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Volume 95-B, Issue SUPP_34 December 2013 International Society for Technology in Arthroplasty (ISTA)

Ali Abdulkarim Anas Elsibaei Bob Jackson Danial Riordan John Rice

Introduction

Proper femoral reaming is a key factor for a successful outcome in cementless hip arthroplasty. Good quality reaming minimizes risks of intra-operative femoral fracture during reaming and prevents poor fitting of the implant which can lead to subsidance of the stem postoperativly. Determining the quality of reaming is largely a subjective skill and dependant on the surgeon's experience with no documented intraoprative method to assess it objectively.

Method

We recorded and analysed the frequencies of sound signals recorded via a bone conduction microphone during reaming of the femoral canal in a series of 28 consecutive patients undergoing uncemented total hip replacement performed by same surgeon. Hammaring sound frequencies and intensity were analysed by mean of computer software. The relationship between the patterns of the recorded reaming sound frequencies compared with surgeon judgment of the reaming quality intraoparativly and post operative x rays. All patients were followed up clinically and radiologically for 2 years after surgery to determine the integrity of the fix and to evaluate the stability of the prosthesis.


Mazen Al-Hajjar Philippa Clarkson Sophie Williams Louise Jennings Jonathan Thompson John Fisher

Introduction

Stripe wear, observed on retrieved ceramic hip replacements, has only been replicated in vitro under translational mal-positioning conditions where the centres of rotation of the head and the cup are mismatched1,2; an in vitro condition termed “microseparation”.

The aim of this study was to compare the edge loading mechanisms observed under microseparation conditions due to translational mal-positioning conditions simulated on two different hip joint simulators.

Materials and Methods

The components used in this study were zirconia-toughened-alumina ceramic-on-ceramic bearings (36 mm) inserted into titanium alloy acetabular cups (BIOLOX® delta and Pinnacle® respectively, DePuy Synthes Joint Reconstruction, Leeds, UK). Six couples were tested for two million cycles under 0.5 mm dynamic microseparation conditions on the Leeds II hip joint simulator as described by Nevelos et al2 and Stewart et al3 (Figure 1). Ten bearing couples were tested for two million cycles under microseparation conditions achieved in two different ways on the ProSim pneumatic hip joint simulator (SimSol, Stockport, UK). Two conditions were tested; condition (1)- the femoral head was left to completely separate (the vertical motion was controlled at 1 mm) causing it to contact the inferior rim of the acetabular cup before edge loading on the superior rim at heel strike (n = 5) and condition (2)- springs were placed below the plate holding the femoral head to control the tilt of the head laterally towards the rim of the acetabular cup as the negative pressure was applied (n = 5; Figure 1). Wear was assessed gravimetrically every million cycles using a microbalance (Mettler AT201, UK). Three-dimensional reconstructions of the wear area on the heads were obtained using a coordinate measuring machine (Legex 322, Mitutoyo, UK) and SR3D software (Tribosol, UK).


Tjarco Alta Joelly M de Toledo Jefferson F Loss Thomas W Janssen Jan Van der Scheer DirkJan (HEJ) Veeger W Jaap Willems

Background:

It is not well known how different external loads influence shoulder kinematics and muscle activity in patients with shoulder prostheses. Study objective: define shoulder kinematics and determine the scapulothoracic contribution to total shoulder motion, in combination with shoulder muscle activity and the degree of co-contraction, of patients with total (TSA) and reverse shoulder arthroplasties (RSA) and healthy individuals during rehabilitation exercises using different loading conditions.

Methods:

Shoulder motions (anteflexion and elevation in the scapular plane) of 17 patients (20 shoulders) with a TSA, 8 patients (9 shoulders) with a RSA and 15 healthy subjects were measured using anelectromagnetic tracking device. A force transducer recorded force signals during loaded conditions (without external load, 1 kg and elastic resistance). Electromyographic (EMG) activity of the deltoid (anterior, middle, posterior parts), latissimus dorsi, pectoralis major (clavicular and sternal parts), teres major and serratus anterior was recorded and the degree of co-contraction calculated.


Thomas Andriacchi

Answering the question of what the patient can teach us about the future of joint replacement starts with a look to the past. The modern era of total joint replacement began in the late 1950's with the pioneering work of John Charnley that established the fundamental structure of a total joint replacement with a metal component bearing against polyethylene and provided many disabled patients with a substantial improvement in function. As the application of joint replacement expanded to a broader patient population it became apparent that a better understanding of the mechanics of patient function was needed to provide more rigorous design criteria and objective assessment of design changes. This presentation will examine how improvements in total knee replacement has been aided by objective measures of ambulatory function and the potential for future improvements in joint replacement that can be based on information from testing patients.

Specifically, from a historical viewpoint one of the major problems limiting the use of total knee replacement in the 1970's was tibial component loosening. The problem of tibial component loosening could be related to the load imbalance between the medial and lateral surface of the tibia. The load asymmetry at the knee resulting from the adduction moment during gait provided a strong rationale for maintaining proper limb alignment following total knee arthroplasty. The analysis clearly showed that knees with a varus alignment of the mechanical axis were more likely to have a substantial load imbalance creating the type of stresses that would eventually lead to tibial component loosening. When the information from gait studies was combined with both clinical and biomechanical studies, tibial component designs were modified using metal backing of the polyethylene articulating surface and instrumentation was modified to allow for proper alignment of the mechanical axis and avoid residual varus deformity following total knee replacement.

Similarly, knee kinematics and moments have been used to differentiate the functional characteristics of different types of designs during stair climbing. Patients with cruciate-sacrificing knee replacements had a tendency to reduce the moment sustained by the quadriceps by leaning forward during the portion of the support phase of ascending stairs when the quadriceps moment would reach a peak value, while patients with a posterior cruciate retaining design were able to sustain normal quadriceps function. The functional differences between the PCL-retaining and sacrificing designs were associated with the normal posterior movement of the femur on the tibia (rollback), with flexion. This finding indicated that TKR design must permit rollback in the early phases of knee flexion to sustain normal stair climbing.

This presentation will conclude with a review of the functional performance of patients with an anterior cruciate deficient knee as a basis for addressing the future needs of a knee replacement to permit natural knee movement. Specifically the role of the anterior cruciate ligament will be discussed in the context of the interaction of the curvature of the articulating surfaces in maintaining a functional envelope of movement that is consistent with retaining both cruciate ligaments.


Charlotte Angel Shaun Sexton Rory MacNair Nicola Fuller

Background:

Higher than expected revision rates have been observed in large bearing metal-on-metal total hip replacements. We have introduced a metal on metal hip screening clinic at our unit and report the results.

Methods:

All patients who had a metal-on-metal total hip replacement implanted at our unit were recalled to clinic. Screening consisted of clinical examination, Oxford hip score, radiographs, MARS MRI and serum cobalt/chromium ion levels. MRI scans were graded (Norwich Classification) by a single consultant radiologist who was blinded to the history, examination, and metal levels. Patients were sub-classified into 6 groups, which determined further follow up and were either entered into a regular screening programme or referred to a revision arthroplasty surgeon for a decision on whether revision was required


Michele Angers Stephane Pelet Jessica Vachon

Background:

Total knee replacement (TKR) is a frequent and effective surgery for knee osteoarthritis. Postoperative pain is under concern and can be relieved by different methods, including femoral nerve block (FNB). The efficacy of FNB on pain relief was associated with the absence of clinical impact when measured with the range of motion (ROM). Recent studies suggest that the quadriceps strength is the best indicator of functional recovery after TKR. The goal of this study is to compare the quadriceps strength recovery after TKR according to the kind of analgesia (patient control analgesia (PCA) with or without FNB) Hypothesis: the FNB delays the QSR at short and mid-term follow-up.

Methods:

Prospective randomized trial with single-blind assessment involving 135 patients admitted for TKR in an academic center. Randomization into one of the three following groups: A) Continuous FNB 48h + PCA B) Single-shot FNB and PCA C) PCA alone. Groups were comparable for demographic and surgical data. The FNB was realised and controlled (electric stimulation) by an expert anesthesiologist before the surgery. Follow-up standardised in all groups with blinded assessors. Quadriceps strength measured with a validated dynamometer at 6 weeks, 6 and 12 months. Secondary outcomes included clinical evaluation (ROM, pain, stability) and functional scores (SF-36 v2, WOMAC). Multivariate analysis (Kruskal-Wallis, Mann-Whitney) for main outcomes and Spearman factor for correlation. Sample size calculated for alpha 5% and study power 80%.


Laurent Angibaud Xeve Silver Scott Gulbransen Bernard Stulberg

Introduction

Clinical outcomes for total knee arthroplasty (TKA) are especially sensitive to lower extremity alignment and implant positioning.1 The use of computer-assisted orthopedic surgery (CAOS) can improve overall TKA accuracy.2 This study assessed the accuracy of an image-free CAOS guidance system (Exactech GPS, Blue-Ortho, Grenoble, FR) used in TKA.

Materials and methods:

A high-resolution 3D scanner (Comet L3D, Steinbichler, Plymouth, MI) was used to scan seven knee models (MITA, Medical Models, Bristol, UK) and collect pre-identified anatomical landmarks (see Figure 1) prior to using the models to simulate knee surgery.

The image-free CAOS guidance system was then used to acquire the same landmarks. After adjusting the position and orientation of the cutting block to match the targets, bone resections were performed, and the knee models were re-scanned. The 3D scans made before and after the cuts were overlaid (see Figure 2) and the resection parameters calculated using the pre-identified anatomical landmark data and advanced software (XOV & XOR, RapidForm, Lakewood, CO and UG NX, Siemens PLM, Plano, TX). Data sets obtained from the 3D scanner were compared with data sets from the guidance system. Given the accuracy of the 3D scanner, its measurements were used as the baseline for assessing CAOS system error.


Jean-Noel Argenson Matthieu Ollivier Sebastien Parratte Xavier Flecher Jean-Manuel Aubaniac

Introduction:

Recent studies have concluded that gender influences hip morphology at the time of surgery as well as dysplastic development of the hip. This may lead to a particular choice of implant including stem design and/or neck modularity. In this study we hypothesized that not only gender but also morphotype and etiology (primary osteoarthritis versus aseptic osteonecrosis) may be a significant factor to predict the anatomy of the hip at the time of total hip arthroplasty (THA).

Methods:

We reviewed 690 patients undergoing THA for primary arthritis (OA) or avascular osteonecrosis (AVN) between April 2000 and June 2005 and stratified each into three groups based on their anatomic constitution: endomorph (EN), ectomorph (ECT), or mesomorph (ME) (determined by the ratio: pelvic width/total leg length measured on full-length X-rays). Two independent observers measured twice four parameters on preoperative CT scan: neck-shaft-angle angle (NSA), femoral offset value (FO), helitorsion (Ht) value and femoral neck anteversion (Av).


Scott Ball Colin Yung Dustyn Severns Eric Chang Christine Chung F. Craig Swenson

Introduction:

To date, there have been few reports of the results of revisions for failed metal-on-metal hip arthroplasties (MoM HA's). These series have included relatively modest numbers, and classification of the severity of adverse local tissue reaction (ALTR) has been under-reported. In this study, early outcomes and complications are analyzed as a function of pre-operative MRI grade and intra-operative ALTR severity to determine their prognostic value.

Methods:

This is a retrospective review of revisions of 121 failed MoM HA's performed between 2008 and 2012. Indications for revision include ALTR (n = 97), loose cup (n = 13), and combined loose cup and ALTR (n = 11). When pre-operative MRI's were available, these were graded according to Anderson's system by 2 radiologists who were blinded to the clinical results. Intra-operative findings were graded for severity according to an ALTR classification. Post-operative complications were recorded. Correlations between pre-operative MRI grade, intra-operative ALTR classification and post-operative complications were analyzed using Spearman's rank correlation.

ALTR Classification:

Type 0: No abnormal fluid or pseudotumor. Peri-articular structures intact.

Type 1: Abnormal fluid and/or pseudotumor. Peri-articular structures disrupted but repairable.

Type 2: Abnormal fluid and/or pseudotumor. Peri-articular structures disrupted and no meaningful repair possible.

Type 3: Abnormal fluid and/or pseudotumor. Peri-articular structrues disrupted, no meaningful repair possible, AND significant necrosis involving abductor muscles.


Marc Bandi Giles Scuderi Eik Siggelkow Iris Sauerberg Francesco Benazzo

Summary:

Smaller increments in the antero-posterior dimensions of femoral components allows significant improvements in balancing of the knee after TKA with restoration of more normal soft-tissue stability.

Introduction:

The soft-tissue stability of the knee after TKA is often compromised by the fact that only a finite set of implantable component sizes is available to match bony anatomy. While this could be overcome with custom components, a more practical solution is a set of femoral components with smaller increments in the antero-posterior (AP) dimension. However, this results in a larger assortment of sizes of both implants and trial components. This study was performed to determine whether smaller increments in the AP sizing of knee prostheses would lead to real benefits in restoration of normal knee function and stability after TKA.


Lowry Barnes Ryan Nunley Cara Petrus

PURPOSE:

Unicompartmental knee arthroplasty (UKA) is becoming more commonly performed and is more technically challenging than total knee replacement. Retention of the anterior and posterior cruciate ligaments requires more accurate re-creation of the patient's normal anatomic posterior slope with UKA. Purpose of this study was to accurately determine the posterior tibial slope in patients having medial or lateral UKA performed.

METHODS:

Retrospective review was performed of 2,395 CT scans performed for a customized UKA implant. Standard CT technique was used and the posterior slope was measured on the involved side of the proximal tibia.


Ayman Bassiony

Background

In young patients with femoral neck non-union it is desirable to preserve the femoral head. The objective of this study was to assess the outcome results of revision internal fixation and nonvascular fibular bone grafting

Patients and Methods:

Ten patients with non united fracture neck femur were included in this prospective study. Fixation was done with two cancellous screws leaving behind a space between two screws for fibular strut graft. Assessment of union was done by both clinical and radiological criteria.


Christopher Bechtel Jeremy Gebhart Joscelyn Tatro Mark Schluchter J. Mark Wilkinson Edward Greenfield

Introduction:

Wear particles cause aseptic loosening by stimulating macrophages to produce inflammatory cytokines. Recent studies indicate that Toll-like receptor 2 (TLR2) and TLR4 mediate macrophage responses to the wear particles [1–3]. TLR2 and TLR4 uniquely activate MyD88-dependent signaling via an additional adapter protein known as TIRAP/Mal [4]. Del Vescovo et al reported that three single nucleotide polymorphisms (SNPs) within the TIRAP/Mal gene associate with aseptic loosening in THA patients [5]. The goal of the current study was therefore to determine whether TIRAP/Mal mediates responses to orthopaedic wear particles.

Methods:

Immortalized wild type (WT) and TIRAP/Mal knockout (KO) murine macrophages (Mfs) were incubated in the presence or absence of titanium (Ti) particles (1 × 108 particles/cm2 [2]. Three types of particles were used as described previously [1,2]: Ti particles with adherent bacterial debris (38.3 Endotoxin Units/109 particles), endotoxin-free Ti particles (<0.1 EU/109 particles), and Ti particles with adherent lipopolysacharide (LPS, 32.8 EU/109 particles). TNFa, IL-1b, and IL-6 mRNAs were measured by real-time PCR and the secreted cytokines were measured by ELISA. Particle-induced osteolysis in calvaria of TIRAP/Mal KO and WT mice was measured 7 days after particle implantation [1,2]. In vitro results are presented as mean ± SEM of 3–4 replicate experiments analyzed by two-way ANOVA with Bonferroni post-hoc corrections. In vivo results are presented as means of individual parietal bones ± SEM (n = 22) and analyzed by one-way ANOVA on ranks with Student Neuman-Keuls post-hoc corrections. * denotes p < 0.5, ** denotes p < 0.01, *** denotes p < 0.


Jeffrey Backes Joel R Politi Bryan Chambers Jared Bentley Matt Clayton

Controlling postoperative pain and nausea after total joint arthroplasty remains an important challenge. We conducted a prospective, randomized controlled trial with 120 patients to determine if the addition of perioperative dexamethasone to a multimodal regimen improves antiemetic and analgesic control, enhances mobility, and shortens hospital length of stay after total hip and knee arthroplasty. Patients administered 10 mg of intravenous dexamethasone intraoperatively consumed less daily rescue anti-emetic and analgesic medication, reported superior VAS nausea and pain scores, ambulated further distances, and had a significantly shorter length of stay compared to the control group (p < 0.05). A second, 24-hour postoperative dose of 10 mg intravenous dexamethasone provided significant additional pain and nausea control and further reduced length of stay (p < 0.05). No adverse events were detected with the administration of the intraoperative and/or postoperative dexamethasone.


Sanaz Berahmani Dennis Janssen David Wolfson Maarten De Waal Malefijt Nico Verdonschot

The effect of an advanced porous surface morphology on the mechanical performance of an uncemented femoral knee prosthesis was investigated. Eighteen implants were inserted and then pushed-off from nine paired femurs (Left legs: advanced surface coating; right legs: Porocoat® surface coating as baseline). Bone mineral density (BMD) and anteroposterior dimension were measured, which both were not significantly different between groups. The insertion force was not significantly different, but push-off force was significantly higher in the advanced surface coating group (P = 0.007). BMD had direct relationship with the insertion force and push-off force (p < 0.001). The effect of surface morphology on implant alignment was very small. We suggest that the surface properties create a higher frictional resistance thereby providing a better inherent stability of implants featuring the advanced surface coating.


Roy Bloebaum Ornusa Chalayon Aaron Adam Hofmann Raymond E. Olsen

Introduction:

With the arrival of the 21st century, there were clear expectations that cementless fixation in total joint replacements (TJR), and the translational animal protocols for introducing new coatings and surface treatments clinically, had been established. Despite the extensive literature in the 1980s and 1990s demonstrating a translational pathway for predicting skeletal attachment, there remain clinical reports of mechanical implant loosening in both cementless total hip acetabular and total knee components. Before screening a new porous coating or surface treatment, it is important to note that there has been only one experimental translational load-bearing model that has had human (1–3), sheep (4–5), clinical (6–8), and implant retrieval verification confirming skeletal attachment in these types of components, the intracondylar model (1–5,8).

What makes the intracondular model predictive of coating or surface treatments for implant attachment is the ability of the model to replicate the healing response of cancellous bone, the main attachment bone tissue to THR acetabular and TKA implants. A lot of the confusion rests with a lack of understanding of the bone response differences between the intracondylar and transcortical animal models.

The goal of this study was to test the hypothesis that the intracondylar model can provide positive and negative surface attachment data, whereas, the transcortical model can only provide positive and false positive attachment data.

Methods:

Five skeletally mature sheep will have been implanted with two 13×8 mm plugs (500 mm larger than the 7.5 mm drilled holes) two plugs transcortically and two intracondylarly. One plug will be titanium with CP porous coating. Another plug is made of petrified dinosaur poop with similar dimensions (see Figure 1). Another five sheep will also be implanted transcortically and intracondylarly using plugs with 500 mm inset of the same materials and dimensions. Again, two implants at each site.


Ben Bolland E Gardner Anne Roques Christian Maul David Culliford Nedal Zeineh Lawrence O'Hara

This study reports the mid-term results of a large bearing uncemented metal on metal total hip replacement (MOMHTHR) matched series using the Synergy stem and Birmingham modular head in 36 hips (mean follow up 61 months). All patients underwent clinical, metal ion and MRI assessment. Wear analysis was performed on retrieved heads using Redlux non-contact optical profilometry.

Seven patients (19%) have undergone revision surgery. All revisions had two or more of either symptoms, high metal ions or an MRI suggestive of an adverse reaction to metal debris (ARMD). There was no evidence of component malposition or impingement. Frank staining of tissues together with high volume dark brown fluid collections were found in all cases. All stems and cups were well fixed. In 4 cases pubic and ischial lysis (adjacent to the inferior fins) was observed. All 7 cases had radiological, intraoperative and histological evidence of ARMD (Figure 1). The failure cohort had significantly higher whole blood cobalt ion levels and OHS (p = 0.001), but no significant difference in cup size (p = 0.77), gender predominance, stem offset or cup position (p = 0.12). Sleeves had been used in all revision cases

Wear analysis (n = 4) demonstrated increased wear at the trunnion/sleeve interface in a distribution compatible with micromotion (Figure 2). There was normal wear at the articulating surface.

This series further demonstrates unacceptable failure rates in LHMOMTHR in a series where a compatible stem for the BHR modular head was used. Use of a CoCr sleeve within a CoCr head taper appears to contribute to abnormal wear and therefore potential ARMD and subsequent failure.


Bert Boonen Bart Kerens Martijn Schotanus Dieter Vangeneugden Nanne Kort

Background:

Patient-specific guiding (PSG) is a relatively new technique for aligning a total knee arthroplasty (TKA). Limited data exist on the precise accuracy of the technique. The purpose of this study is to investigate whether there was significant difference between the alignment of the individual femoral and tibial components (in all three anatomical planes) as calculated pre-operatively and the actually achieved alignment in vivo.

Methods:

Twenty-six patients were included. Software permitted matching of the pre-operative MRI-scan (and therefore calculated prosthesis position) to a pre-operative full-leg CT-scan. After surgery a post-operative full-leg CT-scan could be superimposed onto the pre-operative CT-scan to accurately determine deviations from planning (see figure 1 and 2). This 3D-technique has an accuracy of 0.7–1.0 degrees.


Danilo Bruni Francesco Iacono Francesca Colle Simone Bignozzi Maurilio Marcacci

BACKGROUND:

The optimal reference for rotational positioning of femoral component in total knee replacement (TKR) is debated. Navigation has been suggested for intra-op acquisition of patient's specific kinematics and functional flexion axis (FFA).

QUESTIONS/PURPOSES:

To prospectively investigate whether pre-operative FFA in patients with osteoarthritis (OA) and varus alignment changes after TKR and whether a correlation exists between post-op FFA and pre-op alignment.


Frederick Buechel

Introduction:

UKA allows replacement of a single compartment in patients who have isolated osteoarthritis. However, limited visualization of the surgical site and lack of patient-specific planning provides challenges in ensuring accurate alignment and placement of the prostheses. Robotic technology provides three-dimensional pre-op planning, intra-operative ligament balancing and haptic guidance of bone preparation to mitigate the risks inherent with current manual instrumentation. The aim of this study is to examine the clinical outcomes of a large series of robot-assisted UKA patients.

Methods:

The results of 500 consecutive medial UKAs performed by a single surgeon with the use of a metal backed, cemented prosthesis installed with haptic robotic guidance. The average age of the patients at the time of the index procedure was 71.1 years (range was 40 to 93 years). The average height was 68 inches (range 58″–77″) and the average weight was 192.0 pounds (range 104–339 pounds). There were 309 males and 191 females. The follow-up ranges from 2 weeks to 44 months.


William Bugbee Luke Aram Alex Schenher Michael Swank

Introduction

Optimal alignment of the tibial component in TKA is an important consideration. General agreement exists on the appropriate coronal alignment. However there is no consensus on sagittal alignment (posterior slope). Some surgeons target a fixed posterior slope (usually between 0 and 10 degrees), while others attempt to match the patient's intrinsic anatomy. The purpose of this study was to evaluate the tibial posterior slope in patients undergoing TKA.

Methods

13,586 CT scans of patients undergoing patient specific were analyzed. Three-dimensional reconstructions were performed and the posterior tibial slope was measured. Mean slope and ranges were determined.


Mark Frankle Andres Cabezas Sergio Gutierrez Matthew Teusink Brandon Santoni Daniel Schwartz

Background:

Currently, there are a variety of different reverse shoulder implant designs but few anatomic studies to support the optimal selection of prosthetic size. This study analyzed the glenohumeral relationships of patients who underwent reverse shoulder arthroplasty (RSA).

Methods:

Ninety-two shoulders of patients undergoing primary RSA for a massive rotator cuff tear without bony deformity or deficiency and 10 shoulders of healthy volunteers (controls) were evaluated using three-dimensional CT reconstructions and computer aided design (CAD) software. Anatomic landmarks were used to define scapular and humeral planes in addition to articular centers. After aligning the humeral center of rotation with the glenoid center, multiple glenohumeral relationships were measured and evaluated for linearity and size stratification. The correction required to transform the shoulder from its existing state (CT scan) to a realigned image (CAD model) was compared between the RSA and control groups. Size stratification was verified for statistical significance between groups. Generalized linear modeling was used to investigate if glenoid height, coronal humeral head diameter and gender were predictive of greater tuberosity positions.


Francesco Fiacchi Fabio Catani Vitantonio Digennaro Mauro Gialdini Gianluca Grandi

Orthopaedic surgeons and their patients continue to seek better functional outcomes after total knee replacement, but TKA designs claim characteristic kinematic performance that is rarely assessed in patients.

The objectives of this investigation is to determine the in vivo kinematics in knees with Cruciate Retaining TKA using Patient Specific Technology during activities of daily living and to compare the findings with previous studies of kinematics of other CR TKA designs.

Four knees were operated by Triathlon CR TKA using Patient Specific Technology and a fluoroscopic measurement technique has been used to provide detailed three-dimensional kinematic assessment of knee arthroplasty function during three motor tasks. 3D fluoroscopic analysis was performed at 4-month follow-up.

The range of flexion was 90°(range 5°–95°) during chair-rising, 80°(range 0°–80°) during step up and 100° (range 0°–100°) during leg extension. The corresponding average external rotation of the femur on the tibial base-plate was 7.6° (range +4.3°; +11.9°), 9.5° (+4.0°; 13.5°) and 11.6° (+4.5°; +16.1°). The mean antero-posterior translations between femoral and tibial components during the three motor tasks were +4.7 (−3.7; +1.0), +6.4 (−3.8; +2.6) and +8,4 (−4.9; +3.5) mm on the medial compartment, and −2.5 (−7.1; −9.6), −3.6 (−6.1; −9.7), −2.6 (−7.7; −10.3) mm on the lateral compartment, respectively, with the medial condyle moving progressively anterior with flexion, and the medial condyle moving progressively posterior with flexion.

We compared Triathlon CR PSI TKA results from this study with Genesis II CR TKA, with Duracon CR TKA, with Triathlon CR TKA and with the healthy knee kinematics. The results of this study showed no screw home mechanism. The internal rotation of the tibia with knee flexion is close to normal, better than Genesis II, Duracon and Triathlon CR TKA operated with standard surgery.

The medial condyle is characterized by the same pattern of the other implants, with a paradoxical anterior translation of 5 mm.

The lateral condyle shows a posterior rollback better than Triathlon CR operated with standard surgery.

For the first time is demonstrated that the surgical technique can modify the tibio-femoral kinematics.


Jean-François Cazeneuve

The aim of this retrospective and mono centric study is to expose results and complications of the reverse concept in the elderly in case of trauma. We therefore ask whether clinically the patients recover a pre-broken state, whether the radiological follow-up shows critical images and whether the rate of complications is important.

We reviewed the outcome of forty-two patients operated consecutively by the same surgeon at a mean follow-up of 9.1 years (range, 1–19 years). There were four men and thirty-eight females, mean age 75 (range, 58–92 years), with 28 complex four-part fractures and 14 fracture-dislocations. There was no re-fixation of the tubercles because of a poor bone quality.

Six complications occurred: 2 complex sympathetic dystrophies treated by medication, 2 early dislocations (one superior because of an impingement in adduction between the humeral stem and the remnants of the tubercles solved by their ablation without further problems and one anterior caused by the voluntary 10° ante-version of the humeral component to improve internal rotation leading to the reorientation of the stem), 1 deep infection solved by debridement and drainage for an early postoperative Acinetobacter infection without further problems and one aseptic loosening of the base-plate with a broken screw and no wear at 12-year follow-up leading to implant a classic base-plate because of a fair bone stock and efficient primary grip after impaction.

The mean Constant score dropped from 55 at one year to 52 (20 to 84) at last revision which represented 67% of the mean score for the injured side. Mean adjusted Constant score was 68. Only 58% of the patients were satisfied or very satisfied because of poor rotations avoiding nourishment with utensils, dressing andpersonal hygiene. When the dominant arm was affected, the patients lost frequently their autonomy.

Two patients with 42-mm glenospheres had complete 2-mm radiolucent lines at four- and eight-year follow-up. Inferior spurs were seen in 15 cases (35%). They were stable after emergence without functional impact or radiographic evolution. They appeared at a mean of 2.5 years (range, 1–6 years). Scapular notching was seen in 23 cases (55% of the patients), all appeared before two-year follow-up. Eleven notches were stable with a sclerotic border and without critical humeral images. Twelve were progressive with a proximal humeral bone loss (n = 7) or a radiolucent line (n = 5). In these cases, there was a negative effect on the Constant score: 41 points instead of 57 for notches without critical images.

Our experience reported in the present study has somewhat weakened our enthusiasm for this procedure. 42% of the patients were unsatisfied because of poor rotations and the functional results were never equal to the pre-injury state. 33% of the radiological images found were critical. 14% of the patients had a severe complication. Such results do not allow us to validate in the long-term the concept of RSA in recent trauma of proximal humerus. So nowadays, our elective indication is a woman for a non-dominant arm, over seventy years old with poor physiology and important osteoporosis.


Newton Chan Christoph Fuchs Ricardo Valle Mark Adickes Philip Noble

Introduction:

Femoro-acetabular impingement reduces the range of motion of the hip joint and is thought to contribute to hip osteoarthritis. Surgical treatments attempt to restore hip motion through resection of bone at the head-neck junction. Due to the broad range of morphologies of FAI, the methodology of osteochondroplasty has been difficult to standardize and often results in unexpected outcomes, ranging from minimal improvement in ROM to excessive head resection with loss of cartilage and even neck fracture. In this study we test whether a standardized surgical plan based on a pre-determined resection path can restore normal anatomy and ROM to the CAM-impinging hip.

Methods:

Computer models of twelve femora with classic signs of cam-type FAI were reconstructed from CT scans. The femoral shaft and neck were defined with longitudinal axes and the femoral head by a sphere of best fit. Boundaries defining the maximum extent of anterior resection were constructed: (i) superiorly and inferiorly along the anterior femoral neck at 12:30 and 5:30 on the clock face, approximating the locations of the vascularized synovial folds; (ii) around the head-neck junction along the edge of the articular cartilage; and (iii) at the base of the neck, perpendicular to the neck axis, 20–30 mm lateral to the articular edge. All four boundaries were used to form 3 alternative resection surfaces that provided resection depths of 2 mm (small), 4 mm (medium), and 6 mm (large) at the location of the cam lesion. Solid models of each femur after virtual osteochondroplasty were created by Boolean subtraction of each of the resection surfaces from the original femoral model. For each depth of neck resection, we measured the following: (i) alpha angle, (ii) anterior offset of the head-neck junction, and (iii) volume of bone removed. Before and after each resection, we also measured the maximum internal rotation of the hip in 90° flexion and 0° abduction.


Lauren Karbach Ashley Matthies Sabir Ismaily Jonathan Gold Alister Hart Newton Chan Philip Noble

Introduction:

A disturbing prevalence of painful inflammatory reactions has been reported in metal-on-metal (MoM) hip resurfacing arthroplasty. A contributing factor is localized loading of the acetabular shell leading to “edge wear” which is often seen after precise measurement of the bearing surfaces of retrieved components. Factors contributing to edge wear include adverse cup orientation leading to proximity (<10 mm) of the hip reaction force to the edge of the acetabular component. As this phenomenon is a function of implant positioning and patient posture, this study was performed to investigate the occurrence of edge loading during different functional activities as a function of cup inclination and version.

Methods:

We developed a computer model of the hip joint through reconstruction of CT scans of a proto-typical pelvis and femur and virtually implanting a hip resurfacing prosthesis in an ideal position. Using this model, we examined the relationship between the resultant hip force vector and the edge of the acetabular shell during walking, stair ascent and descent, and getting in and out of a chair. Load data was derived from 5 THR patients implanted with instrumented hip prostheses (Bergmann et al). We calculated the distance from the edge of the shell to the point of intersection of the load vector and the bearing surface for cup orientations ranging from 40 to 70 degrees of inclination, and 0 to 40 degrees of anteversion.


Caecilia Charbonnier Sylvain Chague Matteo Ponzoni Massimiliano Bernardoni Pierre Hoffmeyer Panayiotis Christofilopoulos

Introduction

Conventional pre-operative planning for total hip arthroplasty mostly relies on the patient radiologic anatomy for the positioning and choice of implants. This kind of planning essentially remains a static approach since dynamic aspects such as the joint kinematics are not taken into account. Hence, clinicians are not able to fully consider the evolving behavior of the prosthetic joint that may lead to implant failures. In fact, kinematics plays an important role since some movement may create conflicts within the prosthetic joint and even provoke dislocations. The goal of our study was to assess the relationship between acetabular implant positioning variations and resultant impingements and loss of joint congruence during daily activities. In order to obtain accurate hip joint kinematics for simulation, we performed an in-vivo study using optical motion capture and magnetic resonance imaging (MRI).

Methods

Motion capture and MRI was carried out on 4 healthy volunteers (mean age, 28 years). Motion from the subjects was acquired during routine (stand-to-sit, lie down) and specific activities (lace the shoes while seated, pick an object on the floor while seated or standing) known to be prone to implant dislocation and impingement. The hip joint kinematics was computed from the recorded markers trajectories using a validated optimized fitting algorithm (accuracy: translational error ≍ 0.5 mm, rotational error < 3°) which accounted for skin motion artifactsand patient-specific anatomical constraints (e.g. bone geometry reconstructed from MRI, hip joint center) (Fig. 1).

3D models of prosthetic hip joints (pelvis, proximal femur, cup, stem, head) were developed based on variations of acetabular cup's inclination (40°, 45°, 60°) and anteversion (0°, 15°, 30°) parameters, resulting in a total of 9 different implant configurations. Femoral anteversion remained fixed and determined as “neutral” with the stem being parallel to the posterior cortex of the femoral neck. Motion capture data of daily tasks were applied to all implant configurations.

While visualizing the prosthetic models in motion, a collision detection algorithm was used to locate abnormal contacts between both bony and prosthetic components (Fig. 2). Moreover, femoral head translations (subluxation) were computed to evaluate the joint congruence.


Miriam Chaudhary Peter Walker

Tibial component loosening is an important failure mode in unicompartmental knee arthroplasty (UKA) which may be due to the 6–8 mm of bone resection required or the limited surface area. To address component loosening and fixation, a new Early Intervention (EI) design is proposed which reverses the traditional material scheme between femoral and tibial components. That is, the EI design consists of a plastic inlay component for the distal femur and a thin metal plate for the proximal tibia. With this reversed materials scheme, the EI design requires minimal tibial bone resection compared to traditional UKA to preserve the dense and stiff bone in the proximal tibia. This study investigated, by means of finite element (FE) simulations, the potential advantages of a thin metal tibial component compared with traditional UKA tibial components, such as an all-plastic inlay or a metal-backed onlay. We hypothesized that an EI component would produce comparable stress, strain, and strain energy density characteristics to an intact knee and more favorable values than UKA components. Indeed, the finite element results showed that an EI design reduced stresses, strains and strain energy density in the underlying support bone compared to an all-plastic UKA component. Analyzed parameters were similar for an EI and a metal-backed onlay, but the EI component had the advantage of minimal resection of the stiffest bone.


Caecilia Charbonnier Panayiotis Christofilopoulos Sylvain Chague Jerome Schmid Placido Bartolone Pierre Hoffmeyer

Introduction

Today, there is no clear consensus as to the amplitude of movement of the “normal hip”. Knowing the necessary joint mobility for everyday life is important to understand different pathologies and to better plan their treatments. Moreover, determining the hip range of motion (ROM) is one of the key points of its clinical examination. Unfortunately this process may lack precision because of movement of other joints around the pelvis. Our goal was to perform a preliminary study based on the coupling of MRI and optical motion capture to define precisely the necessary hip joint mobility for everyday tasks and to assess the accuracy of the hip ROM clinical exam.

Methods

MRI was carried out on 4 healthy volunteers (mean age, 28 years). A morphological analysis was performed to assess any bony abnormalities. Two motion capture sessions were conducted: one aimed at recording routine activities (stand-to-sit, lie down, lace the shoes while seated, pick an object on the floor while seated or standing) known to be painful or prone to implant failures. During the second session, a hip clinical exam was performed successively by 2 orthopedists (2 and 12 years' experience), while the motion of the subjects was simultaneously recorded (Fig.1). These sequences were captured: 1) supine: maximal flexion, maximal IR/ER with hip flexed 90°, maximal abduction; 2) seated: maximal IR/ER with hip and knee flexed 90°. A hand held goniometer was used by clinicians to measure hip angles in those different positions.

Hip joint kinematics was computed from the markers trajectories using a validated optimized fitting algorithm which accounted for skin motion artifacts (accuracy: translational error≍0.5 mm, rotational error <3°). The resulting computed motions were applied to patient-specific hip joint 3D models reconstructed from their MRI data (Fig. 2). Hip angles were determined at each point of the motion thanks to two bone coordinate systems (pelvis and femur). The orthopedist's results were compared.


Thomas Halim Michelle Burgett Ian Clarke Thomas Donaldson

The MOM controversy continues with many prevailing opinions as to the causes of failure in contemporary designs. There has been a great deal of focus on breakdown in fluid-film lubrication with respect to cup positioning and edge wear at its rim. However there has been very little discussion on the problems of 3rd body abrasion. In only one study was there a description of unusually large abrasive marks on retrieved femoral heads (McKee Farrar MOM), revealing 100 μm wide scratches, attributed to circulating particles fractured during impingement episodes. With contemporary MOM devices, there is the potential for abrasion by particulates of CoCr, PMMA and Ti6Al4V. However it has been difficult to formulate a coherent simulator model for 3rd-body abrasive wear, given the unpredictable nature of impingement damage releasing abrasive particles into the patient's hip joint. Thus this study sought to identify if metal or cement particulates were capable of creating 100 μm wide scratches as seen on retrieved MOM and develop a simulator model for 3rd body abrasive testing on MOM bearings.

Six 38 mm CoCrMo bearings (DJO Inc., Texas) were run in a12-station hip simulator (SWM, Monrovia, CA) with cups mounted both anatomically and inverted (3 MOM each). The tests were run in standard simulator mode (Paul gait load cycle: 0.2–2 kN, frequency 1 Hz) with the addition of 5 mg of debris particles. Commercially available CoCr (ASTM F75) and titanium alloy (ASTM F136) particles and broken polymerized bone cement particles were used in the size range 50–200 μm. The simulator was run for only 10 cycles and the MOM parts removed for study. All bearings were ultrasonically cleaned and heads were examined using white light interferometry (WLI, Zygo Corp). Grooves were characterized using surface profiles to measure width, depth, and rim height. SEM imaging (EVO MA15, Zeiss) and EDS imaging (X flash detector 4010, Bruker AXS) was performed in areas of grooving and suspected transfer layers.

CoCr debris produced broad, curvilinear grooves with widths ranging from 20–170 μm, depths from 0.3–1.5 μm, raised rims, longitudinal striations and chatter marks. Titanium alloy debris produced arrays of very shallow scratches accompanying larger grooves. These larger grooves measured 20–110 μm wide and 0.4–1.9 μm deep.

EDS imaging showed the smears and islands contained the elements Ti, Al and V representative of the Ti6Al4V alloy. WLI imaging showed these metal deposits (250–900 um wide) were raised >10 um above the surface. Particularly conspicuous was evidence of considerable smearing on CoCr surfaces, with linear streaks ranging 150–300 μm wide. Bone cement debris proved incapable of grooving the CoCr surface, the only scratches observed were those comparable to normal carbide scratches.


Chadd Clary Daren Deffenbaugh Filip Leszko Patrick Courtis

Introduction:

Adequate coverage of the resected tibial plateau with the tibial tray is necessary to reduce the theoretical risk of tibial subsidence after primary total knee arthroplasty (TKA). Maximizing tibial coverage is balanced against avoiding excessive overhang of the tray causing soft tissue irritation, and establishing proper tray alignment improving implant longevity and patella function1. Implant design factors, including the number of tray sizes, tray shape, and tray asymmetry influence the ability to cover the tibial plateau2. Furthermore, rotating platform (RP) tray designs decouple restoring proper tibial rotation from maximizing tibial coverage, which may enhance the ability to maximize coverage. The purpose of the current study was to assess the ability of five modern tray designs (Fig. 1), including symmetric, asymmetric, fixed-bearing, and RP designs, to maximize coverage of the tibial plateau across a large patient population.

Methods:

Lower limb computed-tomography scans were collected from 14,791 TKA patients and the tibia was segmented. Virtual surgery was performed with an 8-mm tibial resection (referencing the high side) made perpendicular to the tibial mechanical axis in the frontal plane, with 3° posterior slope, and aligned transversely to the medial third of the tibial tubercle. An automated algorithm placed the largest possible tray on the plateau, optimizing the ML and AP placement (and I-E rotation for the RP tray), to minimize overhang. The largest sized tray that fit the plateau with less than 2-mm of tray overhang was identified for each of the five implant systems. The surface area of the tibial tray was divided by the area of the resected plateau and the percentage of patients with greater than 85% plateau coverage was calculated.


Justin Cobb Adeel Aqil Victoria Manning Sarah K Muirhead-Allwood

INTRODUCTION

A recent PRCT failed to demonstrate superiority of HRA over THA at low speeds. Having seen HRA walk much faster, we wondered if faster walking speed might reveal larger differences.

We therefore asked two simple questions:

Does fast or uphill walking have an effect on the observed difference in gait between limbs implanted with one HRA and one THA?

If there is a difference in gait between HRA and THA implanted legs, which is more normal?

METHODS

Participants All patients who had one HR and one THR on the contralateral side were identified from the surgical logs of two expert surgeons. Both surgeons used a posterior approach to the hip and repaired the external rotators on closure. All consenting patients were assessed using the Oxford Hip Score (OHS) to ensure they had good functioning hips.

There were 3 females and 6 males in the study group, who had a mean age of 67 (55–76) vs the control group 64 (53–82, p = 0.52). The BMIs of the two groups did not differ significantly (28 v 25, p = 0.11).

The mean average oxford score of included patients was 44 (36–48). Radiographs of all subjects were examined to ensure that implanted components were well fixed.

The mean time from THA operation to gait assessment was 4 years (1–17 yrs) and that for HRA was 6 years (0.7–10 yrs, p = 0.31). Subjects in this study had a mean TWS of 6.8 km/hr (5–9.5), and a mean TWI of 19 degrees (10–25 degrees).


Justin Cobb Barry Andrews Victoria Manning Michela Zannotto Simon Harris

Outcome measures are an essential element of our industry: comparing a novel procedure against an established one requires a reliable set of metrics that are comprehensible to both the technologist and the layman.

We surmised that a detailed assessment of function before and after knee arthroplasty, combined with a detailed set of personal goals would enable us to test the hypothesis that less invasive joint and ligament preserving operations could be demonstrated to be more successful, and cost effective. We asked the simple question: how well can people walk following arthroplasty, and can we measure this?

Materials and methods

Using a treadmill, instrumented with force plates, we developed a regime of walking at increasing speeds and on varying inclines, both up and down hill. The data from the force plates was then extracted directly, without using the proprietary software that filtered it. Code was written in matlab script to ensure that missed steps were not mistakenly attributed to the wrong leg, automatically downloading of all the gait data at all speeds and inclines.

The pattern of gait of both legs could then be compared over a range of activities.

Results

Wide variation is seen in gait both before and after arthroplasty. The variables that are easiest to explain are these:

width of gait – this appears to be a pre-morbid variable, not easily correctible with surgery. (figure 1)

top walking speed – total knee replacement is associated with 11% lower top speeds than uni knees or normals (p < 0.05)

change in stride length with increasing speed: normal people increase their walking speed by increasing both their cadence and their stride length incrementally until a top stride length is reached. Patients with a total knee replacement do not increase their stride length at a normal rate, having to rely on increasing cadence to deliver speed increase. Patients with uni or bi-compartmental knee replacements increase speed like normal people.

Downhill gait: as many as 40% of fit patients with ‘well functioning’ total knee replacements choose not to walk downhill at all, while all fit patients with ‘well functioning’ partial replacements are able to do this. Those who can manage, can only manage 90% of the normal speed, unlike unis which are indistinguishable from normal (p < 0.05)


Conor Lowry Alison Traynor Simon Collins

Introduction

Total Knee Replacement (TKR) is a highly effective treatment providing pain relief and improved function to patients experiencing advanced stage osteoarthritis. Tray fit or bone coverage is a critical design feature for both cemented and cementless designs affecting stability, load transfer and potential for infection. Many authors have attempted to characterise the relationship between the profile of the proximal tibia and gender and ethnicity1–3. As a consequence, a number of manufacturers have commercialised devices designed for specific gender and racial demographics. This study was initiated to compare the effect of the fixed minimum tibial resection depth prescribed by existing surgical instruments with that of a proportionate resection based on the size of the tibia.

Method

A dataset consisting of 30 donor scans from a US cadaver tissue bank (ScienceCare, Memphis, US) was used for this study. The dataset consisted of 12 male and 18 female specimens. Due to the limited view of the diaphysis for most scans, the natural slope of the lateral compartment was used as a guide for orienting the resection. All scans were resected with a 3° posterior slope. For the first part of this study, an equal mediolateral (ML) resection of 9.5 mm, reflecting the minimum resection for the Unity TKR tibia (Corin, UK), was performed on all specimens (Figure 1). Following this, two proportionate resection depths (13.5 mm and 6.7 mm) were calculated based on the ML relationship between the smallest and largest available Unity components (59.5 mm: 84.5 mm). Two further resection depths (11.3 mm and 8.0 mm) were calculated based on a mid size (71.0 mm). Three resection depths (8.0 mm, 9.5 mm & 11.3 mm) were applied to four medium sized specimens. In addition to this two larger specimens were resected at 9.5 mm and 13.5 mm and two smaller specimens at 6.7 mm and 9.5 mm.

A grid was applied to all cut surfaces and oriented using the posterior axis. The cut surface was divided based on lines drawn at 10%, 25%, 50%, 75% and 90% of the overall ML dimension and 10%, 25%, 50%, 75% and 90% of the overall anteroposterior (AP) dimension. Measurements were taken from the medial side and recorded from the points at which lines intersected the external profile of the cut tibia (Figure 2).


Michael Conditt Richard Illgen

While THA is regarded as one of the most successful surgeries in medicine, recent studies have revealed that ideal acetabular cup implantation is achieved as little as 50% of the time. Malalignment of the acetabular component in THA may result in dislocation, reduced range of motion, or accelerated wear. Recently, robotic-assisted surgery has been introduced to reduce the errors in component placement. The purpose of this study is to longitudinally assess the accuracy of cup placement of a single surgeon at three points in time: directly following a total joint fellowship, after 10 years of experience with manual instrumentation, and directly after adopting robotic technology.

Three hundred patients received THA at a single center by a single surgeon representing three series of 100 consecutive patients in each series. The first series A included the surgeon's first 100 THA patients following graduation from joint fellowship (2/2000–5/2002). The second series B included the surgeon's last 100 THA patients before adopting robotic technology (12/2010–1/2012) and the final series C included the surgeon's first 100 THA patients using robotic assistance (4/2012–4/2013). The post-operative abduction and version of the cup was measured using PACS imaging software from the AP and cross-table lateral radiographs. Abduction was measured using a transverse line at the level of the teardrop and the lateral opening angle of the cup relative to this reference line. Anteversion was measured using the ischial method described by Schmalzreid on the crosstable lateral view and accounts for pelvic flexion.

The average inclination for the groups A, B, and C was 48.6 ± 7.6°, 37.4 ± 6.2°, and 39.6 ± 47.6°, respectively and for anteversion was 29.3 ± 10.3°, 26.6 ± 8.4°, and 23.6 ± 5.7°, respectively. The cup placement in the original series A was within the Lewinnek safe zone only 31% of the time. This increased to 45% in series B and up to 74% in series C (p < 0.05). With the robotic series C, the three-dimensional pre-operative plan was obtained from the software. The average error (final placement–plan) was −0.7 ± 2.1° for inclination and 1.1 ± 2.0° for version. 93% of the inclination measurements and 94% of the version measurements were within 5° of the plan and 100% of both measurements were within 10° of the plan. Of note, 8% of the robotic cases were actually planned outside of the Lewinnek safe zone to accommodate for patient deformity and optimize correction to achieve the targeted combined anteversion of the acetabular and femoral components.

Robotic assistance in THA leads to significantly more precise acetabular cup placement. As measured by the Lewinnek safe zone, 10 years of experience resulted in a 45% increase in precision, while adding robotic assistance resulted in a 139% increase in precision compared to the surgeon's initial performance. With greater knowledge of ideal acetabular cup position, highly accurate techniques may allow surgeons to decrease the risk of dislocation, promote durability and improve the ability to restore appropriate leg length and offset.


Richard Cook Natalie Shearwood-Porter Corina Nicolae Benjamin Bolland Jeremy Latham Robert Wood

Introduction:

Cemented femoral components have been used in hip replacement surgery since its inception. For many patients this works well, but recent retrieval studies1–4 and more fundamental studies5, 6 have highlighted the issues of damage and material loss from the both matt and polished cemented stems.

Materials and methods:

This study will focus on a cohort of retrievals from the Southampton Orthopaedics Centre for Arthroplasty Retrieval Surgery (SOCARS). The cohort consisted of a number of hybrid modular total hip replacements with cemented femoral components, both from mixed and matched manufacturer stem and head combinations. Femoral stems were polished, collarless, tapered designs; head sizes ranged from 28–54 mm. For each femoral stem, samples of Palacos R + G cement (Heraeus Medical GmbH, Hanau, Germany) were retrieved from the proximal region of the cement mantle (Gruen zones 1 and 7), corresponding to both macroscopically damaged and undamaged surfaces of the stem. The areas of damage were determined using calibrated digital photography; damaged surfaces were then imaged in detail using an Alicona InfiniteFocus microscope (Alicona Imaging GmbH, Graz, Austria). The technique uses optical microscopy and focus variation technology to extract 3D morphology and depth information from the surface with a resolution of 10 nm. A series of measurements were made and two different analysis routes were used to provide volumetric material loss measurements from the stem surface. High-resolution microscopy and elemental analysis of the cement and stem surfaces was conducted via SEM and EDX to identify the mechanisms leading to material loss at the cement-stem interface.


Craig Silverton Joshua J Jacobs Jeffrey Devitt John Cooper

Background

There are numerous concerns associated with femoral stems that feature a modular neck design, including the potential for corrosion, modular neck fracture, and adverse local tissue reactions. These stems have a higher-than-anticipated rate of failure in registry results, but large single-center cohort studies are lacking.

Methods

This is a retrospective, single-surgeon cohort of 133 hips in 119 patients implanted with a single dual-tapered titanium alloy stem with a modular titanium alloy neck (Profemur® Z; Wright Medical Technology, Arlington, TN). Several bearing surface combinations were used, including metal-on-polyethylene, ceramic-on-polyethylene, metal-on-metal, and ceramic-on-ceramic couples. Patients were evaluated at a mean of 4.5 years (range 2.0–9.0 years) with Harris Hip scores (HHS), radiographic analysis, and metal ion testing.


Luca Cristofolini

Pre-clinical validation of implantable devices, including prostheses, generally aims at demonstrating that a new device offers some advantage compared to existing ones, while not introducing additional hazards. This process involves the assessment of a number of possible failure scenarios and claimed benefits, in order to obtain certification of the device (e.g. FDA or CE-mark), and to support its marketing strategy.

While until the 90ies in vitro tests were regarded as the golden standard, nowadays the trend is to rely more and more on numerical models (chiefly Finite Element models, FE). The truth is that neither numerical models nor in vitro tests are self-sufficient. FE models require the support of in vitro tests for a number of reasons. First of all, to construct reliable FE models a number of input parameters are required (e.g. material properties, friction coefficients) that can only be measured experimentally. Furthermore, FE models, like any model, can only address the scenarios they are intended for, and cannot predict something that is totally unexpected: for this reason, some preliminary indication is mandatory from in vitro tests. Finally, FE models cannot be assumed true until this is proven by validation against in vitro measurements. At the same time, in vitroexperiments have several limitations that make them unsuitable in a number of cases, for which FE models are better suited. First of all, experiments need optimization, which can be performed efficiently using FE models. Secondly, experiments typically inspect the outer surface of the in vitro specimen. Finally, in vitro experiments are ineffective in exploring multiple similar conditions (sensitivity analysis).

A possible paradigm for pre-clinical validation can be summarized as follows (Fig. 1):

Preliminary in vitro experiments should be performed on implants with a prototype of the prosthesis to understand which failure scenarios should be expected.

Potential hazards must be identified. For each hazard, the probability of occurrence and the risk must be identified using either a top-down Fault Tree Analysis (FTA), or a bottom-up Failure Mode and Effect Analysis (FMEA).

To assess the risk of occurrence of each mode of failure, the most appropriate approach must be chosen (either experimental, or numerical). For instance, in vitro experiments are necessary to:

Preliminarily assess the intended implant performance, and explore possible failure modes.

Measure the actual material properties and interface conditions.

Perform tests on specimens that include a real bone, the typical uncertainty related to implantation (interface condition, press-fit), etc.

Conversely, numerical models are advantageous to:

Estimate biomechanical quantities (e.g. state of stress/strain) in regions that are not accessible experimentally.

Explore the effect of design factors (material, surface finish, geometric features, etc), surgical factors (e.g. implant malpositioning) on the outcome.

Predict the post-operative evolution of the implant over time, including progressive failure, tissue adaptation, etc.

Therefore, in vitro experiments and numerical models should be designed concurrently, to enable maximal synergy. The aim of this paper is to illustrate a framework where numerical models and in vitro tests synergistically complement each other (Fig. 2).


Jerry D'Alessio Donald Eckhoff Mark Kester

Computational modeling has been used to simulate the natural and prosthetic kinematic and kinetic function in an attempt to compare designs and/or predict a desired motion path from a design. The levels of soft tissue can range from basic ligaments (MCL, LCL, and ACL & PCL) to more complex models. The goal of this study was to evaluate the sensitivity of the Posterior Cruciate ligament in a virtual model and its effects on the kinematic outcome in a commercially available and validated kinematics package (KneeSim, LifeModeler San Clemente, CA).

Methods:

KneeSIM is a musculoskeletal modeling environment that is built on the foundation of the ADAMS (MSC Software, Santa Ana CA), a rigid body dynamics solver to compute knee kinematics and forces during a deep knee bend. All parameters are customizable and can be altered by the user. Generic three dimensional models of cruciate retaining components of the femoral, tibial, and patellar are available with the software and were used to provide a common reference for the study. The following parameters were modified for each simulation to evaluate the sensitivity of the PCL in the model: 1) Model without PCL, 2) PCL with default properties, 3) PCL Shifted at femoral origin, 7 mm anterior, 7 mm inferior; tibial origin maintained; 4) PCL with increased stiffness properties (2x default), 5) position in the femur and tibia remained default position and 6) PCL with default properties and location, joint line shifted 4 mm superior. The standard output of tracking the flexion facet center (FFC) motion of the medial and lateral condyles was utilized (Figure 1).

Results:

Figure 2 and 3 displays the output of the six conditions tested above. Comparing the curves for the medial and lateral motion show different patterns with the lateral point having more posterior translation than the medial. After approximately 95° of flexion, all cases exhibit an anterior translation in the model. This motion was consistent for all test cases. The model showed no difference with motion either with or without the PCL and with changing the stiffness. Altering the location of the PCL on the femoral insertion had the greatest effect on motion, while shifting the joint line superior was second. The shift of the ligament insertion and changing of the joint line results in the ligament being more parallel to the tibial surface which provides resistance to anterior motion or posterior translation.


Darryl D'Lima Adam Bunn Shantanu Patil Clifford Colwell

Introduction:

Kinematic studies are used to evaluate function and efficacy of various implant designs. Given the large variation between subjects, matched pairs are ideal when comparing competing designs. It is logical to deduce that both limbs in a subject will behave identically during a given motion [1], barring unilateral underlying pathology, thus allowing for the most direct comparison of two designs. It is our goal to determine if this is a valid assumption by assessing whether or not there are significant differences present in the kinematics of left and right knees from the same subject. Gait studies have compared pre-and postoperative implantation kinematics for various pathologies like ACL rupture [2] and osteoarthritis [3, 4]. We designed a study to assess squatting in cadaver specimens.

Methods:

Sixteen matched pairs of fresh-frozen cadavers, (Eleven males, five females; aged 71 years [± 10 yrs]) were tested. Each knee, intact, was tested by mounting it on a dynamic, quadriceps-driven, closed-kinetic-chain Oxford knee rig (OKR), which simulated a deep knee bend from full extension to 120° flexion. We chose femoral rollback, tibiofemoral external rotation, tibial adduction, patellofemoral tilt and shift as our outcomes, which were recorded using an active infrared tracking system.


Darryl D'Lima Shantanu Patil Adam Bunn William Bugbee Clifford Colwell

Introduction:

Despite over 95% long-term survivorship of TKA, 14–39% of patients express dissatisfaction due to anterior knee pain, mid-flexion instability, reduction in range of flexion, and incomplete return of function. Changing demographics with higher expectations are leading to renewed interest in patient-specific designs with the goal of restoring of normal kinematics.

Improved imaging and image-processing technology coupled with rapid prototyping allow manufacturing of patient-specific cutting guides with individualized femoral and tibial components with articulating surfaces that maximize bony coverage and more closely approximate the natural anatomy. We hypothesized that restoring the articular surface and maintaining medial and lateral condylar offset of the implanted knee to that of the joint before implantation would restore normal knee kinematics. To test this hypothesis we recorded kinematics of patient-specific prostheses implanted using patient-specific cutting guides.

Methods:

Preoperative CT scans were obtained from nine matched pairs of human cadaveric knees. One of each pair was randomly assigned to one of two groups: one group implanted with a standard off-the-shelf posterior cruciate-retaining design using standard cutting guides based on intramedullary alignment; the contralateral knee implanted with patient-specific implants using patient-specific cutting guides, both manufactured from the preoperative CT scans. Each knee was tested preoperatively as an intact, normal knee, by mounting the knee on a dynamic, quadriceps-driven, closed-kinetic-chain Oxford knee rig (OKR), simulating a deep knee bend from 0° to 120° flexion. Following implantation with either the standard or patient-specific implant, knees were mounted on the OKR and retested. Femoral rollback, tibiofemoral rotation, tibial adduction, patellofemoral tilt and shift were recorded using an active infrared tracking system.


Yifei Dai Jeffery Bischoff

Introduction

Tibial components that match the resected proximal tibia may promote accurate rotational alignment and maximize coverage while minimizing overhang in total knee arthroplasty (TKA). Tibial component designs have traditionally been evaluated utilizing an overall anterior-posterior (AP)/medial-lateral (ML) ratio. However, since the tibial plateau is irregularly shaped, such a metric has drawbacks. Here, a detailed set of morphological metrics is used to evaluate six contemporary tibia designs against a multi-ethnic bone database.

Methods

Tibial surfaces from 347 subjects, including 97 Indian (50m/47f), 99 Japanese (44m/55f), and 151 Caucasian (85m/66f), were virtually resected following a specific TKA procedure, as previous publications have shown surgical variability minimally impacts tibial resection morphology. Medial and lateral AP dimensions (MAP and LAP), ML width (ML), and medial and lateral anterior radii (MAR and LAR) were measured in a coordinate system constructed on the resected surface based on the neutral rotational axis (Fig. 1A). These metrics, along with anterior radius asymmetry (MAR/LAR), were regressed against ML for each ethnicity. The regressions were then compared with similar measurements obtained from tibial components in six contemporary TKA systems (one asymmetric: Design A; four symmetric: Designs B-E; and one anatomic: Design F).


Ajit Deshmukh Michael J. Moses Nimrod Snir Alan J. Dayan Scott Marwin

Introduction:

Non-hinged constrained condylar components (CCK) may be used for primary TKA in presence of severe deformity, fixed contractures and ligamentous laxity. Several authors have recommended use of stem extensions to accompany CCK type of components. However, use of stem extensions in primary TKA, not only invades the medullary canal, but may also be associated with increased surgical time, implant cost, and thigh or leg pain. The purpose of this study was to assess the short-term outcomes of primary CCK knees without stem extensions and to compare this to a control group of standard posterior stabilized (PS) knees, otherwise using the same implant design.

Materials and Methods:

We retrospectively reviewed the clinical and radiographic data on 503 consecutive TKA's performed by 2 arthroplasty surgeons at the same institution between 2008–2010. Surgical technique, implant type, bone-cement and cementation technique was similar. The only difference between groups was the use of CCK polyethylene insert in one group and a PS insert in the other. Knee society scores (KSS) were used to determine pain, function and ROM. Radiographic evaluation was done using the knee society's criteria to determine implant fixation. Failure was defined as revision for any reason. Statistical analyses were performed using SPSS software.


Jeffrey DeClaire Karthik Vishwanathan Karthik Ramaseshan Meridith Wood Shaunnah Anderson

Background:

A large percentage of the patients who present for unilateral TKA have bilateral disease. Performing simultaneous, bilateral TKA has been debated and currently there is no consensus on the risks and benefit of this approach. In addition, specific selection criteria have not been defined to more accurately identify which patients are potentially appropriate candidates for this approach.

Objectives:

The purpose of this study was to evaluate the clinical outcomes and peri-operative complications in simultaneous, bilateral TKA's using pre-operative patient selection criteria.


Carl Deirmengian Keith Kardos Patrick Kilmartin Alexander Cameron Debra Chung Robert Booth Jay Parvizi

INTRODUCTION:

The diagnosis of periprosthetic joint infection (PJI) remains a serious challenge. Based on previous work, we believe that biomarkers will become the mainstay of diagnosing PJI in the future. We report on completion of our 8 year comprehensive biomarker program, evaluating the diagnostic profile of the 15 most promising synovial fluid biomarkers.

METHODS:

Synovial fluid was prospectively collected from 99 patients being evaluated for infection in the setting of revision hip or knee arthroplasty. All synovial fluid samples were tested by immunoassay for 15 putative biomarkers that were developed and optimized specifically for use in synovial fluid. Sensitivity, specificity and receiver operating Characteristic (ROC) curve analysis were performed for all biomarkers.


Hendrik Delport Luc Labey Ronny De Corte Bernardo Innocenti Jos Vander Sloten Johan Bellemans

Passive knee stability is provided by the soft tissue envelope which resists abnormal motion. There is a consensus amongst orthopedic surgeons that a good outcome in TKA requires equal tension in the medial and the lateral compartment of the knee joint, as well as equal tension in the flexion and extension gap. The purpose of this study was to quantify the ligament laxity in the normal non-arthritic knee before and after standard posterior-stabilized total knee arthroplasty (PS-TKA). We hypothesized that the medial collateral ligament (MCL) and the lateral collateral ligament (LCL) will show minimal changes in length when measured directly by extensometers in the native human knee during varus/valgus laxity testing. We also hypothesized that due to differences in material properties and surface geometry, native laxity is difficult to be completely reconstructed using contemporary types of PS-TKA.

Methods:

A total of 6 specimens were used to perform this in vitro cadaver test using extensometers to provide numerical values for laxity and varus-valgus tilting in the frontal plane. See Fig. 1 The test set-up.

Findings:

This study enabled a very precise measurement of varus and valgus laxity as compared with the clinical assessment which is a subjective measure. The strains in both ligaments in the replaced knee were different from those in the native knee. Both ligaments were stretched in extension, in flexion the MCL tends to relax and the LCL remains tight. Fig. 2 Initial and maximal strain values in the MCL during valgus and varus laxity testing in different flexion angles. a: intact knee, b: replaced knee. and Fig. 3 Initial and maximal strain values in the LCL during valgus and varus laxity testing indifferent flexion angles. a: intact knee, b: replaced knee.


Ajit Deshmukh Saurabh Khakharia Giles Scuderi W Norman Scott

Introduction

The purpose of this study was to determine the efficacy of a multi-modal blood conservation protocol that involved pre–operative autologous blood donations (2 units) in conjunction with erythropoietin supplementation as well as intra-operative conservation modalities.

Methods

A retrospective chart review of 90 patients with simultaneous bilateral total knee arthroplasty done between 2006–2009 by one of the 3 senior authors was performed. Patients donated two units of blood 4 weeks prior to surgery and also received erythropoietin injections (40,000 units: 3 weeks, 2 weeks and 1 week prior to surgery). Intra- operative blood management included use of pneumatic tourniquet, re-infusion drains, local epinephrine injections and fibrin spray. Post-operatively, autologous transfusions were provided based on symptoms. Pre-donation blood levels, peri-operative hemoglobin and hematocrit levels along with transfusion records were assessed.


Rainer Detsch Tobias Fey Peter Greil Qiang Chen Aldo R. Boccaccini

Biomaterials used in regenerative medicine should be able to support and promote the growth and repair of natural tissues. Bioactive glasses (BGs) have a great potential for applications in bone tissue engineering [1, 2]. As it is well known BGs can bond to host bone and stimulate bone cells toward osteogenesis. Silicate BGs, e.g. 45S5 Bioglass® (composition in wt.%: 45 SiO2, 6 P2O5, 24, 5 Na2O and 24.5 CaO), exhibit positive characteristics for bone engineering applications considering that reactions on the material surface induce the release of critical concentrations of soluble Si, Ca, P and Na ions, which can lead to the up regulation of different genes in osteoblastic cells, which in turn promote rapid bone formation. BGs are also increasingly investigated for their angiogenic properties.

This presentation is focused on cell behavior of osteoblast-like cells and osteoclast-like cells on BGs with varying sample geometry (including dense discs for material evaluation and coatings of highly porous Al2O3-scaffolds as an example of load-bearing implants). To obtain mechanically competent porous samples with trabecular architecture analogous to those of cancellous bone, in this study Al2O3 scaffolds were fabricated by the well-known foam replication method and coated with Bioglass® by dip coating.

The resulted geometry and porosity were proven by SEM and μCT. Originating from peripheral blood mononuclear cells formed multinucleated giant cells, i.e. osteoclast-like cells, after 3 weeks of stimulation with RANKL and M-CSF. Thus, the bioactive glass surface can be considered a promising material for bone healing, providing a surface for bone remodeling. Osteoblast-like cells and bone marrow stromal cells were seeded on dense bioactive glass substrates and coatings showing an initial inhibited cell attachment but later a strong osteogenic differentiation. Additionally, cell attachment and differentiation studies were carried out by staining cytoskeleton and measuring specific alkaline phosphatase activity. In this context, 45S5 bioactive glass surfaces can be considered a highly promising material for bone tissue regeneration, providing very fast kinetics for bone-like hydroxyapatite formation (mineralization). Our examinations revealed good results in vitro for cell seeding efficacy, cell attachment, viability, proliferation and cell penetration onto dense and porous Bioglass®-coated scaffolds.

Recent in vivo investigations [3] have revealed also the angiogenic potential of bioactive glass both in particulate form and as 3D scaffolds confirming the high potential of BGs for bone regeneration strategies at different scales. Implant surfaces based on bioactive glasses offer new opportunities to develop these advanced biomaterials for the next generation of implantable devices and tissue scaffolds with desired tissue-implant interaction.


Benjamin Domb Youssef El Bitar Jennifer C Stone Timothy Jackson Dror Lindner Christine Stake

Background:

Total hip arthroplasty (THA) has been proven to be successful in achieving adequate pain relief and favorable outcomes in patients suffering from hip osteoarthritis (OA). However, leg length discrepancy (LLD) is still a significant cause of morbidities such as nerve damage, low back pain and abnormal gait. Despite most of the reported values of LLD in the literature being within the acceptable threshold of < 10 mm, some patients still report dissatisfaction, leading to litigation against orthopedic surgeons. However, lower extremity lengthening is sometimes necessary to achieve adequate hip joint stability and prevent dislocations. The purpose of this study was to compare LLD in patients undergoing THA using three different techniques: conventional anterior-approach THA (ATHA), conventional posterior-approach THA (PTHA), and robotic-assisted posterior-approach THA (RTHA) using the MAKO™ robotic hip system.

Materials and Methods:

All cases of RTHA, ATHA and PTHA that were performed by the senior surgeon between Sep 2008 and Dec 2012 were reviewed. Patients included in this study had a primary diagnosis of hip osteoarthritis, with available and proper post-operative antero-posterior pelvis radiographs. All radiographs were calibrated and measurements done twice by two blinded observers.


Nick Dong Christopher Heffernan Jim Nevelos Michael Ries

Introduction:

Acetabular revision Jumbo cups are used in revision hip surgeries to allow for large bone to implant contact and stability. However, jumbo cups may also result in hip center elevation and instability. They may also protrude through anterior wall leading to ilopsoas tendinitis.

Methods:

The study was conducted using two methods:

Computer simulation study

265 pelvic CT scans consisting of 158 males and 107 females were converted to virtual 3-dimensional bones. The average native acetabular diameter was 52.0 mm, SD = 4.0 mm (males in 52.4 mm, SD = 2.8 mm and 46.4 mm, SD = 2.6 mm in females). Images were analyzed by custom CT analytical software (SOMA™ V.3.2)1 and over-sized reaming was simulated. Four distinct points, located in and around the acetabular margins, were used to determine the reamer sphere. Points 1, 2, 3 were located at the inferior and inferior-medial acetabular margins, and Point 4 was located superiorly and posteriorly in the acetabulum to simulate a bony defect in this location, Point 4 was placed at 10%, 20%, 30%, 40%, 50% and 60% of the distance from the superior – posterior margin of the acetabular rim to the sciatic notch to simulate bony defects of increasing size. (Figure 1)

Radiographical study

Retrospective chart review of patient records for all cementless acetabular revisions utilizing jumbo cups between January 1, 1998 and March 30, 2012 at UCFS (98 patients with 57 men, 41 women). Jumbo cups: ≥66 mm in males; <62 mm in females. Reaming was directed inferiorly to the level of the obturator foramen to place the inferior edge of the jumbo cup at the inferior acetabulum. To determine the vertical position of the hip center, a circle was first made around both the jumbo and the contralateral acetabular surfaces using Phillips iSite PACS software. The center of this circle was assumed to correspond to the “hip center”. The height of the hip center was estimated by measuring the height of a perpendicular line arising from the interteardrop line (TL) and ending at the hip center


Jan Dujardin Hilde Vandenneucker Johan Bellemans Jan Victor

A prospective randomized trial on 128 patients with end-stage osteoarthritis was conducted to assess the accuracy of patient-specific guides. In cohort A (n = 64), patient- specific guides from four different manufacturers (Subgroup A1 Signature ®, A2 Trumatch ®, A3 Visionaire ® and A4 PSI ®) were used to guide the bone cuts. Surgical navigation was used as an intraoperative control for outliers. In cohort B (n = 64), conventional instrumentation was used. All patients of cohorts A and B underwent a postoperative full-leg standing X-ray and CT scan for measuring overall coronal alignment of the limb and three-planar alignment of the femoral and the tibial component. Three-planar alignment was the primary endpoint. Deviation of more than three degrees from the target in any plane, as measured with surgical navigation or radiologic imaging, was defined as an outlier.

In 14 patients (22%) of cohort A, the use of the patient-specific guide was abandoned because of outliers in more than one plane. In 18 patients (28%), a correction of the position indicated by the guide, was made in at least one plane. A change in cranial-caudal position was most common. Cohort A and B showed a similar percentage of outliers in long-leg coronal alignment (24.6%, 28.1%, p = 0.69), femoral coronal alignment (6.6%, 14.1%, p = 0.24) and femoral axial alignment (23%, 17.2%, p = 0.50). Cohort A had more outliers in coronal tibial alignment (14.6%) and sagittal tibial alignment (21.3%) than cohort B (3.1%, p = 0.03 and 3.1%, p = 0.002, respectively). These data indicate that patient specific guides do not improve accuracy in total knee arthroplasty.


Neil Duplantier David Briski J. Lockwood Ochsner Mark S. Meyer Daryl Stanga George Chimento

Background:

Complications following hip and knee arthroplasty can occur in any given patient. However, specific risk factors such as increased age, history of coexistent disease, and increased body mass index have been found to increase the risk of complications after such procedures. Complications often require prolonged hospital admission periods and added hospital resources which ultimately results in increased costs per hospital stay. However, if patients are pre-operatively risk stratified, and followed post-operatively for specific high risk medical issues, many complications may be avoided. By using a hospital standardised peri-operative risk stratification process, the cost per hospital stay for hip and knee arthroplasty may decrease.

Hypothesis:

Overall hospital costs related to joint arthroplasty will be decreased by using a multi-disciplinary peri-operative risk stratification programme.


Christian Fabry Christoph Woernle Rainer Bader

Introduction:

The higher resisting torque against dislocation and the large range of motion due to the enlarged effective head diameter substantiate the use of eccentric dual-mobility cups in case of total hip joint instability [1,2]. As a result of force-dependent self-centering mechanism, an increased movement of the intermediate-component can be expected whose effect on wear propagation is unknown so far. Currently available hip joint simulators are only able to vary the load by the absolute value and not by the direction of resulting force. Therefore, the uniaxial force transmission may lead to a unique and stable alignment of the intermediate-component during testing. The purpose of this numerical study was to evaluate relative movements of the intermediate-component during daily life activities with respect to wear propagation.

Method:

The numerical analysis was based on a standard dual-mobility system consisting of a polished metallic cup, a UHMWPE intermediate-component (40 mm outer diameter) with an eccentric offset of 2 mm and a 28 mm ceramic femoral head [Fig. 1]. The relative motion of the intermediate-component was affected by the geometrically generated self-centering torque (TC) and the friction torque for inner (TFi) and outer (TFo) articulation around the centre of rotation Z1[Fig. 2]. In order to consider lubrication conditions the lambda ratio was estimated for different daily life activities [3], including the calculation of composite roughness and minimum film thickness for a ball-on-plate configuration. The friction torque was related to the product of load (FRes), lever arm and the coefficients of friction which were determined using the equation proposed by [4]. Depending on load FRes and load orientation angle βthe equilibrium of moments around Z1 was established.


Caleb Szubski Mario Farias-Kovac Mark Hebeish Alison Klika Kirtishri Mishra Wael Barsoum

Introduction:

The prevalence of total hip (THA) and knee arthroplasty (TKA) is growing dramatically, with more than 1 million procedures performed annually in the United States. As the cost of and demand for the newest orthopaedic implants continue to rise, the price paid to medical device companies for implants is a growing concern. Some high-volume healthcare institutions have adopted price capitation strategies to control costs, in which a flat purchase price is negotiated for all implant line items regardless of technology and material. The purpose of this study was to evaluate whether the implementation of price capitation in a large health system affected trends in THA and TKA premium implant selection by surgeons. A secondary objective was to compare selection trends between surgeons with an academic center affiliation and community practice surgeons, within a single health system.

Methods:

All consecutive primary THA and TKA cases six months before (1/1/2011–6/30/2011) and after (8/1/2011–1/31/2012) implementation of a capitated pricing strategy (7/1/2011) were identified. Surgeon education regarding the new pricing policy was conducted for 1-month following implementation, and data during this time were omitted from the study. After exclusions (Figure 1), a total of 481 THA and 674 TKA from the large hospital, and 253 THA and 315 TKA from the two community hospitals comprised the final study cohort. A retrospective review of patient demographics and implant characteristics for each case was performed. Premium THA implants were defined by the existence of one of the following bearing surfaces: second (2G) or third generation (3G) highly cross-linked polyethylene liner with a ceramic or oxidized-zirconium femoral head, ceramic liner with a ceramic femoral head, or mobile-bearing system. Premium TKA implants were defined by the existence of at least one of the following criterion: mobile-bearing design, high-flexion design, oxidized-zirconium femoral component, and/or highly cross-linked polyethylene bearing surface. Pearson's chi-square analyses and Fisher's exact test were used to compare implant usage between pre- and post-capitated pricing time periods.


Full Access
Joseph Fetto Peter Walker

Published investigations with custom short stems have reported very encouraging results (Walker, et al, 1). However, off-the-shelf (OTS) versions of shorter length prostheses has not met with the same success.

Several basic questions must be addressed. First, what is the purpose of a stem? Second, can stem length be reduced and if so by how much can this be safely done. Third, what are the effects of stem shortening and are there other design criteria which must take on greater importance in the absence of a stem to protect against implant aseptic failure.

To examine these issues a testing rig was constructed which attempts to simulate the in vivo loading situation of a hip, Fig. 1 (Walker, et, al.). Fresh cadaveric femora were tested with the femora intact and then with femoral components of varying stem length implanted to examine the distribution of stresses within the femur under increasing loads as a function of stem length. This was correlated with observations of prospective DEXA measurement of proximal femoral bone mass and implant migration following THR (Leali, 3). We then initiated a prospective multi-center study of a specific short stem design which included three geometric features to ensure initial implant stability. This report documents that after 2 years, in the first 200 stems implanted, this design has been shown to provide stability against subsidence, flexion/extetnsion and rotational forces. This is consistent with the findings of the in-vitro studies and identical to the previously published clinical results of a similarly designed full length version of this same stem.

Our studies indicated that a stem is not an absolute requirement in order to achieve a well functioning, stable implant. Initial stability can be achieved in the absence of a stem, by a “rest fit,” if adequate design features are incorporated. These studies also demonstrated that simply reducing the length of an existing implant to accommodate changes in surgical techniques may not be a reasonable or safe design change. Such shortened versions of existing stem designs must undergo rigorously in-vitro testing and clinical validation before being released for implantation.


Clare K. Fitzpatrick Richard D. Komitek Paul J. Rullkoetter

Introduction:

There is substantial range in kinematics and joint loading in the total knee arthroplasty (TKA) patient population. Prospective TKA designs should be evaluated across the spectrum of loading conditions observed in vivo. Recent research has implanted telemetric tibial trays into TKA patients and measured loads at the tibiofemoral (TF) joint [1]. However, the number of patients for which telemetric data is available is limited and restricts the variability in loading conditions to a small subset of those which may be encountered in vivo. However, there is a substantial amount of fluoroscopic data available from numerous TKA patients and component designs [2]. The purpose of this study was to develop computational simulations which incorporate population-based variability in loading conditions derived from in vivo fluoroscopy, for eventual use in computational as well as experimental activity models.

Methods:

Fluoroscopic kinematic data was obtained during squat for several patients with fixed bearing and rotating platform (RP) components. Anterior-posterior (A-P) and internal-external (I-E) motions of the TF joint were extracted from full extension to maximum flexion. Joint compressive loading was estimated using an inverse-dynamics approach. Previously-developed computational models of the knee, lower limb, and Kansas knee simulator were virtually implanted with the same design as the fluoroscopy patients. A control system was integrated with the computational models such that external loading at the hip and ankle were determined in order to reproduce the measured in vivo motions and compressive load (Fig. 1). Accuracy of the model in matching the in vivo motions was assessed, in addition to the resulting joint A-P and I-E loading.

The external loading determined for a broader range of patients can subsequently be utilized in a force-controlled simulation to assess the robustness of implant concepts to patient loading variability. The applicability of this work as a comparative tool was illustrated by assessing the kinematics of two PS RP designs under three patient-specific loading conditions.


Clare K. Fitzpatrick Pleun Hemelaar Mark Taylor

Introduction:

Primary stability is crucial for long-term fixation of cementless tibial trays. Micromotion less than 50 μm is associated with stable bone ingrowth and greater than 150 μm causes the formation of fibrous tissue around the implant [1, 2]. Finite element (FE) analysis of complete activities of daily living (ADL's) have been used to assess primary stability, but these are computationally expensive. There is an increasing need to account for both patient and surgical variability when assessing the performance of total joint replacement. As a consequence, an implant should be evaluated over a spectrum of load cases. An alternative approach to running multiple FE models, is to perform a series of analyses and train a surrogate model which can then be used to predict micromotion in a fraction of the time. Surrogate models have been used to predict single metrics, such as peak micromotion. The aim of this work is to train a surrogate model capable of predicting micromotion over the entire bone-implant interface.

Methods:

A FE model of an implanted proximal tibia was analysed [3] (Fig. 1). A statistical model of knee kinetics, incorporating subject-specific variability in all 6-DOF joint loads [4], was used to randomly generate loading profiles for 50 gait cycles. A Latin Hypercube (LH) sampling method was applied to sample 6-DOF loads of the new population throughout the gait cycle. Kinetic data was sampled at 10, 50 and 100 instances and FE predictions of micromotion were calculated and used to train a surrogate model capable of describing micromotion over the entire bone-implant interface. The surrogate model was tested for an unseen gait cycle and the resulting micromotions were compared with FE predictions.


Markus Flohr Kim Haeussler Roman Preuss Robert Streicher

INTRODUCTION

Modular metal-on-metal hip implants show increased revision rates due to fretting and corrosion at the interface. High frictional torque potentially causes such effects at the head-taper interface, especially for large hip bearings. The aim of this study was to investigate fretting and corrosion of sleeved ceramic heads for large ceramic-on-ceramic (CoC) bearings.

METHODS

The investigated system consists of a ceramic head (ISO 6474-2; BIOLOX® Option), a metal sleeve (Ti-6Al-4V, ISO 5832-3) and different metal stem tapers (Ti-6Al-4V, ISO 5832-3; stainless steel, ISO 5832-1; CoCrMo, ISO 5832-12). Three different test methods were used to assess corrosion behaviour and connection strength of head-sleeve-taper interfaces:

Fretting corrosion acc. to ASTM F1- Corrosion under in-vivo relevant loads

Frictional torque under severe i like conditions

Standardized fretting corrosion tests were carried out. Additionally, a long term test (0.5 mio. cycles) under same conditions was performed.

Corrosion effects under 4.5 kN (stair climbing) and 10 kN (stumbling) were determined for three groups. One group was fatigue tested applying 4.5 mio. cycles at 4.5 kN and 0.5 mio. cycles at 10 kN in a corrosive fluid. In parallel two control groups (heads only assembled at same load levels) were stored in the same fluid for same time period. Pull-off tests were performed to detect the effect of corrosion on the interface strength.

A new designed test was performed to analyse the connection strength and fretting-corrosion effects on the head-sleeve taper interfaces caused by frictional torque of large CoC bearings (48 mm). Two separate loading conditions were investigated in a hip joint simulator. One created bending torque (pure abduction/adduction), the other set-up applied rotational torque (pure flexion). A static axial force of 3 kN and movements with a frequency of 1 Hz up to 5 mio. cycles in the same corrosive fluid as in the second set of tests were applied for both tests. Surface analysis of the taper and sleeve surfaces was peformed. In order to detect loosening caused by frictional torque, torque-out tests were conducted after simulator testing.


Daniel Schwartz Benjamin Cottrell Matthew Teusink Rachel Clark Katheryne Downes Mark Frankle

Introduction:

Reverse shoulder arthroplasty (RSA) has proven to be a useful tool to manage a variety of pathologic conditions. However, inconsistent improvement in motion occurs in patients who have undergone RSA for revision shoulder arthroplasty, proximal humeral fracture sequelae, and treatment of infection. Additional factors that have been suggested to produce poor postoperative range of motion (ROM) may be associated with patient's factors such as poor preoperative range of motion and surgical factors such as inability to lengthen the arm. The purpose of this study was to analyze multiple factors which may be responsible in predicting motion after RSA. It is our hypothesis that intraoperative ROM is most predictive of postoperative ROM.

Methods:

Between February 2003 and April 2011 566 patients (225 male and 341 female) treated with a RSA for 1) acute proximal humeral fracture (11), 2) Sequeala of proximal humeral fractures (31), 3) cuff tear arthropathy (278), 4) massive cuff tear without arthritis (78), 5) failed shoulder arthroplasty (168) and 6) infection (29) were evaluated with preoperative range of motion, intraoperative range of motion and range of motion at a minimum of 2-year postoperative follow up. A single observer recorded intraoperative flexion (IFF) in 30° increments. Preoperative and postoperative ROM was recorded by patient video or a previously validated patient performed outcome measure. Preoperative diagnosis was confirmed by radiographic and intraoperative information. 477 patients had preoperative and postoperative radiographs available for analysis of acromial-greater tuberosity distance change (AGT) which was utilized to calculate arm lengthening. A regression analysis was then performed to determine which factors were most influential in predicting postoperative active range of motion.


Nicholas Frisch Michael Charters Nolan Wessell Jakub Sikora-Klak Christopher Dobson Stephen Yu Craig Silverton Michael Laker Clifford Les

Purpose:

Starting February 2012, our institution changed from enoxaparin (Lovenox) to the Factor Xa inhibitor, rivaroxaban (Xarelto) for venous thromboembolism prophylaxis after primary total hip (THA) and total knee arthroplasty (TKA). The purpose of our study was to compare rates of venous thromboembolism and rates of major bleeding between these two medications when used for venous thromboembolism prophylaxis after primary THA and TKA.

Methods:

A retrospective review was performed on 1795 patients who underwent THA or TKA at our institution between January 1, 2011 and December 31, 2012. Patients were excluded if they had a bilateral procedure, partial arthroplasty (hip hemiarthroplasty, unicompartmental knee arthroplasty), revision surgery, and cases designated as complex. Patients were excluded if they were on other anticoagulants (dabigatran, aspirin, clopidogrel, warfarin, heparin, fondaparinux), or if pre-operative creatinine was 1.2 or greater. After excluding these patients, there were 1089 patients included in the study. Chart review recorded demographics (age, gender), comorbidities (BMI, ASA, creatinine), surgery performed (primary THA or TKA), length of stay (LOS), venous thromboembolic events (deep venous thrombosis [DVT], pulmonary embolus [PE]), post-operative infections, and major bleeding events (stroke, post-operative bleeding requiring transfusion). Periprosthetic infection rates are also currently being reviewed. T-tests were used to compare continuous variables between treatment groups, and Chi-square tests were used to compare categorical variables between treatment groups (α = 0.05).


Ahmed Al Mandhari Alexandros Kyriakos Omid Alizadehkhaiyat Simon Frostick

Objective:

Evaluation of the early results of the implementation of reverse shoulder arthroplasty prosthesis “Comprehensive Reverse” in primary and revision shoulder arthroplasties.

Material and Methods:

September 2010–December 2012, 48 patients (32 women, 16 men) underwent reverse shoulder arthroplasty using Comprehensive Reverse system. Average age of 69.88. A total of 46 patients were followed. In 22 patients the operation was performed for revision. Patients were pre-and postoperatively evaluated using Oxford, Constant, SF-12 scores, radiographs, pain and range of motion. Mean follow-up 13 months.


Bo Gao Laurent Angibaud

Introduction

Total knee arthroplasty (TKA) prostheses are semi-constrained artificial joints. A well-functioning TKA prosthesis should be designed with a good balance between stability and mobility, meaning the femorotibial constraint of the artificial joint should be appropriate for the device's function. To assess the constraint behavior of a TKA prosthesis, physical testing is typically required, and an industrial testing standard has been developed for this purpose [1]. Computer simulation has become increasingly useful in many industries, including medical device research and development where finite element analysis (FEA) has been extensively used in stress analysis and structural evaluation. This study presents an FEA-based simulation to evaluate the femorotibial constraint behavior of TKA prosthesis, and demonstrated the effectiveness of the method by validating through physical testing.

Methods

A Cruciate Retaining (CR) TKA prosthesis design (Optetrak Logic CR, Exactech, USA) was used in this study. CAD models of the implants assembled at 0° of flexion were used for the simulation. Finite element models were generated using with all materials assumed linear elastic. Boundary conditions were set up according to the ASTM F1223 standard (Figure 1). The tibial baseplate was fixed distally. A constant compressive force (710 N) was applied on the femoral component. Nonlinear Surface-Surface-Contact was defined at the femorotibial articulating surfaces. Coefficient of friction was determined from physical test. The femoral component was driven under a displacement-controlled scheme to slide along the anterior-posterior (AP) direction on the tibial insert. At each time step, constraint force occurring at the articulating surface was derived from the reaction force at the distal fixation of the tibial baseplate. A nonlinear FEA solver (NX Nastran SOL601, Siemens, USA) was used to solve the simulation. In addition, five samples of the prostheses were physically tested, and the results were compared with the simulation.


Jeffrey Geller David Patrick Barthelemy Liabaud Brett Rebal William Macaulay

Introduction:

Unicompartmental knee arthroplasty (UKA) has been proven to be an effective treatment for degenerative joint disease confined to a single tibiofemoral compartment. Recently, UKAs have been performed with robotic-arm assistance (RAA) devices to build and improve upon previous computer-assisted navigation. As a pilot study, we have analyzed short term outcomes for a series of robotic-arm assisted medial UKAs and compared them to a comparable cohort of traditionally instrumented medial UKAs.

Methods:

Ninety-eight fixed-bearing medial UKAs were isolated in our prospective data collection database for short-term analysis for this study. Included patients completed pre and post-operative Short Form 12 version 1 Health Survey (SF12), Western Ontario and McMaster University Outcome Scores (WOMAC), and Knee Society Function Score (KSFS) questionnaires. Forty-eight RAA UKAs were performed using the MAKO RIO system with Restoris implants, and fifty manual UKAs were performed with the Zimmer® Unicompartmental High-Flex Knee System (ZUK).


Manish Noticewala Kevin Cassidy William Macaulay Jonathan Lee Jeffrey Geller

Introduction:

Total hip arthroplasty (THA) is extremely effective in treating debilitating arthritic conditions of the hip. With the many modular prosthetic designs available, surgeons can now precisely construct mechanical parameters such as femoral offset (FO). Although several studies have investigated relationships between offset choice and hip abductor strength, hip range of motion, and prosthetic wear rate, there is scarce data on the effect of FO on pain and functional outcomes following THA. The objective of this study was to assess the effect of restoring FO (within varying degrees compared to the contralateral non-diseased hip [CL]) on physical function, mental well-being, pain, and stiffness outcomes as measured by the Short Form 12 Health Survey (SF-12) and Western Ontario and McMaster University Osteoarthritis Index (WOMAC) at post-operative follow-up.

Methods:

We prospectively collected data on 249 patients that underwent unilateral THA with no or minimal disease of the contralateral hip. Baseline data collection included: age, gender, diagnosis, femoral head size, type of stem, and pre-operative SF-12 and WOMAC scores. Post-operative SF-12 and WOMAC scores were recorded during annual follow-up visits. Post-operative FO was retrospectively measured on standard anteroposterior (AP) pelvis radiographs and compared to FO of CL. FO was measured as the perpendicular distance from the femoral head center of rotation to the anatomic axis of the femur with appropriate adjustments made for image magnification. Patients were categorized into one of three groups: decreased femoral offset (dFO, less than −5 mm compared to CL), normal femoral offset (nFO, between −5 and +5 mm of CL), and increased femoral offset (iFO, greater than +5 mm compared to CL).


Justin Gerges Viktor Erik Krebs Kirby Hitt Anthony Hedley Rebecca Wenokor Mohamed Singer

Introduction:

For 30 years, uncemented anatomic hip stems have been implanted with documented clinical results[1,2]. Their geometry can be linked back to the geometry of the PCA and ABG stems. Modifications to date include stem length, body geometry, material, and reduction in distal geometry. New tools have been developed allowing anatomical measurements and analysis of three-dimensional digital femora geometry through CT scans[3]. The purpose of this study is to analyze three-dimensional contact of various anatomic hip stem designs using this technique.

Methods:

Six femora (57–87 yrs, 72–88 kg), were selected from a CT scan database (SOMA™) of 604 Caucasian bones. They were selected based on femoral anteversion (average +/−1.5 * std. dev.) with three measuring[4] 8–10° and three 31–33° of anteversion. The CT scans were segmented into cancellous/cortical bone and converted into CAD models in PRO/Engineer Wildfire (v.5). A/P views of the bones were scaled to a 120% magnification to allow three surgeons to surgically template and choose the stem size and location (maximizing fill (n = 1); restoring the head center (n = 2)) with two implant designs (1-Citation TMZF and 2-ABG II Monolithic, Stryker Orthopaedics, Mahwah). Measurements from templating were used to virtually implant CAD models of the implants into the bones (n = 36 bone/stem assemblies). The assemblies were imported into Geomagic Qualify 2012 for 3D deviation analysis comparing the coated region of the implant to the cortical-cancellous boundary. The analysis generated color map profiles based on the following categories: Contact (−2.0 to 0.5 mm), Conformity (0.5 to 2.0 mm), Proximity (2.0 to 5.0 mm), and Gap (5.0 to 12 mm) and the percent of the surface that was within each of these categories. These results were compared for patterns within and across the anatomic families.


Brian Gladnick Denis Nam Saker Khamaisy Sophia Paul Andrew Pearle

Introduction:

Two fixed bearing options exist for tibial resurfacing when performing unicompartmental knee arthroplasty (UKA). Inlay components are polyethylene-only implants inserted into a carved pocket on the tibial surface, relying upon the subchondral bone to support the implant. Onlay components have a metal base plate and are placed on top of a flat tibial cut, supported by a rim of cortical bone. To our knowledge, there is no published report that compares the clinical outcomes of these two implants using a robotically controlled surgical technique. We performed a retrospective review of a single surgeon's experience with Inlay versus Onlay components, using a robotic-guided protocol.

Methods:

All surgeries were performed using the same planning software and robotic guidance for execution of the surgical plan (Mako Surgical, Fort Lauderdale, FL). The senior surgeon's prospective database was reviewed to identify patients with 1) medial-sided UKA and 2) at least two years of clinical follow up. Eighty-six patients met these inclusion/exclusion criteria: 41 Inlays and 45 Onlays. Five patients underwent a secondary or revision procedure during the follow up period and were considered separately. Our primary outcome was the WOMAC score, subcategorized by the Pain, Stiffness, and Function sub-scores. The secondary outcome was need for secondary surgery. Continuous variables were analyzed using the two-tailed Student's t-test; categorical variables were analyzed using Fisher's exact test.


Nitin Goyal Anay Patel Mark Yaffe Micheal Luo S. David Stulberg

Introduction:

Patient specific instrumentation (PSI) generates customized guides from a magnetic resonance imaging based preoperative plan for use in total knee arthroplasty (TKA). PSI software must be able to accommodate differences in implant design. The purpose of the present study was to determine whether any differences in the accuracy of limb alignment, component alignment, component sizing, or bony resection could be identified in patients undergoing PSI TKA with identical PSI software and one of two different implant systems.

Methods:

In this case-control study, two different implant systems from the same manufacturer were evaluated in 37 consecutive PSI TKA (Group 1) and 123 consecutive PSI TKA (Group 2) performed by a single surgeon. A third group (Group 3) consisted of 12 consecutive TKA performed with manual instrumentation and the same implant system as Group 1. Identical software was used to generate a preoperative plan from which planned limb alignment, component alignment, component sizes, and bony resection were determined. Intraoperatively, actual component sizes, bony resection, and recut frequency were determined. Long-standing and lateral radiographs were obtained preoperatively and 4-weeks postoperatively to evaluate limb and component alignment.


Chancellor Gray Chia Wu Keith Baldwin Gwo-Chin Lee

Introduction

Infection following total knee arthroplasty (TKA) is a catastrophic complication. In the United States, for chronic, first time infected TKA, the gold standard remains a 2-stage reimplantation (2SR) procedure, with reported success rates approaching 90%. However, there is a lack of consensus on the treatment of subsequent reinfections.

Question

The purpose of this study was to use published data on infected TKA to develop a decision tree analysis to determine the treatment method likely to yield the highest quality of life for a patient following a failed 2SR.


Fei Liu Thomas P Gross

Background:

Metal-on-metal total hip arthroplasty (THA) implants have been widely debated due to the adverse wear issue related to the bearing surfacing. However, more recent studies have shown that the high metal ion problems that occur after surgery with this type of implant may not be exclusively related to the all metal bearing surfaces, but mainly due to the recently modified connecting tapers. Biomet is one of few companies who have not changed their original taper design for their THA implants. The purpose of this study was to present our up to eight-year clinical results.

Method:

Between November 2004 and April 2011, all of the 196 cases in 167 patients (77 male vs. 89 female) performed by a single surgeon were included in this study. The Biomet Magnum/Jumbo metal-on-metal total hip arthroplasty implants were utilized for all of the cases. The average age was 59 ± 11 years at the time of surgery. Thirteen patients deceased from causes unrelated to THA. The primary diagnosis was OA in 124 cases; followed by AVN in 41 cases, dysplasia in 12 cases and other causes in the remaining 19 cases. The average acetabular component sizes were 54 ± 4 mm. Clinical and radiographic examinations were performed prospectively, and the results were analyzed.


Kenneth A Gustke Gregory Golladay

Introduction

Proper soft-tissue balance is important for achieving favorable clinical outcomes following TKA, as ligament imbalance can lead to pain, stiffness or instability, accelerated polyethylene wear, and premature failure of implants. Until recently, soft-tissue balancing was accomplished by subjective surgeon feel and by use of static spacer blocks. Now, nanonsensor-embedded implant trials allow surgeons to quantify peak load and center of load in the medial and lateral compartments during the procedure, and to adjust ligament tension and implant positioning accordingly. The purpose of this 3-year, multicenter study is to evaluate 500 patients who have received primary TKA with the use of intraoperative sensors in order to correlate quantified ligament balance to clinical outcomes.

Methods

To date, 7 centers have contributed 215 patients who have undergone primary TKA with the use of intraoperative sensors. Patients are seen at a pre-operative visit (within 3 months prior to surgery), and post-operatively at 6 weeks, 6 months, and at 1, 2, and 3-year anniversaries. Standard demographic and surgical data is collected for each patient, including: age at time of surgery, BMI, operative side, gender, race, and primary diagnosis. At each interval, anatomic alignment and range of motion are assessed; KSS and WOMAC evaluations are administered; and a set of standard radiographs is collected, including: standing anteroposterior, standing-lateral, and the sunrise patellar view. Intraoperative loads were recorded for pre- and post-release joint states. All soft-tissue release techniques were recorded. “Optimal” soft-tissue balance was defined as a medial-lateral load difference of less than or equal to 15 lbs.


Hani Haider

Current projections point to a large increase in the number of arthroplasty surgeries over the next 20 years. Implant manufacturers typically offer each hospital multiple sets of instruments dedicated to one of their implant system models. Each set includes over 100 mechanical alignment and other instruments (jigs), typically housed in multiple trays. These instruments increase engineering and production costs to the manufacturer, the training burden for surgeons, and increase costs for the hospital for sterilization, training and other logistics. Patient specific instruments addresses some of this burden but involve scaleability, potential liability and speed challenges in that some of the custom jigs design and all its manufacture is delayed and removed from the surgeon, and cannot be changed during surgery.

This talk is about a revolutionary freehand navigated bone cutting technology for joint replacement surgery without implant specific mechanical jigs, without expensive and cumbersome robots, and optionally also even without external navigation tracker equipment. It facilitates navigated freehand bone cutting with real-time 3D graphical feedback. It transforms the traditional orthopaedic power instruments (eg. sagittal saws, drills) into “smart instruments” which can track themselves in 3D around the surgical scene, and optionally prevent the surgeon from deviating from the planned cuts. In bench experiments, this cutting-edge technology promises faster, cheaper, easier and more accurate bone cuts. It assists the surgeon naturally with miniaturized electronics and intelligence on-board the same powered bone cutting instruments they are highly used to.

Joint replacement surgery is highly successful currently, but this technology is intended to make it easier, faster, cheaper and better. A solution that increases benefits to the patient and surgeon alike, while reducing infection risks and costs, may transform patient care in an overburdened field which is expected to grow in the coming years.


Amgad Haleem Sabir Ismaily Morteza Meftah Philip Noble Stephen Incavo

Introduction:

Dual mobility total hip arthroplasty (DM-THA) allows for very large femoral head size, which may be beneficial for hip range of motion (ROM). No clinical study has objectively compared ROM in patients with DM-THA and large (36-mm head) total hip arthroplasty (36-THA). The aim of this prospective case-control study is to test the hypotheses that DM-THA provides superior hip ROM compared to 36-THA by dynamic radiography, and that surgical approach (posterolateral [PL] versus modified anterolateral [AL]) has effect on post-operative hip ROM.

Materials and Methods:

Sixteen patients (11 males, 5 females) who had undergone DM-THA with a minimum follow up of one year were age, sex and body mass index (BMI) matched to twenty patients (12 males, 8 females) with 36-THA, all operated upon by the senior author. Maximum hip-trunk flexion, extension and total hip-trunk ROM was calculated on standing lateral digital radiographs of the lower lumbar spine, pelvis and hip, using commercially available software (TraumaCad®, BrainLab, Munich, Germany) from three upright positions; standing neutral, standing with maximum hip flexion and standing with maximum hip extension. Contributions to motion from lumbo-sacral spine (LSS) and pelvic tilt were calculated and subtracted from hip-trunk measurements to quantify true hip flexion, extension and total true hip ROM. Statistical analysis (SPSS software, Chicago, IL) was performed on all radiographic measurements to detect difference in ROM between DM-THA and 36-THA, and to detect difference in ROM between THAs performed through posterolateral (THA-PL) and anterolateral (THA-AL) approaches.


Omid Alizadehkhaiyat David Hawkes Simon Frostick

Introduction

Rehabilitation after shoulder arthroplasty is a fundamental in enabling patients achieve a good functional outcome. Therapists must consider the underlying diagnosis, operative technique employed and rotator cuff integrity, amongst other factors, in order to select the most appropriate exercise regime. There is an absence of comprehensive studies in the literature with regard to shoulder rotational exercises. Therefore, this study aimed to describe the shoulder girdle muscle activation strategies during eight commonly cited rotational shoulder exercises.

Method

Thirty healthy subjects with no history of shoulder problems participated in the study. EMG was recorded from 16 shoulder girdle muscles (surface electrodes: anterior, middle and posterior deltoid, upper, middle and lower trapezius, upper and lower latissimus dorsi, upper and lower pectoralis major; fine wire electrodes: supraspinatus, infraspinatus, subscapularis and rhomboid major) using a telemetry based EMG system. Five external and three internal rotation exercises were included (table 1). Signal acquisition and processing were in accordance with standardised guidelines. Amplitude normalisation was to external and internal rotation maximum voluntary contraction as appropriate. Mean EMG amplitudes between exercises were compared using repeated measures ANOVA. Data for muscle groups was calculated by averaging the activation of the component muscles.


Heath Henninger Robert Burks Robert Tashjian

Introduction:

Given that factors like center of rotation (COR), neck shaft angle, glenosphere diameter and component tilt alter the biomechanics of reverse total shoulder arthroplasty (rTSA), the performance of the total rTSA system is of interest. This study compared the composite performance of two rTSA systems that were designed around a medialized or lateralized glenohumeral COR. The objective was to quantify the following outcome measures: 1) COR & humeral position; 2) range of glenohumeral abduction; 3) force to abduct; and 4) range of internal (IR)/external (ER) rotation.

Methods:

Seven pairs of shoulders were tested with a biomechanical shoulder simulator. Beads were implanted in the scapula and humerus to quantify bone positions with a fluoroscope. Spectra lines simulated the deltoid and the rotator cuff. Linear actuators simulated muscle excursion while load cells recorded applied force. Diode arrays were used to quantify arm position and calculate the humeral center of rotation. Native specimens were tested where a motion path was recorded from resting to peak glenohumeral abduction in the scapular plane. The trajectory was replayed and deltoid force vs. arm position was recorded. With the elbow flexed, the arm was articulated to maximal internal and external rotation to determine ROM limits due to impingement or soft tissue constraint. Specimens were implanted with a Tornier Aequalis Reversed Shoulder prosthesis (“A,” 36 mm glenosphere, 10° humeral retroversion, 9 mm poly insert – “medial”) or a DJO Surgical Reverse Shoulder Prosthesis (“R,” 32 mm, 30° retroversion, neutral insert/shell – “lateral”). Implants were randomized between shoulders in a pair. After implantation the test protocol was repeated. Paired-t tests (p ≤ 0.050) were adjusted with Holm's step-down correction for multiple comparisons.


Michael Howard Danielle Anthony Kirby Hitt David Jacofsky Eric Smith Fabio Orozco

Introduction:

Revision total knee arthroplasty (TKA) can be very complex in nature with difficulties/obstacles involving bone and soft tissue deficits, visualization and exposure, as well as alignment and fixation. Auxiliary devices such as augmentation and offset adapters help address these issues; however they increase the complexity of the reconstruction. The objective of this study was to show that use of a single radius revision TKA system allowing for minimal auxiliary revision devices can yield positive early clinical outcomes.

Methods:

This data was collected as part of a prospective, post-market, multicenter study. One hundred and twenty-five single radius revision TKA cases were evaluated. Surgical details were reviewed and cases were grouped based on type of auxiliary devices used. Group 1 included cases that used only femoral and/or tibial augments. Group 2 used femoral and/or tibial augments in conjunction with femoral and/or tibial offset adapters. Early clinical outcomes, operative data and radiographic findings were used to compare cases.


Heinz Hoenecke Cesar Flores-Hernandez Juan Hermida Andrew Kersten Darryl D'Lima

Introduction:

Total shoulder arthroplasty (TSA) is the current standard treatment for severe osteoarthritis of the glenohumeral joint [1]. Often, severe arthritis is associated with abnormal glenoid version or excessive posterior wear [2]. Reaming to correct more than 15° of retroversion back to neutral is not ideal as it may remove an excessive amount of the outer cortical support and medialize the glenoid component [3]. Two recent glenoid components with posterior augments—wedged and stepped—have been designed to address excessive posterior wear and to allow glenoid component neutralization. Hypothetically, these augmented glenoid designs lessen the complications associated with using a standard glenoid component in cases of shoulder osteoarthritis with excessive posterior wear. We set out to determine which implant type (standard, stepped, or wedged) corrects retroversion while removing the least amount of bone in glenoids with posterior erosion.

Methods:

Serial shoulder CT scans were obtained from 121 patients before total shoulder arthroplasty. These were then classified using the Walch Classification. We produced 3D models of the scapula from CT scans for 10 subjects that were classified as B2 using the software MIMICS (Materialise, Belgium). Each of these 10 glenoid subjects were then virtually implanted with standard, stepped, and wedged glenoid components (Fig 1). The volume of surgical bone removed and maximum reaming depth were calculated for each design and for each subject. In addition, the area of the backside of the glenoid in contact with cancellous versus cortical bone was calculated for each glenoid design and for each subject (Fig 2). ANOVA testing was performed.


Harry Hothi Reshid Berber Robert Whittaker Suzie Cro Gordon Blunn John A. Skinner Alister Hart

Introduction

It has been suggested that corrosion and fretting at the taper junctions of stemmed metal-on-metal hip replacements may contribute to their high failure rates. A peer-reviewed semi-quantitative scoring system [Goldberg et al., 2002] has been used to visually assess the severity of corrosion and fretting of the taper junction but has not been validated using multiple examiners. The aim of this study was to assess the inter-observer variability of this method.

Method

Macroscopic and stereomicroscopic examinations of the femoral head and stem tapers of 100 retrieved large diameter metal on metal (MOM) hip components were performed by two independent observers using the methods defined by Goldberg et al. [2002] to quantify corrosion and fretting. Scores ranging from 1 (none) to 4 (severe) were assigned to the medial, lateral, posterior and anterior quadrants of the neck taper and the distal and proximal regions of the head taper. An overall score was then assigned to each surface as a whole.

Cohen's weighted Kappa statistic (κ) was used to measure the inter-observer agreement. A quadratic weighting scheme, that allocated weights to the importance of disagreements that are proportional to the square of the number of categories apart, was used to take account of scaled disagreement.

Kappa values were assessed using previously established criteria where κ ≤ 0 = poor, 0.01 to 0.20 = slight, 0.21 to 0.40 = fair, 0.41 to 0.60 = moderate, 0.61 to 0.80 = substantial, 0.81 to 1 = almost perfect.

A sample size of 100 was used in order to detect a coefficient of 0.60 to within 0.25 with 95% confidence with two experienced observers. Statistical analysis was performed using Stata/IC version 12.1 (StataCorp, College Station, TC, USA) and a p value < 0.05 was considered statistically significant.


Harry Hothi Suzie Cro Paul Bills Liam Blunt Radu Racasan Gordon W Blunn John A. Skinner Alister Hart

Introduction

Metal-on-metal (MOM) total hip arthroplasty using large diameter femoral heads offer clinical advantages however the failure rates of these hips is unacceptably high. Retrieved hips have a wide range of wear rates of their bearing and taper surfaces and there is no agreement regarding the cause of failure.

Detailed visual inspection is the first step in the forensic examination of failed hip components and may help explain the mechanisms of failure. The aim of this study was to determine if there was a correlation between the results of detailed inspections and the volumetric wear of the bearing and taper surfaces of retrieved hips.

Method

Detailed, non-destructive macroscopic and stereomicroscopic examinations of 89 retrieved MOM hip components were performed by a single experienced examiner using quantitative assessment to document the severity of 10 established damage features:

Light scratches, Moderate scratches, Heavy scratches, Embedded particles, Discolouration, Haziness, Pitting, Visible wear zone, Corrosion, Fretting

Each surface was considered in terms of zones comprising of quadrants (cup, head, and taper) and subquadrants (cup and head), Figure 1. Each zone was scored on a scale of 0 to 3 by determining the percentage of the surface area of the zone that exhibited the feature in question: a score of 0=0%, 1<25%, 25%<2<75%, 3>75%. The sum of the scores of each zone was used for the assessment of each damage feature.

The volume of wear at the surfaces of each hip was measured with a Zeiss Prismo coordinate measuring machine (cup and head) and a Talyrond 365 roundness measurement instrument (taper), using previously reported methods1, 2.

Simple linear regression models were used to asses the univariable associations between the inspection scores and wear volumes. Multiple linear regression models were subsequently used to asses the simultaneous contribution of the inspection scores, found significant in univariable analyses, on the wear outcome variables.

All statistical analysis was performed using Stata/IC version 12.1 (StataCorp, USA) and throughout a p value < 0.05 was considered statistically significant.


Joseph Iannotti

Accurate implant placement is important to the success of joint replacement surgery. Three dimensional pre-operative planning optimizing the ability to define the anatomy and select the desired implant and its location. Linking this information into implant and patient specific instrumentation has been termed smart instrumentation. Single use instruments contain the patient's topographical boney anatomy and implant information. This same information can be placed within a bone model and a reusable instrument placed onto the bone model can be adjusted to capture the information originally in the planning software. This instrument can then be placed into the surgical site, registered to the bone surfaces and used to modify the bone surfaces to replicate the surgical plan. These concepts, technology and devices have been developed and clinically tested in randomized clinical trials for shoulder arthroplasty.


Joseph Iannotti

Advanced 3D CT imaging of the shoulder using metal artifact reduction techniques have been developed and validated in pre-clinical and patient population using microscribe and RSA techniques. These studies demonstrate these methods to be highly accurate and reproducible in the measurement of implant position and implant migrations. 3D CT imaging is being used to study the anatomic and clinical factors associated with glenoid implant loosening. This imaging modality does not require marker based image registration and utilizes imaging equipment that is readily available in the clinical setting.


Hirotaka Iguchi Hiroto Mitsui Satona Murakami Nobuyuki Watanabe Kaneaki Tawada Masahiro Nozaki Hideyuki Goto Masaaki Kobayashi Takanobu Otsuka

Introduction

We have been developed lateral flare stem and have been using it since 1989. It was custom stem at first. After being experienced, using the same software, off-the-shelf version lateral flare stem (Revelation) was developed in 1996 in the U.S. We could start using it since 2001 in our country. Lateral flare stems are designed to reproduce physiological proximal load transfer lateral side as well as medial side. It was obtained by having bigger and more accurate proximal part with lateral flare. The design is optimized by matching with 3D insertion path.

Using many custom stems including different length and off-the-shelf standard stems, we have come to feel that as for this high proximal fit and load transfer design, it is not necessary to having long distal part and sometimes it is harmful to obtain good proximal load transfer in some situation such as type A (champagne flute) canal. So we have developed short version of the stem. Many makes of the hip stems have included short stems recently. Some aimed to improve easier insertion, some aimed to improve the volume of residual bone quantity. We have aimed to improve proximal fit expecting more proximal and more physiological load transfer to the femur.

Objectives

Our objectives are to comare standard stem and short stem from biomechanical aspect and clinical aspect.


Hirotaka Iguchi Hiroto Mitsui Satona Murakami Nobuyuki Watanabe Kaneaki Tawada Masahiro Nozaki Masaaki Kobayashi Takanobu Otsuka

Introduction

Massive defect of the acetabular bone is one of the severe situation in the hip arthroplasty. Installation of cup supporter or acetabular reinforcement device is one of the important method as well as big cup and bone graft etc. Preparing the device to be suitable shape is very important and installing it at the very position where the shaping was intended is also very important to obtain a stable condition for the arthroplasty. When we use navigation system, the device must be programmed in. But it is impossible to programme a device we have bended by ourselves into the system. If we can use a navigation system for such devices for those cases, we can expect better installation. We can fit the device on the patient's bone during the surgery of course; which is the ordinary procedure fot it; but it requires much time and tissue damage maybe with less accurate fitting.

Materials and Methods

Two primary and three revision total hip arthroplasty cases with severe acetabular bone defect were treated with this method. First we have made chemical wood model for each case and bended the cup supporter on it. (Fig. 1) Then CAT scan of the model and the bended device on it were taken. Then the coordinate system of DICOM data set of the patient's original pelvis and the second DICOM data set i.e. the bended prosthesis were unified using MIMICS (Materialize, Belgium.) An STL format geometry data file of the bended device was extracted and merged into original DICOM dataset. Thus we could obtain a DICOM data set we call “predicted post-op DICOM.” During the surgery, a navigation system was used based on the predicted DICOM data.


Obinna Ihesiulor

Mechanical wear and corrosion lead to the release of metal particulate debris and subsequent release of metal ions at the trunnion-taper surface. In order to quantify the amount of volume loss to ultimate locations in the surrounding joint space, finite element analysis of the modular head-stem junction is being carried out. The key purpose being to determine a set of optimum design changes that offer the least material loss at the taper-trunnion junction using optimization algorithms such as the gradient based local search (Sequential Quadratic Programming–SQP) and global search (Non-Dominated Sorting Genetic Algorithm-II–NSGA-II). In a broader sense, the principal goal is to work toward the minimization of wear debris produced in the hip joint, thereby resulting in a longer prosthetic lifetime.

A numerical approach that simulates wear in modular hip prostheses with due consideration to the taper-trunnion junction on metal-on-metal contacts is proposed. A quasi-static analysis is performed considering realistic loading stages in the gait cycle, and nonlinear contact analysis is to be employed. The technique incorporates a measured wear rate as an input to the finite element model. The simulation of wear is performed by progressively changing nodal coordinates to simulate the wear loss that occurs during surface interaction. The geometry of the worn surface is updated under gait loading. With a given geometry and gait loading, the linear and volumetric wear increases with the number of gait cycles. The continuous wear propagation is discretized and an approximation scheme known as surrogates is to be developed using Artificial Neural Networks (ANN) to reduce the expensive computational simulations during optimization.

The model is employed in the optimization schemes coded in MATLAB and linked to the finite element model developed in ANSYS batch mode. The objective function of the optimization problem is to minimize the volumetric wear at taper-trunnion interface under some constraints. By minimizing the volumetric wear, the chance of failure of modular hip implants is also minimized. The FE model developed to reproduce fretting wear is validated through in vitro wear simulations.

The important taper design variables considered to have impact on the fretting corrosion performance include; medial-lateral offset, neck length, taper head diameter, trunnion length and diameter, included angle for the head/neck tapers, angle of mismatch or variation in taper trunnion angle, etc. It is expected from clinical outcomes that increased offset and large taper diameter has serious implications in the fretting corrosion behavior primarily because these variables control the bending stresses and strains along the length of the taper. During cyclic loading of the taper, the higher the strain range, the higher will be the relative micromotion at the point of engagement between the stem and head tapers. This research is carried out with the objective to optimize the effects of these geometrical factors at the mating taper interfaces.

The developed models have great potentiality for accurate assessment of wear in a range of metal-on-metal (MoM) hip prostheses at the femoral head taper-trunnion junction while substantially reducing the wear and failure rate of prostheses.


Sabir Ismaily Rikin Patel Alex Suarez Stephen Incavo Michael Paul Bolognesi Philip Noble

Introduction

Malpositioning of the tibial component is a common error in TKR. In theory, placement of the tibial tray could be improved by optimization of its design to more closely match anatomic features of the proximal tibia with the motion axis of the knee joint. However, the inherent variability of tibial anatomy and the size increments required for a non-custom implant system may lead to minimal benefit, despite the increased cost and size of inventory.

This study was undertaken to test the hypotheses:

That correct placement of the tibial component is influenced by the design of the implant.

The operative experience of the surgeon influences the likelihood of correct placement of contemporary designs of tibial trays.

Materials and Methods

CAD models were generated of all sizes of 7 widely used designs of tibial trays, including symmetric (4) and asymmetric (3) designs. Solid models of 10 tibias were selected from a large anatomic collection and verified to ensure that they encompassed the anatomic range of shapes and sizes of Caucasian tibias. Each computer model was resected perpendicular to the canal axis with a posterior slope of 5 degrees at a depth of 5 mm distal to the medial plateau. Fifteen joint surgeons and fourteen experienced trainees individually determined the ideal size and placement of each tray on each resected tibia, corresponding to a total of 2030 implantations. For each implantation we calculated: (i) the rotational alignment of the tray; (ii) its coverage of the resected bony surface, and (iii) the extent of any overhang of the tray beyond the cortical boundary. Differences in the parameters defining the implantations of the surgeons and trainees were evaluated statistically.


Philip Noble Sabir Ismaily Jonathan Gold Drew Stal Adam Brekke Jerry Alexander Kenneth Mathis

Introduction:

Despite all the attention to new technologies and sophisticated implant designs, imperfect surgical technique remains a obstacle to improving the results of total knee replacement (TKR). On the tibial side, common errors which are known to contribute to post-operative instability and reduced function include internal rotation of the tibial tray, inadequate posterior slope, and excessive component varus or valgus. However, the prevalence of each error in surgeries performed by surgeons and trainees is unknown. The following study was undertaken to determine which of these errors occurs most frequently in trainees acquiring the surgical skills to perform TKR.

Materials and Methods:

A total of 43 knee replacement procedures were performed by 11 surgical trainees (surgical students, residents and fellows) in a computerized training center. After initial instruction, each trainee performed a series of four TKR procedures in cadavers (n = 2) and bone replicas (n = 2) using a contemporary TKR instrument set and the assistance of an experienced surgical instructor. Prior to each procedure, computer models of each cadaver and/or bone replica tibia were prepared by reconstructing CT scans of each specimen. All training procedures were performed in a navigated operating room using a 12 camera motion analysis system (Motion Analysis Inc.) with a spatial resolution in all three orthogonal directions of ± 0.15 mm.

The natural slope, varus/valgus alignment, and axial rotation of the proximal tibial surface were recorded prior to surgery and after placement of the tibial component. For evaluation of all data, acceptable limits for implantation were defined as: posterior slope: 0–10°; varus/valgus inclination of tibial resection: ± 3°; and external rotation: 0–10°.


B. Sonny Bal Conrad Ivie Matthew Davis Brett Crist

Introduction:

Patient-specific cutting guides (PSCG) built from imaging of the extremity can improve the accuracy of bone cuts during total knee replacement (TKR). Some reports have suggested that PSCG offer only marginal improvement in the accuracy of alignment and component positioning in TKA. We compared outcomes between TKRs done with PSCG versus standard, intramedullary-based instrumentation.

Methods:

Blood loss, duration of surgery, alignment of the mechanical axis of the leg, and implant position on standing, long-leg, and standard lateral digital radiographs were compared between a CT-guided, custom-built TKA implant (n = 50; ConforMIS iTotal, Boston, MA) implanted with PSCG, versus an off-shelf posterior stabilized TKA implanted with standard instrumentation (n = 50; NKII total knee, Zimmer, Warsaw, IN). The fraction of outliers (>3 degrees) was calculated for the two groups.


Viktor Janz Georgi I. Wassilew Georg Matziolis Stephan Tohtz Carsten Perka

Introduction

The utilization of sonicate fluid cultures (SFC) has been shown to increase the detection rate of periprosthetic joint infection (PJI) in comparison to the use of conventional microbiological methods, because sonication enables a sampling of the causative bacteria directly from the surface of the endoprosthetic components. The hypothesis of this study is that not only will the detection rate of PJI be improved, but also the detection rate of polymicrobial infection in patients with total knee arthroplasty (TKA) revision surgery.

Material and methods

74 patients which underwent TKA revision surgery received a synovial aspiration, intraoperative tissue cultures, histological sampling of the periprosthetic membrane, and sonication of the explanted endoprosthesis. A PJI was defined according to the following criteria: presence of intraarticular pus or a sinus tract, positive isolation of causative bacteria in ≥2 microbiological samples or a histological membrane indicative of infection (type II or III periprosthetic membrane).


Viktor Janz Georgi I. Wassilew Stephan Tohtz Carsten Perka

Introduction

Sonicate fluid cultures (SFC) are more sensitive than conventional microbiological methods in identifying periprosthetic joint infections (PJI), because sonication enables a sampling of the causative bacteria directly from the surface of the endoprosthetic components. Because of their high sensitivity SFC can be positive while all other microbiological methods remain negative. It is therefore difficult to interpret a single SFC as being truly or falsely positive. The aim of this prospective study was to improve the interpretation of SFC in the diagnosis of PJI in patients after total hip arthroplasty through the use of multiple SFC.

Material and methods

102 patients of which 37 had a defined PJI according to the following criteria were included: intraarticular pus or a sinus tract, a periprosthetic membrane (PM) indicative of infection, or a positive microbiological culture in a minimum of 2 separate microbiological samples. A single positive microbiological sample was classified as false positive. In 35 patients multiple SFC were acquired from the separate endoprosthetic components.


Pramod Kumar Puthumanapully Andrew Amis Simon Harris Justin Cobb Jonathan Jeffers

Introduction:

Varus alignment of the knee is common in patients undergoing unicondylar knee replacement. To measure the geometry and morphology of these knees is to know whether a single unicondylar knee implant design is suitable for all patients, i.e. for patients with varus deformity and those without. The aim of this study was to identify any significant differences between normal and varus knees that may influence unicondylar implant design for the latter group.

Methodology:

56 patients (31 varus, 25 normal) were evaluated through CT imaging. Images were segmented to create 3D models and aligned to a tri-spherical plane (centres of spheres fitted to the femoral head and the medial and lateral flexion facets). 30 key co-ordinates were recorded per specimen to define the important axes, angles and shapes (e.g. spheres to define flexion and extension facet surfaces) that describe the femoral condylar geometry using in-house software. The points were then projected in sagittal, coronal and transverse planes. Standardised distance and angular measurements were then carried out between the points and the differences between the morphology of normal and varus knee summarised. For the varus knee group, trends were investigated that could be related to the magnitude of varus deformity.


Claire Brockett Abdellatif Abdelgaied Catherine Hardaker John Fisher Louise Jennings

Introduction

Wear debris induced osteolysis and loosening continue to be causes of clinical failure in total knee replacement (TKR). Laboratory simulation aims to predict the wear of TKR bearings under specific loading and motion conditions. However, the conditions applied may have significant influence on the study outcomes (1)

The aim of this study was to examine the influence of femoral setup and kinematic inputs on the wear of a conventional polyethylene fixed bearing TKR through experimental and computational models.

Methods

Six right Sigma CR fixed bearing TKRs (DePuy Synthes, Leeds, UK) with curved polyethylene inserts (GVF, GUR1020 UHMWPE) were tested in Prosim knee simulator (Simulator Solutions, UK). The femoral bearing was set up with the centre of rotation (CoR) on either on the distal radius of the implant (Distal CoR), as indicated by the device design, or according to the ISO specification (ISO CoR; ISO14243-3). The tests were conducted under ‘High Kinematics’ (2). It was necessary to reverse the direction of the anterior-posterior displacement for the tests conducted with the ISO centre of rotation to maintain the contact region within the insert surface (Reverse High Kinematics). Tests were conducted for three million cycles, lubricated with 25% bovine serum, with wear assessed gravimetrically.

The computational wear model for the TKR was based on the contact area and an independent experimentally determined non-dimensional wear coefficient, previously validated against the experimental data (3).


Johannes F. Plate Marco Andre Augart Daniel Bracey Sarah Von Thaer John Allen Dan Sun Gary Poehling Riyaz Jinnah

Introduction

There has been renewed interest in the use of unicompartmental knee arthroplasty (UKA) for patients with limited degenerative disease of the knee due to improved surgical techniques and prosthetic design, and the desire for minimally invasive surgery. However, patient satisfaction following UKA for lateral compartment disease have been suboptimal with increased revision rates. Robotic-assisted UKA has been shown to improve precision and accuracy of component placement, which may improve outcomes of lateral UKA. The purpose of this study was to compare the outcome of robotic-assisted UKA to conventional UKA for degenerative disease of the lateral compartment with the hypothesis that robotic-assisted lateral UKA results in superior outcomes compared to conventional UKA.

Methods

The institution's joint registry was searched for patients who underwent UKA for limited degenerative disease of the lateral knee compartment between 2004 and 2012 and a total of 125 lateral UKAs were identified. The medical records of all patients were reviewed and assessed for the type of surgical procedure used (robotic-assisted versus conventional), length of hospital stay, Oxford knee score, and occurrence of revision surgery. Preoperative and postoperative radiographs were assessed for tibiofemoral angle, femoral and tibial joint line angle, posterior tibial slope, and orientation of the femoral and tibial components.


Nathan Jové David Markel Sam Samaan Denis Lincoln

Introduction:

A pulmonary embolus (PE) occurs frequently in medical patients and acutely in post surgical total joint patients. While the two groups seem vastly different, there has never been an analysis of the location, number of emboli a patient has and size of the emboli in post-operative total joint arthroplasty patients compared to general medical patients. Studies have looked at the size of PEs relative to symptomatic patients; recent data have suggested the timeline of PE development is usually within the first few days after total knee arthroplasty (TKA) or total hip arthroplasty (THA).

Methods:

We conducted a retrospective chart review at Providence Hospital from 2006 to 2011 of all THA and TKA patients who had a post-operative PE diagnosis and looked at their medical comorbidities, sex, age, procedure, post-operative day of PE, and size/location of PE using a novel pulmonary mapping tree database based on location of the PE on spiral computed tomography (CT). The same data, except for post-operative day, was collected for the medical population with a PE diagnosis. Size was defined based on level of blockage with small emboli occurring at different points within a lobe, medium being at the level of lobe, and large being either a saddle embolus or at the right or left pulmonary artery. Inclusion criteria for orthopaedic patients included THA or TKA performed prior to PE, PE within 1 month of surgery and CT confirming diagnosis of a PE. Medical patients meeting criteria had to have an admitting diagnosis of PE with CT confirmation of the PE. Exclusion criteria included V/Q scan alone to diagnose the PE.


Bong Jae Jun Zong-Ming Li Joseph Iannotti

Background:

Glenoid component loosening remains as an unsolved clinical problem in total shoulder arthroplasty. Current clinical assessment relies on subjective quantification using a two-dimensional plane X-ray image with arbitrarily defined criteria. There is a need to develop a readily usable clinical tool to accurately and reliably quantify the glenoid component motion over time after surgery. A high-resolution clinical CT has the potential to quantify the glenoid motion, but is challenged by metal artifact from the prosthetic humeral components. The objective of this study is to demonstrate the feasibility of using a clinical CT reconstruction to quantify the glenoid implant motion with the aid of tantalum markers.

Methods:

Three spherical tantalum markers of 1.0 mm in diameter were inserted into three peripheral pegs of an all polyethylene glenoid component. The glenoid component was implanted in a sawbone scapula. To determine the effect of metal artifact on quantification of glenoid implant motion, two sawbone humerii were used: one without the prosthetic humeral components and the other with the prosthetic humeral head and stem. Three custom-made translucent spacers with the uniform thickness were placed between the glenoid component and the scapula to produce a gradual translation of the glenoid component from 1 mm to 3 mm. Before and after inserting each spacer, the surface of the glenoid component was digitized by a MicroScribe. The surface points were used to fit a sphere and the corresponding center of the sphere was calculated. The actual translation of the glenoid component was measured as the three-dimensional (3D) distance between the center of the sphere before and after insertion of each spacer. Then, the shoulder model was scanned by a clinical CT with and without the spacers for both humerii conditions. Velcro straps were used to secure the humerus to the glenoid component between the trials. All CT scans were reconstructed in VolNinja software to superimpose the scapula positions (Figure 1). The three tantalum markers were visualized and the center coordinates of the markers were used to measure the 3D distance before and after insertion of each spacer. The accuracy was defined by the difference between the averaged 3D distance measured by CT reconstruction and that measured by the MicroScribe. The standard deviation of the 3D distance measured by each tantalum marker was calculated to evaluate the reliability of the tantalum marker visualization.


Christian Kaddick Robert Streicher

As allergic reactions to implant wear are gaining more attention [4], the incorporation of ceramic materials to device design appears to be a promising development. In particular, ceramic femoral components of total knee replacements have been designed to produce less wear under standard [1] and adverse [5] implant conditions.

Whereas the wear reduction effect of ceramics is generally accepted for hip implants, the corresponding effect for knee implants is not proven. Ezzet et al. reported a wear reduction of 42% for standard wear conditions [2] and of 55% for adverse wear conditions [3] when compared to a geometrically identical CoCr femoral component. In contrast to these findings, an analysis of the EndoLab® database has indicated wear rates of ceramic knee implants that are comparable to traditional low wear material couplings (Figure 1), and are within the range of clinically established devices.

The purpose of this study was to directly compare two TKR designs, one fixed bearing and one mobile bearing, each made of traditional CoCr to one made of alumina matrix composite (BIOLOX®delta, CeramTec, Germany) ceramic material. The BPK-S Rotating Platform System (Peter-Brehm, Germany; Figure 2) and the MULTIGEN PLUS fixed bearing (Lima, Italy) were knee simulator wear tested according to ISO 14243-1 (2002). A total of three specimens plus one loaded soak control for each group (four groups in total) was subjected to 5 million standard gait cycles. The anterior-posterior (AP) and internal-external rotational (IE) motion of the implants resulting from the external load application of this force controlled test was recorded continuously. Wear was determined gravimetrically. The surface appearance of contact areas was analyzed by light microscopy and particle analysis was performed according to ISO 18129. For the mobile bearing groups, a mean wear rate of 2.47 mg per million cycles (StdDev. 0.38) was determined for the CoCr implant and of 1.10 mg per million cycles (StdDev. 0.46) for the BIOLOX®deltaimplant (Figure 3). The total AP and IE motion of the two groups did not differ. However, motion during stance phase was considerably higher for the ceramic group, indicating reduced frictional resistance (data not shown).

For the fixed bearing groups, a mean wear rate of 12.01 mg per million cycles (StdDev. 3.28) was determined for the CoCr implant and of 1.78 mg per million cycles (StdDev. 0.40) for the BIOLOX®delta implant.

Based upon the EndoLab® experience the ceramic total knee replacements tested perform as good as the best performing metallic total knee replacements. However it can be concluded that for the two implant systems tested the wear rate is reduced by more than 50% by using ceramic on polyethylene articulation when compared to an identical cobald crome design.


Robert Streicher Leslie Scheuber Usbeck Sylvia Christian Kaddick Martin Hintner

Introduction

From a tribological point of view and clinical experience, a ceramic-on-ceramic bearing represents the best treatment option after rare cases of ceramic component fracture in total hip arthroplasty (THA). Fractured ceramic components potentially leave small ceramic fragments in the joint capsule which might become embedded in PE acetabular liners.

Purpose

This in vitro study compared for the first time the wear behaviour of femoral ball heads made of ceramic and metal tested with PE liners in the presence of ceramic third-body debris.

The contamination of the test environment with third-body ceramic debris, insertion of ceramic fragments into the PE liners and implementation of continuous subluxation simulated a worst-case scenario after revision of a fractured ceramic component.


Rami Kallala Mazin Ibrahim Fares Haddad

Revision surgery for total knee replacement is a complex procedure, carrying an increased risk for the patient and cost for hospitals. As well as increased cost of peri-operative investigations, blood transfusions, surgical instrumentation, implants and theatre time, there is a well documented increased length of stay (LOS), accounting for the majority of actual costs associated with surgery.

We compared revision surgery for infection vs. other causes (aseptic loosening, dislocation, mal-alignment). Clinical, demographic and economic data were obtained for 180 consecutive revision total knee replacements performed at a tertiary referral centre between 2003 and 2012. Actual costs and National Health Service tariffs were compared per patient and mean difference calculated.

Mean age was 66 years (range 17–87) with 62 male and 117 female patients. Mean LOS for aseptic cases was 10 days (range 1–62) and 20 days (range 4–103) for infection. Mean cost difference in aseptic cases (n = 125) was £−933 (SD = £12,204), and £−3907 (SD = £7,256) for infection (n = 54).

Surgery for infection was associated with increased operating times, blood loss and complications compared to revision for aseptic causes. LOS for infection was on average double that for aseptic cases (p < 0.05). Current NHS tariffs do not fully reimburse the increased costs associated with providing a revision knee surgery service, with even greater cost incurred by the treating hospital for infected cases. These losses may negatively influence the provision of revision surgery in the NHS.


Ryutaku Kaneyama Hideaki Shiratsuchi Kazuhiro Oinuma Yoko Miura Hidetaka Higashi Tatsuya Tamaki Kurato Jonishi

Introduction:

Total knee arthroplasty (TKA) should aim to adjust the component gap (CG) difference between extension and flexion. However, this difference cannot be measured without placement of a femoral component. The bone gap reportedly decreases in extension after component setting. In contrast, it may be possible to use the mean value of the CG difference in several patients to adjust femoral resection amount beforehand. The purpose of this study is to evaluate the technique of adjusting CG difference using the mean values with measured resection technique (MRT) in TKA.

Materials and methods:

The subjects were 222 knees (40 male knees, 182 female knees; mean age 70.4 years). To adjust the CG difference after estimation, the femoral posterior condylar pre-cut technique was used. Extension gap was created by usual bone resection; 4 mm of the femoral posterior condyle was pre-cut, and after all osteophytes and soft tissues had been treated, a pre-cut trial component (thickness of 8 mm for distal femur and 4 mm for posterior condyle without the anterior portion) was mounted, achieving the same condition as the setting of a femoral component in MRT (Fig. 1). When the posterior cruciate ligament (PCL) could be easily preserved by intraoperative gap assessments, the PCL was preserved (190 knees, 86%).


Aaron Kavanaugh Thomas Schmalzried Fabrizio Billi

Questions/purposes:

What factors influence tibial tray-cement interface bond strength? We developed a laboratory model to investigate this issue with the goal of providing technical recommendations to mitigate the risk of tibial tray-cement loosening.

Methods:

Forty-eight size 4 Triathlon® tibial trays were cemented into an acrylic holder using two different cements: Simplex® and Palacos®; three different cementing times: early (low viscosity), per manufacturer (normal, medium viscosity), and late (high viscosity); two different cementation techniques: cementing tibial plateau only and cementing tibial plateau and keel; and two different fat (marrow) contamination conditions: metal/cement interface and cement/cement interface. A push-out test was applied at a velocity of 0.05 mm/s, and the load recorded continuously throughout the test at a rate of 10 Hz. The test was stopped when the plate debonded from the cement (i.e. the tray visibly separated from the acrylic support and the load dropped substantially). Statistical analysis was performed using Welch's t-tests and Cohen's d tests.


Tsutomu Kawano Hidetoshi Ihara Susumu Tsurusaki

[Introduction]

One of the modern design total knee arthroplasty (TKA) system, the NexGen Legacy posterior-stabilized (LPS) Flex prosthesis, has been in use at our hospital since 2001. Between 2006 and 2011, NexGen LPS-Flex primary TKA were mainly performed in combination with a cemented short-keeled minimally invasive version tibial tray (MIS tibial component) instead of the traditional NexGen stemmed tibial tray. We observed some cases required early revision of isolated tibial component in primary TKA performed in this period. Therefore, our objectives were to report the series of this revision cases and to consider this failure mechanism.

[Patients & Methods]

A total of 526 primary TKAs were performed using a NexGen LPS-Flex prosthesis and MIS tibial component during five-year period at our hospital. The mean age was 74 years at the time of the index procedure. We assessed revision rate of this tibial tray in this study and described clinical course of the revision cases. We also examined the clinical and radiographic features which could be associated with the failure.


Oliver Kessler

INTRODUCTION:

One common surgical treatment of even early OA is the implantation of a Total Joint Arthroplasty. In case of younger patients this procedure is questionable. The present study investigates the behaviour of a new silk derived scaffold supplied by Orthox Ltd. (Abingdon, UK) in an in vivo sheep model. This scaffold allows replacing the damaged areas with a resurfacing technique and will avoid the implantation of a total joint in cases of early OA.

METHODS:

The scaffolds where derived from silk fibres by processing into a composite of an open porous matrix in combination with a fibres mash with the same material and covered with a smooth surface. During the process the fluid silk can be casted in any shape. Eight sheep (4 ± 1 years) underwent a surgery where a large defect (2×1 cm) was created in the weight bearing zone of the medial condylus followed by implantation of a scaffold. The unoperated contra lateral stifle joint served as control.

After six months the animals were sacrificed and the joints inspected for inflammation. The Young's modulus of the cartilage and scaffold was determined by indentation or confined compression tests. All tissues were fixed in formaldehyde for histology. The data were analysed by a Wilcoxon and Mann-Whitney-U-test. The roughness of the smooth surface was measured. Synovial fluid was harvested by punction before opening the joint and analysed for particle wear debris and for any signs of inflammation.


Brian Gladnick Saker Khamaisy Denis Nam Keith Reinhardt Andrew Pearle

Introduction

Limb alignment after unicondylar knee arthroplasty (UKA) has a significant impact on surgical outcomes. The literature lacks studies that evaluate the limb alignment after lateral UKA or compare alignment outcomes between medial and lateral UKA. In this study, we retrospectively compare a single surgeon's alignment outcomes between medial and lateral UKA using a robotic-guided protocol.

Methods

All surgeries were performed by a single surgeon using the same planning software and robotic guidance for execution of the surgical plan. The senior surgeon's prospective database was reviewed to identify patients who had 1) undergone medial or lateral UKA for unicompartmental osteoarthritis; and 2) had adequate pre- and post-operative full-length standing radiographs. There were 229 medial UKAs and 37 lateral UKAs in this study. Mechanical limb alignment was measured in standing long limb radiographs both pre- and post-operatively. Intra-operatively, limb alignment was measured using the computer assisted navigation system. The primary outcome was over-correction of the mechanical alignment (i.e, past neutral). Our secondary outcome was the difference between the radiographic post-operative alignment and the intra-operative “virtual” alignment as measured by the computer navigation system. This allowed an assessment of the accuracy of our navigation system for predicting post-operative limb alignment after UKA.


Hasung Kim Kyung-Soon Park Jae-Wook Byun Taek Rim Yoon

Purpose

The purpose of this study is to evaluate the midterm results of cementless revision total hip arthroplasty (THA) using Wagner Cone Prosthesis.

Material and Methods

Between 1996 and 2007, 36 hips in 36 consecutive patients underwent femoral revision THA using Wagner Cone Prosthesis. Among them 28 hips were followed for more than 5 years. The mean age at revision surgery was 57 years and a mean follow-up was 7.6 years. The Paprosky classification system was used for preoperative bone loss evaluation. Clinical results were evaluated using Harris hip scores. For evaluation of the femoral component, radiolucent lines at bone-implant interfaces were evaluated and femoral component vertical subsidence was measured. Heterotopic bone formation and complications were also evaluated.


Christopher Stevens Jay King Aimee Struk Thomas Wright

Background:

The use of reverse total shoulder arthroplasty (RTSA) has been increasing around the world. However, because of concerns over lack of internal rotation with the reverse prosthesis and the resultant difficulties with activities of daily living (ADLs), many have recommended against performing bilateral RTSA.

Methods:

We performed a retrospective review of prospectively obtained clinical data on 15 consecutive patients (30 shoulders) that underwent staged bilateral primary RTSA for the diagnosis of cuff tear arthropathy (CTA) between 2004 and 2012. All operations were performed by a single surgeon. The mean follow-up was 29.6 months from the second RTSA (range 12–65 months). The mean age of the patients at the time of the first operation was 72.9 years (range 63–79 years), and the mean duration between arthroplasties was 21.6 months (range 8–50 months). Patients were evaluated preoperatively and postoperatively at 2 weeks, 6 weeks, 3 months, 6 months, 1 year, and yearly with standardized clinical exams and outcome measures questionnaires including Constant, ASES, UCLA, Simple Shoulder Test, SPADI, and SF-12 scores.


Caleb Szubski Alison Klika Thomas Myers Jesse Schold Wael Barsoum

Introduction:

Over the last several decades, life expectancy following solid organ transplant (i.e. kidney, liver, heart, lung, and pancreas) has increased significantly, largely due to improvements in surgical technique, immunosuppressive regimens, patient selection, and postoperative care. As this population ages, many of these transplant patients become candidates for total knee arthroplasty (TKA). However, these patients may be at greater risk of complications following TKA due to immunosuppression and metabolic derangements secondary to organ dysfunction. The purpose of this study was to use a large, nationally representative database to compare morbidity, mortality, length of stay (LOS), and charges for TKA patients with and without a history of solid organ transplant.

Methods:

This retrospective study was a review of the Nationwide Inpatient Sample (NIS; the largest all-payer inpatient care United States database representing a 20% stratified sample) from 1998 to 2010. Patients who had a primary TKA (ICD-9-CM 81.54) were included (n = 5,706,675, weighted national frequency). A total of 763,924 cases were excluded for the following: age <18 years, pathologic fracture of lower extremity, malignant neoplasm and/or metastatic cancer, previous and/or bilateral arthroplasty, admission type other than “elective”. The remaining 4,942,751 patients were categorized as transplant (n = 5,245; included only liver, kidney, heart, lung and/or pancreas transplant) or non-transplant group (n = 4,931,017; no history of any transplant including solid organ or tissue). A multivariable regression model was used to identify any association(s) between a history of solid organ transplant and morbidity, mortality, LOS and hospital charges, while adjusting for patient and hospital characteristics.


Carmen Zietz Daniel Kluess Christian Fabry Felix Baum Wolfram Mittelmeier Rainer Bader

Current implant designs and materials provide a high grade of quality and safety, but aseptic implant loosening is still the main reason for total hip revision. Highly cross-linked polyethylene (HX-PE) is used successfully in total hip replacements (THR) since several years. The good wear properties lead to a reduction of wear debris and may contribute to a longer survival time of the THRs. Furthermore, thin HX-PE liner allows the use of larger femoral heads associated with a decreased risk of dislocation and an improved range of motion. However, the cross-linking process is associated with a loss of mechanical properties of the polyethylene material which compromise the use of thin HX-PE liner in terms of high stress situations.

The aim of the present study was the experimental wear analysis of HX-PE liner under steep acetabular cup position. Furthermore, a finite element analysis (FEA) was performed in order to calculate the stress within the HX-PE material in case of steep cup position under physiological loading.

Experimental wear testing was performed for 5 Mio load cycles, using highly cross-linked polyethylene (HX-PE) acetabular liner combined with 44 mm ceramic femoral heads at a standard position of the acetabular cup (30° inclination) according to ISO 14242 as well as at 60° cup inclination. The wall thickness of the HX-PE liner was 3.8 mm. A hip wear simulator, according to ISO 14242 (EndoLab GmbH, Rosenheim, Germany), was used and wear was determined gravimetrically. Moreover, finite element models of the THR system at standard and steep cup position was created by Abaqus/CAE (Dessault Systemes Providence, USA). Using the finite element software Abaqus (Dessault Systemes Providence, USA) the total hip implants were physiologically loaded with maximum force of the gait cycle (3.0 kN). Thereby, the stresses within the HX-PE material were analysed.

The average gravimetrical wear rates of the HX-PE liners at standard implant position (30°) and 60° cup inclination showed small wear amounts of 3.15 ± 0.32 mg and 1.92 ± 1.00 mg per million cycles, respectively. The FEA revealed a clear increase of stresses at the HX-PE liner with respect to steep cup position (von Mises stress of 8.78 MPa) compared to ISO standard implant position (von Mises stress of 5.70 MPa).

The wear simulator tests could not demonstrate significant differences of gravimetrical wear amount of HX-PE liners under steep hip cup position compared to standard implant position. The small contact surface between the femoral head and the SX-PE liner during the wear testing may lead to the low wear rate of the misaligned acetabluar cup. Moreover, the FEA showed that the effect of a misaligned acetabular cup on the stresses within the polyethylene liner can be critical. Although an increase of wear could not be detected a steeper acetabular cup position using thin HX-PE liners should be avoided due to higher stresses preventing implant failure in clinical application.


Daniel Kluess Catherine Ruther Carolin Gabler Wolfram Mittelmeier Rainer Bader

Clinically applied methods of assessing implant fixation and implant loosening are of sub-optimal precision, leading to the risk of unsecure indication of revision surgery and late recognition of bone defects. Loosening diagnosis involving measuring the eigenfrequencies of implants has its roots in the field of dentistry. The changing of the eigenfrequencies of the implant-bone-system due to the loosening state can be measured as vibrations or structure-borne sound. In research, vibrometry was studied using an external shaker to excite the femur-stem-system of total hip replacements and to measure the resulting frequencies by integrated accelerometers or by ultrasound. Since proper excitation of implant components seems a major challenge in vibrometry, we developed a non-invasive method of internal excitation creating an acoustic source directly inside the implant.

In the concept proposed for clinical use, an oscillator is integrated in the implant, e.g. the femoral stem of a total hip replacement. The oscillator consists of a magnetic or magnetisable spherical body which is fixed on a flat steel spring and is excited electromagnetically by a coil placed outside the patient. The oscillator impinges inside the implant and excites this to vibrate in its eigenfrequency. The excitation within the bending modes of the implant leads to a sound emission to the surrounding bone and soft tissue. The sound waves are detected by an acoustic sensor which is applied on the patient's skin. Differences in the signal generated result from varying level of implant fixation.

The sensor principle was tested in porcine foreleg specimens with a custom-made implant. Influence of the measurement location at the porcine skin and different levels of fixation were investigated (press-fit, slight loosening, advanced loosening) and compared to the pull-out strength of the implant. Evaluation of different parameters, especially the frequency spectrum resulted in differences of up to 12% for the comparison between press-fit and slight loosening, and 30% between press-fit and advanced loosening. A significant correlation between the measured frequency and the pull-out strength for different levels of fixation was found.

Based on these findings, an animal study with sensor-equipped bone implants was initiated using a rabbit model. The implants comprised an octagonal cross-section and were implanted into a circular drill hole at the distal femur. Thereby, definite gaps were realized between bone and implant initially. After implantation, the bone growth around the implant started and the gaps were successively closed over postoperative period. Consequently, since the tests had been started with a loose implant followed by its bony integration, a reverse loosening situation was simulated. In weekly measurements of the eigenfrequencies using the excitation and sensor system, the acoustic signals were followed up. Finally, after periods of 4 and 12 weeks after implantation, the animals were sacrificed and pull-out tests of the implants were performed to measure the implant fixation. The measured implant fixation strengths at the endpoint of each animal trial were correlated with the acoustic signals recorded.


Stefan W Kreuzer Scott Banks Toshifumi Watanabe Amir Pourmoghaddam

Background

Discrepancies in patient outcomes after total knee arthroplasty have encouraged the development of different treatment options including early preventive interventions. In addition, improvements in surgical techniques and instrumentation have increased the accuracy of the surgeries. In this case study, we review the first robotic-arm assisted modular tricompartmental knee arthroplasty in which bone and soft tissues are conserved by employing a precise planning and execution technique.

Materials and Methods

A 63 year old Caucasian female with a Body Mass Index (BMI) of 27 presented to the surgeon (SK) with knee pain and a varus mechanical alignment. The patient received modular tri-unicompartmental arthroplasty performed with robotic-arm assistance; (see figure 1 for post-op radiograph). Range of Motion (ROM), Knee Society Score (KSS) and Knee Injury and Osteoarthritis Outcomes Score (KOOS) were measured pre-operatively and post-operatively at 6, 16, and 23 months. At 6 months post-op an in-depth in vivo kinematic analysis was conducted by using a validated fluoroscopic assessment technique [1]. The patient simulated stair climbing, kneeling activity, and deep lunge while under single plane fluoroscopy. Three dimensional models were created from CT scans and were matched to 2D fluoroscopic images for kinematic assessment.


Amir Pourmoghaddam Stefan W Kreuzer Adam Freedhand

INTRODUCTION:

Proximally coated femoral stems have been designed to address the shortcomings of fully coated femoral stems including proximal femoral stress shielding. The design improvements leading to more optimized proximal femoral loading condition in the “Neck preserving stems” have increased the popularity of such implants (e.g., Minihip). Neck preserving stems depict better biological outcomes compared to more traditional stems 1 by utilizing more natural mechanical stress/strain distribution over the femur. These stems provide significant reduction in both torsional and bending moments at the stem/bone interface. This reduction may result in decreasing the micromotion and failure of osseointegration 1. Figure 1 demonstrates the differences between the cutting areas of a neck preserving versus traditional stem. The Minihip stem demonstrate a curved structure that is designed to match the shape of the femoral neck. The stability of the implant is achieved in the femoral neck and intertrochanteric area of the proximal femur. Further investigations are needed to establish a solid ground for the outcome of these stem in total hip arthroplasty (THA).

OBJECTIVES:

The current study was conducted to report the short-term clinical outcome of the THA by using Minihip neck preserving stem.


Michael Kurdziel Tristan Maerz Erin Baker Meagan Salisbury Lige Kaplan Kevin Baker

Introduction:

Unicompartmental knee arthroplasty (UKA) has been used in the past decades to treat progressive cartilage degeneration in a single compartment. Concern has been raised over the rate of revision procedures for polyethylene wear and osteoarthritic progression into the adjacent compartment. Few studies have examined the pathology of cartilage degeneration in the setting of UKA. This study aims to investigate the viability of knee chondrocytes introduced to high and low concentrations of orthopaedic wear debris particulate.

Methods:

Normal human articular chondrocytes (nHAC-Kn) were expanded in DMEM/F12 containing 10% FBS, 1% Penicillin/Streptomycin (Pen/Strp), and 50 μg/mL ascorbic acid (Asc). 24 hours prior to the start of the experiment, cells were seeded on 96-well plates at a density of 3500 cells/cm2 and exposed to DMEM/F12 containing 5% FBS, 1% Pen/Strp, and 50 μg/mL Asc. Particles (equivalent circle diameter range: 0.2–7 μm) at a low dose of 100: 1 (particles: cells) and high dose 1000: 1 (particles: cells) were introduced to treatment wells (n = 6). Control wells (n = 6) contained particles with no cells.

Treatment groups included high and low doses of TiAl6V4 alloy, 316L Stainless Steel, and Co-Cr-Mo alloy. At days 1, 3, 5, and 7, cells were assayed with a 3-(4,5-Dimethylthiazol-2-yl)-2,5-dyphenyltetrazolium bromide (MTT) assay for determination of cell viability. Light microscopy was performed at each timepoint to assess change in cell morphology.


Daniel MacDonald Steven Kurtz Sevi Kocagoz Josa Hanzlik Richard Underwood Jeremy Gilbert Gwo-Chin Lee Michael Mont Matthew Kraay Gregg Roger Klein Jay Parvizi Clare Rimnac

Background:

Previous studies regarding modular head-neck taper corrosion were largely based on cobalt chrome (CoCr) alloy femoral heads. Less is known about head-neck taper corrosion with ceramic femoral heads.

Questions/purposes:

We asked (1) whether ceramic heads resulted in less taper corrosion than CoCr heads; (2) what device and patient factors influence taper fretting corrosion; and (3) whether the mechanism of taper fretting corrosion in ceramic heads differs from that in CoCr heads.


Sharat Kusuma Zachary Goodman Kate C. Sheridan Ray Wasielewski

INTRODUCTION:

Recent trends in total hip arthroplasty (THA) have resulted in the use of larger acetabular components to achieve larger femoral head sizes to reduce dislocation, and improve range of motion and stability. Such practices can result in significant acetabular bone loss at the time of index THA, increasing risk of anterior/posterior wall compromise, reducing component coverage, component fixation, ingrowth surface and bone stock for future revision surgery. We report here on the effects of increasing acetabular reaming on component coverage and bone loss in a radiographic CT scan based computer model system.

METHODS:

A total of 74 normal cadaveric pelves with nonarthritic hip joints underwent thin slice CT scan followed by upload of these scans into the FDA approved radiographic analysis software. Utilizing this software package, baseline three-dimensional calculations of femoral head size and acetabular size were obtained. The software was used to produce a CT scan based model that would simulate reaming and placement of acetabular components in these pelves that were 125, 133 and 150% the size of the native femoral head. Calculations were made of cross sectional area bone loss from anterior/posterior columns, and loss of component coverage with increasing size.


Sharat Kusuma Dane Hansen

Introduction

Medial unicompartmental knee arthroplasty (UKA) for isolated medial knee arthritis is a highly successful and efficacious procedure. However, UKA is technically more challenging than total knee arthroplasty (TKA). Research has shown that surgical technical errors may lead to high early failure rates. Haptic robotic systems have recently been developed with the goal of improving accuracy, reducing complications, and improving overall outcomes. There is little research comparing robotic-assisted UKA to standard UKA. The goal of this study was to compare clinical and radiographic data for matched cohorts who received robotic-arm assisted UKA or standard instrumentation UKA.

Methods

We performed a non-randomized, retrospective review of 30 robotic-arm assisted UKA and 32 manual UKA performed by single fellowship-trained joint arthroplasty surgeon (SKK) over 2.5 years. All procedures completed through a medial parapatellar approach. All components were cemented. All tibial components were a metal-backed onlay design. Average follow-up was 10.1 months (range 5–36). A full clinical/hospital chart review of demographic, intra- and post-operative measures was performed. Radiographic analysis of pre- and post-op images evaluating sagital and coronal alignment, and component positioning was performed by single observer (DCH), using OsiriX imaging system (Pixmeo; Geneva, Switzerland). Radiographs were available for analysis in 28 robotic-assisted and 30 manual patients. Statistical analysis was performed using SPSS v. 20. Comparison between group means was performed as well as calculation of variance in component placement within groups.


Oh Soo Kwon Jin Ho Lee Se Heng Oh

Background

Antibiotic-loaded cement has been used over decades as a local antibiotic delivery for the treatment of bone and joint infections. However, there were some disadvantages such as unpredictable elution, insufficient local concentration and reduced mechanical strength. We developed hydrophilized bone cement and investigated whether it can improve consistent antibiotic release for extended periods to be effective in eradicating joint infection without any changes of mechanical strength.

Methods

The experiments consists of preparation of the hydrophilized, vancomycin-loaded bone cement, In vitro test including drug release behavior, mechanical properties by compression test, cytotoxicity, antibacterial effect and animal study. In animal study, Antibiotic cement rod was implanted in the femur of rat osteomyelitis model. Sign of infections were assessed by gross observation, Micro CT and blood analysis at indicated period.


Bethany Larsen Marc Jacofsky David Jacofsky Brian Onstot

Introduction:

This study evaluates the impact of radii-related differences in posterior cruciate ligament retaining (PCR) primary total knee arthroplasty (TKA) prosthetic designs on knee biomechanics during level walking 1-year after surgery. The multi-radius (MR) design creates at least two instantaneous flexion axes by changing the radius of curvature of the femoral component throughout the arc of knee motion. The femoral component of the single-radius (SR) design has only one radius and therefore a fixed axis.

Methods:

Subjects scheduled for computer-navigated TKA (n = 37: SR n = 20 [9M, 11F], MR n = 17 [8M, 9F]; 69.8 ± 7.1 years, 87.6 ± 20.8 kg, 1.68 ± 0.09 m), and demographic-matched controls without knee pathology n = 23 [13M, 10F], provided informed consent under the Banner IRB (Sun Health panel). All surgical subjects received similar pre-, peri-, and post-operative care under the direction of three surgeons from a single orthopedic practice. Position and force data were collected using 28 reflective markers (modified Helen Hayes [Kadaba et al 1990]) tracked by ten digital IR cameras (120 Hz) (Motion Analysis Corp., Santa Rosa, CA) and four force platforms (1200 Hz) (AMTI, Watertown, MA) embedded in an 8m walkway. Data were recorded and smoothed (Butterworth filter, 6 Hz) using EVaRT 5.0.4 software (Motion Analysis Corp.). Gait cycle parameters were calculated using the ‘Functional Hip Center’ and ‘Original Knee Axis’ models in Orthotrak 6.6.1 (Motion Analysis Corp.). Data from each group were height and weight normalized and ensemble averaged by affected limb (right limb for controls) using custom code written in Labview (National Instruments Corp, Austin, TX). Descriptive statistics for the maximum and minimum knee kinematic, kinetic, and temporal spatial values in the stance and swing phases of the gait cycle were generated for each group. Between-group comparisons were made using an ANOVA with post hoc testing as appropriate (SPSS 14.0 (SPSS Inc, Chicago, IL)).


Full Access
Jeremy Latham Richard Cook Ben Bolland Sam Yasen

Background

Large diameter chrome cobalt modular heads in hip replacement surgery have caused one of the biggest challenges to face orthopaedic surgeons, manufacturers and regulators in a generation. Increasing numbers of retrieved implants offer the opportunity to look in detail at the modes of failure of these devices.

Methods

We have examined the mechanical behaviour of the head taper/trunnion using a variety of techniques including:

mechanical testing in a custom-made jig

3D nano-precision form profilometry (RedLux)

optical 3D microscopy with focus variation technology

electro-chemical testing.


Michael Lawrenchuk Lara Vigneron Sebastian DeBoodt

With the increasing use of 3D medical imaging, it is possible to analyze 3D patient anatomy to extract features, trends and population specific shape information. This is applied to the development of ‘standard implants’ targeted to specific population groups.

INTRODUCTION

Human beings are diverse in their physical makeup while implants are often designed based on some key measurements taken from the literature or a limited sampling of patient data. The different implant sizes are often scaled versions of the ‘average’ implant, although in reality, the shape of anatomy changes as a function of the size of patient. The implant designs are often developed based on a certain demographic and ethnicity and then, simply applied to others, which can result in poor design fitment [1]. Today, with the increasing use of 3D medical imaging (e.g. CT or MRI), it is possible to analyze 3D patient anatomy to extract features, trends and population specific shape information. This can be applied to the development of new ‘standard implants’ targeted to a specific population group [2].

PATIENTS & METHODS

Our population analysis was performed by creating a Statistical Shape Model (SSM) [3] of the dataset. In this study, 40 full Chinese cadaver femurs and 100 full Caucasian cadaver femurs were segmented from CT scans using Mimics®. Two different SSMs, specific to each population, were built using in-house software tools. These SSMs were validated using leave-one-out experiments, and then analyzed and compared in order to enhance the two population shape differences.


Ian Clarke Jean Yves Lazennec Adrien Brusson Michelle Burgett Thomas Donaldson

Controversy exists over the role of fretting-corrosion in modular junctions of large-diameter metal-on-metal (MOM) heads given the many design plus alloy mix-and-match variations. Overall data was also scant regarding a) fitting stem trunnions to head tapers, b) role of taper angles, c) role of smooth vs threaded trunnion junctions, d) role of head neck-lengths and e) role of head diameters. While the “12: 14” taper has been used with small CoCr heads for 40 years, we could not find retrieval analyses on this European ‘gold-standard’. We therefore selected 10 femoral stems with 28 mm modular heads for analysis (3–8 years follow-up). Unique to this study were the threaded taper profiles on both stems and heads (Fig. 1).

Six stems were cemented Ti6Al4V (Alize, FH-Orthopedics, France) with 12/14 taper angle defined as 5° 42′. These represented Ti64: CoCr combinations from 2 vendors. The other four were CoCr stems including the CoCrMo (Protasul-2) and CoNiCrMo (Protasul-10) alloys (cemented and HA-coated; Sulzer, Switzerland). These CoCr: CoCr combinations from one vendor had “12/14” stem-taper defined as 5° 38′. Anatomical positioning of Metasul heads (Sulzer, Switzerland) was identified by main-wear zone maps. Femoral heads were then bi-valved in horizontal plane for direct imaging by interferometry (WLI) and SEM. Visual corrosion mapping (3) was recorded digitally in 4 anatomical views. Quantitative analysis used 1 to 5 taper zones with 6-replicate measurements per zone (Fig. 1).

The WLI and SEM studies showed that non-contacting taper zones inside CoCr heads (Fig. 2) were threaded with pitch of 70 μm (PV: peak-valley depth = 5–7 μm). The non-contact zones on Sulzer stems had 130 μm pitch (PV = 4–8 μm) whereas Alize stems had 210 μm pitch (PV = 10–12 μm). Threads on both stem types were much coarser than CoCr heads; Ti64 stem threads were much coarser than CoCr stems. In contact zones, the Metasul threads had flattened (avg. roughness = 0.45 μm Ra). With CoCr stems there was little difference. Difference in pitch of stem-threads vs head-threads indicated there was no imprinting onto head tapers. Nor were there statistically significant differences evident in the contact zones along CoCr or Ti64 tapers. Small damaged areas (Fig. 3: arrows) may have been due to alternatively; initial machining, surgical impaction, in-vivo cold-welds, fretting, corrosion, or from surgical-removal. The as labeled “corrosion damage” was well within the “mild” grade for all implants.(3) Thus even with this considerable variety of design and material parameters, we were satisfied that these gold-standard taper junctions with threaded interfaces had performed very well with 28 mm MOM at 3–8 years follow-up.


Guoan Li Jing-Sheng Li Ali Hosseini Young-Min Kwon Harry E Rubash

Due to technology advancement, many studies have reported on in-vivo human knee kinematics recently (Dannis, 2005; Moro-oka, 2008; Tashman, 2003; Koo, 2008). This abstract summarized the joint kinematics during three motions usually seen in our daily living, i.e. gait, step-up (stair ascending) and single-legged lunge that was measured using a combined dual-fluoroscopic imaging system and MRI based modeling technique (Li, 2008). Cartilage contacts or condylar motion using transepicondylar axis (TEA)/geometric center axis (GCA) were used to describe the motion characters of the knee during these motions.

In the treadmill gait, the movement of the medial femoral condyle along the anteroposterior direction was significantly greater than that of the lateral femoral condyle during the stance phase using either TEA (9.7 ± 0.7 mm vs. 4.0 ± 1.7 mm, respectively; p < 0.01; Fig. 1A) or GCA (17.4 ± 2.0 mm vs. 7.4 ± 6.1 mm, respectively; p < 0.01; Fig. 1B). A “lateral-pivoting” of the knee was observed (Kozanek, 2009).

In the step-up motion, both medial and lateral contact points moved anteriorly on the tibial articular surfaces along the step-up motion path. The contact points on the medial and lateral tibial plateau moved anteriorly (13.5 ± 3.2 mm vs. 10.7 ± 5.0 mm, respectively; p > 0.05; Fig. 2A) with knee extension. Using the TEA (Fig. 2B), the femoral condylar motions presented a similar pattern as the contact points; nonetheless, using the GCA (Fig. 2C), the femoral condylar motion pattern was dramatically different. The medial condyle moved anteriorly, while the lateral condyle shifted posteriorly. However, none of them showed a significant pivoting phenomenon (Li, 2013).

In the single-legged lunge, both medial and lateral contact points moved similarly before 120° of knee flexion, but the lateral contact moved posteriorly and significantly more than the medial compartment in high flexion (1.9 ± 2.1 mm vs. 4.8 ± 2 mm, respectively; p < 0.05). The single-legged lunge didn't show a single motion pattern (Fig. 3) (Qi, 2013).

These data provide baseline knowledge for the understanding of normal physiological function of the knee during gait, step-up and lunge activities. The findings of these studies demonstrated that knee joint kinematics is activity-dependent and indicated that the knee joint motions could not be described using a single motion character such as “medial-pivoting” that has recently been popularized in total knee arthroplasty design areas.


Glen Zi Qiang Liau Mann Hong Tan

Introduction

Published literature that examined pre-operative Body Mass Index (BMI) with Total Knee Arthroplasty (TKA) outcomes have shown conflicting data. Some show that higher BMI and is associated with poorer post-TKA function and HRQoL outcomes, but not others.

The aim of our analyses is to identify the relationship of pre-operative obesity with the outcomes of TKA, including physical and mental functional limitations.

Methods

We performed a prospective analysis of a consecutive series of 191 patients, who had underwent TKA from March 2006 to February 2011, performed by a single surgeon, at Singapore General Hospital, Singapore. Patients were eligible if they had met the following criteria: primary, unilateral TKA, using fixed bearing, posterior stabilized prostheses, under computer assisted surgery system. Patients were reviewed clinically at 6 months and 2 years post-operatively.

Patients were stratified into non-obese (BMI <30 kg/m2), mildly obese (BMI 30 to 35) and highly obese (BMI ≥35) groups. Outcome measures evaluated include: SF-36, Oxford knee score and Knee Society Score.


Seung-Jae Lim Byung Ho Lim Keun Ho Lee Kyung Rae Ko Young-Wan Moon Youn-Soo Park

Introduction:

The outcome of previous cemented total hip arthroplasty has been reported to be inferior in renal transplant patients because of poor bone stock resulting from long-term steroid use. Moreover, as renal transplant patients remain on immunosuppressant therapy for life, higher levels of overall morbidity must be considered. We evaluated the mid-term results of cementless total hip arthroplasty in renal transplant recipients with osteonecrosis of the femoral head, and compared those with age and sex matched osteonecrosis patients that had not undergone organ transplantation or been treated with long-term steroid.

Materials & Methods:

Between October 1997 and October 2008, 45 consecutive primary cementless total hip arthroplasties were performed in 30 patients with advanced osteonecrosis of the femoral head after renal transplantation. There were 18 males (27 hips) and 12 females (18 hips) of overall mean age 44 years (22 to 68). The clinical and radiographic results of cementless total hip arthroplasty in these 45 hips were compared with those of 96 sex and age-matched osteonecrotic hips of 72 patients that had not undergone organ transplantation or long-term steroid use. Patients were evaluated at surgery and at a mean of 7.2 years (range, 2–13 years) postoperatively.


Jason Longaray Reginald Lee Lizeth Herrera Amber Schweitzer Aaron Essner

Burroughs et al showed that frictional torque increases with increasing head size in a simple in vitro model and showed differences in frictional torque with different polyethylene materials [1]. Therefore, the purpose of this study was to evaluate the influence of bearing material and bearing size on the frictional torque of hip bearings utilizing a more physiologically relevant hip simulator model.

A total of four hip bearing combinations (Crosslinked PE/CoCr, Conventional PE/CoCr, Crosslinked PE/Delta and Alumina /Alumina) with various bearing sizes were evaluated. The sizes tested in this study range from 22 mm to 44 mm; it is important to note that the study only evaluated bearing combinations (size and material combination) currently commercially available. A total of three samples per bearing combination were tested, with the exception of conventional PE, which included a total of 4 samples. A MTS hip joint simulator was used. All components were oriented anatomically with the femoral head mounted below on a rotating angled block which imparts a 23° biaxial rocking motion onto the head. Loading was held constant at each load level (500N, 1000N, 1500N, 2000N, 2450N) for at least two rotational cycles while all 3 axes of load and all 3 axes of moments were measured at 10 khz. Fresh Alpha Calf Fraction serum was utilized as a lubricant.

Results show that frictional torque increases with the increase of head size regardless of head material for all polyethylene combinations (p > 0.05), as shown in Figure 1 and 2. However, results showed no change in frictional behavior for the Alumina/Alumina combination regardless of the bearing size. The results of this test did not show any significant difference between crosslinked PE and conventional PE materials for sizes 28 mm and 32 mm when paired against a CoCr head (p > 0.05) (Figure 3). The Alumina/Alumina bearing combination had the lowest frictional torque among all the bearing material combinations evaluated in this study.

This data suggests that there is a strong correlation between increased head size and increased frictional torque (R2 = 0.6906, 0.8847) for the polyethylenes evaluated here regardless of head material. No correlation can be concluded for the Alumina /Alumina bearing combination (R2 = 0.0217). The combination of Alumina /Alumina seems to have the most favorable frictional properties. This data also suggests no effect on frictional properties regardless of the polyethylene material (crosslinked and conventional) for sizes 28 mm and 32 mm. The frictional torque values recorded in this study are different than those published by Burroughs et al [1]. This difference may be attributed to the testing methodology. The current study utilizes a hip simulator, which closely mimics the natural joint providing a more physiologically relevant model whereas the Burroughs et al study utilizes a single axis machine. It is important to understand that frictional behavior in hip bearings may be highly sensitive to bearing clearance, cup thickness, and stiffness, which may outweight the effect of head diameter. Further evaluation is necessary to isolate and investigate those parameters.


Thomas Luyckx Lucas Beckers William Colyn Johan Bellemans

Introduction

Several studies have described the relationship between the joint line and bony landmarks around the knee. However, high inter-patient variation makes these absolute values difficult in use.

This study was set up to validate the previously described distances and ratios on calibrated full limb standing X-rays and to investigate the accuracy and reliability of these ratios as a tool for joint line reconstruction

Methods:

One hundred calibrated full-leg standing radiographs obtained from healthy volunteers were reviewed (fig 1). Distances from the medial epicondyle, the lateral epicondyle, the adductor tubercle, the fibular head and the proximal center of the knee (CJD) to the virtual prosthetic joint line were determined (fig 3). This prosthetic joint line was created by introducing a virtual distal femoral cutting block with a valgus angle of 6° on the full-leg radiographs.

The adductor ratio was defined as the distance from adductor tubercle to the joint line divided by the femoral width.

The correlation with the femoral width, the CJD and the limb alignment was analysed using linear regression analysis. The accuracy and reliability of the use of the ratio of the distance of the adductor tubercle, the medial epicondyle and the CJD relative to the femoral width to reconstruct the joint line was calculated.


Shinichi Maeno Kenshi Sakayama Setsuya Kamei Seiji Saito Nobuyuki Fujita Masahiro Ishizaka Kazuki Kimura Kazuya Maeda Ko Onoda Kaori Sadakiyo Masaki Akutsu Toshiro Otani Ko Masumoto

Patients who have undergone Total Knee Replacement (TKR) improve their knee functions with time dependent recovery. However, the speed and degree of recovery widely varies from person to person. Practitioners generally find that postoperative satisfaction after TKR is closely related to the degree of preoperative severity in deformity. We focused on preoperative FTA to determine how the degree of deformity affects postoperative improvements after TKR.

Methods:

44 consecutive knees of 44 patients with medial osteoarthritis underwent TKR for nomination in this study. All operations were conducted by a single surgeon using a mid vastus approach with cemented posterior stabilized (PS) implant and patellar resurfacing. Patients were targeted for full weight bearing the next day.

Patients were divided into 3 groups of preoperative FTA: 174–180 degrees (11 knees), 181–189 degrees (17 knees), and more than 190 degrees (16 knees). Walking ability was assessed by gait speed and width of step. Balance was measured by a “Functional Reach Test (FR),” which is the difference between arm's length and maximal forward reach (Duncan PW et al. 1990), a “Timed Up and Go Test (TUG),” the time interval for a patient rise from an arm chair, walk 3 meters, and return (Podsiadlo and Richardson 1991), and the capacity to stand on one leg (one leg standing time trial). Every measurement was performed prior to the operation (pre-op), and 4 weeks after operation (post-op 4w). The recovery rate (%) was defined as post-op 4w/pre-op ×100. Data were analyzed by one-way ANOVA, and then differences among means were analyzed using Bonferroni procedures. P-values lower than 5% are regarded as significant.

Result:

The recovery rate of walking speed and TUG showed significant improvement in the FTA more than >190 degree group than that of 174–180 degree group. Every other result showed a higher recovery rate for the >190 degree group, although results were not statistically significant.


Alexander Chong Joshua M. Matthews David A. McQueen Justin D. O'Guinn Paul H. Wooley

INTRODUCTION:

A discrepancy exists between biomechanical and clinical outcome studies when comparing cruciate-retaining (CR) versus posterior stabilized (PS) component designs. The purpose of this study is to re-evaluate experimental model results using half-body specimens with intact extensor mechanisms and navigation to evaluate PS and CR component gaps though an entire range of motion.

METHODS:

A custom-designed knee testing apparatus was used for secure anchoring of the lower half of cadaver pelvic, allowing full range of knee motion and the application of traction throughout that range. Eight sequential testing regimens: were conducted with knee intact, with CR TKA in place, with PS TKA with quadriceps tendon in place, with PS TKA with sectioned quadriceps tendon in place, with and without traction at each stage. At each stage, a navigated knee system with dedicated software was used to record component gapping through a full range of motion from 0° to 120°. The amount of traction used was 22N. Each knee (n = 10) was taken through 6 full ranges of motion at every stage. At each stage, corroboration of navigation findings was attempted using a modified gap balancer to take static gap measurements at 0° and 90° with 12 in. lbs of torque was applied.


Morteza Meftah Hollis Potter Amar Ranawat Chitranjan S Ranawat

Introduction:

The earliest evidence of particle-induced response is found in the synovium, leading to osteolytic defect. The degree of synovitis can be quantified by magnetic resonance imaging (MRI). This is the first long-term, prospective, matched-pair study using MRI to analyze wear-induced synovitis and osteolysis between rotating-platform posterior-stabilized (RP-PS), fixed-bearing metal-back (FB-MB), and all-polyethylene tibial (APT) designs in active patients with identical femoral components and polyethylene.

Methods:

From September 1999 to October 2001, a matched-pair analysis of 24 TKAs (18 patients, 3 groups: 8 RP-PS, 8 FB-MB, and 8 APT) was performed. TKAs were matched for age, sex, body mass index (BMI), and University of California Los Angeles (UCLA) activity scores. All patients underwent MRI using MAVRIC (multi-acquisition variable-resonance image combination) knee protocol designed to reduce metal susceptibility artifact. Images were evaluated for volumetric measure of synovitis and/or osteolysis and presence of fibrous membrane formation at the cement-bone interface.


Morteza Meftah Amar Ranawat Chitranjan S Ranawat

Introduction:

Proper component orientation and soft tissue balancing are essential for longevity of total knee arthroplasty (TKA), especially in young and active patients. The aim of this study was to evaluate long-term results and quality of TKA in young and active patients with extension first gap balancing technique, in 2 Posterior-Stabilized (PS) total knee designs with identical femoral component.

Material and Methods:

43 consecutive Rotating-Platform (RP-PS, 33 patients) and 38 Fixed-Bearing (FB-PS, 29 patients) with University of California Los Angeles (UCLA) activity score of 5 or above and mean age was 53 ± 1.5 years were followed prospectively for a minimum of 10 years. 18 random TKAs were analyzed for component rotation using MRI.


Vivek Mohan Robert Namba Dhiren Sheth Liz Paxton Maria Inacio

Background and Purpose:

Modularity of the tibial component in total knee arthroplasties (TKA) has many surgical benefits. It also reduces inventory related expenses but increases implant cost. The resulting locking mechanism micromotion that leads to non-articular microwear and has been an accepted consequence of modularity. The purpose of this study is to evaluate the risk of revision (all-cause and aseptic) of a monoblock all-polyethylene tibial component compared to a fixed bearing modular tibial construct with the same articular geometry while adjusting for potential confounders in a community based sample of primary TKAs. In addition, younger and older patient specific risk of revision was evaluated.

Method:

A retrospective analysis of prospectively collected data from a Total Joint Replacement Registry (TJRR) was conducted. All 27,657 primary TKAs enrolled between 2001 and 2010 performed for any diagnosis with the same implant from a single manufacturer were included in the study. Patient characteristics, as well as surgeon, hospital, procedure, and implant characteristics were compared by the main exposure of interest, i.e. the type of tibial prosthesis (monoblock all-polyethylene vs. metal-backed modular). The main endpoints of the study were all-cause and aseptic revisions only. Descriptive statistics and Cox-regression models were employed. Hazard ratios (HR) and 95% confidence intervals (CI) are provided.


Young-Wan Moon Hyungtae Lim Kyung Rae Ko Keun Ho Lee Sangyeon So Jai-Gon Seo

Background:

The safety implications of achieving high flexion after TKA and the use of high flexion prostheses remain issues of concern. It is possible that different designs have different clinical and radiological results and complications, such as, early aseptic loosening. However, little information is available on the clinical results of TKAs performed using single-radius, high-flex posterior stabilized design. Accordingly, this study was undertaken to document results of single-radius, high-flex posterior stabilized TKAs with minimum 7-year follow-up.

Methods:

From April 2003 to February 2006, 308 patients (455 knees) underwent TKA using single-radius, high-flex posterior stabilized design and among those patients, 251 patients (388 knees) included in this study who were able to be followed up for a minimum 7 year. Clinical results were evaluated using Knee Society Knee scores (KSKS) and Knee Society Function scores (KSFS) at last follow-up. The passive knee flexion was measured using a goniometer before and after surgery. The survival rate of the implants and implant-specific complications such as osteolysis or loosening were investigated. The osteolysis or loosening around the components was recorded according to the Knee Society Radiological scoring System.


Syam Morapudi Yousef Khan Rui Zhou Keith Barnes

Introduction:

Infection as an indication for revision has increased to 12% of the total revisions (UK NJR 9th report). However, it is next to impossible to find out the cause for a delayed prosthetic infection. With increasing number of arthroplasty procedures, is there a need for prophylactic antibiotics in patients with prostheses?

Methods:

At London Knee Meeting 2012, a total of 163 surgeons were asked to take part in a survey. This was to find out if they knew of any existing guidelines for prophylaxis for dental procedures, if there was a need to practice more uniformly, and if they recommend such prophylaxis to their patients routinely. The grade of the surgeon and their experience in years was also noted.


Syam Morapudi

Introduction:

The clinical significance of serum metal ion levels alone in patients with stemmed MoM hip arthroplasty remains uncertain. This study aims to measure the metal ion levels in patients with unilateral and bilateral hip arthroplasty to see whether or not the patients with bilateral hips have higher metal ions.

Patients and Methods

All the patients with bilateral MoM hip arthroplasty were identified from the research database. These patients were then matched with those in a similar age group who had a unilateral hip arthroplasty, but same University of California Los Angeles (UCLA) activity score. The UCLA activity scores along with other hip scores have been previously gathered for all the patients. Both sets of patients then had measurement of serum cobalt and chromium levels. The results were analyzed and compared.


James Murphy Paul Courtney Gwo-Chin Lee

Proper restoration of posterior condylar offset during TKA has been shown to be important to maximize range of motion and minimize flexion instability. However, there is little information as to the importance of restoration of mid-sagittal femoral geometry. There is controversy as to whether a TKA prosthesis should have a single radius or multiple radii of curvature. The purpose of this study is to evaluate the effectiveness of a multi-radius femoral component at restoring mid sagittal femoral offset.

A consecutive series of 100 TKAs with digital preoperative and postoperative radiographs and standardized radiographic markers were analyzed. There were 71 female and 29 male knees with mean age of 59 years. All TKAs were performed by a single surgeon using a multi-radius femoral component design. The distal femoral resection was set to resect 10 mm from the distal femoral condyle and a posterior referencing system was used to size the femoral component. Using radiographic perfect lateral projections of the knees, a line was drawn along the posterior femoral shaft and another parallel line down the anterior femoral shaft. A 3rd line was then drawn parallel to the posterior shaft at the furthest point posterior on the condyle. A 4th line was drawn parallel to the anterior shaft at the furthest point anterior on the femur. 90 degree angles were constructed to create a grid in the anterior and posterior directions, similar to a previously reported technique. Finally, 45 degree angle lines were created in the grid to assess mid flexion dimensions [Fig-1 and 2]. The percent change in posterior condylar offset (PCO), anterior femoral offset (AFO), mid femoral anterior offset (MAFO) and mid femoral posterior offset (MFPO) were calculated.

The mean reproduction of the mid-anterior femoral offset and mid-posterior femoral offset were 101.1% [range 56.5%–167.5%] and 96.8% [range 54.9%–149.0%] of preoperative measurements respectively. The average restoration of posterior offset and anterior offset were 92.8% [range 49.0%–129.8%] and 115.3% of preoperative measurements [range 35.7%–400.0%] respectively. When the posterior condylar offset was restored to within 10% of the native anatomy, the MPFO restoration more closely resembled normal anatomy (103.0% vs. 93.9%, p = 0.005). When the postoperative posterior condylar offset was decreased greater than 20%, both the MAFO (90.1% vs. 104.5%, p = 0.004) and MPFO (78.5% vs. 102.9%, p < 0.001) decreased compared to the native knee. There was no relationship between restoration of the PCO and the MAFO correction (104.6% vs. 99.4%, p = 0.213). Finally, there was no correlation between restoration of anterior femoral offset within 10% of normal and the restoration of mid sagittal femoral offset; 98.0% vs 102.0% for MAFO (p = 0.320) and 98.7% vs 96.3% for MPFO (p = 0.569).

A modern multi-radius condylar knee design is capable of reproducing the mid-sagittal geometry of the preoperative knee. However, the restoration of mid sagittal offset is largely dependent on the restoration of the posterior condylar offset. Intraoperative adjustments in anterior and posterior femoral resections can have significant impact in the ability of the implant to reproduce mid-sagittal femoral anatomy.


Stephen Murphy William Murphy S. Douglas Werner Jens H. Kowal

Introduction:

Wear, wear-associated osteolysis, and instability are the most common reasons for revision total hip arthroplasty. These failures have been shown to be associated with acetabular component malpositioning. However, optimal acetabular component orientation on a patient-specific basis is currently unknown. The current study uses CT to assess acetabular orientation in a group of unstable hips as compared to a control group of stable hips.

Methods:

Our institutional database of CT studies performed in the region of the hip beginning in February of 1998 (41,975 CT studies) was compared against our institutional database of revision total hip arthroplasties beginning in August of 2003 (2262 Revision THA) to identify CT studies of any hip treated for recurrent instability by revision of the acetabular component. Twenty hips in 20 patients with suitable CT studies were identified for the study group. Our control group consisted of 99 hips in 93 patients who had CT studies either for computer-assisted surgery on the contralateral side or for assessment of osteolysis. Using the CT data, the AP plane (APP) was defined, supine pelvic tilt was measured, and cup orientation was calculated by fitting a best fit plane to 6 points on the rim of the acetabular component. Cup orientation was calculated in degrees of operative anteversion and operative inclination according to the definitions of Murray. Both absolute cup position relative to the APP and tilt-adjusted cup position1 were calculated.


Jan Nadorf Marc Thomsen Robert Sonntag Joern Reinders J. Philippe Kretzer

INTRODUCTION:

Good survival rates of cementless hip stems serve as motivation for further development, just like modular implant systems or short stems. New aims are worth striving for, e.g. soft tissue or bone sparing options with similar survival rates in case of short stems. Even minimal design modifications might result in complications, e.g. missing osseointegration, loosening of the implant or painful stem, as shown in the past.

One of these developments is the Biomet – GTS™ stem [Fig. 1], a hybrid between conventional cementless straight stem and potentially sparing short stem.

Aim of this biomechanical study was to analyze, if the biomechanical behavior of the stem is comparable to a clinically proofed design with respect to the stem fixation in the bone and to the mechanical behavior of the stem itself. That's why the primary stability of the GTS™ stem has been determined and subsequently was compared to the Zimmer – CLS® stem.

MATERIAL & METHODS

Four GTS™ stems and four CLS® stems were implanted standardized in eight synthetic femurs. Micromotions of the stem and the bone were measured at different sites. A high precision measuring device was used to apply two different cyclic load situations: 1. Axial torque of +/−7 Nm around the longitudinal stem axis to determine the rotational implant stability. 2. Varus-valgus-torque of +/−3, 5 Nm to determine the bending behavior of the stem. Comparing the motions of the stem and femur at different sites allowed the calculation of relative micromotions at the bone-implant-interface.


Jan Nadorf Jan Dennis Graage J. Philippe Kretzer Eike Jakubowitz Stefan Kinkel

Introduction:

Extensive bone defects of the proximal femur e.g. due to aseptic loosening might require the implantation of megaprostheses. In the literature high loosening rates of such megaprostheses have been reported. However, different fixation methods have been developed to achieve adequate implant stability, which is reflected by differing design characteristics of the commonly used implants. Yet, a biomechanical comparison of these designs has not been reported.

The aim of our study was to analyse potential differences in the biomechanical behaviour of three megaprostheses with different designs by measuring the primary rotational stability in vitro.

Methods:

Four different stem designs [Group A: Megasystem-C® (Link), Group B: MUTARS®(Implantcast), Group C: GMRS™ (Stryker) and Group D: Segmental System (Zimmer); see Fig. 1] were implanted into 16 Sawbones® after generating a segmental AAOS Typ 2 defect.

Using an established method to analyse the rotational stability, a cyclic axial torque of ± 7.0 Nm along the longitudinal stem axis was applied. Micromotions were measured at defined levels of the bone and the implant [Fig. 2]. The calculation of relative micromotions at the bone-implant interface allowed classifying the rotational implant stability.


Denis Nam Elizabeth Cody Joseph Nguyen Mark P. Figgie David J. Mayman

Background:

Conventional, extramedullary (EM) tibial alignment guides are only 65%–88% accurate in creating a tibial resection within 2° of perpendicular to the tibial mechanical axis in total knee arthroplasty (TKA). The purpose of this study was to compare the overall, tibial component alignment, and the surgeon's ability to achieve a specific, intraoperative goal for alignment between a portable, navigation system (KneeAlign™) and conventional, EM alignment guides.

Methods:

One hundred patients were enrolled in a prospective, randomized controlled study. Fifty patients received a TKA using the KneeAlign™ to perform the tibial resection, and 50 patients an EM alignment guide. Standing AP hip-to-ankle radiographs and lateral knee-to-ankle radiographs were obtained at the first, postoperative visit.


Denis Nam Patrick Maher Amar Ranawat Douglas E Padgett David J. Mayman

Background:

Numerous studies have reported the importance of acetabular component positioning in decreasing dislocation rates, the risk of liner fractures, and bearing surface wear in total hip arthroplasty (THA). The goal of improving acetabular component positioning has led to the development of computer-assisted surgical (CAS) techniques, and several studies have demonstrated improved results when compared to conventional, freehand methods. Recently, a computed tomography (CT)-based robotic surgery system has been developed (MAKO™ Robotic Arm Interactive Orthopaedic System, MAKO Surgical Corp., Fort Lauderdale, FLA, USA), with promising improvements in component alignment and surgical precision. The purpose of this study was to compare the accuracy in predicting the postoperative acetabular component position between the MAKO™ robotic navigation system and an imageless, CAS system (AchieveCAS, Smith and Nephew Inc., Memphis, TN, USA).

Materials and Methods:

30 THAs performed using the robotic navigation system (robotic cohort) were available for review, and compared to the most recent 30 THAs performed using the imageless, CAS system (CAS cohort). The final, intraoperative reading for acetabular abduction and anteversion provided by each navigation system was recorded following each THA. Einsel-Bild-Roentgen analysis was used to measure the acetabular component abduction and anteversion based on anteroposterior pelvis radiographs obtained at each patient's first, postoperative visit (Figure 1). Two observers, blinded to the treatment arms, independently measured all the acetabular components, and the results were assessed for inter-observer reliability.

Comparing the difference between the final, intraoperative reading for both acetabular abduction and anteversion, and the radiographic alignment calculated using EBRA analysis, allowed assessment of the intraoperative predictive capability of each system, and accuracy in determining the postoperative acetabular component position. In addition, the number of acetabular components outside of the “safe zone” (40° + 10° of abduction, 15° + 10° of anteversion), as described by Lewinnek et al., was assessed. Lastly, the operative time for each surgery was recorded.


Diana Nguyen Michelle Burgett Thomas Halim Thomas Donaldson Ian Clarke

There is a consensus that impingement, subluxation, and dislocation are major risks that can lead to failure in total hip arthroplasty (1). As well as producing edge-wear, such clinical events also may create additional loads of particulate debris (2). It has been suggested that the release of metal debris with collateral damage on metal-on-metal (MOM) bearings creates a particularly severe abrasive wear, hitherto not understood, and recently termed ‘micro-grooving’ (3,4). Perhaps related to this micro-grooving, large surface depressions have also been observed. These we labeled ‘Dongas’, from the South African term for a steep-sided gully created by erosion. The goal of this study was to examine Dongas found on retrieved MOM bearings and to correlate factors such as cause of revision, MOM diameter and Donga locations with respect to regions of normal and stripe wear. Our hypotheses were: (1) Dongas will be most visible in non-wear zones (NWZ) adjacent to the main-wear zone boundary (MWZ), (2) the 28 mm MOM, being inherently less stable compared to large-diameter MOM, will show a higher Donga frequency and (3) patients with subluxation or dislocation complaints will reveal a higher Donga frequency.

Five cases with 28 mm MOM, five of 34–38 mm, and five of 50–56 mm diameter were studied (N = 15). The MWZ was measured in each MOM head and the number of NWZ and MWZ Dongas recorded. Bearing damage was examined using a white-light interferometer (Zygo; 5x lens).

Dongas were mainly elliptical in shape, but sometimes highly irregular. They were commonly circumscribed by raised lips (Fig. 1). Donga “trails” were also found, appearing as a linear series of similar-sized Dongas (Fig. 2). Donga trails exhibited some variability with raised lips either lining only the opposite sides or circumscribing most of the perimeter. The Dongas were commonly found in NWZ, with less than 20% found in MWZ. For this set of 15 MOM bearings, large-diameter bearings showed the largest number of Dongas and the greatest frequency of Dongas resulted from either loose or migrating cups.

The high occurrence of dongas in the non-wear zone (supporting hypothesis-1) may be a result of particles swept into the bearing interface (2,5). The size of the Dongas and their frequent association to local micro-grooves indicated that these were the impact sites of circulating particles. Such large surface depressions (40–200 μm) have not been described previously and may be unique to MOM bearings (3,4). The observation that Dongas were most prevalent in cases with loose or migrating cups left hypothesis-2 unsatisfied. The much higher incidence of Dongas in the large-diameter MOM was surprising and negated hypothesis-3. Overall these new data relating Dongas and micro-grooves gives new credence to a hitherto unsuspected 3rd-body abrasive wear mechanism due to repetitive subluxation or impingement.


Philip Noble Rikin Patel Kashif Ashfaq Derek Bernstein Sabir Ismaily Stephen Incavo

Introduction

After TKR, excessive tension within the lateral retinaculum can lead to joint instability, component wear, stiffness and pain. The spatial distribution of strain in the lateral retinculum is unknown, both in the native knee and after TKR. In this study we measure the magnitude and distribution of mechanical strain in the lateral retinaculum with knee flexion, both in the native knee and after TKR. We hypothesize that:

Strain in the lateral retinaculum will increase as a function of flexion.

Some regions of the lateral retinaculum experience greater strain than others.

TKR will affect the magnitude and location of strain during knee flexion.

Materials and Methods

A fiduciary grid of approximately 40–70 markers was attached to the exposed lateral retinacula of five fresh frozen cadaveric knees in order to allow tracking of soft-tissue deformation. Each knee was flexed from 0–120° in a 6 degree-of-freedom custom activity simulator that physiologically loaded the knee during a squatting maneuver. During simulation, the displacement of each fiduciary point was measured using visible-light stereo-photogrammetry. The fiduciary grid divided into four distinct regions for strain analysis. Using the grid of the native knee in full extension as the initial state, the average principal strain in each region was calculated as a function of flexion. Measurements were repeated after TKR was performed using a contemporary implant system.


Philip Noble Maureen Dwyer Hugh Jones Richard E Field Joseph C McCarthy

Introduction:

The sealing function of the acetabular labrum is central to the stability of the hip and the health of the joint. Disruption of the labrum has been shown to reduce intra-articular pressure and increase the rate of cartilage consolidation during static loading. Functional activities require movement of the hip through wide ranges of joint motion which disrupt joint congruency, and thus may alter the seal. This study was performed to test the hypothesis that the sealing function of the labrum varies with the position of the hip during functional activities.

Methods:

Six fresh cadaveric hip joint specimens were obtained from donors of average age 45.5 ± 16.1 years (range 25–63 years). Each specimen was dissected free of soft tissue, leaving the capsule and labrum intact, potted in mounting fixtures, and placed in a loading apparatus. Catheters were inserted into the central and peripheral compartments of each hip to allow infusion of fluid and monitoring of compartment pressures via miniature transducers (OMEGA Engineering, Inc). After application of a joint load of 0.50 BW, fluid was introduced into the central compartment at a constant rate until transport was indicated by a rise in pressure within the peripheral compartment. These measurements were performed with each hip placed in 10 functional positions ranging from −5 to 105 degrees of flexion, −5 to 13 degrees of abduction, and −25 to 35 degrees of external rotation simulating the sequential stages of gait, stooping, and pivoting. Motion analysis was performed via reflective marker arrays attached to the femur and pelvis to allow computer visualization of the position of the pelvis and femur using CT reconstructions. In each hip position, we measured the peak pressure (kPA) developed within the central compartment prior to fluid transfer to the peripheral compartment.


Iustin Moga Melvyn Augustus Harrington Sabir Ismaily Philip Noble

Introduction

The failure rate of Total Hip Replacement (THR) has been shown to be strongly influenced by the nature of the articulating interfaces, with Metal-on-Metal (MoM) articulations having three times the failure rate of Metal-on-Polyethylene (MoP) components. It has been postulated that this observation is related to edge wear and increased bearing torque of large MoM heads, which would lead to increased loading and wear at the head taper junction and, subsequently, to the release of metal ions and corrosion products. This suggests that taper wear and corrosion should not be as prevalent in large head MoP implants as in large head MoM implants. This study was undertaken to test the hypotheses that: (i) MoM implants exhibit higher rates of corrosion and fretting at the head taper junction than MoP implants, and that (ii) the severity of corrosion and fretting is greater in components of larger head diameter.

Materials and Methods

Our study included 90 modular implants (41 MoM; 49 MoP) retrieved during revision hip arthroplasties performed between 1992 and 2012. Only retrievals with head diameters greater than 32 mm were included, and trunnion sizes ranged from 10/12 mm to 14/16 mm with 12/14 mm being the most common size. The stem trunnion and head taper surfaces were examined under stereomicroscope by a single observer. Each surface was scored for both corrosion (using a modified Goldberg scoring system) and fretting (using the standard Goldberg scoring system). For both the trunnion and head tapers, the student's t-test was used to determine if differences exist in the severity of corrosion or fretting between the MoM and MoP groups and between different head sizes of the same articulation type.


Philip Noble Christopher Noel

Background:

The use of registry data to detect and eliminate inferior devices is based on the assumption that the results of the first cases performed with a new device are indicative of how the same implant would perform with widespread usage. However, existing registry data clearly proves that the performance of individual implants is very surgeon dependent. In this study we utilized a computer simulation of a large implant registry to address the question: How does the pairing of different surgeons with different implants affect the ability of registries to correctly identify inferior devices?

Materials and Methods:

A synthetic implant registry was created consisting of 10,000 patients who underwent joint replacement performed by 100 different surgeons using 5 different implants. Hazard functions representing the relative risks for revision associated with individual patients and surgeons were derived from the annual reports of implant registries. The cumulative revision rates (CRR values) of the 5 hypothetical implants were fixed at nominal values of 10%, 15%, 20%, 25%, and 30% at 15 years post operation vs. 10% for average implants. The surgeons were ordered according to their individual probabilities of a revision at less than 15 years post-op. Each surgeon was placed in one of 8 subsets comprised of 12.5% of the total surgeon pool, ranging from the lowest to the highest risk of revision. Patients, surgeons, and implants were randomly matched in an iterative fashion to simulate 500 separate RCTs, starting with the group of surgeons of with the lowest risk, and then repeating the simulation using surgeons with the lowest and second lowest risk of revision. This process was repeated iteratively until all surgeons were enrolled.


Jerry Alexander Adam Hexter Sabir Ismaily Alister Hart Philip Noble

Introduction

Tribo-chemical damage of modular taper junctions is often observed at revision THR and may be a contributing factor to chronic inflammation of peri-prosthetic tissues through generation of chromium rich corrosion products. At the time of revision, surgeons may elect to leave the primary femoral stem in situ and replace the original femoral head with a new component. This decision is based on the assumption that the interface formed between the original trunnion and the new bore is capable of withstanding the loads and torques applied during use, without failure of the new interface. This study was performed to determine the extent to which the mechanical properties of the taper interface are degraded with varying degrees of tribo-chemical damage secondary to prior implantation.

Materials and Methods

Fifteen CoCr femoral heads (DePuy: 6, Smith & Nephew: 5; Zimmer: 4) were retrieved at revision THR and were examined with stereomicroscopy. The surface of each bore was scored for the presence of fretting and corrosion using the grading system of Goldberg et al. Nine additional heads in original (unimplanted) condition (3 per manufacturer) were also selected to act as controls. Each head was manually assembled on a matching unimplanted TiAlV trunnion in a mechanical testing machine (MTS Bionix) and loaded at 500N/sec to a maximum assembly load of 4000N. The head/trunnion specimen was then mounted in a torsional loading fixture and immersed in bovine serum. A cyclic torque was applied to the head with an initial maximum value of 2 Nm. The specimen was unloaded and held for a 30 sec wait period and the torsional loading was repeated to a peak value of 4 Nm. With each torsional cycle the peak torque was increased by 2 Nm until the taper junction underwent rotational failure. During testing, relative motion between the femoral head and the trunnion was measured with a displacement transducer (DVRT-3, MicroStrain, accuracy = ± 0.1%, resolution = 1.5 μm, hysteresis & repeatability = ± 1 μm). A separate disassembly test was performed by first assembling each specimen with 4000N and then applying a distraction force at 0.008 mm/sec until separation.


Michael Olsen Peter Lewis Ryan Wolek Michael McKee James Waddell Emil Schemitsch

Introduction:

One method of femoral head preservation following avascular necrosis (AVN) is core decompression and Tantalum Rod insertion. There is, however, a published failure rate of up to 32% at 4 years. The purpose of the present study was to document the clinical and radiological outcome following Total Hip Arthroplasty (THA) subsequent to failed Tantalum Rod insertion.

Methods:

Twenty-five failed Tantalum Rod insertions subsequently requiring THA were identified from a prospectively updated database. Seventeen patients met minimum 2 year clinical and radiographic follow-up criteria. St. Michael's Hip (SMH) scores were compared to a matched cohort of patients with THA for AVN without prior Tantalum Rod insertion. Postoperative radiographs were reviewed assessing component alignment, linear wear (Dorr & Wan) and presence of tantalum residue within the joint space.


Yoshio Onishi Kazunori Hino Masami Ishimaru Hiromasa Miura

Introduction:

In posterior cruciate ligament-retaining total knee arthroplasty (CR-TKA), a small bone block (bony island) is often preserved to protect the attachment of the posterior cruciate ligament (PCL), which might be troublesome. In contrast, we prefer to resect the tibial plateau completely to facilitate the surgical procedure. However, there is concern over the increase of the flexion gap due to partial detachment of the PCL. The purpose of the present study is to evaluate the influence of bony island resection on the flexion gap.

Methods:

The subjects were 20 consecutive patients who underwent posterior cruciate ligament-retaining total knee arthroplasty for varus osteoarthritis. There were 18 women, two men, with a mean age of 71.8 years (range, 62–82 years). All operations were performed using posterior cruciate ligament-retaining prosthesis (MERA Quest Knee System, Senko Medical Instrument Manufacturing, Tokyo) by the same senior author with a measured resection technique. The knees were exposed with a medial parapatellar approach. The distal femur was cut and the tibial plateau resection was made with preserving the bony island. The central joint gaps in 90° flexion and full extension were measured using a tensioning device (Offset Repo-Tensor, Zimmer, Warsaw, IN) at 40-lb distracting force. Then, after the resection of the bony island, the central joint gaps were measured by the same method. In addition, the posterior tilt of the tibial resection and the depth of the lateral tibial cut were measured.


Orhun Muratoglu David Bichara Erik Malchau Nanna Hylleholt Selami Cakmak Ebru Oral

Introduction

In vitro findings (Bladed CL et al. ORS 2011 and J Biomed Mater Res B Appl Biomater, 2012) have suggested that UHMWPE wear particles containing vitamin-E (VE) may have reduced functional biologic activity and decreased osteolytic potential. Currently, there is no in vivo data determining the effects of wear debris from this new generation of implants. In this study we hypothesized that particles from VE-stabilized, radiation cross-linked UHMWPE (VE-UHMWPE) would cause reduced levels of osteolysis in a murine calvarial bone model when compared to virgin gamma irradiated cross-linked UHMWPE.

Methods

Study groups: 1). Radiation cross-linked VE-UHMWPE, 0.8% by weight, diffused after 100 kGy; 2). Radiation cross-linked virgin UHMWPE (virgin UHMWPE); 3). Shams. Particle generation and implantation: UHMWPE was sent to Bioengineering Solutions for particle generation. After IACUC approval, C57BL/6 mice (n = 12 for each group) received 3 mg of particulate debris overlying the calvarium and euthanized after 10 days. Micro-CT scans: Performed using an X-Tek-HMX-ST-225 with 70 kV voltage and 70 μA current. Topographical Grading Scale: Each calvarial bone was blindly scored with the following scale: 0 = No osteolysis, defined as intact bone; 1 = Minimal osteolysis, affecting 1/3 or less of the bone area; 2 = Moderate osteolysis, affecting at least 2/3 of the bone area; 3 = Severe osteolysis, defined as completely osteolytic bone. Histology H&E and TRAP staining was performed. Statistical Analysis: Inter-rater analysis was performed using Cohen's kappa analysis. Inter-rater coefficient >0.65 was considered as high inter-rater agreement. Comparison between groups was made using one-way ANOVA with post hoc Bonferroni correction for multiple comparisons. Correlations are reported as Spearman's rho. A p-value<0.05 was considered statistically significant.


Douglas E Padgett Jon Dounchis Charles R Bragdon Leah Elson Henrik Malchau

Introduction:

Acetabular component orientation has been linked to hip stability as well as bearing mechanics such as wear. Previous studies have demonstrated wide variations of cup placement in hip arthroplasty using conventional implantation techniques which rely upon either anatomic landmarks or the use of commercial positioning guides. Enabling technologies such as navigation have been used to improve precision and accuracy. Newer technologies such as robotic guidance have been postulated to further improve accuracy. The goal of our study was to evaluate the clinical reproducibility of a consecutive series of haptically guided THR.

Methods:

119 patients at 4 centers were enrolled. All patients had preoperative CT scans for the purpose of planning cup placement in lateral opening and version using proprietary software (Mako, Ft. Lauderdale, FL). All procedures were performed using a posterolateral approach. Following bone registration, acetabular preparation and component position is performed using haptic guidance. Final implant postion is ascertained by obtaining 5 points about the rim of the acetabular component and recorded. At 6 weeks, all patients had AP and cross-table lateral radiographs which were then analyzed for cup abduction and anteversion using the Hip Analysis Suite software. The goal was to determine the variability between desired preoperative plan, intraoperative measurement and postoperative results.


Mark Frankle Ioannis Pappou Nazeem Virani Rachel Clark

Background:

The rising number of morbidly obese patients may have significant consequences on the health care system. It may alter the effectiveness, safety as well as cost of certain surgical procedures. Reverse shoulder arthroplasty (RSA) is rapidly gaining in popularity. We investigated the effect of morbid obesity on outcomes, complications, disposition and cost in morbidly obese patients undergoing RSA in a 1: 3 case control series.

Methods:

Our joint registry was searched for all patients undergoing primary RSA (excluding fractures) with a minimum of 24 months follow-up from 2003–2010; 21 patients with Body Mass Index (BMI) > 35 were identified (follow-up 45 ± 16 months, 17 females and 4 males, age 69 ± 7) and compared to 63 matched control patients with BMI<30 (follow-up 48 ± 20, 50 females, age 71 ± 6). Outcome data was obtained pre- and postoperatively. Patients' Charlson-Deyo comorbidity index (CDI), total comorbidities, operative time, blood loss (EBL), hospitalization length, disposition, cost and complications were recorded.


Stephen Incavo Philip Noble Kyle Borque Jonathan Gold Rupal Patel Sabir Ismaily

Introduction

Increasing attention to the functional outcome of total knee arthroplasty (TKA) has demonstrated that many patients experience limitations when attempting to perform demanding activities that are normal for age-matched peers, primarily because of knee symptoms. Episodes of instability following TKA are most commonly reported during activities in which significant transverse or torsional forces are supported by the joint with relatively low joint compression forces, including stair-descent and walking on sloped or uneven surfaces. This study was performed to examine the influence of conformity between the femoral and tibial components on the Antero-Posterior (AP) stability of knee during stair descent.

Methods

Six cadaveric knees were loaded in a six degree-of-freedom joint simulator, with the application of external forces simulating the action of the quadriceps and hamstring muscles and the external loads and moments occurring during stair descent, including the stages of terminal swing phase, weight-acceptance phase (prior to and after quadriceps contraction) and mid-stance. During these manoeuvres, the displacement and rotation of the femur and the tibia were measured with a multi-camera high resolution motion analysis system (Fig. 1). Each knee was tested in the intact and ACL deficient condition – and after implantation of total knee prosthesis with Cruciate-Retaining (CR), Cruciate-Sacrificing with an intact PCL (CS + PCL), Cruciate-Sacrificing with an absent PCL (CS-PCL) and Posterior-Stabilizing (PS) tibial inserts (Figs 2 and 3).


Brett Wiater Daphne Pinkas Denise Koueiter Tessa Buhovecky J. Michael Wiater

Introduction:

Reverse total shoulder arthroplasty (RTSA) has become an accepted surgical treatment for patients with severe deficiency of the rotator cuff. Despite the utility of RTSA in managing difficult shoulder problems, humeral rotation does not reliably improve and may even worsen following RTSA. Several approaches to increase active external rotation (aER) postoperatively have been proposed including the use of concomitant latissimus dorsi tendon transfer (LDTT) or the use of an increased lateral-offset glenosphere (LG). We hypothesized that clinical outcome and range of motion after RTSA with a +4 mm or +6 mm LG would be comparable to RTSA with LDTT in patients with a lack of aER preoperatively.

Methods:

An IRB-approved, prospective, single surgeon RTSA registry was reviewed for patients treated with LDTT or LG for preoperative aER deficiency with minimum 1-year follow-up. Patients qualified for aER deficiency if they had a positive ER lag sign or less than or equal to 10 degrees of aER preoperatively. Matched control groups with patients that did not have preoperative lack of aER and were not treated with LDTT or LG were included for comparison. Outcomes measures included Constant-Murley score (CMS), American Shoulder and Elbow Surgeons (ASES) score, Subjective Shoulder Value (SSV), ASES Activities of Daily Living (ADL) score, Visual Analogue pain Scale (VAS), active forward elevation (aFE), active internal rotation (aIR), and aER. An independent, institutional biostatistician performed statistical analyses.


Brett Wiater James Moravek Daphne Pinkas Denise Koueiter Tristan Maerz David Marcantonio J. Michael Wiater

Introduction:

Reverse total shoulder arthroplasty (RTSA) has become instrumental in relieving pain and returning function to patients with end-stage rotator cuff disease. A distalized and medialized center of rotation in addition to a semi-constrained implant design allows the deltoid to substitute for the non-functioning rotator cuff. The purpose of this study was to examine the relationship between specific deltoid and rotator cuff muscle parameters and functional outcomes following RTSA.

Methods:

Patients undergoing RTSA by a single surgeon were enrolled in a prospective, IRB approved RTSA outcomes registry. Inclusion criteria were diagnosis of cuff tear arthropathy or massive rotator cuff tear, a minimum 2-year follow-up, and a preoperative shoulder MRI. We excluded patients undergoing revision arthroplasty, fracture, and a history of previous open shoulder surgery. For the 28 patients meeting our criteria, the cross-sectional area (CSA) of the anterior, middle, and posterior deltoid were measured on an axial MRI (Figure 1). Fatty infiltration (FI) of the deltoid, supraspinatus (SS), infraspinatus (IS), teres minor, and subscapularis were assessed on sagittal T1-MRI quantitatively via image processing and qualitatively on the 5-point Fuchs scale by a fellowship-trained musculoskeletal radiologist. Outcome measures included active forward elevation (aFE), active external rotation (aER), active internal rotation (aIR), strength in abduction, Constant-Murley score (CMS), Subjective Shoulder Value (SSV), Visual Analogue Scale (VAS) pain, and American Shoulder and Elbow Surgeons (ASES) total and ASES activities of daily living (ADL) scores as assessed by a trained, clinical research nurse. Correlation of deltoid CSA and FI with outcomes measures was analyzed with a Spearman rank correlation coefficient (ρ) with significance at P < .05.


Aidin Eslam Pour Greg A. Erens Thomas L. Bradbury James R. Roberson Alec A. Johnson Richard Thomas

Introduction:

The routine use of posterior hip dislocation precautions is typically utilized postoperatively following total hip arthroplasty via a posterior surgical approach. This has included use of an abduction pillow and limiting adduction, internal rotation and flexion more than 90 degrees for a minimum of 6 weeks postoperatively. This may slow the course of rehabilitation, increase the length of hospital stay and the total cost of the procedure, and add additional anxiety to the patient. We conducted this study to see if posterior hip precautions are necessary after total hip arthroplasty via a posterior approach when the hip meets certain intraoperative criteria for stability.

Methods and Materials:

All patients in our institute undergo routine hip stability testing during primary total hip arthroplasty via a posterior approach. Before October 2010, all of our primary total hip arthroplasty patients were placed on routine hip precautions. We stopped hip precautions in October 2010 for all the patients who were noted to meet hip stability criteria intraoperatively. We prospectively compared the consecutive patients who underwent this procedure without hip precautions with a retrospective control group of patients who had hip precautions.


Aidin Eslam Pour Jean Yves Lazennec Adrien Brusson MA Rousseau Ian Clarke

Introduction

Accurate evaluation of femoral offset is difficult with conventional anteroposterior (AP) X-rays. Routine CT imaging is costly and exposes patients to a significant dose of radiation. The EOS® imaging system is an innovative slot-scanning radiography system that makes possible the acquisition of simultaneous and orthogonal AP and lateral images of the patient in standing position. These 2-dimensional (2D) images are equivalent to standard plane X-rays. Three-dimension (3D) reconstructions are obtained from these paired images according to a validated protocol. This prospective study explores for the first time the value of the EOS® imaging system for comparing measurements of femoral offset obtained from 2D images and 3D reconstructions.

Materials and Methods

Following our standard protocol, we included a series of 100 patients with unilateral total hip arthroplasty (THA). The 2D offset was measured on the AP view with the same protocol as for standard X-rays. The 3D offset was calculated from the reconstructions based on the orthogonal AP and lateral views. Reproducibility and repeatability studies were conducted for each measurement. We compared the 2D and 3D offsets for both hips (with and without THA).


Peng Zeng W Mark Rainforth Amit Rana Rob Thompson Alfons Fischer

With its high wear and corrosion resistance, CoCrMo alloy has been widely used for metal-on-metal total hip replacements (THRs). However, the use of the metal-on-metal implants has dropped substantially as a result of several alerts issued by the Medicines and Healthcare products Regulatory Agency (MHRA) due to concern on metal ion release [1]. However, some of the first generation of metal-on-metal THRs have lasted for more than 20 years [2]. It is far from clear why some MoM joints have survived, while other failed. It is known that dynamic changes occur at the metal surface during articulation. For example, a nanocrystalline layer has been reported on the topmost surface of both in vivo and in vitro CoCrMo THRs [3, 4] but it is not known whether this layer is beneficial or detrimental.

The current work focuses on the sub-surface damage evolution of explanted MoM hips, which is compared to in vitro tested CoCrMo hip prostheses. Site-specific TEM cross-section of both in vivo and in vitro CoCrMo samples were prepared by focused ion beam (FIB) in situ lift-out method (Quanta 200 3D with Omniprobe, FEI, the Netherlands). TEM of the FIB specimens was performed on various microscopes. Routine bright field imaging was performed on a Tecnai 20 (FEI, the Netherland) operating at 200 kV, while high resolution transmission electron microscopy (HRTEM) of the nanocrystalline layer and other surface species was undertaken on a Jeol 2010F (Jeol, Japan) operating at 200 kV.

A nanocrystalline layer (which was not present on the starting surfaces) was observed on both explanted in vivo and in vitro tested materials. For the explanted joints, the nanocrystalline layer was thin (a few 100 nm) and the extent did not appear to correlate with the local wear rate. For in vitro samples, the nanocrystalline layer was thicker (up to micron). HRTEM from this layer are shown in Fig. 1 and Fig. 2. The nanocrystallite size was ∼5 nm and appeared to be a mixture of face centred cubic and hexagonal close packed phases. The formation of the nanocrystalline layer and its correlation with wear behaviour are discussed.


Lokesh Kumar Raja Laura Yanoso-Scholl Jim Nevelos Gregg Schmidig Mayur Thakore

Introduction

Frictional torque is generated at the hip joint during normal gait loading and motion [1]. This study investigated the effect of shell deformation due to press-fit on frictional torque generated at the articulating surfaces of cementless acetabular shells that incorporated fixed and dual mobility bearing designs.

Materials and Methods

Figure 1 lists the study groups (minimum of n = 5). All groups were tested with a 50 mm Trident PSL shell (Stryker Orthopaedics, NJ) and a Ti6Al4V trunnion. Metal-on-Metal specimens were custom designed and manufactured, and are not approved for clinical use. The remaining groups consisted of commercially available products (Stryker Orthopaedics, NJ).

All groups were tested with the shells in deformed and undeformed states.

Deformed Setup: A two-point relief configuration was created in a polyurethane foam block (Figure 2) with a density of 30 lb/ft3 to replicate shell deformation due to press-fit [2]. The blocks were machined to replicate the press-fit prescribed in the shell's surgical protocol. Each shell was assembled into the foam block by applying an axial force at 5 mm/min until it was completely seated.

Undeformed Setup: Each shell was assembled in a stainless steel block with a hemispherical cavity that resulted in a line-to-line fit with the shell OD.

Frictional torque was measured using a physiologically relevant test model [3]. In this model, the specimen block was placed in a fixture to simulate 50° abduction and 130° neck angle (Figure 2). A 2450N side load was applied and the femoral head underwent angular displacement of ± 20° for 100 cycles at 0.75 Hz. The articulating surfaces were lubricated with 25% Alpha Calf Fraction Serum.

Peak torque was observed towards the end or the beginning of each cycle where the velocity of the femoral head approaches 0 and the head changes direction. This torque is referred as maximum static frictional torque. Specimen groups were statistically compared with a single-factor ANOVA test and a Tukey post-hoc test at 95% confidence level. Paired t-tests were performed to compare individual groups in deformed and undeformed states.


Caroline Park Anil Ranawat Anthony Chang Saker Khamaisy Andrew Pearle

Introduction:

Unicompartmental knee arthroplasty (UKA) is a well established method for treatment of single compartment arthritis. However, a subset of patients still present with continued pain after their procedure in the setting of a normal radiographic examination. We propose the use of magnetic resonance imaging (MRI) as a useful modality in determining the etiology of symptoms in symptomatic unicompartmental knee arthroplasties.

Materials & Methods:

An IRB-approved retrospective analysis of 300 consecutive unicompartmental knee arthroplasties between 2008–2010 found 28 cases symptomatic for continued pain. Magnetic resonance imaging was performed with a 1.5 T Surface Coil unit after clinical and radiographic assessment. MRI evaluation included assessment for osteoarthritis, synovitis, osteolysis, and loosening. Validated questionnaires including PAQ, WOMAC and UCLA Activity Score were used for clinical assessment


Amar Ranawat Peter White

Objective:

Patient-specific or “custom” total knee replacements have been designed to fit the arthritic knee in primary total knee arthroplasty (TKA) better than “off-the-shelf” implants. Using computer technology, patient-specific cutting-blocks and custom-made implants are created to more accurately fit the contour of the knee and reproduce the anatomic J-curve with the hope of providing a better functional outcome.

Purpose:

This retrospective, matched-pair study evaluates manipulation under anesthesia (MUA) rates in cemented patient-specific cruciate-retaining (PSCR) TKA compared to that in both cemented posterior-stabilized (PS) and non-cemented cruciate-retaining rotating-platform (NC CR RP) TKA.


Parthiv Rathod Ajit Deshmukh Sean Bhalla Jose Rodriguez

INTRODUCTION

Acetabular cup orientation is an important element of Total Hip arthroplasty (THA). The purpose of this retrospective case-control study was to compare variability of acetabular cup placement between THA performed via Direct Anterior Approach (DAA) with fluoroscopy in supine position and posterior approach (PA) in lateral position without use of fluoroscopy.

METHODS

Radiographic and clinical records of THAs performed by a single, high volume arthroplasty surgeon at one institution were reviewed. Patients with similar design of uncemented acetabular cup, femoral component and bearing surface were included to form two groups. PA group consisted of 300 THAs performed from May 2006 to June 2009. DAA group consisted of 300 THAs performed from Oct 2009 to Oct 2011 excluding first 100 cases to eliminate the influence of learning curve. Radiographic analysis was done by two independent blinded observers to determine cup inclination and anteversion (Liaw et al) on standardized, 6 week postoperative, standing anteroposterior pelvic radiographs using Picture Archiving and Communication System software (PACS).


Michael Reimeringer Natalia Nuño

Introduction

Modeling the press-fit that occurs in Total Hip Arthroplasty (THA) cementless implants is crucial for the prediction of micromotion using finite element analysis (FEA). Some studies investigated the effect of the press-fit magnitude and found a direct influence on the micromotion [1,2]. They assumed in their model that press-fit occurs throughout the prosthesis. However [3] found using computed tomography measurement that only 43% of the stem-bone interfaces is really in contact. The aim of this study is to investigate the press-fit effect at the stem-bone interface on the implant micromotion.

Methods

Finite element analysis (FEA) was performed on a Profemur® TL implanted into a Sawbones®. The implant orientation was validated in a previous study [4]. All materials were defined as linear isotropic homogeneous. FEA was carried out for the static loading conditions defined by [5] simulating walking fastly. Frictional contact between the bone and the prosthesis was assumed all along the prosthesis with a coefficient μ set to 0, 63 for the plasma spray (Fig. 1a) and 0,39 for the polished surface (Fig. 1b) [6]. Firstly, FEA was performed without press-fit (Fig. 2a) and then press-fit was simulated with an interference of 0,05 mm [2] between stem and bone in specific areas: superior (Fig. 2b), intermediate (Fig. 2c), inferior (Fig. 2d), and cortical alone (Fig. 2e) and finally over the entire surface in contact with the bone. The press-fit effect at the stem-bone interface on the micromotion was investigated. Measurement of the micromotion was realised on different points located on the plasma spray surface by calculating the difference between the final displacement of the prosthesis and the final displacement of the bone.


Joern Reinders Robert Sonntag J. Philippe Kretzer

Background:

Standardized preclinical wear testing cannot replicate the variations of wear rates and wear mechanisms seen in-vivo [1]. Therefore, a lot of studies focused on testing scenarios which replicate a wider range of patient-specific conditions such as different activities or malalignment of components. However, differences between the in-vivo and in-vitro situation regarding the environmental conditions are often neglected.

Considerable differences between the in-vivo and the in-vitro situation are related to the surrounding synovial fluid and its in-vitro substitute (bovine serum). For the in-vivo knee only small volumes (1–4 ml) of synovial fluid are reported [2]. However, for in-vitro testing several hundreds of milliliters of bovine serum are typically used. Therefore, the hypothesis of this study is that fluid volume significantly influences the wear rates in simulator tests.

Material and Methods:

For wear testing an established implant system (Sigma® PFC, DePuy, Warsaw, USA) has been used.

Four wear tests with four different testing volumes of bovine serum were carried out: 250 ml; 150 ml; 75 ml; 45 ml. The testing volume of the original chamber (250 ml) was reduced using solids (Fig. 1). Care was taken, that the contact surfaces of the implants were completely immersed and the fluid level was kept constant in all cases (Fig. 1). The testing fluid was maintained at a temperature of 37 ± 1°.

All wear tests were run displacement controlled according to ISO 14243-3: 2004 on an AMTI knee simulator.


Steven Reinitz Barbara Currier Douglas Van Citters

Irradiated, thermally stabilized, highly cross-linked UHMWPE bearings have demonstrated superior wear performance and improved in vitro oxidation resistance compared with terminally gamma-sterilized bearings, yet retrieval analysis reveals unanticipated in vivo oxidation in these materials. There has been little evidence to date that oxidation in these materials is leading to degradation of mechanical properties, but since oxidation has previously been shown to cause chain scission in other materials, there is the potential for oxidation to cause decreased molecular weight and crosslink density. The aim of this study was to determine whether measured in vivo oxidation in highly cross-linked tibial bearings corresponds with a decreasing crosslink density. Retrieval analysis for three tibial bearing materials reveals that crosslink density is decreasing following in vivo duration, and that the change in crosslink density is strongly correlated with oxidation. The results suggest that oxidation in highly cross-linked materials is causing chain scissions that may impact the material properties. If the correlation between oxidation and duration continues, then as longer duration, more oxidized devices are retrieved there is a potential for measurable mechanical property changes.


Tanille Paniogue Steven Reinitz Douglas Van Citters

In vivo oxidative degradation in ultra-high molecular weight polyethylene (UHMWPE) has gained significant attention in recent years, especially with the discovery of unanticipated oxidation in retrieved highly cross-linked bearings. While significant attention has been paid to mechanical property changes caused by oxidation, there has been little focus on understanding how wear rates are affected by these in vivo changes. Recent work has demonstrated the possibility of machining wear pins from retrieved UHMWPE bearings, but leveling of the pins removed the in vivo articular surface.[1] The goal of this study is to determine whether wear pins can be produced utilizing the native articular surface.

Three materials were used for this study: a short-duration retrieved mobile-bearing conforming tibial insert with minimal oxidation (non-oxidized); a shelf-aged, oxidized, non-conforming fixed bearing tibial insert (oxidized); and standard NIST 1050 bar stock (NIST). Utilizing both conforming and non-conforming devices tests the technique over a range of articular curvatures, while testing a highly oxidized material tests the feasibility of maintaining the native surface when machining wear pins with compromised mechanical properties.

FTIR analysis was performed at the articular surface of the devices near where the pins were taken, using ketone peak height as an indicator of oxidation. Wear rates were determined using a six station AMTI OrthoPod with an applied load of 100 N in multidirectional motion for a total of 2 million cycles.

The oxidized material had a surface ketone level of 0.26, the non-oxidized device had a ketone level of 0.05, and the NIST sample had a ketone level less than 0.01. Two pins of each material were machined to ¼″ diameter with a length of the through thickness of the tibial inserts; soak controls were also produced.

Figure 1 shows mass loss data for all six pins tested. Wear rates between the two pins of each group were fairly repeatable, and the wear rates of the different groups could be easily differentiated. The pins machined from NIST bar stock showed the best match-up, but pins machined from retrieved devices also showed good repeatability, with the non-conforming device showing better results than the conforming device.

The ability to produce repeatable wear results with pins machined from in vivo devices is an important step in understanding how the wear rate changes over time in vivo. By maintaining the native articular surface, this test will give a more true representation of the in-vivo wear rate. This method will enable future investigations into how wear rates are affected by oxidation, absorbed chemical species, or other changes that occur in vivo.


Leah Elson Martin Roche Christopher Anderson

Introduction

Post-operative clinical outcomes of TKA are dependent on a multitude of surgical and patient-specific factors. Malrotation of the femoral and/or tibial component is associated with pain, accelerated wear of the tibial insert, joint instability, and unfavorable patellar tracking and dislocation. Using the transepicondylar axis to guide implantation of the femoral component is considered to be an accurate anatomical reference and is widely used. However, no gold standard currently exists with respect to ensuring optimal rotation of the tibial tray. Literature has suggested that implantation methods, which reference the tibial tubercle, reduce positioning outliers with more consistency than other anatomical landmarks. Therefore, the purpose of this evaluation is to use data collected from intraoperative sensors to assess the true rotational accuracy of using the mid-medial third of the tibial tubercle in 98 TKAs.

Methods

The data for this evaluation was retrieved from 98 consecutive patients who underwent primary TKA from the same highly experienced surgeon. Femoral component rotation was verified in every case via the use of the Whiteside line, referencing the transepicondylar axis, and confirming appropriate patellar tracking. Tibial tray rotation was initially established by location of the mid-medial third of the tibial tubercle. Rotational adjustments of the tibial tray were evaluated in real-time, as the surgeon corrected any tibiofemoral incongruency and tray malpositioning. The initial and final angles of tibial tray rotation were captured with intraoperative video feed, and recorded. A z-test of differences between pre- and post-rotational correction was performed to assess the statistical significance of malrotation present in this cohort.


Jerry D'Alessio Martin Roche Mark Kester

INTRODUCTION:

Proper tibial rotation has been cited as an important prerequisite to optimal total knee replacement. The most commonly recognized rotational landmark is the medial 1/3rd of the tibial tubercle. The purpose of this study was to quantify the amount of variability this structure has from a common reference as well as to understand the effects of component design when referencing this structure.

METHODS:

Subjects were prospectively scanned into a Virtual Bone Database (Stryker Orthopaedics, Mahwah, NJ), which is a collection of body CT scans from subjects collected globally. All CT scans displayed cropped bones were excluded. SOMA™ (Stryker) is a unique tool with the ability to take automated measurements of quantities such as distances and angles on a large number of pre-segmented bone samples which was then to perform calculations represented in this study. Demographic information for each subject was recorded were known. For the analysis, the mechanical axis of the tibia (MAT) was established by connecting the center of the proximal tibia to the center of the ankle. From the MAT, a perpendicular resection plane was made at a distance of 9 mm from the most proximal portion of the lateral condyle. This plane was then used as a virtual resection plane to establish the points for the remaining structures which was the medial 1/3rd of the tibial tubercle and the posterior notch of the PCL insertion. The following axes were identified: 3TT (line between the medial 1/3rd of the tibial tubercle and the posterior notch of the tibia); 3CTT (line between the medial 1/3rd of the tibial tubercle and the center of the tibia); and the posterior axis of the tibia (line connecting the two most posterior points of the tibia at the virtual resection plane). Measurements made were the angle of the 3TT Line to the posterior axis and the angle of the 3CTT Line to the posterior axis.


Christopher Roche Phong Diep Sean Grey Pierre Henri Flurin Joseph Zuckerman Thomas Wright

Introduction

Posterior glenoid wear is common in glenohumeral osteoarthritis. Tightening of the subscapularis causes posterior humeral head subluxation and a posterior load concentration on the glenoid. The reduced contact area causes glenoid wear and potentially posterior instability. To correct posterior wear and restore glenoid version, surgeons may eccentrically ream the anterior glenoid to re-center the humeral head. However, eccentric reaming undermines prosthesis support by removing unworn anterior glenoid bone, compromises cement fixation by increasing the likelihood of peg perforation, and medializes the joint line which has implications on joint stability. To conserve bone and preserve the joint line when correcting glenoid version, manufacturers have developed posterior augment glenoids. This study quantifies the change in rotator cuff muscle length (relative to a nonworn/normal shoulder) resulting from three sizes of posterior glenoid defects using 2 different glenoids/reaming methods: 1) eccentric reaming using a standard (nonaugmented) glenoid and 2) off-axis reaming using an 8, 12, and 16° posterior augment glenoid.

Methods

A 3-D computer model was developed in Unigraphics (Siemens, Inc) to simulate internal/external rotation and quantify rotator cuff muscle length when correcting glenoid version in three sizes of posterior glenoid defects using posterior augmented and non-augmented glenoid implants. Each glenoid was implanted in a 3-D digitized scapula and humerus (Pacific Research, Inc); 3 sizes (small, medium, and large) of posterior glenoid defects were created in the scapula by posteriorly shifting the humeral head and medially translating the humeral head into the scapula in 1.5 mm increments. Five muscles were simulated as three lines from origin to insertion except for the subscapularis which was wrapped. After simulated implantation in each size glenoid defect, the humerus was internally/externally rotated from 0 to 40° with the humerus at the side. Muscle lengths were measured as the average length of the three lines simulating each muscle at each degree of rotation and compared to that at the corresponding arm position for the normal shoulder without defect to quantify the percentage change in muscle length for each configuration.


Alessandro Russo Silvia Panseri Tatiana Shelyakova Monica Sandri Alessandro Ortolani Steve Meikle Joe Lacey Anna Tampieri Valentin Dediu Matteo Santin Maurilio Marcacci

Introduction

Diaphyseal bone defect represents a significant problem for orthopaedic surgeons and patients. Bone is a complex tissue whose structure and function depend strictly on ultrastructural organization of its components: cells, organic (extracellular matrix, ECM) and inorganic components. The purpose of this study was to evaluate bone regeneration in a critical diaphyseal defect treated by implantation of a magnetic scaffold fixed by hybrid system (magnetic and mechanical), supplied through nanoparticle-magnetic (MNP) functionalized with Vascular Endothelial-Growth-Factor-(VEGF) and magnetic-guiding.

Methods

A critical long bone defect was created in 8 sheep metatarsus diaphysis: it was 20.0 mm in length; the medullary canal was reamed till 8.00 mm of inner diameter. Then a 8.00 mm diameter magnetic rod was fitted into proximal medullary canal (10 mm in length).

After that a scaffold made of Hydroxyapatite (outer diameter 17.00 mm) that incorporates magnetite (HA/Mgn 90/10) was implanted to fill critical long bone defect. A magnetic rod (6.00 mm diameter) was firmly incorporated at proximal side into the scaffold. Both magnets had 10 mm length. To give stability to the complex bone-scaffold-bone a plate was used as a bridge; it was fixed proximally by 2 screws and distally by 3 screws.

Scaffolds biocompatibility was previously assessed in vitro using human osteoblast-like cells. Magnetic forces through scaffold were calculated by finite element software (COMSOL Multiphysics, AC/DC Model).

One week after surgery, magnetic nanoparticles functionalized with VEGF were injected at the mid portion of the scaffold using a cutaneous marker positioned during surgery as reference point in 4 sheep; other sheep were used as control group. After sixteen weeks, sheep were sacrificed to analyze metatarsi. Macroscopical, radiological and microCT examinations were performed.


Michael Kurdziel Vani Sabesan Jeffrey Ackerman Vinay Sharma Kevin Baker J. Michael Wiater

Purpose:

The optimal degree of conformity between the glenoid and humeral components in cemented total shoulder arthroplasty (TSA) has not been established. Glenoid component stability is thought to be at risk due to the “rocking-horse” phenomenom, which, can lead to increased micromotion and loosening in response to humeral head edge loading. The goal of this biomechanical study is to investigate the influence of glenohumeral mismatch on bone-implant interface micromotion in a cemented glenoid implant model.

Methods:

Twenty-Five cemented glenoid components (Affiniti, Tornier, Inc., Bloomington, MN, USA) were implanted in polyurethane foam biomechanics testing blocks. Five glenoid sizes, 40 mm, 44 mm, 48 mm, 52 mm and 55 mm (n = 5 per glenoid size), were cyclically tested according to ASTM Standard F-2028-08. A 44 mm humeral head (Affiniti, Tornier, Inc., Bloomington, MN, USA) was positioned centrally within the glenoid fixed to a materials testing frame (MTS Mini-Bionix II, Eden Prairie, MN, USA). Phase I testing (n = 3 per glenoid size) involved a subluxation test for determination of the humeral head translation distance which would be used for phase II cyclic testing. During cyclic loading, the humeral head was translated ± distance for 50,000 cycles at a frequency of 2 Hz, simulating approximately 5 years of device use. Glenoid compression, distraction, and superior-inferior glenoid translation were measured throughout testing via two differential variable reluctance transducers.


Tomotaro Sato Atsushi Kaneko Hisato Ishikawa Daihei Kida

Reducion of friction between bearing surfaces in Total Hip Arthroplasty is a main target of biological tribology. MPC (2-Methacryloyloxyethyl phosphorylcholine) has a similar properties to those of cell membranes, and can reduce friction with fluid luburication. We have used crosslink polyethylene with MPC polymer coating for primary and revision THA since 2011.

Eighty one cementless THA were performed with closslink polyethlene liner with MPC polymer in our hospital. We have examined 21 cases which were followed for more than one year. Eighteen cases for primary THA and three for revision THA, and 3 were male and 18 were female. Seventeen cases were osteoarthritis, two osteonecrosis of femoral head and two rheumatoid arthritis. Average age of patients at THA was 60.4 years old.

In the OR, we have experienced a very wet and slippery feeling on the bearing surface of polyethylene liner every time. Surface touch is similar to skin with lotions. No wear were measured on the X-ray display and no infections and no fractures were occurred during follow up.

MPC polymer coating in THA can be useful for reduction of friction and generation of wear debris.


Peter Sculco Lionel E. Lazaro Jacqueline Birnbaum Craig Klinger Jonathan P. Dyke David L. Helfet Dean G. Lorich Edwin Su

Introduction:

A surgical hip dislocation provides circumferential access to the femoral head and is essential in the treatment pediatric and adult hip disease. Iatrogenic injury to the femoral head blood supply during a surgical may result in the osteonecrosis of the femoral head. In order to reduce vessel injury and incidence of AVN, the Greater Trochanteric Osteotomy (GTO) was developed and popularized by Ganz. The downside of this approach is the increased morbidity associated with the GTO including non-union in 8% and painful hardware requiring removal in 20% of patients. (reference) Recent studies performed at our institution have mapped the extra-osseous course of the medial femoral circumflex artery and provide surgical guidelines for a vessel preserving posterolateral approach. In this cadaveric model using Gadolinium enhanced MRI, we investigate whether standardized alterations in the postero-lateral surgical approach may reliably preserve femoral head vascularity during a posterior surgical hip dislocation

Methods:

In 8 cadaveric specimens the senior author (ES) performed a surgical hip dislocation through the posterolateral approach with surgical modifications designed to protect the superior and inferior retinacular arteries. In every specimen the same surgical alterations were made using a ruler: the Quadratus Femoris myotomy occurred 2.5 cm off its trochanteric insertion, the piriformis tenotomy occurred at its insertion and extended obliquely leaving a 2 cm cuff of conjoin tendon (inferior gemellus), and the Obturator Externus (OE) was myotomized 2 cm off its trochanteric insertion. (Figure 1) For the capsulotomy, the incision started on the posterior femoral neck directly beneath the cut obturator externus tendon and extending posteriorly to the acetabulum. Superior and inferior extensions of the capsulotomy ran parallel to the acetabular rim creating a T-shaped capsulotomy. After the surgical dislocation was complete, the medial femoral circumflex artery (MFCA) was cannulated and Gadolinium-enhanced MRI performed in order to assess intra-osseous femoral head perfusion and compared to the gadolinium femoral head perfusion of the contra-lateral hip as a non-operative control. Gross-dissection after polyurethane latex injection in the cannulated MFCA was performed to validate MRI findings and to assess for vessel integrity after the surgical dislocation.


Ashit Shah

Introduction:

During TKR it is mandatory to achieve perfect soft tissue balance and component alignment. As knee is covered in front by quadriceps mechanism, there is some manipulation of this structure while approaching knee for an arthroplasty. This alteration in Quadriceps mechanism can affect outcome of the surgery.

Aim:

To analyze the results of Trivector arthrotomy for TKR surgery.


Full Access
Rajeev Kumar Sharma

Complete or partial disruption of the collateral ligament during total knee arthroplasty in severe deformities is a devastating complication which sometimes remains unnoticed at the time of surgery. We analysed 280 knees in 150 patients with over 30° varus with flexion (196 knees), flexion deformity alone (60 knees) & valgus deformity (24 knees) treated with primary total knee arthroplasty from January 2002 to January 2008. The mean age of patient was 65 years (ranging from 54 years to 78 years).

Problems encountered were avulsion of MCL from tibial attachment in 26 knees, femoral attachment avulsion with a bony fragment in 9 knees. Lateral collateral ligament was injured in 5 knees. In 12 knees with varus of >30° with element of tibial rotation medial release alone was not enough to balance the joint. Lateral collateral ligament tightening was needed in these cases using lateral epicondylar osteotomy. In 4 cases the medial collateral ligament was reconstructed using semi-tendinosus graft. Direct repair was not done in any case. Constrained knee prosthesis was used in only 22 knees to provide added stability. The mean duration of follow-up was 42 months. Stability of the knee was assessed clinically and on fluoro-radiography in full extension, 30°flexion and at 90° flexion of the knee. Seventy three percent (38/52) patients regained stability within 2 mm, 25% (13/52) had instability upto 4 mm and only one patient had gross instability needing hinge knee prosthesis. On the side of ligament reconstruction the ROM remained 10 to 15° less than the opposite side. Range of motion knee-brace was needed for 3 weeks in all cases. In cases with ligament reconstruction using Hamstring tendon, brace was used up to 12 weeks.

In conclusion identification of ligamentous insufficiency and its management will not only prevent unstable joint but also minimize the risk of revision in future. Lateral collateral ligament tightening is needed in certain select extreme varus deformities in addition to medial release.


Andrew Shimmin Sara Martinez Martos John Owens Alex Iorgulescu

Introduction

The SAIPH™ (MatOrtho, UK) total knee replacement is a new fixed-bearing prosthesis design having attributes of a mobile bearing and the posterior stabilised categories for knee arthroplasties. The implant design goal is an articulation that provides definitive anteroposterior stability to beneficially control tibiofemoral translation, the ability for the tibia to axially rotate to accommodate various lifestyle activities, and to maintain a relatively posterior femoral position on the tibia to facilitate range of motion. This study aims to analyze knee kinematics of the SAIPH™ total knee arthroplasty (TKA) by videofluroscopy during four different weightbearing activities.

Method

Fourteen consecutive patients operated on by a single surgeon, with a minimum follow up of 24 months were included in this IRB-approved study. A medially conforming knee was implanted in all cases. Participants in the study were asked to perform weightbearing kneeling, lunging, step-up/down and pivoting activities while their knee motions were recorded by videofluoroscopy. Three-dimensional (3D) joint kinematics were determined using model-image registration. The 3D orientation of each TKA component was expressed using standard joint angle conventions, and the anterior/posterior location of each condyle was expressed relative to the deepest part of the tibial sulcus.


Peter Simon Miguel Diaz Daniel Schwartz Brandon Santoni Mark Frankle

Introduction:

The complex 3D geometry of the scapula and the variability among individuals makes it difficult to precisely quantify its morphometric features. Recently, the scapular neck has been recognized as an important morphometric parameter particularly due to the role it plays in scapular notching, which occurs when the humeral component of a reverse shoulder arthroplasty (RSA) prosthesis engages the posterior column of the scapula causing mechanical impingement and osseous wear. Prosthetic design and positioning of the glenoid component have been accepted as two major factors associated with the onset of notching in the RSA patient population. The present image-based study aimed to develop an objective 3D approach of measuring scapular neck, which when measured pre-operatively, may identify individuals at risk for notching.

Materials and Methods:

A group of 81 subjects (41 M, 69.7 ± 8.9 yrs.; 40 F, 70.9 ± 8.1 yrs.) treated with RSA were evaluated in this study. The 3D point-cloud of the scapular geometry was obtained from pre-operative computed tomography (CT) scans and rendered in Mimics. Subsequently, a subject-specific glenoid coordinate system was established, using the extracted glenoid surface of each scapula as a coordinate reference. The principal component analysis approach was used to establish three orthogonal coordinate axes in the geometric center of the glenoid. Utilization of glenoid-specific reference planes (glenoid, major axis, and minor axis plane) were selected in order to remove subjectivity in assessing “true” anterior/posterior and profile views of the scapula. The scapular neck length was defined as the orthogonal distance between the glenoid surface and the point on the posterior column with the significant change of curvature (Fig. 1). In addition, the angle between the glenoid plane, area center of the glenoid, and the point of significant change of the curvature were assessed (Fig. 2). This new parameter was developed to serve as a predictive critical value for the occurrence of notching. The incidence of notching increases as the value of the notching angle decreases. In order to evaluate relationships between glenoid and scapular neck, the glenoid width and height was also measured at the glenoid plane.


Robert Sonntag Stephan Koch Julia Merziger Johannes S. Rieger Joern Reinders Tobias Reiner J. Philippe Kretzer

Background

Migration analysis after total joint arthroplasty are performed using EBRA analysis (Krismer et al., 1997) or - more accurate but also much more cost-intensive and time-consuming – via radiostereometric analysis (RSA). For the latter, additional radiographs from two inclined perspectives are needed in regular intervals in order to define the position of the implant relative to tantalum bone markers which have been implanted during surgery of the artificial joint (Fig. 1). Modern analysis software promises a migration precision along the stem axis of a hip implant of less than 100 μm (Witvoet-Brahm et al., 2007). However, as the analysis is performed semi-automatically, the results are still dependent on the subjective evaluation of the X-rays by the observer. Thus, the present phantom study aims at evaluating the inter- and intra-observer reliability, the repeatability as well as the precision and gives insight into the potential and limits of the RSA method.

Materials and Methods

Considering published models, an RSA phantom model has been developed which allows a continuous and exact positioning of the prostheses in all six degrees of freedom (Fig. 2). The position sensitivities of the translative and rotative positioning components are 1 μm and 5 to 24, respectively. The roentgen setup and Model-Based RSA software (3.3, Medis specials bv, Leiden, Netherlands) was evaluated using the SL-PLUS® standard hip stem (size 7, Smith & Nephew, Baar, Switzerland). The inter-observer (10 repetitions) and intra-observer (3 observers) reliability have been considered. Additionally, the influences of the model repositioning and inclination as well as the precision after migration and rotation along the stem axis are investigated.


Hendrik Bertmaring Roman Preuss Robert Streicher

INTRODUCTION:

In order to obtain a secure taper connection it is advised to clean and dry the metal cup before assembling a ceramic insert. A slight axial tap using a plastic impactor completes the insertion procedure.

There are a few reported cases that the taper connection failed intraoperatively although it was inserted and impacted as recommended. A conceivable reason seems to be a high amount of fluid in the gap between insert and cup (e.g. from rinsing process, blood) that prevent the insert from being securely fixed due to its incompressibility.

Methods:

Cups embedded in a cast resin have been used in an appropriate impaction test setup. Four different amounts of 1.75% polyvinyl pyrrolidone solution with comparable viscosity to that of blood were filled into the metal cups (figure 1). To obtain reference values, tests were made with dry metal cups (0%), too.

Three different in-vivo like test conditions were considered:

The fluid

cannot escape from the gap

can permeate through a low permeable screen cloth

can permeate through a high permeable screen cloth.

The screen cloth should represent different cancellous bone densities. Ten Ceramic inserts of each size (28 and 36 mm) made of pure alumina (BIOLOX® forte) were impacted axially into the cups resulting in a peak force of approximately 1200 N, measured by a load cell (see figure 2). Ensuring the exact level of fluid before impaction for conditions 2 and 3, two different hydrophobic screen clothes were fixed across the central hole of the cup. During impaction the fluid could permeate through the screen cloth. To assess the connection strength after impaction, push-out forces have been measured.


Roman Preuss Robert Streicher

INTRODUCTION

Since over 40 years, ceramics are known for their excellent biocompatibility, extremely low wear rates and excellent wettability. This would make a ceramic-on-Polyethylene bearing also a beneficial combination for a knee implant if potential strength issues could be overcome.

METHODS

A mechanical proof-test for a ceramic femoral knee implant component was developed by subsequent steps of numerical load/stress analysis and design of adequate mechanical test equipment. The procedure was organized as follows:

Analysis of maximum in-vivo loading condition and distinguish between alternating regular loading with a high cycle number during life time and irregular worst case loading. The relevant regular loading is represented by rising from a chair and normal walking. The most critical irregular worst cases are stumbling or impact loading. The load transfer, stress distribution and the anticipated cycle number during life-time are distinguished and taken into account for the development of the test concept.

Analysis of the “boundary conditions,” i.e. the fixation of the ceramic prosthesis on the bone identifying the worst-case conditions

Finite Element analysis: Identifying regions of highest stress concentration at variable external loading

Design analysis and accommodation if necessary

From step 3 it is evident that stress concentration is mainly generated by geometric features, e.g. the shape of the corners at the interface to the cement. Significant reduction of stress concentration was achieved by some minor corrections of design details.

Development of an adequate mechanical test equipment which produces stresses comparable to the in-vivo conditions and performing of mechanical tests with ceramic femoral components

Validation of the test concept: comparison of test results and stress analysis

Assign “safety margin,” i.e. required overload tolerance of the ceramic component with respect to worst case load in-vivo

Establish “proof test,” i.e. in-production mechanical testing of each individual component in order to provide safety margin


S. David Stulberg Hasham Alvi Rushi Talati Anay Patel Mark Yaffe

Introduction:

Patient specific instrumentation (PSI) is an innovative technology in total knee arthroplasty. With the use of a preoperative MRI or CT scan, custom guide blocks are individually manufactured for each patient. Contrary to other TKA technologies such as computer-assisted surgery, PSI utilizes measured resection technique rather than a primarily ligament balancing technique. This has the potential to negatively affect the operating surgeon's ability to achieve optimal soft tissue balancing, which is especially critical in patients with severe lower extremity malalignment. Despite early research suggesting that PSI is accurate, has a low learning curve, and can reduce OR time, it remains unclear whether a surgeon using PSI can achieve optimal soft tissue balancing using a measured resection technique. The purpose of this study is to evaluate the efficacy of PSI in patients with severe preoperative limb alignment deformities.

Methods:

Fifty PSI total knee arthroplasties were performed on 46 patients (21 male, 25 female) using the Zimmer NexGen Patient Specific Instrumentation system. Each patient included in the study had a minimum preoperative deformity of at least 10° varus or valgus measured on preoperative long leg standing radiographs, Zimmer preoperative software or both. Forty-three of the included knees had a varus deformity and 7 had a valgus deformity. Preoperative mechanical axis alignment measurements were obtained using the PSI preoperative planning software and were manually calculated using pre-operative long leg standing radiographs. Postoperative mechanical axis alignment measurements were calculated using plain long leg standing radiographs. The Knee Society Scoring System was used to evaluate clinical and functional outcomes at 1 to 6 months postoperatively.


Jayson Zadzilka Bernard Stulberg

Early developments of computer assisted TKA focused on improving the technical aspects of proper registration, improved ease of use of instrumentation to ensure proper placement of cutting blocks and implants, and to document the technical improvements in alignment that come with the use of these technologies. There was minimal adoption of these technologies, as costs have been high and measured improvement in outcomes has not been demonstrated.

Patient specific instrumentation (PSI), involving preoperative three dimensional imaging and engineering of patient specific guides have been more actively embraced by the orthopaedic community – with industry embracing the technology and promoting it vigorously. This has increased interest in the use of three dimensional technologies – with reported use by up to 14% of orthopaedists in the US- despite the fact that scientific evidence has been mixed.

The next generation is merging these technologies, taking the best features of both to give the surgeon control of the patient specific TKA process. Sophisticated morphing technology coupled with innovative instrumentation now allows MONITORED real time PSI – affording the surgeon a means to fully understand the knee deformity being addressed, make decisions based on quantitative information that is accurate and easy to assess, and to resect and position parts as planned, confirming position easily (See Figure 1 & Figure 2). Additional ability to perform and monitor balancing is available if desired.

From April 2012 to April 2013 sixty-two TKAs in 56 patients underwent TKA using the Exactech GPS system. Twenty-four knees had CR TKA for varus deformity, 5 for valgus deformity; 27 had PS TKA for varus deformity, 5 for valgus deformity. The average AP alignment was 4.0°; the average clinical ROM at the most recent follow-up for CR TKA was 107° vs. 112° for PS TKA which was not significantly different. One knee has been revised to a more constrained insert for CR deficiency.

These cases were to validate the integrity of the instruments and software of a new navigation system. In April 2013, personalized instrumentation has been introduced to easily position femoral resection pins through a single, navigated instrument. Pin accuracy and cutting efficiency are easily documented, and proper femoral position in all planes is controlled. No additional imaging is needed, and the surgeon controls all aspects of decision making directly, monitored real-time patient specific TKA. It can easily be integrated for a balanced gap approach to implant positioning. This represents the newest application of three dimensional technologies and continues the field moving toward technologies that allow the surgeon to directly control all aspects of patient specific TKA.


Shinro Takai Norishige Iizawa Hidemi Kawaji

Anterior cruciate ligament (ACL) of four major knee ligaments is most crucial ligament to maintain normal knee kinematics. It is well know that ACL dysfunction causes secondary osteoarthritis of the knee. The influence of age on the biomechanical properties of the ACL was examined. The structural properties of 27 pairs of human cadaver knees without OA were evaluated. Specimens were equally divided into three groups of nine pairs each based on age: younger (22 to 35 years), middle (40 to 50 years), and older (60 to 97 years). Tensile tests of the femur-ACL-tibia complex were performed at 30 degrees of knee flexion with the ACL aligned vertically along the direction of applied tensile load. Structural properties of the femur-ACL-tibia complex, as represented by the linear stiffness, ultimate load, and energy absorbed, were found to decrease significantly with specimen age.

On the other hand, little has been written about the arthritic ACL. This study was designed to evaluate the relationship among ROM, cross sections of the intercondylar notch and the macroscopic condition of ACL degeneration. Fifty osteoarthritic patients who underwent TKA as a result of severe osteoarthritis were randomly selected. Occupation rate of the osteophytes to the notch width were measured at the anterior 1/3, middle 1/3, and posterior 1/3 notche images obtained from preoperative tunnel view. ROM was measured preoperatively and under anesthesia. Macroscopic conditions of the ACL and PCL were classified into four types of Normal, Frayed, Partial rupture, and Absent.

The macroscopic ACL conditions were Normal: 12 cases, Frayed: 15 cases, Partial rupture: 14 cases, and Absent: 9 cases. The macroscopic PCL conditions were Normal: 34 cases, Frayed: 9 cases, Partial rupture: 7 cases, and Absent: 0 case. Occupation rate of the osteophytes to the notch correlated to the preoperative varus deformity (p < 0.05). In terms of ACL, the occupation rate of the osteophytes to the notch were 22.9%, 28.8%, 46.0%, and 81.8% in Normal, Frayed, partial ruptured, and Absent, respectively. The patients with more than 40% occupation rate and less than 110 degree of knee flexion angle showed either partial rupture or absent of the ACL during the surgery. Those results correlated with the degree of OA deterioration. We conclude that occupation rate of the osteophytes to the notch poor preoperative ROM is a good predictor of evaluating the ACL degeneration in osteoarthritic knee. We also conclude that ACL dysfunction due to joint space narrowing accelerates the advancement of the knee OA.


Shinro Takai Hidemi Kawaji Norishige Iizawa

Introduction:

Although the risk of pulmonary embolism (PE) or other embolic events associated with total joint arthroplasty have been recorded for some time, to date no direct means of these events in human arthroplasty have reported. This prospective study was designed to clarify the pathophysiologic mechanism of PE after total knee arthroplasty (TKA).

Methods:

Nine patients fulfilling the following selection criteria were included in this prospective study: diagnosis of osteoarthosis, age 60 to 75 years, cemented primary TKA. All patients had a baseline pulmonary perfusion scan 2 days prior to the surgery. TKA was performed in the standard manner under general anesthesia. Monitoring of the heart chambers during the course of the TKA was performed using a 5 MHz ultrasonic transducer placed into the esophagus. The 4-chamber view plane of the heart was then imaged using a 2-dimensional echocardiography. A tip of the catheter inserted from the contralateral femoral vein was also placed in the inferior vena cava to harvest the venous blood flowed from the suffered lower extremity before and after tourniquet release. All patients had pulmonary perfusion scans 3 hours after TKA and on the 21st postoperative day. The ventilation-perfusion scan was compared with the baseline perfusion scan.


Yoshiki Takeoka Hirotsugu Muratsu Shinsuke Kihara Tomoyuki Matsumoto Nobuaki Miyaji Takashi Oshima Akihiro Maruo Hidetoshi Miya Ryosuke Kuroda Masahiro Kurosaka

Objective

The goal of total knee arthroplasty (TKA) is to achieve a stable and well-aligned tibiofemoral and patello-femoral (PF) joint, aiming at long-term clinical patient satisfaction. The surgical principles of both cruciate retaining (CR) and posterior stabilized (PS) TKA are accurate osteotomy and proper soft tissue balancing. We have developed an offset-type tensor, and measured intra-operative soft tissue balance under more physiological joint conditions with femoral component in place and reduced PF joint.

In this study, we measured intra-operative soft tissue balance and assessed the early post-operative knee joint stability quantitatively, and compared these parameters between CR and PS TKA.

Material and Method

Seventy patients with varus osteoarthritis of the knee underwent TKAs (35 CR TKAs: CR and 35 PS TKAs: PS). Mean varus deformity in standing position was 9.8 degrees in CR, and 10.7 degrees in PS (p = 0.45). All TKAs were performed by a single surgeon with measured resection technique. The external rotation of posterior femoral condyle osteotomy was performed according to surgical epicondylar axis (SEA) in pre-operative CT. We measured intra-operative soft tissue balance using an offset-type tensor with 40 lbs of joint distraction force at 0, 10, 30, 45, 60, 90, 120 and 135 degrees of flexion. The joint component gap (mm) and varus angle (degrees) were measured at each flexion angle.

Four weeks after operation, we evaluated the knee stability at extension by varus and valgus stress radiography using Telos (10 kg) and at flexion by epicondylar view with 1.5 kg weight at the ankle. We measured joint separation distance at medial as medial joint looseness (MJL) and at lateral as lateral joint looseness (LJL). Joint looseness was defined as the average of MJL and LJL.

Intra-operative measurements and post-operative joint stabilities were compared between CR and PS using unpaired t-test.


Cuneyt Tamam Johannes F. Plate Marco Andre Augart Gary Poehling Riyaz Jinnah

Introduction

Bicompartmental knee replacement (BKR) may be an alternative to total knee arthroplasty (TKA) for degenerative disease limited to two knee compartments. Most commonly, BKA is a combination of medial compartment and patellofemoral compartment resurfacing. In contrast to TKA, BKA preserves the uninvolved compartment and cruciate ligaments possibly leading to advanced stability and more physiologic knee kinematics. Robotic-assisted systems for unicompartmental knee arthroplasty have shown to provide improved component positioning with dynamic ligament balancing that may improve outcomes of BKA. The purpose of this study was to evaluate the short-term outcomes of patients undergoing BKA at a single institution by a single surgeon using a robotic-assisted system.

Methods

A search of the institution's joint registry was conducted to identify patients that underwent robotic-assisted BKA of the patellofemoral compartment and the medial or lateral compartment between December 2009 and April 2012. All medical records were analyzed for patient demographics and comorbidities. The patients were evaluated preoperatively and at 6,12 months and then annually. The patients were contacted by phone when recent follow-up was not available. The radiographic assessment was also undertaken. The orientation of the tibial and femoral implants was assessed radiologically postoperatively. We examined the clinical results with the Oxford Knee Score (OKS)


Matthew Teeter Hee-Nee Pang Richard W McCalden Douglas Naudie Steven MacDonald

Background:

Polyethylene wear in total knee arthroplasty (TKA) is influenced by patient, surgeon and implant factors. The objective of this study is to assess the effect of limb alignment, implant position and joint line position on the pattern of wear in posterior stabilized (PS) tibial inserts.

Methods:

This was a retrieval analysis of 83 PS liners collected from patients who underwent revision surgery from 1999 to 2011. Inserts were divided into 16 zones and a microscopic analysis of surface damage was carried out. We determined overall damage with a scoring system. Pre-revisions radiographs were reviewed and analyzed for correlation with the wear profile.


Matthew Teeter Amit Parikh Marc Taylor Jeff Sprague Douglas Naudie

BACKGROUND:

Implant wear continues to be a limitation of total knee replacement (TKR). Wear simulator studies are a valuable screening tool in new implant development. The purpose of this study was to determine the ability of micro-CT to prospectively measure wear in TKR implants during a wear simulator trial.

METHODS:

Three identical cruciate-retaining, fixed bearing cobalt-chromium-molybdenum (CoCrMo) on conventional EtO-sterilized polyethylene TKA implants underwent wear simulator testing up to 3.2 million cycles using gait inputs; loaded-soaks were used to correct for fluid absorption. The implants were weighed and scanned with micro-CT (at 50 micron resolution) before and after testing. The gravimetric mass was converted to volume based on the density of polyethylene. Volume change due to wear was calculated from both the gravimetric and micro-CT methods. The pre- and post-wear test micro-CT geometries were co-registered and the deviations between the two were measured.


Mark Frankle Matthew Teusink Randall Otto Benjamin Cottrell

Background:

While reverse shoulder arthroplasty (RSA) has shown successful outcomes for a variety of shoulder pathologies, postoperative scapula fractures continue to be one of the most common complications limiting outcomes with rates reported between 0.8–7.2%. Previous literature has shown that postoperative scapula fractures have a deleterious effect on elevation and outcomes scores, however these studies were all performed at short-term follow-up from the fracture. It has also not been shown whether postoperative scapular fractures increases risk of revision surgery. The purpose of this study was to determine the effect of postoperative scapula fracture on the outcomes following RSA at minimum 1 year follow-up from the fracture.

Methods:

A retrospective, case-control study of 25 nonoperatively treated postoperative scapula fractures following RSA in a single surgeon's practice was analyzed with minimum 2 year follow-up from surgery and 1 year follow-up from fracture. Patients with postoperative scapula fractures were matched 1: 4 to a control group for age, sex, total follow-up time, indication for surgery, and primary versus revision surgery. Outcome measures including revision surgery, ASES score, and change in range of motion were compared between fracture cases and controls. Radiographic features including fracture location (acromion vs. scapular spine) and healing of fracture was also analyzed with respect to outcome.


Emmanuel Thienpont

Three important objectives in knee arthroplasty are improving outcome, providing stability and obtaining correct alignment. Alignment has always been described either by anatomically measured alignment (short films, Knee Society Radiologic Score) or by mechanically measured alignment (HKA angle on long leg films). The difficulty of obtaining correct alignment in knee arthroplasty, is that as surgeons we need to find and use anatomical axes and landmarks, in the arthritic and often deformed knee, to align the implant well mechanically. Conventional instruments do the job well for 2/3 of patients, but for 1/3 we need some additional help. Navigation and patient-specific instruments (PSI) should make us more accurate surgeons.


Joyce Van Den Broeck Evie Vereecke Roel Wirix-Speetjens Jos Vander Sloten

The use of 3D imaging methodologies in orthopaedics has allowed the introduction of new technologies, such as the design of patient-specific implants or surgical instrumentation. This has introduced the need for high accuracy, in addition to a correct diagnosis. Until recently, little was known about the accuracy of MR imaging to reconstruct 3D models of the skeletal anatomy. This study was conducted to quantify the accuracy of MRI-based segmentation of the knee joint.

Nine knees of unfixed human cadavers were used to compare the accuracy of MR imaging to an optical scan. MR images of the specimens were obtained with a 1.5T clinical MRI scanner (GE Signa HDxt), using a slice thickness of 2 mm and a pixel size of 0.39 mm × 0.39 mm. Manual segmentation of the images was done using Mimics® (Materialise NV, Leuven, Belgium). The specimens were cleaned using an acetone treatment to remove soft-tissue but to keep the cartilage intact. The cleaned bones were optically scanned using a white-light optical scanner (ATOS II by GOM mbH, Braunschweig, Germany) having a resolution of 1.2 million pixels per measuring volume, yielding an accuracy of 0.02 mm. The optical scan of each bone reflects the actual dimensions of the bone and is considered as a ground truth measurement. First, a registration of the optical scan and the MRI-based 3D reconstruction was performed. Then, the optical scan was compared to the 3D model of the bone by calculating the distance of the vertices of the optical scan to the reconstructed 3D object.

Comparison of the 3D reconstruction using MRI images and the optical scans resulted in an average absolute error of 0.67 mm (± 0.52 mm standard deviation) for segmentation of the cartilage surface, with an RMS value of circa twice the pixel size. Segmenting the bone surface resulted in an average absolute error of 0.42 mm (± 0.38 mm standard deviation) and an RMS error of 1.5 times the pixel size. This accuracy is higher than reported previously by White, who compared MRI and CT imaging by looking at the positioning of landmarks on 3D printed models of the segmented images using a calliper [White, 2008]. They reported an average accuracy of 2.15 mm (± 2.44 mm) on bone using MRI images. In comparison, Rathnayaka compared both CT- and MRI-based 3D models to measurements of the real bone using a mechanical contact scanner [Rathnayaka, 2012]. They listed an accuracy of 0.23 mm for MRI segmentation using five ovine limbs.

This study is one of the first to report on the segmentation accuracy of MRI technology on knee cartilage, using human specimens and a clinical scanning protocol. The results found for both bone and cartilage segmentation demonstrate the feasibility of accurate 3D reconstructions of the knee using MRI technology.


Catherine Van Der Straeten Damien Van Quickenborne Seth Pennynck Koen De Smet Jan Victor

Background:

Potential systemic toxicity of metal ions from metal-on-metal hip arthroplasties (MoMHA) is concerning. High blood cobalt (Co) levels have been associated with neurological, cardiac and thyroid dysfunctions.

Questions/purposes:

The aim of this research was to investigate the prevalence of systemic Co toxicity in a MoMHA population, to identify confounding factors, and to indicate a Co level above which there is a high risk for systemic toxicity.


Ivor Vanhegan Melanie Coathup Ian McCarthy Fares Haddad Gordon Blunn

Introduction

Revision hip arthroplasty is a technically challenging operation as proximal bony deficits preclude the use of standard implants. Longer distally fixing stems are therefore required to achieve primary stability.

Aims

This work aims to compare the primary stability and biomechanical properties of a new design of tapered fluted modular femoral stem (Redapt®, Smith & Nephew) to that of a conical fluted stem (Restoration®, Stryker). It is hypothesized that the taper will provide improved rotational stability under cyclical loading.


Matthias Verstraete Thomas Luyckx Karel De Roo Wim Dewaele Johan Bellemans Jan Victor

Purpose

As human soft tissue is anisotropic, non-linear and inhomogeneous, its properties are difficult to characterize. Different methods have been described that are either based on contact or noncontact protocols. In this study, three-dimensional (3D) digital image correlation (DIC) was adopted to examine the mechanical behaviour of the human Achilles tendon. Despite its wide use in engineering research and its great potential for strain and displacement measurements in biological tissue, the reported biomedical applications are rather limited. To our knowledge, no validation of 3D DIC measurement on human tendon tissue exists.

The first goal of this study was to determine the feasibility to evaluate the mechanical properties of the human Achilles tendon under uniaxial loading conditions with 3D Digital Image Correlation. The second goal was to compare the accuracy and reproducibility of the 3D DIC against two linear variable differential transformer (LVDT's).

Methods

Six human Achilles tendon specimens were prepared out of fresh frozen lower limbs. Prior to preparation, all limbs underwent CT-scanning. Using Mimics software, the volume of the tendons and the cross sectional area at each level could be calculated. Subsequently, the Achilles tendons were mounted in a custom made rig for uni-axial loading. Tendons were prepared for 3D DIC measurements with a modified technique that enhanced contrast and improved the optimal resolution. Progressive static loading up to 628,3 N en subsequent unloading was performed. Two charge-coupled device camera's recorded images of each loading position for subsequent strain analysis. Two LVDT's were mounted next to the clamped tendon in order to record the displacement of the grips.


Jan Victor Farhad Tajdar Stijn Ghijselings Erik Witvrouw Catherine Van Der Straeten

Background:

The number of young patients undergoing total knee arthroplasty is rapidly increasing. Long-term follow-up of modern type implants is needed to provide a benchmark of implant longevity for these patients.

Methods:

Between January 1995 and October 1997, 245 consecutive total knee arthroplasties were performed in 217 patients by a single surgeon. In 156 knees, the Genesis I implant was used, and in 89 knees the Genesis II implant was used. Mean age at surgery was 69.3 years for the Genesis I cohort and 66 years for the Genesis II (p = 0.016). At 15 to 17 years, cumulative survivorship was calculated using Kaplan-Meier statistics whilst outcomes were rated with the ‘Knee society score’ and with the ‘Knee Injury and Osteoarthritis Outcome Score’. Radiological assessment included coronal alignment measured on full leg standing X-rays, and analysis of radiolucent lines and polyethylene thickness on AP, Lateral and Axial X-rays, positioned under fluoroscopic control.


Carlos Lavernia David Iacobelli Jesus Villa

INTRODUCTION

Computer navigation has been shown to decrease the variance of component positioning in primary THR. The cost of a navigation system in the U.S. however can exceed $200,000 in capital costs and $300–850 a case for disposables. Our objective was to assess the cost-utility of a hip navigation system.

METHODS

A review of the literature on costs and times for primary THR was done. Consecutive THR were done with an infrared navigation system. Total surgical time from incision to final skin closure and intra-operative time associated with the navigation process were recorded. Professional fees and the costs of revision surgery were estimated.


David Walker Aimee Struk Thomas Wright Scott Banks

Background:

Little is known about scapular kinematics in patients with reverse total shoulder arthroplasty (RTSA). Understanding how RTSA affects shoulder function may help refine its design, use, and rehabilitation strategies. The purpose of this study was to quantify motion in the reverse shoulder. The scapulohumeral rhythm (SHR) of the RTSA shoulder was calculated using 3d-2d image registration techniques. SHR was compared to normal subjects in literature to asses kinematic changes post RTSA.

Methods:

26 subjects were recruited for an institutional review board approved study. Subjects who were ≥ 6 months post unilateral RTSA. Subjects were prompted to do abduction in the coronal plane with and without a 3 lb. weight. Three dimensional to two dimensional image registration techniques were used to derive orientation and position measurements for the humerus and scapula from dynamic x-ray. Tukey Honest differences statistics were used to assess significance differences between groups.


Peter Walker Patrick Meere Christopher Bell

The purpose of balancing in total knee surgery is to achieve smooth tracking of the knee over a full range of flexion without excessive looseness or tightness on either the lateral or medial sides. Balancing is controlled by the alignment of the bone cuts, the soft tissue envelope, and the constraint of the total knee. Recently, Instrumented Tibial Trials (OrthoSensor) which measure and display the location and magnitude of the forces on the lateral and medial condyles, have been introduced, offering the possibly of predictive and quantitative balancing. This paper presents the results of experiments on 10 lower limb specimens, where the effects of altering the bone cuts or the femoral component size were measured.

A special leg mounting rig was fixed to a standard operating table. A boot was strapped to the foot, and the boot tracked along a horizontal rail to allow flexion-extension. The initial bone cuts were carried out by measured resection using a navigation system. The trial femoral component and the instrumented tibial trial were inserted, and the following tests carried out:

Sag Test; foot lifted up, the trial thickness chosen to produce zero flexion.

Heel Push Test; heel moved towards body to maximum flexion.

Varus-Valgus Test, AP and IXR Tests were also carried out, but not discussed here.

For an initial state of the knee, close to balanced, the lateral and medial contact forces were recorded for the full flexion range. The mean value of the contact forces per condyle was 77.4N, the mean in early flexion (0–60 deg) was 94.2N, and the mean in late flexion (60–120 deg) was 55.7N. The difference was due to the effect of the weight of the leg. One of the following Surgical Variables was then implemented, and the contact forces again recorded.

Distal femoral cut; 2 mm resection (2 mm increase in insert thickness to preserve extension)

Tibial frontal varus, 2 mm lateral stuffing

Tibial frontal valgus, 2 mm medial stuffing

Tibial slope angle increase (5 deg baseline); +2 degrees

Tibial slope angle decrease (5 deg baseline); −2 degrees

Increase in AP size of femoral component (3 mm)

The differences between the condyle force readings before and after the Surgical Variable were calculated for low and high angular ranges. The mean values for the 10 knees of the differences of the above Surgical Variables from the initial balanced state are shown in the chart.

From literature data, the mean tension increase in one collateral ligament is close to 25N/mm up to the toe of the load-elongation graph, and 50N/mm after the toe. Hence in the initial balanced state, the collateral ligaments were elongated by 2–4 mm producing pretension. From the Surgical Variables data, up to 2 mm/2 deg change in bone cuts (or 3 mm femcom change), and collateral ligament releases up to 2 mm, would correct from any unbalanced state to a balanced state.

This data provides useful guidelines for the use of the Instrumented Tibial Trials at surgery, in terms of bone cut adjustments and ligament releases.


Michael Lowry Peter Walker

In different contemporary posterior-stabilized (PS) total knees, there are considerable variations in condylar surface radii and cam-post geometry. This is expected to result in differences in kinematics and functional outcomes in patients. The hypotheses of our study were: 1. Current PS design will show symmetric motion which is different from anatomic motion, and 2. An asymmetric PS design will produce motion closer to normal anatomic motion than symmetric designs.

A special machine was constructed which could implement the ASTM standard test on constraint, by measuring the laxities. The rational for the test is to predict functional laxity ranges which will affect the kinematics in vivo. The machine set the knee at the required flexion angles and applied combinations of compressive, shear, and torque forces, to represent a range of everyday activities. The femorotibial contact points, the neutral path of motion, and the AP and internal-external laxities were used as the motion indicators. The benchmark was the motion data from anatomic knee specimens tested under the same conditions.

Four contemporary PS designs with a range of geometries was selected for the tests, together with a design where the medial side was more constrained, the lateral side was less constrained, and the post was rounded. The output motions were compared between themselves, while all designs were compared with the anatomic data. The PS designs showed major differences in motion characteristics among themselves including the neutral path of motion and the AP and rotational laxities. These differences were related to the constraints of the condyles, and the cam-post designs. The four PS designs showed motion different from anatomic, including symmetric mediolateral motion, susceptibility to excessive AP medial laxity, and reduced laxity in high flexion. The asymmetric Guided Motion design alleviated some but not all of the abnormalities; in particular, while the lateral rollback with flexion and the near-constant position of the medial femoral condyle resembled anatomic behaviour, the rotational laxity was still limited in high flexion. The latter ws observed to be due to the ‘entrapment’ of the femoral condyles between the upwards posterior lip of the tibial plastic, and the posterior of the cam-post, a phenomenon seen on all designs.

The conclusion of the study is that an asymmetric PS design may provide a path to achieving a closer match to anatomic kinematics. This may improve functional outcomes, and even provide a better ‘feel’ to the patient. However, there are still inherent challenges in PS design to closely achieve this goal. Other design configurations have also been formulated which could even more closely reproduce anatomic motion. However a pre-clinical testing method such as presented here, is one method for evaluation and can be used hand-in-hand with computational methods to produce an optimal design. The importance of the benchmark of the anatomic knee and the identification of the important parameters of the ASTM standard, notably the neutral path of motion and the laxity about the neutral path, are important aspects of the design methodology.


Simon Pearce Jason Chow William Walter

The accuracy of cup position in total hip arthroplasty is essential for a satisfactory result as malpositioning increases the risk of complications including dislocation, high wear rate, loosening, squeaking, edge loading, impingement and ultimately failure.

We studied 173 patients in a single surgeon series of matched cohorts of patients who underwent total hip arthroplasty. Four separate groups were identified comprising of posterior approach +/− navigation and direct anterior approach +/− navigation.

We found a significant difference between the direct anterior navigated group and the posterior non-navigated group for both anteversion (p < 0.05, CI −3.86 to −1.73) and inclination (p < 0.05, CI −3.08 to −1.08). 72% of anterior navigated patients fell within 5° of the navigation software set target cup position of 45° inclination and 20° anteversion and 100% were within 10°. Only 30% of posterior non-navigated were within 5° of both anteversion and inclination and 73% were within 10°.

There was also a significant difference between the direct anterior navigated and non-navigated group with respect to anteversion only (p < 0.05, CI 1.50 to 1.30). There were no other significant differences between approaches +/− navigation.

The direct anterior approach allows ease of access to both anterior-superior iliac spines for navigation and a supine patient allows anteversion and inclination to be measured in the frontal plane. We conclude that the direct anterior approach with navigation improves accuracy of cup position compared to the conventional posterior approach without navigation.


Simon Pearce William Walter Mark Gillies

The design of the femoral prosthesis in cementless total hip arthroplasty is known to affect the initial strains in the cortex during implantation and in the early postoperative time period. High strains have a direct influence on periprosthetic fracture. This study compares the existing ABGII stem, which is proximally coated with a grit blasted titanium surface with hydroxyapatite coating with a prototype that has a rougher titanium plasma spray proximal coating. The Australian National Joint registry results 2011 reported the ABG2 femoral component cumulative percent revision (CPR) of 6.5 (93.5% survival), which compares favourably with equivalent stems with 10 year CPR data such as the Taperloc 6.6 and Corail 7.3.

Six pairs of fresh-frozen cadaveric femurs were mounted in blocks according to ISO guidelines in single leg stance setup. Five strain gauges were attached around the neck of the femur and then prepared according to routine operative techniques to accept the femoral prosthesis. Cortical strains were measured during insertion of the prosthesis with an instrumented mallet attached to an accelerometer. Subsequently, force-displacement readings were taken during cyclical loading on a servo-hydraulic machine and finally the stems were tested to failure.

Our results showed significantly less strain during cyclical loading of the stem with increased surface roughness (p < 0.05). They also showed no significant differences loads/strains during impaction (p = 0.159), no significant difference in micromotion (p = 0.148) and no significant difference in load-to-failure (p = 0.37).


Selin Munir Arjuna Imbuldeniya William Walter William Walsh

Introduction

The Morse taper was adapted into orthopaedics as a connecting junction in total hip replacements. The benefit of modular systems includes the adjustment of leg length, offset and the ability to remove the head for acetabular exposure during revision surgery. The design of the Morse taper facilitates the intimate contact of the conical trunnion of the femoral stem (male component), with the conical bore of the femoral head (female component). Design consideration for tapers involve physical parameters (angle, length, diameter and contact points), and manufacturing finish (surface characteristics). Orthopaedic trunnion tapers are not standardized and vary in length, taper angle and base dimension. Variations in the design and surface characteristics of the trunnion, which directly reflects on the interface at the taper junction can influence the likelihood of subsequent wear, corrosion and ultimately effect longevity of the implant.

Methods and Materials

We studied 11 clean un-used commercial stems from five different companies (DePuy, Stryker, Biomet, Wright Medical, Smith and Nephew). Trunnion surface was scanned with an optical profilometer (Bruker ContourGT-I 3D Optical Microscope (Karlsruhe, Germany), an interference microscopes with the capability to analyse 3 dimensional topographical features of materials. Three measurements of each trunnion were taken on the anterior surface at the proximal, mid-point, and distal segments. Each region scan was conducted under a 20x objective with the scan length of 1000 um and a back scan of 500 um.


Arjuna Imbuldeniya Rishi Chana William Walter Bernard Zicat William Walter

Introduction

The success of total hip arthroplasty has meant its indications have been extended to the younger more active patient. Due to the higher activity levels and increased demands of these patients, revision rates have been traditionally higher than when compared to older patients [1]. Ceramic on ceramic bearings may offer a viable long term solution as manufacturing methods have evolved resulting in improved mechanical properties, particularly of third and fourth generation ceramics. We report the outcome of primary cementless, alumina-on-alumina hip arthroplasty with a minimum 10 year follow up in 110 patients under the age of 55 years of age at time of surgery.

Methods

A series of 120 consecutive total hip arthroplasties in 110 patients were performed between June 1997 and February 1999 by the two senior authors. All patients had an Osteonics ABC acetabular component and SecurFit or SecurFit Plus femoral component (Stryker Orthopaedics, Mahwah, NJ) with an alumina C-taper ceramic head (Biolox Forte, Ceramtec, Plochingen, Germany).


Georgi I. Wassilew Markus Heller Carsten Perka

INTRODUCTION:

Acetabular retroversion has been implicated as a risk factor for the development of early hip osteoarthritis. In clinical practice standard osseous signs such as the cross-over sign (COS) and the posterior wall sign (PWS) are widely used to establish the diagnosis of acetabular retroversion on plain radiographs. Despite standardized radiological evaluation protocols, an increased pelvic tilt can lead to a misdiagnosis of acetabular retroversion in AP radiographs and 2D MR or CT scans. Previous studies have shown that the elimination of observer bias using a standardized methodology based on 3D-CT models and the anterior pelvic plane (APP) for the assessment of COS and PWS results in greater diagnostic accuracy. Using this method a prevalence of 28% for COS and 24% for PWS has been found in a cohort of patients with symptoms indicative of FAI, however the prevalence of both signs in asymptomatic adults remains unknown. This study therefore sought to establish the prevalence of the COS and PWS in relation to the APP in an asymptomatic population using a reliable and accurate 3 D-CT based assessment.

METHODS:

A large pool of consecutive CT scans of the pelvis undertaken in our department for conditions unrelated to disorders of the hip was available for analysis. Scans in subjects with a Harris hip score of less than 90 points were excluded leaving a sample of 100 asymptomatic subjects (200 hips) for this study. A previously established 3D analysis method designed to eliminate errors resulting from variations in the position and orientation of the pelvis during CT imaging was applied to determine in order to assess the prevalence of the COS and PWS in relation to the APP. Here, the acetabuli were defined as retroverted if either the COS, PWS or both were positive.


Toshifumi Watanabe Takeshi Muneta Ichiro Sekiya Nicholas Dunbar Alex Iorgulescu Scott Banks

Introduction:

Adjusting joint gaps and establishing mediolateral (ML) soft tissue balance are considered essential interventions for better outcomes in total knee arthroplasty (TKA). However, the relationship between intraoperative laxity measurements and weight-bearing knee kinematics has not been well explored. The goal of this study was to establish how intraoperative joint gaps and ML soft tissue balance affect postoperative kinematics in posterior-stabilized (PS)-TKA.

Methods:

We investigated 44 knees with 34 patients who underwent primary PS-TKA. Subjects averaged 71 ± 7 years at the time of surgery, included 8 male and 36 female knees with a preoperative diagnosis of osteoarthritis in 38 knees and rheumatoid arthritis in 6 knees. A single surgeon performed all the surgeries with mini-midvastus approach. After independent bone cutting, soft tissues were released on a case-by-case basis to obtain ML balance. The femoral trial and a tensor were put in place, and the patella was reduced to the original position. A joint distraction force of 40 lb was applied by the tensor, and the central joint gaps and ML tilting angles were measured at 0°, 10°, 30°, 60°, 90°, 120° and 135° flexion (Fig. 1). We defined a “gap difference” as a gap size difference between one gap and another, which represents the gap change between the two knee flexion positions. ML soft tissue balance was assessed by measuring the mean joint gap tilting angle over all flexion angles for each patient. Based on the tilting angle, the 44 knees were classified into three groups: The knees with the mean joint gap tilting of less than −1.0° (13 knees), between −1.0 and 1.0° (14 knees), and over 1.0° (17 knees). At least 1.5 year after surgery, a series of dynamic squat radiographs and 3 static lateral radiographs of straight-leg standing, lunge at maximum flexion, and kneeling at maximum flexion, were taken for each patient. The 3-dimensional position and orientation of the implant components were determined using model-based shape matching techniques (Fig. 2). Correlations between intraoperative measurements and knee kinematics were analyzed. The knee kinematics was also compared among three tilting groups.


Hiroki Watanabe Yudo Hachiya Hideaki Murata Koichi Muramatsu Syoichi Taniguchi Mikihiro Kondo Kenichiro Tanaka

Introduction

Higher concentrations of metal ion levels after Metal-on-metal (MoM) THA are a cause for concern. Elevated cobalt (Co) and chromium (Cr) ion levels in the blood indicate metal wear, and may predict secondary soft-tissue damage (adverse reaction to metal debris; ARMD). Although, it is well known that concentrations of metal ion levels are elevated in the short term after MoM, the long-term consequences in ion concentration and risk factors for increased ion levels are not clarified. We sequentially investigated the postoperative Co and Cr ion levels after MoM THA and the relationship between the metal ion levels and several risk factors.

Materials and Methods

We reviewed the data on one hundred and eighty six patients of two hundred ninety one MoM THA cases. The one hundred eighty six patients were measured at least three times after a MoM THA surgery over a five year (2005–2010) period in our institution. Serum cobalt and chromium levels were measured by inductor coupled plasma – mass spectrometry at several times in follow-up period, (measured at the preoperative period, the third month, the sixth month, the first year, the second year, and the fourth year after MoM THA). Furthermore, we investigated the correlation between the metal ion levels and various factors which might influence the release of metal ions, such as Body mass index (BMI), renal function, femoral head size, unilateral or bilateral THA, the cup position, and postoperative activity. The renal function was evaluated by measuring estimated glomerular filtration ratio (GFR) at preoperative examination. A postoperative activity was assessed with a pedometer measurement counting number of steps a day. A cup position was evaluated by lateral inclination measured by X-ray or computed tomography.


Jeff Weiss Corinne E. Henak Andrew E. Anderson Christopher L. Peters

Introduction:

Most cases of hip osteoarthritis (OA) are believed to be caused by alterations in joint contact mechanics resulting from pathomorphologies such as acetabular dysplasia and acetabular retroversion. Over the past 13 years, our research group has focused on developing approaches for patient-specific modeling of cartilage and labrum in the human hip, and applying these approaches to study hip pathomorphology. The long term objective is to improve the understanding of the etiology of OA related to hip pathomorphology, and to improve diagnosis and treatment. The objectives of this presentation are to provide a summary of our subject-specific modeling approach, and to describe the results of our analysis of hips from three populations of subjects: normal, traditional dysplastic, and retroverted.

Methods:

A combined experimental and computational protocol was used to investigate contact mechanics in ten normal subjects (normal center edge angles (CEA), no history of hip pain), ten subjects with hip pain secondary to acetabular dysplasia (CEA less than 25°), and ten patients with a radiographic crossover sign, pain and clinical exams consistent with acetabular retroversion. CT arthrography was used to image cartilage and bone. Volumetric image data were segmented and discretized, and subject-specific finite element models were produced using validated methods [Fig. 1]. Boundary and loading conditions were obtained from instrumented implant and gait data. Contact mechanics were evaluated on the acetabular cartilage and labrum. Labrum contact area and peak contact stress were evaluated. Cartilage contact area, peak and average contact stress were evaluated in six anatomical regions in the acetabulum.


Jeff Weiss Andrew E. Anderson Christopher L Peters Corinne E. Henak Benjamin J. Ellis Ashley L. Kapron Michael D. Harris Christine L. Abraham Jill Erickson

This presentation will provide an overview of the interdisciplinary research program on hip pathomorphology at the University of Utah, including studies of dysplasia and femoracetabular impingement. The discussion will emphasize the implications of the research findings for hip preserving surgery


Fred Wentorf Marc Bandi Iris Sauerberg Amitkumar Mane

Introduction:

Following total knee arthroplasty, patients often complain of an unnatural feeling in their knee joint, which in turn limits their activities [Noble et al, CORR 2006]. To develop an implant design that recreates the motion of the natural knee, both the functional kinematics as well as the laxity of the joint need to be understood. In vitro testing that accurately quantifies the functional kinematics and laxity of the knee joint can facilitate development of implant designs that are more likely to result in a natural feeling, reconstructed knee. The objective of this study is to demonstrate that robotic in vitro testing can produce clinically relevant functional kinematics and joint laxities.

Methods:

All testing was performed using a KUKA (KUKA Robotics, Augsburg, Germany) 6 degree of freedom robotic arm and a six degree of freedom load cell (ATI Industrial Automation, Apex, North Carolina, USA), attached to the arm (Figure 1).

FUNCTIONAL KINEMATICS: Eight cadaveric specimens implanted with contemporary cruciate retaining implants were used for this evaluation. The functional activity, lunge, was simulated using kinematic control for flexion/extension and force-torque control for the other degrees of freedom. The inputs for the force-torque control were obtained from e-tibia data from live patients during the lunge activity [Varadarajan et al, J Biomech 2008]. At a given flexion angle, the robot moved in force-torque control to obtain the desired values within given tolerances (± 2.5N & ± 0.1 Nm). When these tolerances were met the position of femur with respect to the tibia was recorded and the knee flexed to the next level. The lunge simulation began at full extension and ended at 120 degrees of knee flexion, through 1 degree increments. The kinematic data from the contemporary CR implants were compared to in vivo kinematics of patients that were implanted with the same knee replacements performing a lunge activity [Varadarajan et al, Med Eng Phys 2009].

JOINT LAXITY: Eight native, unimplanted knees were used for this evaluation. Joint laxity of the knee joint was evaluated at 0, 30, 60, 90, and 120 degrees of knee flexion by applying various loads to the tibia and quantifying the resulting motion of the tibia. The resulting laxities were compared to various knee laxity studies in the literature.


Karl-Heinz Widmer

Introduction:

Dislocation is still one of the major complications in total hip arthroplasty. Among other factors, it is important to maximize the intended range of movement (iROM) in order to reduce the risk for prosthetic impingement and to prevent edge loading in order to avoid surface damage and squeaking. Therefore, both components should be positioned in accordance to the new combined safe-zone for correct combined version and inclination aiming for an optimal relative orientation of both components. This study shows how this optimal combined orientation of both components can be determined for a specific total hip prosthetic system and how the result can be transferred to surgery and accomplished intraoperatively using minimal-invasive stem-first technique.

Material and Methods:

829 minimal-invasive total hip arthroplasties have been performed from 2007 to 2013 in our institution. In all of these surgeries a minimal-invasive direct anterior approach (DAA) was applied. All patients were positioned supine on a proprietary orthopedic table. In 168 cases a system-specific mechanical aiming device was used intraoperatively in order to control the combined version and inclination according to the specific safe-zone by orienting the prosthetic socket in relation to the prosthetic stem. This is called “stem-first technique” meaning that the prosthetic stem dictates the orientation of the socket. It does not mean the sequence of implantation. It's specific advantage is that the stem redirects the socket if it's position is modified. It equally applies to standard, anatomic (Fig. 1) or short stems (Fig. 2). The socket orientation is not primarily referred to bony landmarks of the pelvis but to the neck of the stem. Nevertheless the surgeon has to look for sufficient fixation of the socket within the acetabular bone. Leg length was measured in the surgical field additionally and prosthetic offset was adjusted according to the preoperative planning. All other patients were operated on in our standard minimal-invasive DAA-procedure. The majority of the patients suffered from osteoarthritis, their mean age was 68 years.


Erik Woodard William Mihalko John Williams

Soft tissue balancing during Total Knee Arthroplasty (TKA) is a step every surgeon takes during surgery. Coronal and transverse plane mechanical alignment is another parameter that surgeons address during surgery in an attempt to decrease wear and increase longevity. To date, a correlation between laxity, component wear patterns, and alignment of the tibial and femoral implant components has not been established. Theoretically, suboptimal alignment and poor soft tissue balancing should increase polyethylene wear and decrease implant survivorship, contributing to implant loosening and costly revision surgeries. This study utilizes a retrieval program of functioning TKAs obtained at the time of necropsy. By utilizing CT scans, mechanical laxity testing, and polyethylene damage scores, we aimed to determine if any correlation between proper alignment and ligament balancing to polyethylene damage scores exists.

Methods:

Computed Tomography (CT) scans were performed on 17 cadaveric knees containing TKAs obtained from the Medical Education and Research Institute (Memphis TN) using a GE Brightspeed scanning system with a 1.25 mm slice thickness. Transverse slices from these scans were used to calculate the femoral and tibial component rotation for each specimen. Component rotation was determined by utilizing previously published methods (Berger et al), and component mismatch was defined as the difference in rotation angles of the femoral and tibial components. After removal of skin, subcutaneous and muscle tissue, the tibia and femur of each leg was cut transversely, and the specimens were mounted in a custom knee testing machine (Little Rock, AR). Specimens were subjected to a 10 Nm varus and valgus torque and a 1.5 Nm internal and external rotation torque. Data was continuously recorded, and the angle or displacement at each torque or force was noted. Each test was performed at full extension and 30, 60, and 90 degrees of flexion. TKA components were then removed from the cadaveric knees, cleaned of PMMA, and visually inspected for wear using a grading system with 10 wear areas on the articulating surface of the polyethylene tibial insert (Hood et al). Scores were assigned based on severity of 7 different degradation characteristics, and were separated based on medial or lateral compartment. The maximum possible total score was 210 for each knee.

Results:

The average length of TKA implantation was 10 years. The coronal angle at +10 Nm (varus) moment ranged from 5 to 12 degrees, while the angle under a −10 Nm (valgus) moment ranged from 7 to 11 degrees across 10 specimens. The average component rotational mismatch was 20.5 degrees. The average overall medial wear score was 8.8, while the lateral average was 9.6. Wear scores showed a higher correlation to laxity in the medial compartment than the lateral side (Figures 1 and 2).


Christopher Roche Pierre Henri Flurin Yann Marczuk Thomas Wright Joseph Zuckerman

Introduction

Both anatomic (aTSA) and reverse (rTSA) total shoulder arthroplasty are the standard of care for various end-stage degenerative conditions of the glenohumeral joint. Osteoarthritis (OA) is the most common indication for aTSA while Rotator Cuff Tear Arthropathy (CTA) is the most common indication for rTSA. Worldwide, the usage of both aTSA and rTSA has increased significantly due in part, to the predictability of acceptable outcomes achieved with each prosthesis type. The aim of this study is to quantify outcomes using 5 different metrics and compare results achieved for each indication using one platform total shoulder arthroplasty system which utilizes the same humeral component and instrumentation to perform both aTSA or rTSA.

Methods

200 patients (70.9 ± 7.3 yrs) were treated by two orthopaedic surgeons using either aTSA or rTSA. 73 patients received aTSA (67.4 ± 8.0 yrs) for treatment of OA (PHF: 64 patients; YM: 9 patients) and 127 patients received a rTSA (72.9 ± 6.1 yrs) for treatment of CTA (PHF: 53 patients; YM: 74 patients). These patients were scored pre-operatively and at latest follow-up using the SST, UCLA, ASES, Constant, and SPADI metrics; active abduction, forward flexion, and external rotation were also measured. The average follow-up for all patients was 31.4 ± 9.7 months (aTSA: 32.5 ± 12.1 months; rTSA: 30.8 ± 8.0 months). A Student's two-tailed, unpaired t-test was used to identify differences in pre-operative, post-operative, and pre-to-post-operative improvements in results, where p < 0.05 denoted a significant difference.


Timothy Wright Joseph Lipman

Introduction

The design and manufacture of patient specific implants at Hospital for Special Surgery (HSS) was started in the fall of 1976. The first implant designed and manufactured was an extra large total knee. This effort expanded to include all arthroplasty devices including hips, knees, shoulders and elbows along with fracture fixation devices. In the 1980s, the hospital was designing and manufacturing over 100 custom implants per year. This reduced significantly in the 1990s due to the introduction of modular total knee replacements. In 1996, HSS ceased manufacture due to rising costs and a greater regulatory burden. However, implants are still designed at HSS with manufacturing outsourced to commercial companies. Since 1976, the hospital has designed over 2500 implants.

Patient Population

Currently, we design implants for ∼30 cases per year, hips, knees, and upper extremity devices (mainly elbow). We've seen an increase in acetabular revision cases over the last few years and now design about 10 revision acetabular components each year.


Chandra Shekhar Yadav Ashok Kumar Sumit Banerjee Samarth Mittal Vivek Shankar

Background:

Role of intra-articular Tranexamic acid in total knee replacement arthroplasty

Materials and methods

Prospective evaluation was done to see the effect of intra-articular Tranexamic acid on blood loss in 60 patients (120 knees) undergoing total knee arthroplasty. All the patients were operated by one surgeon with same technique by using same implants. Patients were randomly injected 1500 mg/20 ml of Tranexamic acid on one side of the knee only. Nothing was injected on the contra lateral knee. Evaluation was done for swelling and the amount of blood loss in the drain.


Jin Yamaguchi Teruo Terashima

[Introduction]

Total hip arthroplasty (THA) markedly improves pain, gait, and activities of daily living for most patients with osteoarthritis. However, pelvic osteotomy has been recommended for young and active patients with hip dysplasia, because THA in that population is associated with high rates of revision THA. The rotational acetabular osteotomy (RAO) of Ninomiya and Tagawa, and the eccentric rotational acetabular osteotomy of Hasegawa for hip dysplasia reportedly are successful in young and active patients. However, even after the surgery of RAO, osteoarthritis developed in some cases and leaded to the conversion to THA. The differences of bone quality of acetabulum have been reported between at the surgery of THA after RAO and at the surgery of primary THA. We should not discuss the results of these two THA equally. The purpose of this study is to report the results of THA after RAO.

[Patients and Methods]

We retrospectively reviewed 33 patients (37 hips) treated by total hip arthroplasty after rotational acetabular osteotomy between 1992 and 2012. Five cases were performed RAO with valgus osteotomy. At the time of THA surgery, the overall mean age of the patients was 57.5 years (range, 39–72 years). The average of follow-up period was 7.0 years (range, 8–258 months). One surgeon (TT) evaluated the hips clinically using the Japanese Orthopaedics Association (JOA) score. The radiographic measurements were performed by the other physician (JY) blinded to the clinical scores. Radiographical examination was performed using AP X-ray. We evaluated the presence of osteolysis and loosening of the implants. We evaluated the stability of stem implants using Engh classification and of cup implants using Hodgkinson classification.


Richard Komistek William Hamel Matthew Young Ian Zeller Trevor Grieco Adrija Sharma

INTRODUCTION:

Stationary fluoroscopy has been a viable resource for determining in vivo knee kinematics, but limitations have restricted the use of this technology. Patients can only perform certain normal daily living activities while using stationary fluoroscopy and must conduct the activities at speeds that are slower than normal to avoid ghosting of the images. More recently, a Mobile Tracking Fluoroscopic (MTF) unit has been developed that can track patients in real-time as he/she performs various activities at normal speeds (Figure 1). Therefore, the objective of this study was to compare in vivo kinematics for patient's evaluated using stationary and mobile fluoroscopy to determine potential advantages and disadvantages for use of these technologies.

METHODS:

The MTF is a unique mobile robot that can acquire real-time x-ray records of hip, knee, or ankle joint motion while a subject walks/manoeuvres naturally within a laboratory floor area. By virtue of its mechanizations, test protocols can involve many types of manoeuvres such as chair rises, stair climbing/descending, ramp crossing, walking, etc. Because the subjects are performing such actions naturally, the resulting fluoroscope images reflect the full functionality of their musculoskeletal anatomy. Patients in the study were initially fluoroscoped using a stationary unit and then using the MTF unit.


Yixin Zhou

Background:

The origin of a valgus deformity affects the algorithmic and individualized approach used in total knee arthroplasty in valgus knees. We developed a new physical examination technique, the swing test, to evaluate whether valgus malalignment is present when the knee flexes.

Methods:

We performed the swing test on 44 valgus knees in 44 consecutive patients, and we conducted traditional malalignment analysis on each patient's long-film radiographs and computed tomography images to evaluate origin of valgus deformity. We did a diagnostic test to compare the results of the swing test with those of traditional malalignment analysis.


The Q Angle Is Dynamic Pages 213 - 213
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Yixin Zhou

Background

The Q angle is an index of the vector of combined pull of the quadriceps and the patellar tendon. However, the Q angle is traditionally measured with the knee extended and static. The indexation of the Q angle measured using the traditional method therefore is questionable.

Questions/purposes

We asked if the Q angle would change when the knee flexed; if it did change, how it changed; and if it changed with different patterns in females and males.


Abdellatif Abdelgaied Claire Brockett Feng Liu Louise Jennings Zhongmin Jin John Fisher

Introduction:

Backside wear has been previously reported through in-vitro and in-vivo to have a significant contribution to the total wear in rotating bearing TKRs.

The present study investigated the contribution of backside wear to the total wear in the PFC Sigma rotating platform mobile bearing TKR. In addition, the wear results were compared to the computed wear rates of the PFC Sigma fixed bearing TKR, with two different bearing materials.

Materials and Methods:

The commercially available PFC Sigma rotating platform mobile bearing and PFC Sigma fixed bearing total knee replacements, size 3 (DePuy, UK) were tested, with either conventional or moderately cross-linked (5 MRad) GUR1020 UHMWPE bearing materials. The computational wear model for the knee implants was based on the contact area and an independent experimentally determined non-dimensional wear coefficient [1,2,3].

The experimental wear test for the mobile bearing was force controlled using the ISO anterior-posterior force (ISO14243-1-2009). However, due to time limitation of the explicit simulation required to run the force controlled model, the simulation was run using the AP displacements taken from the experimental knee simulator which was run under the ISO AP force. The Sigma fixed bearing TKR was run under high level of anterior-posterior displacements (maximum of 10 mm).


Ali Abdulkarim Anas Elsibaei Bob Jackson Danial Riordan

Introduction

Many surgeons are familiar with the audible change in the sound pitch while hammering a rasp in a long bone during surgeries like Hip Arthroplasty. We have developed a hypothesis indicating that there is a relationship between that sound change and the development of micro-fracture and subsequently full fracture.

Methods

An experiment using porcine femur bone performed by attaching a bone conduction microphone to the distal part of the bone while hammering a rasps of different sizes through the medullary canal till the point where a fracture developed. The transduce sound resonances created in the bone during rasping are converted to an analogue electrical signals that were sent to a Zoom H4n handheld recording device which recorded the signal to a disk.

The recorded signals subsequently were analysed using Matlab software and a spectrum analyzer using Fast Fourier Transforms (FFT).


Ali Abdulkarim Prasad Ellanti Nicola Motterlini Thomas Fahey J M O'Byrne

The optimal method of fixation for primary total hip replacements (THR), particularly fixation with or without the use of cement is still controversial.

In a systematic review and meta-analysis of all randomized controlled trials (RCT) comparing cemented versus uncemented THRS available in the published literature, we found that there is no significant difference between cemented and uncemented THRs in terms implant survival as measured by the revision rate.

Better short-term clinical outcome, particularly an improved pain score can be obtained with cemented fixation. However, the results are unclear for the long-term clinical and functional outcome between the two groups. No difference was evident in the mortality and the post operative complication rate. On the other hand, the Radiographic findings were variable and do not seem to correlate with clinical findings as differences in the surgical technique and prosthesis design might be associated with the incidence of osteolysis.

We concluded in our review that Cemented THR is similar if not superior to uncemented THR, and provides better short term clinical outcomes. Further research, improved methodology and longer follow up are necessary to better define specific subgroups of patients in whom the relative benefits of cemented and uncemented implant fixation can be clearly demonstrated.


Ali Abdulkarim Nicola Motterlini TM ODonnell MJ Neil

Introduction

Unicompartmental knee arthroplasty (UKA) is a recognized procedure for treatment of medial compartment osteoarthritis. Patellofemoral (PF) joint degeneration is widely considered to be a contraindication to medial unicompartmental knee replacement. We examined the validity of this preconception using information gathered prospectively on consecutive patients who underwent UKA using the Repicci II® UKA prosthesis for medial compartment osteoarthritis.

Methods

We prospectively collected data on 147 consecutive patients who underwent the Repicci II® UKA for medial compartment osteoarthritis. All operations were performed between July 1999 and September 2000 by the same surgeon. The status of the PF joint was assessed intra-operatively in all patients, and accordingly patients were divided into two groups, one group with a normal PF joint, and the second group with degenerative changes of the PF joint.

Variables measured for outcome included the International Knee Society (IKS) score, limb alignment, and range of motion. Radiographs were assessed for progression of disease or failure of implant. The mean follow-up was 9.4 years (range: 5–10.7 years).

Patients were reviewed initially at 2 weeks, and then at 6 months post-operatively. They were subsequently reviewed on an annual basis. All patients completed an IKS score preoperatively and at last follow-up. Age, gender, BMI, length of hospital stay, perioperative complications, all subsequent surgery, including revision of the prosthesis, and survivorship at 10 years was recorded, and results of the 2 groups compared.


Satomi Abe Hitoshi Nochi Hiroshi Kobayashi Takuya Ruike Hiroshi Ito

Introduction

Malrotation of the femoral component is a cause of patellofemoral maltracking after total knee arthroplasty. We have developed a balanced gap technique in posterior stabilized total knee arthroplasty using an original instrument. Patellar instability is associated with an increased the tibial tubercle and the center of the groove (TT-TG) distance > 20 mm, and TT-TG is regarded as one index of a factor influencing congruity. To assess the influence on a patellofemoral joint by a modified gap technique, the purpose of this study is to compare the TT-TG distance before surgery and after total knee arthroplasty.

Material and Methods

We explored the 30 knees, 25 patients (4 male and 21 female), who underwent total knee arthroplasties (NexGen LPS-Flex, fixed surface, Zimmer; Warsaw, USA) for osteoarthritis or rheumatoid arthritis. All procedures were performed through a medial parapatellar approach and a balanced gap technique used a developed versatile tensor device. We compared the preoperative and postoperative CT at a knee flexion angle of 30 degrees. To assess the force vector of the extensor mechanism, TT-TG distance and the proximal-distal distance between the entrance of the tracheal groove and the tibial tubercle (ET-TT distance) were measured in CT. The relation of both distances (TT-TG index) that divided TT-TG in ET-TT was calculated, because the TT-TG distance was affected by the individual knee size. Three dimensional Q-angle (θ) was also calculated using TT-TG distance and ET-TT distance, sinθ = TT-TG distance/ET-TT distance. (Figure 1)


Michael Kurdziel Jeffrey Ackerman Meagan Salisbury Erin Baker James John Verner

Purpose:

Acetabular bone loss during revision total hip arthroplasty (THA) poses a challenge for reconstruction as segmental and extensive cavitary defects require structural support to achieve prosthesis stability. Trabecular metal (TM) acetabular augments structurally support hemispherical cups. Positive short-term results have been encouraging, but mid- to long-term results are largely unknown. The purpose of this study was to determine the continued efficacy of TM augments in THA revisions with significant pelvic bone loss.

Methods:

Radiographs and medical records of 51 patients who had undergone THA revision with the use of a TM augment were retrospectively reviewed. Acetabular defects were graded according to the Paprosky classification of acetabular deficiencies based on preoperative radiographs and operative findings. Loosening was defined radiographically as a gross change in cup position, change in the abduction angle (>5°), or change in the vertical position of the acetabular component (>8 mm) between initial postoperative and most recent follow-up radiographs (Figure 1).


Aditya Aggarwal Soumya Chakraborty Ajay Bahl

Patients with symptomatic osteoarthritis of the knee are typically obese and relatively less active and may be associated with cardiovascular deconditioning and increased risk of heart disease. Purpose of this study was to evaluate the impact of the total knee arthroplasty upon cardiovascular status of the patient, as indicated by assessment of the endothelial function and correlation of the same with the functional outcome. Endothelial function has been found to correlate with the cardiovascular health of an individual closely and therefore was chosen as a noninvasive means to study the same. This study was conducted prospectively in 34 patients of advanced Osteoarthritis of knee joint (11 males, 23 females) who underwent unilateral (25) or bilateral (9) total knee arthroplasty at a mean age of 59.2 + 9.7 years (range 40–77 years). All the patients underwent preoperative assessment of endothelial function by the method of flow mediated dilatation (FMD). We report the results at 2 to 3.5 years (mean, 3.0) follow-up. The reassessment of the endothelial function and functional outcome in terms of Knee society score were performed at follow up. We noted excellent improvement in Knee society score (mean 102.3 + 22.9 at 6 months, 152.5 + 19.8 at 18 months and 174.4 + 17.3 at 42 months compared to 65.4 + 30.3 preoperatively). There was good improvement in endothelial function at 6 months (29.98 + 19.28%) and excellent improvement (69.87 + 35.57%) at 18 months and (85.65 + 26.14%) at 42 months respectively. Significant improvement in endothelial function can result following total knee arthroplasty.


Aditya Aggarwal Shashikanth VS Neelam Marwaha

Background:

Blood loss, pain and wound healing contribute significantly to the perioperative morbidity after total knee arthroplasty. Prospective randomized controlled studies are lacking, to our knowledge. The purpose of this study was to determine whether platelet rich plasma (PRP) might prevent blood loss and postoperative pain and expedite wound healing following TKA.

Methods:

Forty consecutive age, sex and BMI-matched patients who had unilateral or bilateral arthritis of the knee with similar deformity and preoperative range of motion were enrolled for this prospective randomized controlled double blinded clinical trial. Preoperative haemoglobin, range of motion, WOMAC and KSS scores were noted. Platelet-rich plasma was applied over the wound including the capsule, medial and lateral recesses in seventeen patients. Twentythree served as controls. Postoperative haemoglobin, blood loss, blood transfusion, VAS score, Wound score, KSS and WOMAC score were recorded and evaluated.


Alberto Agueci Cesare Mariani

The Authors present a ligament tensor for the evaluation of the ligaments balance used during the implant of total knee prosthesis, which is able to suggest the orientation of the bone resection, not only in knee flexion, but also in extention. This instrument provides for the placement of the endomedullary rod equipped (figures 1 and 2) with a plate of various valgus levels on which, the balancing part of the tensor, is pushing against, while the stable part is leaning against the tibial resected surface (figure 3).

This system allows to choose the right valgus level, without having to recur to the ligamentous lysis, if so only minimum, and above all, allows this way to aviod the error of orienting the distal femoral resection due to the imperfect coaxiality between the endomedullary rod and the femoral canal. This mistake might happen because of the imperfect point of entrance and/or because of a not so small difference between the rod caliber and the femoral canal width.


Tjarco Alta Lauryl Decroocq Gregory Moineau Nicolas Brassart Luc Favard Francois Sirveaux Philippe Clavert Pascal Boileau

BACKGROUND:

Bony healing of tuberosities around shoulder prostheses is difficult to obtain in the elderly patient. We hypothesized that reattachment of the tuberosities, performed in combination with bone grafting, around a specific reverse shoulder fracture-prosthesis (RSFP) would favour improved tuberosity healing and shoulder mobility in elderly patients with displaced proximal humerus fractures.

METHODS:

We included 49 patients (50 shoulders)(45 female, 4 male) in this prospective study. Mean (± SD) age 80 ± 4 years (range, 70–88). Clinical evaluation consisted of ROM, VAS (pain), Constant scores, patient satisfaction (Subjective Shoulder Value (SSV)) and noted complications. Radiological evaluation consisted of tuberosity healing and component loosening. Mean follow-up 18 ± 8 months (12–39).


Tjarco Alta Nicolas Morin-Salvo Charles Bessiere Pascal Boileau

BACKGROUND:

Bony increased-offset reverse shoulder arthroplasty (BIO-RSA) creates a long-necked scapula, providing the benefits of lateralization. Experience with allogenic bone grafting of the glenoid in shoulder arthroplasty is mainly based on its use with total shoulder arthroplasty (TSA). Therefore, our study objectives were: 1) verify if the use of BIO-RSA together with glenoid surface grafting with allogenic bone would provide similar benefits (clinical and functional) as found with autologous bone, 2) determine if allograft could be a good alternative in the absence of (good quality) autograft bone, and 3) to see if the allograft would incorporate with the native glenoid bone.

METHODS:

We included 25 patients (19 female, 6 male) in this prospective study. Indications for BIO-RSA were: fracture sequalle (n = 9), revisions (n = 11), 4-part humerus fracture (n = 1), rheumatoid arthritis (n = 1) and cuff tear arthropathy (CTA) with poor humeral head bone quality/osteonecrosis (n = 3). Mean (± SD) age 70 ± 11 years (range, 44–86). Clinical evaluation consisted of ROM, Constant scores, patient satisfaction (Subjective Shoulder Value (SSV)) and noted complications. Radiographic and CT scan evaluation consisted of bone graft healing, bone graft resorption/lysis, glenoid component loosening, inferior scapular notching, spur formation and anterior/posterior scapular notching. Mean follow-up was 34 ± 10 months (24–62).


Tjarco Alta Nicolas Morin-Salvo Charles Bessiere Gregory Moineau Pascal Boileau

Introduction:

Lateralization of reversed shoulder arthroplasty provides improvement in range of motion and decreases inferior scapular notching. The purpose of this study was to verify if the autologous cancelous bone graft harvested from the humeral head does heal constantly in a large cohort of patients followed for a long time

Methods:

Cohort of 92 consecutive patients operated between 2006 and 2010 with a BIORSA for definitive shoulder pseudoparalysis, secondary to cuff tear arthropathy (CTA) or massive, irreparable cuff tear (MCT). The autogenous cancelous graft was harvested from humeral head in all cases. Eight patients were lost for follow up, and four died before 2 years. The remaining 80 patients underwent clinical, radiographic and CT assessment at a minimum FU of 24 months. Mean age was 73 years. Three independent observers evaluated notching, partial or total glenoid or humeral loosening and viability of the graft. Constant-Murley score, range of motion and subjective shoulder value (SSV) were recorded. The mean follow up was 39 months (range 24–74 months).


Derek Amanatullah Paul E DiCesare Patrick Meere Gavin Pereira

Incorrect registration during computer assisted total knee arthroplasty (CA-TKA) leads to malposition of implants. Our aim was to evaluate the tolerable error in anatomic landmark registration. We incorrectly registered the femoral epicondyles, femoral and tibial centers, as well as the malleoli and documented the change in angulation or rotation. We found that the distal femoral epicondyles were the most difficult anatomic landmarks to register. The other bony landmarks were more forgiving. Identification of the distal femoral epicondyles has a high inter- and intra-observer variability. Our observation that there is less than 2 mm of safe zone in the anterior or posterior direction during registration of the medial and lateral epicondyles may explain the inability of CA-TKA to improve upon the outcomes of conventional TKA.


Derek Amanatullah Matthew Lopez Michael Alaia Kenneth Montini Paul DiCesare Gavin Pereira

Restoration of the joint line of the knee during primary and revision total knee arthroplasty is one of many critical steps that directly influence patient outcomes. Fifty MRI scans of normal atraumatic knees were analyzed to determine a quantitative relationship between the joint line of the knee and the bony landmarks of the knee joint: femoral epicondyles, metaphyseal flare of the femur, tibial tubercle, and proximal tibio-femoral joint. We describe the relationship of these six anatomic landmarks about the knee in a gender and size independent manner. This description supports a simple three-step algorithm allowing orthopaedic surgeons to calculate, instead of estimate, the location of the joint line of the knee.


Wataru Ando Kengo Yamamoto Tsuyoshi Koyama Kazumasa Fudo Takashi Tsujimoto Masaharu Aihara Kenji Ohzono

Metal on metal total hip arthroplasty provides the potential improvement in articular wear and the use of large-diameter femoral heads following the prospect for reduction in the risk of dislocation. The purpose of this study was to compare the clinical and radiographic outcomes as well as serum metal ion level between the two different component designs with small and large femoral heads in metal on metal total hip arthroplasty.

We studied 39 patients with large head (Magnum®, Biomet; cup size minus 6 mm) and 37 patients with small head (M2a taper®, Biomet; 28 or 32 mm head) of metal on metal total hip arthroplasty between December 2009 to October 2011 with follow-up of 2.1 years (1.0–3.3 years) after surgery. Harris Hip Score, UCLA activity score, EQ-5D, radiographic assessment, and serum cobalt and chromium ion levels were evaluated.

Harris Hip Score, UCLA activity score, and EQ-5D were improved after surgery in small and large head groups, however, no significant differences were observed between both groups. Cup inclination was below 50 degree in all prosthesis. No loosening and no osteolysis were observed. Cobalt and chromium ion was not detected before surgery; however, metal ion levels of both groups were increased after surgery in time dependent manner. There was no significant difference between two groups at one year after surgery. One patient in each group showed the increase of cobalt ion level over 7 ppb (15.4 ppb, 12.9 ppb) without any clinical symptom including pain. Cup inclination was 29 degree in both patients and cup anteversion was 38 and 41 degree, respectively.

There was no significant difference of ion levels between both groups. No dislocation was observed in large head group while one dislocation occurred in small head group. No patients required the revision surgery.

This metal on metal component, especially with large femoral heads, showed the good clinical results at the maximum follow up of 3.3 year after surgery. However, the ion level of two patients increased over 7 ppb and longer follow-up will be needed.


Laurent Angibaud Xeve Silver Scott Gulbransen Bernard Stulberg

Introduction

From pre-operative planning to final implant cementation, total knee arthroplasty (TKA) can be defined by a succession of individual steps, each presenting potential errors that can result in devices being implanted outside the desired range of alignment.

Our study used an image-free computer-assisted orthopedic surgery (CAOS) guidance system (Exactech GPS, Blue-Ortho, Grenoble, FR) to evaluate alignment discrepancies occurring during different steps of a typical TKA procedure.

Materials and methods:

A surgical profile was established to define resection parameters and steps for proximal tibial and distal femoral cuts (see Figure 1A) to be made on seven synthetic knee models (MITA, Medical Models, Bristol, UK). First, the guidance system was used to acquire pre-identified landmarks. Next, a cutting block was adjusted to match the resection targets and then fixed to the bone using locking pins. Bone cuts were performed and then checked. Data was collected from the guidance system at three steps: (1) cutting block adjusted but not pinned to bone (see Figure 1B), (2) cutting block adjusted and pinned to bone (see Figure 1C), and (3) after checking cuts (see Figure 1D). These data were then compared to the resection target parameters to assess potential discrepancies.


Ayman Bassiony Mohamed Kamal Asal

Failure of the femoral component after a primary or revision THA is commonly associated with some degree of femoral bone loss. Depending on the quantity and quality of the remaining host bone, femoral stem revision can be challenging.

Twenty patients with severe proximal femoral bone loss due to prosthetic loosening were treated by Wagner cementless self-locking revision stems with a mean follow up of 24 months (range 18–36 months). The indication of revision surgery was aseptic loosening in 16 patients and septic loosening in 4 cases.

At the end of the follow up the mean Harris hip score increased from 35 to 86 points. Definite radiographic evidence of bone regeneration in the bony defects was achieved within 3 months in all patients.

Implantation of a Wagner cementless selflocking revision stem provided satisfactory results. The Wagner SL Revision prosthesis, firmly and rotationally stable fixed in the medullary cavity of the healthy bone distal from the original prosthetic bed, with its conical longitudinal ribs and cementless anchorage, bridges the defective prosthetic bed and hereby leads to a condition of relative mechanical stability. With time, there is active ossification in the old prosthetic bed, replacing lost bone.


Anouska Ayub Toby Richards Fares Haddad

AIM:

Preoperative anemia in patients undergoing elective total knee arthroplasty has been associated with increased allogeneic blood transfusion therapy and increased rates of in hospital morbidity, which often leads to a longer length of hospital stay. We measured the prevalence of anaemia among patients attending pre-admission clinic before elective major joint arthroplasty.

METHODS:

Retrospectively, a randomized sample of all patients undergoing total hip arthroplasty between Dec 2009 and June 2010 were included. The computerized laboratory results were analysed for anaemia as defined by the local reference range (<11.5g/dL for females, <13g/dL for males). Patients were reviewed 6 weeks post operatively and range of flexion and extension was documented.


Yusuke Baba Keitaro Yamamoto Daisuke Maruyama Tomohiro Sugimoto Seiji Nakagawa Yoshio Nakashima

Background:

Total knee arthroplasty (TKA) has achieved excellent clinical outcomes and functional performances. However, younger and Asian patients require even greater implant longevity and higher flexion. It is necessary for much further functional upgrading to design TKA with mobility and stability. Therefore, we determined the relationship between mobility and stability of TKA.

Methods:

We evaluated the force of constraint of femorotibial surfaces in two types of designs in order to measure the property of femorotibial surfaces. The anatomical geometry knee (AGK) has an asymmetrical design, which restores the anatomical jointline in both sagittal and coronal planes, and is expected to permit normal kinematics, with cruciate-retaining fixed type. The functional designed knee (FDK) has a symmetrical design, and enhances concave femorotibial surfaces with cruciate-retaining mobile type.

We performed mechanical tests to measure the force of constraint regarding anterior-posterior (AP) and internal-external (IE) rotational direction in extension position, 90-degree flexion and a maximum flexion of 140-degree. The force load to AP direction of tibial tray was measured when the femoral component moved plus or minus 10 millimeters. The moment load to IE rotational direction of tibial tray was measured when the femoral component moved plus or minus 20 degrees. The vertical load of 710N has been loaded on the femoral component during this test.


Mamadou Bah Junfen Shi Martin Browne Yanneck Suchier Fabien Lefebvre Philippe Young Leonard King Doug Dunlop Markus Heller

This work was motivated by the need to capture the spectrum of anatomical shape variability rather than relying on analyses of single bones. A novel tool was developed that combines image-based modelling with statistical shape analysis to automatically generate new femur geometries and measure anatomical parameters to capture the variability across the population. To demonstrate the feasibility of the approach, the study used data from 62 Caucasian subjects (31 female and 31 male) aged between 43 and 106 years, with CT voxel size ranging 0.488 × 0.488 × 1.5 mm to 0.7422 × 0.7422 × 0.97 mm.

The scans were divided into female and male subgroups and high-quality subject-specific tetrahedral finite element (FE) meshes resulting from segmented femurs formed the so-called training samples. A source mesh of a segmented femur (25580 nodes, 51156 triangles) from the Visible Human dataset [Spitzer, 1996] was used for elastic surface registration of each considered target male and female subjects, followed by applying a mesh morphing strategy.

To represent the variations in bone morphology across the population, gender-based Statistical Shape Models (SSM) were developed, using Principal Component Analysis. These were then sampled using the principal components required to capture 95% of the variance in each training dataset to generate 1000 new anatomical shapes [Bryan, 2010; Blanc, 2012] and to automatically measure key anatomical parameters known to critically influence the biomechanics after hip replacement (Figure 1).

Analysis of the female and male training datasets revealed the following data for the five considered anatomical parameters: anteversion angle (12.6 ± 6.4° vs. 6.2 ± 7.5°), CCD angle (124.8 ± 4.7° vs. 126.3 ± 4.6°), femoral neck length (48.7 ± 3.8 mm vs. 52 ± 5 mm), femoral head radius (21.5 ± 1.3 mm vs. 24.9 ± 1.5 mm) and femur length (431.0 ± 17.6 mm vs. 474.5 ± 26.3 mm). However, using the SSM generated pool of 1000 femurs, the following data were computed for females against males: anteversion angle (10.5 ± 14.3° vs. 7.6 ± 7.2°), CCD angle (123.9 ± 5.8° vs. 126.7 ± 4°), femoral neck length (46.7 ± 7.7 mm vs. 51.5 ± 4.4 mm), femoral head radius (21.4 ± 1.2 mm vs. 24.9 ± 1.4 mm) and femur length (430.2 ± 16.1 mm vs. 473.9 ± 25.9 mm).

The highest variability was found in the anteversion of the females where the standard deviation in the SSM-based sample was increased to 14.3° from 6.4° in the original training dataset (Figures 2 & 3). The mean values for both females (10.5°) and males (7.6 °) were found close to the values of 10° and 7° reported in [Mishra, 2009] in 31 females and 112 males with a [2°, 25°] and [2°, 35°] range, respectively.

Femoral neck length of the female (male) subjects was 47.3 ± 6.2 mm (51.8 ± 4.1 mm) compared to 48.7 ± 3.8 mm (52 ± 5 mm) in the training dataset and 63.65 ± 5.15 mm in [Blanc, 2012] with n = 142, 54% female, 46% male and a [50.32–75.50 mm] range. For the measured CCD angle in both female (123.9 ± 5.8°) and male (126.7 ± 4°) subjects, a good correlation was found with reported values of 128.4 ± 4.75° [Atilla, 2007], 124.7 ± 7.4° [Noble, 1988] and 129.82 + 5.37° [Blanc, 2012].

In conclusion, the present study demonstrates that the proposed methodology based on gender-specific statistical shape modelling can be a valuable tool for automatically generating a large specific population of femurs to support implant design and planning of femoral reconstructive surgery.


Christopher Barr A Nebergall Donna Scarborough Gavin Braithwaite Young-Min Kwon Harry E Rubash Orhun Muratoglu Henrik Malchau

Introduction:

Acetabular cup position is an important factor in successful total hip arthroplasty (THA). Optimal cup placement requires surgeons to possess an accurate perception of pelvic orientation during cup impaction, however, varying pelvic anatomy and limited visual cues in the surgical field may interfere with this process. The purpose of this study was to evaluate the utility of an inertial measurement unit (IMU) in monitoring pelvic position during THA.

Materials & Methods:

Ten patients scheduled to undergo THA were IRB-approved and consented by four surgeons. A small IMU was placed over the patient's sacrum pre-operatively and zeroed in standing position. Pelvic orientation data was streamed and captured wirelessly throughout the procedure. Surgeons were blinded to all data throughout the study period. Prior to cup impaction, the surgeon indicated his intended cup abduction angle and the degree to which the cup impactor was manipulated to compensate for perceived AP pelvic tilt. The degree of pelvic tilt as determined by the IMU (angle β) was then recorded (Figure 1). AP-pelvis radiographs were measured in Martell Hip Analysis Suite post-operatively to calculate the cup abduction angle, which was then compared to the surgeon's intended abduction angle to determine surgeon accuracy. To predict the final cup abduction angle, the degree of pelvic tilt recorded by the IMU (angle β) was subtracted from the abduction angle of the cup impactor (angle α) that was positioned using the OR table as a reference (Figure 1). This value was then compared to the measured post-operative cup abduction angle in order to assess the accuracy of the IMU in measuring pelvic tilt. Surgeon accuracy and IMU accuracy were compared to determine if the IMU was more or less effective than surgeon perception at determining pelvic tilt.


Jane Liu Travis Small Jessica Masch Andrew Goldblum Alison Klika Wael Barsoum

Introduction:

While indications for total knee (TKA) and hip arthroplasty (THA) have expanded over the last 35 years, implant labeling has largely remained stagnant, with conditions including obesity, developmental dysplasia, and many others (Table 1) still considered as contraindications. Implant labeling has not co-evolved with surgical indications, as most orthopaedic implants are cleared through the 510(k) process, which conserves the labeling of the predicate device. While surgeons can legally use devices for off-label indications, the scrutiny regarding off-label use of orthopaedic implants has intensified. The objective of this study was to determine the incidence of off-label use at our institution, define the risk in terms of revision rate associated with off-label use, and to compare activity level, functional outcomes, and general health outcomes for on- and off-label TKA and THA patients.

Methods:

Patients who underwent primary TKA or THA at a large academic tertiary referral center between January 1, 2010 and June 30, 2010 were considered for the study (n = 705). Of this cohort, a convenience sample of 283 patients were selected for the study based on the presence of baseline outcomes data. Patients were contacted via mail and/or phone to collect details regarding potential revision surgeries, UCLA activity scores, short form-12 (SF-12), Knee Injury and Osteoarthritis Outcome Score (KOOS) or Hip Disability and Osteoarthritis Outcome Score (HOOS). Using labeled contraindications from the product inserts from multiple orthopaedic implant manufacturers, procedures were categorized as on-label or off-label. Outcomes including revision rate, activity score, and SF-12, KOOS, and HOOS scores were adjusted for age, gender, and BMI by fitting a logistic model and analyzed using the Wald chi-square test (SPSS, Chicago, IL).


Christopher Bell Peter Walker Frederick Kummer Patrick Meere

Balancing in total knee replacement is generally carried out using the feel and experience of the surgeon, using spacer blocks or distractors. However, such a method is not generally applicable to all surgeons and nor does it provide quantitative data of the balancing itself. One approach is the use of instrumented distractors, which have been used to monitor soft tissue releases or indicate a flexion cut for equal lateral and medial forces. More recently an instrumented tibial trial has been introduced which measures and displays the magnitude and location of the loads on the lateral and medial plateaus, during various manoeuvres carried out at surgery. The data set is then used by the surgeon to determine options, whether soft tissue releases or bone cut adjustments, to achieve lateral-medial equality.

The testing method consisted of mounting the femoral component rigidly in a fixture on the vertical arm of an MTS machine. The tibial component was fixed on to a platform which allowed varus-valgus correction, and where the component could be displaced or rotated in a horizontal plane. Two of each size times 4 sizes of production components were tested. Compressive forces from 0–400N in steps of 50N were applied and the readings taken. There were strong correlations between applied and measured forces with mean Pearson's Correlation Coefficient of 0.958.

The special tests under different conditions did not have any effect on the output values. The output data proved to be repeatable under Central Loading with a maximum standard deviation of ± 15.36N at the highest applied force of 400N. “Low battery” did not adversely affect the data. Applying the load steadily to maximum versus load-unload-zero tests produced similar results. Lubrication versus no lubrication tests produced no changes to the results. There was no cross talk of the electronics within the device when loaded on one condyle. For both central and anterior-posterior loading, the contact points were centered medial-lateral on the GUI display, and tracked contact point translation appropriately.

Anterior-posterior loading did create output load variance at the extremes. However, it enabled the validation of the relationship of the femur on the trial surface. In addition, malrotation would be indicated by the femur riding up on the anterior or posterior tibial edges, important for soft tissue tension in all flexion angles.

In conclusion, the sensors provided data which was accurate to well within a practical range for surgical conditions. In our separate experiments on 10 cadaveric leg specimens, even the same test under controlled conditions could produce variations of up to ± 30N. Hence the sensor outputs indicated whether or not the knee was balanced to that level of tolerance, while the contact point data would indicate contacts too close to the anterior or posterior of the tibial surface.


Ilya Bendich Wayne Moschetti Stephen Kantor Kevin Spratt Ivan Tomek

Introduction:

Proponents of quadriceps-sparing (QS) subvastus approach for total knee arthroplasty (TKA) suggest short-term advantages including better early functional results, less pain and shorter hospital stay. However, because of potentially reduced visibility and exposure, the QS approach may compromise component alignment – an important surgeon-controlled outcome affecting implant longevity. The purpose of this study was to determine if a QS approach resulted in compromised component alignment compared to a medial parapatellar arthrotomy (MPPA), when both were performed with contemporary minimally invasive surgery (MIS) principles including small incision (≤ 15 cm), MIS instrumentation, patellar subluxation without eversion, and in situ bone cuts.

Methods:

This prospective, randomized, double-blinded study enrolled 128 patients with knee osteoarthritis undergoing primary TKA using the same cemented, posterior-stabilized prosthesis. After skin incision, patients were randomized to MPPA (n = 66) or QS technique (n = 62), with all surgeries performed by two fellowship-trained arthroplasty surgeons. Using the Knee Society roentgenographic evaluation system, two reviewers blinded to the surgical approach evaluated post-operative radiographs to measure coronal and sagittal plane alignment using the standing femoral and tibial angles as well as the lateral femoral flexion and tibial angles. Inter-observer agreement was ensured by a secondary review of all x-rays where the two observers differed by more than 1 degree in their measurements of a specific radiograph. Differences in mean angles were evaluated using the general linear model and differences in proportions were evaluated using binary regression. All analyses were conducted with SAS 9.3 on the Windows Ultimate 64-bit operating system.


Sanaz Berahmani Dennis Janssen David Wolfson Maarten De Waal Malefijt Nico Verdonschot

Pegs are often used in cementless total knee replacement (TKR) to improve fixation strength. Studies have demonstrated that interference fit, surface properties, bone mineral density (BMD) and viscoelasticity affect the performance of press-fit designs. These parameters also affect the insertion force and the bone damage occurring during insertion. We aimed to quantify the effect of the aforementioned parameters on the short-term fixation strength of cementless pegs.

6 mm holes were drilled in twenty-four human femora. BMD was measured using calibrated CT-scans, and randomly assigned to samples. Pegs were produced to investigate the effect of interference fit (diameters 6.5 and 7.6 mm), surface treatment (smooth and rough- porous-coating [friction coefficient: 1.4]) and bone relaxation (relaxation time 0 and 30 min) and interactions were studied using a DOE method. Two additional rough surfaced peg designs (diameters 6.2 and 7.3 mm) were included to scrutinize interference. Further, a peg based on the LCS Porocoat® (DePuy Synthes Joint Reconstruction, Leeds, UK) was added as a clinical baseline. In total seven designs were used (n = 10 for all groups). Pegs were inserted and extracted using an MTS machine (Figure 1), while recording force and displacement. Bone damage was defined as the difference between the cross-sectional hole area prior to and after the test.

BMD and interference fit were significant factors for insertion force. BMD had a significant positive correlation with pull-out force and subsequent analyses were therefore normalised for BMD.

Pull-out force increased significantly with interference for both surface coatings at time 0 (p < 0.05). However, after 30 minutes the effect remained significant for rough pegs only (p < 0.05-Figure 2A).

Pull-out force reduced significantly with roughness for both peg diameters at time 0 (p < 0.001). However, after 30 minutes the effect remained significant for small pegs only (p < 0.05-Figure 2A).

The time dependant interaction was only significant for smooth pegs in both diameters (p < 0.05-Figure 2A).

Additionally, the pull-out force increased with diameter in a non-linear manner for the rough pegs (Figure 2B). The two surface treatments were not significantly different to the clinical comparator. Interference fit was the only significant factor for bone damage.

BMD was significant for insertion and pull-out forces, reinforcing the need to account for this factor in biomechanical studies and clinical practice. This study also highlights the importance of time in studying bone interactions, with surface treatment and interference showing different interaction effects with relaxation time. Although smooth pegs initially have a higher pull-out force, this effect reduces over time whereas the pullout force for rough pegs is maintained. Smooth pegs also show time sensitivity in relation to interference and the benefit of increased interference reduces over time, whereas it is maintained in rough pegs. This may be explained by different damage (compressive and abrasive) mechanisms associated with different surface treatments.

In conclusion, BMD and interference fit are significant factors for initial fixation. Bone relaxation plays an important role as it reduces the initial differences between groups. Therefore, these findings should be strongly considered in the design development of cementless TKR.


Sanaz Berahmani Dennis Janssen David Wolfson Maarten De Waal Malefijt Nico Verdonschot

To achieve desirable outcomes in cementless total knee replacement (TKR), sufficient primary stability is essential. The primary stability inhibits excessive motions at the bone-implant interface, hence providing the necessary condition for osseointegration [1]. Primary stability for cementless TKR is provided by press-fit forces between the bone and implant. The press-fit forces depend on several factors including interference fit, friction between bone and implant surface, and the bone material properties. It is expected that bone mineral density (BMD) will affect the stability of cementless TKR [2]. However, the effect of BMD on the primary stability of cementless femoral knee component has not been investigated in vitro.

Phantom calibrated CT-scans of 9 distal femora were obtained after the surgical cuts were made by an experienced surgeon. Since the press-fit forces of the femoral component mainly occur in the Anteroposterior (AP) direction, the BMD was measured in the anterior and posterior faces for a depth of 5 mm; this depth was based on stress distributions from a Finite Element Analysis of the same implant design. In addition, four strain gauges were connected to different locations on the implant's outer surface and implant strain measured throughout as an indication of underlying bone strain. A cementless Sigma CR femoral component (DePuy Synthes Joint Reconstruction, Leeds, UK) was then implanted using an MTS machine. In order to simulate a ‘normal’ bone condition, the implanted bone was preconditioned for one hour at a cyclic load of 250–1500 N, and a rate of 1 Hz. Finally, the implants were pushed-off from the bone in a high-flex position. Forces and displacements were recorded both during insertion and push-off tests.

Strong correlations were found for insertion and push-off forces with BMD, R2 = 0.88 and R2 = 0.88, respectively (p < 0.001), so although implantation may be harder in patients with higher BMD, initial stability is also improved. A correlation was also found between final strain and push-off forces (R2 = 0.89, p < 0.01) and BMD also showed a strong reverse correlation with total bone relaxation (R2 = 0.76, p = 0.023). These results indicate that higher BMD induces higher bone strain, which can lead to improved fixation strength.

There is no consensus on the best fixation method for the TKR but some surgeons prefer a cementless design for young and active patients. The results of our study showed that the primary stability of a cementless femoral knee component is directly correlated with the bone mineral density. Therefore, patient selection based on bone quality may increase the likelihood of good osseointegration and adequate long-term fixation for cementless femoral knee components.


Manoshi Bhowmik-Stoker Michael Howard Danielle Anthony Kirby Hitt David Jacofsky Eric Smith

1) INTRODUCTION

Total knee arthroplasty (TKA) is one of the most common orthopaedic procedures performed, and is projected to exponentially increase over the next 20 years. As primary TKA cases increase, so does the frequency of revisions. The primary goals for all TKA cases include alleviating pain and improving overall knee function. The objective of this study was to evaluate the change in outcomes as measured by the Knee Society Score (KSS) between primary and revision TKA systems.

2) METHODS

This data was collected as part of three prospective, post-market, multicenter studies comparing preoperative to 6-week data. Patients were stratified into two groups based on type of single radius knee device; Posteriorly Stabilized (PS) group and Total Stabilizer (TS) group. Early clinical outcomes based on the KSS and operative data were used to compare groups.


Thom Bitter Dennis Janssen B. Willem Schreurs Imran Khan Nico Verdonschot

Introduction

Recent reports have implicated fretting corrosion at the head-stem taper junction as a potential cause of failure of some large diameter metal-on-metal (MOM) devices. While it has been suggested that larger MOM heads, may induce greater frictional torques at the taper connection, the exact mechanisms underlying fretting corrosion remain poorly understood.

It is likely that the onset of the corrosion process is caused by mechanical factors, such as contact stresses and micromotions occurring at the interface. These stresses and micromotions depend on the fixation of the head onto the stem and may be affected by blood, fat, bone debris or other contaminations. The fixation of the head is achieved intraoperatively through impaction.

To further study this phenomenon, we adopted a finite element approach in which we modeled the head-taper junction fixation mechanics. In this model, we analyzed the effect of impaction force on the micromotions occurring at the head-stem interface.

Materials and methods

We created a model of a BIOMET Type-1 taper and an adapter that is typically used for larger heads.

Titanium alloy material properties were assigned to both components, and frictional contact (μ = 0.5) was simulated between the adapter and the taper.

To ensure that the model accurately represented the contact mechanics, we first simulated experiments in which the head was assembled on the taper in a load-controlled manner, at different load (4 and 15 kN), after which it was disassembled axially. The disassembly loads predicted by the FEA simulations were then compared to the experimental values.

After ensuring a correct prediction of the disassembly loads, we used various impaction loads (2, 4, and 15 kN) to assemble the taper, after which a 2.3 kN load (ISO 7206-4) was applied to the adapter/taper assembly. This loading regime is commonly used to determine endurance properties of stemmed femoral components. Under these loading conditions, we then analyzed the contact stresses and micromotions, and the effect of impaction load on these quantities.


Dustin Williams John Vinciguerra Julia Lerdahl Roy Bloebaum

Introduction:

Periprosthetic infections that accompany the use of total joint replacement devices cause unwanted and catastrophic outcomes for patients and clinicians. These infections become particularly problematic in the event that bacterial biofilms form on an implant surface. Previous reports have suggested that the addition of Vitamin E to ultra-high-molecular-weight polyethylene (UHMWPE) may prevent the adhesion of bacteria to its surface and thus reduce the risk of biofilm formation and subsequent infection.1–3 In this study, Vitamin E was blended with two types of UHMWPE material. It was hypothesized that the Vitamin E blended UHMWPE would resist the adhesion and formation of clinically relevant methicillin-resistant Staphylococcus aureus (MRSA) biofilms.

Methods and Materials:

Five sample types were manufactured, machined and sterilized (Table 1). To determine if MRSA biofilms would be reduced or prevented on the surface of the Vitamin E (VE) loaded samples (HXL VE 150 kGy and HXL VE 75 kGy) in comparison to the other three clinically relevant material types, each was tested for biofilm formation using a flow cell system.4

Direct Bacterial Quantification – An n = 7 samples of each material type were placed individually into a chamber of the flow cell. A solution of 10% modified brain heart infusion (BHI) broth containing 105 MRSA cells/mL was flowed through each chamber. Using previously established protocols,4–7 after 48 hours of growth, each sample was removed, and the number of colony forming units (CFU) determined using a 10-fold dilution series.

SEM Imaging – Using the same protocol as above, after the 48-hour incubation period, an n = 7 of each material type were fixed in 2.5% glutaraldehyde, dehydrated in ascending concentrations of ethanol, coated with carbon and imaged using scanning electron microscopy (SEM).


Full Access
Nicolas Hohl Richard A Boiardo Michel Brax Gerard Giordano Sandrine Polakovic

Total knee arthroplasty (TKA) is a common procedure with good success rates. The literature shows resection accuracy plays a crucial role in device longevity1. Computer guidance is used by some surgeons to enhance accuracy.

This study reports on a continuous series of Optetrak knee prostheses (Exactech Inc., FL, USA) implanted by three senior surgeons between July 2010 and April 2013.

259 TKA were implanted at the Haguenau Hospital, Haguenau, France (Site 1), Joseph Ducuing Hospital, Toulouse, France (Site 2) and Saint Michaels Medical Center, Newark, NJ, USA (Site 3) using Exactech GPS (Blue-Ortho, Grenoble, FR), a new computer-assisted guidance system. Surgeons can use the unique Exactech GPS profiler to define steps to be computer-assisted during surgery. Each centre in this study used different surgical profiles. Planned tibial and femoral cuts were compared to actual cuts digitised using GPS. Operating time and external femoral rotation were analyzed and post-operative leg alignment was compared to pre-operative.

The mean error between planned and digitised proximal tibial cuts was 0.26° ± 1.11 of valgus and 0.06° ± 0.99 of posterior slope for Site 1, 0.07° ± 0.89 of varus and 0.53° ± 0.90 of anterior slope for Site 2, and 0.19° ± 0.73 of varus and 0.10° ± 1.17 of posterior slope for Site 3 (see Fig. 1). The mean error between planned and digitised femoral distal cuts was 0.03° ± 0.99 of varus and 0.67° ± 1.36 of extension for Site 1, 0.14° ± 0.85 of varus and 0.49° ± 0.94 of extension for Site 2, and 0.26° ± 0.86 of varus and 0.09° ± 1.22 of flexion for Site 3. Average operating time was 38 minutes for Site 1, 29 minutes for Site 2, and 34 minutes for Site 3. External femoral component rotation ranged from 0° to 18° with an average of 3.7° degrees for Site 1 and from −3° to 8° with an average of 3.0° for Site 2. External rotation was fixed at 3° for Site 3. Post-operative Hip-Knee-Ankle angle (HKA) varied between 177° and 182° with an average of 179° for Site 1, 172° to 184° with an average of 179° for Site 2, and 178° to 185° with an average of 180° for Site 3. Pre-operative HKA ranged from 162 to 191°.

Despite different techniques and teams, all surgeons experienced similar results. Cuts were aligned in the frontal plane, while guidance was harder to follow in the sagittal plane, possibly due to saw blade bending during resection. Average surgical time was similar. GPS guidance added an average of 10 minutes to standard surgical times. All surgeons agreed the increased accuracy justified the additional time. Regardless the site, all average femoral rotations were close to the accepted 3° standard. Average post-operative HKA was 179°. HKA scores were within 3° of perfect alignment in all Site 1 cases and 96% of Site 2 and Site 3 cases. According to the literature1, HKA between 177° and 183° is linked with high implant survival.

Participating surgeons associated Exactech GPS with satisfactory immediate post-operative results.


Gary Bradley

Introduction

Dissemination of Total hip Arthroplasty through the direct anterior approach has, depending upon one's experience and perspective, benefitted from or been plagued by aggressive marketing. Although first developed over 60 years ago it was all but unknown until the past decade. This study exams one community surgeon's experience and thus sheds light on whether the ATHA is a viable operation for all orthopaedic surgeons.

Methods

332 hips having a THA through the direct anterior approach were prospectively studied. Side and sex distribution were approximately equal; primary OA was by far the most common diagnosis. 4 hips were converted from a previous operation for fracture. No hips were excluded; all hips were replaced through the direct anterior approach.

All hips had the same HA coated, cementless triple-taper stem; a variety of cups were used. 92% of the bearings were ceramic on poly including 22% “dual mobility” design; 88% of the heads were 28 or 32 mm. A special orthopaedic table and intraoperative c-arm were used universally. Charnley Merle D'Aubigne, Harris, and WOMAC scores were obtained before surgery and annually thereafter.

Anti-embolic prophylaxis was with intraop bilateral thigh high sequential pumps, early mobilization and aspirin for most. Those patients deemed at risk received lovenox, and those already on Coumadin continued – with bridging lovenox.


Danilo Bruni Francesco Iacono Giovanni Raspugli Ibrahim Akkawi Maurilio Marcacci

Purpose:

Management of unicompartmental knee osteoarthritis (OA) in middle-aged patients is a challenging problem. Recent studies have underlined the efficacy of UKA not just in elderly, but also in middle-aged patients. The primary purpose of the present study was to determine the short to mid-term survivorship of an all-poly tibial UKA in patients under 60 years of age. The secondary purpose was to prospectively evaluate the clinical outcome in this selected group of patients.

METHODS:

Thirty-three consecutive patients under 60 years of age at the time of surgery with isolated medial compartment OA underwent a unilateral medial UKA from 2002 to 2005 and were prospectively followed. A Kaplan-Meyer analysis was performed to determine the 8-years implant survivorship with revision for any reason as endpoint. KSS, WOMAC, Tegner-Lysholm, Tegner and VAS scores were prospectively evaluated at 3 to 6 years follow-up. Weight-bearing radiographs were collected pre-operatively and at 3 to 6 years follow-up to prospectively evaluate femorotibial angle (FTA), tibial plateau angle (TPA) and posterior tibial slope (PTS).


Danilo Bruni Laura Bragonzoni Michele Gagliardi Marco Bontempi Maurilio Marcacci

The Rizzoli Orthopaedic Institute has been involved in RSA since 1998. During last 25 years, several investigations have been carried on to evaluate both implant fixation and poliethylene deformation in unicompartmental and total knee replacements. Nevertheless, RSA has also been used to investigate the relative micromotions and the kinematic modifications in cadaveric models of ankles with ligamentous injuries. RSA evaluation has demonstrated that in a particular TKR implant, with mobile half-bearings, the threshold for loosening was 1.3° for rotation about the longitudinal axis and 0.5 mm for medio-lateral translation. Moreover, RSA has revealed cold flow to be concentrated in the posterior region of the medial half-bearing. This has lead to further improvement in polyethilene and implant design. RSA has also demonstrated that in all-poly tibial UKR, poliwear does not impair tibial component fixation and that deformation of the all-poly tibial component is strictly correlated to implant loosening. Moreover, RSA has been used to investigate stress-inducible displacement of the tibial component in all-poly UKRs. It has been demonstrated that rotations around the transverse axis of the knee joint are the most common form of stress-inducible displacement, while stress-induced translations are negligible. Moreover, stress-inducible translational displacement has reached significantly higher values for those patients with unexplained painful UKR, despite no sign of loosening on conventional radiographic and standard supine RSA evaluations.

Further application of RSA has focused on the kinematic evaluation of poliethilene motion pattern modifications throughout a 3 years follow-up period after a mobile-bearing TKR. Patients have been investigated in weight-bearing conditions and results demonstrated that longitudinal rotations and medio-lateral translations tended to increase at last follow-up, while sagittal translations dod not show any significant modification over time.

At present, a new device has been installed at the Istituto Ortopedico Rizzoli. It was specifically designed and made for RSA, static and fluoroscopic. This device can work both in mono- and bi-planar configuration as required by the RSA protocols. Moreover it is able to acquire image stacks in order to study the in-vivo and real time kinematics of a joint. he theoretical biomechanical resolution of a static RSA followup tests is 0.2 mm for translation and 0.3° for rotation. In fluoroscopic configuration the theoretical resolution is 1 mm for translation and 1° for rotations, depending on the used frame rate and on the joint movement speed. A kinematic comparison of different prosthetic designs is currently ongoing, to evaluate different motion patterns under dynamic weight-bearing conditions and to compare them with passive kinematics acquired intra-operatively using a navigation system.


Danilo Bruni Laura Bragonzoni Marco Bontempi Michele Gagliardi Ibrahim Akkawi Maurilio Marcacci

Introdution:

Over the last years research has focused on attempts to achieve better fixation in knee prosthesis by improving cementing techniques and prosthetic designs; thus prosthetic fixation is critical while loosening at the bone-cement interface is still an important matter for the orthopaedic surgeon.

Material and Method:

In the present study, we evaluated in vivo displacement of both total and unicompartimental knee prosthesis implanted on 73 patients by collecting data from RSA associated to the conventional X-rays and clinical follow-ups; we were able to reach only 18 patients (2 males and 16 females) for the actual follow up because of death or other diseases occurred on the other patients over the years (mean age at the time of surgery 68, range 27–83).


Christopher Stevens JC Clark Mark Murphy Tony Bryant Thomas Wright

Purpose:

The reverse total shoulder arthroplasty (RTSA) was approved for use by the United States FDA in 2004. Since its introduction, its popularity for treating a number of shoulder conditions has grown considerably. However, many patients inquire about the potential to return to playing recreational golf, and at present there are no published data about how the RTSA prosthesis affects the golf swing. The purpose of this study is to evaluate the biomechanics of the golf swing in patients with RTSA, as well as the postoperative changes in handicap, driving distance, and holes played/week.

Methods:

A review of patient records for those that had an RTSA placed between June 2004 and December 2008 was performed. These patients were sent a questionnaire inquiring about details of golfing before and after RTSA. Patients who were still golfing after implantation of the RTSA prosthesis were selected for six-camera motion analysis testing of their golf swing. Computer analysis program was used to calculate parameters to biomechanically describe the golf swing.


Christopher Stevens Tony Bryant Bryan Conrad Aimee Struk Thomas Wright

Introduction:

External rotation (ER) of the shoulder is a commonly used clinical measurement to assess the glenohumeral joint; however, the position in which these measurements are obtained varies between clinicians. The purpose of this study was to compare the following: ER in the upright & supine positions, motion capture & goniometric values of ER, active & passive ER, ER in the right & left shoulders, and ER in male & female subjects.

Methods:

Eighteen subjects (mean age 25.4 yrs) with ‘normal’ shoulders (by screening questionnaire) were enrolled in the study and subject to triplicate measurements of active and passive ER of both shoulders with a goniometer and a 12 camera, high speed optical motion analysis system in both the upright and supine positions. ANOVA was used to compare variables and linear regression used to correlate the goniometer & optical motion capture measurements.


Frederick Buechel

Introduction:

This is a case report of a 78 year old male who underwent outpatient mini-incision medial UKA using the haptic robotic guidance. The patient subsequently suffered a traumatic lateral meniscus tear and underwent a lateral compartment UKA with the same robotic system instead of converting to a total knee replacement at one year post op and is now 2 years post op on the lateral side as well.

Methods:

The patient is a 74 year old male with a BMI of 27, suffering from OA of the right knee. He had a previous TKA on his left side by another surgeon that was followed with a lateral release by still another surgeon with fair to good satisfaction currently; however he did not want another TKA. He had multiple aspirations and injections of corticosteroids for arthritic effusions on his right knee that were moderate to severe and painful. On 7/6/2010 he underwent a right medial UKA using with robotic guidance. The patient had a subsequent injury to his lateral meniscus causing pain for which multiple options were discussed with the patient. The informed patient chose to have a lateral compartment arthroplasty. On 6/21/2011 a lateral compartment UKA was performed on the same patient's right knee through a second mini-lateral incision again using robotic guidance.


Frederick Buechel

Introduction:

Isolated lateral compartment osteoarthritis (OA) occurs in 5–10% of knees with unicompartmental OA. Lateral unicompartmental knee arthroplasty has been limited in its prevalence due to challenging surgical technique issues. A robotic-arm assisted surgical technique has emerged as a way to achieve precise implant positioning which can potentially improve surgical outcomes.

Methods:

63 consecutive lateral unicompartmental knee arthroplasties were performed by a single surgeon with the use of a metal backed, cemented prosthesis installed with the three-dimensional intra-operative kinematics and haptic robotic guidance. The average age of the patient was 72.7 years (range: 59–87) and the average BMI was 27.2 (range: 19.0–38.6). The follow-up ranged from 2 months to 30 months.


Frederick Buechel

Introduction:

Unicompartmental knee arthroplasty has been shown to have lower morbidity, quicker rehabilitation and more normal kinematics compared to conventional TKA, but subchondral defects, or severe osteoarthritic changes, of the medial compartment may complicate component positioning. Successful UKA in these patients requires proper planning and exact placement of the components to ensure adequate and stable fixation and proper postoperative kinematics. This study presents a series of three patients with spontaneous osteonecrosis of the knee receiving a UKA with CT-based haptic robotic guidance.

Methods:

This series includes two females and one male with spontaneous osteonecrosis of the medial femoral condyle who underwent outpatient mini-incision medial UKA using the MAKO Surgical Rio Robotic Arm System. Pre-operatively all patients were found to have pain with weight bearing that would not improve despite non-arthroplasty treatment.


Eddie H. Huang Steven Copp William Bugbee

Introduction:

One of the primary goals in total knee arthroplasty (TKA) is restoration of the mechanical alignment. The accuracy of conventional mechanical alignment guides and computer-assisted navigation systems has been extensively studied. The purpose of this study is to assess the accuracy of a hand-held accelerometer-based navigation system for TKA.

Methods:

Fifty three patients undergoing TKA utilizing the KneeAlign system (OrthAlign Inc, Aliso Viejo, CA) (Figure 1) were performed by two surgeons. Intraoperative data including tourniquet time, device assembly time, and resection times were recorded. Target alignment goals were 0° femoral, tibial, and overall mechanical coronal alignment and 3° femoral flexion and posterior tibial slope. Coronal/sagittal alignment of the implant and the mechanical axis were measured by two independent observers on full length (54 inch) postoperative hip to ankle radiographs.


William Bugbee Pamela A. Pulido Timothy Goldberg Darryl DLima

Introduction:

Rehabilitation after total knee arthroplasty (TKA) is an essential component of treatment. Various protocols and methodologies have evolved to enhance the effect of rehabilitation in the postoperative period. We prospectively evaluated the effect of using an antigravity treadmill as an alternative to routine postoperative physical therapy.

Methods:

Twenty-nine patients undergoing unilateral primary TKA were randomized to either gait training (standard outpatient physical therapy) or to the use of an AlterG® antigravity device for gait training for 2 days/week for 4 weeks for a total of 8 therapy sessions. Average age was 68 and 55% were female. The Knee Injury and Osteoarthritis Outcome Score (KOOS) and Timed Up and Go (TUG) test were collected at baseline (first therapy session), at final therapy session and at 3 months postoperatively. The numerical rating scale (NRS) for pain was measured at baseline and at end of therapy. Adverse events and complications were recorded.


William Bugbee Luke Aram Alex Schenher Michael Swank

Introduction

Optimal alignment and position of implants is an important goal In TKA. Conventional mechanical instruments use the anatomic axis and “average” anatomy to position the femoral component to achieve acceptable mechanical limb alignment. Numerous studies have documented the frequency of TKA outliers (+/− 3 degrees) to be 30% or more. The purpose of this study was to determine the “true” distal femoral valgus angle of the femur.

Methods

13,586 CT scans of patients undergoing TKA with patient specific instruments were analyzed. Three-dimensional reconstructions were performed and the distal femoral anatomic and mechanical axes were measured digitally. The distal femoral valgus angle was defined and the difference between the anatomic and mechanical axes of the distal femur.


Michelle Burgett Ian Clarke Thomas Donaldson Thomas Halim

The relevance of fluid-film lubrication, elasto-hydrodynamic lubrication and ‘tribolayers’ for hip bearings has been the subject of much debate (Fisher 2012). However, knowledge of the thickness and distribution of proteins in and around the wear zone of metal-on-polyethylene (MPE) bearings is scant. The efficacy of protein lubrication with metal-on-metal bearings (MOM) is in discovery. This simulator study was designed to analyze film formation on MOM bearings using varied protein concentrations. The hypotheses were that increasing protein concentrations in the serum lubricant would result in 1) greater thickness of protein films, and 2) reduced MOM wear.

The hip simulator was run for 5 million cycles (5 Mc) duration using 28 mm MOM bearings (DJO Inc) run with the cups anatomical. Lubricant protein concentrations were 16.5, 33, and 66 mg/ml. At each test interval of 1 Mc, the proteins films on CoCr surfaces were analyzed by both interferometry and SEM imaging in main-wear, transition-wear and non-wear zones. Thickness of protein films was measured using non-contacting interferometry. Areas of wear zones were mapped and measured and the areas compared. MOM wear rates were assessed gravimetrically.

It was found that the proteins formed two types of film (Figure 1). Type-1 was visually hazy in appearance, grainy in structure, and most commonly found in the main-wear zone. This type of protein film was always present in the main-wear zone but its thickness (approximately 0.05 μm) did not increase with increase in the lubricant protein concentrations. Type-2 was visually rainbow-like in appearance, more gel-like with thick clumps appearing as islands on the CoCr surfaces, and more common in the transition zone. This type of film was always present (approximately 1 μm thick) and its thickness notably increased in cups with increased lubricant protein concentrations. This film remained relatively consistent on femoral heads and did not change with increased protein concentrations (Figure 2).

The type-1 protein films were always detectable in the actual wear zones but only the type-2 film showed a build-up with protein concentration and only inside the cups. This may be partially a response to the orbital simulator set up. In the Anatomical test mode, the cup is fixed with respect to the load axis and the head oscillates. Thus the main-wear zone on the head had a distributed type of wear patch and the main-wear zone in the cup was fixed. This configuration would allow the type-2 proteins to accumulate around the edge of the cup wear zone. In contrast, they would be scraped off the wear zone of the orbiting femoral head. This study showed that protein films endure even inside the main-wear zone of MOM bearings. In addition, collaborative studies have shown that the protein films are highly mobile and stream across the main-wear zones. Thus there is both an interaction with the CoCr surfaces and a degradation phenomenon that likely results in the protein-rich layers in the transition regions.

Figure 1: SEM images of type 1 and type 2 protein films.

Figure 2: Protein films on MOM bearings under three different protein concentrations.


Michelle Burgett Thomas Halim John Vinciguerra Thomas Donaldson

Is is believed that 3rd-body wear of polyethylene, be it from particles of bone, bone-cement (PMMA), or metal, is an unavoidable risk in total hip arthroplasty (THA). Simulator studies have demonstrated that wear in conventional polyethylene (CXPE) and highly crosslinked polyethylene (HXPE) cups increased 6 and 20-fold respectively when challenged by circulating 3rd-body PMMA particulates. There was no corresponding change in head roughness, i.e. the PMMA did not roughen CoCr surfaces. Many contemporary cup designs now use the vitamin-E process combined with higher crosslinking dosage (VEPE). However, little if anything is known about the VEPE debris. Therefore in this study we analyzed the morphology of VEPE particles from cups that had been run in, a) standard simulator test mode and b) adverse PMMA debris-challenge mode. The aim of this study was to determine how a clinically relevant challenge, such as addition of PMMA particles affected the wear debris. This had not been attempted previously due to contamination polyethylene by PMMA debris. The hypotheses were that, a) during the ‘clean’ test, VEPE would yield smaller debris of standard globular shape compared to controls (XPE) and b) in adverse PMMA challenge mode, VEPE debris size would increase and become more flake-like.

The XPE and vitamin-E blended cups (VEPE) cups were gamma-irradiated at 7.5 Mrad and 15 Mrad, respectively. Cups were run Inverted and mated with ceramic femoral heads of diameter 44 mm (Biolox-delta, Ceramtec). The three test phases included; ‘clean’ for 6 million cycles (6 Mc), abrasive slurry 6–8 Mc (concentration 10g/L), and ‘clean’ 8–10 Mc. The debris was isolated using standard procedure for ‘clean’ tests and a modified procedure for the abrasive slurries. Particles were imaged using SEM and the micrographs analyzed (Image J). Approximately 600 particles were analyzed from each sample (4.5 Mc and 8 Mc) and morphology defined via aspect ratio (AR), equivalent circular diameter (ECD), and circular shape factor (CSF).

The clean test revealed slight differences in shape factors for XPE and VEPE (AR, CSF within 30%: p <0.0001) but none with regard to size (p > 0.9999). The median ECD for both XPE and VEPE was approximately 0.55 μm. The abrasive test revealed a statistical difference (p < 0.0001) in shape compared to the clean test, but varied less than 25%. The greater change in debris morphology between the abrasive test and clean test was size, which increased 3.6 fold for VEPE particles (ECD = 2.0 μm) and 4.3 fold for XPE particles (ECD = 2.3 μm).

It was determined that addition of vitamin E to the PE did not change the size, but did change the shape of PE debris particles up to 30%. This study was the first to isolate debris particles during an abrasive slurry test and determine morphology under such conditions. Debris particles formed in abrasive conditions were found to be 4-fold larger in diameter, suggesting a larger volume of shreds in comparison to the mostly submicron population observed under standard testing conditions.

Figure 1: Boxplot of equivalent circular diameter values.

Figure 2: Boxplot of aspect ratio values.

Figure 3: Boxplot of circular shape factor values.


Emilio Mazza Giorgio Maria Calori Massimiliano Colombo

Introduction:

The development of new prostheses due to large resections has offered important opportunities to orthopedic surgeons mainly in oncology. A medline research can easily underline how poor is the international experience about this cases in nonunion: 75 results for megaprosthesis just 7 works in nonunion.

It is proposed the experience of our department, which deals specifically with the treatment of nonunion, in cases of repeated failures to treatment.

One of the most significant problems in the treatment of relapsing nonunion is the consequent worsening of joint function.

Critical bone defects, sepsis, joint fractures and unclear relapsing nonunions are the most common cases for a megaprosthesis treatment.

In these cases, even if it obtains the healing of nonunion the functional result would be presumptively poor. This radiological or clinical situation drove us, in such cases, to drastic solutions following the principles of cancer cases.

We implanted megaprosthesis with either techniques: 1 stage or 2 stages depending on the clinical findings. In nonunion the main decision making was the septic or aseptic status.

Materials and Methods:

we treated 32 patients with megaprosthesis replacing the nearest joint to the nonunion segment or both the proximal e distal one as follows: proximal femur, distal femur, proximal tibia, and total femur.

The mean follow-up of patients is 12 months (2 yrs max, min 3 months). Clinical and serial radiographic evaluations with standard methods (RX in 45 days, 3-6-12-24 months) was performed; as well as monitoring of blood parameters for 2 months.


Lowry Barnes Dylan Carpenter

Introduction:

Tibial component fit, specifically significant overhang of tibial plateau or underhang of cortical bone, can lead to pain, loosening and subsidence. The purpose was to utilize morphometric data to compare size, match, and fit between patient specific and incrementally sized standard unicompartmental knee arthroplasty (UKA) implants.

Methods:

CT images of 20 medial UKA knees and 10 lateral UKA knees were retrospectively reviewed. Standard and patient-specific implants were modeled in CAD, utilizing sizing templates and patient-specific CAD Designs. Virtual surgery maximized coverage of tibial plateau while minimizing implant overhang. Tibial plateau implant coverage was evaluated for fit and incidence of overhang/undercoverage.


Jacob Cartner Patrick Aldinger Megan Fessenden Chenxi Li

INTRODUCTION:

The use of tapered junctions in primary hip arthroplasty has excellent results. Large heads are being used to mitigate dislocation and optimize range of motion. The prevalence of larger heads, coupled with recent findings regarding corrosion artifacts at tapered surfaces, has spurred growing interest when considering revision rates. The purpose of this study was to determine if correlations exist between severity of corrosion artifacts and head size, head offset, time in vivo, orhead material in a 15 year retrieval database.

METHODS:

Retrieved hip arthroplasty devices with CoCrMo or oxidized zirconium (OxZr) heads were investigated for corrosion artifacts in this study. Female tapered surfaces were scored independently by a panel according to the Goldberg system for assessment of corrosion. Exclusion criteria included less than 1 week in vivo, ceramic taper, and modular proximal stem sleeves. Evaluation was performed on only stem/head taper junctions. SEM analyses and a newly developed method of vertical straightness deviation (VSD) were used on a subset of devices as an additional measure to quantify corrosion within the taper contact region by measuring depth of material loss.


Jesal Parekh Hugh Jones Newton Chan Philip Noble

Introduction:

Angular mismatch of the modular junction between the head and the trunion has been recognized as a contributing factor to fretting and corrosion of hip prostheses. Excessive angular-mismatch can lead to relative motion at the taper interface, and tribo-corrosion of the head-neck junction secondary to disruption of the passive oxide layer. Although manufacturing standards have been adopted to define acceptable tolerances for taper angles of mating components, recent investigations of failed components have suggested that stricter tolerances or changes in taper design may be necessary to avoid clinical failures secondary to excessive taper wear and corrosion. In this study we examine the effect of angular-mismatch on relative motion between the taper and bore subjected to normal gait load using finite element methods.

Methods:

Computer simulations were executed using a verified finite element model (FEM), the results from which were determined to be consistent with literature. A stable, converging hexahedral mesh was defined for the trunnion (33648 elements) and a tetrahedral mesh for the femoral head (51182 elements). A friction-based sliding contact was defined at the taper-bore interface. A gait load of 1638N (2.34 × BW, BW = 700N) was applied at an angle of 30° to the trunnion axis (Figure 1) on an assembled FEM. A linear static solution was set up using Siemens NX-Nastran solver. Angular-mismatch was simulated by incrementing the conical half-angle of the bore to examine these cases: 0°, 0.005°, 0.010°, 0.015°, 0.030°, 0.050°, 0.075°, 0.100°, 0.200°and 0.300°.


Philip Noble Newton Chan Ashley Matthies Alister Hart John A. Skinner

Introduction

Recent retrieval studies and registry reports have demonstrated an alarming incidence of early failure of metal-on-metal THR. This appears to be due to fretting and corrosion at the taper junction (trunnion) between the neck and large diameter heads in metal-on-metal hip implants. It has been proposed that designs with lower bearing clearances and greater cup flexibility deform during implantation leading to increased frictional torque and micromotion at the head-neck taper junction. Small movements at the trunnion may suggest elastic deformation, but large movements may suggest slippage at the friction interface. This study was conducted using retrieved metal-on-metal components to test the hypotheses that: 1. Cup deformation through localized compression leads to increased bearing torque, and 2. Increased torques generated in large head metal-on-metal bearings cause motion of the head-neck taper junction.

Materials and Methods

Nine metal-on-metal hip implants were received from a national joint retrieval service and tested in a mechanical testing machine. The components were of three different designs (ASR, BHR, and Durom) and ranged in diameter from 42–54 mm. A custom jig was constructed to generate controlled radial compression at opposite points on the rim of an acetabular component. The jig was positioned inverted to the normal anatomical position and was angled to simulate the anatomical orientation of the cup (35° inclination, 10° anteversion). With the exception of an initial compression load of 100N, the cups were compressed at 200N intervals to a maximum of 2000N. Three trials at each cup compression load were performed. The torque developed about the trunnion axis was measured as the head articulated through a motion arc of 60° and the friction factor was calculated. Head–neck micromotion was continuously monitored using a non-displacement inductive transducer. Changes in micromotion from the 100N compression load were calculated.


Rabah Qadir Sanbir Sidhu J. Lockwood Ochsner Mark S. Meyer George Chimento

Introduction:

Deep infection after total joint arthroplasty is a devastating complication with reported incidence of 1–3% with projection to increase to 6.8% by 2030. The direct costs of revision surgery due to septic failure are estimated at over $55,000 per case. Antibiotic-Loaded Bone Cement (ALBC) has been proposed as a preventive measure to decrease post-operative infection rates. Its efficacy has been compared with plain bone cement (PBC) in multiple studies. There has been no study to our knowledge examining its efficacy in “high risk” patients. The purpose of this study is to compare infection rates in three cohorts of patients: (1) all patients receiving only PBC, (2) all patients receiving only ALBC, and (3) only “high risk” patients receiving ALBC.

Methods:

A standard cement protocol was instituted at our hospital for primary total knee arthroplasties (pTKA). From January 2000 to 2005 all pTKAs were performed with PBC. From February 2005 to May 2010, all pTKAs were performed with ALBC. From June 2010 to March 2012, all patients received regular bone cement unless they had previous diagnoses of rheumatoid arthritis, obesity, and/or diabetes mellitus. Our institutional joint registry was queried and the three cohorts' individual charts were retrospectively reviewed. Infection rates amongst cohorts were compared at 30 days, 6 months, and 1 year from index surgery date utilizing two sided proportion tests.


Kwang Woo Nam Sung-Wook Choi Uk Nam Kyu-Bum Seo Sang-Rim Kim Hee Joong Kim

Introduction:

Whole blood metal ion level and clinical outcomes of ceramic-on-metal bearing were comparable to ceramic-on-ceramic THA in this prospective randomized controlled trial.

Methods:

We randomized 150 consecutive THA cases at one institution into two groups: Group I and Group II. Group I, 75 cases, received a THA using ceramic-on-metal couplings and Group II, 75 cases, received ceramic-on-ceramic bearing THA. The implant differed only in the bearing surfaces used. We compared the serum levels of cobalt (Co) and chromium (Cr) and functional outcome scores preoperatively, and at 2, 6, and 12 months postoperatively.


Ian Clarke Jean Yves Lazennec Adrien Brusson Michelle Burgett Thomas Donaldson

This study of retrieved 28 mm Metasul™ (cemented) revealed for the first time adverse wear effects created by impingement-subluxation in MOM. The 10 cases selected (with femoral stems) had annual follow-up 3–11 years. (1) Unequivocal evidence here shows that all heads routinely subluxed from the Metasul liners.

Femoral stems revealed well-demarcated notches (DN) on necks and trunnions (Fig. 1a: n = 6), shallow cosmetic blemishes (Fig. 1b CB: n = 4), and abrasion by cement (Fig. 1b: PMMA). As demonstrated by EOS radiographs, impingement locations varied with implant positioning, pelvic mobility and patient functionality – both anterior and posterior notching (Fig. 1). The first impingement notch occurred with head located (Fig. 2a), whereas the head had subluxed from the cup at 2nd notch (Fig. 2b). The model demonstrated that patients gained 20° motion by such head-subluxation manoeuvres. It was surprising that there was no collateral damage evident on the liners. Even with severe notching of Ti6Al4V and CoCr stems, the cup rims generally appeared well-polished.

Femoral heads revealed macro-stripe damage on articular surfaces (Fig. 3), as did cups. Basal and polar macro-stripes on heads were always located at hip impingement positions. The equatorial stripes were formed at main-wear zone boundaries. Thus equatorial stripes were likely created by some form of rim-impact damage (micro-separation) or by local ingress of 3rd-body wear particles under the cup rim.

Micro-grooving was evident within these macro-size stripes and frequently featured large raised lips (Fig. 3), interpreted as signs of adverse 3rd-body wear mechanisms, and rarely described.(2) It would appear that large metal particulates were released during MOM impingement-subluxation manoeuvres and circulated the hip joint to producing severe 3rd-body abrasion. Gradual decomposition of such large debris to nano-sized particulates under joint loading would then produce the often-referenced ‘self polishing’ effect of CoCr. EDS studies revealed metal smears on the CoCr surfaces containing the elements of titanium alloy (Ti, Al, V). This was further evidence of impingement-subluxation manoeuvres.(1, 3)

In-vivo cup wear patterns also appeared much larger than those produced in MOM simulators. Such differences likely reflected head-subluxation in vivo, whereby heads unconstrained by the subluxation maneuver were free to orbit up and even cross cup rims, i.e. “edge wear”. This appears to be the first study detailing the adverse wear mechanisms in MOM bearings. There are two limitations to our retrieval study, a) these wear results may not be representative for all MOM designs, and b) it is unknown whether such results have relevance to MOM cases continuing successfully.


Chadd Clary Alex Schenher Luke Aram Filip Leszko Mark Heldreth

Introduction:

Appropriate transverse rotation of the tibial component is critical to achieving a balance of tibial coverage and proper tibio-femoral kinematics in total knee replacement (TKR), yet no consensus exists on the best anatomic references to determine rotation. Historically, surgeons have aligned the tibial component to the medial third of the tibial tubercle1, but recent literature suggests this may externally rotate the tibial component relative to the femoral epicondylar axis (ECA) and that the medial border of the tubercle is more reliable2. Meanwhile, some TKR components are designed with asymmetry of the tibial tray assuming that maximizing component coverage of the resected tibia will result in proper alignment. The purpose of this study was to determine how different rotational landmarks and natural variation in osteoarthritic patient anatomy may affect asymmetry of the resected tibial plateau.

Methods:

Pre-operative computed-tomography scans were collected from 14,791 TKR patients. The tibia and femur were segmented and anatomic landmarks identified: tibial mechanical axis, medial third and medial border of the tibial tubercle, PCL attachment site, and the surgical ECA of the femur. Virtual surgery was performed with an 8-mm resection (referencing the high side) made perpendicular to the tibial mechanical axis in the frontal plane, with 3° posterior slope, and transversely aligned with three different landmarks: the ECA, the medial border, and medial third of the tubercle. In each of these rotational alignments, the relative asymmetry of the medial and lateral plateaus was calculated (Medial AP/Lateral AP) (Fig. 1).


Robert Cohen

Cementless biologic fixation surfaces on total joint replacement devices, such as those used in total hip and knee procedures, have evolved over the decades. Historically, various surfaces to allow bone ingrowth or ongrowth have been applied as a coating to a pre-formed solid metal substrate. As shown in Figure 1, from left to right, representative coating surfaces include sintered beads, diffusion-bonded fiber metal, and plasma sprayed titanium. In certain applications, tantalum porous metal (Fig 1, left) can be used without a solid metal substrate, but its most widespread usage is in a modular acetabular cup design with the porous metal diffusion-bonded to a solid metal substrate similar to other coatings. Each of these examples of biologic fixation surfaces has limitations. With comparatively low porosity, bead, fiber metal and plasma spray coatings are simply a surface enhancement onto a rigid machined, forged or cast metal substrate. Furthermore, the thermal process to apply the coatings can adversely affect the mechanical properties of the metal substrate. Released in the 1990's, tantalum porous metal is considered a ‘highly porous metal’ with twice the porosity of the applied surface coatings. With that greater porosity comes lower strength that requires engineers to make standalone tantalum porous metal shapes more bulky. The chemical deposition process to produce tantalum porous metal shapes has also limitations on geometry possibilities. Where bonding the tantalum porous metal to a solid metal substrate is necessary for adequate strength, that diffusion bonding process pressure can diminish the surface coefficient of friction necessary for initial stability.

A new class of manufacturing processing, referred to as ‘additive manufacturing’, allows engineers to create unique porous configurations. These configurations can be fabricated with beneficial properties to a specific implant application. One such enabling additive manufacturing process is called direct metal laser sintering (DMLS). This process utilizes a laser that travels over a fine powder bed. The laser path is determined by a program that mimics a computer model. Where the laser contacts the powder bed, the powder consolidates. Layer by layer, a scaffold porous metal is fabricated. Figure 2 shows a titanium alloy porous metal structure produced by DMLS. This formed biomaterial has 65% porosity, a high coefficient of friction, low stiffness, and strength that is 2 to 3 times that of tantalum porous metal. From a design versatility perspective, with greater strength, relatively thinner and more bone conserving geometries can be developed. When a solid metal surface interface to secure a modular polymer bearing is required, the DMLS process can produce the solid surface and the porous metal at the same time. With no secondary bonding thermal cycle needed, the construct's mechanical integrity is not compromised. Advancing biologic fixation necessitates bone conserving implant designs that have the properties to achieve immediate mechanical stability and longer term bone ingrowth. This novel use of DMLS in this particular porous metal geometry allows engineers to meet those criteria.


Robb Colbrunn Tara Bonner Wael Barsoum Jason Halloran

Introduction

Experimental testing reproducing activity specific joint-level loading has the potential to quantify structure-function relationships, evaluate intervention possibilities, perform device analysis, and quantify joint kinematics. Many recent technological advancements have been made in this field and inspire this study's aim to present a framework for the application of activity dependent tibiofemoral loading in a specific custom developed 6 degree of freedom (DOF) robotic test frame. This study demonstrates a pipeline wherein kinetic and kinematic data from subjects were collected in a gait lab, analyzed through musculoskeletal modeling techniques, and applied to cadaveric specimens in the robotic testing system in a real-time manner. This pipeline (Figure 1 blue dotted region) fits into a framework for synergistic development and refinement of arthroplasty techniques and devices.

Methods

Gait lab kinetic and kinematic data for walking was collected from 5 subjects. Subject-specific musculoskeletal modeling was performed to determine 6 DOF active component joint loading (OpenSim version 2.4, simtk.org). Kinetic profiles of the stance phase of gait were estimated and experimentally prescribed in a clinically relevant joint coordinate frame (as a function of time). Of note, knee flexion angle was the only kinematically applied DOF in the robotic testing system. Six fresh-frozen left cadaveric knee specimens (3 male, 3 female, age 49–70) were acquired. The specimens were rigidly secured to the robotic Universal Musculoskeletal Simulator (UMS) custom testing apparatus [1], which controlled joint loads with a real-time force feedback controller. Joint loads were scaled to 40% of predicted loads determined through modeling, because of system load capacity limitations and to prevent joint soft tissue damage potentially caused by additional loads without active muscle constraints. The loading profile for the walking activity was applied to each of the knees and the resulting kinematics were recorded. In addition, the force feedback controller performance was evaluated by calculating the root-mean-square (RMS) error between the desired and actual loads throughout these dynamic loading profiles.


Conor Lowry Graham Vincent Alison Traynor David Simpson Simon Collins

Introduction:

Leg length and offset discrepancy resulting from Total Hip Replacement (THR) is a major cause of concern for the orthopaedic community. The inability to substitute the proximal portion of the native femur with a device that suitably mimics the pre-operative offset and head height can lead to loss of abductor power, instability, lower back pain and the need for orthodoses (1). Contemporary devices are manufactured based on predicate studies (2–4) to cater for the variations within the patient demographic. Stem variants, modular necks and heads are often provided to meet this requirement. The number of components and instruments that manufacturers are prepared to supply however is limited by cost and an unwillingness to introduce unnecessary complexity. This can restrict their ability to achieve the pre-osteoarthritic head centre for all patient morphologies. Corin has developed bone conserving prosthesis (MiniHip™) to better replicate the physiological load distribution in the femur. This study assesses whether the MiniHip™ prosthesis can better match the pre-osteoarthritic head centre for patient demographics when compared to contemporary long stem devices.

Method:

The Dorr classification is a well accepted clinical method for defining femoral endosteal morphology (5). This is often used by the surgeon to select the appropriate type and size of stem for the individual patient. It is accepted that a strong correlation exists between Flare Index (FI), characterising the thinning of cortical walls and development of ‘stove-pipe’ morphology, and age, in particular for females (Table 1) (3). A statistical model of the proximal femur was built from 30 full length femoral scans (Imorphics, UK). Minimum and maximum intramedullary measurements calculated from the statistical model were applied to relationships produced by combining Corins work with that of prior authors (Table 2) (2; 3; 6). This data was then used to generate 2D CAD models into which implants were inserted to compare the head centres achievable with a MiniHip™ device compared to those of a contemporary long stem.


Alison Traynor Amy Kinbrum Jonathan Housden Simon Collins

Introduction

Bearing surfaces of metal-on-metal (MoM) hip resurfacing devices and total hip replacements (THRs) are a known source of metallic debris. Further, large diameter heads and the high friction of a MoM joint are thought to lead to fretting and corrosion at the taper interface between modular components1. The metal debris generated can cause significant problems on the joint area2. This paper investigated fretting and corrosion of femoral head-neck junctions. Variables of the head-neck junction which may have an effect on fretting and corrosion were identified with the aim of determining the key drivers so that their risk on fretting and corrosion could be reduced through design. Additionally, a Chromium Nitride (CrN) coating was assessed to determine the effect on fretting and corrosion of coating the stem (male), head (female) or both trunnion interfaces. As there is currently no standard specification for a head-neck trunnion interface and trunnion designs vary significantly across the market, this work may lead to a positive change in the design and materials used in head-neck taper interfaces for all THR devices.

Methods

Suitable head and stem combinations were identified to enable individual variables such as; coating, medial-lateral (M-L) offset, head offset and taper angle to be isolated (Figure 1 and Figure 2). For the coated components a 3 μm CrN coating was applied to trunnion using electron beam physical vapour deposition (Tecvac, Cambridge, UK). Fretting and corrosion testing was carried out in accordance with ASTM F1875-98 (2009) method II procedure B3 following assembly of the components under a 2 kN load.


Alfonso Manzotti Norberto Confalonieri

INTRODUCTION:

Despite clear clinical advantages Unicompartimetal Knee Replacement still remain an high demanding and less forgiving surgical procedure. Different Authors in literature pointed out how malalignment increases the rate of aseptic failure even more than in TKR. Computer-assisted surgery has been proposed to improve implant positioning in joint replacement surgery with no need of intramedullary guide despite no still proven clinical advantages. Likewise more recently Patient Specific Instrumentation (PSI) has been suggested, even in partial knee reconstruction, as a new technology capable of new advantages such as shorter surgical times and lower blood losses maintaining at least the same accuracy. Aim of the study is to present a prospective study comparing 2 groups of UKR s using either a computer assisted technique or a CT-based Patient Specific Instrumentation.

MATERIALS AND METHODS:

Since January 2010, 54 patients undergoing UKR because medial compartment arthritis were enrolled in the study prospectively. Before surgery patients were alternatively assigned to either computer-assisted alignment (group A) or patient specific instrumentation group (group B). In the group A (27 knees) the implant (Sigma, Depuy Orthopaedics Inc, Warsaw, Indiana, USA) was positioned using a CT-free computer assisted alignment system specifically created for UKR surgery (OrthoKey, Delaware, USA). In group B (27 knees) the implant (GMK Uni, Medacta, Castel San Pietro, Switzerland) was performed using a CT-based PSI technology (MyKnee, Medacta, Castel San Pietro, Switzerland). In both the groups all the implants were cemented and using always a fixed metal backed tibial component. The surgical time and complications were documented in all cases. Six months post-operatively the patients underwent to the same radiological investigation to determine the frontal femoral component angle (FFC), the frontal tibial component angle (FTC), the hip-knee-ankle angle (HKA) and the sagittal orientation (slope) of tibial/femoral components. The number and percentage of outliners for each parameter was determined. In addition the percentage of patients in each group with all 5 parameters within the desired range was calculated. Furthermore the 2 groups were clinically assessed using KSS and Functional score


Emmalynn Connor Florian Boucher Thies Wuestemann Ross Crawford

Introduction

The Exeter cemented polished tapered stem design was introduced into clinical practice in the early 1970's. [i] Design and cement visco-elastic properties define clinical results [ii]; a recent study by Carrington et al. reported the Exeter stem has 100% survivorship at 7 years. [iii] Exeter stems with offsets 37.5–56 mm have length 150 mm (shoulder to tip). Shorter stems, lengths 95–125 mm, exist in offsets 30–35.5 mm. The Australian National Joint Replacement Registry recently published that at 7 years the shorter stems are performing as well as longer stems on the registry [iv]. Clinical observation indicates in some cases of shorter, narrower femora that fully seating a 150 mm stem's rasp in the canal can be difficult, which may affect procedural efficiency. This study investigates the comparative risk of rasp distal contact for the Exeter 150 mm stem or a 125 mm stem.

Materials and Methods

Rasps for 37.5, 44, 50 mm offset, No.1, 150 mm length stems (Exeter, Stryker Orthopaedics, Mahwah NJ) were compared with shortened length models using SOMA™ (Stryker Orthopaedics Modeling and Analytics technology). 637 patients' CT scanned femora were filtered for appropriate offset and size by measuring femoral-head to femoral-axis distance and midsection cancellous bone width (AP view). These femora were analyzed for distal contact (rasp to cortices) for 150 mm and 125 mm models (Figure 1). The widths of the rasp's distal tip and the cancellous bone boundary were compared to assess contact for each femur in the AP and ML views; the rasp was aligned along an ideal axis and flexed in order to pass through the femoral neck (ML view only).


John Cooper Sheila Sanders Richard Berger

Introduction

Air travel and total joint arthroplasty are both established risk factors for development of venous thromboembolism (VTE); accordingly patients are typically counseled against flying in the early postoperative period. The basis for this recommendation may be unfounded, as the risk of VTE associated with flying in the early postoperative period has not been investigated.

Methods

This is a case-control study of 1465 consecutive unilateral total hip arthroplasties (THA) and total knee arthroplasties (TKA) performed by a single surgeon over an 18-month period. A multimodal regimen was used for VTE prophylaxis, consisting of early mobilization, mechanical prophylaxis, and chemoprophylaxis according to a risk-stratification model; 96% of patients received aspirin as the sole chemoprophylactic agent. The study population consisted of 220 patients (15.0%) who flew at a mean of 2.9 days after surgery. Patients who elected to fly were encouraged to wear anti-embolic stockings, perform frequent ankle-pump exercises, and move around at least every hour. Mean flight duration was 2.7 hours (range, 1.1 to 13.7 hours). This study population was compared to a control population of 1245 patients (85.0%) who did not fly during this time. Baseline characteristics were similar between the groups, with the exception that the group who flew tended to be older (65.5 vs. 59.5 years, p < 0.001) with a lower body-mass index (28.4 vs. 31.1 kg/m2, p < 0.001).


John Cooper Robert Urban Carl Deirmengian Wayne Paprosky Joshua J Jacobs

Introduction

Taper corrosion at modular junctions can cause a spectrum of adverse local tissue reactions (ALTR) in the periprosthetic soft tissues in patients who have undergone total hip arthroplasty (THA). Because these reactions are usually painful, taper corrosion has become part of the differential diagnosis of hip pain following THA. However these destructive lesions may not always cause pain, and can occasionally result in other atypical presentations. The purpose of this study is to describe a cohort of patients presenting with late and recurrent instability following THA due to underlying ALTR and taper corrosion.

Methods

This is a multicenter retrospective case series of fourteen patients presenting with late instability secondary to ALTR and corrosion at the modular head-neck taper. The cohort included nine women and five men with a mean age of 66.8 years (range, 49 to 74). All patients had a metal (CoCr)-on-polyethylene bearing surface, but had a range of CoCr and Ti-alloy stem designs from three different manufacturers. Seven patients had 28 mm heads, while the rest had 32–40 mm heads. Patients experienced a mean of 3.4 dislocations (range, 2 to 6) at an average of 5.2 years (range, 0.4 to 17.0) following their index surgery. Although most reported some degree of discomfort around the hip, instability was the primary presenting symptom in all fourteen patients, and four were otherwise completely asymptomatic. Serum metal levels demonstrated a greater elevation of cobalt (mean 3.13 ng/mL) than chromium (mean 2.33 ng/mL). Preoperative infection workup including serum inflammatory markers and a hip aspiration documented the absence of sepsis.


Oren Costantini Daniel Choi Lawrence Gulotta Andreas Kontaxis

Lateralizing the center of rotation in reverse shoulder arthroplasty has been the subject of renewed interest due to complications associated with medialized center of rotation implants. Benefits of lateralization include: increased joint stability, decreased incidence of scapular notching, increased range of motion, and cosmetic appeal. However, lateralization may be associated with increased risk of glenoid loosening, which may result from the increased shear forces and the bending stresses that manifest at the bone-implant interface. To address glenoid loosening in reverse implants with lateralized joint centers, recent studies have focused on testing and improving implant fixation. However, these studies use loads derived from literature specific to subjects with normal anatomy. The aim of this study is to characterize how joint center lateralization affects the loading in reverse shoulder arthroplasty.

Using an established computational shoulder model that describes the geometry of a commercial reverse prosthesis (DELTA® III, DePuy), motion in abduction, scapular plane elevation, and forward flexion was simulated. The simulations were run for five progressively lateralized centers of rotation: −5, 0, +5, +10, and +15 mm (Figure 1). The model was modified to simulate a full thickness rotator cuff tear, where all cuff musculature except Teres Minor were excluded, to reflect the clinical indication for reverse shoulder arthroplasty on cuff tear arthropathy patients. To analyze the joint contact forces, the resultant glenohumeral force was decomposed into compression, anterior-posterior shear, and superior-inferior shear on the glenoid.

Joint center lateralization was found to affect the glenohumeral joint contact forces and glenoid loads increased by up to 18% when the center was lateralized from −5 mm to +15 mm. Compressive forces were found to be more sensitive to lateralization in abduction, while changes in shear forces were more affected in forward flexion and scapular plane abduction. On average, the superior shear component showed the largest increases due to lateralization (up to a 21% increase), while the anterior-posterior shear component showed larger changes than those of compression, except in the most lateralized center position (Figure 2).

The higher joint loads in the lateralized joint centers reflect a shortening of the Deltoid muscle moment arms (Figure 3), since the muscle needs to exert more force to provide the desired motions. The additional shear forces generated by the lateralization may increase the risk of the ‘rocking-horse’ effect. Together with the lateralized joint center, this creates an additional bending stress at the bone-implant interface that puts the implant at further risk of loosening (Figure 1). Current studies on implant fixation tend to use loads in compression and superior shear that exceed the forces seen in this study but have not investigated anterior-posterior shear loads. Our data support that loading in anterior-posterior direction can be significant. Using inappropriate loads to design fixation may result in excessive loss of bone stock and/or unforeseen implant loosening. The implication is that future studies may be performed using this more relevant data set to navigate the tradeoff between fixation and bone conservation.


Luca Cristofolini Lorenzo Zani Mateusz M. Juszczyk

BACKGROUND

In vitro tests have shown that when a force is applied to the proximal femur within the range of directions spanned during physiological activities, the direction of principal strain vary by a very narrow angle (Cristofolini et al, 2009, J. Engng. Med.). This shows that the anatomy and the distribution of inhomogeneous and anisotropic material properties of the bone tissue make the structure of the proximal femur optimized to withstand a wide range of loading directions.

The increasing use of hip resurfacing is associated with early neck fractures of the implanted femur. The aim of this study was to elucidate if such fractures could be caused by a non-physiological state of stress/strain post-implantation. While the possible role of notching at the neck-implant interface has already been elucidated, it is not know whether a resurfacing implant could make the principal strain vary in magnitude and direction in a way that could compromise integrity of the proximal femur.

METHODS

The aim of this study was to measure if the direction of the principal strain in the proximal femur was affected by the presence of a resurfacing prosthesis. Seven human cadaver femurs were instrumented with 12 triaxial strain gauges to measure the magnitude and alignment of principal strains in the head-neck region. Each femur was implanted with a typical resurfacing prosthesis (BHR). All femurs were tested in vitro before and after implantation with a range of loading conditions to explore the range of loading directions during daily activity (Fig. 1).


Darryl D'Lima Jonathan Netter Nikolai Steklov Juan Hermida Peter Chen Jim Nevelos

Introduction:

Microseparation has resulted in more than ten-fold increase in ceramic-on-ceramic and metal-on-metal bearing wear, and even fracture in a zirconia head [1–4]. However, despite the greater microseparation reported clinically for metal-on-polyethylene wear, less is known about its potential detrimental effects for this bearing couple. This study was therefore designed to simulate the effects of micromotion using finite element analysis and to validate computational predictions with experimental wear testing.

Methods:

Experimental wear rates for low and highly crosslinked polyethylene hip liners were obtained from a previously reported conventional hip wear simulator study [5]. A finite element model of the wear simulation for this design was constructed to replicate experimental conditions and to compute the wear coefficients that matched the experimental wear rates. We have previous described out this method of validation for knee wear simulation studies [6,7]. This wear coefficient was used to predict wear in a Dual-Mobility hip component (Fig 1).

Dual mobility total hip arthroplasty components, Restoration ADM (Fig 1), with highly crosslinked acetabular liners were experimentally tested: the control group was subjected to wear testing using the ISO 14242-1 waveform on a hip wear simulator. The microseparation group was subjected to a nominal 0.8 mm lateral microseparation during the swing phase by engaging lateral force springs and reducing the swing phase vertical force.


Yifei Dai Jian Yao Jeffery Bischoff

INTRODUCTION:

Successful tibial component placement during total knee arthroplasty (TKA) entails accurate rotational alignment, minimal overhang, and good bone coverage, each of which can be facilitated with a tibial component that matches the resected tibial surface. Previous studies investigated bony coverage of multiple tibial component families on digitized resections. However, these studies were based on manual placement of the component that may lead to variability in overhang and rotational alignment. An automated simulation that follows a consistent algorithm for tibial component placement is desirable in order to facilitate direct comparison between tibia component designs. A simulation has been developed and applied to quantify tibial coverage in multiple ethnicities, including Japanese, Indian, and Caucasian. Here, this approach is taken to evaluate tibial coverage of five contemporary tibial designs in Chinese subjects.

METHODS:

Digital models of 100 healthy Chinese tibiae (50 male, 50 female; age 68 ± 3 years; stature 1.65 ± 0.10 m) were virtually resected at 5° posterior slope referencing the anterior border of the proximal tibia, 0° varus/valgus rotation referencing the tibial mechanical axis, and 8 mm off the unaffected plateau (reflecting a 10 mm surgical cut, assuming a cartilage thickness of 2 mm). Neutral internal/external (I/E) alignment axis was derived from the medial third of the tubercle and the PCL attachment site.

Five commercial tibial designs (Design A, Deluxe™, Montagne, Beijing, China; Designs B-E contemporary market-established symmetric designs from four US manufacturers) were virtually placed on the resected tibiae following an automated algorithm, which maximizes component size while ensuring proper rotational alignment (within 5° I/E) and minimizing overhang (<1 mm in zones 1–4, Fig 1). Tibial coverage (posterior notch excluded, zone 5 in Fig 1) and distance from the component to the exterior cortex of the tibia in four clinically relevant anatomical zones (anterior medial, anterior lateral, posterior medial, and posterior lateral, zones 1–4, Fig 1) were calculated. Statistical significance was defined at p < 0.05.


Richard Komistek Mohamed Mahfouz Ray Wasielewski Thibaut De Bock Adrija Sharma

INTRODUCTION:

Previous modalities such as static x-rays, MRI scans, CT scans and fluoroscopy have been used to diagnosis both soft-tissue clinical conditions and bone abnormalities. Each of these diagnostic tools has definite strengths, but each has significant weaknesses. The objective of this study is to introduce two new diagnostic, ultrasound and sound/vibration sensing, techniques that could be utilized by orthopaedic surgeons to diagnose injuries, defects and other clinical conditions that may not be detected using the previous mentioned modalities.

METHODS:

A new technique has been developed using ultrasound to create three-dimensional (3D) bones and soft-tissues at the articulating surfaces and ligaments and muscles across the articulating joints (Figure 1). Using an ultrasound scan, radio frequency (RF) data is captured and prepared for processing. A statistical signal model is then used for bone detection and bone echo selection. Noise is then removed from the signal to derive the true signal required for further analysis. This process allows for a contour to be derived for the rigid body of questions, leading to a 3D recovery of the bone. Further signal processing is conducted to recover the cartilage and other soft-tissues surrounding the region of interest. A sound sensor has also been developed that allows for the capture of raw signals separated into vibration and sound (Figure 2). A filtering process is utilized to remove the noise and then further analysis allows for the true signal to be analyzed, correlating vibrational signals and sound to specific clinical conditions.


Francesca De Caro Massimo Berruto Marco Delcogliano Giulia Carimati Giovanni Ziveri Francesco Uboldi Paolo Ferrua Carlo De Biase Antonio Delcogliano

Background:

Different surgical approaches have been proposed for the treatment of chondral lesions. However surgical management of osteochondral defects of the knee joint involving subchondral bone are still under debate.

Purpose:

The aim of this prospective non-randomized uncontrolled clinical investigation is to confirm the effectiveness of a commercially available biomimetic osteochondral scaffold in regenerating cartilage and subchondral bone of severe osteochondral lesions of the knee joint with one step surgery.


Danielle De Villiers Amy Kinbrum Alison Traynor Simon Collins Sarah Banfield Jonathan Housden Julia Shelton

Introduction

Vitamin-E has been introduced into highly-crosslinked polyethylene liners to reduce the oxidation potential of the material while maintaining low wear rates. However, little has been reported on adverse testing of the material with one test on diffused vitamin-E polyethylene [1] and no adverse tests of vitamin-E blended polyethylene reported. Adverse testing of crosslinked polyethylene has focused on the use of large diameters, the incorporation of third body particles, roughening of the counterface or severe activity [2–4]. This investigation considers the wear of vitamin-E blended highly-crosslinked polyethylene under standard and adverse conditions articulating against uncoated and chromium nitride (CrN) coated metal heads.

Methods

Seven metal heads were tested against prototype ϕ52 mm 0.1 wt% vitamin-E blended highly-crosslinked polyethylene liners (Corin, UK). Three heads remained as cast double heat treated metal (MoP) while four, of similar metallurgy, were coated with CrN via electron beam physical vapour deposition (CrNoP) (Tecvac, UK) and polished to a similar surface finish. Tests were conducted for 5 million cycles (mc) under conditions described in ISO 14242–3: 2009. Alumina particles (mean size 2.4 μm) at concentrations of 0.15 mg/mL were added to the lubricant for 1 mc to consider the effect of severe head damage. Testing continued for a further 1 mc without the presence of the particles and then 3 jogging intervals (14,400 cycles each) were conducted at slow, medium and fast speeds [3]. Wear volume was determined gravimetrically for the heads and liners and fluid collected throughout the testing was analysed for cobalt concentration using graphite furnace atomic absorption spectroscopy.


Jeffrey DeClaire Adolph Lombardi Keith Berend

Background:

Coronal malalignment occurs frequently in total knee arthroplasty (TKA) and reduces implant longevity and function. Designed to improve consistency and efficiency, patient- specific positioning guides (PSPG) generated from preoperative imaging studies represent a paradigm shift from manual instrumentation (MI) and intraoperative computer navigation.

Purposes:

We compare the efficacy of PSPG to MI in (1) restoring mechanical axis of the extremity and (2) achieving neutral alignment of the femoral and tibial components.


Francesca De Caro Carlo De Biase Giovanni Ziveri Marco Delcogliano Mario Borroni Alessandro Castagna

Introduction:

Reverse shoulder arthroplasty (RSA) is a reasonable treatment modality in patients with Cuff Tear Arthropaty and massive irreparable cuff tears. RSA has been shown to increase patient function and decrease pain. The aim of this study is to evaluate the clinical and radiographic results of a 44 polyethylene glenosphere.

Methods:

Since 2008 we treated 88 patients with cuff tear arthropaty and irreparable massive cuff tear, using an RSA. We selected 80 patients with minimum FU of 24 months in which we used an implant with polyethylene glenosphere and metal humeral insert. Size of the glenosphere used was 44. All patients were assessed with the Constant score and with VAS. The shoulder ROM was measured preoperatively and postoperatively.


Hendrik Delport Luc Labey Jos Vander Sloten Johan Bellemans

Today controversy exists whether restoration of neutral mechanical alignment should be attempted in all patients undergoing TKA. The restoration of constitutional rather than neutral mechanical alignment may in theory lead to a more physiological strain pattern in the collateral ligaments, and could therefore potentially be beneficial to patients.

It was therefore our purpose to measure collateral ligament strains during three motor tasks in the native knee and compare them with the strains noted after TKA in different postoperative alignment conditions. Six cadaver specimens were examined using a validated knee kinematics rig under physiological loading conditions. The effect of coronal malalignment was evaluated by using custom made tibial implant inserts in order to induce different alignment conditions.

The results indicated that after TKA insertion the strains in the collateral ligaments resembled best the preoperative pattern of the native knee specimens when constitutional alignment was restored. Restoration to neutral mechanical alignment was associated with greater collateral strain deviations from the native knee.

Based upon this study, we conclude that restoration of constitutional alignment during TKA leads to more physiological periarticular soft tissue strains during loaded as well as unloaded motor tasks.


Ajit Deshmukh Jose Rodriguez Charles Cornell Vijay Rasquinha Amar Ranawat Chitranjan S Ranawat

Introduction:

Severe bone loss creates a challenge for fixation in femoral revision. The goal of the study was to assess reproducibility of fixation and clinical outcomes of femoral revision with bone loss using a modular, fluted, tapered distally fixing stem.

Methods:

92 consecutive patients (96 hips) underwent hip revision surgery using the same design of a modular, fluted, tapered titanium stem between 1998 and 2005. Fourteen patients with 16 hips died before a 2-year follow-up. Eighty hips were followed for an average of 11.3 years (range of 8 to 13.5 years). Bone loss was classified as per Paprosky's classification, osseointegration assessed according to a modified system of Engh et al, and Harris Hip Score was used to document pain and function. Serial radiographs were reviewed by an independent observer to assess subsidence, osseointegration and bony reconstitution.


Alexander Dickinson Andrew Taylor Anne Roques Martin Browne

Introduction:

Novel biomaterials may offer alternatives to metal arthroplasty bearings. To employ these materials in thin, bone conserving implants would require direct fixation to bone, using Titanium/HA coatings. Standard tests are used to evaluate the adhesion strength of coatings to metal substrates [1], versus FDA pass criteria [2]. In tensile adhesion testing, a disc is coated and uniform, uniaxial tension is exerted upon the coating-substrate interface; the strength is calculated from the failure load and surface area. Rapid failure occurs when the peak interface stress exceeds the adhesion strength, as local failure will propagate into an increasing tensile stress field.

Ceramics and reinforced polymers (e.g. carbon-fibre-reinforced PEEK), have considerably different stiffness (E) and Poisson's Ratio (ν) from the coating and implant metals. We hypothesised that this substrate-coating stiffness mismatch would produce stress concentrations at the interface edge, well in excess of the uniform stress experienced with coatings on similar stiffness metals.

Methodology:

The interface tensile stress field was predicted for the ASTM F1147 tensile strength test with a finite element analysis model, with a 500 μm thick coating (50 μm dense Ti layer, 450 μm porous Ti/HA/adhesive layer), bonded to a stainless steel headpiece with FM1000 adhesive (Fig. 1). Solutions were obtained for:

Configuration A: ASTM-standard geometry with Ti-6Al-4V (E = 110GPa, ν = 0.31), CoCrMo (E = 196GPa, ν = 0.30), ceramic (E = 350GPa, ν = 0.22, e.g. BIOLOX delta) and CFR-PEEK (E = 15GPa, ν = 0.41, e.g. Invibio MOTIS) substrates.

Modified models were used to analyse oversized substrate discs:

Configuration B: coated fully and bonded to the standard diameter headpiece, and

Configuration C: Coated only where bonded to the headpiece.


Pramod Kumar Puthumanapully Natalie Shearwood-Porter Mary Stewart Rick Kowalski Martin Browne Alexander Dickinson

Introduction

Implant-cement debonding at the knee has been reported previously [1]. The strength of the mechanical interlock of bone cement on to an implant surface can be associated with both bone cement and implant related factors. In addition to implant surface profile, sub-optimal mixing temperatures and waiting times prior to cement application may weaken the strength of the interlock.

Aims

The study aimed to investigate the influence of bone cement related factors such as mixing temperature, viscosity, and the mixing and waiting times prior to application, in combination with implant surface roughness, on the tensile strength at the interface.


Pramod Kumar Puthumanapully Mary Stewart Martin Browne Alexander Dickinson

Introduction

Fatigue and wear at the head/stem modular junction of large diameter total hip replacements can be exacerbated as a result of the increase in frictional torque. In vivo, a “toggling,” anterior-posterior (A-P) movement of the head taper on the trunnion may facilitate corrosion in the presence of physiological fluids, leading to increased metal ion release. Clinically, metal ion release has been linked to the formation of pseudo tumours and tissue necrosis [1].

Aims

In this investigation, a large diameter metal on metal THR was tested on a rig designed to recreate the toggling motion at the head/stem junction. Post-test analyses are conducted to look for evidence of mechanical and corrosive damage.


Benjamin Domb Youssef El Bitar Timothy Jackson Dror Lindner Itamar Botser Christine Stake

Background:

Acetabular cup positioning1, 2, leg length discrepancy3 and global offset4 are important parameters associated with outcomes following total hip arthroplasty (THA). Deviation from an accepted range of values for each of these parameters can lead to significant complications including nerve injury, low back pain, abnormal gait, increased dislocation rate, and bearing surface wear. The primary purpose of this study was to assess whether the use of the MAKO™ robotic hip system is reliable in predicting post-operative radiographic measurements of cup inclination, cup anteversion, leg length change, and global offset change in THA.

Materials and Methods:

All robotic-assisted THAs performed using the MAKO™ system between June 2011 and Dec 2012 were reviewed. A single surgeon performed all cases through a mini-posterior approach. The intra-operative measurements of cup inclination and anteversion angles, leg length change, and global offset change recorded by the MAKO™ system were compared to the post-operative radiographic measurements.


Michelle Burgett Thomas Donaldson Ian Clarke

In an effort to understand the role of metal ion analysis and how it relates to revision surgery and implant wear, four revised MOM cases were reviewed. The first case was revised for acute infection and is representative of the low bearing wear predicted by MOM simulator studies. Two of the four cases had apparent anterior subluxation as a result of hip hyperextension occurring with long stride gaits. The last case is a true hypersensitivity response to CoCr ions.

All four MOM prostheses were implanted by one surgeon and revised by the same surgeon approximately 6–8 years postoperatively. The implants had been positioned satisfactorily with inclination angles 45°–55° and anteversion angles 28°–42°.

Patient A (76 y/o female) with bilateral MOM hip replacements, was revised at approximately 8 years due to infection and had moderately elevated ions at the time of revision surgery (Co = 5, Cr = 2.3, Ti = 4). Only the femoral head was retrieved in this case. Retrieval analysis identified a well defined main-wear zone and one polar stripe. The CMM indicated there was minimal wear overall (form factor = 11 μm).

Patient B (33 y/o male) with bilateral MOM hip replacements, was revised at approximately 8 years due to pain, popping/catching sensations, and elevated ions (Co = 33, Cr = 17, Ti = 90). Intraoperatively, the implant was observed subluxing superiorly from the acetabular cup with anterior rotation of the leg. Both the femoral head and acetabular cup were retrieved. Retrieval analysis identified a well defined main-wear zone and multi-directional polar stripe formations similar to those reported on dislocated implants (Figure 1)[McPherson 2012, 2013]. The CMM indicated that overall wear was significant (form factor > 100 μm).

Patient C (77 y/o female) was revised at approximately 6 years due to pain, suspected implant loosening, osteolytic cysts determined by CT, and highly elevated ions (co = 164, Cr = 45, Ti = 33). Intraoperatively, there was evidence of wear including darkly stained tissue and osteolytic cysts. Both the femoral head and acetabular cup were retrieved. Retrieval analysis identified a well defined main-wear zone and one polar stripe. CMM indicated considerable wear (head form factor > 200, cup form factor >300).

Patient D (45 y/o female) was revised at approximately 6 years due to pain, apparent reactive response joint effusion, and moderately elevated ions (Co = 5, Cr = 6, Ti = 71). Only the femoral head was retrieved. Retrieval analysis identified a well defined main-wear zone and one polar stripe. Minimal wear was indicated by CMM (form factor = 21).

These four cases demonstrate distinct failure models of MOM hips and their respective metal ion results. Due to the diversity of patient location, a variety of clinical labs were utilized for this patient population. Caution should be used in interpreting metal ion analysis, as there are still no standards.

Figure 1: Retrieval analysis of stripe wear identified on femoral head from patient B.

Figure 2: Femoral head from patient C showing broader polar stripe associated with anterior subluxation in comparison to narrow polar stripe found on femoral head from patient A.


Michelle Burgett Thomas Donaldson Yubisela Gonzales

The purpose of this study was to determine the survivorship for a single MOM implant series and create an affordable clinical follow-up model. A retrospective cohort of 104 primary MOM THA procedures (94 patients) were all performed by one surgeon at three local hospitals and have reached 7–12 years follow-up. Fifteen patients are now deceased and 16 patients have been lost to follow-up. In the remaining 63 patients, 8 are bilateral providing a total of 71 THA for study. The clinical follow-up model included: hip score, X-rays, ultrasound, and metal ion testing. Due to the diversity of patient location, a variety of clinical labs were utilized for metal ion analysis. Statistical methods included a Kaplan-Meier survival curve. Hip scores were available for all 71 THA and of these 61 had a hip score (HHS) above 80 (86%). Fifty-three X-rays were available and of these 42 (79%) were in the safe zone (inclination ≤55 and anteversion ≤35). Thirty-six ultrasounds were performed and of these two yielded fluid collections (6%). Metal ion concentrations in either whole blood or serum have been documented for 32 of 63 patients (51%). Three outliers were identified within the metal ion concentrations; Co ranged 0.3–71.1 ppb (average 7.9, median 3.6), Cr ranged 0–26.9 ppb (average 4, median 2.1) and Ti ranged 2–100 ppb (average 51.8, median 52). Three patients have been revised by the original surgeon and two patients are currently scheduled to undergo revision surgery. Of the three patients revised, only one had a documented wear problem resulting from anterior subluxation, while the other two were revised for femur fracture and infection. These results represent survivorship of 94.7% at 9 years and may be a result of anterior lateral approach performed by one surgeon in which 79% of cups were well placed.


H. Gene Dossett George J. Swartz Nicolette A. Estrada George W. LeFevre Bertram Kwasman

Introduction:

Recently there has been interest in an alternative method of aligning a total knee arthroplasty (TKA) referred to as kinematic alignment. The theoretical appeal of this method is that alignment of each patient's knee can be individualized through the use of preoperative imaging and computer software, with the goal of achieving pre-arthritic alignment through restoration of the axes of rotation of each particular knee. Clinical studies have evaluated the outcomes of this new alignment technique, but to date there have been no randomized controlled trials comparing kinematic alignment to mechanical alignment. This randomized controlled trial was conducted to compare kinematically aligned and mechanically aligned TKA outcomes of knee pain, function and motion at two years' post-op, along with a comparison of limb, knee, and implant alignment of the two methods.

Methods and Materials:

Forty-four patients were surgically treated with kinematically aligned TKA (figure 1) with the use of patient specific guides, and forty-four patients were surgically treated with mechanically aligned TKA with the use of conventional instruments. All patients underwent CT long leg scanograms after surgery, and outcomes data were collected at a minimum of 2 years. The patient, radiographic evaluator, and clinical evaluator were blinded as to the alignment method.


H. Gene Dossett

The development of the High Reliability Organization focused on safety in organizations such as nuclear power plants, to avoid catastrophes in an environment where accidents might be expected due to risk factors and complexity. (Figure 1) The Agency for Healthcare Research and Quality applied High Reliability Concepts to hospitals in an effort to improve safety and quality.

The Institute for Healthcare Improvement has further expanded this approach to include establishing processes to ensure highly reliable care through analysis, design or redesign, using a model for improvement, and supported by technology and the physical environment.

These concepts can be applied to total knee replacement by identifying key processes, conducting regular measurement and analysis, and ensuring daily problem solving to create and maintain process reliability.

The application of patient specific technology to our conventional total knee replacement procedures creates an opportunity to improve both quality and safety in total knee replacement procedures. Preoperative imaging and use of computer software allows the surgeon to develop an individual blueprint for each operative procedure. A patient specific cutting guide is fabricated for use in surgery. Intra-operative measurement of bone cuts with comparison to the planned blueprint allows correction of inaccurate bone cuts during surgery. Post operative CT scanning provides a final accurate check of limb, knee and implant alignment in 3 dimensions, with comparison to the preoperative plan. Feedback from the surgeon to the engineers involved in the planning process allows daily improvement of the guide fit, cut accuracy and accuracy of limb, knee and implant alignment for these procedures.

Patient reported outcome measures such as the Oxford Knee Score or WOMAC score can be carried out preoperatively and at 6 months post op, to assess reduction of pain and functional improvements resulting from the operative procedure.

Ongoing annual patient surveillance using the 12 questions on the Oxford Knee Score, one question about satisfaction, and one question asking if the patient has undergone further surgery on the operative knee, can help assess the durability of the patient outcomes and the longevity of the prosthesis.

Use of patient specific cutting guides, coupled with preoperative software for planning a kinematically aligned TKA, has demonstrated improved RCT outcomes at the Phoenix VA. Figure 2 compares the distribution of WOMAC scores for kinematically aligned and mechanically aligned TKA. Individualizing the alignment for each patient has narrowed the distribution of the scores, with 87% of the kinematically aligned scores better than the median score for mechanically aligned patients.

There have been additional recent preoperative, perioperative and postoperative processes and checklists designed to increase quality and safety of TKA. Medical team training for preoperative briefing and post operative debriefing, use of the AAOS new STEPPS training program, monitoring post operative results with the NSQIP/VASQIP program and database give us additional tools to improve safety and quality. Coupled with patient specific alignment technology, I believe we currently have an excellent opportunity to move toward High Reliability in total knee replacement.


Michael Conditt Thomas Coon Martin Roche Andrew Pearle Todd Borus Frederick Buechel Jon Dounchis

INTRODUCTION

Successful clinical outcomes following unicompartmental knee arthroplasty (UKA) depend on component positioning, soft tissue balance and overall limb alignment which can be difficult to achieve using manual instrumentation. Recently, robotically guided technology has been used to improve post-operative implant positioning, and limb alignment in UKA with the expectation that this will result in greater implant longevity. This multi-center study examines the survivorship of this robotically guided procedure coupled with a novel, anatomically designed UKA implant at two years follow up.

OBJECTIVES

This study examines the two year survivorship and patient satisfaction of an anatomically designed UKA implant using a new robotically guided technology that has been shown to improve implant positioning and alignment.


Matthew Dressler Benjamin Owens Amber Metcalfe Chadd Clary Mark Heldreth

Introduction

For many patients, total knee replacement (TKR) provides pain relief and restores motion for many years [1]. Some patients, however, experience early failures and require revision surgery. One of the suggested contributors to early failure has been excessive wear due to malalignment [2]. Previous work has shown that varus-valgus malalignment results in extreme condylar loading and could lead to high wear [3]. The purpose of this experiment, therefore, was to evaluate medial/lateral load sharing in an in vitro wear simulation.

Methods

Wear testing was conducted on midsized Attune and Sigma fixed bearing cruciate substituting TKR components (DePuy Synthes). The two systems differ in many aspects; notably, Attune employs antioxidant-stabilized moderately-crosslinked polyethylene and a gradually changing sagittal femoral curvature while Sigma uses remelted moderately-crosslinked polyethylene and a mulit-radius femoral design. Wear was evaluated across a wide range of medial/lateral (M/L) load splits: 10/90, 60/40, and 90/10 using an AMTI six-station knee simulator (Figure 1). Simulation was conducted for 3 million cycles using at 1 Hz using previously described methods [4] with ‘High Kinematic’ displacement controlled inputs in 25% bovine calf serum (Hyclone) at 37 ± 2°C supplemented with sodium azide and EDTA. Polyethylene wear was determined gravimetrically with load soak compensation every 0.5 Mcyc.


Lynsey Duffell Jameel Mushtaq Milad Masjedi Justin Cobb

It has been proposed that higher knee adduction moments and associated malalignment in subjects with severe medial knee joint osteoarthritis (OA) is due to anatomical deformities as a result of OA [1, 2]. The emergence of patient-matched implants should allow for correction of any existing malalignment. Currently the plans for such surgeries are often based on three dimensional supine computed tomography (CT) scans or magnetic resonance imaging (MRI), which may not be representative of malalignment during functional loading. We investigated differences in frontal plane alignment in control subjects and subjects with severe knee joint OA who had undergone both supine imaging and gait analysis.

Fifteen subjects with severe knee OA, affecting either the medial or lateral compartment, and 18 control subjects were selected from a database established as part of a larger study. All subjects had undergone gait analysis using the Vicon motion capture system. OA subjects had undergone routine CT scans and were scheduled for knee joint replacement surgery. Control subjects had no known musculoskeletal conditions and had undergone MRI imaging of hip, knee and ankle joints. Frontal plane knee joint angles were measured from supine imaging (supine) and from motion capture during standing (static) and during gait at the first peak ground reaction force (gait).

OA subjects had a significantly higher BMI (p < 0.01) and different gender composition (13 males and 2 females vs 4 males and 5 females; p = 0.03) compared with controls. Multiple linear regression analysis indicated no significant confounding effect of these differences on frontal plane angles measured in supine, static or gait conditions.

For both OA and healthy subjects, frontal plane knee angles were significantly higher during gait compared with supine (p = 0.03 and 0.02, respectively). There were also significant differences in knee alignment between OA and healthy subjects for supine and static (p < 0.05) but not for gait, although this was approaching significance (p = 0.052). Overall there seemed to be higher variation in alignment in the OA subjects (Fig. 1).

The significantly higher frontal plane knee joint angles measured in both control and OA subjects during gait compared with supine imaging indicate that functional alignment should be taken into consideration when planning patient-specific surgeries. Higher variation in OA patients may be due to alterations in gait patterns due to pain or degree of wear in their osteoarthritic joints, and requires further investigation. In addition, methodological considerations should be taken when comparing alignment from measurements taken with imaging and motion capture to avoid systematic errors in the data. In conclusion, we believe that both supine and loadbearing imaging are insufficient to gain a full representation of functional alignment, and analysis of functional alignment should be routinely performed for optimal surgical planning.


Michael Duffy Kartik Mangudi Varadarajan Thomas Zumbrunn Harry E Rubash Henrik Malchau Andrew Freiberg Orhun Muratoglu

Introduction

Large diameter femoral heads provide increased range-of-motion and reduced dislocation rates compared to smaller diameter femoral heads. However, several recent studies have reported that contemporary large head prostheses can directly impinge against the local soft tissues leading to anterior hip pain. To address this we developed a novel Anatomically Contoured large diameter femoral Head (ACH) that maintains the profile of a large diameter femoral head over a hemispherical portion and then contours inward the distal profile of the head for soft-tissue relief. We hypothesized that the distal contouring of the ACH articular surface would not affect contact area. The impact of component placement, femoral head to acetabular liner radial clearance, and joint loading during different activities was investigated.

Methods

A finite element model was used to assess the femoroacetabular contact area of a 36 mm diameter conventional head and a 36 mm ACH (Fig. 1). It included a rigid acetabular shell, plastically deformable UHMWPE acetabular liner, rigid femoral head and rigid femoral stem. The femoral stem was placed at 0°, 10° and 20° of anteversion. The acetabular shell and liner were placed in 20°, 40° and 60° of abduction and 0°, 20° and 40° of anteversion. The femoral head to acetabular liner radial clearances modeled were 0.06 mm, 0.13 mm and 0.5 mm. Three loading cases corresponding to peak in vivo loads during walking, chair sit and deep-knee bend were analyzed (Fig. 2). This allowed a range of component positions and maximum joint loads to be studied.


Michael Duffy Kartik Mangudi Varadarajan Thomas Zumbrunn Harry E Rubash Henrik Malchau Andrew Freiberg Orhun Muratoglu

Introduction

Dual mobility (DM) implants provide increased stability and range-of-motion through the use of a large diameter mobile liner articulating against an acetabular shell. However, recent studies have reported that such contemporary large head prostheses can directly impinge against the local soft tissues leading to anterior hip pain. To address this drawback, a novel Anatomically Contoured Dual Mobility (ACDM) liner was developed that maintains the outer spherical geometry over an approximately hemispherical portion and then contours inward the distal profile of the DM liner for soft-tissue relief. The extent of the inner profile encapsulating the small diameter head is increased to provide more coverage of the head and maintain the inner head pullout force. We hypothesized that the ACDM liner for soft-tissue relief would not affect retention of the small diameter inner head or liner-acetabular load-bearing contact area.

Methods

A finite element model to evaluate head retention and contact mechanics was created with a rigid acetabular shell, a plastically deformable UHMWPE DM liner, a rigid femoral head and a rigid femoral stem. For the head retention analysis, the extent of head coverage (Fig. 1) was optimized to match the inner head pullout force of a conventional DM liner. Contact mechanics of a conventional DM and ACDM liner were analyzed at the maximum joint load of three activities: gait, deep-knee bend and chair sit. One set of simulations was completed with the mobile liner and head axes aligned and another with the axes mal-aligned so that the mobile liner rim was adjacent to the femoral stem neck and the potential area of contact was away from the mobile liner apex. This allowed a broader range of potential contact to be assessed including what was determined to be a worst-case alignment.


Richard Dyrkacz Urs Wyss Jan-M Brandt Thomas Turgeon

Introduction

This retrieval analysis study consisted of two goals. The first goal was to determine if there was a difference in the corrosion and fretting damage along the taper interface between large femoral heads in comparison to monopolar hemiarthroplasty heads. The second goal was to examine if the diameter of monopolar hemiarthroplasty heads can influence corrosion and fretting damage along the taper interface.

Patients and Methods

This retrieval analysis compared the corrosion and fretting behaviour of 40 mm femoral heads (n = 13) to monopolar hemiarthroplasty heads (n = 17 for a diameter < 50 mm; n = 6 for a diameter ≥ 50 mm) such that all implants had a minimum implantation period of three months, a 12/14 mm taper, and the heads and stems consisted of CoCr alloy. The 40 mm heads articulated with a polyethylene cup whereas the monopolar hemiarthroplasty heads articulated with cartilage. The 40 mm heads were manufactured from one company whereas the monopolar hemiarthroplasty heads were manufactured from four different companies. Corrosion and fretting damage were assessed using a previous technique [1]. Table 1 lists the patient information and reasons for revision whereas Table 2 provides the implant information.

The Mann Whitney U test and the Kruskal-Wallis test were performed for identifying significant differences for corrosion and fretting scores that were not normally distributed (α = 0.05). An unpaired student's t-test was conducted for comparing the head corrosion scores for the two head size groups of monopolar hemiarthroplasty implants since these scores were normally distributed.


Eric Greber C. Lowry Barnes Marty Bushmiaer Rebecca Wilson Paul Edwards Cara Petrus

Periprosthetic joint infections (PJI) continue to be a diagnostic challenge for orthopedic surgeons. Chronic PJI are sometimes difficult to diagnose and occasionally present in a subclinical fashion with normal CRP/ESR and/or normal joint aspiration. Some institutions advocate for routine use of intraoperative culture swabs at the time of all revision surgeries to definitively rule out infection. The purpose of this study is to determine whether routine intraoperative cultures is an appropriate and cost effective method of diagnosing subclinical chronic PJI in revision joint replacement patients with a low clinical suspicion for infection.

We performed a retrospective chart review and identified 33 patients that underwent revision hip or knee replacement from a single surgeon over a five-month period. The AAOS guidelines for preoperative PJI workup were followed. 13 patients were diagnosed preoperatively with infection and excluded from the study. 20 patients underwent revision joint replacement and three separate cultures swabs were taken for each patient to help in determining true-positive cultures. Infectious Disease was consulted for all patients with any positive culture. Culture results were reviewed. At our hospital, the cost billed to insurance for a single culture is $1,458.58. We did not calculate the cost of the consultant fee.

Three (15%) of the 20 revision arthroplasty patients had a single positive culture. Infectious Disease consultants diagnosed all three of these positive cultures as contaminants. None of the patients had a true-positive intraoperative culture. The total cost billed by the hospital to obtain these cultures in all 20 patients was $87,514.80

In our study, obtaining a set of three intraoperative cultures for those patients with a negative preoperative infection workup was not only cost prohibitive but did not diagnose a single subclinical infection. Studies to find other more reliable, accurate, and cost effective alternatives to diagnose PJI are warranted.

In patients undergoing revision hip or knee arthroplasty with a low preoperative clinical suspicion for infection, it does not seem that routine intraoperative culture swabs are necessary or cost effective method for diagnosing subclinical periprosthetic joint infection.


Lowry Barnes Paul Edwards D. Gordon Newbern

PURPOSE:

Medicare intermediary denial of primary joint replacements has become common over the past couple of years. Our community hospital had a marked increase in denials following the assignment of a new intermediary. Our purpose is to document the initial impact of these denials.

METHODS:

A retrospective review of the first 361 Medicare total joints (181 hips and 180 knees) after a new intermediary began processing claims was performed. Initial denial rate, positive response rate to first appeal, as well as delay in payments because of these denials were documented


Denis Nam Marci Elpers Susie Boydston-White Michael Ast Douglas E Padgett Timothy Wright

Introduction:

Concerns remain regarding both the toughness of alumina, and stability of zirconia ceramics in total hip arthroplasty (THA). A zirconia-toughened alumina (ZTA) bearing has been introduced, in which yttria-stabilized, zirconia polycrystals are uniformly distributed in an alumina matrix. The goal is to combine the wear resistance of alumina with the toughness of zirconia. Zirconia's toughness is attributed to a tetragonal to monoclinic (t-m) phase transformation that occurs in response to a crack, hindering its propagation; however, it might decrease material stability. The purposes of this study were to investigate the degree and position of metal transfer, and the occurrence of t-m phase transformation using Raman spectroscopy, in a series of retrieved, ZTA femoral heads.

Materials and Methods:

Twenty-seven ZTA femoral heads were reviewed as part of an IRB-approved implant retrieval program. All acetabular liners were composed of highly cross-linked polyethylene. The length of implantation, age, body mass index (BMI), sex, and reason for revision were recorded.

Two independent graders assessed each femoral head for metal transfer over three regions (apex, equator, and below equator), using a previously validated grading system (Figure 1). The female trunnion of each head was graded in two regions: the deep and superficial 50% (Figure 2).

Raman spectra were collected with a confocal Raman imaging system (alpha300 R, WITec, Knoxville, TN) operating a 488 nm laser, using a microscope objective of 20X. Three scans were taken in each of the aforementioned regions of the femoral head surface. Scans were also performed in regions of visible wear or metal transfer.

Interobserver correlation coefficients for the measurement of metal transfer between the two graders were determined. One-way ANOVAs were used to compare differences of metal transfer between the 3 surface regions (p < 0.05 = significant).


Lizeth Herrera Aaron Essner Jason Longaray Mark Kester Peter Bonutti

Demand for TKR surgery is rising, including a more diverse patient demographic with increasing expectations [1]. Therefore, greater efforts are being devoted to laboratory testing. As a result, laboratory testing may set a clinical performance presumption for surgeons and patients. For example, oxidized ZrNB (Oxinium) femoral components have been projected to show 85% less wear than CoCr femoral components in bench-top testing [2]. However, recent clinical data show no difference in outcomes between Oxinium® and CoCr for the same design [3]. While it does not show lagging peformance for the Oxinium components, it does call into question the predictive ability of simulation. To better understand the performance of these two materials, a non standardized simulator evaluation was conducted.

One commercially available design (Legion PS) was evaluated with two variations of femoral component material (n = 3/material) Oxinium® and Cobalt Chromium. All testing was conducted using a 7.5 kGy moderately crosslinked UHMWPE (XLPE). A 6-station knee simulator was utilized to simulate stair-climbing kinematics. The lubricant used was Alpha Calf Fraction serum which was replaced every 0.5 million cycles for a total of 5 million cycles. Soak controls were used to correct for fluid absorption and statistical analysis was performed using the Student's t-test.

Total wear rate results for the tibial inserts are shown in Figure 1. There was no statistical difference in volume loss (p = 0.8) or wear rate (p = 0.9) for the Oxinium® system when compared to the CoCrsystem under stair-climbing kinematics. Visual examination revealed typical wear scars and features on the condylar surfaces, including burnishing.

These results corroborate the recent clinical data showing no difference between Oxinium® components and their CoCr analogs [3]. The kinematics used here are not a combination of normal level walking with stair-climbing conditions as was published originally for the Oxinium® material [2], but stair-climbing kinematics only. Even though the stair-climbing profile utilized here does not represent standardized kinematics, it provided results that are in line with clinical observations for these femoral materials. Logic suggests that a combined duty cycle is more representative of patient behavior so there must be additional test factors contributing to the prediction previously reported. The goal of bench top testing is to simulate actual clinical performance so test models must be validated as clinicaly relevant in order to be predictive. Furthermore, the results of this test indicate that the different femoral materials evaluated in this study do not alter the wear characteristics of this TKR. This is further supported by a similar previous study showing the relative contribution of design versus materials in terms of wear behavior [4]. The main determination comes from clinical evidence, and as it has been demonstrated by Kim, et al [3], there is no significant difference in the clinical results of the two TKR devices analyzed.


Sally Arno Joseph Fetto Christopher Bell Konstantinos Papadopoulos Peter Walker

INTRODUCTION:

The purpose of this study was to determine if a short femoral stem (Lima Corporate, Udine, Italy) would result in a strain distribution which mimicked the intact bone better than a traditional length stem, thereby eliminating the potential for stress-shielding.

METHODS:

A 2 mm thick moldable plastic (PL-1, Vishay Micromeasurements, Raleigh, NC) was contoured to six fourth-generation composite femoral bones (Pacific Research Laboratories, Vashon, WA). The intact femurs were then loaded (82 kg) in a rig which simulated mid-stance single limb support phase of gait (Figure 1). During testing, the femurs were viewed and video recorded through a model 031 reflection polariscope. Observing the photoelastic coating through the polariscope, a series of fringes could be seen, which represented the difference in principal strain along the femur. The fringes were quantified using Fringe Order, N, as per the manufacturers technical notes. In order to analyze the strain distribution, the femur was separated into 6 zones, 3 lateral and 3 medial, and the maximum fringe order determined. Upon completion of testing of the intact femur, the short length femoral stem was inserted and tested, and finally the traditional length femoral stem was inserted and tested. Anterior and lateral radiographs were obtained of the femur with each femoral stem in order to confirm proper alignment.


Joseph Fetto

355 non-cemented MOM arthroplasties, of a single surgeon, with a follow up of 3–16 years (avg. 7.5 years) were retrospectively reviewed for evidence of pseudotumor and aseptic mechanical failure. There were 186 with 28 mm heads, 126 with 34 mm heads, 47 with 38 mm heads, from a single manufacturer.

There were 5 revisions of 38 mm heads for atraumatic painful “metalosis” 4–8 years after implantation (10.7%).

There were 4 revisions of 34 mm heads for post-traumatic instability (dislocation) with secondary metalosis 4–7 years after implantation (3.1%)

There were 2 revisions of 28 mm heads for post-traumatic instability (dislocation) with secondary metalosis 6–12 years after implantation (1.1%).

There were 5 patients, all with 38 mm heads, with asymptomatic “psoas bursae” with elevated serum CR and Co levels (1.0–3.0).

All of the failed THR's had acetabular components with lateral tilt <50 degrees (35–50), and anteversion angles <15 degrees (0–15). 2 of the 34 mm and both 28 mm instabilities were the consequence of injuries sustained in motor vehicle accidents. The remaining 2 instabilities with 34 mm implants were the result of mechanical falls.

Particulate debris, whether secondary to polyethylene, ceramic or metal articulations has been well documented as a cause of synovitis and damage to bony and soft tissues adjacent to a THR. This debris appears to be the result of material wear and mechanical failure with use over time. Unlike native articular cartilage, these materials are incapable of self-lubrication. Therefore THR articulations are dependent upon the penetration of ambient synovial fluid to provide lubrication of the replacement surfaces. This study suggests that increase in head diameter may reduce penetration of synovial fluid between the articulating surfaces of a THR, compromising the lubrication of bearing surfaces; thereby contributing to accelerated wear and premature failure of larger MOM arthroplasties.


Clare K. Fitzpatrick Chadd Clary Paul J. Rullkoetter

Introduction:

While survivorship of total knee arthroplasty (TKA) is excellent, up to 25% of patients remain dissatisfied with their outcome [1, 2]. Knee instability, which is common during high demand activities, contributes to patient dissatisfaction [3]. As younger patients undergo TKA, longevity requirements and functional demands will rise [4]. Design factors influence the functional outcome of the procedure [5, 6], although in clinical studies it can be difficult to distinguish joint mechanics differences between designs due to confounding variability in patient-related factors. The objective of the current study was to assess the stability and mechanics of several current TKA designs during high-demand dynamic activities using a computational model of the lower limb.

Methods:

Three high-demand dynamic activities (gait, stepdown, squat) were simulated in a previously described lower limb model (Fig. 1) [7]. The model included calibrated tibiofemoral (TF) soft-tissue structures, patellofemoral (PF) ligaments and extensor mechanism [8]. Loading conditions for the simulations were derived from telemetric patient data in order to evaluate TKA designs under physiological kinematic and loading conditions [7, 9]. Four fixed-bearing TKA designs (both cruciate-retaining (CR) and posterior-stabilizing (PS) versions) were virtually implanted into the lower limb model and joint motion, contact mechanics and interface loads were evaluated during simulation of each dynamic activity.


Mark Frankle

Reverse total shoulder arthroplasty was developed to address the treatment of patients with Cuff Tear Arthropathy. Despite of the clinical improvements seen with initial reverse shoulder replacements, several mechanical problems remain. Scapular notching has been reported between 24.5% and 96% of cases. Patients have also exhibited limited external rotation, either from impingement or slackening of remaining cuff musculature. Additionally, by medializing and moving the humerus distally, patients note a loss of the normal deltoid contour leading not only to cosmetic concerns, but possibly decreasing deltoid efficiency and creating a prosthesis with less inherent stability. Finally, although mechanical failure on the glenoid side initially was thought to be uncommon, various glenoid sided problems have been reported.

Recognition of these problems led to clinical and basic science studies aimed at improving surgical technique and the design of reverse shoulder implants. During the last 10 years, our institution has been conducting biomechanical research examining the forces across the glenohumeral joint. Several different models have been created to replicate mechanical failures by integrating biomechanical information with our clinical investigations, including altering the position of the implant (tilt), the type of fixation of the implant (screw or peg), and glenoid-sided bone loss. We were able to address glenoid component failure (with initial rates of 10% in our clinical studies) by recommending locking screws to neutralize forces at the fixation site. These discoveries have reduced glenoid-sided fixation failures to less than 0.1%.

In vitro kinematic function and factors that affect impingement free glenohumeral motion of reversed implants is another area of interest. The clinical relevance of impingement includes scapular-notching, pain from impingement, instability and excessive prosthetic wear. Several models that include motion in three different planes (flexion-extension, abduction-adduction and internal-external rotation) have been developed to study multiple prosthetic, technique and anatomic factors which can result from varying degrees of impingement. By integrating the results from these models into our clinical practice (e.g., selecting a more lateralized glenosphere, selecting a varus humeral component and inferiorly translating the glenoid component on the glenoid surface), we have been able to maintain low rates of notching (∼10% at 8 year follow-up). Finally, our current work involves development of a model that attempts to understand which factors might be influential in causing instability and stiffness. Thus, biomechanics research offers an excellent opportunity for interdisciplinary collaboration to solve complex clinical problems.


Ryan Freed Melinda Harman

Introduction:

Femoral head surface roughness has been recognized as an important determinant of linear and volumetric polyethylene (UHMWPE) wear in total hip replacement (THR), particularly for metal heads. Fisher et al1 found that a 2- μm scratch with a 1- μm buildup of metal debris produced a 70-fold increase in the wear rate. Ceramic materials and hard-on-hard bearing couples have been introduced to provide more scratch resistance. However, THR bearing surfaces of all materials can become damaged during in vivo function, potentially impacting wettability. The purpose of this study is to quantify surface roughness as related to distinct damage types on retrieved femoral heads and to assess wettability of common bearing materials.

Materials and Methods:

An IRB-approved archive of retrieved THR bearing components was queried, identifying 29 metal (CoCr) and ceramic (alumina, zirconia) femoral heads that had articulated with UHMWPE and ceramic acetabular liners, respectively. Mean in vivo functional duration was 5.5 ± 4.5 years (range, 1 month to 27 yrs), and patient age and weight averaged 68 ± 12 years (range, 36–81) and 72 ± 21 kilograms (range, 52–123), respectively. Retrieval reasons were dislocation (18), loosening (4), polyethylene wear (2), infection (1), squeaking (1) and unknown (3). Damage appearance and surface roughness were evaluated in a grid pattern of 49 zones distributed across the bearing surface of each head using optical microscopy to identify Mode-1 or Mode-2 wear and a non-contact interferometer (NT2000 & NPFLEX, Bruker Corp.) Wettability of smooth and rough CoCr and alumina materials was assessed using contact angle measurements (DSA30, Krüss USA).


Nicholas Frisch Jakub Sikora-Klak Craig Silverton

Introduction:

Demand for total hip arthroplasty (THA) continues to rise and as such there is a concurrent presumed increase in the incidence of periprosthetic femoral fractures. Several studies have previously demonstrated differences in fixation technique and biomechanical advantages of various cerclage constructs in fixation of femoral periprosthetic fractures. The purpose of this study is to determine the most effective combination of cerclage materials and technique in fixation of of periprosthetic fractures during cementless THA.

Methods:

Thirty fourth generation synthetic femora were tested in axial compression and torsion. Femurs were placed in a standardized mount and a press fit hip prosthesis was implanted by one senior surgeon. After broaching but prior to implant placement, a band saw was used to create a Vancouver B1 fracture below the level of the lesser trochanter. The implant was then placed in the femur. Four different cerclage constructs were then created using two of the following: 1) hose clamp, 2) metallic cable, 3) synthetic cable, 4) monofilament wire. All cables were placed using tensioning devices to standardize final cerclage tension. Additional constructs were created increasing the number of cerclage cables/wires to three and then four, evenly spaced across the implant. Axial compression and torsion were assessed to failure for all constructs using standard Instrom testing criteria. Cost analysis was performed for each construct.


Simon Frostick Margaret Roebuck John Davidson Alasdair Santini Viju Peter Joanne Banks Amanda Williams Haiyi Wang Jecko Thachil Richard Jackson

Introduction:

Wear debris from articulating joint implants is inevitable. Small debris particles are phagocytosed by macrophages. Larger particles initiate the fusion of many macrophages into multi-nucleated giant cells for particle encasement. Macrophages are recruited into inflamed tissues from the circulating monocyte population. Approximately 10% of white blood cells are monocytes which after release from the bone marrow circulate for 2–3 days, before being recruited into tissues as inflammatory macrophages or undergoing apoptosis. Circulating MRP8/14 (S100A8/A9) is a measure of monocyte recruitment, part of the monocyte-endothelial docking complex, and shed during monocyte transmigration across the endothelium. The higher the S100A8/A9 the more monocytes being recruited giving an indirect measure of debris production.

Methods:

2114 blood samples were collected from arthroplasty patients with hip or knee osteoarthritis (primary, post-traumatic and secondary), 589 before their primary arthroplasty, 1187 patients > 1 year post-arthroplasty, 101 patients before revision for aseptic loosening and 237 patients >1 year post-revision. Plasma S100A8/A9 was measured using BMA Biomedicals Elisa kit, normal levels in health adults are 0.5–3 mg/ml. Joint specific scores, WOMAC knee or Oxford Hip adjusted to percent of maximum, together with SF-12 were completed.


Simon Frostick Amanda Williams Haiyi Wang John Davidson Alasdair Santini Jecko Thachil Joanne Banks Richard Jackson Margaret Roebuck

Introduction:

The risk factors for degenerative joint disease are well established: increasing age, obesity, joint abnormalities, trauma and overuse, together with female gender, ethnic and genetic factors. That obesity is a significant risk factor for developing osteoarthritis in non-weight-bearing as well as weight-bearing and joints was one of the first indications that the risk was nor purely that of aberrant biomechanical loading. Low grade chronic systemic inflammation is a component of each of ageing and obesity, atherosclerosis and diabetes, culminating in Metabolic Syndrome. In our study of 1684 patients with joint degeneration 85% were overweight or obese and 65% older than 65 years with 62% being both, 73% of patients were taking medications for serious, ‘non-orthopaedic’ health problems such as cardiovascular or respiratory disease, obesity or NIDDM. Monocytes are a major component of chronic inflammation, approximately 10% of white blood cells are monocytes which circulate for 2–3 days, before being recruited into tissues as inflammatory macrophages or undergoing apoptosis. Circulating S100A8/A9 (MRP8/14) is a measure of monocyte recruitment being shed during monocyte transmigration across the endothelium. The higher the S100A8/A9 the more monocytes being recruited giving an indirect measure of chronic inflammatory status.

Methods:

2154 blood samples were collected from arthroplasty patients (first or second joint replacement), 1135 Female and 1019 Male, age 29–93 years, body mass index (BMI) 18–56, with hip or knee osteoarthritis (primary, post-traumatic and secondary), 589 before a primary arthroplasty, 1187 patients >1 year post-arthroplasty, 101 patients before revision for aseptic loosening and 237 patients >1 year post-revision. All study patients received metal on UHMWPE implants. Plasma S100A8/A9 was measured using BMA Biomedicals Elisa kit, normal levels in healthy adults are 0.5–3 mg/ml. The data were analysed using SPSS, p values were calculated using Spearman's test.


Hiroshi Fujita Tomoo Okumura

Purpose

One of the drawbacks of cemented total hip arthroplasty (THA) is aseptic loosening after long period, major reason for which is bioinertness of PMMA bone cement. To improve longevity of THA, interface bioactive bone cement (IBBC) technique which is characterized with smearing hydroxyapatite (HA) granules just before cementation has been used in our institute.

Objective

Smooth-surfaced triple-tapered Titanium-alloy stem (T) and Exeter stem (E) have been used consecutively in the different period. Objective of the present study was thoroughly comparing two stems clinically and radiologically.


Kazuo Fujiwara Hirosuke Endou Yoshiki Okada Yohei Kagawa Toshifumi Ozaki

Objectives

The setting angle of the cup is important for achieving the stability and avoiding the dislocation after total hip arthroplasty (THA). It is difficult to set the cup at correct angle in minimally invasive THA by modified Watson-Jones approach. So we use CT-based navigation system. We evaluated the accuracy of with post-operative CT data.

Materials and Methods

We treated 30 hips in 30 patients (7 male and 23 females) by navigated THA. 26 osteoarthritis hips, 2 rheumatoid arthritis hips and 2 idiopathic osteonecrosis hips were performed THA with VectorVision Hip 3.5.2 navigation system (BrainLAB). Implants were AMS HA cups and PerFix stems (Kyocera Medical, Osaka). Appropriate angles and positions of cups were decided on the 3D model of hip joint before operation. According to the preoperative planning, we put the cups with navigation system and stems without navigation system. We measured the anteversion angle with post-operative CT data and 3-dimensional template software.


Kiyokazu Fukui Ayumi Kaneuji Tanzo Sugimori Toru Ichiseki Tadami Matsumoto

Background

The rotational acetabular osteotomy (RAO), that was developed in Japan, has been used successfully in patients with developmental dysplasia of the hip (DDH) (Figure 1). However there are some patients who are forced to have a total hip arthroplasty (THA) due to the progression of osteoarthritis. It is unknown if a RAO poses technical difficulties or increases the chances of complications if a THA must be performed afterwards becausethere is not much data on patients who underwent a THA after a previous RAO.

Objectives

The purpose of this study was to investigate the mid-term results of a THA after a RAO.


Olimpio Galasso Massimo Mariconda Matteo Sticozzi Giorgio Gasparini

BACKGROUND:

Modern total hip arthroplasty (THA) has shown a great improvement in pain, function and range of motion of patients but data on patients' quality of life after this surgery as assessed by validated tools are lacking.

METHODS:

In this cohort study we evaluated the quality of life and functionality of 250 patients an average of 16 years (11–23) after THA using the SF-36 questionnaire, the Harris Hip Score, the WOMAC score, the Functional Comorbidity Index, and a study specific questionnaire. Models of multiple stepwise linear and logistic regression analysis were constructed to evaluate the relationships between the explanatory variables and the functional outcomes.


Bo Gao Laurent Angibaud

Introduction

Total knee arthroplasty (TKA) prostheses are semi-constrained artificial joints. Femorotibial constraint is a key property of a TKA prosthesis and should be designed to match the device's intended function. Cruciate Retaining (CR) prostheses are usually used for patients with a functioning posterior cruciate ligament (PCL). For patients without a fully functioning PCL, CR-Constrained (CRC) prostheses may be used. A CRC tibial insert usually has a more conforming sagittal profile especially in the anterior aspect to provide increased constraint to prevent paradoxical femoral translation during knee flexion. A quantitative understanding of the constraint behavior of a prosthesis design is critical to ensure its functional outcome. Using a validated computer simulation, this study evaluated the anterior-posterior (AP) constraint of two types of tibial inserts (CR and CRC) from a same TKA product family.

Methods

Both the CR and CRC prostheses are from the same TKA product family (Optetrak Logic, Exactech, USA). Three sizes (sizes 1, 3, and 5) from each product line were included in this study. Computer simulations using finite element analysis (FEA) were performed at 0° flexion per ASTM F1223 standard [1] (Figure 1). The simulation has been validated with physical testing (more details submitted in a separate abstract to ISTA 2013). Briefly, FEA models were created with all materials considered linear elastic. The tibial baseplate was distally fixed and a constant compressive force (710 N) was applied to the femoral component. Nonlinear Surface-Surface-Contact was established at the articulating surfaces. A coefficient of friction of 0.1 was assumed for all articulations [2]. The femoral component was driven under a displacement-controlled scheme to slide along AP direction on the tibial insert. Constraint force occurring at the articulation was derived from the reaction force at the distal fixation. A nonlinear FEA solver was used to solve the simulations.


Bo Gao Laurent Angibaud

Introduction

Ability to accommodate increased range of motion is a design objective of many modern TKA prostheses. One challenge that any “high-flex friendly” prosthesis has to overcome is to manage the femorotibial contact stress at higher flexion angle, especially in the polyethylene tibial insert. When knee flexion angle increases, the femorotibial contact area tends to decrease thus the contact stress increases. For a high-flex design, considerations should be taken to control the contact stress to reduce the risk of early damage or failure on the tibial insert. This study evaluated the effect of femoral implant design on high flexion contact stress. Two prostheses from a same TKA family were compared – one as a conventional design and the other as a high-flex design.

Methods

Two cruciate retaining (CR) prostheses from a same TKA product family were included in this study. The first is a conventional design for up to 125° of flexion (Optetrak CR, Exactech, USA). The second is a high-flex design for up to 145° of flexion (Logic CR, Exactech, USA). The high-flex design has a femoral component which has modified posterior condyle geometry (Figure 1), with the intent to increase femorotibial contact area and decrease contact stress at high flexion. Three sizes (sizes 1, 3, and 5) from each prosthesis line were included to represent the commonly used size spectrum. Contact stress was evaluated at 135° of flexion using finite element analysis (FEA). The CAD models were simplified and finite element models were created assuming all materials as linear elastic (Figure 2). For comparison purpose, a compressive force of 20% body weight was applied to the femoral component. The average body masses of sizes 1, 3 and 5 patients are 69.6 kg, 89.9 kg, and 106.3 kg based on the manufacture's clinical database. A nonlinear FEA solver was used to solve the simulation. Von Mises stress in the tibial insert was examined and compared between the two prostheses.


Andrea Gardner Laurent Angibaud Nick Stroud

Introduction

Ideally, a patient receiving a unicondylar knee replacement will have fully functional anterior and posterior cruciate ligaments. When at least one of the cruciate ligaments is not fully functional, femoral and tibial implant contact position can potentially increase along the anterior-posterior (AP) axis. Where unicondylar implant wear testing typically uses AP resistance assuming fully functional cruciate ligaments, the authors used reduced AP resistance intended to simulate deficient cruciate ligaments.

Methods

Optetrak Logic® Uni (Exactech Inc, Gainesville, FL USA) unicondylar test specimens featuring an all-UHMWPE tibial component and a cobalt chromium femoral component were used in this study. The system has a semi-constrained articular geometry. Testing was conducted at an independent testing facility (EndoLab GMBH, Thansau, Rosenheim, Germany). A four-station knee simulator was used (EndoLab knee simulator) with two unicondylar knee implants per station, giving a total of eight test specimens. Two different tibial fixation designs (keeled and peg) with identical articulating surfaces were tested. Tibial test specimens were 6 mm in thickness. Unloaded soak controls were stored in distilled water at 37°C. The test was conducted according to ISO 14243–1: 2009 [1]. Test specimens were immersed in calf serum (PAA GmBH, Cölbe, LOT B00111-5126) with a protein content of 20 g/l. Custom polyurethane molds allowed for individual component measurement. Per the ISO 14243-1, a 7% medial offset was incorporated into the set-up. The unicondylar knee implants were set at neutral position in extension. Tibial rotational restraint was 0.36 Nm/° and zero when the test specimen was within ± 6° of the reference position. This test was conducted with an AP resistance of 9.3N/mm to maximize AP displacement and simulate deficient cruciate ligaments. Typical unicondylar knee wear testing is conducted with an AP resistance of 44N/mm, which assumes functional cruciate ligaments.


Olimpio Galasso Giorgio Gasparini Roberto Castricini Valerio Mastroianni

BACKGROUND:

Few studies have evaluated at a medium-term follow-up the use of semiconstrained reverse shoulder arthroplasty (RSA) for primary glenohumeral osteoarthritis, massive rotator cuff tear, or cuff tear arthropathy excluding any other shoulder disease. Moreover, data on patients' quality of life after this surgery are lacking.

METHODS:

In this prospective cohort study, 80 patients were evaluated after an RSA for either primary osteoarthritis, massive rotator cuff tear, or cuff tear arthropathy with the Constant-Murley score (CMS), ROM, and Short Form Health Survey (SF-36). A radiologic assessment was performed pre- and postoperatively.


Ryuichi Gejo Hiraku Motomura Makiko Nogami Kazuhito Sugimori Tomoatsu Kimura

Introduction:

One of the important factors for success in TKA is to achieve proper stability of the knee joint. It is currently unknown that how much joint laxity exists in mid-range to deep knee flexion, postoperatively. We hypothesized that retaining the PCL or not during TKA has an influence on the postoperative joint laxity from mid-range to deep knee flexion. The purpose of this study was to investigate the postoperative coronal joint laxity throughout the full range of motion by the 3-dimensional in vivo analysis, both in PS and CR TKA.

Methods:

We implanted 5 knees with a PS TKA using a NexGen LPS-flex and 5 knees with a CR TKA using a NexGen CR-flex. All of them were the osteoarthritis patients. We performed all operations with a measured resection technique. Four weeks after TKA, the valgus- and varus-stress radiographic assessments were performed at the five flexion angles from full extension to maximum flexion. The patients sat on the radiolucent chair with their lower legs hanging down. The examiner held their thigh, and a force of 50N was applied 30 cm distal to the tibiofemoral joint. The series of static fluoroscopic images via a flat panel detector were stored digitally. A 3-dimentional to 2-dimentional techniqueusing an automated shape-matching algorithm was employed to determine the relative 3-dimentional positions of the femoral component and tibial component in each fluoroscopic image (KneeMotion; LEXI, Tokyo). On the coronal plane of the tibial component, the angle between the tangent line of the condyles of the femoral component and the tibial plateau was measured as the joint laxity for valgus (α valgus) or varus (α varus). The flexion angle between the femoral component and tibial component was also measured.


Jeffrey Geller Scott AJ Thompson Barthelemy Liabaud Kate W Nellans

Indications for UKA for isolated osteoarthritis of the knee remain controversial. 229 UKA that were performed at our institution were evaluated for which factors was associated with a poor outcome. BMI > 35 was correlated with lower KSS scores than patients with BMI < 35. In contrast to prior reports, patients younger than 60 years old had higher scores than patients 60 years and older at 2 years. Women had an unacceptably high short-term revision rate for any reason of 6.5%. Popularity for UKA has increased, and a more in depth investigation of predictors of poor outcomes demonstrates that younger patients appear to have better results. Obese patients continue to improve up to 2 years after surgery and should not be precluded from undergoing UKA.


Jeffrey Geller Shane Dickerson David Patrick Barthelemy Liabaud

The study is a prospective series of the functional outcomes of total knee arthroplasty (TKA) with a novel bi-cruciate stabilizing prosthesis (BCS TKA) compared to a Posterior stabilized (PS) TKA. Between 2008 and 2012, 63 BCS TKA were performed on 56 patients (71 knees) and 54 patients underwent 56 PS TKA with a primary diagnosis of degenerative osteoarthritis, all performed by a single surgeon. Patients completed the Short-Form 12 and WOMAC Index questionnaires pre-operatively and post-operatively at 3 months, 1 year, and 2 years with range of motion determined in the office setting. Regarding the BCS knees, significant improvements in post-operative range of motion were noted, and results of the WOMAC pain component were promising at all intervals tested. However, measures of overall knee function including the WOMAC physical function and stiffness scores in addition to Knee Society Functional Scores saw a slight decline during the second post-operative year. Results from the PS knee implants showed similar trends, and no statistically significant differences were found between the two cohorts throughout functional follow-up; however the ranges of motions appear to be increased in the BCS knee cohort.


Bastiaan Ginsel Ross Crawford Lance Wilson Takkan Morishima Sarah Whitehouse

Introduction:

The risk for late periprosthetic fractures is higher in patients treated for a neck of femur fracture compared to those treated for osteoarthritis. It has been hypothesised that osteopenia and consequent decreased stiffness of the proximal femur are responsible for this. We investigated if a femoral component with a bigger body would increase the torque to failure in a biaxially loaded composite sawbone model.

Method:

A biomechanical composite sawbone model was used. Two different body sizes (Exeter 44-1 vs 44-4) of a polished tapered cemented stem were implanted by an experienced surgeon, in 7 sawbones each and loaded at 40 deg/s internal rotation until failure. Torque to fracture and fracture energy were measured using a biaxial materials testing device (Instron 8874). Data are non-parametric and tested with Mann-Whitney U-test.


Bastiaan Ginsel Ross Crawford Sarah Whitehouse Ahmed Taher

Aim:

This prospective cohort study investigated whether the use of preoperative anticoagulants is an independent risk factor for the outcomes of surgical treatment of patients with a neck of femur fracture.

Methods:

Data was obtained from a prospectively collected database. All patients admitted for a neck of femur fracture between Nov 2010 and Oct 2011 were included. This resulted in three hundred twenty-eight patients with 330 neck of femur fractures. Four groups were defined; patients preoperatively (i) on aspirin (n = 105); (ii) on clopidogrel (n = 28); (iii) on warfarin (n = 30); and (iv) without any anticoagulation history (n = 167, the control group). The non-warfarin group included the aspirin group, clopidogrel group and the control group. Primary outcome was the in-hospital mortality. Secondary outcomes were the postoperative complications, return to theatre and length of stay.


Tyler Goldberg W. Todd Curry Jared W. Bush

The present IRB approved study evaluates the early results of 100 TKAs using CT-based Patient-Specific Instrumentation (PSI) (MyKnee®, Medacta International, SA, Castel San Pietro, Switzerland). For this technique, a CT scan of the lower extremity is obtained, and from these images, the knee is reconstructed 3-dimensionally. Surgical and implant-size planning are performed according to surgeon preference, with the goal to create a neutral mechanical axis. Once planned and approved, the blocks are made [Fig. 1].

Outcomes measured for the present study include surgical factors such as Tourniquet Time (TT) as a measure of surgical efficiency, the actual intraoperative bony resection thicknesses to be compared to the planned resections from the CT scan, and complication data. Furthermore, pre- and post-operative long standing alignment and Knee Society Scores (KSS) were obtained.

During surgery, the PSI cutting block is registered on the femur first and secured with smooth pins. No osteophytes are removed as the blocks use the positive topography of the osteophytes for registration. The distal femoral resection is performed directly through the block. An appropriate sized 4-in-1 block is placed and the remaining resections are performed. The tibial resection block is registered and resection performed. Final bone preparation, patella resurfacing, and trialing is performed as is standard to all surgical techniques.

There were 50 Left and 50 Right TKA's performed in 61 females and 39 males. All patients had diagnosis of osteoarthritis. The average BMI was 31.1 and average age was 64.5 (range 41–90). 79 patients had pre-operative varus deformities with Hip Knee Angle (HKA) average of 174.7° (range 167°–179.5°). 19 patients had pre-operative valgus deformities averaging 184.4° (range 180.5°–190°). Three patients were neutral.

Average TT was 31.2 minutes (range 21–51 minutes). With regard to the bony resections, the actual vs. planned resections for the distal medial femoral resection was 8.7 mm vs. 8.9 mm respectively. Further actual vs. planned femoral resections include distal lateral 7.2 vs. 6.7 mm; posterior medial 8.3 vs. 8.9 mm; and posterior lateral 6.2 vs. 6.8 mm. The actual vs. planned tibial resections recorded include medial 6.4 vs. 6.3 mm and lateral 8.3 vs. 8.2. The planned vs. actual bony cuts are strongly correlated, and highly predictive for all 6 measured cuts (p=<.001) [Fig. 3]. No intraoperative complications occurred.

Average KSS improved from 45.9 to 81.4, and KSS Function Score improved from 57.7 to 73.5 at 6 weeks postoperative visit. There were no thromboembolic complications. Two patients had a post-operative infection requiring surgical intervention.

Post-operative alignment was 179.36° (range 175°–186°) for all patients. Alignment was neutral, within 3° in 95.9% of patients. There were only 4 outliers with maximal post-operative angulation of 6° [Fig. 2].

In conclusion, these early results demonstrate efficacy of CT-based PSI for TKA. The surgery can be performed efficiently, accurately, and safely. Furthermore, excellent short term clinical and radiographic results can be achieved.


W. Todd Curry Tyler Goldberg Jared W. Bush

Hardware in or about the knee joint presents a number of challenges to the surgeon in performance of Total Knee Arthroplasty (TKA). Conventional instrumentation usually requires a modification of technique or removal of the metallic implants. Computer-Assisted TKA (CAOS) is another option, but adds complexity and time to the procedure. MRI-based Patient-Specific Instrumentation (PSI) cannot be used as metal causes unwanted artifact and renders the images for planning, useless. However, CT scans are not affected by metal and thus CT-based PSI can be used in TKA patients with pre-existing hardware.

The present IRB approved study evaluates 12 consecutive knees (10 patients) with pre-existing hardware using CT-based PSI (MyKnee®, Medacta International, SA, Castel San Pietro, Switzerland).

In this technique, CT scan of the lower extremity is obtained, and from these images, the knee is reconstructed 3-dimensionally. Surgical and implant-size planning are performed according to surgeon preference, with the goal to create a neutral mechanical axis. Once planned and approved, the blocks are made [Fig 1].

During surgery, the PSI cutting block is registered on the femur first and secured with smooth pins. The distal femoral resection is performed directly through the block. An appropriate sized 4-in-1 block is placed and the remaining femoral resections are performed. The tibial resection block is registered and resection performed. Final bone preparation, patella resurfacing, and trialing is performed as is standard to all surgical techniques.

Of the 12 TKAs, there were 5 left and 7 right knees performed in 6 females and 6 males. The average BMI was 33.19 and average age was 53 (range 44–63). All diagnoses were either osteoarthritis or post-traumatic osteoarthritis. Follow-up averaged 59 weeks (range 18.6–113.7).

Nine patients had pre-operative varus deformities with HKA deformities average of 171.9° (range 154°–178.5°). One patient had pre-operative valgus deformity of 184.5°. Two patients were neutral (180°). Post-operative alignment for all patients (n = 11) was 179° (range 177°–180°). All patients were within 3° neutral, post operatively. Four patients measured 180°, 4 measured at 179°, 2 measured at 178°, and only one at 177°.

Hardware consisted of 5 patients with femur or tibia staples, 3 with plate(s) and screws [Fig. 2], 3 patients with ACL interference screws, and one titanium rod. No hardware was removed unless necessary for implantation. Only 3 patients required some hardware removal.

The pre-operative Range of Motion (ROM) averaged 2.9° to 98.3° (Extension range 0–15° and flexion range 30–115°). Post-operative ROM was 2.9° to 101.3°. (Extension range 0–5° and flexion range 65–125°). Knee Society Score (KSS) improved from 42.3 to 82.3, and KSS Function Score improved from 52.1 to 77.5. No intraoperative complications were recorded. Average tourniquet time was 42.1 minutes (range 28–102).

Regardless of the deformity, the patient's post-operative mechanical axes HKA averaged 179° (range 177–180). Clinical scores were typical for TKA patients with improvement in both KSS and ROM.

In conclusion, early results using PSI in patients with pre-existing hardware in or about the joint, is safe, efficient, and accurate in performance of TKA.


Eric Greber Marty Bushmiaer Lowry Barnes

Background:

Until recently, there has been no consensus of the best approach to dIfferentiating aseptic from septic loosening in joint replacement patients. The recent AAOS Clinical Practice Guideline Summary that was published in 2010, tasks orthopedic surgeons with the strong recommendation of obtaining ESR and CRP for all patients needing hip and knee arthroplasty revision surgery and aspirating the joint based upon these results. The purpose of this study is to determine from our patients whether this guideline has been helpful and cost effective in determining periprosthetic joint infections.

Methods:

We retrospectively reviewed charts of 50 consecutive patients who underwent revision total hip or knee arthroplasty. Each patient received an ESR and CRP level prior to operation and patients with known periprosthetic joint infections were excluded from the study. As guidelines recommend, aspiration with cultures and cell count were obtained on all knees with either elevated ESR or CRP and all hips with both ESR and CRP elevated. We then determined how many patients needing revision arthroplasty of the hip or knee benefited from ESR, CRP, and aspiration by finding subclinical periprosthetic infection and changing the intraoperative treatment. Hospital charge data was used to report cost of this protocol.


Fei Liu Thomas P Gross

Introduction:

One reason that young and active patients choose hip resurfacing arthroplasty (HRA) rather than stemmed total hip arthroplasty (THA) is that they wish to return to high impact sports after their operation. Few studies have addressed the outcome in hip arthroplasty patients who choose to participate in high impact sports post-operatively. We therefore wanted to determine if the durability of HRA in highly active patients was decreased.

Methods:

From 5/2001 to 5/2011, a single surgeon performed 2434 HRA cases in 2013 patients. The study group consists of all patients that had a UCLA Activity score of 9 or 10 at any point after surgery in our prospective database. There were 936 (38%) cases in 776 patients who reported participating in high impact sports at some point after surgery. This group was compared to the entire database. The mean age of the study group was 50 ± 8 years, which was significantly younger than the entire group (P = 0.0007). 82% of the study group was male compared to 73% in the entire group (P < 0.0001). 85% of the primary diagnoses were osteoarthritis in the study group compared to 78% in the entire group (P < 0.0001), followed by dysplasia (8%) and osteonecrosis (4%).


Fei Liu Thomas P Gross

Introduction:

Uncemented acetabular component fixation has been considered the most reliable fixation method in contemporary metal-on-metal hip resurfacing arthroplasty (HRA). During prospective long-term follow-up of a HRA device, we have encountered a surprisingly high incidence of this complication and wish to alert surgeons and manufacturers of this problem.

Methods:

The study group was comprised of all 373 HRAs performed by a single surgeon using this hybrid hip resurfacing implant from May 2001 to March 2005. The acetabular component features a dual-coated bone ingrowth surface of plasma-sprayed titanium plus hydroxylappatite. There were a total of 34 revisions identified at the time of this study.


Fei Liu Thomas P Gross

Introduction:

More and more metal-on-metal hip resurfacing arthroplasty (HRA) implants have been used for active younger patients because of its higher success rate and better function outcomes for this group of patients compared to the traditional total hip arthroplasty (THA). One of the advantages of HRA is femoral neck preservation, which provides better bone structure in case a revision is necessary in the future. However, some believe that the outcomes after revision of hip resurfacing were not as good as the traditional THA. The purpose of this study was to provide our outcomes of the revisions, due to various causes, from over 3000 HRAs.

Method:

Between May 2001 and April 2013, a single surgeon performed 3180 HRA. During that same period, 88 required revision (2.8%). Among them, the primary causes of the revision were acetabular component loosening in 22 cases; femoral component loosening in 21; femoral neck fracture in 19; adverse wear in eight; deep infection in four; and other causes for the rest. 68 of these revisions were performed by the same surgeon, while the remainder were revised elsewhere. 53 among these 68 cases had reached a minimum follow-up of two years and were included in this report. In 96%(51/53) of cases, the revision bearing was a large metal type including in 6/8 cases of adverse wear failure. There were eight cases of adverse wear with ion levels elevated above 10 μg/L, metalosis and inflammatory reaction seen at the time of revision. All of these cases had acetabular inclination angles larger than 50°. 7/8 of these cases were revised to another large metal bearing with improved acetabular component position. We analyzed the clinical scores, complications and radiographic results and compared them between these groups.


Shigong Guo Aroon Baskaradas Ian Holloway

Introduction

Reconstructing acetabular defects in revision hip arthroplasty can be challenging. Small, contained defects can be successfully reconstructed with porous-coated cups without bone grafts. With larger uncontained defects, a cementless cup even with screws, will not engage with sufficient host bone to provide enough stability.

Porous titanium augments were originally designed to be used with cementless porous titanium cups, and there is a scarcity of literature on their usage in cemented cups with bone grafting.

Methods

We retrospectively reviewed five hips (four patients – 3 women, 1 man; mean age 65 years) in which we reconstructed the acetabulum with a titanium augment (Biomet, IN, USA) as a support for impaction bone grafting and cemented acetabular cups (Figure 1). All defects were classified according to Paprosky classification. Radiographic signs of osseointegration were graded according to Moore grading. Quality of life was measured with the Oxford Hip Score.


Shantharam Shaetty Ajith Kumar Saurabh Gupta

Purpose

To validate accuracy of transepicondylar axis as a reference for femoral component rotation in primary total knee arthroplasty.

Methods

A prospective study done from dec 2010 to dec 2011 at tertiary centre. 80 knees were included (43 females and 21 males). All surgeries were carried out by one senior arthroplasty surgeon. All patients undergoing primary total knee replacement were included and all revision cases were excluded. Intraoperative assessment of TEA was done by palpating most prominent point on lateral epicondyle and sulcus on medial epicondyle and passing a k wire through it. Confirmation is done under image intensifier C arm with epicondylar view. Postoperative TEA was assessed by taking CT scan, measuring condylar twist angle and posterior condylar angle. Also correlation of femoral component rotation with postoperative anterior knee pain was assessed.


Shantharam Shaetty Ajith Kumar Saurabh Gupta

Purpose:

To compare accuracy of transepicondylar axis as a reference for femoral component rotation in primary navigated versus non navigated total knee arthroplasty in severely deformed knees.

Methods:

A prospective study done from dec 2009 to dec 2011 at tertiary centre. 180 knees were included (124 females and 56 males). All cases were randomly allocated into 2 groups: navigated and non navigated. All surgeries were carried out by two senior arthroplasty surgeons. All patients undergoing primary total knee replacement were included and all revision cases were excluded. Intraoperative assessment of TEA was done by palpating most prominent point on lateral epicondyle and sulcus on medial epicondyle and passing a k wire through it. Confirmation is done under image intensifier C arm with epicondylar view in Non navigated knees. Postoperative TEA was assessed by taking CT scan, measuring condylar twist angle and posterior condylar angle (PCA).


Saurabh Gupta Shantharam Shaetty Ajith Kumar

Purpose

To assesment of geometric center of knee as a reference for femoral component rotation in primary total knee arthroplasty.

Methods

A prospective study done from dec 2009 to dec 2011 at tertiary centre. 180 knees were included (124 females and 56 males). All cases were randomly allocated into 2 groups: navigated and non navigated. All surgeries were carried out by two senior arthroplasty surgeons. All patients undergoing primary total knee replacement were included and all revision cases were excluded. Postoperative geometric center of knee was assessed by taking CT scan.


Kim Haeussler Markus Flohr Roman Preuss Robert Streicher

Introduction

Dislocation is one of the major factors for revision surgery. Current literature states that the usage of larger bearing couples (> 36 mm) have the potential of reducing the risk of dislocation. Smaller ceramic-on-ceramic bearing couples (< 36 mm) have demonstrated very low wear rates. But does the wear behaviour change with increasing diameter? Therefore, the aim of this study was to compare wear rates of larger ceramic-on-ceramic bearing couples for total hip arthroplasty.

Materials and Methods

Wear tests according to ISO 14242 with 36, 40 and 44 mm zirconia platelet toughened alumina (ZPTA) bearings were performed in a servo-hydraulic hip simulator. In total, the specimens were loaded up to 5 million cycles. Wear was measured gravimetrically every million cycles. For each diameter three different combinations regarding clearance and roundness were chosen. One combination represented in tolerance parts (70 μm clearance, < 5 μm roundness). The other two combinations represented parts at the lower end and at twice the upper end of the tolerance band regarding clearance and out of specification parts regarding the roundness.


Keisuke Hagio Masanobu Saito Naotaka Tazaki Kohei Kushimoto Hiroshi Egami

Background:

Few clinical hip score include toe-reach motion after THA (put-on-socks, nail-cutting). Some reports have shown whether THA patients can put on socks or not in daily activity, and not shown how they can do it. The purpose of this study is to investigate real pattern of put-on-socks motion in daily activities after THA, and to evaluate safe range of motion for prevention of hip dislocation.

Materials and Methods:

Reviewing clinical chart, we investigated highly frequent pattern in wearing socks motion that would cause hip dislocation in ADL in 100 patients with normal lower extremities except for hip joint more than one year after THA, then, we classified the motion pattern. Using an optical 3-D motion analysis (MAC3D system, Motion Analysis, USA), we measured necessary angle of the hip in 10 THA subjects (mean age at operation 61 years old) one year postoperatively, while the patients make such frequent patterns of movement as above. Simultaneously, individual 3-dimensional skeletal model was reconstructed from CT data and implant CAD data. Driving 3-D skeletal model combined with motion analysis data on display (Zed Hip, LEXI), we calculated angle from posture that hip flexion angle was maximum during wearing-socks motion to impingement point (implant and/or bone) for each direction. ALL joint angle was defined as “zero” in supine position.


Sam Hakki

Introduction:

Purpose of mini-invasive hip arthroplasty, is least damage to skin and muscles. Unlike Roettinger modification to Watson-Jones, our approach requires no special table or instruments. Besides, direction of skin incision is perpendicular to interval between glutei and tensor muscles, thus called a Crisscross Approach. Incision is at direction of retractors causing less skin damage; and parallel to femur allowing expansion. No tendon or muscles are severed achieving a true inter-muscular non invasive approach. Unlike anterior approach, femoral circumflex vessels and lateral femoral cutaneous nerve are spared.

Material and Methods:

240 prospective patients underwent mini-invasive crisscross technique since December 2006. A standard non-cemented hip was implanted. Previously disrupted hip muscles patients were excluded. In the operating room, patients were secured in a lateral decubitus position with the pelvis flexed at 20°–30° to allow operated leg to extend beyond the table to be placed in a standard plastic bag. The anterior superior iliac spine (ASIS), the greater trochanter (GT) and its tubercle are identified and marked. A line is drawn between ASIS and GT tubercle representing the interval between the glutei and the tensor fascia lata muscles. Another line representing the skin incision is drawn perpendicular. It may be curved a little toward the femur starting two inches inferior and posterior to ipsilateral ASIS extending distally for 3 inches or more for obese or muscular patients. The Crisscross Approach starts with a skin incision being made as above and through the subcutaneous fat identifying the inter-muscular interval between the glutei and the tensor fascia lata. Sharp dissection is made in the connecting fascia only and blunt dissection is needed to separate the two muscles. A branch of the superior gluteal nerve proximally crossing from the glutei to the tensor fascia lata may be encountered but it should not be disturbed as long as blunt dissection is maintained. Curved retractors are placed one above and the other below the femoral neck exposing the anterior capsule. Incision is made in the capsule and the retractors are re-placed to better expose the femoral neck. The appropriate level of neck is osteotomized and the head is extracted as routine. Acetabulum is further exposed by placing the curved retractors at about mid anterior and mid posterior. The final appropriate cup size and orientation is implanted routinely. Before exposing the femoral canal the deep fascia at the junction of the glutei and the vastus lateralis should be incised (about 2–3 inches). This will tremendously help femoral canal exposure. Then the surgeon is positioned anterior, the patient is made fully paralyzed and the table is tilted 20°–30° posteriorly (away from the surgeon). Hip extended 20°–30°, externally rotated to 80°–90° and adducted with a retractor underneath femoral neck and a curved one on greater trochanter to protect the glutei. Leg is allowed to drop in a bag (posteriorly). Canal finder is helpful to avoid going through the cortex Broaching or reaming and final implant insertion as routine. Posterior capsule need not be disturbed; however, the superior and inferior capsule should be detached from the neck to allow better exposure of the femoral canal. Closure starts with one or two stitches in the remainder of the capsule. Then suture deep fascia at the junction of glutei and vastus lateralis with absorbable suture. Finally, subcutaneous fat and skin are closed as routine.


Sam Hakki Victor Bilaotta

Introduction:

Current pelvic plane software is not accurate and do not address normal acetabular center axis that has minimum impingement and maximum stability relation with femur in navigated THA

Methods:

A retrospective study of 137 consecutive THA, comparing ACA and APP registration data with postoperative pelvic CT, independently measuring acetabular and cup inclination and version. APP registration points were anterior superior iliac spines and symphysis pubis. Computer identifies preoperative ACA as ‘zero’ after averaging superior, anterior and posterior rim points of registration of acetabulum. Reaming and cup orientation is kept within 4 mm of ACA or within 5 degrees of inclination and anteversion of APP software to avoid impingement.


Sam Hakki William Mihalko Khaled J Saleh

Introduction

The prevalence of reversing of extension coronal deformity during flexion and how that may change the routine algorithm of soft tissue balancing in total knee arthroplasty (TKA) has not been published. We name this phenomenon, the reversing coronal deformity (RCD). We observed 12% (45 patients) of coronal deformities consistently reverse in flexion in the osteoarthritic knees before surgery. We conclude that RCD phenomena need to be addressed in every TKA and collateral ligament release need to be modified or avoided; otherwise postoperative flexion instability may be inevitable. Femoral rotation adjustment with posterior capsule release has to be attempted first in RCD patients.

Method

We define RCD as the reversing of a coronal extension deformity of more than 2° while the knee reaches 90°of flexion. That is to say a 2° or more varus knee in extension becomes a 2° or more valgus at 90° of flexion or vice versa.

We retrospectively analyzed, in a multicenter study the alignment patterns of 387 (US = 270, UK = 117) consecutive computer navigated TKA subjects (June 2004–May 2008). 364/387 (US = 252, UK = 112) subjects were eligible for analysis (23 subjects had incomplete data: US = 18, UK = 5). The coronal deformity kinematics was observed during the range of motion and the range of medial /lateral deflections were analyzed.


Thomas Halim Michelle Burgett Ian Clarke Thomas Donaldson

It has come to light that one significant mechanism for MOM failure may be repeated subluxation or impingement episodes leading to edge wear and release of 3rd body particles. This MOM debris-challenge model simulates a patient who experienced one subluxation or impingement event and then continues to walk normally until the next event occurs one week later. Our model assumes that 100–200 particles (debris size 100–200 μm) would be released into the joint space at each subluxation or impingement event. The question then becomes: what is the effect of the patient walking on that single dose of particulates over the next week (or 500,000 cycles in simulator test mode).

Nine 38 mm CoCrMo bearings (DJO Inc., Texas) were run inverted in a12-station hip simulator (SWM, Monrovia, CA). The test was run in standard simulator mode (Paul gait load cycle: 0.2–2 kN, frequency 1 Hz) with the addition of 5 mg of debris particles for the first 3 Mc, followed by 10 mg of debris particles from 3–5 Mc. Commercially available CoCr (ASTM F75) and titanium alloy (ASTM F136) particles and broken polymerized bone cement particles were used in the size range 50–200 μm. Serum was changed out every 500,000 cycles and a fresh dose of debris added. All bearings were ultrasonically cleaned and examined using white light interferometry (WLI, Zygo Corp) and SEM (EVO MA15, Zeiss). Wear rates were determined gravimetrically and serum discoloration was noted at each test interval.

Titanium alloy and CoCr debris produced darkened serum within the first hour of the test and remained so for the duration (500,000 cycles). Serum color with cement debris remained an opaque golden color throughout the test run. The debris challenge provoked the largest MOM wear response using Ti6Al4V particulates (6.7 mm3/Mc), slightly milder with CoCr particulates (4.5 mm3/Mc) and minimal with PMMA particulates (0.5 mm3/Mc). Compared to bone cement debris chambers (which had wear rates comparable to non abrasive MOM bearing tests), CoCr debris created a 9-fold higher MOM wear and titanium alloy debris created a 14-fold higher MOM wear. These observations indicated that only the metal debris elicited an ‘Adverse’ wear response with MOM bearings.


Kengo Harato Aiko Sakurai Yutaka Kudo Hidenori Tanikawa

Introduction

Skin closure methods are various in total knee arthroplasty (TKA). Subcuticular skin closure techniques, which do not require postoperative stitch removal, are considered to be useful for excellent cosmesis and patients' satisfaction. Basically, subcuticular skin closure provides the tightness and water-tight seal, which leads to loss of postoperative normal physiologic drainage. As a routine wound closure, we performed the subcuticular skin closure with use of absorbable sutures or barbed sutures without staples. According to some previous reports, subcuticular skin closure using barbed sutures resulted in worse clinical outcomes, comparing with conventional skin staples. However, little attention has been paid to the differences between conventional absorbable and barbed sutures in both capsular and subcuticular skin closures. Our purpose was to investigate the efficacy and safety of the barbed suture, comparing to conventional absorbable sutures in TKA.

Methods

A total of 81 knees in 75 patients (60 females and 15 males) were enrolled in the current investigation. Mean age was 73 (58–89) years old. All the subjects underwent unilateral or staged bilateral TKA using Balanced Knee System, posterior stabilized design (Ortho Development, Draper, UT). All knees were divided into two groups, as presented in Table 1. In conventional group, capsule was repaired using interrupted number 1 braided absorbable sutures, followed by closure of subdermal layer using a 3-0 monofilament absorbable suture with inverted interrupted knots. Thereafter, subcuticular skin closure was done using 4-0 monofilament absorbable suture, followed by adhesive tape. On the other hand, in barbed suture group, 1-0 and 4-0 unidirectional barbed suture (V-Loc, Covidien, Mansfield, Massachusetts) was used for capsule and subcuticular skin closure, respectively. Drains were removed on postoperative day 2. We evaluated closure time from capsule to skin, range of motion (ROM), Hollander Wound Evaluation Score (HWES: maximum score 6/6), and complications. Postoperative ROM and HWES were evaluated on postoperative day 14.

As a statistical analysis, the data was compared between groups using Mann-Whitney U-test and Fisher exact probability test. P-values of < 0.05 were considered as significant.


Shinichi Hasegawa Jun Mizutani Seiji Otsuka Nobuyuki Suzuki Muneyoshi Fukuoka Takanobu Otsuka Scott Banks

Introduction

Cervical orthoses are commonly used to regulate the motion of cervical spines for conservative treatment of injuries and for post-operative immobilization. Previous studies have reported the efficacy of orthoses for 2D flex-extension or 3D motions of the entire cervical spine. However, the ability of cervical orthoses to reduce motion might be different at each intervertebral level and for different types of motion (flexion-extension, rotation, lateral bending). The effectiveness of immobilizing orthoses at each cervical intervertebral level for 3D motions has not been reported. The purpose of this study is to evaluate the effectiveness of the Philadelphia collar to each level of cervical spines with 3D motion analysis under loading condition.

Patients & Methods

Patient Sample Four asymptomatic volunteer subjects were recruited and provided informed consent. Approval of the experimental design by the institutional review board was obtained. These 4 individuals were without any history of cervical diseases or procedures. The presence of any symptoms, spinal disorders and anatomical abnormalities in fluoroscopic images or CT was a criterion of exclusion from this study.

Outcome Measures To evaluate the efficacy of the Philadelphia collar, ANOVA was used to compare the range of motion with and without collar at the C3/4, C4/5, C5/6 and C6/7 intervertebral levels for each motion. The level of statistical significance was set at p < 0.05. When a statistical difference was detected, post hoc Tukey tests were performed.


Shinya Hayashi Takaaki Fujishiro Shingo Hashimoto Noriyuki Kanzaki Takayuki Nishiyama Masahiro Kurosaka

Introduction:

Implant dislocations are often caused by implant or bone impingement, and less impingement is critical to prevent dislocations. Several reports demonstrated that greater femoral offset delayed bony impingement and led to an improved range of motion (ROM) after THA. Therefore, an increase in the femoral offset may improve ROM and decrease implant dislocation. The aim of this study was to clarify the effect of the femoral offset in avoiding component or bony impingement after total hip arthroplasty (THA).

Methods:

Seventy-eight patients underwent THA with a Pinnacle cup and Summit stem (DePuy). Intraoperative kinematic analysis was performed with a navigation system, which was used to obtain intraoperative range of motion (ROM) measurements during trial insertion of stems of 2 different offset lengths with the same head size. Further, ROM was also measured after actual component insertion.


Nathanael Heckmann Reza Omid Lawrence Wang Michelle McGarry C. Thomas Vangsness Thay Lee

Background:

The purpose of this study was to compare the biomechanical effects of the trapezius transfer and the latissimus dorsi transfer in a cadaveric model of a massive posterosuperior rotator cuff tear.

Methods:

Eight cadaveric shoulders were tested at 0°, 30°, and 60° of abduction in the scapular plane with anatomically based muscle loading. Humeral rotational range of motion and the amount of humeral rotation due to muscle loading were measured. Glenohumeral kinematics and joint reaction forces were measured throughout the range of motion. After testing in the intact condition, the supraspinatus and infraspinatus were resected, simulating a massive rotator cuff tear. The lower trapezius transfer was then performed. Three muscle loading conditions for the trapezius (12N, 24N, 36N) were applied to simulate a lengthened graph as a result of excessive creep, a properly tensioned graph exerting a force proportional to the cross-sectional area of the inferior trapezius, and an over-constrained graph respectively. Next the latissimus dorsi transfer was performed and tested with one muscle loading condition 24N. A repeated-measures analysis of variance was used for statistical analysis.


Evan Argintar Nathanael Heckmann Lawrence Wang James Tibone Thay Lee

Background:

Individuals with large Hill-Sachs lesions may be prone to failure and reoccurrence following standard arthroscopic Bankart repair. Here, the Remplissage procedure may promote shoulder stability through infraspinatus capsulo-tenodesis directly into the lesion. Little biomechanicaldata about the Remplissage procedure on glenohumeral kinematics, stability, and range of motion (ROM) currently exists.

Questions/purposes:

What are the biomechanical effects of Bankart and Remplissage repair for large Hill-Sachs lesions?


Hakan Hedlund Li Fellander-Tsai

Background:

Hip arthroplasty is very successful in order to alleviate pain and improve health-related quality of life. Health-care costs are constantly growing and the burden of patients with hip disease has increased dramatically. Careful consideration of the patients'need and expectations include not only the proper indication for surgery but also choice of method. Hip resurfacing (HRA) has been popularized during the last decade, being bone conservative, capable to restore the anatomical hip center and lower the risk of dislocation. Some HRA-designs have proven good long-term survival rate while others have shown an unacceptable high amount of loosening and been recalled. Yet, for a selected group of patients HRA may be advantageous to THA regarding health-related quality of life. A fundamental prerequisite understanding today's and tomorrow's request on hip arthroplasty is to measure outcomes from patients' perspectives. In this pilot study we compared the patient-reported outcome measures after hip resurfacing with THA using validated general and hip disease specific instruments.

Methods:

A questionnaire was sent to 108 randomly selected patients (72% male) of a cohort of 259 patients (Charnley A+B) who had had uni- or bilateral (two stages) HRA for a period of at least six months. Maximal follow-up time was 7 years. Mean age was 50.2 years (males) and 46.2 years (females) respectively. Patients were reporting EQ-5D and self assessed health-quality (0–100%). In addition, a minor group randomly selected, reported their activity that was graded according to UCLA-activity score. As preoperative EQ-5D baseline, a matched group of 40 patients from the hospital's database scheduled for HRA served.


Masaru Higa Chih-Chiang Chang Christopher Roche Aimee Struk Kevin Farmrer Thomas Wright Scott Banks

Introduction

Persistent problems and relatively high complication rates with reverse total shoulder arthroplasty (RTSA) are reported (1, 2). It is assumed that some of these complications are affected by improper intraoperative soft tissue tension. Achieving proper intraoperative soft tissue tension is an obvious surgical goal. However, intraoperative soft tissue tension measurements and methods for RTSA have not been reported. One way to quantify soft tissue tension is to measure intraoperative joint forces using an instrumented prosthesis. Hence, we have developed an instrumented RTSA to measure shoulder joint forces intraoperatively. The goal of this study was to measure intraoperative shoulder joint forces during RTSA.

Materials and Methods

The instrumented shoulder prosthesis measures the contact force vector between the glenosphere and humeral tray. This force sensor is a custom instrumented trial implant that can be used with an existing RTSA system (EQUINOXE, Exactech Inc, Gainesville, FL) just as a standard trial implant is used. Four uniaxial foil strain gauges (QFLG-02-11-3LJB, Tokyo Sokki Kenkyujo Co., Ltd., JP) are instrumented inside the sensor. Using a calibration matrix, the three force components were calculated from four strain gauge outputs (3).

Sixteen patients who underwent RTSA took part in this IRB approved study. All patients were greater than 50 years of age and willing to review and sign the study informed consent form. After obtaining informed consent for surgery, a standard deltopectoral approach to the shoulder was performed. The instrumented trial prostheses were assembled on the glenoid baseplate instead of a standard glenosphere. After the joint was reduced, joint forces were recorded during cyclic rotation, flexion, scapular plane movement (scaption), and adduction of the shoulder. Strain gauge outputs were recorded during these movements as well as the neutral position just before movements. Mean values of forces with each motion were compared by one-way analysis of variance (ANOVA). A multiple comparisons test was subsequently performed to examine differences between motions.


Carlos Higuera Joseph Styron Gregory Strnad Joseph Iannotti

Introduction:

Total knee arthroplasty (TKA) outcomes drive assessment of quality and reinvestment; therefore a risk stratified assessment is paramount for fair evaluation. Stratification can be affected by multiple factors including patient motivation. This study attempted to identify the correlation of patient's preoperative confidence in their ability to return to desired activity level after TKA and improved function and outcomes.

Methods:

A continuous series of TKA procedures from 2008 to 2010 in a healthcare system was reviewed retrospectively. Patients included reported pre- and postoperative knee injury and osteoarthritis outcomes scores (KOOS), SF-12 scores, and responded a question regarding the desired activity level, including the level of confidence (0–10 scale) in attaining such goals, after surgery. Gender, age, body mass index, education level, smoking status, length of stay (LOS), 30-day readmission and reoperation, and 1-year infection rates were collected. Correlation of patient confidence in attaining treatment goals and the outcomes collected was established using multiple linear and logistic regression models adjusted for baseline mental and functional scores.


Kazunori Hino Masami Ishimaru Yoshio Onishi Hiromasa Miura

There are some reports that the invasive surgery of knee joint replacement repair static and dynamic balance. We investigated the changes in static and dynamic balance and muscle strength in pre- and postoperative of TKA and UKA for the purpose of assessing time dependent improvement.

A total of 168 patients (137 TKA; mean age 75.3, 31 UKA; mean age 78.1) were recruited to the study. These patients underwent static and dynamic balance assessment and muscle strength pre operation and 3, 6, 12 months post operation. The parameters of assessment were one leg standing time (open or close eyes), postural sway test (open or close eyes), 3m timed-up-and-go test, maximum stride and Isokinetic muscle strength. We have evaluated both the absolute value and the index which divided the value of the post-operation with the value of pre-operation.

Alignment had improved significantly after surgery in TKA and UKA. Isokinetic muscle strength (Fig. 1), one leg standing time with open eyes, 3m timed-up-and-go test (Fig. 2) and maximum stride showed better improvement than pre operation at 3, 6, and 12 months after surgery in TKA and UKA. On the other hand, one leg standing time with close eyes and postural sway test showed no improvement than pre operation at any time after operation (Fig. 3). Butpostural sway test in UKA showed the improvement trend at 3 months after surgery. In contrast, those test in TKA showed no improvement at 3 months after surgery (Fig. 3).

Our result showed the improvement of balance function correlated with muscle recovery and improvement of lower limb alignment than equilibrium function after the artificial knee joint replacement surgery. Because one leg standing time with close eyes and one leg postural sway test represent the equilibrium function than other tests. It is interesting that significant difference in the recovery of postural sway in three months after surgery in UKA compared with TKA.


Shunji Hirokawa Michihiko Fukunaga

Knowledge of joint kinematics in the lower limb is important for understanding joint injuries and diseases and evaluating treatment outcomes. However, limited information is available about the joint kinematics required for high flexion activities necessary for floor sitting life style. In this study, the hip and knee joint kinematics of ten healthy male and ten healthy female subjects were investigated using an electromagnetic motion tracking system. We measured the hip and knee joints' functions moving into 1) kneeling on knees with legs parallel without using arms, 2) kneeling on knees with legs parallel with using arms, 3) kneeling on knees with one foot forward without using arms, 4) cross-legged sitting, 5) kneeling with legs to the side, 6) sitting with legs stretched out, and 7) deep squatting, and moving out of the above seven conditions. Conditions 1) through 3) were Japanese seiza style. On conditions 4) through 7), arms were not used. We further measured the functions of putting on and taking off a sock under such conditions as 8) with standing position and 9) sitting position (Fig 1). Here special attention was paid for flexion and extension motion. The data were used to produce the pattern of joint angulation against the percentage of the cycle for each individual conducting each activity. The kinematic curves were split into 3 phases: moving into the rest position, the rest position and out of the rest position. It should be noted that the moving into and the rest phases were split at the moment when the peak value was determined during the moving into phase. Thus the initiation of the rest phase on the curve was not coinciding with the moment the subject reached at the rest position. This was necessary in order not for the mean kinematic curve to become too dull in shape. Same was true when the end of rest phase was determined. The maximum hip and knee joint angles during the cycle were determined. Further a relationship between the hip and knee joint excursions were investigated. The results indicated condition 8) requires the maximum flexion angles to the hip among all conditions, 157.5 ± 20.4° and condition 3) to the knee joint, 157.1 ± 10.0° respectively (Fig 2). The results also indicated in many activities, the maximum joint angles were recorded not during the rest phase but during the moving into or out of phase. In any conditions even including donning on and off a sock, a strong relationship was found between the hip and knee joints motion (Fig 3), indicating the bi-articular muscles' co-contraction during the sit to stand activities. The data presented in this study will increase the knowledge of high-flexion needs especially in non-Western cultures and provide an initial characterization of the prosthesis kinematics in high flexion.


Shunji Hirokawa Kazuo Kiguchi Michihiko Fukunaga Teruo Murakami

There are several concerns about the current simulators for TKA. First, the knee is flexed in a “passive way” under the condition of applying constant muscular tension forces. Second, the effects of hip joint motion are not taken into account. Thirdly, the external load for example, upper body weight is not applied in a natural way. Finally, few simulators are capable of knee flexion greater than about 100°.

To this end, we have developed a novel knee simulator system that reproduces the active and natural knee motion to evaluate kinematics and joint forces of TKA. Our simulator system has the following advantages and innovative features. First, it is driven directly by muscles' tension forces, and the knee is capable of active flexion. Secondly, a hip joint is incorporated into it and the lower limb motion is achieved in a synergistic way between the hip and knee joints. Thirdly, it is capable of complete deep knee flexion up to 180°.

Figure 1 shows the structure of the system. Both the hip and knee joints are moved by the tension forces of four wires that simulate the functions of the mono-articular muscles ((1), (3)) and the bi-articular muscles ((2), (4)) by means of a multiple pulley system (Fig 2). The femoral and tibial components of TKA are secured in the distal end of the upper link (thigh) and the proximal end of the lower link (shank) respectively. The ankle assembly has three sets of rotary bearings whose axes intersect at a fixed point, the center of the ankle, allowing spherical movement of the tibia about the ankle center. Springs were stretched around the ankle center to substitute the muscles around the ankle. Weights I and II are counterweights so as to duplicate the weights of the human upper body, thigh and shank respectively. The wires are pulled to produce the hip and knee motions. The linear bearings running along vertical rods also prevent the system from collapsing.

In the experiment, a custom-designed posterior stabilized type TKA was attached to the simulator system for evaluation. The system was operated so as to reproduce the sit-to-stand features in a quasi-static manner in order to study the kinematics of TKA. Beyond 130°, the knee proceeded to flex passively because of upper body weight. Conspicuous internal/external rotation or valgus/varus motion of the tibia relative to the femur was not observed as the knee flexed. When our simulator system was driven in a quasi-static manner, it was able to measure the kinematics of TKA however, when the system was driven in a dynamic manner, it oscillated because the springs around the ankle were not stiff enough to hold the inverted pendulum-like system upright and the ratios of the tension force exerted by the four wires simulating muscles could not be determined appropriately.


William Hodge Melinda Harman Scott Banks

A unique, laterally stabilized design concept (3D Knee-DJO Surgical, Inc) for total knee arthroplasty (TKA) without traditional post and cam construct was developed to allow surgeons to resurface the arthritic knee while choosing to maintain or sacrifice the posterior cruciate ligament (PCL). Reported complications with current ‘post and cam’ designs of PCL-substituting TKRs include higher polyethylene wear associated with cam-post impingement, increased bone interface shear stresses, and more distal femoral bone resection making revisions more complex and problematic. The effectiveness of this laterally stabilized TKA design has been extensively studied biomechanically using both in-vitro and in-vivo methods. It was hypothesized that for this total knee arthroplasty design; the mid-term clinical, radiographic and functional results would be the same for patients having two different surgical techniques in which the posterior cruciate ligament was either completely retained or completely resected. This study reports on eight year clinical results as well as in-vivo fluoroscopic results and retrieval data. Reported are 159 patients with 116 knees done by a surgeon who preserved the PCL with a bone block technique and 43 knees by a second surgeon who completely resected the PCL. Clinical results did not statistically differ between the two groups and found Knee Society Scores of 96 for Pain and 91 for Function. Average ROM was measured at 124 degrees. Comparative fluoroscopic imaging analysis of in-vivo dynamic flexion activities of thirty-three (20 PCL-preserved and 13 PCL resected) knees was performed demonstrating stable performance and only small (non-significant) mechanical differences. Analysis of two unrelated groups of tibial polyethylene inserts, the first retrieved from patients after 1–4 years in-vivo function (n = 14) and the second after in-vitro knee wear simulation (n = 4) showed low wear rates with no delamination. There was only one failure for mechanical loosening in the cruciate resected group and radiolucent lines of greater than 2 mm were only seen in 4% with none being progressive. Kaplan-Meier Survivorship, using mechanical loosening as the end point, was 99.2% at an average of 8.8 years. In summary, this laterally stabilized TKR design offers a very good alternative to standard ‘post and cam’ PCL sacrificing TKRs while still giving surgeons the ability to maintain the PCL if desired.


Harry Hothi Reshid Berber Robert Whittaker John A. Skinner Alister Hart

Metal-on-metal (MOM) total hip arthroplasty and hip resurfacing using large diameter femoral heads offer clinical advantages, however the failure rates of these hips are unacceptably high. Retrieved MOM hips have a wide range of wear rates of their bearing surfaces and there is ongoing research to identify the causes of failure.

Detailed visual inspection is the first step in the forensic examination of failed hip components, but there is no universally accepted description or process. Visible features may help explain the mechanism of failure of MOM hips.

During our analysis of 2000 MOM hip components, we have developed protocols to undertake detailed, non-destructive macroscopic and stereomicroscopic examinations of each component, using quantitative assessment to document the presence of types of damage.

We have established a systematic terminology to describe the types of damage that are observed, allowing for consistency and clarity in the vocabulary used. These include (but are not limited to):

Scratching – when there is an increase in the number and/or magnitude of scratches present on the surface, typically increasing measured roughness parameters. The severity of scratching is determined by rubbing a 0.18 mm thickness acetate gage or fingernail over the surface:

Light –visible but not detectable with gage.

Moderate – visible and detectable with gage.

Heavy – depth clearly visible and will catch a fingernail or gage.

Pitting – indentations in the surface for which the dimensions are similar in all directions.

Embedded Particles – hard particles that have become embedded in the bearing surface.

Discolouration – observed as a change in the appearance of the surface, often as colour diffraction patterns.

Polishing, gouges, etching (from corrosion), surface films, surface deposits and tribochemical reaction layers.

To assess the distribution of these types of damage on the components, each surface is considered in terms of zones defined by quadrants (cup, head, stem and taper) and sub-quadrants (cup and head only), Figure 1. Each zone is scored on a scale of 0 to 3 by determining the percentage of the surface area of the quadrant that exhibits the feature in question:

a score of 0 indicates 0%

indicates greater than 0% but less than 25%

indicates between 25% and 75% inclusive

indicates greater than 75%.

The use of zones to differentiate between the polar and equatorial regions of the cup and head surfaces can offer important information relating to the articulation of the bearing surfaces. For example in a cohort of 90 inspections, a score of 3 for light scratching was recorded in all areas of the bearing surface in 40% of cups, whilst approximately 5% had evidence of pitting, occurring near the rim.

Current research at our retrieval centre involves correlating the results of detailed inspections with a range of variables, including implant design, size and surgical position.


Norishige Iizawa Atsushi Mori Syuhei Matsui Ryosuke Oba Toshihiko Ito Shinro Takai

Purpose:

Biomechanical knowledge of the medial collateral ligament (MCL) is important for MCL release during knee arthroplasty. The purpose of this study was to define the influences of the deep medial collateral ligament (dMCL) and the posterior oblique ligament (POL) on valgus and rotatory stability in knee arthroplasty.

Methods:

Six cadaveric knees were divided into 2 groups with unique sequential sectioning sequences of the dMCL and the POL. Group A (n = 2) first received femoral arthroplasty only, and thereafter sequentially received medial half tibial resection with spacer, ACL cut, dMCL cut, POL cut, and finally tibial arthroplasty. Group B (n = 4) first received femoral arthroplasty only, and thereafter sequentially received medial half tibial resection with spacer, ACL cut, tibial arthroplasty, dMCL cut, and finally, POL cut. A CT-free navigation system monitored motion after application of valgus loads (10 N-m) and internal and external rotation torques (5 N-m) at 0°, 20°, 30°, 60°, and 90°of knee flexion.


Masami Ishimaru Yoshitaka Shiraishi Kazunori Hino Yoshio Onishi Hiromasa Miura

Introduction:

The widespread use of TKA promoted studies on kinematics after TKA, particularly of the femorotibial joint. Knee joint kinematics after TKA, including the range of motion (ROM) and the physical performance, are also influenced by the biomechanical properties of the patella. Surgeons sometimes report complications after TKA involvinganterior knee pain, patellofemoral impingement and instability. However, only few studies have focused specially on the patella. Because the patella bone is small and overlapped with the femoral component on scan images. In addition, the patellar component in TKA is made of x-ray–permeable ultra-high molecular weight polyethylene. It is impossible to radiographically determine the external contour of the patellar component precisely. No methods have been established to date to track the dynamic in vivo trajectory of the patella component. In this study, we analyzed the in vivo three-dimensional kinematics of the patellar component in TKA by applying our image matching method with image correlations.

Methods:

A computed tomography (CT) and an x-ray flat panel detector system (FPD) were used. FPD-derived post-TKA x-ray images of the residual patellar bone were matched by computer simulation with the virtual simulation images created using pre-TKA CT data. For the anatomic location of the patellar component, the positions of the holes drilled for the patellar component pegs were used. This study included three patients with a mean age of 68 years (three females with right knee replacement) who had undergone TKA with the Quest Knee System and achieved a mean passive ROM of 0 to ≥ 130° after 6 or more month post-TKA. We investigated three-dimensional movements of the patellar component in six degrees of freedom (6 DOF) during squatting and kneeling. Furthermore, we simulated the three-dimensional movement of the patellar component, and we estimated and visualized the contact points between the patellar and femoral components on a three-dimensional model.


Gerald Jerry Jon Dounchis

Introduction

Accurate alignment of components in total knee arthroplasty (TKA) is a known factor that contributes to improvement of post-operative kinematics and survivorship of the prosthetic joint. Recently, CAOS has been introduced into TKA in effort to reduce positioning variability that may deviate from the mechanical axis. However, literature suggests that clinical outcomes following TKA with CAOS may not present a significant improvement from traditional methods of implantation. This would infer that achieving correct alignment, alone, might be insufficient for ensuring an optimal reconstruction of the joint. Therefore, this study seeks to evaluate the importance of soft-tissue balancing, through the quantification of joint kinetics collected with intraoperative sensors, with or without the combined use of CAOS.

Methods

Seven centers have contributed 215 patients who have undergone primary TKA with the use of intraoperative sensors. Of the 7 surgeons contributing patients to this study, 3 utilize CAOS; 4 utilize manual techniques. Along with standard demographic and surgical data being collected as per the multicenter study protocol, soft-tissue release techniques and medial-lateral intercompartmental loads—as indicated by the intraoperative sensors—were also captured pre- and post-release. “Optimal” balance was defined as a medial-lateral load difference of ≤ 15 lbs. A chi-squared analysis was performed to determine if the percentage of soft-tissue release was significantly different between the two groups: patients with CAOS, and patients without CAOS.


Thomas John Gaurav Shah Matin Lendhey Amar Ranawat Chitranjan S Ranawat

Introduction

Total hip arthroplasty (THR) is one of the most successful procedures performed today. Uncemented acetabular components have by and large replaced cemented cups. As such, optimal fixation, bony ingrowth with longevity, and safety is highly demanded. In this study, we look at the safety and efficacy of the Stryker® Trident PSL™ acetabular component based on radiographic and clinical analysis.

Materials and Methods

We looked at 860 consecutive patients between 2003 and 2007. Of these, 231 consecutive patients had a minimum 5 year follow up. All cases were for degenerative joint disease (DJD), except 2 for dysplasia, 1 for avascular necrosis (AVN), 1 femoral neck nonunion. Average Hospital for Special Surgery (HSS) hip scores at final follow up were recorded. Radiographic analysis included classification based on Delee and Charnley's zones 1–3. Osseointegration was assessed based on presence of SIRCAB (stress induced reactive cortical hypertrophy of bone), demarcation around the implant, stress shielding, presence of radial trabeculae, absence of radiolucency, type of bearing, presence of preoperative protrusion, violation of Kohler's line. EBRA software was used to assess acetabular inclination and version.


Kurato Jonishi Ryutaku Kaneyama Hideaki Shiratsuchi Kazuhiro Oinuma Yoko Miura Hidetaka Higashi Tatsuya Tamaki

Introduction

In posterior cruciate ligament (PCL)-preserving total knee arthroplasty (TKA), it is important to determine whether the PCL is properly functioning after surgery. As the PCL is partly damaged during the operation, we cannot rule out the possibility that excessive tension further damages the remaining PCL resulting in dysfunction or that initial functioning of the PCL is lost due to excessively low tension. However, it is normally difficult to examine whether the PCL has remained intact and is still functional after TKA. The objective of this study was to visualize knee joint flexion after TKA by MRI and evaluate the PCL based on these images.

Method

PCL-preserving TKA was performed in 41 knees using the Fine Total Knee System® (Nakashima Medical, Okayama, Japan) where a titanium component can be selected for both the femur and the tibia. We visualized knee flexion positions by MRI at 6 months after surgery and evaluated visualization or non-visualization of the PCL, the relationship between knee flexion angle and PCL elevation angle against the plane of the tibial joint vertical to the tibial axis, and the forms of PCL based on the MRI data.


Kwang Am Jung Alvin C Ong Kwang Am Jung Byoung Yoon Hwang Hye Sun Ahn

Introduction:

Sleep disturbance is the one of major complaints associated with knee osteoarthritis, and sleep status is one factor that influences quality of life. The present study was designed to assess sleep status in patients undergoing total knee arthroplasty and to identify factors affecting sleep patterns.

Methods:

We performed a prospective study of 112 patients undergoing total knee arthroplasty from June 2011 to February 2012. Data including demographic characteristics (age, gender, BMI, VAS pain scale score, SF 36, level of education, and psychologic comorbidities) and sleep profiles (Nottingham Health Profile – 0 to 100, with 0 indicating good sleep status; Sleep Satisfaction Scale – 0 to 10, with 10 indicating full satisfaction) was collected before and after (six days, two weeks, three months, and six months) total knee arthroplasty.


Kwang Am Jung Alvin C Ong Kwang Am Jung Jong Won Kim Ha Young Park

Background:

Periprosthetic joint infection (PJI) is one of the most devastating complications in patients undergoing total knee arthroplasty (TKA). Although controversy exists about the necessity of the prophylactic use of antibiotics in clean operations, the routine use of antibiotic-loaded bone cement (ALBC) has been the clinical procedure against PJI for many decades. Additionally, the combination of antibiotics has been used to broaden the antimicrobial spectrum and to enhance antimicrobial activity in a revision setting with a potentially resistant organism. Even in primary TKA, the prophylactic combination of antibiotics used as therapy should be considered on patients with a higher susceptibility to bacterial infection based on their clinical histories of PJI, rather than the lower risk population. The purpose of this study is to investigate whether the synergistic combination of antibiotics in bone cement in high risk patients can reduce PJI.

Methods:

A total of 3015 knees of 1918 patients were screened for inclusion in this study based on their risk factor, and those categorized as systematically or locally high risk patients were included. Patients that were classified as “systemically high risk” received an American Society of Anesthesiologists (ASA) classification of 3 or higher and a Charlson Comorbidity Index (CCI) classification of 2 or higher (n = 212 knees, 70.7% of 300 total). Patients that were classified as “locally high risk” had a history of inflammatory arthritis, poor skin conditions, and/or recent septic knee arthritis (n = 76 knees, 25.3%). Patients with both systemically and locally high risk included 12 knees (4.0%). The 300 knees included in this study were separated into three groups based on the combination of antibiotics administered. In group 1(208 knees), gentamycin–impregnated cement was used and in group 2(48 knees) hand-mixed vancomycin with pre-mixed gentamycin cement for intraoperative management was used. In group 3 revision bone cement containing a combination of two antibiotics (gentamycin and clindamycin) was used (44 knees). The mean age was 70.9 years. The number of men and women were 31(10.3%) and 269(89.7%), respectively. The average body mass index (BMI) was 26.7 kg/m2. The incidence of PJI was investigated.


Kwang Am Jung Alvin C Ong Il Ho Park Kwang Am Jung

Introduction:

Unicompartmental knee arthroplasty (UKA) is becoming an increasingly popular option in single compartment osteoarthritis. As a result, diverse second operations including revisions to total knee arthroplasty (TKA) will also increase. The objective of this study is to investigate the distribution of causes of second operations after UKA.

Methods:

We retrospectively reviewed 695 UKAs performed on 597 patients between January 2003 and December 2011. Except in one case, all UKAs were replaced at the medial compartment of the knee. The UKAs were performed on 559 (80.4%) women's knees and 136 (19.6%) men's knees. The mean age at the time of UKA was 61.5 years. The mobile-bearing designs were those that were predominantly implanted (n = 628 mobile, 90.2%; n = 67 fixed). The mean interval between UKA and second operation was 14.1 months.


Kwang Am Jung Jong Won Kim Kwang Am Jung Byung Ho Lee Ha Young Park Alvin C Ong

Introduction:

Recently, patient expectations regarding the outcomes of total knee arthroplasty (TKA) have increase due to advances in knee implant design, surgical techniques, and procedure safety. However, outcomes do not always meet preoperative expectations. The purpose of this study is to investigate what Korean patients expect from their TKA and relationship between Pre-TKA expectation and demographic factors.

Methods:

We performed a prospective study of 228 patients undergoing primary TKA from April 2013 to May 2013. The number of men and women were 211 (92.5%) and 17 (7.5%) respectively, and mean age was 70.9. We used 19-item clinical knee assessment questionnaire including “crossed leg” item for unique sedentary culture in eastern countries. Each item was evaluated on a Likert scale from 0 to 4 (0: not relevant, 1: relevant, 2: little important, 3: somewhat important, 4: very important). We also used another questionnaire regarding to patient's demographics. Score of all expectation was calculated by sum of all item score.


Mateusz Juszczyk Martin Hintner Christian Kaddick Alfons Kelnberger Wecker Heinrich

Introduction:

Failure of the polyethylene glenoid component is the most common complication of Total Shoulder Arthroplasty (TSA) and accounts for a majority of the unsatisfactory results after this procedure. Nowadays, most of the shoulder prostheses consist of metal on polyethylene bearing components. Repetitive contact between the metal ball and the polyethylene socket produces progressive abrasion of the implant if the moving part is made of polyethylene. Its debris may then lead to an active osteolysis and implant loosening. Failure of the glenoid component is often manifested clinically by pain, loss of function, and the presence of a clunking noise and leads to revision surgery.

The use of ceramic balls aims at the reduction of this phenomenon. In many studies regarding knee and hip replacement it has been shown that the use of ceramic on polyethylene is more beneficial in terms of polyethylene wear and failure, when compared to metal on polyethylene. This is to our knowledge the first study to address in direct comparison wear in both TSA and RTSA.

Materials and methods:

Two different wear tests were conducted in order to address both TSA and RTSA kinematics.

Since up to day, there is no test standard for wear testing neither for TSA nor for RTSA a customised joint simulators were used to create worst-case scenarios motions in both cases.

In the TSA testing setup, the orientation of the glenoid component and humeral component was chosen according to M. A. Wirth (2009) study but with the humeral component assembled inferiorly. For the RTSA the applied kinematics was based on a study of G. Kohut (2012) and ISO 14242-1 (2012) standard.

Three articulating couples for each material were tested for both TSA and RTSA for total of 5 million cycles. Standard midterm gravimetric measurements were conducted at each 1 million cycles.


Rami Kallala Ikram Nizam Fares Haddad

Introduction:

Periprosthetic joint infection (PJI) is a devastating diagnosis that carries a significant rate of associated mortality and places a large burden on health care systems. Treatment protocols often include combined intravenous antibiotics and staged revision surgery with locally-delivered antibiotics via PMMA cement spacers and/or beads. One disadvantage of PMMA is the need for later removal. Antibiotic releasing Calcium Sulphate beads (CaSO4) have had promising results in revision joint surgery and are absorbable, making later removal unnecessary. We report on use in a tertiary referral centre in the UK and present our initial findings.

Methods & Results:

CaSO4 beads containing 1 gram of Vancomycin and 240 mg of tobramycin per 10 cc was implanted in 12 patients between August 2012 and December 2012, all having undergone revision joint surgery for PJI. Of these patients; 7 were men and 5 women, mean age was 57 years (range 39–72) with a mean ASA grade of 2 (1–4). Indications were infected Total Hip Replacement (n = 7), infected Total Knee Replacement (n = 4) and infected metal on metal hip resurfacing (n = 1). Three procedures were emergencies, with the remainder being semi-elective procedures. One patient had single-stage revision THR. At latest follow up 10 patients had made a full recovery, with normal function and inflammatory markers. Two patients were awaiting a second stage revision procedure. Mean follow up was 2 months (1–4).


Hirnori Kaneko Yutaka Hoshino Yoshihiko Saito Takashi Tsuji Yasunori Tsukimura Hitoshi Abe Kazuhiro Chiba

Introduction:

Since2007, we have used CT-based fluoroscopy-matching navigation system (Vector Vision Hip Ver.3.5.2, BrainLAB, Germany) in revision total hip arthroplasty. This system completes the registration procedure semi-automatically by matching the contours of fluoroscopic images and touching 3 adequate points to the contours of 3D bone model created in the computer. Registration procedure using fluoroscopic figures has finished before making surgical incision. It needs no elongation time during the operation. The objective of this study was to evaluate the accuracy of CT-based fluoroscopy-matching navigation system in revision THA.

Material and method:

We analysed the acetabular cup in consecutive 33 hips with both intra-operative and post-operative alignment data (based on navigation system and CT evaluation) We further compared these measurements with results from primary THA. Data for primary THA were therefore obtained from 40 consecutive patients who underwent primary THA between August 2007 and May 2013 using the same navigation system by postero-lateral approach. We aimed the cup angle for Revision THA as following, the inclination: 40 degrees, the anteversion: 20 degrees Anteversion on the navigation system must be adjusted by the pelvic tilt.


Ryutaku Kaneyama Ryuji Nagamine Chen Weijia Hideaki Shiratsuchi

Objective:

Accurate measurement of the extension and flexion gap is important in total knee arthroplasty (TKA). Particularly, the flexion gap may be influenced by several factors; therefore, tension of the posterior cruciate ligament (PCL), knee extensor mechanism, and the thigh weight may need to be considered while estimating the flexion gap. However, there is no comprehensive study on the flexion gap, including an assessment of the influence of gravity on the gap. The purpose of this study is to investigate the influence of PCL, knee extensor mechanism, and thigh weight on the flexion gap by using a fresh frozen cadaver.

Methods:

A fresh frozen lower limb that included the pelvis was used for the assessments. The knee was resected by a measured resection technique and a femoral component was implanted to estimate the component gap. The knee was flexed by precisely 90 degrees using a computer navigation system. The flexion gap was measured in different situations: group A, PCL preserved and patella reduced; group B, PCL preserved and patella everted; group C, PCL resected and patella reduced; and group D, PCL resected and patella everted. In each group, the measurements were obtained under 3 different conditions: 1, knee flexed and the lower limb on the operation table under gravity, as is usually done in TKA; 2, hip and knee flexed 90 degrees to avoid the influence of gravity; and 3, knee set in the same position as in condition 1 and the thigh was held by hand to reduce the influence of the thigh weight.


Makoto Kawasaki Ryuji Nagamine Keiichi Kondo Chen Weijia Kei Osano

Introduction

Following total knee arthroplasty (TKA), some patients show patella baja. It is possible that patella baja after posterior stabilized (PS)-type TKA causes the patellar clunk syndrome and limitation of flexion. The purpose of this study was to examine patellar height before and after PS-type TKA and identify the factors related to the change in patellar height.

Methods

Lateral X-ray films were taken at 90 degrees flexion before and after TKA using fluoroscopy in 87 patients (95 knees) (Fig. 1a, b). The components and surgical technique for TKA were Scorpio NRG (Stryker) and the modified gap control technique, respectively. The Insall-Salvati ratio (ISR) and the Labelle-Laurin method (LL) were measured as parameters of patellar height (Fig. 1c, d). Posterior condylar offset (PCO) (Fig. 1e), the distance from the anterior femoral line to the tibial tuberosity (TA), and the distance from the tibial tuberosity to the posterior condyle of the femur [TP; {TA-F (the length of the femoral condyle)}] (Fig. 1f) were examined as parameters that could be associated with the change in patellar height. All parameters were divided by patellar length to compensate for the expansion rate in each photograph. The mean LL/P, PCO/P, TA/P, and TP/P before TKA were set at 100%.


Seyyed Morteza Kazemi Mahdi Bahari Mehrabani Seyyed Mohammad Qoreishi Farshad Safdari

Background:

It has been suggested that double-level osteotomy can prevent the occurrence of joint line obliquity (JLO), as one of the complications following high tibial osteotomy (HTO). In this study, we aimed to compare the preoperative distal femoral and proximal tibial obliquity in patients with primary genu varum with a group of normal subjects (without genu varum).

Materials and methods:

75 patients with primary genu varum and 75 normal persons, contributed to a case-control study. The medial distal femoral mechanical angle (MDFMA), medial proximal tibial mechanical angle (MPTMA), joint diversion angle (JDA) and femoral and tibial JLO were measured and compared between the two groups. The percentage of patients' with > 4 degrees of JLO in both distal of femur and proximal of tibia, were then determined.


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John Keggi Timothy McTighe Matthew Ariyavatkul Arthur Landry

Wear debris associated with CoCr bearings has been implicated in the development of adverse soft tissue reactions and pseudotumors following THA with large metal heads and following hip resurfacing. Additional concerns have been raised regarding trunion fretting and corrosion. Most recently, the neck-stem junction of some modular femoral stem designs have come under additional scrutiny. We undertook a review of patients who had undergone THA with a proximal modular junction stem design in order to ascertain the state of the junction in early follow up.

We examined the records of all patients in our practice who had undergone uncomplicated, unilateral THA with the ARC stem (OmniLife Science, East Taunton, MA, USA) between April 2010 and April 2012. Office records, radiographs and laboratory data were included. Serum or blood cobalt and chromium ion levels were obtained at the one-year post-op visit or later or if the patient had unexpected pain. The test obtained (serum or blood) was dependent on the lab performing the study.

In the study period 100 patients met the inclusion criteria and had metal ion levels available for review. No patient required revision for adverse soft tissue reaction or elevated metal ion levels. Cobalt levels fell with the normal lab ranges in the majority of patients with a very small percentage demonstrating levels slightly above the normal range. Chromium levels all fell within the expected normal range. One patient had a neck exchange for mechanical reasons at 8 weeks following primary THA. This patient went on to develop elevated serum cobalt levels and a large hip effusion. The hip was revised at one year to a non-modular stem.

A modular proximal stem offers the advantages of addressing variable anatomy and allowing less soft tissue dissection. Some designs have enjoyed success while others have been withdrawn from the market due to fatigue failure, dissociation or metal-associated adverse reactions. Modular junction designs vary greatly which can impact their inherent stability and their ability to resist micro-motion. In this patient group the junction has shown good stability in early follow up as judged by clinical and laboratory data. Cobalt levels were all normal or well below the range considered suspicious for adverse reaction. Chromium levels all fell within the normal range. A case of an exchanged neck with retention of the stem was associated with high cobalt levels. We discuss several junction designs and their characteristics.


Oliver Kessler

INTRODUCTION:

To avoid the early onset of osteoarthritis after partial meniscectomy an effective replacement of injured meniscal tissue would be desirable. The present study investigates the behaviour of a new silk derived scaffold supplied by Orthox Ltd. (Abingdon, UK) in an in vivo sheep model.

METHODS:

The scaffolds where derived from silk fibres by processing into an open porous matrix. Nine sheep (4 ± 1 years) underwent partial meniscectomy at the anterior horn of the medial meniscus followed by implantation of a scaffold. The unoperated contralateral stifle joint served as control.

After six months the animals were sacrificed and the joints inspected for inflammation. The Young's modulus of the tibial cartilage, meniscus and scaffold was determined by indentation or confined compression tests. All tissues were fixed in formaldehyde for histology. The data were analysed by a Wilcoxon and Mann-Whitney-U-test.


Samantha Wright Tim A.E.J. Boymans Tony Miles Bernd Grimm Oliver Kessler

Introduction

The human body is a complex and continually adapting organism. It is theorised that the morphology of the proximal femur is closely related to that of the distal femur. Patients that have abnormal anatomy in the proximal femur, such as a high femoral neck anteversion angle, may have abnormal anatomy in the distal femur to overcome proximal differences. This phenomenon is of key interest when performing Total Hip Replacement (THR) or Total Knee Replacement (TKR) surgery. The current design and placement of existing hip and knee implants does not account for any correlation between the anatomical parameters of the proximal and distal femur, where bone anatomy may have adapted to compromise for abnormalities.

A preliminary study of 21 patients has been carried out to assess the relationship between the proximal and distal femur. The difficulties in defining and measuring key anatomical parameters on the femur have been widely discussed in the literature [1] due to its complex three dimensional geometry. Using CT scans of healthy octogenarians, it was possible to mark key anatomical landmarks which could be used to define various anatomical axes throughout the femur. Correlation analyses could then be carried out on these parameters to assess the relationship between proximal and distal femur morphology.

Methods

Each femur was initially realigned along the mechanical axis (MA); defined by joining the centre of the femoral head (FHC) to the centre of the intercondylar notch (INC) [2]. All anatomical landmarks were then identified using the Materialise Mimics v12 software (Figure 1 and 2) and exported into Microsoft Excel for analysis. Key anatomical parameters which were derived from these landmarks included the femoral neck axis (FNA), femoral neck anteversion angle (FNAA) [1–4], condylar twist angle, clinical transepicondylar axis (TEA), trochlea sulcus angle and medial and lateral trochlea twist.

A correlation analysis was carried out on SPSS Statistics v20 (IBM) to assess the relationship between proximal and distal anatomical parameters.


Denis Nam Saker Khamaisy Hendrik Zuiderbaan Andrew Pearle

Introduction:

The number of medial unicompartmental knee arthroplasties (UKA) performed over the last decade has increased by 30%, as studies have demonstrated improved knee kinematics, range of motion, and decreased perioperative morbidity versus total knee arthroplasty. However, concerns remain regarding the future risk of revision due to lateral compartment degeneration. In patients with a varus mechanical alignment and tibiofemoral subluxation secondary to medial compartment osteoarthritis, the femoral and tibial articular surfaces of the lateral compartment subsequently become incongruous, potentially increasing the focal contact stresses seen with loading. The purpose of this study is to evaluate whether the tibiofemoral congruence of the lateral compartment of the knee is improved following a medial UKA.

Methods:

This study is a retrospective review of 192 consecutive medial UKAs included in an IRB-approved, single-surgeon database. All UKAs were performed using a robot-assisted surgical technique. Preoperative and postoperative standing, anteroposterior hip-to-ankle radiographs controlling for lower extremity rotation were performed from which the congruence of the lateral compartment was measured.

The preoperative and postoperative degree of articular congruence (congruence index, CI) was calculated using an iterative closest point (ICP)-based software code (Matlab, MathWorks Inc., Natick, MA), specially developed to evaluate congruence of knee compartments. Following digitization of the articular surfaces of the femur and tibia, the code performs a rigid transformation that best aligns the articular surfaces and evaluates the current degree of articular congruence. A congruence index (CI) is then calculated, with a value of 1 indicating complete congruence, and a value of 0 indicating a 100% dislocation of the articular surfaces.

A student's t-test was used to compare the preoperative and postoperative values of lateral compartment congruence.


In Soo Song Tae In Kim

Background:

To evaluate causes and results of revision arthroplasties in unstable total knee arthroplasties

Methods:

We retrospectively reviewed 24 knees that underwent revision arthroplasty for unstable total knee arthroplasty from December 2004 to December 2010. The mean age was 71.0(range, 54–85) years and the average follow-up period was 33.8 months (range, 6–70). The mean interval between the primary TKA and revision TKA was 82.5 months (range, 14–228). We classified the instability and analyzed the treatment according to its cases. Stress radiographs, postoperative component position and joint level were measured. Joint line position was measured using the fibular head as the reference point. Clinical outcomes were assessed using the Hospital for Special Surgery (HSS) score and range of motion. Wilcoxon sign rank test was employed for statistical analysis, and when p-value was over 0.05, it was analyzed as having statistical significances.


In Soo Song Tae In Kim

Purpose:

We compared patients, (group A) who had severe varus deformity with posterolateral varus thrust, with patients,(group B) who didn't have varus thrust for results of total knee arthroplasty.

Materials and Methods:

The average follow-up period was 33 months in group A (25 cases out of 23 patients) and 67 months in group B (50 cases out of 50 patients). We evaluated which kind of implant the patient had, the thickness of the polyethylene and changes of joint levels. Also we measured preoperative and postoperative mechanical axis deviation, tibio-femoral angle, and implant positions. Clinical results included preoperative and postoperative HSS, KSS, range of motion, and remained posterolateral instability on final follow-ups (Fig 1, Fig 2).


Hasung Kim Kyung-Soon Park Jae-Wook Byun Taek Rim Yoon

Purpose:

The purpose of this study was to evaluate the results of two stage reconstruction for infected arthroplasty of hip joint and to know the risk factor for failures.

Patients and Methods:

From May 2004 to September 2011, 104 consecutive patients (105 hips) who underwent two stage reconstruction for the infected arthroplasty of hip joint were retrospectively evaluated. There were 60 hips with primary THA infection (Acute infection 22, Delayed infection 38), 4 hips with revision THA infection (Acute infection 1, Delayed infection 3), 20 hips with primary hemiarthroplasty infection (Acute infection 14, Delayed infection 6) and 24 hips with acute pyogenic coxitis. We evaluated the number of surgeries before two-stage reconstruction and also analysed the cultured pathogens. Mean follow duration after 2nd stage revision THA was 1.80 ± 1.76 years and average age at the time of 1st stage surgery (Debridement and PROSTALAC insertion) was 62.8 ± 14.3 years.


Jay King Aimee Struk Kevin Farmrer Thomas Wright

Purpose:

While the use of press-fit humeral components has been accepted in total shoulder arthroplasty, few studies focus on the outcomes after uncemented reverse total shoulder arthroplasty. The purpose of this study is to compare the radiographic and functional results of uncemented and cemented humeral fixation in reverse total shoulder arthroplasty.

Materials/Methods:

A retrospective review was performed identifying all patients that underwent reverse total shoulder arthroplasty (RTSA) between May 2007 and December 2010. Medical records and a prospective research database were reviewed for demographic, operative, and clinical information. Inclusion criteria were a primary reverse total shoulder arthroplasty from one manufacturer with a grit-blasted humeral metaphyseal stem and minimum follow-up of 2 years. Exclusion criteria included shoulder arthroplasty for fractures, fracture sequelae, or inflammatory arthropathy. Antibiotics were not routinely added to the cement. The radiographic and functional outcomes were compared between the uncemented and cemented groups. Statistical analysis was performed using the Fisher Exact test to compare the dichotomous variables between the groups. The functional outcome data between the groups was calculated using the two-tailed Wilcoxon Rank Sum test.


Kyung Rae Ko Keun Ho Lee Sang-Min Kim Seung-Jae Lim Young-Wan Moon

Introduction:

The robot-assisted cementless total hip arthroplasty has theoretical advantages of providing better fit and mechanical stability of the stem. However, no previous study has been reported on a short stem implantation using surgical robot. We compared early clinical and radiographic results between robotic milling and manual rasping in short stem total hip arthroplasty.

Materials & Methods:

We designed a prospective randomized controlled trial to determine whether robot-assisted short stem total hip arthroplasty improves the implant position represented by stem alignment, leg length equality, and reduces the intraoperative and early postoperative complications. A total of 40 patients were enrolled with informed consents and randomly assigned to robotic milling group (20 hips) and manual rasping group (20 hips) by means of a computer-generated random number table. There were no statistically significant differences in the demographics of the patients between the two groups


Laryssa Korduba-Rodriguez Chau Ngo Aaron Essner

INTRODUCTION

Many studies have looked at the effect of titanium versus cobalt chrome baseplates on backside wear. However, the surface finish of the materials is usually different [1,2]. There may also be subtle locking mechanism design changes [2]. The purpose of this study was to evaluate the wear performance of polyethylene inserts when mated with titanium baseplates to cobalt chrome baseplates, where both have non-polished topside surfaces and an identical locking mechanism.

MATERIALS AND METHODS:

A total of three trays per material were used. The titanium trays are intended for cementless application and include a porous titanium surface on the underside, while the cobalt chrome trays are intended for cemented applications. All trays were Triathlon design (Stryker Orthopaedics, Mahwah, NJ). Tibial inserts were manufactured from GUR 1020 polyethylene then vacuum/flush packaged and sterilized in nitrogen (30 kGy). Cobalt chrome femoral components were articulated against the tibial inserts.

Surface roughness of the baseplates was measured prior to testing using white light interferometry (Zygo, Middlefield, CT). A 6-station knee simulator (MTS, Eden Prairie, MN) was used for testing. A normal walking profile was applied [3]. Testing was conducted for 1 million cycles. A lubricant of Alpha Calf Fraction serum (Hyclone Labs, Logan, UT) diluted to 50% with a pH-balanced 20-mMole solution of deionized water and EDTA was used [4]. The serum solution was replaced and inserts were weighed for wear every 0.5 million cycles. Standard test protocols were used for cleaning, weighing, and assessing the wear loss [5]. Soak control specimens were used to correct for fluid absorption. Statistical analysis was performed using the Student's t-test (p < 0.05).


J. Philippe Kretzer Joern Reinders Robert Sonntag Christian Merle Georg Omlor Marcus Streit Tobias Gotterbarm Peter Aldinger

Corrosion in modular taper connections of total joint replacement has become a hot topic in the orthopaedic community and failures of modular systems have been reported. The objective of the present study was to determine in vivo titanium ion levels following cementless total hip arthroplasty (THA) using a modular neck system.

A consecutive series of 173 patients who underwent cementless modular neck THA and a ceramic on polyethylene bearing was evaluated retrospectively. According to a standardized protocol, titanium ion measurements were performed on 67 patients using high-resolution inductively coupled plasma-mass spectrometry. Ion levels were compared to a control group comprising patients with non-modular titanium implants and to individuals without implants.

Although there was a higher range, modular-neck THA (unilateral THA: 3.0 μg/L (0.8–21.0); bilateral THA: 6.0 μg/L (2.0–20.0)) did not result in significant elevated titanium ion levels compared to non-modular THA (unilateral THA: 2.7 μg/L (1.1–7.0), p = 0.821; bilateral THA: 6.2 μg/L, (2.3–8.0), p = 0.638). In the modular-neck THA group, patients with bilateral implants had significantly higher titanium ion levels than patients with an unilateral implant (p < 0.001). Compared to healthy controls (0.9 μg/L (0.1–4.5)), both modular THA (unilateral: p = 0.029; bilateral p = 0.003) and non-modular THA (unilateral: p < 0.001; bilateral: p < 0.001) showed elevated titanium ion levels.

The data suggest that the present modular stem system does not result in elevated systemic titanium ion levels in the medium term when compared to non-modular stems. However, more outliner were seen in modular-neck THA. Further longitudinal studies are needed to evaluate the use of systemic titanium ion levels as an objective diagnostic tool to identify THA failure and to monitor patients following revision surgery.


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J. Philippe Kretzer V Pohl F Zeifang M Buelhoff Robert Sonntag Joern Reinders

Hemi shoulder arthroplasty is an attractive treatment for shoulder arthritis in particular if the natural glenoid is still intact. However, comparing the clinical results of hemi and total shoulder arthroplasty clearly shows lower survival for the hemi arthroplasty. One of the most common reasons for revision surgery is gleniod erosion, where the cartilage or bone is worn of. Aim of the current study was to analyse if the metallic articular surface of retrieved hemi shoulder arthroplasty is different from new implants. We hypothesized that the surface roughness will increased due the articulation and that metallic wear is detectable on the implants. Twelve retrieved and three brand new hemi shoulder arthroplasty were included. The surface roughness (Ra, Rz, Rmax, Rsk) was measured on different sites of the surface (center of the head and at the edge). The implants were further measured using a coordinate measuring machine to gain information on volumetric wear and geometrical alterations.

Compared to new implants the surface roughness on the retrievals was significantly increased (Tab. 1), except for skewness.

Although the roughness parameters within the retrieval group were generally higher at the center of the head compared to the edge, this difference was not significant. Apart from form deviations no volumetric wear was detectable on the heads (Fig. 1).

The current results indicate that the metallic articular implant surface changes in vivo and that the material is hurt due to the articulation against the softer cartilage or bone. Although it can't be finally clarified by that study, to what extend the higher roughness is taking part in the process of the clinically observed erosion of the gleniod, it can be assumed that an increased roughness is disadvantageous. Possibly, the observed surface alterations won't occur clinically with harder materiel (e.g. ceramic), but this even needs to be validated.


Amir Pourmoghaddam Stefan W Kreuzer Adam Freedhand

INTRODUCTION:

Unicompartmental knee replacement (UKR) facilitates the use of smaller sized implants that require less bone resection and allows preservation of the anterior and posterior cruciate ligaments (ACL and PCL)[1]. Therefore, UKR preserves the intact kinematics and may improve the clinical outcomes especially compared to the outcomes of total knee replacement (TKA). Despite the known benefits of UKR in arthritis limited to one compartment, in multicompartment disease TKA remains the gold standard. Current TKA designs require the sacrifice of the ACL in all cases, whereas the surgeon can decide to use a cruciate sparing or substituting design altering normal knee kinematics. Performing bi-UKR or tri-UKR with traditional instruments is very challenging and rarely done due to the difficulty in establishing the correct spatial relationship of the separate components. Recent advances in robotic surgery have provided the opportunity to utilize partial knee replacements. The MAKO Rio platform is a surgeon-interactive robotic arm with haptic guidance that allows computer assisted planning and intraoperative accurate placement of multiple unicompartmental components including the bi-UKR. Currently there is a lack of understanding about the short-term and long-term clinical outcomes of the bi-UKR compared to the traditional TKA.

OBJECTIVES:

The objective of the current study was to investigate the differences in the clinical outcomes of bi-UKR and TKA.


Amir Pourmoghaddam Stefan W Kreuzer Adam Freedhand

INTRODUCTION:

The popularity of the direct anterior approach (DAA) for total hip arthroplasty (THA) is increasing as this approach causes less soft tissue damage and no muscular detachments and significantly shorter postoperative recovery time. Despite the promising early results the complication rate in the DAA cases has been concerning such as 9% rate in 247 DAA cases reported by Woolen et. al [1]. As DAA has not conventionally being used by surgeons these complications are expected to be reduced when the surgeons are more experienced. Therefore to better understand the issues that cause the postop complications in DAA we have conducted the present study.

OBJECTIVES:

The objective of the current study is to investigate the postop complications in individuals with arthritic hips treated by DAA THA over a period of 3.5 years by a one surgeon.


Michael Kurdziel Sebastian Peers James Moravek Matthew Budge Michael Newton Kevin Baker J. Michael Wiater

Purpose:

Although short term outcomes of reverse total shoulder arthroplasty (rTSA) have been promising, long-term success may be limited due to complications, including scapular notching. Scapular notching has been explained primarily as a mechanical erosion, however, generation of wear debris may lead to further biologic changes contributing to the severity of scapular notching. Highly cross-linked ultra-high molecular weight polyethylene (UHMWPE) has been used routinely in constrained joint applications such as total hip arthroplasty for reduction of wear debris particles. Although rTSA shares similarity in design conformity, conventional UHMWPE remains the gold standard.

Methods:

A commercially available hip simulator was converted to a 12-station rTSA wear simulator. Conventional and highly cross-linked UHMWPE humeral liners were subjected to 5,000,000 cycles of alternating abduction-adduction and flexion-extension loading profiles. Every 250,000 cycles, liners were evaluated with gravimetric wear measurements and test serum was collected for morphological characterization of wear particles.


Yuichi Kuroda Kazunari Ishida Tomoyuki Matsumoto Hiroshi Sasaki Shinya Oka Katsumasa Tei Yohei Kawakami Tokio Matsuzaki Atsuro Uefuji Kanto Nagai Nobuhiro Tsumura Ryosuke Kuroda Masahiro Kurosaka

Background:

The axis of the fibula in the sagittal plane are known as a landmark for the extramedullary guide in order to minimize posterior tibial slope measurement error in the conventional total knee arthroplasty (TKA). However, there are few anatomic studies about them. We also wondered if the fibula in the coronal plane could be reliable landmark for the alignment of the tibia. This study was conducted to confirm whether the fibula is reliable landmark in coronal and sagittal plane.

Methods:

We evaluated 60 osteoarthritic knees after TKA using Athena Knee (SoftCube Co, Ltd, Osaka, Japan) 3-D image-matching software. Angle between the axis of the fibula (FA) and the mechanical axis (MA) in the coronal and sagittal plane were measured.


Yuji Kuroyanagi Hideaki Yoshida Ryoji Fujimaki Sota Kato Naoto Inaba

Total knee arthroplasty (TKA) provides good results even for severe knee osteoarthritis (OA) patients. However, patients often suffer from post-operative pain and have long rehabilitation periods. In recent years, utilization of unicompartmental knee arthroplasty (UKA) has increased in an effort to decrease pain and shorten recovery compared to TKA. Moreover, the long-term results of the UKA have improved. Many surgeons now wonder whether TKA or UKA is better for patients with isolated medial knee OA. In Japan, the government has public insurance system and patients are able to receive the joint replacement surgery inexpensively. This study was conducted to compare the cost the public insurance and the patients co-payment for TKA and UKA.

We investigated a series of thirty TKAs and fifteen UKAs performed in Fussa Hospital (Tokyo, Japan) from July 2012 to April 2013. Data from two TKAs' were excluded since the patients had comorbidities (asthma and severe DM) that extended their hospitalizations. Patients were discharged from the hospital if they were able to go up and down the stairs or were able to conduct routine activities of daily living.

Total payments the hospital received averaged $19600 (S.D. $1600) for a TKA and $15200 (S.D. $1300) for a UKA. Patients paied averaged of $690 (S.D. $370) for a TKA and $470 (S.D. $170) for a UKA (Figure 1). The surgical fee was $3769 for both TKA and UKA, and was uniform thoughout Japan. The implant price averaged $6200 (S.D. $300) for TKA and $3900 (S.D. $200) for UKA, where prices were also determined by the government. Hospitalization averaged 28 days (S.D. 7 days) for TKA and 21 days (S.D. 6 days) for UKA. For both TKA and UKA, the total cost and the number of days in hospital were highly correlated (R = 0.92 and R = 0.96, respectively). A linear cost model suggests the TKA cost was $210 times days of hospitalization plus $13100 and the UKA cost was $220 times days of hospitalization plus $10000. Patients' payments were not correlated to the days of hospitalization (R = 0.22 and R = 0.45, respectively).

TKA and UKA are performed all over the world now and the number of the surgeries increases each year. Althouth each country has a different insurance system, many countries face an increasing and problematic economic burden for both patients and insurance organization (either public or private company). This study showed UKA is less expensive than TKA by $4400, an advantage that might complement the traditional view that UKA is less invasive and often has fewer complications for treating isolating medical compartment OA. For Japanese system, patients pay relatively little out-of pocket despite long hospitalization, and length of stay has a direct and significant effect on total cost for TKA and UKA


Steven Kurtz Olga Zielinska Daniel MacDonald Harold Cates Michael Mont Arthur L Malkani Jay Parvizi Clare Rimnac

Introduction:

First generation highly crosslinked polyethylenes (HXPLEs) have proven successful in lowering both penetration and osteolysis rates. However, 1st generation annealing and remelting thermal stabilization have been associated with in vivo oxidation or reduced mechanical properties. Thus, 2nd generation HXLPEs were developed to improve oxidative stability while still maintaining material properties. Little is known about the in vivo clinical failure modes of these 2nd generation HLXPEs.

The purpose of this study was to assess the revision reasons, wear, oxidative stability, and mechanical behavior of retrieved sequentially annealed Vitamin E diffused HXLPE in THA and TKA.

Methods:

251 2nd Generation HXLPE hip and knee components were consecutively retrieved during revision surgeries and continuously analyzed in a prospective, IRB approved, multicenter study. 123 acetabular liners (Implanted 1.2y; Range 0–5.0y) and 117 tibial inserts (Implanted 1.6y; Range 0–5.8y) were highly crosslinked and annealed in 3 sequential steps (X3). Five acetabular liners (Implanted 0.6y; Range 0–2.0y) and six tibial inserts (Implanted 1.3y; Range 0.5–1.8y) were diffused with Vitamin E (E1). Patient information was collected from medical records (Table 1).

Linear penetration of liners was measured using a calibrated digital micrometer (accuracy: 0.001 mm). Surface damage of tibial components was assessed using the Hood method. Thin sections were taken from the acetabular liners (along the superior/inferior axis) and the tibial components (along the medial condyle and central spine) for oxidation analysis and analyzed according to ASTM 2102. Mechanical behavior was assessed via the small punch test (ASTM 2183).


Steven Kurtz Daniel MacDonald Genymphas Higgs Jeremy Gilbert Gregg Roger Klein Michael Mont Jay Parvizi Matthew Kraay Clare Rimnac

Introduction:

Degradation of modular head-neck tapers was raised as a concern in the 1990s (Gilbert 1993). The incidence of fretting and corrosion among modern, metal-on-polyethylene and ceramic-on-polyethylene THA systems with 36+ mm femoral heads remains poorly understood. Additionally, it is unknown whether metal debris from modular tapers could increase wear rates of highly crosslinked PE (HXLPE) liners.

The purpose of this study was to characterize the severity of fretting and corrosion at head-neck modular interfaces in retrieved conventional and HXLPE THA systems and its effect on penetration rates.

Patients & Methods:

386 CoCr alloy heads from 5 manufacturers were analyzed along with 166 stems (38 with ceramic femoral heads). Metal and ceramic components were cleaned and examined at the head taper and stem taper by two investigators. Scores ranging from 1 (mild) to 4 (severe) were assigned in accordance with the semi-quantitative method adapted from a previously published technique. Linear penetration of liners was measured using a calibrated digital micrometer (accuracy: 0.001 mm). Devices implanted less than 1 year were excluded from this analysis because in the short-term, creep dominates penetration of the head into the liner.


Jeremy Latham Richard Cook Ben Bolland Alison Wakefield David Culliford Charlie Tilley

Introduction

Metal on metal hip arthroplasty continues to be controversial. Emerging evidence suggests that there are multiple modes of failure, and that the results of revision surgery are influenced by host and implant factors.

Methods

This study compares a single surgeon series of hip resurfacings (Birmingham Hip Resurfacing {BHR}) and large diameter metal on metal total hip replacements (LDMOMTHR). Primary outcome measures included survival rates, failure secondary to histologically identified Adverse Reaction to Metal Debris (ARMD), and patient reported outcome measures (Oxford Hip Score {OHS}) following revision.

Between 1999 and 2005, 458 BHR and 175 LDMOMTHR were performed. At latest review 43 BHR's (9.4%) and 28 LDMOMTHR's (14%) have been revised.


Jean Yves Lazennec Adrien Brusson Jean Patrick Rakover MA Rousseau

Introduction

The viscoelastic lumbar disk prosthesis ESP is an innovative one-piece deformable but cohesive interbody spacer; it provides 6 full degrees of freedom about the 3 axes including shock absorption. The prosthesis geometry allows limited rotation and translation with resistance to motion (elastic return property) aimed at avoiding overload of the posterior facets. The rotation center can vary freely during motion. It thus differs substantially from current prostheses. This study reports the results of a prospective series of 120 patients who are representative of the current use of the ESP implant since 2006.

Material and methods

The surgeries were performed by 2 senior surgeons. There were 73 women and 47 men in this group. The average age was 42 (27–60). The average body mass index was 24.2 kg/m2 (18–33). The implantation was single level in 89% of cases. 134 ESP prostheses were analyzed.

Clinical data and X-rays were collected at the preoperative time and at 3, 6, 12, 24, and 36 months post-op.

The functional results were measured using VAS, GHQ 28, ODI, SF-36, (physical component PCS and mental component MCS. The analysis was performed by a single observer who was independent from the selection of patients and from the surgical procedure.


Jean Yves Lazennec Aidin Eslam Pour Adrien Brusson MA Rousseau Ian Clarke

Introduction

Femoral stem anteversion after total hip arthroplasty (THA) has always been assessed using CT scan in supine position. In this study, we evaluated the anteversion of the femoral prosthesis neck in functional standing position using EOS® technology with repeatability and reproducibility of the measurements. The data obtained were compared with conventional anatomic measurements.

Materials and Methods

We measured the anteversion of the femoral prosthesis neck in 45 consecutive patients who had THA performed in nine hospitals. All measurements were obtained using the EOS® imaging system with patients in comfortable standing position. The orientation of the final vector representing the femoral neck was measured on 3-dimensional reconstructions. The anatomic femoral anteversion was calculated as in a transverse plane relative to the scanner and to the plane of the reconstructed bicondylar femoral segment (femoral prosthesis neck against the femoral condyles). Functional femoral anteversion (FFA) was measured in the horizontal plane relative to the frontal plane of the patient through the center of two femoral heads. FFA embodies true anteversion of the femoral prosthesis neck relative to the pelvis, representing the combined lower extremity anteversion.


Jean Yves Lazennec Adrien Brusson E Ebramzadeh Ian Clarke

Unlike conventional radiographic methods, the newly introduced EOS system provides simultaneously-synchronized anteroposterior (AP) and true-lateral (LAT) x-ray images. EOS offers considerable potential for calculating parameters such as true femoral and acetabular angular positioning, impingement sites, and also for measuring wear in polyethylene cups. In this study we used THA wear-simulation fixtures to assess 3D-wear in polyethylene cups using EOS algorithms.

Material and methods

A validated phantom apparatus was used to simulate values of three-dimensional wear, controlled in the 3 directions (antero-posterior, medio-lateral, cranio-caudal) using micrometers. (Figure 1)

24 simulations of wear with controlled amplitudes and directions were imaged using the biplane EOS slot-scanning system. Wear amplitudes were between 0 and 3464 μm. Using dedicated software, wear was measured by a 2D/3D matching of 3D spheres onto the 2D frontal and lateral radiographs, allowing the determination of the 3D coordinates of both the cup and femoral head centers and thus the calculation of a 3D wear vector. (Figure 2)

Measured wear vector were compared to real wear vectors in terms of amplitude and direction.3D wear vectors were measured twice by 3 independent observers (for a total of 144 measurements) in order to evaluate intra- and inter-observer reliability.

Results

There was a strong correlation between the measured wear amplitude and the real wear amplitude (Pearson's r = 0,99). Mean error when comparing wear measurement amplitude with real wear amplitude was 356 μm (SD = 127 μm). None of the 144 measurements presented an error over 1 mm.

The accuracy of wear direction evaluation was highly correlated with wear amplitude (Spearman's rho = 0,98), the measurement of 3D wear direction presenting an accuracy better than 15° for wear amplitudes over 1,5 mm. Intra-observer errors for wear amplitude were between 138 μm and 221 μm depending on the observer. Inter-observer error for wear amplitude was 333 μm.


Kim-Phuong Le Jason Longaray Jacob Blitz Lin Song Shi-Shen Yau Aaron Essner

Introduction:

The solvent extraction step applied in conventional oxidation measurement protocols for UHMWPE retrievals resulted in an elevated oxidation index (OI) in remelted highly cross-linked UHMWPE (RM-HXLPE). The present study seeks to confirm the effect of solvent extraction on OI measurement and to understand the relationships among soak-aging, fluid uptake, and resulting OI from various test protocols.

Materials and Methods:

Two materials were tested, representing legacy gamma-in-air sterilized (GammaAir-PE, GUR4150, 30 kGy) and remelted highly cross-linked (RM-HXLPE, GUR1050, 100 kGy, 147°C/5h) UHMWPE. Concave discs approximately 19 millimeters (mm) in diameter and 3 mm in dome thickness were machined from both materials prior to soak-aging. Soak-aging consisted of a combination of: (1) ASTM F2003 accelerated aging (5 atm O2, 70 °C for 14 days), and (2) either static soaking (SS, for 11.57 days) or dynamic load-soaking (LS, 2280 N at 1 Hz for 1 million cycles) in bovine synovial fluid at 37 °C to simulate the combination of shelf and in-vivo aging, respectively. Unsoaked samples were used as control (C) group.

Thin films (150 μm) were harvested from cross-sections of all groups and were subjected to two solvent extraction protocols using Sohxlet (Heptane for 6 h (HEP6) or Hexane for 16 h (HEX16)) prior to be analyzed by two OI analyses using Fourier transform infrared spectroscopy (FTIR).

FTIR analyses (128 scans/spectra, 4 cm−1 resolution) were carried out using both peak height at and peak area centering 1714 cm−1 for OI and 1734 for fluid uptake index (FI); carbon-carbon vibration at 1368 cm−1 was used for normalization. All GammaAir-PE data was further normalized using prewash control while RM-HXLPE data used computed results.

The paired t-test was used with a significance level of p < 0.05.


Stephen Murphy Daniel Le

Introduction

Adverse Local Tissue Reactions (ALTR) have been reported in association with both wear and corrosion. Tissue reactions have been reported in association with corrosion at CoCr head-CoCr neck, CoCr head-TiAl6V4 neck, and CoCr modular neck on beta-titanium (TMZF) stem junctions. The current abstract reports on 3 cases of ALTR in association with CoCr modular necks on convention titanium (TiAl6V4) stem junctions.

Case 1. A 67 year old male (87 kg, 1.73 m, BMI 29.1) presented with new onset hip irritation 11 months after surgery. Radiographs show no abnormalities. Further investigation revealed the following: ESR = 95, CRP = 5, Cr level = 1.0, Co level = 4.1, leukocyte transformation testing = highly reactive to nickel. Hip aspiration was culture negative with 11,250 wbc. Metal artifact reduction MR showed cystic local reaction in the region of the greater trochanter.

Case 2. A 52 year old male (89 kg, 1.83 m, BMI 26.5) presented with new onset hip irritation 30 months after surgery. Radiographs show no abnormalities. Further investigation revealed the following: ESR = 7, CRP = 5.4, Cr level = 2.1, Co level = 4.8, leukocyte transformation testing = reactive to nickel. Hip aspiration was culture negative with 3995 wbc. Metal artifact reduction MR showed cystic local reaction in the region of the iliopsoas.

Case 3. A 52 year old male (104 kg, 1.85 m, BMI 30.1) presented with new onset hip irritation 26 months after surgery. Radiographs show no abnormalities. Further investigation revealed the following: ESR = 33, CRP = 34.9, Cr level = 1.0, Co level = 3.7, leukocyte transformation testing = no reactivity to any of the biomaterials. Hip aspiration was culture negative with 3,780 wbc. Metal artifact reduction MR showed cystic local reaction in the region of the iliopsoas.

Discussion

All three of these patients are scheduled for revision surgery. All three had ceramic-ceramic bearings. We have experience with 1029 ceramic-ceramic THA with fixed neck conventional titanium and modular titanium neck implants with minimum 2 yr f/u and have never diagnosed an adverse reaction in any of these patients. It is possible that corrosion at the CoCr neck on TiAl6V4 stem junction is the root cause of these reactions. Although the incidence of diagnosed reactions is roughly 1%, it appears that the use of CoCr at any junction under significant mechanical stress can result in adverse local tissue reaction and therefore should either be avoided or used with great caution and compelling indications.


Stephen Murphy William Murphy Daniel Le

Introduction:

Young patients have been reported to have a higher risk of revision following total hip arthroplasty (THA) than older cohorts, possibly to due higher activity and a higher incidence of deformity and prior surgery. Ceramic-on-ceramic bearing surfaces have been proposed for use in young and active individuals due to their low wear, low risk of adverse biologic reaction, and long-term survivorship. We assessed the clinical results and long-term survivorship of uncemented ceramic-on-ceramic THA in a young patient population.

Methods:

341 total hip arthroplasties in 218 patients under 50 years of age at the time of surgery were performed were performed using alumina ceramic-on-ceramic bearings from August 1999 to April 2009 as part of a prospective nonrandomized study. All patients received uncemented acetabular components with flush-mounted acetabular liners using an 18 degree taper and uncemented femoral components. The average patient age at the time of surgery was 41.7 years (range 17.8–49.9 years). The minimum follow-up time was 2 years, (mean 9.1, range 2–13.9). We evaluated implant-related complications and performed Kaplan-Meier analyses to determine survivorship of the femoral and acetabular components with revision for any reason as the endpoint.


Jungbum Lee Jeongyong Yoon Jaeik Lee

To investigate the effectiveness of avulsion fracture of tibial insertion of posterior cruciate ligament using the safe postero-medial approach through analyzing the clinical and radiographic outcomes. We treated 14 cases of acute PCL tibial avulsion fracture with “safe postero-medial approach”. The PCL and avulsion bony fragment was fixed with 1 cannuated screw and washer. The patients were assessed clinically and radiographically at 3 months, 6 months, and 12 months. Clinical examination for each visit included assessment of the knee range of motion, using goniometer and the posterior drawer test. The patients were evaluated according to the Lysholm and Tegner rating scales. Patients were followed-up for 12 to 16 months. X-ray showed that satisfactory reducdtion and bony healing was achieved in all cases. There was no neurovascular complication. All patients had negative posterior drawer tests. Excellent outcomes were reported by all patients with the Lysholm score system. And there was no signicant difference between the Tegner scores before injury and last follow-up. Surgical treatment of acute tibial avulsion fracture of the PCL with this approach can restore the stability and fuction of the joint safely in most patients without neurovascular complication. Therefore “safe postero-medial approach” may be suitable for the treatment of isolated tibial avulsion fracture of the PCL.


Keun Ho Lee Kyung Rae Ko Sang-Min Kim Seung-Jae Lim Young-Wan Moon Youn-Soo Park

Introduction:

The management strategy regarding optimally addressing polyethylene wear with a well-fixed acetabular shell remains controversial. The purpose of the present study was to document outcomes of cementation of a highly cross-linked polyethylene (PE) liner into a well-fixed acetabular metal shell in 36 hips

Materials & Methods:

We identified 37 patients (39 hips) who had undergone revision THA by cementation of a highly cross-linked PE liner into a well-fixed metal shell between June 2004 and April 2009. Of these patients, one (1 hip) died before the end of the 3-year evaluation and another was lost to follow-up. Thus, the study cohort consisted of 35 patients (36 hips). There were 23 males (24 hips) and 12 female (12 hips) patients with a mean age at time of revision surgery of 57.6 years (range, 38–79 years). All operations were performed by a single surgeon using only one type of liner. Clinical and radiographic evaluation was performed at a mean of 6.1 years (range, 3–8 years) postoperatively.


Jonathan Levy Louis Keppler Olivier Verborgt Geert Declercq Mark Frankle

Background and Motivation

Accurate placement of glenoid components in reverse and total shoulder arthroplasty has been shown to reduce the risk of implant failure (1, 2, 6). Surgical techniques and literature describe methods to determine favorable positions for implant placement (3, 4, 5) but achieving that position surgically remains a challenge. Placement of glenoid components is faced with the challenge of variable glenoid morphology on which conventional instrumentation does not always provide a reliable reference (6, 7, 8). Limited surgical exposure is another challenge since many anatomic landmarks are not visible to the surgeon to use as spacial reference. Anatomic landmarks and angles can be more reliabily selected on CT scans with 3-dimentional reconstruction (9,10) yet few methods allow for the reproducible translation of these plans to surgery. Navigation has produced better accuracy and lower variability than conventional instrumentation (11), yet its regular usage remains limited, especially in the shoulder.

Methods

A patient specific planning and guiding system has been developed for glenoid implant placement of total and reverse shoulder arthoplasty procedures. This method allows for preoperative planning on a patient specific virtual 3D model of the scapula derived from CT images (Figure 1), and guided placement of a pin which which serves as the central axis for determining proper implant position. An initial implant position was presented on the virtual model based on the methods described by the surgical technique of the corresponding procedure. These plans were either approved or adapted to a desired position within the planning software by the surgeons. Using this planned position as input, patient specific surgical guides were created which fit onto the exposed anatomy and guide the drilling of the pin (Figure 1). This method was tested on 14 cadavers, with attention directed to translation of the starting point from the original plan, the ability to reproduce the intended degree of inferior tilt, and the ability to reproduce the glenoid version angle.


David Licini Michael Meneghini

Introduction:

Efforts continue to reduce blood loss in total knee arthroplasty (TKA). Computer assisted surgery (CAS) has been shown to reduce outliers in component position and improve functional outcomes in TKA, yet few studies have reported specifically on blood loss. The primary study objective was to determine whether a modern abbreviated CAS protocol would reduce blood loss in TKA compared to conventional instrumentation. A secondary objective was to assess the effect of CAS on cost and surgical efficiency.

Methods:

A retrospective cohort study of 100 consecutive patients was performed comparing an abbreviated and modern CAS protocol versus conventional IM instrumentation. All TKAs utilized an identical surgical technique without any hemostatic agent. Blood loss was determined using drain output, change in hemoglobin, and calculated blood loss. Tourniquet times were recorded as an indicator of procedural efficiency. A cost analysis compared the CAS protocol to the cost associated with tranexamic acid (TXA) to reduce blood loss and long-leg alignment radiographs to optimize component position.


Seung-Jae Lim Keun Ho Lee Kyung Rae Ko Sang-Min Kim Young-Wan Moon Youn-Soo Park

Introduction:

Ceramic head with titanium-alloy sleeve offers a modular ceramic head solution for the damaged taper in revision total hip arthroplasty (THA). It can also be used in primary THA to reduce the risk of ceramic head fracture. The purpose of the present study was to report the intermediate-term outcomes of primary ceramic-on-ceramic THA with use of ceramic head with titanium-alloy sleeve.

Materials & Methods:

We evaluated 244 patients (271 hips) who had undergone primary ceramic-on-ceramic THA with use of BIOLOX® forte 32 mm ceramic head with titanium-alloy sleeve between November 2005 and August 2009. There were 158 males (175 hips) and 86 female (96 hips) patients with a mean age of 55.5 years. Clinical and radiographic evaluation was performed at a mean of 4.6 years (range, 2–7 years) postoperatively.


Michael Meneghini Luke Lovro David Licini

Introduction:

Although cementless total hip arthroplasty (THA) is well accepted, the optimal femoral component design remains unknown. Among early complications, loosening and periprosthetic fracture persist and are related to implant design. The purpose of this study is to compare the anatomic fit and early subsidence of two different stem designs: a modern, short taper-wedge design and a traditional fit-and-fill design.

Methods:

A retrospective cohort study of 129 consecutive cementless THAs using two different femoral stems was performed. A modern taper-wedge stem was used in 65 hips and a traditional proximal fit-and-fill stem was used in 64 hips. Radiographic analysis was performed at preoperative, immediate postoperative and 1-month postoperative intervals. The radiographic parameters of bone morphology via the canal-flare index, implant subsidence at 1 month, sagittal alignment, and the “anatomic fit” metrics of canal fill and associated gaps were measured and recorded.


Thomas Luyckx Matthias Verstraete Karel De Roo Wim Dewaele Jan Victor Johan Bellemans

Introduction

In this study, three-dimensional (3D) digital image correlation (DIC) was adopted to investigate the strain in the superficial medial collateral ligament (sMCL) of the human knee. To our knowledge, no reports or validation of 3D DIC measurement on human collagenous tissue exists.

The first part of this research project focused on the validation of 3D DIC (1) as a highly accurate tool for non-contact full field strain analysis of human collagenous tissue. In the second part, 3D DIC was used to measure the strain patterns in the superficial medial collateral ligament (sMCL) of the native knee (2). In a third part, the strain pattern in the sMCL after total knee arthroplasty (TKA) in an ‘optimal’ (3) and with a proximalised joint line (4) was analysed.

Methods

(1) Six fresh frozen human Achilles tendon specimens were mounted in a custom made rig for uni-axial loading. The accuracy and reproducibility of 3D DIC was compared to two linear variable differential transformers (LVDT's). (2) The strain pattern of the sMCL during the range of motion (ROM) was measured using 3D DIC in six fresh frozen cadaveric knees. The knees were mounted in a custom made rig, applying balanced tension to all muscle groups around the knee. The experiment was repeated after computer navigated implantation of a single radius posterior stabilised (PS) TKA in ‘optimal’ (3) and with a 4 mm proximalised joint line (4).


Akihiko Maeda Atsushi Kusaba Saiji Kondo Yoshikatsu Kuroki Noriyuki Hemmi Akihiko Maeda Masashi Tsuchida Naoyuki Hakuta

Introduction

Simultaneous bilateral total hip arthroplasty is now widely accepted for their economically and functionally advantages than staged total hip arthroplasty.

But there is concerning higher demands of blood transfusion than unilateral procedure.

Multiple studies suggest that tranexiamic acid (TXA) reduces perioperative blood loss.

However there is no report for simultaneous bilateral total hip arthroplasty in these studies.

Hypothesis

TXA reduces significant blood loss after bilateral total hip arthroplasty.

Patients and methods

We retrospectively reviewed the records of 12 patients who did not use TXA, and 12 patients who had used TXA. There were no significant differences between the groups in terms of demographics and preoperative Hb.

1g of TXA was administered just before first skin incision and 1g was administered 6 hours after surgery. Intra operative blood loss, the amount of drainage for the first operative day and perioperative Hb changes were recorded.


Shinichi Maeno Kenshi Sakayama Setsuya Kamei Seiji Saito Nobuyuki Fujita Masahiro Ishizaka Kazuki Kimura Kazuya Maeda Ko Onoda Kaori Sadakiyo Masaki Akutsu Toshiro Otani Ko Masumoto

Total Knee Replacement (TKR) has been proven to be an effective procedure not only to eliminate pain but also to achieve better knee function. Recent rehabilitation is basically focused on achieving better ROM and muscle strength. However, improvements of balancing or walking ability in detail have not been sufficiently elucidated yet.

Methods

91 consecutive knees of 70 patients, with medial osteoarthritis undergone TKR have been nominated in this study. All were done by a single surgeon, via mid vastus approach, using cemented PS implant with patellar resurfacing. Patients were arrowed to start full weight bearing from the next day.

Assessing walking ability, gait speed and width of a step were measured. As for balancing, “Functional Reach (FR)” which was the difference between arm's length and maximal forward reach (Duncan PW et al), “Timed Up and Go Test (TUG)” which was time while a patient rose from an arm chair, walked 3 meters, turned, walked back, and sat down again (Podsiadlo D et al), and possible period standing on one leg (one leg standing) were used. Every measurement was performed prior to the operation, 1,2,3,4 weeks, 2 months and 6 months after operation. Data of prior to the operation, 2, and 6 monts after the operation were analyzed by one-way repeated ANOVA, and then differences among means were analyzed using Bonferroni procedures. P-value lower than 5% is regarded as significant.

Result

Every result except for one-leg standing time on contralateral leg (non-operative side) showed the worst during the first week, followed by better results over time (Fig. 1,2,3). One leg standing time of operative leg reached maximum at 2 months of time, while the others revealed improvement even at 6 months of time. Interestingly, postoperative one leg standing period of contra-lateral leg showed improvement with similar tendency until 4 weeks, followed by reaching plateau over time.


Pankaj Mahindra Mohammad Yamin Harpal Singh Selhi Rajnish Garg Deepak Jain Akshdeep Bawa

INTRODUCTION:

Cementless total hip arthroplasty (THA) is gaining ground over cemented THA. The objective of this study was to assess survival rates of a ceramic on polyethylene THA implant after at least 3 years and to assess changes in acetabular bone structure.

MATERIAL AND METHODS:

Twenty five ceramic-on-polyethylene THA prostheses were implanted between 2010 and 2013. Mean age at the time of operation was 57.9 years. Clinical outcomes were assessed using the Harris hip score and Postel Merle d'Aubigné score. For each hip, radiographs were examined for acetabular radiolucent lines, changes in bone structure and trabeculae were assessed comparatively to the other hip and classified from no change to severe osteolysis. Changes in trabeculae served to assess the loads applied to the bone. Polyethylene wear was assessed using the Livermore method.


Kartik Mangudi Varadarajan Thomas Zumbrunn Harry E Rubash Henrik Malchau Guoan Li Orhun Muratoglu

Introduction:

Contemporary Posterior Cruciate Ligament (PCL) retaining TKA implants (CR) are associated with well-known kinematic deficits, such as absence of medial pivot motion, paradoxical anterior femoral sliding, and posterior femoral subluxation at full extension. The hypothesis of this study was that a biomimetic implant, reverse engineered by using healthy knee kinematics to carve the tibial articular surface, could restore normal kinematic patterns of the knee.

Methods:

Kinematics of the biomimetic CR and two contemporary CR implants (A, B) were evaluated during simulated deep knee bend and chair-sit in LifeModeler KneeSIM™ software. Anteroposterior motion of the medial and lateral femoral condyle centers was measured relative to a tibial origin. The implants were mounted on an average knee model created from magnetic resonance imaging (MRI) of 40 healthy knees. The medial and lateral collateral ligaments, posterior cruciate ligament, quadriceps mechanism, and the overall capsular tension were modeled. The soft-tissue insertions were obtained from the average knee model, and the mechanical properties were obtained from literature. In vivo knee kinematics of healthy subjects from published literature was used for reference.


Kartik Mangudi Varadarajan Thomas Zumbrunn Harry E Rubash Henrik Malchau Orhun Muratoglu Guoan Li

Introduction:

While kinematic abnormalities of contemporary TKA implants have been well established, a solution has not yet been achieved. We hypothesized that contemporary TKA implants are not compatible with normal soft-tissue function and normal knee motion. We propose a novel technique for reverse engineering advanced implant articular surfaces (biomimetic surface), by using accurate 3D kinematics of normal knees. This technique accounts for surgical placement of the implants, and allows design of tibial and femoral articular surfaces in conjunction.

Methods:

Magnetic resonance imaging was used to create 3D knee models of 40 normal subjects (24 male, 16 female, age 29.9 ± 9.7 years), and bi-planar fluoroscopy was used to capture 3D knee motion during a deep knee bend. These data were combined to create a 3D virtual representation of an average normal knee and its motion pathway. A TKA femoral component was mounted on the average knee, and moved through its normal kinematic pathway to carve out an articular surface from a tibial template (Fig. 1 and 2). The geometry of the resulting biomimetic tibia was compared to that of the native tibia, and a contemporary TKA tibial insert that uses the same femoral component.


Kartik Mangudi Varadarajan Thomas Zumbrunn Michael Duffy Harry E Rubash Henrik Malchau Andrew Freiberg Orhun Muratoglu

Introduction:

Dual Mobility (DM) hip implants have gained popularity for the treatment and preventions of instability. In DM implants a large diameter mobile insert matches the native femoral head size. However, studies have shown that the peripheral regions of such large diameter implants overhang beyond the native anatomy and can directly impinge against nearby soft tissues, especially the iliopsoas, leading to groin pain (Fig. 1). Soft-tissue impingement can also trap the mobile DM insert, leading to damage of its peripheral rim, which secures the small diameter inner head (Fig. 2). The goal of this research was to develop an anatomically contoured soft-tissue friendly DM insert.

Methods:

Various Anatomically Contoured Dual Mobility (ACDM) insert designs were constructed, wherein the outer articular surface extending from the pole to a theta (θ) angle, matched that of contemporary implants (Fig. 3). However, the articular surface in the peripheral region was moved inward towards the center, thereby reducing implant volume that could impinge on the soft tissue (Fig. 1 and Fig. 3). Finite element analyses were used to determine the insert-acetabular contact area under peak in vivo loads during different activities. Finite element analysis was also used to determine resistance to extraction of the inner head. Published data was used to compare the implant articular geometry to native anatomy. These analyses were used optimize the soft-tissue relief, while matching the load bearing contact area and the resistance to extraction of the inner head in contemporary implants.


Kartik Mangudi Varadarajan Michael Duffy Thomas Zumbrunn Harry E Rubash Henrik Malchau Andrew Freiberg Orhun Muratoglu

Introduction:

Large diameter femoral heads have been used successfully to prevent dislocation after Total Hip Arthroplasty (THA). However, recent studies show that the peripheral region of contemporary femoral heads can directly impinge against the native soft-tissues, particularly the iliopsoas, leading to activity limiting anterior hip pain. This is because the spherical articular surface of contemporary prosthesis overhangs beyond that of the native anatomy (Fig. 1). The goal of this research was to develop an anatomically shaped, soft-tissue friendly large diameter femoral head that retains the benefits of contemporary implants.

Methods:

Various Anatomically Contoured femoral Head (ACH) designs were constructed, wherein the articular surface extending from the pole to a theta (θ) angle, matched that of contemporary implants (Fig. 2). However, the articular surface in the peripheral region was moved inward towards the femoral head center, thereby reducing material that could impinge on the soft-tissues (Fig. 1 and Fig. 2). Finite element analysis was used to determine the femoroacetabular contact area under peak in vivo loads during different activities. Dynamic simulations were used to determine jump distance prior to posterior dislocation under different dislocation modes. Published data was used to compare the implant articular geometry to native anatomy (Fig. 3). These analyses were used to optimize the soft-tissue relief, while retaining the load bearing contact area, and the dislocation resistance of conventional implants.


Kenneth Mann Mark Miller

INTRODUCTION:

Clinical densitometry studies indicate that following TKR implantation there is loss of bone mineral density in regions around the implant. Bone density below the tibial tray has been reported to decrease 36% at eight years after TKR. This bone loss (∼5%/year) is substantially greater than osteoporosis patients in the same age group (∼1–2%/year) and could contribute the loss of mechanical support provided by the peri-implant leading to loosening of components in the long term. High patient mass and body mass index have also been implicated in increased loosening rates, and was thought to be due to high stress or strain on the tibial constructs. These findings suggest that peri-implant bone strain may be affected by time in service and patient factors such as body mass.

The goal of this project was to assess the proximal tibial bone strain with biomechanical loading using en bloc retrieved TKR tibial components. Note that the implants were not obtained from revision surgery for a loose implant, but rather after death; thus the implants can be considered to be successful for the lifetime of the patient. We asked two research questions, guided by the clinical and laboratory observations: (1) are the peri-implant bone strain magnitudes for cemented tibial components greater for implants with more time in service and from older donors?, (2) is tibial bone strain greater for constructs from donors with high body weight and lower peri-implant BMD?

METHODS:

Twenty-one human knees with cemented total knee replacements were obtained from the SUNY Upstate Medical University Anatomical Gift Program. Clinical bone density scans were obtained of the proximal tibia in the anterior-posterior direction. Axial loads (1 body weight, 60/40% medial to lateral) were applied to the tibia through the contact patches identified on the polyethylene inserts. Strain measures were made using a non-contacting 3-D digital image correlation (DIC) system. Strain was measured over six regions of the bone surface (anterior (A), posterior (P), medial (M), lateral (L), postero-medial (PM), postero-lateral (PL)) (Figure 1).


Mohsen Mardani-Kivi

Background:

Historically, performing a successful hip joint replacement in patients aged fewer than 30 years has been an orthopedic challenge. The newer generation of prostheses and surgical techniques has the potential to increase the longevity of implants. The purpose of this study was to evaluate the outcomes of cementless hip arthroplasty in patients aged fewer than 30 years.

Materials and Methods:

In this cross-sectional study, 41 patients (46 hips) were studied with a mean age of 24, 4 (from 17 to 30 years) of whom underwent cementless metal – polyethylene hip arthroplasty from 2004 to 2007. The Harris hip score (HHS) was used to assess the functional consequences. Patients were followed up in terms of early complications (thrombophlebitis of the lower limbs, dislocation, hematoma and infection) and late complications (aseptic loosening, dislocation, and reoperation) at weeks 3 and 6, at 3 and 6 months, one year after surgery and annually thereafter.


Masaaki Maruyama Keiji Tensho Shinji Wakabayashi Kenji Hisa

BACKGROUND:

Although most radiographs used for polyethylene wear measurements have been taken with the patient in the supine position in order to assess penetration by the femoral head into the acetabular polyethylene socket, we have questioned the effect of weight-bearing on the position of the head within the socket. The current study aimed to determine the effect of weight bearing, i.e. standing on the two-dimensional radiographic position of the femoral head within the socket.

PATIENTS AND METHODS:

A total of three hundred and fifty patients (three hundred and eighty three hips) who had had a total hip arthroplasty had digital radiographs made a set of anteroposterior radiographs for each patient: one radiograph was made with the patient supine and one was made with the patient standing in full weight bearing on the replaced hip. The patients were divided into the following two groups: 1) seventy-five patients (eighty-three hips) with conventional polyethylene (CON) (group-1); 2) two hundred and seventy-five patients (three hundred hips) with highly cross-linked polyethylene (XPL) (group-2).

The set of radiograph was taken at three weeks postoperatively and at the time of semiannual follow-up. The average ceramic femoral head penetration was measured with radiographs taken in the standing or supine position at the final follow-up and compared with those of three weeks postoperatively. A single researcher with use of a computerized measurement system performed all measurements on the radiographs of the two-dimensional position of the head. Follow-up period were 13.5 ± 1.0 (range. 11.0–15.5) years in group-1 and 7.6 ± 2.1 (range. 5.0–12.6) years in group-2.


Garret Garofolo Nimrod Snir Brian Park Theodore Wolfson Mathew Hamula Nachum Levin Scott Marwin

Background:

Dual mobility components in total hip arthroplasty have been successfully in use in Europe for greater than 25 years. However, these implants have only recently obtained FDA approval and acceptance among North American arthroplasty surgeons. Both decreased dislocation rate and decreased wear rates have been proposed benefits of dual mobility components. These components have been used for primary total hip arthroplasty in patients at high risk for dislocation, total hip arthroplasty in the setting of femoral neck fracture, revision for hip instability, and revision for large metal-on-metal (MoM) hip articulation. The literature for the North American experience is lacking.

Purpose:

We report indications, short term outcomes, and complications of a series of subjects who received dual mobility outcomes at one institution.


Garret Garofolo Nimrod Snir Brian Park Theodore Wolfson Mathew Hamula Scott Marwin

Background

Revision surgery for failed metal-on-metal (MOM) total hip arthroplasty (THA) or hip resurfacing (HR) has been a challenge. Previous studies have reported high failure and complication rates, including dislocation, infection, aseptic loosening and lower patient satisfaction. Options for revision depend on the integrity and stability of the femoral and acetabular components. When both components fail, full revision is required; however, when the acetabular component remains well fixed and oriented, only the isolated femoral component revision can be performed. Dual mobility components can be utilized to match the size to the inner diameter of the metal cup. With the dual mobility implant, the morbidity and complications associated with cup revision are avoided while maintaining a natural femoral head size and potentially increasing range of motion and stability postoperatively compared to standard THA.

Purpose

The aim of this study was to evaluate short- to mid-term results of revision THA after failed metal-on-metal THA or HR using the dual mobility device.


Milad Masjedi Adeel Aqil Wei Liang Tan Jaskaranjit Sunnar Simon Harris Justin Cobb

Introduction:

Cam type femoroacetabular impingement (FAI) may lead to osteoarthritis (OA)[1]. In 2D studies, an alpha angle greater than 55° was considered abnormal however limitations of 2D alpha angle measurement have led to the development of 3D methods [2–4]. Failure to completely address the bony impingement lesions during surgery has been the most common reason for unsuccessful hip arthroscopy surgery [5]. Robotic technology has facilitated more accurate surgery in comparison to the conventional means. In this study we aim to assess the potential application of robotic technology in dealing with this technically challenging procedure of cam sculpting surgery.

Methods:

CT scans of three patients' hips with severe cam deformity (A, B and C models) were obtained and used to construct 3D dry bone models. A 3D surgical plan was made in custom written software. Each 3D plan was imported into the Acrobot Sculptor robot and bone resection was carried out. In total, 42 femoral models were sculpted (14/subset), thirty of which were performed by a single operator and the remaining 12 femurs were resected by two other operators. CT of the pre/post resected specimens was segmented and a 3D alpha angle and head neck ratios were measured [3–4] and compared using Mann-Whitney U test. Coefficient of variation (CV) was used to determine the degree of variation between the mean and maximum observed alpha angles for inter and intra observer repeatability.


Milad Masjedi Simon Harris Justin Cobb

INTRODUCTION:

The 3D shape of the normal proximal femur is poorly described in current designs of proximal femur prosthesis. Research has shown that in current implant designs with small diameter femoral heads the moment arm of the ilio-psoas tendon is reduced causing weakness in full extension, while large femoral heads cause psoas tendon impingement on the femoral head neck junction [1]. The femoral head-neck junction thus directly influences the hip flexor muscles' moment arm. Mathematical modeling of proximal femoral geometry allowed a novel proximal femur prosthesis to be developed that takes into account native anatomical parameters. We hypothesized that it is possible to fit a quadratic surface (e.g. sphere, cylinder…) or combinations of them on different bone surfaces with a relatively good fit.

METHODS:

Forty six ‘normal’ hips with no known hip pathology were segmented from CT data. Previous research has shown the femoral head to have a spherical shape [2], the focus here was therefore mainly on the neck. The custom-written minimization algorithm, using least squares approximation methods, was used to optimize the position and characteristics of the quadratic surface so that the sum of distances between a set of points on the femoral neck and the quadratic surface was minimized. Furthermore, to improve upon current design regarding the transition between head and the neck, we recorded the position of the head neck articular margin in addition the slope of the transition from head to neck in the above 46 hips.


Leo Massari Araldo Causero Paolo Rossi Pier Paolo Grillo Alessandro Bistolfi Gaetano Gigliofiorito Carlotta Pari Andrea Francescotto Piermario Tosco Davide Deledda Giulia Carli Silvia Burelli

Introduction

Trabecular Titanium™ is a highly porous biomaterial with a regular hexagonal cell structure, which has shown excellent mechanical properties. Several in vitro studies reported promising data on its osteoinductive and osteoconductive properties. Furthermore, it has demonstrated in vivo to enhance bone in-growth. Aim of this multicentre prospective study was to assess Trabecular Titanium™ osseointegration by measuring change in bone mineral density (BMD) around a cementless DELTA-TT cup with dual-emission X-ray absorptiometry (DXA).

Methods

89 patients (91 hips) underwent primary THA with DELTA-TT cups (Lima Corporate) between 2009 and 2010. There were 46 (52%) men and 43 (48%) women, with a median (IQR) age of 67 (57–70) years and a median (IQR) BMI of 26 (24–29) kg/m2. Right side and left side were affected in 44 (48%) and 47 (52%) cases, respectively. Underlying pathology was primary osteoarthritis in 80 (88%) cases, osteonecrosis in 5 (6%), post-traumatic osteoarthritis in 3 (3%), developmental dysplasia of the hip in 2 (2%) and oligoarthritis in 1 (1%). BMD was determined by DXA using DeLee and Charnley 3 Regions of Interest (ROI) at 7 days, 3, 6, 12 and 24 months. Clinical evaluation (Harris Hip Score, HHS), patient health status survey (SF-36) and radiographic assessment were performed preoperatively and at the same time-points. Data were analyzed using non-parametric tests (Mann-Whitney, Wilcoxon signed-rank) and a p < 0.05 as threshold for statistical significance.


Takayuki Matsuhisa Hiroaki Tsutsui Naoya Nishinaka Taishi Uehara Takashi Atsumi

Introduction:

The treatment of 3- or 4-part proximal humeral fractures in elderly can be carried out with hemiarthroplasty. Also hemiarthroplasty has performed for failed osteosynthesis or conservative treatment in Japan. However the secondary hemiarthroplasty has poor clinical outcome. The aim of this study was to compare the clinical outcomes of primary and secondary hemiarthroplasty for proximal humeral fractures.

Materials and Methods:

Between March 2004 and January 2013, twenty-four shoulders in 23 patients (22 females, 1 male) with proximal humeral fractures and fracture dislocations underwent hemiarthroplasty. The mean age was 75.6 years and the average follow-up period was 25.6 months (range 3 to 108 months). Eighteen shoulders in 17 patients were treated primary with hemiarthroplasty (primary group). Six shoulders in 6 patients were treated with hemiarthroplasty after other treatments had failed (secondary group). All patients were evaluated with the Japan Orthopaedic Association shoulder scoring system (JOA score) and range of motion.


Kazuaki Matsumoto Tatsuya Tamaki Yoko Miura Kazuhiro Oinuma Hideaki Shiratsuchi

Introduction:

The lateral radiographs are useful in evaluation of the acetabular cup anteversion. However, this method was affected by variations in pelvic position and radiographic technique. In this study, we employed the ischial axis (IA) as an anatomical landmark on the lateral radiographs, and we investigated a relationship between IA and the anterior pelvic plane (APP) using three-dimensional computed tomography (3D-CT). Using these findings, we report a new method for accurate measurement of the acetabular cup anteversion on plain lateral radiographs using IA as an anatomical reference.

Materials and Methods:

At first, preoperative3D-CT images were obtained in 109 patients who underwent total hip arthroplasty. The diagnosis was osteoarthritis in all patients. The angle between the IA (defined by a line connecting the anterior edge of the greater sciatic notch and the lesser sciatic notch) and APP (defined by the bilateral anterosuperior iliac spine and the symphysis) was measured on 3D-CT (Fig. 1). Secondly, postoperative lateral radiographs were obtained at 2 weeks, 4 weeks, 12 weeks, 24 weeks, and 52 weeks after surgery in 15 patients. The angle between a line tangential to the opening of the cup and a line perpendicular to APP was measured (Fig. 2). Three methods of acetebular cup position assessment were compared: 1) the present method, 2) Woo and Morrey method, and 3) software (2D template, Kyocera) method.


Michael Ast David J. Mayman Edwin Su Michael Parks Alejandro Gonzalez Della Valle Mathais Bostrum Steven B. Haas

INTRODUCTION

Wasted implants represent both an increased risk and cost to our healthcare system. In our institution, a sterilely packaged implant that is opened and not implanted is wasted in one out of 20 primary total knee replacement procedures. The cost of these wasted implants exceeds $1 million per year. We propose the introduction of a novel, computer based, e.Label and compatibility system to reduce implant-related medical errors and waste in total knee arthroplasty. We hypothesize that the implementation of this system will help reduce medical errors and wasted implants by improving and standardizing the visual markers and by ensuring that parts are compatible so that implant mismatches and inappropriate laterality are prevented.

METHODS

A software program was implemented which creates an e.Label for all components (Figure 1) and checks imbedded, manufacturer provided, compatibility charts to ensure that parts are of appropriate laterality, and are compatible with each other. Upon implementation, the program was studied prospectively for seven months and compared to a retrospective cohort in regards to number, type, and cost of wasted implants. Critical errors that were detected were also recorded.


Edward McPherson Michelle Burgett Thomas Halim Thomas Donaldson Ian Clarke

Controversy has existed for decades over the role of fretting-corrosion in modular CoCr heads used with stems of CoCr vs Ti6Al4V. Since retrieval data on taper performance remains scant, we report here an18-year survivorship of a Ti6Al4V: CoCr combination (APR design; Intermedics Inc). Unique to this study were the threaded profiles present on both stem and head tapers (Fig. 1).

This female patient was revised for pain, osteolysis and recurrent hip dislocation at 17 years, 10 months. A prior MPE hip replacement performed for her severely dysplastic right hip had lasted 11 years. At this 2nd revision, the 28 mm CoCr head was found dislocated posteriorly and superiorly. Metallosis was evident in the tissues. The polyethylene liner showed extensive rim damage on both anterior and posterior aspects. The neck of her APR Revision stem (Intermedics Inc) had worn through the polyethylene rim and impinged on the metal cage. The cage was found loose, the liner had disassociated, and the peri-trochanteric areas were compromised by massive osteolysis. The femoral stem and head were removed together without disassembly. The femoral stem and acetabular construct were replaced by an ARCOS revision system using 36 mm head with a Freedom cup (cemented to Max-Ti cage; Biomet Inc.).

The complete femoral neck and head were bi-valved assembled in horizontal plane for direct imaging by interferometry and SEM (Fig. 1a). After sectioning the head separated from the stem. Quantitative imaging used 1 to 5 regions with 6-replicate measurements per region and differentiation into contact and non-contact zones (Fig. 1b). Visual corrosion mapping (3) was recorded digitally in 4 anatomical views (Figs 1b–f).

The thread profile on contact zone inside the head (Fig. 2a) had a pitch of approximately 40 μm and a peak-to-valley depth of 4 μm overall (Fig. 2b profile section of thread: PV = 2 μm). The thread profile on stem trunnion (Fig. 3a) had a pitch of approximately 125 μm and a peak-to-valley depth of 3.5 μm overall (Fig. 2b profile section of thread: PV = 1 μm). Thus the stem trunnion thread was much coarser than the head. Overall corrosion grading was judged very mild. Overall we were satisfied that this Ti6Al4V: CoCr combination taper junction with threaded interfaces had performed very well for 18 years. Nevertheless, our visual grading was subject to opinion and thus unrewarding. The continuing project will quantify the contacting and non-contacting regions of head and stem (Fig. 1b).


Patrick Meere Peter Walker Christopher Bell

Obtaining accurate bone cuts based on mechanical axes and ligament balancing, are necessary for a successful total knee procedure. The OrthoSensor Tibial Trial displays on a GUI the magnitude and location of the lateral and medial contact forces at surgery. The goal of this study was to develop algorithms to inform the surgeon which bone cuts or soft tissue releases were necessary to achieve balancing, from an initial unbalanced state.

A rig was designed for lower body specimens mounted on a standard operating table. SURGICAL TESTS were then defined: Sag Test, leg supported at the foot; Dynamic Heel Push test, flexing to 120 degrees with the foot sliding along a rail; Varus-Valgus test; AP Drawer test; Internal-External Rotation test. The bone cuts were made using a Navigation system, matching the Triathlon PCL retaining knee. To determine the initial thickness of the tibial trial, the Sag Test was performed to reach 0 deg flexion. The Heel Push Test was then performed to check the AP position of the lateral and medial contacts, from which the rotational position of the tibial tray was determined. Pins were used to reproduce this position during the experiments.

SURGICAL VARIABLES were then defined, which would influence the balancing: LCL Stiffness, MCL Stiffness, Distal Femoral Cut Level, Tibial Sagittal Slope, Tibial Varus or Valgus, and AP Femoral Component Length. Balancing was defined as equal lateral and medial forces due to soft tissue tensions throughout the flexion range, equal varus and valgus stiffnesses, and no contacts closer than 10 mm to component edges. All of the above tests were then performed sequentially, and the changes in the contact force readings were considered as a signature of that Surgical Variable.

Testing was carried out on 10 full leg specimens. The Sag Test was the basic test for determining the thickness of the tibial insert. The Heel Push Test was then implemented from which force data throughout flexion was determined; followed by the Varus-Valgus Test. In a surgical case, this data will be used in a decision tree to identify which Surgical Variable required correction. In the experiments, by obtaining the above data for each SURGICAL VARIABLE in turn, we were able to determine a SIGNATURE for each SURGICAL VARIABLE. It was found that there was considerable variation in the force magnitudes between knees. However the SIGNATURES were sufficient to point to the specific SURGICAL VARIABLE requiring correction. In some knees, although there was a dominant SURGICAL VARIABLE, even after correcting for that, there was still an imbalanced state, requiring a second correction.

This research provided the fundamental principles and data for:

Defining tests to be carried out at surgery, to obtain force data to determine the SURGICAL VARIABLE to correct.

Defining the algorithm based on Closest Approach, for building up a database of data for predictive purposes.

How to use the Sag Test and the Varus-Valgus test as primary indicators.

How to use the AP Drawer test and the Internal-External Rotation test as fine tune indicators.


Morteza Meftah Philip Noble Stephen J Incavo

Background:

The Rejuvenate modular neck stem (Stryker, Mahwah, NJ) was recently recalled due to corrosion at the neck-stem junction. The purpose of this study was to investigate the rate of corrosion related failures and survivorship of this implant, and analyze the correlation between the implant and patient factors with serum metal ion levels.

Material and Methods:

Between June 2009 and July 2012, 123 Rejuvenate stems (97 modular and 26 non-modular) THAs were implanted in 104 patients by a single surgeon via a modified anterolateral approach. Serum Cobalt (Co) and Chromium (Cr) levels (microgram per liter [μg/L]) were obtained in all patients. In cases of elevated serum metal ion levels or symptomatic hip, patients underwent magnetic resonance imaging (MRI) for assessment of osteolysis or adverse local tissue reactions (ALTR). Correlation between implant factors (implant size, head size, head length, offset), patient factors (age, gender, BMI) with serum metal ion levels and revisions were analyzed using logistic regression models.


Morteza Meftah Kevin Hwang Sabir Ismaily Stephen Incavo Kenneth Mathis Philip Noble

Introduction:

Proper rotational alignment of the tibial component is a critical factor in the outcome of total knee arthroplasty (TKA), and misalignment has been implicated as a major contributing factor to several mechanisms of TKA failure. In this study we examine the relationship between bony and soft tissue tibial landmarks against the knee motion axis (plane that best approximates tibiofemoral motion through range of motion).

Methods:

The kinematic motions of 16 fresh-frozen lower limb specimens were analyzed in simulated lunging and squatting. All the tendons of the quadriceps and hamstrings were independently loaded to simulate a lunging or squatting maneuver. All specimens underwent CT scan and the 3D position of the knee was virtually reconstructed. Ten anatomic axes were identified using both the intact tibia and the resected tibial surface. Two axes were normal vectors to either the medial-lateral plateau center or the posterior tibial surface. Seven axes were defined between the tibial tubercle (the most prominent point, center of the tubercle, or medial third of the tubercle) and soft tissue landmarks of the tibia (the medial insertion of the patellar tendon, the center of the PCL and ACL, and the tibial spines). The last axis was the Knee Motion Axis (KMA), which was defined as the longitudinal axis of the femur from 30 to 90 degrees of flexion.


Menachem Meller Mark Gonzalez A. Seth Greenwald

The prevalence of Class III Obesity (BMI ≥ 40 kg/m25) in black women is 18%, three times the 6 national average. Class III obesity is associated with mobility limitations, particularly hip joint 7 deterioration. Therefore black women are highly likely to come to the attention of orthopedic 8 surgeons. Weight loss associated with bariatric surgery should lead to enhanced success of hip 9 replacements. However, we present a case of a black woman who underwent Roux-en-y gastric 10 bypass with the expectation that weight loss would improve her ambulation and if necessary 11 make her a better surgical candidate for hip replacement. Her gastric bypass was successful as her BMI declined from 52.0 kg/m2 to 33.7 kg/m212. However, her hip circumference post weight 13 loss remained persistently high. As a consequence, the soft tissue tunnel geometry presented 14 major challenges. The tunnel depth as well as the immobility of the soft tissue envelope 15 interfered with retractor placement, tissue reflection and adequate surgical access to the 16 acetabulum. Therefore a traditional cup placement could not be achieved. Instead, a 17 hemiarthroplasty was performed. Her pre-surgery Harris Hip Score was 17.0. In the first few 18 months post surgery there were improvements, specifically a decrease in pain and a decreased 19 reliance on external support. But her overall functional independence never improved. This case 20 is presented to raise awareness that improved BMI category post bariatric surgery is not 21 sufficient to guarantee that orthopedic risks have been minimized. Overall, weight loss does 22 improve both the metabolic profile and anesthesia risk, but the success rate of total hip 23 arthroplasties will be low if fat mass (i.e. high hip circumference) in the operative field remains 24 high. We are now repeatedly recognizing this problem but are not finding any case reports on 25 this issue. Therefore we provide a practical approach to evaluate these patients and describe 26 ways we have found to successfully address intra-operative challenges.


Michael Meneghini Luke Lovro Shelly Smits Philip Ireland

Introduction:

Although commonly used, the clinical performance of highly crosslinked polyethylene in total knee arthroplasty (TKA) remains unknown and concerns exist regarding fatigue resistance and oxidation, particularly in posterior-stabilized (PS) designs. The purpose of this study is to compare highly crosslinked and conventional polyethylene in a PS TKA design at a minimum of 5-years.

Methods:

A prospective cohort study of 114 consecutive TKAs in 83 patients was performed as a subset of a multi-center prospective study. All TKAs utilized an identical PS design. Conventional polyethylene inserts were used in 50 knees and second-generation highly cross-linked polythethylene inserts were implanted in 64 TKAs. All patients were followed with clinical outcome measures (Short-Form 36, Knee Society Scores, WOMAC and LEAS) and radiographically for a minimum of 5 years.


Rene Mihalic Rihard Trebe Darij Kreuh

Background

Periacetabular osteotomy (PAO) is an effective treatment method for early or mild osteoarthritis caused by developmental dysplasia of the hip. Since the procedure is performed from late eighties of the past century it is still a very demanding procedure performed only by high skilled surgeons in high volume orthopaedic centres. The idea was to develop a custom-made surgical tool to improve the accuracy of the two osteotomies of the iliac bone and help us to avoid inadvertent intraarticular osteotomy of the acetabulum.

Methods

Firstly CT scans of pelvises of two cadavers were performed. The DICOM format files were up-loaded into EBS software (Ekliptik d.o.o., Ljubljana, Slovenia), application for preoperative planning, constructing and designing different templates, where the three-dimensional (3D) model of each pelvis was created. On the virtual pelvis models the PAO lines on each of four acetabuls were placed and virtual PAOs were performed [Fig. 1]. For the execution of the two iliac bone osteotomies the osteotome or saw guiding jigs were virtually created and exported in STL format in ProJet 3500 HDPlus printer which created custom made jigs made from VisiJet Crystal biocompatible plastic material (3D systems, Rock Hill, South Carolina, USA) for each of the four acetabula. The next step was the surgery on aforementioned cadavers. Extended Smith-Petrson approach was performed on each of four cadaveric hips and Bernese PAOs were performed using custom-made jigs. After performing the acetabular correction the cadavers were carefully dissected to study any possible posterior column damage or damage of the acetabular wall. None of them were damaged and the osteotomies were performed according to the virtual plan.

Next step was the real procedure on 47-years old female patient with bilateral acetabular dysplasia. The procedure was executed on right side using the extended Smith-Peterson approach. Preoperatively native X-ray of both hips and the CT scan of pelvis were performed. According the CT scan (DICOM format) the virtual 3D model of the pelvis was created and virtual osteotomy lines were decided and production of the appropriate jig was manufactured in the same manner as for the cadavers [Fig. 2]. Preoperative and postoperative centre-edge (CE) angles were measured.


Mark Mighell Jeremy Miles Brandon Santoni Leon Anijar Chistopher James

Purpose:

Tuberosity healing in hemiarthroplasty for proximal humerus fractures remains problematic. Improved implant design and better techniques for tuberosity fixation have not been met with improved clinical results. The etiology for tuberosity failure is multifactorial; however thermal injury to host bone is a known effect of using polymethylmethacrylate for implant fixation. We hypothesized that the effect of thermal injury at the tuberosity shaft junction could be diminished by utilizing an impaction grafting technique for hemiarthroplasty stems.

Methods:

Five matched pairs of cadaveric humeri were skeletonized and hemiarthroplasty stems were implanted in the proximal humeri in two groups. The first group had full cementation utilized from the surgical neck to 2 cm distal to the stem (cement group) and the second group had distal cementation with autologous cancellous bone graft impacted in the proximal 2.5 cm of the stem (impaction grafting group). Thermocouples were used to measure the inner cortical temperature at the tip of the stem, surgical neck, and at the level of the cement-graft interface for both treatment groups (see Fig. 1). Experiments were initiated with the humeri fully submerged in 0.9% sodium chloride and all three thermocouples registering a temperature of 37 ± 1°C. Statistical analyses were performed with a one-sided, paired t-test.


Kenneth Mann Mark Miller Jacklyn Goodheart Timothy H Izant Clare Rimnac Richard Cleary

INTRODUCTION:

Aseptic loosening continues to be a short and long-term complication for patients with cemented knee replacements. Changes in cemented total knee replacement (TKR) fixation have been limited to assessment of radiographic changes at the implant-bone interface and quantification of component migration. The goal of this study was to determine the interlock morphology between cement and trabecular bone using en bloc postmortem retrieved TKR. Note that these retrievals were not obtained from revision surgery for a loose implant, but rather after death. Thus the implants can be considered successful for the lifetime of the patient. We hypothesized that constructs with greater time in service have less interlock between cement and bone and constructs with more estimated initial interlock sustain more interlock with in-vivo service.

METHODS:

Twelve retrieved tibial components and two lab-prepared constructs with time in service from 0 to 20 years were sectioned in the transverse plane in 10 mm increments, imaged at high resolution, and the current contact fraction (curCF), estimated initial interdigation depth (inID), current interdigitation depth (curID), and loss of interdigitation depth (lossID) were quantified at the cement-bone interface. Contact fraction was determined using a stereology method using random ray projections (Figure 1A). The trabecular shape cast into the cement layer upon curing was used to document the initial penetration of bone into the cement. A line tracing algorithm was used to determine interdigiation depth (Figure 1B).


Brent Mitchell

Additive manufacturing (AM) techniques have gained attraction in orthopedic implant design with their ability to create unique shapes and structures. Depending on the application, there are different mechanical properties required. This study evaluated the mechanical properties of direct metal laser sintered (DMLS) Titanium alloy (Ti6Al4V) with and without hot isostatic pressure (HIP) treatment.

Three dimensional computer modeling and the DMLS manufacturing assisted in building net or near-net samples for testing. The material testing consisted of uniaxial tension, Charpy impact, rotating beam fatigue (RBF), density, and hardness. Two sets of Ti6Al4V samples were created for testing using a DMLS process and stress relieved in a vacuum furnace prior to removal from the build platform. One set of samples were HIP treated. The two sets of samples were tested and the material properties of the non-HIP treated samples were compared to those with HIP treatment.

Tension testing was conducted on fifteen (15) samples per treatment according to ASTM E8/E8M on as-built samples designed to a round specimen 3 per the standard. Fifteen (15) Charpy impact samples per treatment were built to near-net shapes. A low stress grind was performed on all surfaces and a notch was placed in the sample to comply with ASTM E23 and testing was performed in accordance with the standard. Fifteen (15) samples were built per treatment and machined for RBF per ISO 1143. RBF was performed on all samples at a frequency of 100 Hz with run out conditions of 10M cycles or failure. Density and hardness was measured on three (3) samples from each set using Archimedes' Principle and Rockwell hardness techniques respectively.

The average (standard deviation) tensile strengths between the two groups were statistically different (p < 0.05). The non-HIP treated samples had an average ultimate strength of 956(10) MPa, yield strength of 896(13) MPa, and modulus of 118(2) GPa (Table 1). The HIP treated samples had an average ultimate strength of 909(4) MPa, yield strength of 832(9) MPa, and modulus of 112(3) GPa (Table 1). There was also statistical differences in the impact strength with the HIP treatment samples having a higher required force of 23.4(1.6) J compared to the non-HIP treated group of 19.8(1.8) J (Table 1). The fatigue strength of the samples HIP treated compared to the non-HIP treated group was 650 MPa and 396 MPa respectively (Table 1).

This study shows that the HIP treatment of DMLS Ti6Al4V diminishes some mechanical strengths while greatly improving the fatigue life of the material. As we continue to evaluate these “new” materials for orthopedic devices, these mechanical and physical properties will help us understand the capabilities of this process and material.


Hiromasa Mitsui Kazutaka Sugimoto Masamitsu Sakamoto

[Introduction]

In 1995, Muller reported on the improvement of metal-on-metal (MOM) bearing over the existing metal-on-polyethylene (MOP) articulations which demonstrated more rapid wear together with granulomatous foreign body reactions, damage of periarticular bony and soft tissues and associated expansile psoas bursal masses. He suggested that adequate lubrication together with improved material properties and manufacturing technologies would bring to the market a superior device with greater longevity. We wish to present our experience with a modern version of a MOM bearing.

[Material and Methods]

Between April 2008 and February 2012, we implanted 160 MOM THA with head diameters of 38–50 mm in 139 patients (21 males and 118 females). Their ages were 40–86 years (avg. 63.6 yrs). Follow up was 9 to 53 months post implantation (avg. 28 months). All implants were manufactured by one company (Wright Medical Technology, Arlington, TN, USA). The stems were of a standard titanium-aluminum alloy, either 45 ANCA-FIT or 115 PROFEMUR Z non-cemented stems. Acetabular components were all CONSERVE PLUS cobalt-chromium monoblock shells. Heads were also fabricated out of cobalt-chromium alloy, with modular junctions. Patients with complaints of groin pain and/or swelling or hip instability underwent MRI examination in order to detect the presence of fluid collections or soft tissue masses (Fig. 1 and 2). The statistical correlation between abnormal findings on MRI and age, gender, head diameter, component position and duration post-surgery was performed.


Hiroto Mitsui Hirotaka Iguchi Kaneaki Tawada Nobuyuki Watanabe Masahiro Nozaki Hideyuki Goto Yuko Nagaya Masaaki Kobayashi Takanobu Otsuka

This study shows the radiographic results of total hip arthroplasty (THA) using Revelation stem ® (Djo surgical USA) for hip joint disease.

We removed cases which we couldn't follow up, the remaining of the patients who had undergone a primary THA July 2007 to December 2009 in our institution using Revelation hip stem® and 58 cases-65 hips (14 men and 44 women) were possible for progress observation on this study, and radiographic evaluation was done at the time of the last observation. The preoperative diagnosis of the hip included osteoarthritis (OA) in 40 patients, idiopatic, necrosis of the hip in 13 patients, Rheumatoid arthritis (RA) in 4 patients, and femoral head fracture in 1 patient.

Three patients had undergone femoral head replacement (FHA) and 55 patients had undergone THA.

At the time of the last evaluation, spot welds were detected in 63 hips (97%) in zone1 and 7. Demarcation lines, which indicates movement of the stem, were detected in zone3,4,5, but not in the proximal of the stem.

Stress shielding were observed in 32 joints, according to Engh's classification, first degree were 27 joints and second degree were 5 joints. Cortical hypertrophy were detected in 13 joints.

The revelation stem features a lateral overhang structure (lateral flare) and the stem has an expanded proximal geometry allowing the device to rest on both medial and lateral cortices at the metaphyseal level. Above all the stem has anterior overhand structure (trapezoidal structure). The medullary cavity occupation rate is made to increase by these structures. Above all, the stability of the stem is increased by a proximal portion by three point support.

The distal stem is tapered and polished, which prevents the stress loading to a distal portion of the device.

Stress shielding more than the third degree is not detected, and spots welds were detected in the proximal of the stem. These facts indicate that the concept of this stem, transmit loading to the femur bone, at the proximal portion of the stem, would be achieved.


Young-Wan Moon Kang-Il Kim Seung-Beom Han ChoongHyeok Choi Myung Chul Lee Seong-Il Bin

Purpose:

To investigate treatment patterns and efficacy of postoperative strong opioids in patients who underwent total knee arthroplasty (TKA) in Korea

Methods:

A prospective, non-interventional study of 301 patients who underwent TKA and received strong opioids following patient controlled analgesia (PCA) was conducted by reviewing patient charts and diaries from 19 teaching hospitals. Clinical characteristics, strong opioid treatment patterns, efficacy of strong opioid on a scale of 0–10, and opioid-related adverse events (AEs) were investigated during hospitalization and at first outpatient visit. Safety analysis was conducted on 301 patients, and efficacy analysis was conducted on full analysis set (FAS) which consisted of all the patients who had at least 1 efficacy result among 301 patients.


Syam Morapudi Rui Zhou Yousef Khan Keith Barnes

Introduction:

The awareness of MoM hips in the general public, one would expect, to be good, given the media coverage. This study aims to look at the perceptions and knowledge of patients who have already got a MoM arthroplasty.

Methods:

All the patients who have had a MoM hip arthroplasty from Nov 2003 to the end of 2007 were identified from the database. Postal questionnaires were sent to all the patients, the responses received and analyzed. Those patients who had symptoms and those who fulfilled MHRA criteria were invited to a clinic for further surveillance.


Syam Morapudi Pter Ralte Keith Barnes

Introduction:

Intraoperative cell salvage involves the collection of blood directly from the operative field. The purpose of this study was to determine if its use reduces the need for postoperative allogenic blood transfusion, assess any adverse events and its effect on duration of postoperative stay in primary hip arthroplasty.

Patients and Methods:

We prospectively examined the effect of intraoperative cell salvage on the need for postoperative allogenic blood transfusion. Between February 2009 and August 2010, a total of 77 patients who underwent primary total hip arthroplasty were included in the study, under the care of the senior author (KB). All patients had a diagnosis of osteoarthritis.

Intraoperative cell salvage was used in 38 patients and not used in 39 patients. We prospectively collected data on patient demographics, ASA grade, preoperative and postoperative haematological features, number of units of packed red cells transfused and the volume of intraoperative reinfused cell salvaged blood. Total inpatient stay and any postoperative adverse events were recorded.


John Hollingdale Simon Mordecai Ajay Gupta

Patella resurfacing is becoming more routine in total knee replacements with recent reports indicating improved long term outcomes. Despite this, patella osteotomy relies heavily on how the cutting jig is applied rather than on fixed anatomical landmarks. Recognised complications of asymmetric patella resection are patella fractures, patella maltracking, bony impingement and pain. Accurate instruments have been developed for other aspects of total knee replacements. However cutting guides for the patella tend to be cumbersome with poor reproducibility.

Patella tilt is defined as the angle subtended by a line joining the medial and lateral edges of the patella and the horizontal. Keeping this angle to a minimum results in congruent alignment of the patella button within the trochlear groove. Current patella cutting jigs do not take this angle into consideration as they require full eversion of the patella laterally, not only making accurate placement of the jig difficult but also putting excessive strain on the surrounding soft tissue.

This study describes a new cutting technique for the patella osteotomy which is referenced off the distal femoral condyles ensuring a more accurate and reproducible cut without having to evert the patella.

With the femoral component trial in situ and the patella in its normal anatomical lie, the knee is flexed to 30°. The patella cutting jig is then applied in the usual manner making sure that adequate thickness of patella remains but it is placed parallel to a line joining the two condyles of the femoral component. By cutting the patella in this position parallel to the distal femoral condyles, patella tilt is minimised and the patella button will be aligned evenly within the trochlear groove.

Currently all patients requiring patella resurfacing at our institution are undergoing this technique and the short term results have been very promising.

This study presents a novel patella cutting technique that utilises a fixed landmark to ensure a more accurate and reproducible osteotomy. We are planning a large scale trial comparing pre- and post-operative knee scores and radiological assessment of patients having this new technique compared to standard cutting techniques. This will allow us to report on the longer term effects and pave the way for better patella resurfacing instrumentation.


Takkan Morishima Bastiaan Ginsel Godwin Choy Lance Wilson Sarah Whitehouse Ross Crawford

Introduction:

In an attempt to reduce stress shielding in the proximal femur multiple new shorter stem design have become available. We investigated the load to fracture of a new polished tapered cemented short stem in comparison to the conventional polished tapered Exeter stem.

Method:

A total of forty-two stems, twenty-one short stems and twenty-one conventional stems both with three different offsets were cemented in a composite sawbone model and loaded to fracture.


Khalaf Moussa

Introduction:

Total hip arthroplasty has became one of the most successful standard procedures in the orthopaedic surgery. With a more frequent use in young and active patients bone saving procedures become more important. On the other hand, the ever increasing trend toward minimal excision of the healthy bone during implantation of the total hip replacement has led to a range of implants that can be classified according their means of anchorage in the various anatomic segments. The Nanos-short-stem endoprothesis presented here requires metaphyseal anchorage.

Material and methods:

From juli 2005 to march 2009 a total of 112 (70 males, 52 female) uncemented Nanos-short-stem prothesis were implanted in 111 patients in Westpfalz academic hospital –University Mainz. The patiens average age was 53 years (33–73). The indication for this procedure was predominantly coxarthrosis. In all cases dorsal approach was used. The mean follow up period was 2,5 years (range 6 months–4,5 years). The patients were assessed using Harris Hip Score and radiologically to detect any bone changes, the stand of the prothesis and peri-articular ossifications.


Stephanie Muh Jonathan Streit John P Wanner Yousef Shishani Robert Nowinski Reuben Gobezie

Introduction

The treatment of glenohumeral arthritis in a young patient poses a significant challenge. Factors that affect decision making include higher activity levels, greater expectations, and concerns of implant longevity. Conflicting results have been reported in the literature. The purpose of this study is to report on our results for resurfacing of the humeral head combined with a biologic glenoid resurfacing using a soft tissue allograft for the treatment of glenohumeral osteoarthritis.

Methods

From 2003 to 2009 a retrospective multi-center review of 15 humeral and biologic glenoid resurfacing procedures with a mean age of 36.5 yrs. was performed. Indications for surgery included a diagnosis of glenohumeral arthritis non-responsive to conservative treatment. Exclusion criteria included major glenoid osseous deficiency, advanced rheumatoid arthritis, and chronic infection.


Satona Murakami Hirotaka Iguchi Masaaki Kobayashi Hiroto Mitsui Takanobu Otsuka

Introduction:

Obesity is one of the biggest issues to harm health so as increase medical costs worldwide. Unfortunately, Japan is no exception. Under a big governmental campaign, obese rate in Japanese elderly begins to decrease very recently. However, we cannot help to have impression that our patients who undergo hip/knee replacement surgery have been getting heavier and heavier. The purpose of this study is to examine the change of body mass in our patients and find related factors.

Patients and methods:

We reviewed hospital record of patients who underwent knee or hip replacement from January 1 to December 31 in 2004 or 2012. Patient who underwent either unicompartmental or total knee arthroplasty was included, however, those who went through femoral head replacement (hemiarthroplasty) was excluded from this study population. Body mass index (BMI) was calculated from body height and weight measured within a week before surgery. Unlike in United States, BMI greater than 25 is categorized as obese, and below 18.5 is considered underweight in Japan. Additionally, gender, age at surgery, operated site (hip or knee), primary surgery or revision, blood loss in operation, surgery time, anesthesia time were evaluated as co-factors.


Teruo Murakami Nobuo Sakai Tetsuo Yamaguchi Seido Yarimitsu Kazuhiro Nakashima Yoshinori Sawae Atsushi Suzuki

In joint prostheses using ultra-high molecular weight polyethylene (UHMWPE) as bearing material, wear problems are not yet completely solved under severe conditions in various daily activities, although efficacious treatments such as crosslinking, addition of vitamin E and the grafting of phospholipid polymer improved the wear properties. In contrast, in healthy natural synovial joints possessing articular cartilage as biphasic bearing material lubricated with synovial fluid, minimal wear with extremely low friction has been maintained for a whole life. Therefore, the joint prosthesis with artificial hydrogel cartilage with similar properties to articular cartilage is expected to show superior tribological functions with very low friction and infinitesimal wear if the appropriate lubrication mechanism is actualized. In this study, the effectiveness of biphasic lubrication mechanism in hydrogel through significant load support by fluid phase is evaluated in finite element (FE) analysis for reciprocating motion.

As biocompatible artificial hydrogel cartilage materials, two kinds of poly (vinyl alcohol) (PVA) hydrogels were prepared by the repeated freezing-thawing method and the cast-drying method, which are physically crosslinked with hydrogen bonding but different in structure and mechanical properties. To evaluate these time dependent behaviors of load-support ratio of fluid/solid phases and friction, two-dimensional biphasic FE analysis for cylindrical PVA hydrogel cartilage as 1.5 mm thick soft layer and radius of 5 mm was conducted under continuous loading of 0.2 N/mm by impermeable rigid plate in reciprocating motion in Fig. 1. The sliding speed is 4 mm/s for stroke of 8 mm at period of 4 s. A commercial package ABAQUS (6.8–4), which was appropriately evaluated for the biphasic FE analyses, was used in this study. The biphasic tissue was modeled by CPE4RP (four-node bilinear displacement and pore pressure, reduced integration with hour glass control) elements. The mechanical properties such as permeability, Young's modulus and Poisson ratio were estimated by curve fitting to stress relaxation behaviors in compression test.

As indicated in Fig. 2, it is worth noting that the cast-drying PVA shows significant interstitial fluid pressurization compared with a repeated freezing-thawing PVA hydrogel at 292 s after start-up, where coefficient of friction for solid-to-solid was assumed as 0.2. Changes in friction for PVA hydrogels in reciprocating motion were estimated as shown in Fig. 3. In spite of high friction (0.2) for solid-to-solid, cast-drying PVA brought the gradual decreasing in friction, probably due to rising of load-support ratio by fluid phase from initial 74% to 80%.

In human body, lubricating constituents in synovial fluids such as hyaluronic acid, proteins, glycoproteins and phospholipids can reduce the coefficient of friction for solid-to-solid. As suggested for low coefficient of friction for solid-to-solid as 0.01 in Fig. 3, rubbing friction is expected to be reduced to significantly low level.

As described above, the effective biphasic lubrication can sustain low friction level and minimal wear in synergistic action with soft-elastohydrodynamic lubrication, hydration lubrication and boundary lubrication as a similar mechanism to natural cartilage in various daily activities. These results indicate the usefulness of artificial hydrogel cartilage for longer durability in joint prostheses for clinical application.


Kohei Murase Sadami Tsutsumi Shinro Takai Nobuyuki Yoshino

The contact condition in the human knee joint must play important roles especially in dynamic loading situations where the loads transfer in the knee. In this study, the impact stress propagations through the inside of the knee joint were simulated using the three-dimensional finite element analysis (FEA). And the differences in the stress distribution were investigated between the intact knee and the total replacement condition.

The finite element (FE) models of an intact human knee joint and a total replaced knee joint were constructed with high shape fidelity. The intact model included the cortical bone, cancellous bone, articular cartilage, bone marrow, and meniscus. And the total replacement knee FE model, which is consisted of the artificial femoral and tibial components were also prepared to compare the impact propagations with the intact model (Figure 1). Impact load were applied to the proximal femur of the FE models under the same conditions as those of the weight-drop experiments with the knee joint specimens.

The FEA results showed that the impact stress propagated to the tibia through the knee joint for several milliseconds. The values and the time dependent change of the compressive strain on the cortical surface had good agreement with the experimental results. The compressive stress mainly propageted at the medial side, with 1.0 MPa at 1.2 milliseconds.

Especially, the impact stress propagated not only in the cortical surface area which has hard material property but also in the soft cancellous bone region inside the knee joint. The mass density of the cancellous bone has similar to that of the cortical bone, and thus the role of the load bearing in the cancellous area must be much increasing under the impact condition.

In the total replacement model, concentration of the impact compressive stress was observed with 2.8 MPa at the tibial region, while not under the normal intact conditions (Figure 2). Since the total replacement model is formed of different materials and the impact propagations were inhibited by the interfacial condition, such as sliding or debonding, it is considered that the contact condition between such materials have a great effect on the stress propagation.


Hirotsugu Muratsu Shinsuke Kirizuki Shinsuke Kihara Yoshiki Takeoka Tomoyuki Matsumoto Akihiro Maruo Hidetoshi Miya Ryosuke Kuroda Masahiro Kurosaka

[Introduction]

Rapid increase of aged population has been one of major issue affecting national health care plan in Japan. In 2006, Japanese Orthopaedic Association indicated a new clinical entity of musculoskeletal ambulation disorder symptom complex (MADS) to define the higher risk of fall and ambulatory disability in the elderly population caused by musculoskeletal disorders. Osteoarthritis of the knee is one of major cause of MADS. The number of patients with MADS underwent total knee arthroplasty (TKA) had been increased in Japan, and also expected to increase worldwide in the near future. The effectiveness of TKA for the patient with MADS would be a key issue for the patient satisfaction in TKA. In the present study, we analyzed the influence of pre-operative factors on the ambulatory functions in the patients of primary TKA.

[Material & Method]

132 patients with osteoarthritic knees implanted with posterior-stabilized (PS) TKAs were subjected to this study. There were 113 female and 19 male patients. The mean age of the patients was 73.6 years (range, 59 to 87 years). Patients were pre-operatively subjected to 2 functional performance tests which were essential tests for MADS diagnosis. Firstly, 3 meter timed up and go test (TUG) was used to evaluate ambulation ability. Secondary one leg standing time (ST) with open eyes was measured with both operated and non-operated leg to assess balancing ability. MADS was diagnosed if TUG and ST were not less than 11 seconds and/or less than 15 seconds respectively. The influence of each pre-operative factor was evaluated simple linear regression analysis (p < 0.05). Pre-operative factors consisted of age, sex, weight, height, BMI, standing femoro-tibial angle (FTA) and active knee range of motion.


Stephen Murphy William Murphy Jens H. Kowal

Introduction:

Conventional methods of aligning the acetabular component during hip arthroplasty and hip resurfacing often rely upon anatomic information available to the surgeon. Such anatomical information includes the transverse acetabular ligament and the locations of the pubis, ischium and ilium. The current study assesses the variation in orientation of the plane defined by the pubis, ischium and ilium on a patient-specific basis as measured by CT.

Methods:

To assess the reliability of anatomical landmarks in surgery, we assessed 54 hips in 51 patients (32 male, 22 female) who presented for CT-based surgical navigation of total hip arthroplasty. The HipSextant Research Application (version 1.0.7, Surgical Planning Associates Inc., Boston, Massachusetts) was used to perform the calculations. This application allows for determination of the Anterior Pelvic Plane coordinates from a 3D surface model. Standardized points on the ilium, ischium, and pubis were entered. These three points defined a plane and the orientation of the plane in the AP Plane coordinate system was calculated in degrees of operative anteversion and operative inclination according to the definitions of Murray1.


Stephen Murphy William Murphy Jens H. Kowal

Introduction:

Cup malposition in hip arthroplasty and hip resurfacing is associated with instability, accelerated wear, and the need for revision. A recent study measuring cup orientation on conventional radiodiographs demonstrated an incidence of cup malpositioning of 50% according to the safe zone that they defined1,2. A prior study of 105 conventionally placed cups using CT demonstrated a cup malpositioning incidence of 74%3. The current study similarly assesses the variation in cup position using conventional techniques as measured by CT.

Methods:

We have performed CT-based navigation of hip arthroplasty and revision arthroplasty on a routine basis since 2003 and also use CT imaging to quantify periprosthetic osteolysis. In our image database from these, we have identified 98 hips and y patients who had a previously conventionally-placed cup on CT imaging. For each hip, cup orientation was determined in operative anteversion and operative inclination (according to the definitions of Murray) using an application specific software application (HipSextant Research Application 1.0.7, Surgical Planning Associates Inc., Boston, Massachusetts). This application allows for determination of the Anterior Pelvic Plane coordinates from a 3D surface model. A multiplanar reconstruction module allows for creation of a plane parallel with the opening plane of the acetabulum and subsequent calculation of plane orientation in the AP Plane coordinate space.


Stephen Murphy William Murphy Jens H. Kowal

Background:

While more than ½ of acetabular components placed during hip arthroplasty are significantly malpositioned, traditional surgical navigation and robotoics have not been widely adopted. This may be due to the additional time, expense, and complexity associated with this technology. As an alternative, smart mechanical navigation instruments, adjusted on a patient-specific basis, have been introduced to address the problem of cup malorientation. The current study assesses the accuracy of acetabular component alignment using a mechanical navigation instrument.

Patients and Methods:

The acetabular component was aligned in 58 consecutive hips in 58 patients using the HipSextant Mechanical Navigation System (Surgical Planning Associates, Inc. Boston, MA). The technique involves using a patient-specific plan and associated software. In planning for surgery, CT data are used to create a 3D model and to define the anterior pelvic plane (APP). A patient-specific HipSextant docking coordinate system is then determined by three points: one just behind the posterior acetabular rim, a second on the lateral side of the ASIS, and a third on the surface of the ilium (Figure 1). The HipSextant itself has two adjustable orthogonal protractors (in-plane and off-plane angle) and two adjustable arms so that the instrument is adjusted for each patient based on their specific anatomy. The instrument docks directly to the pelvis so the recommended orientation of the acetabular component is based on the actual position of the pelvis at the time of component implantation. A direction indicator points in the direction of the planned cup orientation (Figure 2). Cup alignment was further enhanced with the use of a parallel guide to improve parallel visualization (Figure 3). Postoperative cup orientation was measured using a validated two-dimensional/three-dimensional matching method [3,5].


Ryuji Nagamine Chen Weijia Mitsugu Todo Shunji Hirokawa Keiichi Kondo Makoto Kawasaki Kei Osano

Purpose:

Differences in the sizes of femoral and tibial components between females and males, between osteoarthritis (OA) and rheumatoid arthritis (RA), and between measured bone resection and the gap control technique during TKA were assessed.

Method:

500 PS-TKAswith the Stryker NRG system in 408 cases were assessed. There were 83 male knees and 417 female knees, and 472 OA knees and 28 RA knees. This study was performed in Japan, and almost all OA knees had varus deformities. In each case, the sizes of the femoral and tibial components were measured on radiographs. The measured sizes represented those of the measured bone resection. TKA was performed by the gap control technique using a tensor/balancer with 30 inch-pounds expansion strength, and the sizes of the femoral and tibial components (used size) were recorded.


Yoshitaka Nakanishi Higaki Hidehiko Hiromasa Miura Yoshitaka Shiraishi Takeshi Shimoto Takatoshi Umeno Hiroshi Mizuta Yukihide Iwamoto

An ultra-high molecular weight polyethylene (UHMWPE) is widely used as bearing material in artificial joints, however, UHMWPE wear particles are considered to be a major factor in long-term osteolysis and loosening of implants. The wear particles activate macrophages, which release cytokines, stimulating osteoclasts, which results in bone resorption. The biological activity of the wear debris is dependent on the volume and size of the particles produced. Many researchers reported that the volume and size of particles were critical factors in macrophage activation, which particles in the size range of 0.1–1 mm being the most biological active.

To minimize the amount of wear of UHMWPE and to enlarge the size of UHMWPE wear particle, a nano-level surface textured on Co-Cr-Mo alloy as a counterface material was invented (Figure 1). Although the generally-used surface for a conventional artificial joint has 10 nm roughness (G-1), the nano-level surface has a superfine surface of 1 nm with groove and dimples against the bearing area. The existence probability of groove or dimples, and their surface waviness were adjusted (P-1, 2, 3, 4 and W-1, 2).

Pin-on-disc wear tester capable of multidirectional motions was used to verify that the nano-textured surface is the most appropriate for artificial joint. UHMWPE pin with an average molecular weight of 6.0 million was placed in contact with the disc and the contact pressure was 6.0 MPa. The disc and pin were lubricated by a water-based liquid containing the principal constituents of natural synovial fluid. Sliding speed of 12.12 mm/s had been applied for total sliding distance of 15 km.

The nano-textured surfaces reduced the amount of UHMWPE wear, this would ensure the long-term durability of artificial joint (Figure 2). The wear particles isolated from lubricating liquid were divided broadly into two categories; one is “simple type” and the other is “complicated type”. The lengths in a longitudinal direction (Ll) and its orthogonal direction (Ls) for each particles (>150) were measured, and the each aspect ratio (= Ll/Ls) was calculated. No significant difference was found in the ratio between simple type and complicated type, and in the distributions of aspect ratios. However, the distributions of Ll, which means the size of UHMWPE wear particle, were dramatically changed by using the nano-textured surface (Figure 3). These results suggest that the nano-textured surface does not change the morphological aspect of UHMWPE particle but enlarges the size of UHMWPE particle.

Cells (RAW264.7, blood, Mouse) were cultured with the particles in supplemented Dulbecco's modified Eagle's medium for 24 h in an atmosphere of 5% CO2 in air at 37 degrees C, and the quantitative PCR was performed for genetic expression of IL-6. The wear debris generated on the nano-textured surface inhibited the genetic expression of IL-6, which does not induce the tissue reaction and joint loosening.


Katsuya Nakata Makoto Kitada Keisuke Akiyama Hajime Owaki Takeshi Fuji

[Introduction]

Short tapered wedge-shaped cementless (TW) stems have been widely used for several years. The concept of fixation of TW stem is wedge-fit fixation in the proximal metaphysis. Developmental dysplasia of the hip (DDH) has anatomical abnormality, such as excessive femoral anteversion, short femoral neck length, narrow femoral cavity, or proximal-distal mismatching of the femoral canal. Therefore, Mismatching between stem and bone might be occurred in DDH. We evaluated intramedullary matching of short TW stem for DDH by three dimensional (3D) digital template in order to clarify whether mismatching between stem and bone is seen in DDH implanted short TW stem.

[Materials and Methods]

One hundred hips (92 patients) with DDH were performed preoperative simulation for total hip arthroplasty by 3D digital template system (ZedHip: Lexi, Tokyo, Japan). The average age was 63.5 years old. There were 12 males and 80 females. The average bone mass index was 21.5 kg/m2. Femoral canal shape was normal in 71, champagne-flute in 16 and stovepipe in 13 hips. Bone quality was classified into type A in 23, type B in 74 and type C in 3 hips. Preoperative computed tomography data were used for 3D digital template and reconstructed to 3D femoral model. Short TW stem (Taperloc Complete Microplasty: Biomet, Warsaw, IN) model constructed from computer-assisted design was matched to the reconstructed femoral model. Short TW stem model was in principle implanted according to the femoral neck anteversion with neutral alignment (varus and valgus < 2 degrees, flexion and extension < 2 degrees) at the coronal and sagittal plane of the femur. Stem size was determined in order to obtain the largest intramedullary matching at the coronal plane. Area of stem fitting with the cortical bone was investigated at 10 mm intervals above and below of mid minor trochanter. Intramedullary matching pattern was classified into proximal mediolateral metaphyseal fit, proximal flare fit and diaphyseal fit at multiple reconstructed planes of the 3D femoral model according to stem fitting area.


Satya Nambu Richard Obert Michael Roark Douglas Linton Scott Bible Jon Moseley

Introduction:

Modular necks allow intra-operative adjustment of neck length, offset, and version, enabling the surgeon to better match leg length and accommodate anatomical differences. However, there have been recent reports of early fatigue failures of the neck initiating from the neck/stem taper, and some retrieved components exhibit severe fretting corrosion.1 Fatigue testing according to ISO 7206-6 (10/9 orientation) has been shown to replicate the clinical fatigue failures, but results in relatively minor fretting and corrosion. The purpose of this pilot study was to evaluate techniques for accelerating fretting corrosion with the goal of replicating the most severely corroded clinical retrieval cases.

Methods:

Constructs tested in this study consisted of a single stem and neck design (PROFEMUR modular, Wright Medical Technology). The worst case long varus neck design was evaluated in two materials: Ti6Al4V and wrought CoCr. In vitro fatigue testing in the 10/9 configuration was conducted at 10 Hz in unbuffered, aerated saline. Fretting mass loss, distraction force, and assessment of taper corrosion via SEM/EDS were measured. Methods used to exacerbate fretting corrosion are shown in Figure 2.


Haitong Zeng Jaroslaw Karwowski Daniel Lawrynowicz Jim Nevelos

Introduction:

The purpose of this study was to evaluate the basic corrosion properties of conventional CoCr (ASTM F 1537, UNS R31537), Gas Atomized Dispersion Strengthened (GADS) CoCr (ASTM 1537, UNS R31539), Ti6Al4V ELI (ASTM F 136, UNS R56401) and Ti-12Mo-6Zr-2Fe (TMZF) (ASTM F 1813) alloys that are used in joint replacement applications.

Methods:

Test coupon samples made from alloys' wrought bar stocks were polished then tested. Each material had 4 groups (n33) that were tested in 4 aqueous solutions: 1) pH 7.4, 2) pH 5, 3) pH 2, and 4) pH 2 with 1 M of H2O2. Potential dynamic polarization was conducted using a Princeton Applied Research VMC Potentiostat, with an Ag/AgCl electrode as the reference electrode, and it resembled method in ASTM F 2129-08. The samples were evaluated with Scanning Electron Microscope (SEM).


Diana Nguyen Michelle Burgett Ian Clarke Thomas Halim Thomas Donaldson

Damage to metal-on-metal bearings (MOM) has been varyingly described as “edge wear,” third-body abrasive wear and “rim-damage” (1–4). However, no distinction has been made between any of these proposed wear mechanisms. The goal of this study was to discover what features might differentiate between surface damage created by either 2-body or 3-body wear mechanisms in MOM bearings. The hypotheses were that surface damage created by impingement of the cup rim (2-body wear) would be i) linear on the micro-scale, ii) reveal transverse striations (in direction of the sliding rim), iii) have either no raised lip or have a single lip along one side of the track, and iv) have an asymmetrical surface profile across the track width.

Five cases with 28 mm MOM, five of 34–38 mm MOM, and five of 50–56 mm diameter were studied (N = 15). The main wear zone (MWZ) was measured in each MOM head and the number of 2-body wear tracks recorded in the non-wear (NWZ) and main wear zone (MWZ). Bearing damage was examined using a white-light interferometer (Zygo Newview 600; 5x lens) and a scanning electron microscope (Zeiss MA15). The depths and slopes were assessed across the width of the damage tracks.

Thirteen of the 15 MOM bearings showed wear tracks that exhibited all four of the hypothesized 2-body wear characteristics. These wear tracks will be referred to as “micro-segments”. While micro-segments visually appeared linear, microscopically they revealed a semi-lunar edge coupled with transverse striations leading to a linear edge. This indicated that during impingement episodes, the cup rim ploughed material from the CoCr surface at the semi-lunar edge (Fig. 1), thereby creating the abruptly raised lip on the linear edge of the track. This “snow plough effect” and its distinct edge effect can account for the asymmetrical surface profile. A different type of 2-body wear was identified and referred to as “furrows”. Furrows also visually appeared linear visually, but microscopically revealed longitudinal striations and a symmetrical surface profile (Fig. 2). Furrows had lips raised on both sides of the track, but not circumscribing the terminal ends of the track. Instead, the ends of the furrows are tapered smooth transitions to the articular surface.

Thus, 2-body tracks were found to be distinguishable from 3-body tracks (micro-grooves) and were classified as either micro-segments or furrows. Micro-segements supported hypotheses 1–3 and provided a clearer definition for hypothesis-4, while furrows only supported hypothesis 1. The divergence in features between micro-segments and furrows allude to different interactions between the bearing and cup rim that led to each type of track. While these data represent a small set of cases (n = 15) this evidence shows for the first time what was previously only suspected (2), that the CoCr rim can routinely create 2-body wear damage mechanisms in MOM femoral heads.


Young-Kyun Lee Jae-Hwi Nho Kee-Haeng Lee Yong-Chan Ha Kyung-Hoi Koo

Background:

Two-stage reconstruction, reimplantation after removal of an infected prosthesis, has been considered to be the gold standard for treatment of infected hip arthroplasty. However, during the removal of a well-fixed femoral stem, the proximal femur can be damaged and a sequestrum can be formed, which might lead to chronic osteomyelitis and difficulty in reimplantation. We wanted to determine whether infection after hip arthroplasty can be treated without removal of a well-fixed stem.

Materials and Methods:

We treated 19 patients who had an infection after hip replacement, but a well-fixed cementless stem, with 2-stage reconstruction. At the first stage, we removed the acetabular cup, the liner and the head, but not the stem. We then implanted a cup of cement spacer. After control of infection, we reimplanted the acetabular component and head.


Masataka Nishikawa Hajime Owaki Takeshi Fuji

[Objective]

The objectives of this study are to measure the morphometric parameters of pre-operative distal femur in Japanese patients who received TKA, to investigate the differences in distal femoral anatomy between the genders, and to compare the measurements with the dimensions of femoral implants current used in Japan.

[Methods]

One-hundred seventy-nine Japanese patients who underwent TKA in Osaka Koseinenkin Hospital from April, 2009 to December, 2011 were included in this study. The genders and diagnoses were 25/ 154 patients (male/ female) and 143/ 36 patients [osteoarthritis (OA)/ rheumatoid arthritis (RA)], respectively. The mean age, height and body weight were 73.2 years, 152.2 cm and 56.7 kg, respectively. We measured the AP length, ML width, aspect ratio angle of distal femur. The measurement points on the medial condyle was 10 mm and on the lateral condyle was 8 mm from the lowest points of the medial and lateral posterior condyle to stimulate the optimal cutting thickness. We evaluated the relationship between AP length and ML width, or aspect ratio and ML width in diagnosis, alignment and gender. We also compared the measurements with the dimensions of femoral implants current used in Japan.

Continuous variables were assessed using the Mann-Whitney's U test. Relationship between AP length and ML width, or aspect ratio and ML width were assessed using simple regression analysis. Regression lines were assessed using analysis of covariance. For all tests, probability values (p values) of < 0.05 were considered to indicate statistical significance.


Naoya Nishinaka Hiroaki Tsutsui Taishi Uehara Takayuki Matsuhisa Takashi Atsumi

Objectives

Surgical treatment is standard for advanced osteochondritis dissecans (OCD) of the humeral capitellum. When cartilage is seen to be separated or completely detached, this fragment fixation is not usually applied. There have been reports of cases in which advanced OCD of the humeral capitellum progressed to osteoarthritis (Fig), particularly in cases which involved the lateral wall. In these cases, every attempt should be made to reconstruct the lateral wall to avoid osteoarthritis. In this study, we followed up cases with rib osteochondral autograft transplantation technique.

Methods

Subjects were 20 cases who were followed up until after they started pitching. The mean age was 13.8 years old and the mean observation period was 2 years and 6 months (from 7 months to 6 year 3 months). Kocher's approach was used to give a good access to the aspect of the radiohumeral joint. The majority of cases suffered from extensive OCD of the elbow. Detached fragment was removed (Fig. 2a) and graft from 5th or 6th rib with screw fixation was performed on 12 patients and 8 received fixation with no material (Fig. 2b). Follow-up assessment included the range of motion, start time of playing catch and throwing a ball with full power, sports activity, evaluation of radiography, a subjective (including Pain, Swelling, Locking/Catching and Sport activity) and objective (Flexion contracture, Pronation/Supination and sagittal arc of motion) modified elbow rating system by Timmeman et al. We also investigated the details of the arthroscopy observations and the 2nd arthroscopy findings for 4 cases.


Philip Noble Prem Ramkumar Chris Cookston Sabir Ismaily Jonathan Gold Charles Lawrie Kenneth Mathis

Introduction:

Malrotation of the tibial component is a common error in TKR, and has been frequently cited as the cause of clinical symptoms. Correct rotational orientation of the tibial tray is difficult to achieve because the resected surface of the tibia is internally rotated and is not symmetrical in shape. This suggests that anatomically contoured components may lead to improved rotational positioning.

This study was undertaken to test the hypotheses:

Use of an anatomically shaped tibial tray can reduce the prevalence of malrotation and cortical over-hang in TKA while increasing coverage of the resected tibial surface, and

Component shape has more influence on the results of surgical trainees compared to experienced surgeons.

Materials and Methods:

A standard symmetric design of tibial tray was developed from the profiles of 3 widely used contemporary trays. Corresponding asymmetric profiles were generated to match the average shape of the resected surface of the tibia based on a detailed morphometric analysis of anatomic data. Both designs were proportionally scaled to generate a set of 7 different sizes. Computer models of eight tibias were selected from a large anatomic collection. The proximal tibia was resected perpendicular to the canal axis with a posterior slope of 5 degrees at a depth of 5 mm (medial). Eleven experienced joint surgeons and twelve trainees individually determined the ideal size and placement of each tray on each of the 8 resected tibias. The rotational alignment, coverage of the resected bony surface, and extent of overhang of the tray beyond the cortical boundary were measured for each implantation. Differences in the parameters defining the implantations of the surgeons and trainees were evaluated statistically.


Kyle Borque Jonathan Gold Sabir Ismaily Rupal Patel Stephen Incavo Philip Noble

Purpose:

Knee pain and instability during high demand activities such as stair descent are reported by patients after TKA. Previous studies theorized that this pain is from increased demand on the quadriceps required to stabilize the femur on the tibia. In this study we explore the relationship between implant design, the posterior cruciate ligament (PCL), and AP stability of the knee during stair descent.

Methods:

CTs of 6 fresh-frozen human cadaveric knees (average age: 61 ± 6.5 years) with functioning cruciates were prepared. All specimens were mounted in a computer controlled, 6 DOF simulator programed to apply physiologic muscle loads and flexion/extension moments simulating the highest demand phase of stair descent (terminal swing to initial contact). A contemporary design of TKA was implanted in each specimen by an experienced surgeon. Testing was repeated after implantation of tibial inserts of the CR, CS with and without a PCL and PS designs.


Stuart Michnick Philip Noble Gauray Sharma Holly Adams Sabir Ismaily Robert Booth Kenneth Mathis

Introduction:

With the growing emphasis on the cost of medical care, there is renewed interest in the productivity and efficiency of surgical procedures. We have developed a method to systematically examine the efficiency of the surgical team during primary total knee replacement (TKR). In this report, we present data derived from a series of procedures performed by different joint surgeons. This data demonstrates a variation between the duration and efficiency of each step in this procedure and its relationship to the experience and coordination of the surgeon working with the scrub team.

Methods:

After consent was achieved, videotaped recordings were prepared of ten primary TKR procedures performed by five highly experienced joint surgeons. For quantitative analysis, each procedure was divided into 7 principal tasks from initial incision to wound closure. In order to quantify efficiency, we recorded the occurrence of events leading to delays in each step of the procedure (Table 1). Starting with a total score of 100 points, deductions were made, based on the number of delaying events and its impact on the efficiency of the procedure. A final score for the surgery was then determined using the individual scores from each principal task. The experience of each member of the surgical team in participating in TKR, and in working with the surgeon, were recorded and correlated with the total efficiency score for the entire procedure.


Philip Noble Maureen Dwyer Hugh Jones Richard E Field Joseph C McCarthy

Objectives:

Experimental disruption of the labrum has been shown to compromise its sealing function and alter cartilage lubrication. However, it is not known whether pathological changes to the labrum secondary to femoro-acetabular impingement (FAI) have a similar impact on labral function. This study was performed to determine the effect of natural labral damage secondary to abnormal femoral morphology on the labral seal.

Methods:

Ten intact hip specimens were obtained from male donors (47.8 ± 1.5 yrs) for use in this study. CT reconstructions demonstrated that 6 specimens were of normal morphology, while 4 displayed morphology typical of cam-FAI. Specimens were dissected free of the overlying soft tissue, leaving the capsule and labrum intact. Each specimen was potted and placed in a loading apparatus (0.5 BW). Pressures developed within the central and peripheral compartments were monitored with miniature pressure transducers. The sealing capacity of the labrum was measured by introducing fluid into the central compartment at a constant rate until transport was detected from the central to the peripheral compartment. These measurements were performed in 10 functional positions simulating sequential stages of gait, stooping, and pivoting. During testing, the 3D motion of the femoral head in the acetabulum was measured with motion analysis combined with computer visualization. Peak pressures were compared between specimens with and without labral damage for each of the three activities (p < 0.05).


Leslie Harrold Wenjun Li Allison Jeroan Philip Noble David Ayers Patricia Franklin

Introduction:

There is an increasing trend within the US for utilization of total knee replacement for patients who are still of working-age. Numerous causes have been suggested, ranging from greater participation in demanding sporting activities to the epidemic of obesity. A universal concern is that increased arthritis burden will lead to increased disabilty and unsustainable health-care costs both now and in the future with increasing rates of revision surgery in the years ahead. This raises the critical question: Are younger patients receiving knee replacement prematurely? To address this issue, we compared the severity of operative knee pain and functional status in younger versus older TKR patients, drawing upon a national research registry.

Methods:

A cohort of 3314 primary TKR patients was identified from the FORCE national research consortium from all surgeries performed between July 1st 2011 and March 30th 2012. This set of patients was derived from 120 contributing surgeons in 23 US states. Data characterizing each patient undergoing surgery was derived from patients, surgeons and hospitals, and included the SF 36 Physical Component Score (PCS), the Knee injury and Osteoarthritis Outcome Score (KOOS) and the Oswestry Low Back Pain Disability Questionnaire. WOMAC scores were also calculated from the KOOS data and transformed to a 0-to-100 scale with lower scores representing worse impairment. Using descriptive statistics, we compared the demographic and baseline characteristics of patients younger than 65 years of age (n = 1326) vs. those 65 years of age and older (n = 1988).


Philip Noble David Ayers Leslie Harrold Wenjun Li Allison Jeroan Patricia Franklin

Introduction:

Total knee replacement (TKR) and total hip replacement (THR) reliably relieve pain, restore function, and ensure mobility in patients with advanced joint arthritis; however these results are not uniform across all patient populations. Moreover, it is well established that knee replacement patients have outcomes inferior to those undergoing hip replacement procedures with lower rates of dissatisfaction with post-operative function and pain relief.

We compared baseline demographic and symptom profiles in patients from a US national cohort undergoing primary TKR and THR to determine whether differences in demographic make-up, pre-operative symptoms, or pre-existing co-morbidities might contribute to these differences observed post-operatively.

Methods:

A cohort of 2375 patients undergoing primary TKR and THR was identified from the FORCE national research consortium from all surgeries performed between July 1st 2011 and March 30th 2012. This set of patients was derived from 120 contributing surgeons in 23 US states. Gathered data included patient demographics, comorbidity (Charlson Comorbidity Index), operative joint pain severity (Western Ontario and McMaster Universities Arthritis Index (WOMAC)), physical function (SF-36; Physical Component Score (PCS)), emotional health (SF-36; Mental Component Score (MCS)), and musculoskeletal burden of illness (Hip and Knee Disability and Osteoarthritis Outcome Scores; Oswestry Disability Index). Using descriptive statistics, we compared the baseline demographic characteristics and symptom profiles of patients undergoing TKR (n = 1362) and those undergoing THR (n = 1013).


Hitoshi Nochi Satomi Abe Takuya Ruike Hiroshi Kobayashi Hiroshi Ito

Introduction:

The assumption that symmetric extension-flexion gaps improve the femoral condyle lift-off phenomenon and the patellofemoral joint congruity in total knee arthroplasty (TKA) is now widely accepted. For tease reasons, the balanced gap technique has been developed. However, the management of soft tissue balancing during surgery remains difficult and much is left to the surgeon's feel and experience. Furthermore, little is known about the differences of the soft-tissue stiffness (STS) of medial and lateral compartment in extension and flexion in the both cruciate ligaments sacrificed knee. It has a deep connection with the achievement of appropriate gaps operated according to the balanced gap technique. Therefore, the purpose of this study was to analyze the STS of individual compartment in vivo.

Materials and Methods:

The subjects presented 100 osteoarthritic knees with varus deformity underwent primary posterior stabilized (PS) – TKA (NexGen LPS-flex, Zimmer, Warsaw, USA). All subjects completed written informed consent. The patient population was composed of 14 men and 68 women with a mean age of 74.5 ± 7.5 years. The average height, weight, BMI, weight-bearing femorotibial mechanical angle (FTMA), the patella height (T/P ratio), extension and flexion angle of the knee under anesthesia were 151.9 ± 7.8 cm, 62.1 ± 9.4 kg, 26.9 ± 3.7 kg/m2, 167.7 ± 5.6 °, 0.91 ± 0.15 °, −12.0 ± 6.7° and 129.4 ± 13.8°, respectively. After finishing osteotomy and soft tissue balancing, the femoral trial prosthesis was fitted with patello-femoral joint reduction. Then, the medial and lateral compartment gaps (CG) were measured at various distraction forces (89–178 N) using a newly developed versatile tensor device at full extension and 90° flexion positioning, respectively. (Fig. 1) The STS (N/mm) was calculated from a load displacement curve generated by the intra-operative CG data and joint distraction force. Comparisons were made by Wilcoxon signed-ranks test. Correlations were analyzed with Pearson's correlation coefficient. Predictive variables were analyzed with Stepwise regression. A value of p < 0.05 was considered significant.


Hitoshi Nochi Satomi Abe Takuya Ruike Hiroshi Kobayashi Hiroshi Ito

Introduction:

Conventional understanding of knee kinematics suggests that the femoral component should be rotationally aligned parallel to the surgical epicondylar axis (SEA). In contrast, the balanced gap technique suggests the knee be balanced in extension and flexion to achieve proper kinematics and stability of the knee without reference to fixed bony landmarks. To investigate the functional flexion-extension axis (FFEA) when a balanced gap technique was used in the posterior-stabilized total knee arthroplasty (PS-TKA), the relationships between rotational alignment of the femoral component to the postoperative flexion gap balance and to the tibial mechanical axis were evaluated radiographically.

Materials and Methods:

In this prospective study, 63 consecutive knees in 50 patients were included with medial osteoarthritis undergoing a primary PS-TKA (NexGen LPS-Flex, fixed surface, Zimmer; Warsaw, USA). All subjects completed written informed consent. The patient population was composed of 8 men and 42 women with a mean age of 73.0 ± 7.7 years. The average height, weight, BMI, weight-bearing femorotibial mechanical angle (FTMA), condylar twist angle (CTA), and the patella height (T/P ratio) were 150.9 ± 7.2 cm, 62.3 ± 10.1 kg, 27.3 ± 4.0 kg/m2, 167.8 ± 5.5°, 5.9 ± 1.6° and 0.94 ± 0.15, respectively. All procedures were performed through a medial parapatellar approach and a balanced gap technique used a newly developed versatile tensor device. Pre- and post-operatively, the CTA was evaluated using computed tomography (CT). To assess the postoperative flexion gap balance, a condylar lift-off angle (LOA) was evaluated using the epicondylar view radiographs. The FTMA and coronal alignment of the tibial component in reference to the tibial mechanical axis (angle β) were evaluated using plain AP radiography. The FFEA (angle θ) of the knee was calculated as the following; (angle β) + (post-operative CTA) – (LOA). Correlations were analyzed with Pearson's correlation coefficient. Predictive variables were analyzed utilizing Stepwise regression. A value of p < 0.05 was considered significant.


Yasuhiro Ohmori Seiya Jingushi Tsutomu Kawano Moritoshi Itoman

Purpose:

In order to acquire good stability of an arthroplasty hip, the proper placement of the implants, which prevents impingement between the stem neck and the socket, is important. In general, the anteversion of the uncemented femoral stem depends on the relationship between the three-dimensional structure of the proximal femoral canal and the proximal stem geometry. The exact degree of the anteversion will be known just after broaching during the operation. If the stem anteversion could be forecasted, preoperative planning of the socket placement would be relatively easy. Furthermore, when a high degree of anteversion is forecasted, a special femoral stem to reduce it, such as a modular stem, could be prepared. However, we experienced that the preoperatively measured anteversion of the femoral neck using computer tomography (CT) was sometimes different from that of the stem measured during the operation. The purpose of this study was to investigate whether the preoperative measurement would be helpful to predict the stem anteversion by examining the relationship between the anteversion of the femoral neck and the stem.

Patients and methods:

A total of 57 primary THAs by one senior surgeon from April 2011 until March 2012 were carried out. Two THAs using a modular stem and one for the hip after previous proximal femoral osteotomy were excluded. The remaining 54 THAs were examined. The used uncemented stems were designed for proximal metaphyseal fixation. CT scans, including the distal femoral condyles as well as the hips, were carried out in all cases preoperatively. The anteversion of the femoral neck was measured as the angle of the maximum longitudinal line of the cross section of the femoral neck to the line connecting the posterior surfaces of both of the distal femoral condyles (Fig. 1). The femoral neck anteversion was measured at three levels (Fig. 1). The stem anteversion was measured just after the femoral broaching during the THA. The relationship between the anteversion angles of the femoral neck and of the stem was examined by using a regression analysis. The institutional review board approved this study.


Yoshiki Okada Hirosuke Endou Kazuo Fujiwara Yohei Kagawa

Background

The main factor of osteoarthritis (OA) of the hip in Japan is secondary due to developmental dislocation of the hip and hip dysplasia. For this reason, navigation is useful to treat complicated cases.

Purpose

We performed total hip arthroplasty (THA) for the secondary OA of the hip using paired point matching and fluoroscopic matching, and compared the accuracy between them.


Yukimasa Okada Shinichi Miyazawa Nobuhiro Abe

Introduction:

One of the complications occurring after total knee arthroplasty (TKA) is venous thromboembolism (VTE). The current screening techniques for VTE are venography, lower extremity vascular ultrasound, pulmonary scintigraphy, and contrast-enhanced computed tomography (CT). Although venography and lower extremity vascular ultrasound can detect deep venous thrombosis (DVT) in the lower extremities, pulmonary thrombosis poses a diagnostic problem. We performed contrast-enhanced CT screening for DVT and pulmonary embolism (PE) after TKA, and assessed the efficacy of the following prophylactics for VTE: fondaparinux, enoxaparin, and edoxaban.

Materials and Methods:

Subjects included 219 patients (260 knees) undergoing TKA at our hospital between April 2007 and November 2012. The 260 subject knees were divided as follows: group C, 31 cases in which DVT prophylactics were not used (April 2007 to October 2008); group F, 107 cases receiving fondaparinux 2.5 mg/day (July 2007 to October 2009); group ENO, 87 cases receiving enoxaparin 2000–4000 IU/day (November 2009 to October 2011); and group EDO, 35 cases receiving edoxaban 15–30 mg/day (November 2011 to November 2012). Contrast-enhanced CT images were obtained from the pulmonary apex to the foot for diagnosis of VTE. Groups were compared for incidence of symptomatic PE, asymptomatic PE, DVT-negative asymptomatic PE, DVT-positive asymptomatic PE, and DVT.


Michael Olsen Douglas Naudie Max Edwards Michael Sellan Richard W McCalden Emil Schemitsch

Introduction:

Alignment of the initial femoral guidewire is critical in avoiding technical errors that may increase the risk of failure of the femoral component. A novel alternative to conventional instrumentation for femoral guidewire insertion is a computed tomography (CT) based alignment guide. The aim of this study was to assess the accuracy of femoral component alignment using a CT-based, patient specific femoral alignment guide.

Methods:

Between March 2010 and January 2011, 25 hip resurfacings utilizing a CT-based femoral alignment guide were performed by three surgeons experienced in hip resurfacing. Stem-shaft angle (SSA) accuracy was assessed using minimum 6 week post-operative digital radiographs. A benchside study was also conducted utilizing six pairs of cadaveric femora. Each pair was divided randomly between a group utilizing firstly a conventional lateral pin jig followed by computer navigation and a group utilizing a CT-based custom jig. Guidewire placement accuracy for each alignment method was assessed using AP and lateral radiographs.


Zachary Morison Michael Olsen Akshay Mehra Emil Schemitsch

Purpose:

The use of computer navigation has been shown to improve the accuracy of femoral component placement compared to conventional instrumentation in hip resurfacing. Whether exposure to computer navigation improves accuracy when the procedure is subsequently performed with conventional instrumentation without navigation has not been explored. We examinedwhether femoral component alignment utilizing a conventional jig improves following experience with the use of imageless computer navigation for hip resurfacing.

Methods:

Between December 2004 and December 2008, 213 consecutive hip resurfacings were performed by a single surgeon. The first 17 (Cohort 1) and the last 9 (Cohort 2) hip resurfacings were performed using a conventional guidewire alignment jig. In 187 cases the femoral component was implanted using the imageless computer navigation. Cohorts 1 and 2 were compared for femoral component alignment accuracy.


Zachary Morison Michael Olsen Michael Donnolly Michael Blankstein Emil Schemitsch

The purpose of this study was to examine the utility of the acetabular component introducer as a tool to intra-operatively predict implant inclination in total hip arthroplasty. This study investigated (1) the correlation between intra-operative photographic assessment of cup inclination using the acetabular introducer and that measured on post-operative radiograph; and (2) the accuracy of intra-operative prediction of abduction angle.

For this study, we prospectively recruited 56 patients scheduled to receive primary hip arthroplasty from one of two senior surgeons. During the procedure, the lead surgeon provided a prediction of the abduction angle based on the alignment of the impactor attached to the cup in its final seated position. A standardized anteroposterior (AP) photograph was then taken of the acetabular impactor in situ. Abduction angles were measured by two observers on the photographs and post-operative AP pelvis radiographs. Linear regression was used to determine the correlation between the angle of the guide measured on the photographs and the actual position of the implant measured on the radiograph. Descriptive statistics were further used to analyze the accuracy of the intra-operative prediction as compared with the abduction angle measured on the photographs.

Measurements of cup position made from post-operative radiographs were significantly correlated with the measurements as assessed by intra-operative photographs (r = 0.34, p = 0.00). Our findings demonstrate that radiological abduction angles tend to be greater than that assessed by intra-operative photographs by a mean of 5.6 degrees (SD = 6.6 degrees; 95% CI = 7.3 to 3.9 degrees). Conversely, surgeon prediction of cup inclination based on the acetabular introducer differed from the radiographic measurements by a mean of 6.8 degrees (SD = 8.7 degrees). There was good agreement between the two observers in both photographic and radiographic measurement (k = 0.95, k = 0.96, respectively).

In conclusion, we found that the intra-operative photographic assessment of acetabular cup inclination by acetabular impactor alignment tends to underestimate the abduction angle by a mean of approximately 5 degrees. In addition, intra-operative surgeon estimation of acetabular inclination did not appear accurate in this study demonstrating that cup position should rely on additional visual cues beyond that captured in the anteroposterior view of the cup introducer.


Orhun Muratoglu Ebru Oral Andrew Neils Brinda Doshi

Introduction:

Irradiated ultra-high molecular weight polyethylene (UHMWPE), used in the fabrication of joint implants, has increased wear resistance [1]. But, increased crosslinking decreases the mechanical strength of the polymer [2], thus limiting the crosslinking to the surface is desirable. Here, we usedelectron beam irradiation with low energy electrons to limit the penetration of the radiation exposure and achieve surface cross-linking.

Methods:

Medical grade 0.1 wt% vitamin E blended UHMWPE (GUR1050) was consolidated and irradiated using an electron beam at 0.8 and 3 MeV to 150 kGy. Fourier Transform Infrared Spectroscopy (FTIR) was used from the surface along the depth at an average of 32 scans and a resolution of 4 cm−1. A transvinylene index (TVI) was calculated by normalizing the absorbance at 965 cm−1 (950–980 cm−1) against 1895 cm−1 (1850–1985 cm−1). TVI in irradiated UHMWPE is linearly correlated with the radiation received [3]. Vitamin E indices were calculated as the ratio of the area under 1265 cm−1 (1245–1275 cm−1) normalized by the same. Pin-on-disc (POD) wear testing was conducted on cylindrical pins (9 mm dia., 13 mm length, n = 3) as previously described at 2 Hz [4] for 1.2 million cycles (MC). Wear rate was measured as the linear regression of gravimetric weight change vs. number of cycles from 0.5 to 1.2 MC. Double notched IZOD impact testing was performed (63.5 × 12.7 × 6.35 mm) in accordance with ASTM F648. Cubes (1 cm) from 0.1 wt% blended and 150 kGy irradiated pucks (0.8 MeV) were soaked in vitamin E at 110°C for 1 hour followed by homogenization at 130°C for 48 hours.


Oner Tatar Harun Yasin Tuzun Kadir Ozturk Yusuf Emrah Eyi Huseyin Ozkan Yuksel Yurttas Cemil Yildiz Servet Tunay Mustafa Basbozkurt

Developmental hip displasia (DHD) still presents as an important problem in our country. Latency in diagnosis and inaccurate treatment causes seconder osteoarthritis in young adults and elder patients. Variable reconstructive surgical procedures as proximal femoral and acetabular osteotomies can be performed, but the most satisfactory functional results are achieved by total hip arthroplasty (THA). In this study, we analyzed the results of the cementless total hip arthroplasties performed in coxarthrosis secondary to developmental hip displasia. Between January 2006 and October 2009, 53 patients diagnosed with hip osteoarthritis secondary to DHD, whom performed 59 total hip arthroplasties in GATA Orthopaedics and Traumatology Clinic were included in the study. 10 of the patients were male (%19), and 43 of them were female (%81). Age of the patients varied between 29 and 78 years and the mean age was 48,7. In 23 patients (%44), THA procedure was performed at the right hip and in 24 patients (%45) at the left hip. 6 patients operadted bilaterally. All patients were followed up 8–38 months (mean 20, 6 months) with clinical and radiological evaluation. The hospitalization period varied between 7–14 days, mean 8,3 days. Posterolateral incision was used at all of the patients. Totally 10 (%17) complications were observed. 5 (%8,5) of them was intraoperative and 5(%8,5) was postoperative. Patients evaluated preoperatively and postoperatively with modified Harris Hip Score. While preoperative mean Harris score was 39,1, the postoperative mean score measured as 90,3. The results were excellent in 52 cases (%88,1), and very good in 7 cases (%11,9). Appropriate implementation of cementless total hip prosthesis in patients with hip osteoarthritis secondary to DHD, who have good bone quality and surgical indicaton; clinical and radiological short term results were satisfactory.


Fabrizio Pace Filippo Randelli Sara Favilla Carlo Zaolino Lorenzo Banci

Second-generation metal-on-metal bearings have been used since the late 1980s as alternative bearings to eliminate aseptic loosening due to polyethylene wear.

This study is the first with a long term follow-up for Meteasul, (Zimmer GmbH, Winterthur, Switzerland) metal on metal (MoM) hip replacement; in literature most of the studies have a mean follow-up of 7 years. Metasul showed better performances than other MoM couplings, with a low failure rate at long term follow-up and low revision rate for aspetic loosening.

The aim of the present study was to evaluate the long-term results of a series of Metasul implanted between January 1993 and July 1997. 145 cementless THAs with a 28 mm Metasul articulation were performed in 114 consecutive patients. Implant survivorship was calculated and clinical and radiographic evaluations were performed on 93 hips still available for follow-up at a mean of 19 years postoperatively (43 hips are dead or lost to FU, 29, 6%).

Nine hips (6.2%) were revised. The cumulative probability of survival of the overall implant at 19 years postoperatively with revision for any reason as the end point, was 0.937 (95% confidence interval, 0.888 to 0.985). The cumulative probability of survival of Metasul with revision for any reason as the end point, was 0.956 (95% confidence interval, 0.916 to 0.997).

Clinical outcome has been evaluated with modified Harris Hip Score for 93 hips with an average of 88.8 points.

Various degrees of radiolucencies and osteolysis were found proximally around the femoral components of 25 hips (20%).

Most of the patients has normal serum levels of metal ions (Co and Cr), and no cases of systemic toxicity has been reported.

Cementless Metasul THAs showed high probability of survival at 19 years postoperatively.


Douglas E Padgett Kirsten Stoner Nader Nassif Danyal Nawabi Timothy Wright Marci Elpers

Introduction:

Large diameter metal on metal total hip arthroplasty (MOM THA) have shorter lengths of implantation due to increased failure caused by wear either at the articulating surface as well as the taper-trunnion interface. Taper-trunnion wear may be worse in large diameter MOM THA due the increased torque at the taper-trunnion interface. However little has been done to understand how differences in taper-trunnion geometry and trunnion engagement effects wear. The purpose of this study was to (1) measure the differences in taper geometry and trunnion engagement on the head-taper of 11/13, 12/14, and Type 1 taper designs and (2) to determine if taper geometry affects fretting, corrosion, and wear at the taper interface.

Methods:

We identified 54 MOM THA primary revision implants with head diameters greater than 36 mm from our retrieval archive. Patients' charts were queried for demographic information and pre-revision radiographs were measured for cup inclination and cup anteversion. To measure taper geometry and wear the head tapers were imaged using Redlux©. The point clouds obtained from this were analyzed in Geomagic©. Taper angles and contact length where the trunnion engaged with the female taper of the head-tapers were measured. The diameter of the taper at the most distal visual area of trunnion engagement was also measured. Best fit cones were fit to the unworn regions to approximate the pristine surface. Differences between the raw data and the unworn surface were measured and volumetric wear rates were calculated. Fretting and corrosion of the head-taper was graded using the Goldberg Scoring.


Anna Panagiotidou Ben Bolland Jay Meswania John Skinner Fares Haddad Alister Hart Gordon Blunn

Introduction:

High failure rates with large diameter, metal on metal hip replacements have highlighted a potential issue with the head/stem taper junction as one of the significant sources of metal ion release. Postulated reasons as to why this may be such a problem with large head metal on metal hip replacements is due to the increased torque achieved by the larger head size. This may be responsible for applying greater micromotion between the head and stem taper and consequently greater amounts of fretting corrosion. The aim of this study was to perform short term in vitro electrochemical tests to assess the effect of increasing head diameter and torque on the fretting corrosion susceptibility of the head/stem taper interface and to investigate its effect on different material combinations.

Methods:

36 mm Cobalt Chrome (CoCr) femoral heads were coupled with either a CoCr or Titanium (Ti) stem with 12/14 tapers, all with a smooth surface finish. Increasing perpendicular horizontal offsets in the sagittal plane created incremental increases in torque. Offset increments of 0 mm, 5.4 mm and 7.5 mm were selected (Figure 1) to simulate the torque force equivalent to 9 Nm, 12 Nm and 17 Nm. An inverted hip replacement setup was used (ASTM F1875-98) (Figure 2). Components were statically loaded at 0 kN and 2.3 kN prior to sinusoidal cyclic loading and electrochemical testing. Mean & fretting currents were calculated every 50 cycles up to a maximum of 1000 cycles of sinusoidal cyclic loading at 3 Hz along with the Overall Mean Current (OMC), Overall Mean Fretting Current (OMFC) and Overall Current change (OCC).


Anna Panagiotidou Jay Meswania Jia Hua Sarah K Muirhead-Allwood John A. Skinner Alister Hart Gordon Blunn

Introduction:

There has been widespread concern regarding the adverse tissue reactions after metal-on-metal (MoM) total hip replacements (THR). Concerns have also been expressed with mechanical wear from micromotion and fretting corrosion at the head/stem taper junction in total hip replacements. In order to understand the interface mechanism a study was undertaken in order to investigate the effect of surface finish and contact area associated with modular tapers in total hip replacements with a single combination of materials of modular tapers.

Methods:

An inverted hip replacement setup was used (ASTM F1875-98). 28 mm Cobalt Chrome (CoCr) femoral heads were coupled with either full length (standard) or reduced length (mini) 12/14 Titanium (Ti) stem tapers. These Ti stem tapers had either a rough or smooth surface finish whilst all the head tapers had a smooth surface finish. Wear and corrosion of taper surfaces were compared after samples were sinusoidally loaded between 0.1 kN and 3.1 kN for 10 million cycles at 4 Hz. In test 1 rough mini stem tapers were compared with rough standard stem tapers whilst in test 2 rough mini stem tapers were compared with smooth mini stem tapers. Surface parameters and profiles were measured before and after testing. Electrochemical static and dynamic corrosion tests were performed between rough mini stem tapers and smooth mini stem tapers under loaded and non-loaded conditions.


Sang Eun Park Do Hyun Yeo

The first case was that of an 89-year-old woman with advanced dementia. After falling onto the left hip, she was admitted to the emergency room. Standard x-rays revealed an unstable intertrochanteric fracture. Closed reduction and internal fixation was performed using the long PFNA with a 105-mm helical blade, the second patient treated with this implant in our series. The operation was performed by an attending surgeon who was experienced with treatment of trochanteric fractures with intramedullary devices. Six weeks later the patient presented again with severe pain after she had fallen onto her left hip for a second time. Follow-up x-rays showed a perforation of the helical blade through the cortex of the femoral head after a shortening of the femoral neck by 2 cm. CCD angle was still 129 degrees, and there were no radiological signs of rotational displacement. The acetabular cartilage appeared intact. At her second operation, a replacement of the blade was performed using a shorter 95-mm implant. Postoperatively the patient was again mobilized under full weight bearing, and at 12 weeks follow-up, we found cut through again, we replaced hip with biopolar hemiarthroplasty.


Scott Banks Toshifumi Watanabe Stefan W Kreuzer Kevin Leffers Michael Conditt Jennifer Jones Brian Park Nicholas Dunbar Alex Iorgulescu

INTRODUCTION

There is strong current interest to provide reliable treatments for one- and two-compartment arthritis in the cruciate-ligament intact knee. An alternative to total knee arthroplasty is to resurface only the diseased compartments with discrete compartmental components. Placing multiple small implants into the knee presents a greater surgical challenge than total knee arthroplasty, and it is not certain natural knee mechanics can be maintained. The goal of this study was to compare functional kinematics in cruciate-intact knees with either medial unicondylar (mUKA), mUKA plus patellofemoral (mUKA+PF), or bi-unicondylar (biUNI) arthroplasty using discrete compartmental implants with preparation and placement assisted by haptic robotic technology.

METHODS

Nineteen patients with 21 knee arthroplasties consented to participate in an I.R.B. approved study of knee kinematics with a cruciate-retaining multicompartmental knee arthroplasty system. All subjects presented with knee OA, intact cruciate ligaments, and coronal deformity ranging from 7° varus to 4° valgus. All subjects received multicompartmental knee arthroplasty using haptic robotic-assisted bone preparation an average of 13 months (6–29 months) before the study. Eleven subjects received mUKA, five subjects received mUKA+PF, and five subjects received biUKA. Subjects averaged 62 years of age and had an average body mass index of 31. Combined Knee Society Pain/Function scores averaged 102 ± 28 preoperatively and 169 ± 26 at the time of study. Knee range of motion averaged −3° to 120° preoperatively and −1° to 129° at the time of the study.

Knee motions were recorded using video-fluoroscopy while subjects performed step-up/down, kneeling and lunging activities. The three-dimensional position and orientation of the implant components were determined using model-image registration techniques (Fig. 1). The AP locations of the medial and lateral condyles were determined by computing a distance map between the femoral condyles and the tibial articular surfaces.


Lowry Barnes Christopher Parks Marty Bushmiaer

PURPOSE:

Wright Medical has a long history of modular neck hip implants but had fracture issues with the original titanium necks. They subsequently changed to chrome cobalt modular necks. Direct contact between these dissimilar metal parts in the modular femoral component brings into consideration the possibility of similar adverse reactions of metal-on-metal articulations that have been previously described in other designs.

METHODS:

A retrospective review of 10 patients with Wright Medical chrome cobalt modular necks who were evaluated with chromium and cobalt metal ion levels as well as Metal Artifact Reduction Sequence (MARS) MRI's was performed. Pseudotumors were classified by MRI based on wall thickness, T1/T2 signal, shape, and location and given a corresponding type of I, II, or III. For each patient, symptoms or lack thereof were recorded, and time since surgery noted.


Megan Paulus Mark William Zawadsky Patrick Murray

Introduction:

The direct anterior approach for total hip arthroplasty has shown to improve multiple early outcome measures. However, criticisms suggest improved results may be due to selection bias and protocol changes. This study compares mini-incision posterior approach to direct anterior approach performed by one surgeon, controlling for influences other than the surgical approach itself.

Methods:

An IRB approved retrospective review was conducted on 150 consecutive primary total hip arthroplasty patients; the first 50 from mini-incision posterior approach, followed by 50 during the learning curve for direct anterior approach, and 50 subsequent cases when the approach was routine. Peri-operative protocols were alike for all groups. Data collection included patient demographics, anesthesia, operative times, discharge disposition, length of stay, VAS pain scores, progression from assistive devices, and narcotic use at follow-up of two and six weeks. Statistical methods included Wilcoxon rank sum, ANOVA, Kruskal-Wallis, chi-square, fisher exact and t-tests. P-value of <.05 was considered significant.


Loris Perticarini Matteo Ghiara Traiano Lamberti Francesco Maria Benazzo

INTRODUCTION

Managing severe periacetabular bone loss during revision total hip arthroplasty (THA) is a challenging task. Multiple treatment options have been described.

Delta Revision Trabecular Titanium™ (TT) cup is manufactured by Electron Beam Melting (EBM) technology that allows modulating cellular solid structures with an highly porous structure were conceived to rich the goals of high bone ingrowth and physiological load transfer. The caudal hook and fins ensure additional stability and the modular system allows the surgeon to treat bone defects in the most complex revisions. Entirely modular, the system can meet all intra-operative needs thanks to a customized implant construction.

The aim of this prospective study is to evaluate the short to mid-term clinical and radiographic outcomes of this acetabular revision cups.

MATERIALS AND METHODS

We prospectively assessed clinical and radiographic results of 31 cases of acetabular revisions that were performed from June 2007 and March 2012 by Delta TT Lima Revision system. The mean age of patients was 69.5 years (range 29–90).

The causes of revision were aseptic loosening in 22 cases (71.0%), periprosthetic acetabular fractures in 4 cases (13.0%), multiple dislocation of the primary implant in 3 cases (9.6%) and outcome of infection in 2 cases (6.4%). Stem revision was performed in 11 cases (35,4%). In 24 cases bone impaction grafting was used to fill cavitary defects (Paprosky 2B-3A); in 7 cases TT augments were used with the same aim. The average follow-up was 32 months (range 12–69).


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David Pienkowski Daniel Porter Marie-Claude Monier-Faugere Hartmut Malluche

Advances in the performance and longevity of total joint arthroplasty (TJA) have been enabled by related progress in implant materials, device designs, and surgical techniques. Successful TJA also depends upon adequate bone quality to provide an enduring mechanical foundation. Bone quality can be defined as the ability to repetitively withstand physiologically-relevant loads without excess deformation or fracture. It is now recognized that bone quality encompasses more than just material quantity, i.e. densitometrically-measured bone mass. Bone quality is also determined by: material composition and arrangement, cortical and cancellous structure, and extent of microdamage. These properties, together with the appropriate mass, confer bone with the biomechanical competence needed to meet the repetitive load-bearing demands imposed by total joint implants.

The need for TJA continues to increase in the aging global baby-boomer population. Unfortunately, this group is also experiencing increases in related comorbidities including: osteoporosis, kidney dysfunction, and diabetes, among others. Collectively these three comorbidities afflict more than 74 million Americans, and each is increasing at 2–8% annually. More importantly, each of these comorbidities negatively affects bone quality through alterations in bone turnover independent of bone mass changes commonly associated with these diseases. Specifically, alterations in bone turnover result in abnormal mineral-to-matrix ratios as measured by Fourier transform infra-red (FTIR) spectroscopy (Fig. 1) and altered Young's moduli (shape-independent resistance to deformation) as measured by nanoindentation (Fig. 2). These parameters are related to bones' fracture toughness and load-bearing capabilities, respectively. Also, low bone turnover is associated with mechanically important structural changes, i.e., decreased trabecular thickness (Fig. 3), cortical thickness and cancellous volume. Furthermore, low bone turnover may result in reducing the repair rate of physiologically – induced bone microdamage. This may lead to increases in the number or length of bone cracks, crack coalescence, and ultimately reduced energy needed for fracture.

Therefore, patients needing TJA who also have comorbidities associated with abnormal bone quality are at risk for inferior arthroplasty results. Recognition and treatment of the TJA-relevant biomechanical implications of these comorbidities may help improve outcomes.


Michael Kurdziel Brett Wiater James Moravek Daphne Pinkas J. Michael Wiater

Purpose:

Glenoid loosening persists as a common cause of anatomic total shoulder arthroplasty (TSA) failure. Considering radiographic evidence of loosening as an endpoint, TSA has a reported survivorship of only 51.5% at 10 years. Component loosening may be related to cementation and it is postulated that poor cement penetration and heat-induced necrosis may partially be responsible. There is a growing interest among surgeons to minimize or abandon cement fixation and rely on biologic fixation to the polyethylene for long-term fixation. De Wilde et al. reported promising early clinical and radiographic results using a pegged, all-polyethylene ingrowth glenoid design implanted without cement. The goal of this study was to compare glenoid micromotion in an all-polyethylene, centrally fluted pegged glenoid using 3 cement fixation techniques.

Materials and Methods:

Glenoid components (Anchor Peg Glenoid, Depuy Orthopaedics, Warsaw, IN, USA) (Figure 1) were implanted in polyurethane foam testing blocks with 3 different fixation methods (n = 5 per group). Group I glenoids were implanted with interference fit fixation with no added cement. Group II was implanted with a hybrid fixation, where only the peripheral pegs were cemented. Group III glenoids were fully cemented for implantation. Glenoid loosening was characterized according to ASTM Standard F-2028. The glenoid component and a 44 mm humeral head were mounted to a materials testing frame (858 Mini Bionix II, MTS Crop., Eden Prairie, MN, USA) with a 750N applied joint compressive force (Figure 1). A humeral head subluxation displacement of ± 0.5 mm was experimentally calculated as a value that simulates glenoid rim loading that may occur at higher load activities. For characterization of glenoid loosening, the humeral head was cycled 50,000 times along the superior-inferior glenoid axis, simulating approximately 5 years of device service. Glenoid distraction, compression, and superior-inferior glenoid migration were recorded with two differential variable reluctance transducers fixed to the glenoid prosthesis.


Brett Wiater James Moravek Daphne Pinkas Matthew Budge Denise Koueiter David Marcantonio J. Michael Wiater

Introduction:

Studies have demonstrated both clinical and radiological success of reverse shoulder arthroplasty (RTSA), with follow-up approaching 10-years. To date, most RTSA studies involve cemented fixation of the humeral components, and most involving uncemented RTSAs have used implants not necessarily designed for bony ingrowth. Cementless fixation utilizing proximally porous-coated (PPC) femoral implants has shown long term survivorship approaching 99% at greater than 10-years follow-up in total hip arthroplasty. Currently, the number of commercially available PPC RTSA implants is steadily growing, but there has been no published study examining clinical and radiographic outcomes in PPC, press-fit humeral stems. We hypothesized that the clinical and radiographic results of uncemented RTSA utilizing a PPC humeral stem would be similar to cemented RTSA stems when followed for at least 2-years.

Methods:

A prospective, IRB approved RTSA outcomes registry with 261 patients that underwent RTSA by one fellowship-trained orthopaedic surgeon between 2005 and 2008 was reviewed. Inclusion criteria were diagnosis of cuff tear arthropathy or severe rotator cuff deficiency refractory to all other treatments, and minimum 2-year clinical and radiographic follow-up. Exclusion criteria were proximal humeral fractures, glenohumeral instability, rheumatoid arthritis, incomplete follow-up, and revision arthroplasty. Outcome measures included active forward elevation (aFE), active external rotation (aER), active internal rotation (aIR), Constant-Murley score (CS), Subjective Shoulder Value (SSV), visual analogue scale (VAS) pain, and American Shoulder and Elbow Surgeons (ASES) score. Radiographs at 2 weeks, 3 months, 1 year, 2 years and yearly thereafter were evaluated for humeral component position, osteolysis, humeral component radiolucent lines (RLLs), stress shielding, and scapular notching. Statistical analysis was conducted by an independent institutional statistician.


David Porter Robert Urban Joshua J Jacobs Jose Rodriguez John Cooper

There is renewed concern surrounding the potential for corrosion at the modular head-neck junction to cause early failure in modern hip implants. Although taper corrosion involves a complex interplay of many factors, previous studies have correlated decreasing flexural rigidity of the femoral trunnion with an increased likelihood of corrosion at retrieval. A multicenter retrieval analysis of 85 modular femoral stems was performed to calculate the flexural rigidity of various femoral trunnions. Stems were implanted between 1991–2012 and retrieved between 2004–2012. There were 10 different taper designs from 16 manufacturers. Digital calipers were used to measure taper geometries by two independent observers. Mean flexural rigidity was 262 Nm2, however there was a wide range of values among the various stems spanning nearly an order of magnitude between the most flexible (80 Nm2) and most rigid (623 Nm2) trunnions, which was due in part to the taper geometry and in part to the material properties of the base alloy. There was a modest but significant negative correlation between flexural rigidity of the trunnion and release date of the stem. This wide variability in flexural rigidity may predispose particular stem designs to an increased risk of corrosion at the modular head-neck taper, and may in part explain why taper corrosion is being seen with increasing frequency in modern hip arthroplasty.


Aidin Eslam Pour Jean Yves Lazennec Adrien Brusson MA Rousseau

Introduction

The position and orientation of the lower extremities are fundamental for planning and follow-up imaging after arthroplasty and lower extremity osteotomy. But no studies have reported the reproducibility of measurements over time in the same patient, and experience shows variability of the results depending on the protocols for patient positioning. This study explores the reproducibility of measurements in the lower extremity with the patients in “comfortable standing position” by the EOS® imaging system.

Materials and Methods

Two whole-body acquisitions were performed in each of 40 patients who were evaluated for a spine pathology. The average interval between acquisitions was 15 months (4–35 months). Patients did not have severe spine pathology and did not undergo any surgery between acquisitions. The “comfortable standing position” is achieved without imposing on the patient any specific position of the lower limbs and pelvis. All the measurements were performed and compared in both 2- and 3-dimensional images. Distances between the centers of the femoral heads and between the centers of the knees and ankles were measured from the front. The profile is shown by the flexion angle between the axis of the femur (center of the femoral head and the top of the line Blumensaat) and the axis of the tibia.


David Putzer Debora Coraca-Huber Alexander Wurm Werner Schmoelz Michael Nogler

A cleaning process reduces the contamination risk in bone impaction grafting but also modifies the grain size distribution. The cleaned allograft shows a higher mechanical stability than the untreated group.

In revision total hip replacement, bone loss can be managed by impacting porous bone chips. The bone chips have to be compacted to guarantee sufficient mechanical strength. To improve the safety of bone grafts and to reduce the risk of bacterial and viral contamination, cleaning processes are used to remove the organic portion of the tissue while maintaining its mechanical characteristics.

A cleaning procedure described by Coraca-Huber et al. was compared to untreated allografts by performing a sieve analysis, followed by an uniaxial compression test. Differences in grain size distribution and weight loss during the cleaning procedure were compared to data from literature. Yield stress limits, flowability coefficients as well as initial density and density at the yield limit of the two groups were determined for each group over 30 measurements. The measurements were taken before and after compression with an impaction apparatus (dropped weight).

The cleaning process reduced the initial weight by 56%, which is comparable to the results of McKenna et. al. Cleaned allograft showed a 25% lower weight of bone chips sized > 4 mm compared to data from a previous study.

The cleaned bone chips showed a statistically significant (p > 0.01) higher yield limit to a compression force (0.165 ± 0.069 MPa) compared to untreated allograft after compaction (0.117 ± 0.062 MPa). The flowability coefficient was 0.024 for the cleaned allograft and 0.034 for the untreated allograft.

Initial density as well as the density at the yield limit was higher for the untreated allografts, as the sample weight was twice as high as in the cleaned group, to compensate for the washout of the organic portion. The cleaned bone grafts showed a higher compaction rate, which was 31%, compared the the untreated group with a compaction rate of 22%.

The cleaned allograft showed a higher compaction rate, which means that the gaps between the single grains are filled out with smaller particles, resulting in better interlocking. In the untreated allograft the interlocking mechanism is hindered by the organic elements. This observation is confirmed by a reduced flowabillity and a higher yield stress limit. The loss of weight as well as a higher compaction rate implies that more cleaned graft material is needed to fill bone defects in hip surgery. Sonication may damage the bone structure of the allograft and reduce the size of the particles.


R Qadir J. L Ochsner G. F Chimento M Meyer B Waddell J. M Zavatsky

Introduction

The utility of vancomycin powder application into the surgical site has recently shown efficacy in decreasing infections in patients undergoing thoracolumbar spine surgery. The effect on polyethylene wear after intraoperative placement of vancomycin powder at the surgical site of total joint replacements has not been determined. The purpose of this study is to compare wear behavior of material couples of Cobalt Chromium Alloy (CoCr) on ultra high molecular weight polyethylene (UHMWPE) to identical wear couples with vancomycin powder added prior to the start of wear simulation.

Methods

A custom-designed six-station wear simulator was used to establish in vitrowear characteristics of CoCr on UHMWPE on test articles fabricated from materials identical to total knee implants. Three stations included vancomycin powder added to the 36% bovine calf serum solution used in each station. Cyclic articulation simulations were run for 10 million cycles (Mc) at 4 ± 0.3 Hz under a constant axial load of 89N over 25 degrees of flexion-extension. UHMWPE wear was measured using photography, stereomicroscopic examination, and gravimetric measurements at the end of 0.5, 1, 2.5, 5, and 10 Mc.


Fernando Quevedo Gonzalez Natalia Nuno

INTRODUCTION

Porous metallic materials, due to their capability of tailoring their mechanical properties to those of bone, have been suggested to be utilized in prosthesis to avoid the stress shielding phenomenon1, believed to increase the risk of implant loosening2.

The aim of this work is to obtain the most simplified model possible to simulate the mechanical behavior of a Ti6Al4V porous structure. For this purpose, a beam element model was analyzed and the results were then compared to a 3D-solid model.

EXPERIMENTAL METHODS

Two computational models of the porous structure were developed: a 3D solid model, considered as the reference for comparison, and a beam model as a simplified and computationally inexpensive approximation (Fig. 1). CATIA V5R20 (3D modelling) and ANSYS V13 (simulations) were used.

Isotropic elastic material model was used. Strut diameter (ϕb) was set to 450 μm, pore diameter (ϕp) was varied between 600 and 5000 μm, and pore number (np) between 2 and 9. Structures sizes varied from 2.1 × 2.1 × 2.1 mm3 to 49.05 × 49.05 × 49.05 mm3. Apparent elastic modulus (Eap) and its difference between both models (error) were analyzed for the different values of ϕp and slenderness ratio (SR). In addition, the influence of loading direction was analyzed with the beam model for cubic and diamond cell geometries. Eap variations were compared.


Radu Racasan Leigh Fleming Paul Bills John Skinner Alister Hart Liam Blunt

Background

The changes in surface roughness occurring during the wear process at the bearing surface are of great importance in trying to understand the failure mechanism of large head metal-on-metal hip replacements. The aim of the study is to identify and characterise the areal surface parameter variation between the worn and unworn areas. Surface topography variations at the bearing surface have an effect on the lubrication regime [1]. In vitro tests of these components have suggested a “self-polishing” of the surface [2]. Traditionally Ra has been used as a descriptor of surface texture. Considering the high standard of manufacturing to which these components are produced, Ra is not sufficient to describe surface morphology which requires spatial information which can only be achieved through the use of areal parameters.

Methods

A total of 50 retrieved metal-on-metal hip replacements were assessed using white light scanning interferometry (Talysurf CCI, Ametek, UK) to determine the difference in the areal surface topography parameters between the worn and unworn regions of the bearing surface. The worn area was identified by use of a previously described method [3] to produce a wear map of the bearing surface, this allows the identification of the regions of interest. A series of six measurements were taken on each component (figure 1) comprising of: 2 measurements at the equator of the head representing the unworn region, one measurement at the pole and just off centre from the pole and the rest of the measurements were taken inside and at the boundary of the wear area. Each measurement covered an area of 1 mm2 therefore it is crucial that the location of the measurement be established as accurately as possible.

Data was analysed to determine the most relevant parameters that could be used to describe and highlight the changes in surface roughness that occur during the wear process.


Laura Yanoso-Scholl Lokesh Kumar Raja Jim Nevelos Jason Longaray Lizeth Herrera Gregg Schmidig Mayur Thakore

Introduction

Many tests have been published which measure frictional torque [1–4] in THR. However, different test procedures were used in those studies. The purpose of this study was to determine the effect of test setup on the measured friction torque values.

Methods

Specimen Description Table 1 lists tested study groups (n≥3). Metal-on-Metal specimens were custom designed and manufactured, and are not approved for clinical use. The remaining groups consisted of commercially available products (Stryker Orthopaedics, NJ).


Laura Yanoso-Scholl Lokesh Kumar Raja Gregg Schmidig Christopher Heffernan Mayur Thakore Jim Nevelos

Introduction

The femoral head/stem taper modular junction has several advantages; it also has the potential to result in fretting [1]. Stability of the taper junction is critical in reducing the risk associated with fretting. The purpose of this test was to measure the strength of various commercially available head-stem taper combinations under torsional loads to determine the effect of taper geometry and material on the strength of this taper junction.

Methods and Materials

CoCr femoral heads were tested with trunnions that were machined with both a large and small taper geometry, replicating commercially available stem taper designs, V40 (small) and C (large) (Table-1, Stryker Orthopaedics, NJ).

The femoral heads were assembled onto the trunnions with a 2 kN axial force. A multi-axis test frame (MTS Corp, MN) was used to test the head-trunnion combination by dynamically loading with a torque of ± 5Nm and a constant axial load of 2450N for 1000 cycles at 1.5 Hz (Figure 1). Samples were submerged in 25% diluted Alpha Calf Fraction Serum (Hyclone, UT). Upon completion of the dynamic test, a static torque to failure test was performed where the axial force of 2450N was maintained and the trunnion was rotated to 40° at a rate of 3°/sec.

The torque required to rotate the trunnion by 1° was determined for each specimen. Also, the torsional resistance, defined as change in torque/change in angle in the linear region of the torque-angular displacement data curve, was calculated for all the specimens. A limitation associated with the static test was that at 1° rotation it was difficult to differentiate between rotation of the trunnion inside the femoral head and physical twisting of the trunnion. Specimen groups were compared with a single-factor ANOVA test and a Tukey post hoc test at 95% confidence level.


Morteza Meftah Amar Ranawat Chitranjan S Ranawat

Introduction:

Jumbo cups (58 mm or larger diameter in females and 62 mm or larger diameter in males), theoretically have lowered the percentage of bleeding bone that is required for osseointegration in severe acetabular defects. The purpose of this study was to analyze the safety and efficacy of Tritanium jumbo cups in patients with major acetabular defects (Paprosky type IIIa and IIIb) and assess the extent of osseointegration.

Material and Methods:

From February 2007 and August 2010, 28 consecutive hips (26 patients, mean age of 69 years) underwent acetabular revision arthroplasty for treatment of Paprosky type IIIa and IIIb defects using Tritanium jumbo cups (Stryker, Mahwah, New Jersey).


Morteza Meftah Amar Ranawat Chitranjan S Ranawat

Introduction:

Non-cemented, porous-coated metaphyseal sleeves have been designed to improve biologic fixation and stability in revision total knee arthroplasty (TKA) with major bone defects. The aim of this study was to evaluate the clinical results and osteointegration of these sleeves in major bone loss.

Materials and Methods:

Between 2008 and 2011, 24 revision TKAs with major bone loss were reconstructed with non-cemented, porous-coated proximal sleeve (DePuy, Warsaw, IN). All patients were prospectively followed for a minimum of 2 years. Indications for use of sleeves were major metaphyseal tibial and femoral bone loss, younger age, and higher activity level. Osteointegration around the sleeves were classified as:

Grade 1: Complete osteointegration in all views without any demarcation.

Grade 2: Sleeves that are not completely osteointegrated but they are stable.

Grade 2A: Demarcation less than 2 mm on any view

Grade 2B: Demarcation more than 2 mm on any view

Grade 3: Sleeves that are not osteointegrated and unstable with evidence of subsidence.

Grade 3A: Subsidence less than 2 mm on any view

Grade 3B: Subsidence more than 2 mm on any view


Morteza Meftah Amar Ranawat Chitranjan S Ranawat

Introduction:

Hard-on-hard bearings and surface replacement (SR) have been used in young and active patients due to the reduced wear and lower rates of osteolysis. However, neither of these options resulted in survivorship higher than 90%–95% in this group of patients. The purpose of this prospective study was to compare minimum 10-year survivorship of non-cemented total hip arthroplasty (THA) using 28 mm metal head against highly-cross linked polyethylene (HXLPE) in our cohort as compared to published reports of other bearings, including surface replacements, in young-active patients.

Matierial and Methods:

From 1999 to 2003, 91 consecutive patients (112 hips; 57 males and 34 females) with average UCLA score of 8 and mean age 53 years (range 24–65 years), who received metal on HXLP (Crossfire), were included. At minimum 10-years follow-up, patients' clinical data was assessed. All level I, II studies, registry data, and prospective cohorts published in the literature with minimum 10 years of surface replacement (SR) and ceramic on ceramic (CoC) in young patients were included.


Fabrizio Pace Filippo Randelli Luca Serrao Lorenzo Banci

Introduction:

We present the mid-term results of our consecutive series of 155 hips treated with ASR XL Acetabular System (ASR-XL) for large-diameter metal-on-metal total hip arthroplasty and with DePuy ASR Hip Resurfacing System (ASR) for hip resurfacing.

Methods:

114 ASR-XL and 41 ASR were implanted between 2004 and 2008 in 145 patients (69 men and 76 women) with a mean age of 57 years. Twenty-one patients (23 hips) resulted lost to follow-up. All patients were recalled and monitored periodically with clinical, hematological and radiological evaluation. Average follow-up of the 155 hips was 72 months (1 to 104). The mean follow-up, excluding revised patients and those lost to follow-up, was up to 89 months.


Fabrizio Pace Filippo Randelli Luca Serrao Lorenzo Banci

Background

Previous studies have indicated poor outcomes and high complication rate in patients having revision of metal-on-metal (MoM) hip implants resulting from adverse local tissue reactions. Metal ions released by MoM bearings may potentially increase infection occurrence in patients with failed implants.

Questions/purposes

We reviewed all patients at our institution who sustained revision of a failed large-head metal-on-metal hip implant to determine if infection-related complications are associated with the elevation of serum metal ions concentration.


Parthiv Rathod Karl Orishimo Ian Kremenic Ajit Deshmukh Jose Rodriguez

Introduction:

Direct anterior approach (DAA) total hip arthroplasty (THA) has been reported to be a muscle sparing approach. The purpose of this study was to compare gait patterns over time between patients undergoing THA via DAA and posterior approach (PA).

Methods:

22 patients with unilateral primary hip osteoarthritis were prospectively enrolled and gait analysis was performed prior to, at 6 months and 1 year following THA via DAA and PA. All PA THA's were performed by a single surgeon from January 2008 to February 2009; all DAA THA's were performed by the same surgeon at the same institution from January 2010 to May 2011 with similar design of uncemented acetabular, femoral components and bearing surfaces. Reflective markers were placed on the lower extremity and motion data collected using six infrared cameras (Qtrac, Qualysis). Ground reaction forces were recorded with a multicomponent force plate (Kistler). A repeated-measures ANOVA was used to compare changes in gait parameters over time. Harris Hip Score was used to quantify pain and function.


Parthiv Rathod Ajit Deshmukh Jonathan Robinson John Stirton Jose Rodriguez

Introduction

Acetabular component position is an important determinant of stability, wear and impingement following total hip arthroplasty (THA). Its optimum position and size in direct anterior approach (DAA) THA has not been clearly described in previous studies. Our aim was to study the evolution of the same with reference to stability and impingement as a part of a single surgeon's learning curve.

Methods

Clinical and radiographic records of first 300 consecutive DAA THAs performed by a single surgeon from April 2009 to April 2011 were reviewed from a prospective database at a single center. Radiographic analysis was done by two observers to determine acetabular inclination and anteversion on 6 week postoperative standing radiographs. Native femoral head size, measured on preoperative radiographs after adjusting for magnification, was used to calculate the native acetabular cup size. The study population was divided into three groups; Group A– 1st 100 DAA THA cases, Group B – 2nd 100 and Group C – 3rd 100 corresponding to the use of intraoperative anterior stability assessment (Group B and C) and change in the cup size strategy (Group C). The incidence of instability and psoas impingement (PI) –related groin pain at 2 year follow-up was determined for the three groups. Statistical analysis was done to see if there were differences in these clinical and radiographic outcome measures in the three groups.


Joern Reinders Falko Von Stillfried Robert Sonntag Christian Heisel J. Philippe Kretzer

Background:

Total ankle replacements (TAR) are not as successful as total hip or total knee replacements. A three-time increased revision rate is reported in registry data [1]. Therefrom, wear associated revisions are frequent [2]. However, there is little knowledge about the wear behavior of TAR. This may be partly related to the fact, that currently no standard for wear testing of TAR exists.

The aim of this study is to define a biomechanical valid, force-controlled test specification for level walking of TAR.

Material and Methods:

Basic requirements for force-controlled testing of TAR is the definition joint flexion, as well as active forces and torques acting on the joint and the definition of the ligamental stabilization of the joint.

To specify flexion of the ankle, gait analysis was performed on patients treated with a TAR (HINTEGRA, Smith & Nephew) using skin mounted markers. Data about in-vivo forces is missing for TAR. Hence, determination of active forces and torques was based on mathematical models as described in the literature.

A new testing device (figure 1) has been developed to measure ligamental stabilization of the ankle joint. Measurements were performed on 10 paired cadaver feet (n = 20). Measurements were performed in different flexion angles when applying anterior-posterior forces (± 160N) and internal-external torques (± 2,5 Nm) between the talus and the tibia.


Joern Reinders Falko Von Stillfried Robert Sonntag Christian Heisel J. Philippe Kretzer

Background:

There is little knowledge about wear performance of total ankle arthroplasties (TAR). However, revisions rates are high for TAR [1] and wear associated revisions are frequent [2].

Therefore, the aim of this study is

To test the wear behavior of a TAR using a biomechanically valid testing scenario.

To test the influence of an alternative ceramic tibial component.

To test the long term wear performance of TAR.

Material and Methods:

In the first part of this study the HINTEGRA (Smith & Nephew) TAR has been used for wear testing. Wear testing was performed on a modified AMTI knee simulator. Level walking according to a previous described testing standard [see abstract: Development of a force controlled testing scenario for total ankle replacements] has been used. Level walking was simulated in three clinical relevant situations, first simulating the reduced loading after implantation, secondly simulating an increasing range of motion and at last a loading pattern orientating at the loadings in the native/healthy joint. Every simulation was run for 3 million cycles, resulting in 9 million total cycles.

In the second part of this study the metal tibial plateau was replaced by a ceramic tibial component (Biolox® Delta, CeramTec). Simulation was run, as described above, for additional 9 million cycles. Termed as a long term test, in total 18 million cycles of testing are performed.


Matthias Klotz Nicholas Beckmann Tobias Reiner Sebastian Jaeger Rudi Bitsch

In cases of poor bone quality intraoperative torque measurement might be an alternative to preoperative dual energy x-ray absorptiometry (DXA) to assess bone quality in Total Hip Arthroplasty (THA). 14 paired fresh frozen human femurs were included for trabecular peak torque measurement. We evaluated an existing intraoperative torque measurement method to assess bone quality and bone strength. We modified the approach to use this method in total hip arthroplasty (THA), which has not been published before. Since there are several approaches used in THA to exposure the hip joint, we decided to prefer the measurement in the femoral head which allows every surgeon to perform this measurement. Here a 6.5 × 23 mm blade was inserted into the proximal femur without harming the lateral cortical bone (figure 1). Further tests of the proximal femur evaluated the results of this new method: DXA, micro-computed tomography (μCT) and biomechanical load tests. Basic statistical analyses and multiple regressions were done. In the femoral head mean trabecular peak torque was 4.38 ± 1.86 Nm. These values showed a strong correlation with the values of the DXA, the μCT and the biomechanical load test. In comparison to the bone mineral density captured by DXA, the results of the intraoperative torque measurement showed a superior correlation with high sensitive bone quality evaluating methods (mechanical load tests and micro-computed tomography). Hence, the use of this intraoperative torque measurement seems to be more accurate in evaluating bone strength and bone quality than DXA during THA. The torque measurement provides sensitive information about the bone strength, which may affect the choice of implant in cases of poor bone stock and osteoporosis. In clinical use the surgeon may alter the prosthesis if the device indicates poor bone quality. Furthermore, we assume that the disadvantages associated with DXA scans like radiation exposure or errors caused by potential extraosteal sclerosis and interindividual soft-tissue artifacts could be excluded.


Richard Reitman John Vinciguerra

The clinical outcome and radiographic analysis of 82 patients undergoing total hip arthroplasty using a titanium acetabular component coated with a new proprietary Titanium Porous Coating inserted without cement are reported. All total hip replacements were performed by a single surgeon and utilized a porous coated, cementless femoral component. Pre clinical testing was carried out in an animal model to evaluate the new porous coating.

THR was performed using a cementless acetabular component of the same geometrical design inserted without cement. The component is coated with a new proprietary Titanium Porous Coating wherein the non-spherical bead itself is also porous. This creates a “lava rock” type of structure and gives variability in the pore sizes that aids in the in-growth and apposition of bone (fig 5). The inter-bead pore size: the pore size between each non-spherical bead = 200–525 μm while the Intra-bead pore size: the pore size within each non-spherical bead = 25–65 μm. The resulting surface is extremely rough and provides a robust initial “bite” or “stick” to the bone. Clinical results were evaluated using the Harris Hip score and were recorded prospectively preoperatively and at 6 weeks, 6 months, and 1 year postoperatively. Radiographs were evaluated for component migration, subsidence, and cortical and cancellous biologic response as well as zonal analysis of radiolucent lines, using the Muller THR template. Pre-clinical animal testing of the new porous coating was carried out in 50 sheep using a metacarpal intramedulary implant (similar to a hip stem) designed to function as a Percutaneous Osseointegrated Prosthesis (POP) for amputees and evaluated Apposition Bone Index (ABI) (fig 1), Mineral Apposition Rate (MAR) (fig 2),% Bone In-growth (fig 3), and Axial Pull-out Force (fig 4). Sheep were sacrificed at time points of 0, 3, 6, 9, and 12 months to measure and evaluate the above parameters.

Human clinical and radiographic follow up averaged 10.5 months (range 2–18 months). There were 39 females and 43 males. Average age was 59 years. The clinical results were excellent with respect to both pain and function at mid term follow up. Patient satisfaction was high. Radiographic analysis showed no migration or change in the angle of inclination at latest follow up. Femoral component subsidence was detected in 2 cases and averaged 1.8 mm. No polyethylene wear was detected. No hips dislocated. No hips underwent additional surgery. Pre-clinical test data demonstrated excellent mechanical and biological attributes. Average tensile strength of the coating surpassed the FDA minimum requirement by 3X. Animal testing in the sheep showed no evidence of stem loosening or need for revision after 12 months, and corroborated well with clinical results.

Correlation between the pre-clinical testing and the human experience was exceptional. Application of a new titanium porous coating utilizing a proprietary dual pore size structure to the surface of the acetabular component provides an extremely rough surface and robust initial fixation during cementless THR. Excellent early clinical and radiographic results are demonstrated. The addition of this new type of porous coating to other arthroplasty components may confer additional clinical advantages.


Jonathan Robinson Suresh Patil Parthiv Rathod Jose Rodriguez

Introduction:

Subsidence of cementless femoral stems in total hip arthroplasty (THA) has been associated with poor initial fixation and subsequent risk of aspectic loosening. There is limited literature on how subsidence of cementless, proximally porous coated, tapered wedge femoral stems impacts the patient clinically. The aim of our study was to assess whether subsidence with these stems is associated with a decline in clinical function.

Method:

A review of a prospectively collected database of THAs performed by a single surgeon at one institution using two cementless, tapered wedge stem designs from January 2006 to June 2010 was performed. Radiographic analysis using Picture Archiving and Communications System (PACS) was used to identify patients with greater than 1.5 mm of subsidence, and to document osseointegration. Preoperative and postoperative pain and Harris hip scores were recorded; and analyzed to identify if the clinical recovery pattern of the subsidence versus no subsidence groups differed. Protected weight bearing was recommended to all patients with subsidence.


Jonathan Robinson Parthiv Rathod John Stirton John Cooper Amar Ranawat Jose Rodriguez

The aim was to study the evolution of radiographic patterns of osteointegration of tapered wedge stems and determine if there is correlation with bony morphology and initial stem fit.

We reviewed primary total hip replacements performed by two surgeons using a single cementless tapered wedge design and that had a complete series of radiographs (defined as preoperative, 6 weeks, 1 year and 5 or more years).

Signs of bony remodeling were recorded at each Gruen zone. Calcar remodeling, changes in cortical thickness, evidence of subsidence and pedestal formation were recorded (Figure 1).

57 hips (50 patients) were available for analysis with a mean follow up of 5.03 years. Mean changes in cortical thickness were positive in zones 2(7.51) and 6(5.36) and negative in zones 1(−7.53) and 7(−13.51). Radiolucent lines were found in gruen zones 3,4(39%), and 5. Femoral neck cancellization was seen in zone 7 in 8 patients (14%) in year 1 and 36 (63%) by year 5.

Correlations were seen with proximal canal fill and radiolucent lines at zones 3 (0.278; p0.36) and 5 (0.258; p 0.05) and with distal canal fill and hypertrophy of the cortex in zone 3 (0.429; p0.001) and 5.

Cortical hypertrophy around the midstem, lack of radiolucent lines around the proximal stem and cancellization of the calcar are all radiographic patterns which occur routinely. A positive correlation with distal canal fill and hypertrophy of zones 3 and 5 was noted.

There was no significant correlation with preoperative boney morphology or initial stem fit proximally.


Christopher Roche Nick Stroud Matthew DiPaola Pierre Henri Flurin Joseph Zuckerman Thomas Wright

Introduction

Initial fixation of noncemented implants is critical to achieve a stable bone/implant interface during the first few months after surgery to potentiate bone in-growth and avoid aseptic loosening. Numerous reverse shoulder glenoid implant designs have been conceived in an attempt to improve implant performance and decrease the rate of aseptic glenoid loosening, commonly reported to be 5%. Design variations include: baseplate profile, baseplate size, backside geometry, center of rotation, surface finish and coatings, fixation screw diameters, number of fixation screw options, and type of screw fixation. However, little comparative biomechanical data exist to substantiate one design consideration over another. To that end, this study quantified glenoid fixation before and after cyclic loading of simulated abduction of 6 different reverse shoulder glenoid designs when secured to a low density polyurethane bone substitute block.

Methods

A displacement test quantified fixation of 6 different reverse shoulder designs: 38 mm Equinoxe standard offset (EQ), 38 mm Equinoxe lateral offset (EQL), 36 mm Depuy Delta III (DRS), 36 mm Zimmer, (ZRS), 32 mm neutral DJO RSP (DJO), and a 36 mm Tornier BIO-RSA (BIO), secured to a 0.24 g/cm3 polyurethane block as a shear (357 N) and compressive (50 N) load was applied before and after cyclic loading. (Figure 1) Glenoid displacement was measured relative to the block using dial indicators in the directions of the applied loads along the superior/inferior axis. A cyclic test rotated each glenosphere (n = 7 for each design) about a 55° arc of abduction at 0.5 Hz for 10k cycles as 750N was constantly applied. (Figure 2) Each implant was cycled using a 145° humeral liner of the appropriate diameter to ensure each device is subjected to the same shear load. A two-tailed unpaired student's t-test was used to compare pre- and post-cyclic mean displacements between designs; p < 0.05 denotes significance.


Leah Elson Kenneth A Gustke Gregory Golladay Martin Roche Christopher Anderson

Introduction

During primary total knee arthroplasty, the surgeon may encounter excessive medial collateral ligament tension while addressing a varus knee. This may be due to medial ligament/capsular complex contractures, and/or, due to the creation of a 0 degree mechanical axis in a varus knee. This tension leads to increased loading in the medial compartment, which contributes to an unbalanced extension and flexion gap. If uncorrected, this imbalance can lead to unfavorable clinical outcomes, including: pain, accelerated polyethylene degradation, joint instability, and limited ROM. Currently, intercompartmental soft-tissue balance is obtained by a subjective surgeon's “feel”. However, this method of judging soft-tissue tension is both variable and unreliable. Most surgeons can detect gross instability, but judging ligament tension is difficult. The following technique describes the integration of intraoperative microelectronic tibial inserts to assess and modify ligament tension, utilizing real-time dynamic sensor feedback

Methods

500 TKAs were performed between September 2012 and April 2013, by three collaborating surgeons. All surgeons used the same implant system, compatible with an embedded microelectronic tibial insert with which to receive real-time feedback of femoral contact points and joint kinetics. Intraoperative kinematic data, displayed loading patterns consistent with identifiable intercompartmental imbalance through a full ROM. All mediolateral imbalance, secondary to an excessively tight medial compartment, was addressed with the technique described herein.


Christopher Roche Phong Diep Matthew Hamilton Pierre Henri Flurin Joseph Zuckerman Howard Routman

Introduction

The inferior/medial shift in the center of rotation (CoR) associated with reverse shoulder arthroplasty (rTSA) shortens the anterior and posterior shoulder muscles; shortening of these muscles is one explanation for why rTSA often fails to restore active internal/external rotation. This study quantifies changes in muscle length from offsetting the humerus in the posterior/superior directions using an offset humeral tray/liner with rTSA during two motions: abduction and internal/external rotation. The offset and non-offset humeral tray/liner designs are compared to evaluate the null hypothesis that offsetting the humerus in the posterior/superior direction will not impact muscle length with rTSA.

Methods

A 3-D computer model was developed to simulate abduction and internal/external rotation for the normal shoulder, the non-offset reverse shoulder, and the posterior/superior offset reverse shoulder. Seven muscles were modeled as 3 lines from origin to insertion. Both offset and non-offset reverse shoulders were implanted at the same location along the inferior glenoid rim of the scapula in 20° of humeral retroversion. Muscle lengths were measured as the average of the 3 lines simulating each muscle and are presented as an average length over each arc of motion (0 to 65° abduction with a fixed scapula and 0 to 40° of internal/external rotation with the humerus in 0° abduction) relative to the normal shoulder.


Christopher Roche Phong Diep Matthew Hamilton Pierre Henri Flurin Joseph Zuckerman Howard Routman

Introduction

Reverse shoulder arthroplasty (rTSA) increases the deltoid abductor moment arm length to facilitate the restoration of arm elevation; however, rTSA is less effective at restoring external rotation. This analysis compares the muscle moment arms associated with two designs of rTSA humeral trays during two motions: abduction and internal/external rotation to evaluate the null hypothesis that offsetting the humerus in the posterior/superior direction will not impact muscle moment arms.

Methods

A 3-D computer model simulated abduction and internal/external rotation for the normal shoulder, the non-offset reverse shoulder, and the posterior/superior offset reverse shoulder. Four muscles were modeled as 3 lines from origin to insertion. Both offset and non-offset reverse shoulders were implanted at the same location along the inferior glenoid rim of the scapula in 20° of humeral retroversion. Abductor moment arms were calculated for each muscle from 0° to 140° humeral abduction in the scapular plan using a 1.8: 1 scapular rhythm. Rotation moment arms were calculated for each muscle from 30° internal to 60° external rotation with the arm in 30° abduction.


Leah Elson Kenneth A Gustke Gregory Golladay Martin Roche Patrick Meere Christopher Anderson

Introduction

Flexion instability of the knee accounts for, up to, 22% of reported revisions following TKA. It can present in the early post-operative phase or present— secondary to a rupture of the PCL— in the late post-operative phase. While most reports of instability occur in conjunction with cruciate retaining implants, instability in a posterior-stabilized knee is not uncommon. Due to the prevalence of revision due to instability, the purpose of constructing the following techniques is to utilize intraoperative sensors to quantify flexion gap stability.

Methods

500 posterior cruciate-retaining TKAs were performed between September 2012 and April 2013, by four collaborating surgeons. All surgeons used the same implant system, compatible with a microelectronic tibial insert with which to receive real-time feedback of femoral contact points and joint kinetics. Intraoperative kinematic data, as reported on-screen by the VERASENSE™ knee application, displayed similar loading patterns consistent with identifiable sagittal plane abnormalities. These abnormalities were classified as: “Balanced Flexion Gap,” “Flexion Instability” and “Tight Flexion Gap.” All abnormalities were addressed with the techniques described herein.


Parthiv Rathod Jose Rodriguez John Cooper

INTRODUCTION:

Short femoral stems are receiving increasing attention for less invasive total hip replacement (THR). The purpose of this study is to report our initial experience with a short modular femoral (SMF) stem at a minimum two-year follow up.

METHODS:

Twenty-six primary total hip arthroplasties (THAs) using the SMF stem were performed between August 2009 and January 2010. Patients were evaluated clinically with Harris Hip Score (HHS) and radiographically up to two years. Radiographs were analyzed to determine the degree of stem migration from its initial postoperative position. These parameters were compared to those of a cohort of 54 patients implanted with a monolithic tapered wedge stem from the same manufacturer over the same time period.


Lucas Rodriguez Danieli BC Rodrigues

Acrylic bone cements are used rather extensively in orthopedic and spinal applications. The incorporation of calcium phosphate additives to bone cements, to induce osteoconductivity, have typically resulted in increased cement viscosity, decreased handling, and detrimental effects of the mechanical performance of the cement. Additionally, bioactive bone cements are offered at a premium cost, which limits clinical use of these materials. The goal of this study was to examine and characterize an alternative two-solution poly (methyl Methacrylate) (PMMA) bone cement (referred to as TSBC), after incorporation of several calcium phosphate additives and antimicrobials. These bioactive and antimicrobial two-solution cements were designed to have adjustable properties that meet specific requirements of orthopedic applications. The addition of a bioactive agent would lead to increased levels of bone reformation after surgery, while an antibiotic within the cement would decrease the ability for pathogens to grow in the interface between the bone and new implant. TSBC is a pre-mixed bone cement that exhibits a combination of attractive properties including high strength, adjustable viscosity, adequate exothermal properties, as well as offering the possibility of using the same batch multiple times. The addition of antibiotics has not been previously explored in two-solution bone cements. Therefore, it is desirable to induce antibacterial activity with this formulation. Hydroxyapatite (Ca5(PO4)3(OH)), Brushite (CaHPO4•2H2O), and Tricalcium Phosphate (Ca3(PO4)2)(TCP) were incorporated into the TSBC in varying concentrations (25 and 50 wt%), and the rheological characteristics were examined to verify the feasibility of adding high concentrations of fillers to this cement formulation. Results demonstrated that unlike commercial powder-liquid formulations, calcium phosphate additives in TSBC do not detrimentally affect handling and the rheological properties of the material, while also providing maintenance of cement strength and other physical properties. TSBC material spends a dramatically increased amount of time in the swelling phase, as compared to powder-liquid formulations and thus is better suited to incorporate additives fully into its polymer matrix. Current two-solution bone cements do not contain any osteoconductive or antimicrobial agents. This study investigated the effects of addition of these bioactive agents in the physical and mechanical properties of the cement. Cement porosity was investigated to ensure that the porous nature of the bioactive cement does not damage the mechanical stability of the material. Further imaging will be conducted to demonstrate the improved osteointegration of these bioactive cement with osteoblasts (Figure 1). Degradation studies have been conducted to validate the biodegradable properties of the bioactive components and antibiotics release profile. It is further hypothesized that the degradation time will correlate to the antimicrobial activity. As the cement is replaced with natural bone, more and more antimicrobial will become exposed to the physiologic environment causing a continuous antimicrobial release as the material is partially replaced with new bone over time. Antimicrobial effectiveness and antimicrobial release studies are under-way to illustrate the cements ability to restrict growth at the cement surface, as well as show the antimicrobial release profile over time.


Jason Rogers Lowry Barnes

Postoperative stiffness is a relatively uncommon issue in total knee arthroplasty (TKA). However, it can be a debilitating complication when it occurs. Manipulation under anesthesia (MUA) is commonly used as the primary treatment modality following failed physiotherapy. The ADVANCE® Medial Pivot Knee (Wright Medical Technology) was created in an effort to prevent stiffness postoperatively and increase range of motion. The EVOLUTION® Medial Pivot Knee is a second generation design that builds upon the technology of the ADVANCE® knee. We performed a retrospective review of prospectively collected data on 881 primary medial pivot knees (592 ADVANCE® knees, 289 EVOLUTION® knees). We theorized that the design changes made to the EVOLUTION® knees might contribute toward reducing the need for MUA. We found that the EVOLUTION® knees required significantly fewer manipulations under anesthesia (p = 0.036). The design modifications made to the EVOLUTION® knees may have contributed to the lower rate of MUA.


Michael Ron Thies Wuestemann

INTRODUCTION:

Recreating the natural head center of the hip joint during hip arthroplasty is important for restoring biomechanics in order to minimize leg length discrepancies, improve soft-tissue tension, and mitigate impingement [1,2]. New tools have been developed that allow anatomical measurements and analysis of three-dimensional digital femura geometry based on CT scans [3]. The purpose of this study is to analyze the head center location of various fit-and-fill hip stem designs in relation to the natural bone head center location using a novel technique.

METHODS:

556 computer tomography (CT) images (SOMA™) of left femora were used in this study. The acetate templates of five fit-and-fill stem designs (Design 1: Secur-Fit Advanced, Stryker; Design 2: Secur-Fit Max, Stryker; Design 3: Summit, Depuy; Design 4: Synergy, Smith & Nephew; Design 5: Zimmer, VerSys Epoch FullCoat) were compared to each other to correlate stem sizes between different systems. The appropriate stem body size for each of the CT bones was established based on the medial offset of the bone 20 mm above the lesser trochanter (MO+20) and the stem medial offset at the medial resection point. Utilizing the commercially available offset heads for each design, the bone head centers and the stem head centers were plotted, aligning the central axis of the bone/stem as well as the MO+20 of the bone with the stem medial resection point. The percent of bone head centers within 1,2,3,4,&5 mm of a stem/head offset data point was calculated for all designs. Additionally, the distance from the bone head center to the closest stem/head offset data point and the average head offset used were calculated.


Lennert Ruiter Dennis Janssen Adam Briscoe Nico Verdonschot

Introduction

Current clinical practice in total knee arthroplasty (TKA) is largely based on metal on polyethylene bearing couples. A potential adverse effect of the stiff metal femoral component is stress shielding, leading to loss of bone stock, periprosthetic bone fractures and eventually aseptic loosening of the component. The use of a polymer femoral component may address this problem. However, a more flexible material may also have consequences for the fixation of the femoral component. Concerns are raised about its expected potential to introduce local stress peaks on the interface.

The objective of this study was to analyze the effect of using a polyether-etherketone (PEEK-Optima®) femoral component on the cement-implant interface. We analyzed the interface stress distribution occurring during normal gait, and compared this to results of a standard CoCr component.

Materials and methods

An FEA model was created, consisting of a femoral component cemented onto a femur, and a polyethylene tibial component. A standard loading regime was applied mimicking an adapted gait cycle, according to ISO14243-1. The implant-cement interface was modelled as a zero-thickness layer connecting the implant to the cement layer. Femoral flexion/extension was prescribed for the femur in a displacement controlled manner, while the joint loads were applied to pivoting nodes attached to the tibial construct, consistent with the ISO standard. Implant-cement interface properties were adopted from a previous study on CoCr interface debonding[1].


Alessandro Russo Michele Bianchi Nicola Lopomo Maria Cristina Maltarello Alessandro Ortolani Maurilio Marcacci

Introduction

When osteoarthritis occurs, joint replacement is the most frequent treatment. Currently, the mean survival rate for total joint arthroplasty is ∼90% after 10 years: the main reason for long-term implant failure, that generally required a revision surgery, are osteolysis and aseptic loosening of the implant, which are strongly correlated with wear debris formation from the UHMWPE insert [Ingham, 2005], as a consequence of the cyclic loading against the metallic or ceramic counterface [Dumbleton, 2002]. Wear debris bring to chronic inflammation of periprosthetic tissues causing an increase of bone reabsorption that finally provoke aseptic loosening, so implant failure[Holt, 2007]. Different solutions were proposed to reduce wear debris production but agreement has not been achieved yet. Our challenging approach prefigures the direct coating of the plastic component with a hard and well-adherent ceramic film, in order to drastically reduce wear debris formation from the plastic substrate while preserving its well-established bulk mechanical properties, especially under high local loads [Bianchi, 2013].

Methods

3%yttria-stabilized zirconia films were deposited by PPD technique. PPD is a new vapour deposition technique based on the ablation of a target material as a consequence of the impact of a high-energy electron beam. The plasma plume of ablated material is directed toward and deposited onto the substrate. Films were characterized by SEM-EDX, X-ray diffraction, nanoindentation, adhesion and tribological tests. Moreover, capability of ZrO2–UHMWPE system of carrying local loads – i.e. an estimation of the resistance to a third-body abrasion – was investigated.


Vani Sabesan Mark Callanan Vinay Sharma

Background

Total shoulder arthroplasty is technically demanding in regards to implantation of the glenoid component, especially in the setting of increased glenoid deformity and posterior glenoid wear. Augmented glenoid implants are an important and innovative option; however, there is little evidence accessible to surgeons to guide in the selection of the appropriate size augmented glenoid.

Methods

Solid computer models of a commercially available augmented glenoid components (+3, +5, +7) contained within the software allowed for placement of the best fit glenoid component within the 3D reconstruct of each patient's scapula. Peg perforation, amount of bone reamed and amount of medialization were recorded for each augment size.


Vani Sabesan Mark Callanan Vinay Sharma George Ghareeb Jim Moravek J. Michael Wiater

Background

There has been increased focus on understanding the risk factors associated with scapular notching in reverse shoulder arthroplasty (RSA). The purpose of this study is to evaluate the effect of scapular morphology and surgical technique on the occurrence of scapular notching using the notching index as a comprehensive predictive tool.

Methods

Ninety-one patients treated with a primary RSA were followed for a minimum of 24 months. Using a previously published notching index formula ((PSNA × 0.13) + (PGRD)), a notching index value for all patients was calculated. Radiographic assessment of patients were grouped by Nerot grade of scapular notching, group mean differences for prosthetic scapular neck angle (PSNA), peg glenoid rim distance (PGRD), preoperative scapular neck angle (SNA), notching index and clinical outcomes were compared.


Kengo Harato Aiko Sakurai Yutaka Kudo

Introduction

Total knee arthroplasty (TKA) has traditionally been performed as an effective treatment for patients with end-stage knee OA, by relieving pain, restoring function, and correcting deformity. One-leg standing (OLS) test is a widely used clinical tool to evaluate postural steadiness in a standing position for elderly people. According to previous reports, one-leg standing time was associated with subjects' age, self-assessment of their health status, body mass index, mortality, and the risk of falls. Therefore, it is important to know knee condition including OLS in older patients with knee OA. However, it is unknown whether TKA will be really beneficial for OLS in the elderly people.

It was hypothesized that postoperative recovery would be more slowly in older patients than in younger patients. Our purpose was to investigate factors affecting the OLS time in patients with end-stage knee OA and to clarify an age-related recovery process following TKA in the early postoperative period.

Methods

A total of 80 knees in 40 patients (35 females and 5 males) were enrolled in the current investigation. Mean age was 75 (60–82) years old. All the patients had bilateral varus deformities with radiographic OA of grade 4 severities, according to Kellgren-Lawrence grade. All the patients were divided into 2 Groups; patients older than 76 years (Group O) and younger than 75 years (Group Y). After unilateral TKA using Balanced Knee System®, posterior stabilized design (Ortho Development, Draper, UT), postoperative evaluations including OLS time, knee flexion angle during standing (KFA), and Visual Analogue Scale (VAS), were done preoperatively and daily from postoperative day 3 to 20 in each group, because epidural catheter was removed on postoperative day 2.

As a statistical analysis, values of preoperative measurements were used as controls in each group. Statistical difference between the data was evaluated using two-tailed repeated-measures of analysis of variance (ANOVA). After a significant P value (< 0.05) was determined, a post hoc Dunnett test was performed to compare selected mean values, and P-values of < 0.05 was considered as significant.


Anas Saleh Bishoy Gad Carlos Higuera Alison Klika Joseph Iannotti Wael Barsoum

Background:

Acetabular component malpositioning in total hip arthroplasty increases the risk of dislocations, impingement, and long-term component wear. The purpose of this Sawbones study was to define the efficacy of a novel acetabular imprinting device (AID) with 3D preoperative planning in accurately placing the acetabular component.

Methods:

Four surgeons performed the study on osteoarthritic and dysplastic Sawbone models using 3 different methods for placing the acetabular component (total n = 24). The 3 methods included (1) standard preoperative planning and instrumentation (i.e., standard method), (2) 3D computed tomographic (CT) scan planning and standard instrumentation (i.e., 3D planning method), and (3) 3D CT scan planning combined with an acetabular imprinting device (i.e., AID method). In the AID method, 3D planning software was used to virtually place the acetabular component at 40° of inclination and 22° of anteversion and create a parallel guide pin trajectory. A patient-specific surrogate bone model with a built-in guide pin trajectory was then manufactured as a stereoltihography device (Fig. 1A). The surgeon molded bone cement into the acetabulum imprinting the acetabular features while maintaining the guide pin trajectory (Fig. 1B). Afterward, the AID was removed from the surrogate bone model and placed onto the Sawbone, ensuring a secure fit (Fig. 1C). A guide pin was drilled into the Sawbone along the prescribed trajectory. With the guide pin in place, the surgeon could ream the acetabulum and impact the acetabular component using the guide pin as a visual aid (Fig. 1D). Postoperatively, a CT scan was used to define and compare the actual implant location with the preoperative plan. Statistical analysis was performed as 3 group comparisons using the chi-squared test for categorical data and analysis of variance (ANOVA) for continuous measurements.


Buster Sandgren

Introduction:

Conventional radiographic images are the gold standard method for postoperative evaluation of uncemented cups in patients with total hip arthroplasty. A conventional radiographic image of the pelvis gives a radiation dose of 0.7 mSv. Normally two images are needed. At present, dual energy CT is becoming more accessible in clinical practice and could allow lower radiation dose.

Aim:

We wanted to assess what radiation dose was possible without sacrificing image resolution.


Alejandro Espinoza Orias Yasunori Saruta Junichi Mizuno Tomonori Yamaguchi Masaki Mizuno Nozomu Inoue

INTRODUCTION:

As a consequence from cervical arthroplasty, spine structural stiffness, loading and kinematics are changed, resulting in issues like adjacent segment degeneration and altered range of motion. However, complex anatomical structures and lack of adequate precision to study the facet joint (FJ) segmental motion in 3D have prevented proper quantitative analyses. In the current study, we investigate the innovative use of a local coordinate system on the surface of the superior articular process of the caudal vertebral body in order to analyze FJ segmental motion using CT-based 3D vertebral models in flexion/extension.

METHODS:

CT images were obtained from six patients (2F/4M, mean age: 53 y.o.) with cervical degenerative disc disease in neutral, flexion and extension positions. CT data was used to create subject-specific surface mesh models of each vertebral body. From these, mean normal vectors were calculated for all FJ surfaces and posterior walls from C3/4 down to C6/7 (Fig. 1). The global coordinate system (x, y, z) corresponds to the CT scanner. Within this system, a new local coordinate system (u, v, w) was set on the centroid of each FJ surface (Fig. 1), where the u-, v-, and w- axes correspond to the normal-to-the-FJ, right-left and cranio-caudal directions, respectively. In flexion/extension, translations in mm were calculated as differences in the FJ centroid position and rotations were calculated in degrees as angular differences of the vector of the opposing surface in flexion/extension. Results are presented as mean ± SD. Differences within vertebral levels and left/right FJs were sought using 1- or 2-way ANOVA, respectively.


Hiroshi Sasaki Kazunari Ishida Katsumasa Tei Nao Shibanuma Tomoyuki Matsumoto Yuichi Kuroda Shinya Oka Tokio Matsuzaki Atsuro Uefuji Hiroomi Tateishi Ryosuke Kuroda Masahiro Kurosaka

Introduction

Increased long-term survival of TKA is becoming more important. Several studies have confirmed that optimal positioning and alignment of prosthetic components is crucial for the best long-term results. Therefore, the purpose of the current study was to compare the postoperative alignment and sizing of femoral prosthesis among patients performed by 3 different navigation systems.

Methods

Twenty patients who underwent primary TKA (E. motion; B. Braun Aesculap, Tuttlingen, Germany) using a CT-free navigation system (OrthoPilot v 4.2) by modified gap technique were enrolled in this study. The results of this study group were retrospectively compared with those in a control group of 20 matched-paired posterior stabilized TKAs (Triathlon;Stryker; Mahwah, NJ, USA) which were using another CT-free navigation system (Stryker Navigation System) by measured technique and 20 matched-paired posterior stabilized TKAs (Press-fit Condylar prosthesis; DePuy, Tokyo, Japan) using CT-based navigation system (VectorVision) by measured technique. Several parameters were evaluated for each patient using Athena Knee (Softcube Co, Ltd. Osaka, Japan), 3-D image-matching software. The coronal component angles and sagittal component angles were measured in relation to mechanical axis (MA). In addition, axial femoral component angle was measured in relation to surgical epicondylar axis (SEA) and axial tibial component angle was measured in relation to Akagi line.


Tatsuya Sato Hiroshi Ito Hiromasa Tanino Yasuhiro Nishida

[Introduction]

It is said that the mechanical stress is a main factor to advance degenerative osteoarthritis. Therefore, to keep the joint stability is very important to minimize mechanical stress. Methods to evaluate bone-related factor are almost established, especially in hip dysplasia. On the other hand, it is unclear how much each soft tissue contribute to the joint stability. In this study we evaluated the soft tissue contribution for hip joint stability by distraction testing using MTS machine.

[Materials & Methods]

We used seven fresh frozen hips from four donors, whose race was all western and reason of death was not related to hip disease in all cases. Average age of them at death was 83 years old. Mean average weight and height were each 52 kg and 162 cm. We retrieved hemi pelvis and proximal femur which kept hip joint intact. We removed all other soft tissue except iliofemoral ligament, pubofemoral ligament, ischiofemoral ligament and capsule. The hemi-pelvis mounted on angular-changeable fixator and the femur fixed to MTS machine (Figure 1). XY sliding table was used to minimize the horizontal direction stress during distraction. MTS machine was set to pull the femur parallel to its shaft by 0.4 mm/sec velocity against pelvis after 10N compression and to keep 5 mm distance for 5 seconds. We measured the force at 1 mm, 3 mm, 5 mm distraction. In case the joint was dislocated, the maximum force just before dislocation was recorded. The specimen was changed its posture as neutral (flexion0° abduction0° external rotation0°), flexion (flexion60° abduction0° external rotation0°), abduction (flexion0° abduction30° external rotation0°) and extension (extension20° abduction0° external rotation0°). Each position was measured in six sequential conditions, which are normal, Incised iliofemoral ligament, Circumferentially incised capsule, resected capsule, labral radial tear and resected labrum. After measurement joint surface was observed to evaluate the joint condition.


Loren Latta Prasad Sawardeker Check Kam Edward Milne Elizabeth Ouellette

INTRODUCTION:

Radial head arthroplasty is a reliable procedure with good functional outcomes when faced with irreparable radial head fractures. Since the first attempt at arthroplasty by Speed in 1941, there have been a variety of different designs created for radial head prostheses. There has been considerable recent interest in bipolar radial head components. However, to date, there have been few biomechanical studies comparing bipolar components to their monopolar counterparts. We examine the effects of alteration of axial length of the radial head prosthesis and force conveyed at the radiocapitellar joint in a head-to-head comparison of bipolar implants to monopolar implants.

METHODS:

Sixteen fresh-frozen, sided cadaveric arms were utilized. Radial heads were resected and either a monopolar, rigid, metal radial head prosthesis (Solar, Stryker, Mahwah, NJ) was implanted or a bipolar metal prosthesis used (Katalyst, Integra, Plainsboro, NJ). Adjustments of radial head length were made in 2 mm increments using radiolucent washers to create an understuffed (−2), neutral (0), and overstuffed (+2, +4) effect, see Fig. 1. Forearms were cyclically loaded in compression from 13N to 130N with the forearm in neutral. Radiocapitellar forces were measured using Tekscan (Tekscan, Inc., Boston, MA) pressure sensors with radial head length set at −2 mm, 0, +2 mm and +4 mm and comparisons were made with the neutral (0) radial head, see Fig. 2. Multivariant ANOVA with Tukey's HSD correction was used for statistical analysis.


TC Clark C Plaskos FH Schmidt

Introduction:

Computer-assisted surgery (CAS) aims to improve component positioning and mechanical alignment in Total Knee Arthroplasty (TKA). Robotic cutting-guides have been integrated into CAS systems with the intent to improve bone-cutting precision and reduce navigation time by precisely automating the placement of the cutting-guide. The objectives of this study were to compare the intra-operative efficiency and accuracy of a robotic-assisted TKA procedure to a conventional computer-assisted TKA procedure where fixed sequential cutting-blocks are navigated free-hand.

Methods:

This was a retrospective study comparing two distinct cohorts: the control group consisted of patients undergoing TKA with conventional CAS (Stryker Universal Knee Navigation v3.1, Stryker Orthopaedics, MI) from May 2006 to September 2007; the study group consisted of patients undergoing TKA with a robotic cutting-guide (Apex Robotic Technology, ART, OMNIlife Science, MA) from October 2010 to May 2012. Exclusion of patients with preexisting hardware in the joint or an absence of navigation data resulted in a total of 29 patients in the control group and 52 patients in the study group. Both groups were similar with respect to BMI, age, gender, and pre-operative alignment. All patients were operated on by a single surgeon at a single institution.

The navigation log files were analyzed to determine the total navigation time for each case, which was defined as the time from the start of the acquisition of the hip center to the end of the final alignment analysis for both systems. The intraoperative final mechanical axis was also recorded. The tourniquet time (time of inflation prior to incision to deflation immediately after cement hardening) and hospitalization length were compared. Linear regression analysis was performed using R statistical software v2.12.1.


David Scott

Introduction:

Significant proximal femoral remodeling occurs after total hip arthroplasty (THA), with regions of bone loss, and regions of hypertrophy. This study compared three implants for changes in femoral bone mineral density over 2 years following primary uncemented hip arthroplasty with a conventional stem (THA), a novel femoral neck-sparing short hip stem (NS-THA), and resurfacing hip arthroplasty (RHA).

Methods:

Seventy-one patients participated in this non-randomized, prospective study. All patients had a diagnosis of osteoarthritis and underwent primary uncemented hip arthroplasty. Dual Energy XRay Absorptomitry (DXA) scans were performed at preoperative, 3–7 days post-op, 6 weeks, 6 months, one, and two years post-op. Using custom 2 cm zones, 19 zones were observed for percent changes in bone mineral density (BMD). Radiographs and Harris Hip scores were obtained at each visit.


David Scott

Introduction:

There is no consensus whether a traditional post and cam-style posterior stabilized (PS) total knee device is superior to a deep-dish, more congruent cruciate-substituting (CS) device. This study compared the clinical and radiographic outcomes of two such devices. The primary hypothesis was that the clinical outcomes would be equivalent and the secondary hypothesis was that there would be measurable differences in the tourniquet time and intraoperative blood loss.

Methods:

This prospective randomized study compared the outcomes of 56 patients who received a Triathlon® PS tibial insert and 55 patients who received a Triathlon® CS lipped tibial insert (Stryker®, Mahwah, NJ, USA). All patients undergoing elective primary total knee arthroplasty were eligible for participation. Institutional Review Board approval and informed consent from participants were obtained. Regular clinical and radiographic assessments were performed preoperatively, 6 weeks, 6 months, and annually. Data were compared using chi-square test and T-test with a significance level of .05.


Peter Sculco Joseph Lipman Craig Klinger Lionel E. Lazaro Alexander Mclawhorn David J. Mayman Chitranjan S Ranawat

Introduction:

Successful total joint arthroplasty requires accruate and reproducible acetabular component position. Acetabular component malposition has been associated with complications inlcuding dislocation, implant loosening, and increased wear. Recent literature had demonstrated that high-volume fellowship trained arthroplasty surgeons are in the “safe zone” for cup inclination and anteversion only 47% of the time. (1) Computer navigation has improved accuracy and reproducibility but remains expensive and cumbersome to many hospital and physicians. Patient specific instrumentation (PSI) has been shown to be effective and efficient in total knee replacements. The purpose of this study was to determine in a cadaveric model the anteversion and inclination accuracy of acetabular guides compared to a pre-operitive plan.

Methods:

8 fresh-frozen cadaveric pelvis specimens underwent Computer Tomography (CT) in order to create a 3D reconstruction of the acetabulum. Based on these 3D reconstruction, a pre-operative plan was made positioning the patient specific acetabulum guides at 40 degrees of inclination and 20 degrees of anteversion in the pelvis.(Figure 1) The guides were created based on the specific bony morphology of the acetabular notch and rim. The guides were created using a 3D printer which allowed for precise recreation of the virtual model. 7 cadaveric specimens underwent creation and implantation of a acetabular guide specific to each specimens bony morphology. Ligamentum, pulvinar, and labum were removed for each cadaver prior to implantation to prevent soft tissue obstruction. The guides were inserted into the acetabular notch with the final position based on the fit of the guide in the notch. (Figure 2) Post-implantation CT was then performed and inclination and anteversion of the implanted guide measured and compared to the preoperative plan.


Ashit Shah

Introduction:

One of the important criteria of the success of TKR is achievement of the Flexion ROM. Various factors responsible to achieve flexion are technique, Implant and patient related. Creation of the Posterior condylar offset is one of the important factors to achieve satisfactory flexion.

Aim:

To correlate post op femoral condylar offset to final flexion ROM at 1 yr. post op.


Sami Shalhoub Chadd Clary Lorin Maletsky

Introduction

Quadriceps weakness, which is often reported following total knee arthroplasty (TKA), affects patients' abilities to perform activities of daily living [1]. Implant design features, particularly of the patella-femoral joint, influence the mechanical advantage of the extensor mechanism. This study quantifies the changes in extensor mechanism moment arms due to different patellar resurfacing options during TKA.

Methods

Posterior-stabilized TKR surgery was performed on seven cadaveric knees which were subsequently mounted in the Kansas Knee Simulator (KKS) [2]. A dynamic physiological squat was simulated between 5° and 80° knee flexion at 50% body weight while knee kinematics, including the lines of action of the rectus femoris (RF) muscle and patellar tendon (PT), were recorded using an optical tracking system. The simulation was performed after three patella treatment options: 1) leaving the native patella Unresurfaced, 2) resurfaced with a medialized Dome patella, and 3) resurfaced with a medialized Anatomic patella which included a conforming lateral facet. Moment arms from the tibio-femoral helical axis to the line of action of the PT and the RF were calculated for each patella condition.


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Rajeev Kumar Sharma

INTRODUCTION:

Management of developmental dysplasia of hip in adult is challenging and needs more to be understood in terms of ideal implant, position of acetabulum and operative technique. Patient may present very late, usually when osteoarthritic changes develop followed by pain. Operative management is difficult because of hypoplastic femoral medullary canal and shallow acetabulum filled with soft tissues. Altered anatomy of neurovascular structures also pose a risk of being injured during surgery.

AIMS:

The goal of this study was to evaluate late results of total hip arthroplasty in adults after a minimum of 5 years follow-up.


Adrija Sharma Richard D. Komitek Darryl D'Lima Clifford Colwell

Telemetric knee implants have provided invaluable insight into the forces occurring in the knee during various activities. However, due to the high amount of cost involved only a few of them have been developed. Mathematical modeling of the knee provides an alternative that can be easily applied to study high number of patients. However, in order to ensure accuracy these models need to be validated with in vivo force data. Previously, mathematical models have been developed and validated to study only specific activities. Therefore, the objective of this study was compare the knee force predictions from the same model with that obtained using telemetry for multiple activities.

Kinematics of a telemetric patient was collected using fluoroscopy and 2D to 3D image registration for gait, deep knee bend (DKB), chair rise, step up and step down activities. Along with telemetric forces obtained from the implant, synchronized ground reaction forces (GRF) were also collected from a force plate. The relevant kinematics and the GRF were input into an inverse dynamic model of the human leg starting from the foot and ending at the pelvis (Figure 1). All major ligaments and muscles affecting the knee joint were included in the model. The pelvis and the foot were incorporated into the system so as to provide realistic boundary conditions at the hip and the ankle and also to provide reference geometry for the attachment sites of relevant muscles. The muscle redundancy problem was solved using the pseudo-inverse technique which has been shown to automatically optimize muscle forces based on the Crowninshield-Brand cost function. The same model, without any additional changes, was applied for all activities and the predicted knee force results were compared with the data obtained from telemetry.

Comparison of the model predictions for the tibiofemoral contact forces with the telemetric implant data revealed a high degree of correlation both in the nature of variation of forces and the magnitudes of the forces obtained. Interestingly, the model predicted forces with a high level of accuracy for activities in which the flexion of the knee do not vary monotonically (increases and decreases or vice-versa) with the activity cycle (gait, step up and step down). During these activities, the difference between the model predictions with the telemetric data was less than 5% (Figure 2). For activities where flexion varies monotonically (either increases or decreases) with activity (DKB and chair rise) the difference between the forces was less than 10% (Figure 3).

The results from this study show that inverse dynamic computational models of the knee can be robust enough to predict forces occurring at the knee with a high amount of accuracy for multiple activities. While this study was conducted only on one patient with a telemetric implant, the required inputs to the model are generic enough so that it is applicable for any TKA patient with the mobility to conduct the desired activity. This allows kinetic data to be provided for the improvement of implant design and surgical techniques accessibly and relatively inexpensively.


Adrija Sharma Christopher Carr Joseph Cheng Mohamed Mahfouz Richard Komistek

Mathematical modeling provides an efficient and easily reproducible method for the determination of joint forces under in vivo conditions. The need for these new modeling methodologies is needed in the lumbar spine, where an understanding of the loading environment is limited. Few studies using telemetry and pressure sensors have directly measured forces borne by the spine; however, only a very small number of subjects have been studied and experimental conditions were not ideal for giving total forces acting in the spine. As a result, alternative approaches for investigating the lumbar spine across different clinical pathologies are essential. Therefore, the objective of this study was to develop of an inverse dynamic mathematical model for theoretically deriving in-vivo contact forces as well as musculotendon forces in patients having healthy, symptomatic, pathological and post-operative conditions of the lumbar spine.

Fluoroscopy and 3D-to-2D image registration were used to obtain kinematic data for patients performing flexion-extension of the lumbar spine. This data served as input into the multi-body, mathematical model. Other inputs included patient-specific bone geometries, recreated from CT, and ground reaction forces. Vertebral bones were represented as rigid bodies, while massless frames symbolized the lower body, torso and abdominal wall (Figure 1). In addition, ligaments were selected and modeled as linear spring elements, along with relevant muscle groups. The muscles were divided into individual fascicles and solved for using a pseudo-inverse algorithm which enabled for decoupling of the derived resultant torques defining the desired kinetic trajectory for the muscles.

The largest average contact forces in the model for healthy, symptomatic, pathological, and post-operative lumbar spine conditions occurred at maximum flexion at L4L5 level and were predicted to be 2.47 BW, 2.33 BW, 3.08 BW, and 1.60 BW, respectively. The FE rotation associated with these theoretical force values was 43.0° in healthy, 40.5° in symptomatic, 44.4° in pathological, and 22.8° in post-operative patients. The smallest forces occurred as patients approached the upright, standing position, followed by slight increases in the contact force at full extension. The theoretically derived muscle forces exhibited similar contributory force profiles in the intact spine (healthy, symptomatic, and pathologic); however, surgically implanted spines experienced an increase in the contribution of the external oblique muscles accompanied with decreased slope gradients in the muscle force profiles (Figure 2).

These altered force patterns may be associated with the decrease in the predicted contact forces in post-operative patients. In addition, the decreased slope gradients in surgically implanted patients corresponds with the observed difficulty of performing the prescribed motion, possibly due to improper muscle firing, thereby leading to slower motion cycles and less ranges-of-motion. On the contrary, patients having an intact spine performed the activity at a faster speed and to greater ranges-of-motion, which corresponds with the higher contact forces derived in the model. In conclusion, this research study presented the development of a mathematical modeling approach utilizing patient-specific data to generate theoretical in-vivo joint forces. This may serve to help progress the understanding for the kinetic characteristics of the native and surgically implanted lumbar spine.


Full Access
Yoshihiro Shibata Hirotaka Iguchi Satona Murakami Hiroto Mitsui

Background:

For hip prostheses, short stems allow easy insertion and reduce thigh pain risk, and are therefore suitable for Minimally Invasive Surgery. However, clinical outcome depends on sufficient initial fixation in the proximal femoral component. Revelation stems are designed to increase medullary cavity occupancy in the proximal femoral component and allow physiological load transmission within this component. Theoretically, on initial fixation of the proximal part of the stem, fixation remains unaffected by cutting the distal part of the stem. Recently, the Revelation micro MAX stem has become available. In this system, only the distal part of the stem is removed. To prepare for the introduction of this stem, we evaluated its rotational stability by installing it in the femurs of formalin-fixed cadavers. We then evaluated the time course of changes in bone density at the stem circumference and stem position by CT in the first eight patients undergoing hip arthroplasty.

Subjects and Methods:

Micro MAX stems were inserted into the left femurs of one male and six female cadavers (76 to 95 years of age). A commonly used torque meter was mounted on the stem, and stem fixation was evaluated by the application of clockwise torque of 6 to 12 N-m. Further, in patients, three men and five women (age range 38–83 years, mean 67 years; two cases of femoral head necrosis, two of femoral neck fracture, and four of osteoarthritis of the hip) who underwent surgery with the micro MAX stem from July 2012 to April 2013 were evaluated at 3 weeks, and 3 and 6 months after surgery for stem insertion angle and stem subsidence by CT, and for bone density around the stem by the DEXE method.


Hiroki Shimodaira Keiji Tensho Masaaki Maruyama

BACKGROUD/PURPOSE

Recently, the use of a large diameter femoral head has been discussed as a means to reduce the risk of hip dislocation after total hip arthroplasty (THA). Although it has been clear that increasing the head size increases the oscillation angle and hip stability, a consensus on the usefulness of a larger head size has not been reached due to an increased propensity for bone impingement. We studied the effect of the range of motion (ROM) and bone impingement caused by increasing the femoral head size using a 3D simulation system.

PATIENTS AND METHODS

All patients who had undergone a primary THA in our hospital from October 2010 were selected, and we excluded those with severe osteoarthritis, severe dysplasia (Crowe group), or excessive femoral neck anteversion (35°). This resulted in 60 patients (16 men and 44 women), with a mean age of 66.6 years (range, 47–83 years). The diagnoses were osteoarthritis in 42 hips, osteonecrosis in 11 hips, rheumatoid arthritis in four hips, and femoral neck fracture in three hips. A virtual hip model was generated from the preoperative CT scan and a component was virtually implanted via computer simulation software (Zed Hip, LEXI, Japan). The acetabular cup was implanted with an inclination of 45°, anteversion of 20°, and the femoral stem was implanted into the femur recreating the same head height with an anteversion of 25°. We defined three leg positions: (A) maximum flexion (B) internal rotation with hip in 90°of flexion and 20°of adduction as posterior dislocation, and (C) external rotation with hip in 0°of extension as anterior dislocation. In each leg position, range of motion up to the impingement and the type of impingement (implant or bone) was assessed with 22-, 26-, 28-, 32-, and 36 mm femoral head sizes.


Takaaki Shishido Toshinori Masaoka Toshiyuki Tateiwa Kosuke Kubo Kengo Yamamoto

Introduction

Bi-Metric® cementless primary stem is tapered, rounded conical shaped and coated with plasma spray porous to one-third from the proximal. Fixation is achieved by a press-fit insertion in the Metaphyseal-diaphyseal junction. From 1986 until now, nearly 700 Bi-Metric® stems have been implanted at our hospital. The purpose of this study was to present the clinical and radiological findings including a survival analysis of a consecutive Bi-Metric® stems series followed for over 10 years.

Materials and methods

112 primary cementless THAs in 96 patients using the Bi-Metric® femoral tapered stem were available for clinical and radiological evaluation with a minimum follow-up of ten years. Malloy-Head 4-fined acetabular cup was used in all hips. Follow-up was at a mean of 13 years. We applied THA in 84 patients for osteoarthritis, in 6 avascular necrosis for the femoral head and in 6 for rheumatoid arthritis. The mean age of the patients was 59.5 years. Clinically, pain ROM walking and ADL were evaluated according to the Japanese association hip (JOA) score, and complications and survivorship were investigated. Radiographic results were described according to the 7 femoral Gruen zones. Stem fixation in accordance with the method of Engh at al, cancellous condensation, reactive line, osteolysis, stem subsidence, and bone atrophy with stress shielding were examined. Wear was measured according to the method described by Livermore et al., and the effect of the wear on osteolysis was investigated.


Peter Simon Nazeem Virani Miguel Diaz Matthew Teusink Brandon Santoni Mark Frankle

Introduction:

Subchondral bone density (SBD) distribution is an important parameter regarding that may be important when considering implant stability. This parameter is a reflection of the loading experienced by the joint throughout the lifetime and may be useful in pre-surgical planning and implant design. Clinically, the question of the glenoid surface preparation for TSA/RSA remains controversial, despite numerous published studies on glenoid bone morphology. To address this question, there exists a need to develop a 3D quantitative method capable of analyzing the complex glenoid bone morphology at different depths from the surface. Computed tomographic osteoabsoptiomery (CT-OAM) evaluates SBD based on the Housfield Unit (HU) value of each pixel. In this pilot study, we aimed to analyze SBD distribution of the glenoid at different depths by means of CT-OAM in male TSA subjects.

Materials and Methods:

A study group of twenty male TSA patients (61–69y.o) were included in this study. Each subject obtained a pre-operative CT scan following a standardized protocol on the same CT scanner (1.25 mm slice thickness). Resultant DICOM 2D images were processed in custom-written program (VC++) and the surface of every glenoid was manually traced from the axial slices. Care was taken during the manual tracing process to exclude osteophytes and cyst formations from the resultant surface. Values of HU at every selected pixel on the surface of the glenoid were recorded. Subsequently, the layer of pixels at a 0.5 mm distance from the previous surface was virtually scraped and the HU values of new layer of pixels were recorded. This routine was repeated up to a depth of 5 mm from the glenoid surface, taking measurements on 11 virtual 3D surfaces with a thickness of 0.5 mm. Mean SBD distribution was reported for each layer and differences were compared using ANOVA and Fisher's post-hoc test.


In Soo Song

Purpose:

To evaluate the results of reverse total shoulder arthroplasty for complicated proximal humerus fractures in old ages.

Materials and Methods:

We retrospectively evaluated 13 cases who underwent reverse total shoulder arthroplasty for proximal humerus fracture, fracture-dislocation and nonunions of the fractures. Mean age was 77 years old and mean follow-up period was 15.2(12–26) months. four part fractures of proximal humerus in 7 cases, fracture-dislocation in 3 cases, locked dislocation with greater tuberosity in 2 cases, nonunion with defiency of rotator cuff in 1 case were included (Fig. 1, Fig. 2, Fig. 3). We evaluated mean ASES, mean UCLA, mean KSS, mean SST and mean range of motion (ROM).


Marc Stein

Smart instrumentation targets optimal joint hardware installation. Intelligent implants target the chronic assessment of joint health and hardware condition.

Intelligent implants would facilitate the collection of data, closing the loop to drive best surgical practice, joint system design, and the improvement of outcomes. Intelligent devices could assist post-op in managing pain and promoting recovery. Intelligent implants could offer opportunity for early detection and less invasive intervention should problems arise acutely, or even long after implant.

While the development of smart instrumentation is tactically important, the development of intelligent implants is vital to the improvement of outcomes, and should be central to the strategic vision for orthopedic technology development.

KEY DISCUSSION POINTS

Define “smart” instruments in orthopedics and why there is a need for developing these devices to achieve optimal joint hardware installation.

Define “intelligent” implants in orthopedics and why there is a need for developing these devices to facilitate the collection of data, and thereby “closing the loop” with smart instrumentation to drive best surgical practice and joint system design.

Review clinical benefits of intelligent implants in post-operation pain management and recovery, as well as early problem detection facilitating less invasive intervention both acutely and chronically.

Understand the latest advances in sensors and related technologies for orthopedic implants and implementing best practices for their use in medical design.

Describe the reduction to practice of an intelligent implant tray capable of measuring and monitoring load, position, and the early onset of infection, and capable of delivering neuro-stimulation for pain management.


Hasham Alvi Micheal Luo Rushi Talati Patrick Sweeney Anay Patel Mark Yaffe S. David Stulberg

Introduction:

Total knee arthroplasty (TKA) is an effective operation for the management of osteoarthritis of the knee. Conventional technique utilizing manual instrumentation (MI) allows for reproducible and accurate execution of the procedure. The most common techniques make use of intramedullary femoral guides and either extrameduallary or intrameduallary tibial guides. While these methods can achieve excellent results in the majority of patients, those with ipsilateral hardware, post-traumatic deformity or abnormal anatomy may preclude the accurate use of these techniques.

Patient-specific instrumentation (PSI) is an alternative innovation for total knee arthroplasty. Utilizing magnetic resonance imaging (MRI) or computed tomography (CT), custom guide blocks are fabricated based on a patient's unique anatomy. This allows for the benefits of computer assisted navigation (CAN) but without the increased operative times or the high learning curve associated with it. Furthermore it allows the use of familiar cutting blocks and guides to check the accuracy of the PSI guide blocks. In this study we sought to evaluate the accuracy of PSI techniques in patients with previous ipsilateral hardware, which would make the use of MI technically challenging and possibly subject to inaccuracy.

Methods:

After reviewing our database of 300 PSI total knee arthroplasty patients, 16 patients were identified (10 male, 6 female) using the Zimmer NexGen Patient Specific Instrumentation System. Fourteen patients included in the study had a preexisting total hip arthroplasty on the ipsilateral side, 1 had a preexisting sliding hip screw, and 1 patient had a preexisting cephalomedullary nail. Postoperative mechanical axis alignment measurements were performed using plain long-standing radiographs. The American Knee Society Score was used to evaluate clinical outcomes postoperatively.


Jayson Zadzilka Bernard Stulberg Brian Rutt Matthew Stover

INTRODUCTION:

The senior surgeon has performed THA in his practice for over 30 years, and, while performing THA and revision THA utilizing a variety of surgical approaches, has employed and taught the modified Gibson posterolateral approach to the hip joint as his “workhorse” surgical approach for the majority of his career. In following the development of the DAA, he felt that there were subgroups of patients in his practice for whom the DAA, and supine THA, might prove beneficial, and started to introduce this approach into his practice 2 years ago. This retrospective review describes the risks and benefits of choosing to introduce this approach, and outlines a rational way in which surgeons can decide if they should learn and then offer this approach to appropriate patients within their practice.

METHODS AND MATERIALS:

A retrospective study was performed comparing outcomes of patients who underwent THA with the standard posterolateral approach vs. those who underwent THA with the direct anterior approach. Demographics such as age, gender, BMI and medical history were obtained. In addition, operative information and pre- and post-operative Harris Hip Score (HHS) evaluations were collected. Radiographic information and details about complications were also acquired.


Carlos Higuera Joseph Styron Gregory Strnad Wael Barsoum Joseph Iannotti

Introduction:

Patient medical comorbidities are well-established risk modifiers of THA patient outcomes. Patient's mental state preoperatively may influence postoperative functional outcomes though just like any medical comorbidity. This study sought to determine if patient confidence in attaining post-operative functional goals was associated with objective and subjective outcomes following THA.

Methods:

Patients undergoing primary or revision THA at a single institution between 2008 and 2010 were administered a questionnaire consisting of demographics, body mass index, Hip Dysfunction Osteoarthritis and Outcomes Score (HOOS), SF-12 scores, the level of functionality they hoped to gain postoperatively and their confidence in attaining that goal (0–10 scale) preoperatively and postoperatively at last follow-up (minimum 12 months). Measured outcomes included length of stay, 30-day readmission, HOOS, and SF-12 physical component scores. Correlation of patient confidence in attaining treatment goals and the outcomes collected was established using multiple linear and logistic regression models that were adjusted for all variables, including baseline mental and functional scores.


Edwin Su Lawrence R Housman John Masonis John W Noble

Background

Post-market surveillance is necessary to ensure the safety and efficacy of newly introduced technologies and implants. The Birmingham Hip Resurfacing (Smith and Nephew, Inc., Memphis, TN) was the first hip resurfacing implant approved for use by the US FDA in May 2006. A prospective, multi-center postmarket approval study has been in progress to assess safety and efficacy of this implant.

Methods

Patients meeting inclusion criteria were enrolled at five sites. Clinical evaluation and radiographs were obtained at 3 months and 1 year, and annually thereafter for a total of 10 years. Blood metal ion levels were measured at 1 year and 4 years.


Takashi Suzuki Keinosuke Ryu Tomohiro Yamada Kei Kojima Shu Saito Yasuaki Tokuhashi

Introduction

Accurate soft tissue balancing in knee arthroplasty is essential in order to attain good postoperative clinical results. In mobile-bearing UKA (Oxford Partial Knee unicompartmental knee arthroplasty, Biomet), since determination of the thickness of the spacer block depends on the individual surgeon, it will vary and it will be difficult to attain appropriate knee balancing. The first objective of the present study was to investigate flexion and extension medial unicompartmental knee gap kinematics in conjunction with various joint distraction forces. The second objective of the study was to investigate the accuracy of gap measurement using a spacer block and a tensor device.

Methods

A total of 40 knees in 31 subjects (5 men and 26 women) with a mean age of 71.5 years underwent Oxford UKA for knee osteoarthritis and idiopathic osteonecrosis of the medial compartment. According to instructions of Phase 3 Oxford UKA, spacer block technique was used to make the extension gap equal to the flexion gap. Adequate thickness of the spacer block was determined so that the surgeon could easily insert and remove it with no stress. Following osteotomy, the tensor devise was used to measure the medial compartmental gap between the femoral trial prosthesis and the tibial osteotomy surface (joint component gap) (Fig. 1 and 2). The medial gap was measured at 20° of knee flexion (extension gap) and 90° of knee flexion (flexion gap) with 25N, 50N, 75N, 100N, 125N, 150N of joint distraction force. Corresponding size of bearing was determined for the prosthesis. The interplay gap was calculated by subtracting the thickness of the tibial prosthesis and the thickness of the selected size of bearing from the measured extension and flexion gaps.


Caleb Szubski Alison Klika Aiswarya Chandran Pillai Nicholas Schiltz Wael Barsoum

Introduction:

Solid organ transplant patients are living longer than in past decades, largely due to improvements in surgical technique, immunosuppressive regimens, patient selection, and postoperative care. As these patients grow older, many of them present for total hip arthroplasty (THA). However, life-long immunosuppressive therapy, metabolic disorders, and post-transplant medications may place transplant patients at higher risk for complications following THA. The objective of this study was to use a national administrative database to compare morbidity, acute complications, in-hospital mortality, length of stay (LOS), and admission costs for THA patients with and without solid organ transplant history.

Methods:

The Nationwide Inpatient Sample (NIS), the largest all-payer inpatient care database representing a 20% stratified sample of United States hospitals, was retrospectively queried for primary THA (ICD-9-CM 81.51) patients from 1998 to 2009 (n = 2,567,930; weighted national frequency). Cases were excluded (n = 324,837) for the following: age <18 years, pathologic fracture of lower extremity, malignant neoplasm and/or metastatic cancer, primary diagnosis of femoral neck fracture, admission type other than “elective,” previous and/or bilateral arthroplasty. The remaining 2,243,093 THA patients were assigned to transplant (n = 6,319; liver, kidney, heart, lung and/or pancreas transplant history) or non-transplant groups (n = 2,231,446; no history of any transplant including solid organ or tissue). Acute complications included a variety of organ-specific and procedure-related complications (i.e. mechanical implant failure, dislocation, hematoma, infection, pulmonary embolism, venous thrombosis). Multivariable regression and general estimating equations were developed to study the effect of transplant history on outcomes, adjusting for patient/hospital characteristics and comorbidity.


Caleb Szubski Travis Small Anas Saleh Alison Klika Aiswarya Chandran Pillai Nicholas Schiltz Wael Barsoum

Introduction:

Primary total knee arthroplasty (TKA) is associated with perioperative bleeding, and some patients will require allogenic blood transfusion during their inpatient admission. While blood safety has improved in the last several decades, blood transfusion still carries significant complications and costs. Transfusion indications and alternative methods of blood conservation are being explored. However, there is limited nationally representative data on allogenic blood product utilization among TKA patients, and its associated outcomes and financial burden. The purpose of this study was to use a national administrative database to investigate the trends in utilization and outcomes (i.e. in-hospital mortality, length of stay, admission costs, acute complications) of allogenic blood transfusion in primary TKA patients.

Methods:

The Nationwide Inpatient Sample (NIS), the largest all-payer inpatient care database representing a 20% stratified sample of United States hospitals, was utilized. Primary TKA (ICD-9-CM 81.54) cases from 2000 to 2009 were retrospectively queried (n = 4,544,999; weighted national frequency). A total of 67,841 admissions were excluded (Figure 1). The remaining 4,477,158 cases were separated into two study cohorts: (1) patients transfused with allogenic blood products (red blood cells, platelets, serum) (n = 540,270) and (2) patients not transfused (n = 3,936,888). Multivariable regression and generalized estimating equations were used to examine the effect of transfusion on outcomes, adjusting for patient/hospital characteristics and comorbidity.


Lowry Barnes Mark Tait

Purpose:

Total knee and hip arthroplasty is a commonly performed surgical procedure. As the population ages the numbers of these procedures are predicted to increase. Maximizing patient outcomes and decreasing healthcare delivery costs will be essential to creating a higher value U.S. healthcare system. The purpose of our study was to analyze the effect of a multidisciplinary preoperative education program (Joint Academy) on various outcomes that effect overall cost of primary hip and knee arthroplasty.

Methods:

A retrospective review of 904 patients' charts that underwent primary total hip and knee arthroplasty from October 1, 2010 to September 31, 2011 at a single institution was performed. We then compared 102 patients who did not have preoperative education to 802 patients who did have preoperative education through the Joint Academy (JA). We looked at patient length of stay (LOS), discharge disposition, and internal hospital cost. Linear regression was performed on all data to look for statistical significance.


Tatsuya Tamaki Yoko Miura Kazuhiro Oinuma Ryutaku Kaneyama Hideaki Shiratsuchi

Background:

The direct anterior approach (DAA) is one of the muscle sparing approaches in total hip arthroplasty (THA). The advantages of the DAA-THA include low dislocation rate, quick recovery with less pain, and accurate implantation. However, complications related to the learning curve have been reported. The aim of this study was to analyze the first 100 cases of DAA-THA performed by 2 surgeons.

Methods:

The records of first 100 consecutive primary DAA-THAs performed by 2 orthopedic surgeons who have np experience of DAA-THA previously were retrospectively reviewed. All operations were performed using DAA in the supine position without the special traction table. The surgical result, the early clinical results, complications, and accuracy of prosthesis placement were investigated.


Tatsuya Tamaki Akimoto Nimura Kazuhiro Oinuma Hideaki Shiratsuchi Satoshi Iida Keiichi Akita

Background:

In anterior approaches for total hip arthroplasty (THA), the femoral part of the procedure requires the release of the capsule from the greater trochanter. However, it is unknown whether any other tendons of the short external rotator muscles are also damaged during capsular release procedures. The aim of this cadaveric study was to identify the bony landmarks on the greater trochanter, which indicate the individual short external rotator muscle insertions.

Methods:

Forty-four hip regions from 28 embalmed cadavers were dissected. At first, micro-computed tomography (micro-CT) images were obtained to identify bony impressions on the greater trochanter. Then, the soft tissues around the greater trochanter were removed and their insertions were identified to assess correlation with micro-CT images.


Cuneyt Tamam Johannes F. Plate Marco Andre Augart Sarah Von Thaer John Allen Gary G. Poehling Riyaz Jinnah

Introduction:

Unicompartmental knee arthroplasty (UKA) has gained renewed interest in recent years as an alternative to total knee arthroplasty (TKA) for limited degenerative disease of the knee. However, recurrence of symptoms may be seen, compromising long-term survivorship. Arthroscopy has been used to for diagnosing and treating symptoms in problematic TKA. The aim of this study was to investigate the outcome of arthroscopic procedures in symptomatic UKA. We hypothesized that arthroscopy is a viable tool in diagnosing and treating patients with recurrent symptoms after UKA and identifying patients that will benefit from revision surgery.

Methods:

A search of the institution's joint registry was conducted to identify patients who underwent arthroscopy following UKA between 2003 and 2011. Medical records were analyzed for patient demographics and comorbidities. Clinical results following arthroscopy were evaluated using the Oxford Knee Score. All patient radiograph were assessed for component alignment and loosening.


Qiheng Tang Yixin Zhou

Objective:

Periacetabular spherical osteotomy for the treatment of dysplastic hip is effective but technically demanding. To help surgeons perform this difficult procedure reliably and safely, a computer assisted navigation technique has been developed and evaluated.

Methods:

Computed tomographic scans of 5 cadaveric pelvises were obtained and three-dimensional models were generated. The osteotomy was planned preoperatively. The pelvises were registered using an optimized algorithm. Periacetabular spherical osteotomy was performed at one side of each pelvis with navigation and at another side without navigation. The deviation of the real osteotomized surface from the planned surface was measured.


Hiromasa Tanino Tatsuya Sato Yasuhiro Nishida Hiroshi Ito

INTRODUCTION:

Modular femoral stems of Total Hip Arthroplasty (THA) have been designed to fit the metaphysis and diaphysis separately. Clinical results with modular femoral stems are reported to be satisfactory, but there exists several concerns with modular implant connections, including fretting corrosion, fracture of implant, and dissociation the stem from the proximal sleeve. Recently, we have become aware of another potential consequence of the modular design: sleeve deformation secondary to forces encountered during insertion. In our patients, we noted that the stems would not fully seat in the machined taper of the sleeve, indicating that some type deformation to the sleeve had occurred. We began an in vivo study to characterize this phenomenon. The objectives of this study were (1) Does deformation occur by impacting the sleeve into the metaphysis? (2) If so, quantify the sleeve deformation in hip arthroplasty patients.

MATERIALS AND METHODS:

One man and 7 women undergoing primary THA were enrolled. This project was approved by IRB. This modular system (4-U CLS; Nakashima Medical Co., Japan) consists of a metaphyseal sleeve that connects with the diaphyseal stem via a Morse taper. The sleeve was impacted into the metaphysis first, followed by the stem. A custom taper gauge for each size of sleeve (Figure 1A) was inserted into the sleeve before and after impacting the sleeve into the metaphysis, and the distance between the top of the sleeve and the top of the gauge was measured using a caliper (* in Figure 1B). Deformation was defined as the difference in distance between the before and the after impacted dimensions. Preoperative femoral morphology, assessed using Dorr classification system, was type A in 2 hips, type B in 5 hips, and type C in 1 hip.


Jonathan Robinson Rupesh Tarwala Parthiv Rathod Jose Rodriguez

Introduction:

The incidence of heterotrophic ossification after primary total hip arthoplasty (THA) has been reported to be between 8 to 90%. The incidence is higher in lateral approach because of extensive muscular trauma associated with it. There exists limited data on the incidence of heterotrophic ossification after direct anterior approach (DAA) THA. The purpose of this study was to assess the incidence of heterotrophic ossification after THA via the direct anterior approach and the influence of surgical technique and chemoprophylaxis.

Method:

A consecutive series of four hundred two primary uncemented direct anterior approach total hip arthoplasties in 378 patients were reviewed for incidence of heterotrophic ossification. In the first 200 total hip arthoplasties an anterior capsulectomy (Group 1) was done for exposure while in the subsequent 202 total hip arthoplasties a capsulotomy (Group 2) followed by complete release of supero-lateral flap of from its attachement to the gluteus minimus muscle and trochanter was performed (Figure 1). Group 1 received warfarin for thromboprophylaxis; while aspirin (thromboprophylaxis) and celecoxib (pain) was used in group 2. Heterotrophic ossification was classified according to Brooker's classification on plain radiographs.


Naotaka Tazaki Keisuke Hagio Masanobu Saito Kohei Kushimoto Hiroshi Egami

Purpose

Change of the pelvic tilt is an important factor affecting walking after total hip arthroplasty (THA). There are many reports of static evaluation of pelvic tilt by X-ray, however, there are few reports of dynamic evaluation during walking. In this study, we investigated change of pelvic tilt of THA subjects before and after operation during walking using an optical position sensor.

Subjects and Methods

5 normal volunteers (mean age 26.6 years old, Control group) and 10 patients who underwent primary THA due to unilateral osteoarthritis of the hip (mean age 61 years old, THA group) were enrolled. We have measured angle of the hip and inclination of the pelvis in the mid-stance phase of the affected limb during walking using a motion analyzer (MAC3D system) and acquired physical assessment of the hip preoperatively, 3 weeks postoperatively and 3 months postoperatively. The acquired data of inclination of the pelvis was classified as Duchenne or Trendelenburg type compared with that of normal volunteers.


Matthew Teeter Hee-Nee Pang Richard W McCalden Douglas Naudie Steven MacDonald

Background:

Varus-valgus constrained (VVC) implants are used in cases of severe valgus deformity, attenuated medial collateral ligament and difficulty in balancing the medial and lateral gaps of the knee. The increased constraint has been postulated to lead to more stress at the bone-implant interface and early loosening. The objective of this study was to compare the wear characteristics of the polyethylene liner in VVC prosthesis with the posterior-stabilized (PS) prosthesis and identify the factors leading to more wear in the VVC tibial inserts.

Methods:

This was a retrieval analysis of all VVC liners collected from patients who underwent revision surgery from 1999 to 2011. These patients were matched to another group with posterior-stabilized inserts who underwent revision in the same time period. These two groups of patients were similar in terms of their demographic data and implant dimensions. Inserts were divided into 16 zones and a microscopic analysis of surface damage was carried out. We determined overall damage with a scoring system. Pre-revisions radiographs were reviewed and analyzed for correlation with the wear profile.


Matthew Teeter Hee-Nee Pang Douglas Naudie Richard W McCalden Steven MacDonald

Purpose

The objective of this study was to compare the wear characteristics and damage scores in highly crosslinked (XLPE) and conventional polyethylene (CPE) acetabular liners.

Methods

This was a retrieval analysis of 13 XLPE liners obtained from patients who underwent revision surgery from 1999 to 2011. These patients were matched on patient demographics (age, BMI, side, sex, and length of implantation) and implant characteristics (inner diameter, outer diameter, and lip angle) to another group with CPE who underwent revision in the same time period. The only difference between implants was the use of XLPE. Wear analysis was performed with micro-computed tomography (micro-CT), provided thickness measurements across four quadrants of the bearing surface. Surface damage was scored and the pattern documented. The mean duration of implantation was 5.00 ± 3.36 years in the XLPE group and 5.19 ± 3.69 years in the CPE group (p = 0.12), with the longest duration exceeding 10 years.


Katsumasa Tei Tomoyuki Matsumoto Nao Shibanuma Masahiro Kurosaka Ryosuke Kuroda

Introduction

Recently, tibial insert design of cruciate-substituting (CS) polyethylene insert is employed. However, in vivo kinematics of using CS polyethylene insert is still unclear. In this study, it is hypothesized that CS polyethylene insert leads to stability of femolo-tibial joint as well as posterior-stabilized polyethylene insert, even if posterior cruciate ligament (PCL) is sacrificed after total knee arthroplasty (TKA). The purpose of this study is an investigation of in vivo kinematics of three different tibial insert designs using computer assisted navigation system intra-operatively in TKA.

Materials and Methods

Sixty-four consecutive patients who had knees of osteoarthritis with varus deformity were investigated in this study. All TKAs (Triathlon, Stryker, New Jersey, USA) were performed using computer assisted navigation system. During surgery, three different designs of polyethylene tibial trial inserts (PS, CS, and cruciate-retaining (CR) polyethylene insert) were inserted respectively after implantation of femoral and tibial components. The kinematic parameters of the soft-tissue balance were obtained by interpreting kinematics curve, which display bicompartmental gaps throughout the range of motion (ROM) after implantation of each trial insert (Figure. 1). During record of kinematics, the surgeon gently lifted the experimental thigh three times, flexing the hip and knee. Deviation of these three values in each ROM was calculated in each tibial insert in each patient for descriptive analysis.


Yuanjun Teng Jin Jiang Yayi Xia

Backgroud:

Periarticular multimodal drug injection (PMDI) during total knee arthroplasty (TKA) has been reported with promising effects, but some results still remain controversial. Therefore, we conducted a systematic review and meta-analysis based on randomized controlled trials (RCTs) to evaluate the efficiency and safety of PMDI technique in TKA.

Methods:

We systematically conducted an electronic search in the databases of PubMed, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science (SCI), and the Chinese Biomedical Literature Database (CBM). Two independent reviewers completed data collection and assessment of methodological quality according to the Cochrane Handbook 5.1. The quality of evidence of outcomes was judged using GRADE criteria. Statistical analysis was performed using the RevMan 5.1 software.


Matthew Teusink Ioannis Pappou Daniel Schwartz Mark Frankle

Background:

While reverse shoulder arthroplasty has shown successful outcomes for a variety of shoulder pathologies, postoperative instability continues to be one of the most common complications limiting outcomes. In the literature, reports of instability range from 2.4%–31%. Many authors recommend an initial attempt at closed reduction followed by a period of immobilization for management of the initial dislocation episode while others may seek to rule out infection or other secondary causes; however there is little data to support either practice. The purpose of this study was to evaluate the outcomes of patients with postoperative dislocation following reverse shoulder arthroplasty managed with closed reduction.

Methods:

A retrospective review of all reverse shoulder arthroplasties performed by a single surgeon (MF) from 2002-present was performed to identify all patients treated for postoperative dislocation treated with closed reduction, either in the office setting or under anesthesia in the operating room. A total of 21 patients were identified. Preoperative patient characteristics, implant selection, and time to initial dislocation episode were recorded. Final outcomes including recurrent instability need for revision surgery, ASES outcome score, and range of motion were evaluated.


Emmanuel Thienpont

Background

Finding the anatomical landmarks used for correct femoral rotational alignment can be difficult. The Posterior Condylar Line (PCL) is probably the easiest to find during surgery. The aim of this study was to analyze if a predetermined fixed angle referencing of the PCL could help obtain good femoral alignment in TKA patients.

Methods

2637 CT scans used for preoperative planning and creation of patient-specific instrumentation (PSI) were used to analyze the Posterior Condylar Angle (PCA) between the Surgical Epicondylar Axis (SEA) and the PCL.


Soichi Tsuji

[Introduction]

As an essential concept in TKA, preparing equalized rectangular extension and flexion gaps is recognized as desirable to ensure proper knee kinematics.

However, in the ways that was recommended by an implant manufacturer, the adjustments are so difficult, and for inexperienced doctor, we don't have an ideal technique for an additional cutting up and ligament balancing.

Then, the New method (Precut method) was introduced in order to enable an ideal adjustments.

[Method]

Sixty eights patients with osteoarthritis of the knee received TKAs using Precut method. This method is the following. At first, proximal tibia was resected 10 mm by standard cutting device. And then, femoral posterior condyle was resected 4 mm lesser than cutting line by measured resection technique (Precut method). In the next, using the spacer block 1 mm unit and the Precut trial implant (8 mm; distal femur 4 mm; posterior condyle), we investigated the bone gap and the component gap (put the Precut trial on the distal femur). Finally, we calculated the amount of the final cutting value based on the component gap.

The survey item measured the bone gap at extension and flexion, the component gap at extension and flexion after putting the Precut trial on.

Then we compared the gap difference with and without the Precut trial.


Koji Tsuji Scott Banks Kazuo Hirakawa

Introduction:

Highly cross-linked polyethylene (XLPE) was introduced into clinical practice to decrease acetabular cup wear in total hip arthroplasty (THA) based upon extremely low wear rates in vitro. Numerous short-term clinical studies using XLPE cups have shown promising improvements in wear performance. In this study we evaluated in vivo wear performance of XLPE cups compared to conventional PE (CPE) cups in primary THA at a minimum five years follow-up.

Materials and Methods:

Between October 2003 and March 2005, 114 hips were randomized to receive either a CPE cup or a XLPE cup with primary THA. A single experienced surgeon performed all cases at the same hospital. All hips received a CoCr femoral head and a cementless acetabular shell (Trilogy, Zimmer, Warsaw). One-hundred three cases received cementless femoral stems and eleven stems were cemented. Forty-six hips received a 26 mm head size CPE cup (gamma sterilized at 25 kGy), and 68 hips received XLPE cups (10 Mrad e-beam irradiation, EtO sterilized) in 26 mm (47 hips), 28 mm (11 hips) and 32 mm (10 hips) head sizes. The mean age in the XLPE and CPE groups was 57 ± 8 and 62 ± 8, respectively (p < 0.05). Mean follow up was 70 months (range, 60 to 91 months).

Supine AP radiographs were obtained postoperatively at 2, 6, 9, 12, 18, 24, 36, 48, and 60 months, and at final follow-up. Each radiograph was assessed for femoral head penetration using Roman v1.70 software (http://www.cookedbits.co.uk/roman/) and the wear magnitude was calculated relative to the 2 month postoperative radiograph.


Takashi Tsujimoto Yoshinori Kadoya

INTRODUCTION:

It has been reported that rotational deformity is present in varus osteoarthritis (OA) of the knee and the tibia rotates externally as the varus deformity progresses. Although many studies addressed the rotational alignment of the femoral and tibial component in total knee arthroplasty (TKA), the pre-and postoperative changes of the rotational alignment in varus OA knee has not been evaluated. The purpose of this study was to quantitatively analyze the alteration of rotational deformity after TKA for the varus OA knee.

METHODS:

Between July 2011 and December 2012, 157 patients (159 knees) with primary varus OA knee undergoing TKA were included. A mobile-bearing, posterior stabilized knee prosthesis was implanted with cement in all patients. Rotational deformities were evaluated with computed tomography (CT) before and after the operation. On the selected CT slices, the relative rotational position of the femur and tibia was quantified as an angle between the line perpendicular to the surgical epicondylar axis of the femur and the line connecting the tibial tubercle tip and the geometric center of the tibia. The knees were divided into three groups according to the preoperative varus deformity (Group I; 0–8° varus, n = 78, Group II; 9–17 ° varus, n = 71 and Group III; 18 ° or greater varus, n = 10) and the difference among the groups were statistically analyzed.


Harun Yasin Tuzun Faruk Akyildiz Oner Tatar Huseyin Ozkan Ibrahim Yanmis Servet Tunay

Femoroacetabular impingement (FAI) syndrome is one of the significant reasons for hip pain, loss of ROM at hip joint and developing early osteoarthritis at young active adults. FAI is not a new term and it is treated successfully with open surgical techniques. Some disadvantages of open surgical tecniques has lead orthopedists to develop arthroscopic tecniques.

At this study, we aimed to assess the effectiveness of arthroscopy at the treatment of FAI. We included 25 patients (19 male, 6 female) and evaluated retrospectively which has gone under arthroscopic surgery for the treatment of FAÄ° at Gulhane Military Medicine Academy, Department of Orthopedics and Traumatology and Ankara Koru Hospital, Department of Orthopedics and Traumatology between January 2009 and May 2012.

We have evaluated modified Harris Hip Score and Visual Analogue Score (VAS) preoperatively and postoperatively at all of our patients. Also we have evaluated, hip internal rotation and flexion range of motions clinically. Mean preoperative Harris Hip Score was 68,52 (range 55–76), mean postoperative score was 88,84 (range 72–98). Mean preoperative flexion ROM was 87, 6 (range 80–95) and 108,2 (range 90–120) postoperatively. Also 4,4 (range 0–5) degrees of mean preoperative internal rotation ROM increased to 19,80 range (10–30) degrees postoperatively. Mean preoperative alpha angle was 76,76 (range 60–90) and it was decreased to 41,76 (range 34–48) postoperatively. Mean preoperative visual analog score were decreased from 8, 63 to 2,8 postoperatively.

We had to perform o second look arthroscopy to a patient because of inadequate resection. Also femoral neck stres fracture occured at a patient probably due to early weight bearing. Transient sciatic nevre neuropraxy occured at a 3 patients and, transient ankle pain (approximately 6 weeks) had occured at 2 patients due to traction. Loss of sensation has occured at a patient due to lateral femoral cutaneus nevre injury during portal placement.

With these results, we assessed that arthroscopic treatment of the FAI syndrome is succesfull with minor complications comperable to open procedures.


Umut Erol Eren Harun Yasin Tuzun Cemil Yildiz Faruk Akyildiz Huseyin Ozkan Kadir Ozturk Servet Tunay

Arthroplasty is a successfulsurgical procedure which provides returning daily activities by relieving pain, correcting deformity, and regaining the loss of ROM which is caused by many diseases such as degenerative arthritis when conservative and other surgical techniques fail to achieve. Successful outcomes depend on many variables at arthroplasty. Proper indication, careful selection of patient, adequate surgical technique and postoperative rehabilitation plays a major role.

Despite successful outcomes achieved at arthroplasty, undesired complications can be frustrating for the patient and the surgeon. These complications can be minimized by careful preoperative planning, meticulous surgical procedure and rigorius postoperative care.

Infection is the most frequent and most effective complication on outcomes after arthroplasty. Because of that, risk factors for infection must be researched carefully and minimized preoperatively. Antibiotic prophylaxis is routinely suggested before the surgery. Using routine irrigation as well as the standard surgical technique is effective for decreasing postoperative infection rates. Antibiotic impregenated cement is used especially at revision arthroplasties and should be used at primary surgery at high risk groups.

In this study we evaluated 19 patients which admitted to Gulhane Military Academy of Medicine, Department of Orthopedics and Traumatology betwen 2007 and 2012. 5 patients had total hip arthroplasty (26.32%), 11 patients had total knee arthroplasty (57.89%) and 3 patients had hip hemiarthroplasty after femoral neck fractures. 14 of the patiens were female (73.68%) and 5 were (26,32%). Mean age was 69.74 (53–83). Primary surgery was held at our institution at 14 of the patients and 5 patients were referred from other instutitions because of their complaints.6 of the knees were right-sided and 5 of them was left-sided. 3 of the totap hips were left-sided and 2 of them was right-sided. 1 of the hip hemiarthroplasties were left-sided and 2 of them was right-sided. 42.11%of the patients were treated medically and 47.37%were treated with two staged surgery. 42.11%of the surgically treated group were healed completely and 5.26%of the patients passed away due to other comorbidities. Wound debridement was applied 10.53%of the patients which were admitted at early phase and resection arthroplasty was applied 5.26%of these patients because of the lack of response to medical and surgical debridement.

With these results, patients with infected prosthesis can present with many different symptoms and infection risk must always be considered. It must be remembered that the onset time of infection is very important during diagnosis and treatment. Follow ups and treatment protocols must be standardized by clinics as algorithms. During the treatment the surgeon must be in close contact with infectious diseases and microbiology departments. Especially by new developing techniques during the recent years, spesific agents of the infection can be determined and spesific antibiotics can be used for the treatment.


Narumi Ueda Kenichi Oe Hiroshi Kawamura Tomohisa Nakamura Naofumi Okamoto Yusuke Ueda Hirokazu Iida

Introduction:

The diagnosis of implant-associated infections is challenging, and the conventional culturing of periprosthetic tissue has been the gold standard for diagnosis of implant-associated infections. However, conventional diagnostic tests are inaccurate because the pathogenesis of implant-associated infection is related to microorganisms growing in biofilms. We compared culture of samples obtained by sonication of explanted implants to dislodge adherent bacteria from implants with conventional culture of periprosthetic tissue. The purpose of this study is to evaluate the results of sonication that is microbiological diagnostic method for implant-associated infections.

Materials and Methods:

Between January 2013 and April 2013, a total of 19 consecutive patients underwent the removal of implants at our institution. There were 15 women and 4 men with a mean age of 71 years (32 to 90) at the time of the operation. Implants were removed because of aseptic loosening in 9 patients, infection in 6 patients, necrosis in 2 patients, dislocation in 1 patient and implant fracture in 1 patient. Removed implants, including 17 joint prostheses and 2 fracture fixation devices, were subjected to sonication in a BactoSonic (BANDELIN, Germany). Preoperative bacterial culture, intraoperative conventional culture of periprosthetic tissue, intraoperative culture of sonicate-fluid, and pathological examination were assessed.


J. Va Faye B. Lassota-Korba M. La Malfa

Aim:

Enhanced recovery pathway is compromised by increased wound oozing due to chemical thromboprophylaxis increasing length of stay (LoS) and complications. We aimed to analyse the difference between LoS, VTE episodes, deep infection and return to theatre between matched cohort of patients either receiving combination therapy of Clexane followed by Rivaroxaban or Rivaroxaban only.

Methods:

We retrospectively collected data on LoS of patients undergoing hip and knee replacements, The cohorts consisted of 458 THRs (235 group I & 223 group II and 526 TKRs (250 group I & 276 group II). Group I received Rivaroxaban. Age was not an exclusion criteria and matched in both groups. ASA 1 to stable ASA3 patients were included in the cohort. Included were patients on aspirin 75 mg PO which was not stopped pre-operatively in either cohort in equal numbers. Anaesthetic and perioperative management of the patients as part of our enhanced recovery protocols were the same for both groups. Multimodal pain management, antibiotic prophylaxis, same day mobilisation, flowtron calf pumps, TED stockings, preoperative MRSA screening was standardised and matched. For TKRs a standard medial parapatellar approach and THRs a standard posterolateral (Southern) approach were utilised. Patients did not have a drain insitu. Exclusion criteria was patients with malignancy, haematological co-morbidities, Hb below 11 and BMI greater than 40.

All prosthesis used were standardised to cemented TKR, cemented THR or uncemented THR depending on bone quality at the time of surgery.

Patients in first cohort (group I) received 10 mg Rivaroxaban at 8 hours post op and continued for 14 days for TKRs and 35 days for THRs. Patients in group II received Clexane 40 mg SC at 8 hours post op followed by Rivaroxaban at 24 hours after first dose of Clexane and continued daily for 14 days for TKRs and 35 days for THRs.


Vinod Vaishnav Nilen Shah

Background:

Morbidity of any surgical procedure is undefined. Major surgeries and minor surgeries have different morbidities but the morbidity after any surgical procedure is neither quantified nor defined in literature. Minimally invasive surgeries have evolved in all surgical branches and are known to have less morbidity after the surgery. There is no score or index to assess early recovery after any surgical procedure.

Aim:

The objective of the study was to develop a scoring method to assess early post operative recovery of TKR patients.


Catherine Van Der Straeten Damien Van Quickenborne Bart De Roest Jan Victor Koen De Smet

Introduction

Metal-on-metal hip resurfacings (MoMHRAs) have a characteristic wear pattern initially characterised by a run-in period, followed by a lower-wear steady-state. The use of metal ions as surrogate markers of in-vivo wear is now recommended as a screening tool for the in-vivo performance of MoMHRAs. The aims of this retrospective study were to measure ion levels in MoMHRAs at different stages during the steady-state in order to study the evolution of wear at minimum 10 years postoperatively and describe factors that affect it.

Materials and methods

A retrospective study was conducted to investigate the minimum 10-year survivorship of a single-surgeon Birmingham Hip Resurfacing (BHR) series, and the evolution of metal ion levels. Implant survival, Harris Hip Scores (HHS), radiographs and serum metal ion levels were assessed. The evolution of metal ion levels was evaluated in 80 patients for whom at least two ion measurements were available at more than 12 months postoperatively, i.e. past the run-in phase. Ion level change (Delta Cr; Delta Co) was defined as Cr or Co level at last assessment minus Cr or Co level at initial assessment. Sub-analysis was performed by gender, diagnosis, age, femoral component size and cup inclination angle.


Catherine Van Der Straeten Erik Witvrouw Tine Willems Lotte Verstuyft Jan Victor Johan Bellemans

Background:

Recently a new version of the Knee Society Knee Scoring System has been developed, adapted to the lifestyle and activities of contemporary patients with a Total Knee Arthroplasty (TKA). It is subdivided into 4 domains including an Objective Knee Score, a Satisfaction Score, an Expectations Score and a Functional Activity Score. Before this scale can be used in non-English speaking populations, it has to be translated and validated for specific populations. The aim of this study was to translate and validate the New Knee Society Knee Scoring System (new KSS) for Dutch speaking populations.

Materials and Methods:

A Dutch translation of the New KSS was established using a forward-backward translation protocol. 137 patients undergoing TKA were asked to complete the Dutch translation of the New KSS as well as the Dutch WOMAC, Dutch KOOS and the Dutch SF12. To determine the test-retest reliability, 53 patients were asked to fill out a second questionnaire with one-week interval. We tested the test-retest reliability of the subjective domains of the New KSS by assessing the intra-class coefficient and the Pearson correlation coefficient between the first and second questionnaires. Systematic differences between the first and second questionnaires were investigated with T-tests and non-parametric statistics. Internal consistency of the Dutch new KSS was evaluated with Cronbach's alpha. The construct validity of the Dutch New KSS was determined by comparing it to the Dutch WOMAC, Dutch KOOS and Dutch SF12 using Pearson correlation coefficients. Content validity was assessed by examining the distribution and the floor and ceiling effects of the Dutch version of the new KSS.


Pieter Boudt Iwein Piepers Catherine Van Der Straeten Alexander Van Tongel Lieven De Wilde

Background:

The balance between the subscapularis muscle and the infraspinatus/teres minor muscles, often referred to as the rotator cuff ‘force couple’, has been proposed to be critical component for glenohumeral stability. Function of these muscles can be estimated with the evaluation of muscle atrophy. In clinical practice, muscle cross-sectional area (CSA) rather than 3D muscle volume measurement have been used because it is less time consuming. Because combined anthropometric measures of length and width more accurately define the muscular volume it seems logical to study the transversal rotator cuff force couple in the transversal plane an not in the sagittal plane of the body because both parameters can be included. But is it not clear which transversal CSA has the best correlation with muscle volume

Purpose:

To determine the optimal transversal CSA that has the best correlation with muscle volume.


Dieter Vangeneugden Joyce Van Den Broeck Karim Chellaoui Martijn Schotanus Bert Boonen Nanne Kort

Background

The full leg x-ray is a widely used imaging modality for post-operative assessment of total knee replacement (TKR). However, these assessments require controlled conditions and precise measuring in order to be accurate. inter-observer reliability remains a matter of concern as well. This study examines whether intersurgeon differences are significant.

Method

Post-operative lateral and full-leg frontal x-rays of 26 patients were assessed by 6 surgeons according to a strict measuring protocol. Four measurements (Figure 1 and 2) were taken of which two were on the femur (Femoral Varus Angle FVA and Femoral Flexion Angle FFA) and two, on the tibia (Tibial Varus Angle TVA; Tibial Slope Angle TSA). A random effects, two-way ANOVA was performed on the data using Minitab (v 16.0, Minitab Inc., Pennsylvania, USA) to determine whether a surgeon has influence on the results (α = 0.05). Intra-class correlation coefficients (ICC) and standard error of measurements (SEM) resulting in smallest detectable changes (SDC) were also calculated [1].


Shyam Vekaria S. David Stulberg Victoria Brander

Introduction:

The addition of neck-stem modularity of femoral components allowed for increased versatility in controlling stability, head center, and limb length in total hip arthroplasty (THA). Recent reports of neck-stem corrosion, complicated by adverse local tissue reaction, have raised concern and prompted further patient evaluation for revision arthroplasty.

Methods:

This was a single center, retrospective case series of thirteen hips in twelve patients. The cohort included eight women and four men, with an average age of 69.5 years (range 50–82), who underwent primary THA with a dual-taper femoral component with a titanium alloy stem, cobalt-chromium (CoCr) alloy modular neck and CoCr alloy head. Patients were followed an average of 34.3 months postsurgical (range 24–38.5 months). Each patient underwent serologic studies including metal ion levels, and Metal Artifact Reduction Sequence (MARS) magnetic resonance imaging (MRI) or Ultrasound. All patients were then referred for fluoro-assisted hip aspiration. Four patients underwent revision surgery.


David Walker Aimee Struk Thomas Wright Scott Banks

Background:

Little validation has been done to compare the principle of using the contralateral side as compared to and age and gender matched control. This study seeks to assess the validity of using the contralateral shoulder as the control as opposed to an age- gender- matched control. This study will give insight as to whether the contralateral side is a viable control as compared to a normal age and gender matched control. The study showed that the use of the contralateral shoulder was not a viable normal control.

Methods:

50 subjects were recruited for an institutional review board approved study. We studied 33 subjects who were ≥ 6 months post unilateral RSTA and 17 subjects who comprised our normal age- and gender-matched control group. The activity of the contralateral shoulder for each RTSA subject was recorded. All subjects were prompted to elevate their arm to perform abduction, flexion, and external rotation activities in both weighted and un-weighted configurations. Electromyography activation of the anterior, lateral, and posterior aspects of the deltoid and the upper trapezius muscles were recorded bilaterally using bipolar surface electrodes. Motion capture using passive reflective markers was used to quantify three-dimensional motions of both shoulders.


David Walker Aimee Struk Thomas Wright Scott Banks

Background:

An upper extremity model of the shoulder was developed from the Stanford upper extremity model (Holzbaur 2005) in this study to assess the muscle lengthening changes that occur as a function of kinematics for reverse total shoulder athroplasty (RTSA). This study assesses muscle moment arm changes as a function of scapulohumeral rhythm (SHR) during abduction for RTSA subjects. The purpose of the study was to calculate the effect of RTSA SHR on the deltoid moment arm over the abduction activity.

Methods:

The model was parameterized as a six degree of freedom model in which the scapula and humeral rotational degrees of freedom were prescribed from fluoroscopy. The model had 15 muscle actuators representing the muscles that span the shoulder girdle. The model was then uniformly scaled according to reflective markers from motion capture studies. An average SHR was calculated for the normal and RTSA cohort set. The SHR averages were then used to drive the motion of the scapula and the humerus. Lastly 3-dimensional kinematics for the scapula and humerus from 3d-2d fluoroscopic image registration techniques were used to drive the motion of model. Deltoid muscle moment arm was calculated.


Arjuna Imbuldeniya Selin Munir Jason Chow William Walter Bernard Zicat William Walter

Introduction

Squeaking is a potential problem of all hard on hard bearings yet it has been less frequently reported in metal-on-metal hips. We compared a cohort of 11 squeaking metal-on-metal hip resurfacings to individually matched controls, assessing cup inclination and anteversion between the groups to look for any differences.

Methods

We retrospectively reviewed the patient records of 332 patients (387 hip resurfacings) who underwent hip resurfacing between December 1999 and Dec 2012. 11 hips in 11 patients were reported to squeak postoperatively. Each of these patients, except one, were matched by age, sex, BMI and implant to 3 controls. The final patient only had one control due to his high BMI.

The latest post-operative radiographs of the squeaking group and controls were analysed using EBRA (Einzel-Bild-Roentgen-Analysis, University of Innsbruck, Austria) software to evaluate cup inclination and anteversion.


Ching-Jen Wang To Wong

Background:

Massive rotator cuff tear can cause functional disability due to instability and degenerative changes of the shoulder joint. In patients with massive irreparable rotator cuff tear, tendon transfer is often used as the salvage procedure. Latissimus dorsi and pectoris major transfer are technically demanding procedures and may incur complications. The biceps tendon transfer may provide a biologically superior tissue patch that improves the biomechanics of the shoulder joint in patients with irreparable rotator cuff tear. This study evaluated the functional outcomes of biceps tendon transfer for irreparable rotator cuff tear in 6 patients with two years and longer follow-up.

Methods:

Between September 2006 and October 2011, 50 patients with 50 shoulders underwent surgical repair for MRI confirmed rotator cuff tear. Among them, six patients with massive irreparable rotator cuff tear were identified intraoperatively, and underwent proximal biceps tendon transfer to reconstruct the rotator cuff tear. The biceps tendon was tenodesed at the bicipital groove, and the proximal intra-articular portion of the biceps tendon was transected. The biceps graft was fanned out and the distal end fixed to the cancellous trough around the greater tuberosity with suture anchor. The anterior edge was sutured to the subscapularis and the posterior edge to the infraspinatus tendon or supraspinatus if present. Postoperative managements included sling protection and avoidance of strenuous exercises for 6 weeks, and then progressive rehabilitation until recovery.


Ching-Jen Wang

Background:

Full thickness cartilage defect of the knee frequently resulted in fibrous tissue formation, and larger lesions often lead to degenerative arthritis of the knee. Many techniques are designed to repair the cartilage defect including chondrocyte transplantation, microfracture and osteochondral graft. Each method has achieved some success but no universal results. Autologus osteochondral graft has gained in clinical popularity because of its technical feasibility and cost effectiveness.

Purpose:

The purpose of this retrospective study was to evaluate the medium-term results of autologous osteochondral graft for focal contained articular cartilage defects of the knee in 25 patients with 26 knees with 2- to 7-year follow-up


Joseph Ward Brian Hallstrom Aidin Eslam Pour

Purpose:

Two-stage revision is the gold standard treatment for chronic periprosthetic infection of the hip or knee. Implantation of a functional antibiotic spacer allows patients the option of two stage revision or living with the spacer in place. Some patients may be satisfied with the activity level that they attain with the functional antibiotic spacer and may avoid the morbidity of a second surgery.

Methods:

We retrospectively examined the outcomes of 30 joints in 27 patients treated for chronic periprosthetic infection of the hip or knee at a mean follow-up of 27 months (range 11–46 months). Comparing the patients treated with two-stage revision to those patients living with a functional antibiotic spacer, we used University of California Los Angeles activity scores, modified Harris hip scores, and patient satisfaction measures to answer two main questions: (1) Is there a significant difference in activity level? (2) Is there a significant difference in patient satisfaction? Patient satisfaction was measured on a 1–100 scale with 100 being completely satisfied.


William Ward Thomas Rusher Scott Wilson

Background

Irrigation and débridement (I&D), often with exchange of modular polyethylene components, is commonly used to treat acute periprosthetic infection (PPI) following total joint arthroplasty. Two-stage revision, the “Gold Standard” for PPIs' is more invasive, requires more resources, creating controversy over recommended initial treatment of PPIs. This study seeks to determine the success rate of an “intent to treat” approach utilizing I&Ds with progression to two stage revisions as required.

Methods

We retrospectively reviewed 5193 hip and knee joint arthroplasties performed over a 63 month period and identified 46 (20 female, 26 male, mean age 60) deep postoperative (within 365 days) infections that were initially managed with an “intention to treat and cure” I&D, with or without poly exchange. We investigated the overall success rate of this approach and the requirements for additional surgical procedures, as well other associated factors. 34 were managed with I&Ds only and 12 with two stage revisions as well.


Hwa Bok Wee Wesley Flint April Armstrong Gregory Lewis

Introduction:

The mechanical stresses and strains surrounding orthopaedic implants can influence bone resorption and formation, micro-fracture, and consequently implant fixation or loosening. Experimental measurement of these internal parameters is generally not feasible. Computational predictions by finite element modeling are promising, but until recently have been limited to assuming the surrounding cancellous bone as a continuous volume, without modeling individual trabeculae. A recent study demonstrated errors in bone-implant stiffness exceeding 100% when using this continuum assumption [1]. Conversely, recently micro-finite element computer models have been built from high resolution imaging of trabecular bone. In the present study we developed such models of central pegs cemented into cadaveric glenoids. We hypothesized that additional applied cement would lead to stronger implant fixation, but less physiologic strains in the trabeculae.

Methods:

Two cadaveric specimens were implanted, with the applied cement volume in the Specimen 2 approximately double that of Specimen 1. The specimens were imaged by micro-computed tomography (vivaCT 40, Scanco, Switzerland) with a resolution of 12 microns. Images were filtered and resampled, then imported in Mimics (Materialise, Belgium) for semi-automated segmentation and 3D reconstruction based on our laboratory's published methods. Finite element models containing 1.7 to 1.8 million elements having sides of 0.1 mm were generated by a direct image voxel-to-element approach [2] (Fig. 1). The material properties of cement and bone were assumed linear elastic (bone: E = 3.5 GPa, cement: E = 3.0 GPa, and implant (UHMWPE): E = 1.3 GPa), and interfaces were assumed fully bonded. All outer walls of the bone were fixed, and a downward force of 250 N was applied to the implant peg. Simulations were run using Abaqus (Simulia, Pawtucket RI) on a 32-core, 1 TB-memory server at PSU's High Performance Computing Systems.


Chen Weijia Ryuji Nagamine

Objective:

Total elbow joint arthroplasty has limited longevity and is therefore not appropriate for younger rheumatoid arthritis patients. Arthroplasty using an inter-positional membrane may be another surgical option for this population. However, clinical results for joint arthroplasty using the inter-positional membrane have not traditionally been favorable because rheumatoid activity could not be controlled. Today, rheumatoid activity can be controlled with biologics; therefore, the utility of the inter-positional membrane procedure was re-evaluated.

Methods:

An 8×6 cm sheet of fascia was detached from the patient's tensor fascia lata muscle to produce a JK membrane. The fascia was stretched on a frame and kept in a 2% chromic acid potassium solution for 24 hours. Then, the fascia was exposed to direct sunlight in order to reduce the dichromic acid. The fascia was washed out in running water for 24 hours and was then stored in phenol with the addition of 70% alcohol. Elbow arthroplasties were performed on three elbow joints in two young female patients. The first case had a significantly damaged right elbow joint with severe joint dysfunction. A JK membrane arthroplasty was done for the first case in 2003, when this patient was 34 years old. Biologics were administered with methotrexate after the surgery. The second case demonstrated bilateral ankylosed elbows due to idiopathic juvenile arthritis. Bilateral JK membrane arthroplasties were performed in 2010, when this patient was 32 years old. Several operative and manual manipulations were necessary in order to increase the range of motion following surgery. Biologics were administered with cyclosporine.


Chen Weijia Ryuji Nagamine Keiichi Kondo Kei Osano

INTRODUCTION:

In varus knee, posterior cruciate ligament (PCL) release has been reported to result in the increase of the flexion gap without significant effect on the extension gap. However, the effect of release on gap angle is still obscure. On the other hand, gap angle and distance measured with the tension devices may vary due to different distraction forces. In this study, difference of gap angle and distance before and after PCL resection in knee extension and 90° flexion was inspected. Effect of different distraction force on gap was also assessed.

OBJECTIVES:

Fifty cases with medial osteoarthritis undergoing PS-TKA were included in the study. PCL of all the cases were identified intact before resection.


Joel Weisenburger Kevin Garvin Hani Haider

Testing wear durability of UHMWPE joint replacement bearings under abrasive conditions (mimicking in vivo conditions when metallic components become scratched from bone or cement debris) is useful in screening new bearing materials or alternative processing methods. Adding third body particle debris in testing brings the complications of minimal (if any) increase in wear with particles lodging into the plastic bearings potentially causing unknown errors for gravimetric wear measurements. Alternatively, testing those bearings against already scratched metallic components may provide a cleaner route without such complications. This requires a method to reproducibly create scratches resembling the damage seen on retrievals. This study introduces such a method, and investigates wear of UHMWPE bearings against metallic femoral hip components that have been intentionally scratched.

In this technique, femoral hip heads were pressed and sunk into a bed of abrasive beads under a known load (712N, one body weight), and this created longitudinal scratches. Latitudinal scratches were generated by rotating the sunken femoral heads ± 90° about their polar axis while under the same load. This process (pressing into the abrasive beads and then turning ± 90°) was repeated 10 times on each femoral component which resulted in thousands of random scratch patterns, but with statistically repeatable overall severity and similar visually to retrievals (Fig. 1). We then evaluated the technique through a hip wear study.

Twelve UHMWPE liners (40 mm I.D.) were tested against CoCrMo femoral heads on a 12-station hip simulator (AMTI). Liners were three materials: a) Three conventional (GUR1020, gamma-sterilized 3.5 Mrad), b) Three highly cross-linked (HXL) (GUR1020, 10 Mrad, annealed, EtO-sterilized, artificially aged), and c) Six HXL w/vitamin-E (GUR1020, 12 Mrad, annealed, EtO-sterilized, aged). The test comprised three phases. Phase-I: standard clean (non-abrasive, non-scratched) test for 5 Mc; Phase-II: Pulverized PMMA was added to serum at 700 mg/L (to introduce abrasive conditions); however, effects were minimal after 2 Mc (7 Mc total). Phase-III: Femoral heads were scratched using our method. Phase-III lasted for 1 Mc, for a testing total of 8 Mc (ISO-14242-1 waveforms). All specimens were lubricated with bovine serum (37°C, 30g/L protein). Plastic liners were cleaned and weighed at standard intervals, and wear was corrected with active loaded soak controls.

The wear results are shown in Fig. 2. The conventional liners showed the highest wear (Phase-I: 55.7 ± 3.00 mg/Mc, Phase-II: 49.2 ± 0.520 mg/Mc, Phase-III: 124 ± 28.9 mg/Mc) while HXL liners displayed much lower wear (Phase-I: 2.58 ± 0.969 mg/Mc; Phase-II: 4.93 ± 1.22 mg/Mc; Phase-III: 9.92 ± 4.64 mg/Mc). Vitamin-E HXL liners also showed very low wear (Phase-I: 5.97 ± 0.50 mg/Mc, Phase-II: 8.89 ± 1.40 mg/Mc, Phase-III: 11.9 ± 2.70 mg/Mc). Addition of the PMMA powder during Phase-II increased liner wear, but the surfaces did not appear damaged like retrievals. Wear rates between Phase-I and Phase-III doubled due to scratching the femoral heads for all material types, a statistically significant increase (p < 0.05).

Our results confirm that the scratching procedure successfully created a severe wear situation for the bearings. Future work will involve abrasive testing on knee components to determine if the method is successful there too.


Joel Weisenburger Kevin Garvin Hani Haider

Damage to metallic femoral heads can occur in vivo. Testing of hip prostheses under abrasive conditions is one among various efforts needed towards more realistic and harsher testing. Abrasion likely increases both wear and friction at the head/liner interface. This study investigates if our novel friction measurement technique can detect damage to femoral heads during extended wear testing of metal-on-plastic (MOP) THRs of various material combinations using both scratched and as-new femoral heads.

Friction was measured based on equilibrium of forces and moments measured by a 6-DOF load cell on each test station of an AMTI hip simulator. The force and moment data from the load cells was utilized to calculate the frictional torque about each of three rotational axes (flexion/extension, abduction/adduction and internal/external rotation). The frictional torques were transformed to account for the offset in load cell position from the hip center and were then vector summed to yield an overall frictional torque about the femoral head. The friction factor was then computed by dividing the overall frictional torque by the applied compressive load and the femoral head radius. The waveforms specified in ISO-14242-1 were used. Diluted bovine serum at 37°C with 30 g/L protein concentration lubricated the specimens.

Twelve UHMWPE liners (40 mm I.D.) were tested against CoCrMo femoral heads. Liners were of three materials: a) Three conventional (GUR1020, gamma-sterilized 3.5 Mrad), b) Three highly cross-linked (HXL) (GUR 1020, 10 Mrad, annealed, EtO-sterilized, artificially aged), and c) Six HXL w/vitamin-E (GUR 1020, 12 Mrad, annealed, EtO-sterilized, aged).

The test consisted of three phases were as follows:

Phase-I: Standard clean (non-abrasive) test for 5 Mc.

Phase-II: Pulverized PMMA was added to serum at 700 mg/L (to introduce abrasive conditions); however, effects were minimal after 2 Mc (7 Mc total).

Phase-III: Femoral heads were scratched using a technique developed in house to create latitudinal and longitudinal scratches similar to what is seen on retrievals. Phase-III lasted for 1 Mc, for a total of 8 Mc.

The friction results are shown in Fig. 1. Friction factors of the three THR types tested were similar for the first 5 Mc (0.062 ± 0.0084) and increased only marginally after the PMMA powder was added (0.066 ± 0.0066). The PMMA powder did not appear to damage the heads much visually, and therefore the insignificant increase was not surprising. However, once heads were intentionally scratched at 7 Mc, the friction factor rose on all three THR types: a) 0.11 ± 0.0077, b) 0.082 ± 0.0049, c) 0.087 ± 0.022.

This friction technique successfully detected when femoral head damage had occurred. Higher friction was clearly observed after femoral heads had been scratched.


Stephen Murphy William Murphy Samuel Wellman Jens H. Kowal

Introduction:

Cup malposition leads to increased incidences of dislocation, impingement, wear, and revision. The HipSextant navigation system is a smart mechanical navigation device designed to indicate correct cup orientation at surgery. The current study assesses the effect of deliberately mis-docking the device on clinical accuracy.

Methods:

Ten patients (5 men and 5 women) presenting for total hip arthroplasty were assessed. Planning for the HipSextant Navigation System (Surgical Planning Associates, Inc., Boston, MA) was performed as usual. This is done by first creating a 3D surface model from CT imaging, establishing an Anterior Pelvic Plane coordinate system, and then creating a patient-specific HipSextant coordinate system. This coordinate system is defined by three points. The first point, called the basepoint, is located just behind the posterior wall of the acetabulum a fixed distance above the infracotyloid notch. The second point is located on the lateral aspect of the anterior superior iliac spine. The third point is located on the surface of the ilium and equally distant from the other two points. These three points define a patient-specific coordinate system that is known relative to the APP. Clinically, the instrument is then docked according to the plan and two protractors on the top of the instrument allow a direction indicator to point in the direction of desired cup orientation.

For each of the hips, after the HipSextant plan was created (Figure 1), two additional plans were created: one where the basepoint was docked 5 mm closer to and one 5 mm further from the infracotyloind notch. The effect of the deliberate mis-docking was measured in degrees of operative anteversion and operative inclination.


Dustin Whitaker Yenshuo Liao Takayuki Nakamura Catherine Hardaker

Introduction:

Moderately crosslinked polyethylene maintains a balance of wear resistance and mechanical properties. The GVF poly was manufactured from GUR1020 UHMWPE bars, sealed in vacuumed foil package, and gamma sterilized at 4 Mrads. The MARATHON® polyethylene inserts were manufactured from GUR1050 UHMWPE bars, crosslinked by gamma irradiation at 5 Mrad, and followed by a remelting process that eliminates free radicals. The final sterilization method is gas plasma (GP) or ethylene oxide (EtO). Both methods will not introduce free radicals. Previous studies have shown MARATHON polyethylene (GP sterilized) with 83% lower wear than conventional polyethylene in a simulation test [1], compared to a 10-year clinical study that showed 77% wear reduction [2]. There is no study to compare the wear performance of MARATHON (EtO sterilized) and conventional poly.

Materials and Methods:

Four groups of polyethylene inserts (Table 1) were paired with matching femoral heads that were manufactured from CoCrMo (ASTM F1537) with diameters of 28, 32, and 36 mm. The inserts were chosen to have similar thickness at the dome for MARATHON, while for GVF it was the largest head size available.

Wear testing was performed on an AMTI Hip Simulator per the ISO 14242-1 standard [3] at 1 Hz using the described inputs (Table 2), which provide a larger range of motion than the ISO standard. The cups were mounted in accordance with ISO 14242-1 using custom fixturing and secured with cement while the femoral heads were mounted on a vertical taper support. Testing was performed in 25% bovine calf serum at 37 ± 2°C. Wear of the inserts was determined gravimetrically. Finally, wear rates were calculated by linear regression and then compared between the groups using ANOVA analysis (α = 0.05).


Markus Wimmer Chris Knowlton Robin Pourzal Pauline McEwen Thomas Andriacchi

Introduction:

Many variables contribute to aseptic loosening, and the release of wear particles is a predominant source of late failure. It has been difficult to measure TKA wear quantitatively from retrieved devices; hence, there is a relative paucity of clinically observed TKA wear rates in the literature. Additionally, little is known about patient factors influencing wear rates. This study (a) establishes a clinically relevant TKA wear rate for a cruciate retaining TKA design and (b) relate those wear readings to gait measures of their hosts.

Methods:

34 revision- and 11 postmortem-retrieved MG II tibial PE-components were included in the analysis. Wear scars on the articulating surface of the insert were digitized under light microscopy. The geometry of the surfaces was mapped at 100×100 μm using a low-incidence laser. Autonomous mathematical reconstruction of the original surface was used [1], and linear penetration on the medial and lateral surfaces and total wear volume were calculated (Fig-1).

For five implants, gait data recorded during 1.5 years after surgery were available. Gait studies were performed using a three-dimensional optoelectronic system for motion capture. Joint kinematics and kinetics were calculated using a six-marker model of the lower extremity [2]. All knee moments are reported in Nm, acting externally at the tibia. Potential linear relationships between wear and moment characteristics were investigated.


Introduction

Conventional total knee instrumentation is used for most total knee replacements. Computer-assisted total knee arthroplasty (CA-TKA) including custom guides has gained popularity due to its reported accuracy in restoring optimal alignment. CA-TKA has demonstrated increased surgical time and cost, with know risks of pin-site infection and fracture. We assessed the radiographic alignment of conventional TKA by one surgeon and determined whether preoperative alignment has an effect on postoperative alignment.

Methods

A prospective series of 100 primary total knee arthroplasties (in 95 patients) from 1/2012-3/2013 were performed by the senior author, using a single conventional instrument system and a consistent methodology of 5° valgus distal femoral cut, intramedullary femoral entry-point, and minor cement balancing. Mechanical axis and component alignment were measured digitally on preoperative and postoperative lower extremity scanograms. Target alignment was set at neutral ± 3°. Knees with preoperative deformity within 0 ± 5° (non-deformed group) and those with >5° varus/valgus (deformed group) were compared using chi-square test.


Erik Woodard William Mihalko John Williams John Crockarell

Introduction:

Soft tissue balancing is a part of every total knee arthroplasty (TKA) surgery. Traditionally, balancing the varus knee has been approached by releasing portions of the medial soft tissue sleeve in a sub-periosteal nature off of the proximal tibia, but this may lead to undue laxity or residual pain about the area the release was performed. More recently, “pie crusting” of the medial soft tissue sleeve has been used to balance the varus knee without compromising the structural integrity of the ligament. This technique may provide advantages over a sub-periosteal release by targeting only medial tight bands that can be palpated with the capsule distracted in 90 degrees of flexion and full extension. This study aims to biomechanically validate the pie crusting technique of the medial soft tissue sleeve and compare the results to those of standard medial releases that have been previously reported.

Methods

Six cadaveric TKA specimens were retrieved through the Medical Education and Research Institute (Memphis TN). For each specimen tested, the skin and muscle tissue was removed, and the femur and tibia were cut transversely 180 mm from the joint center. Specimens were fixed in extension in a custom knee testing platform (Little Rock AR) and subjected to a 10 Nm varus and valgus torque. The angle at which these moments occurred was recorded, and each test was repeated for 0, 30, 60, and 90 degrees of flexion. After tests were performed on TKA specimens, a fellowship trained orthopedic surgeon performed “pie crusting,” making alternating stab patterns with a number 11 scalpel blade along the anterior half of the superficial medial collateral ligament (SMCL) or posterior half of the SMCL including the posterior oblique ligament (POL). Three specimens had the anterior capsule pie crusted first and three had the posterior pie crusting performed first, followed by complete pie crusting. After two stages of pie crusting, the medial soft tissue sleeve was released off of the proximal tibia in a sub-periosteal fashion for comparison. Laxity was defined as the angles at which valgus torque equaled 10 Nm. Any increase or decrease in laxity was referenced to the normal TKA laxity.


Erik Woodard William Mihalko John Crockarell John Williams

Introduction:

Repair of the arthrotomy is a performed at the end of every total knee arthroplasty (TKA). After the arthrotomy is performed, most surgeons attempt to close the arthrotomy with the medial and lateral edges anatomically approximated. If no landmarks are made prior to performing the arthrotomy however, there is a risk that anatomic approximation may not be obtained. This study looked into the biomechanical changes in stiffness of the knee before and after a medial parapatellar approach repaired with an anatomic, and shifted capsular repair with the medial side of the arthrotomy shifted up or down when repaired to determine if capsular closure may have an effect on the stiffness of the joint.

Methods:

Fourteen cadaveric TKA specimens were retrieved through the Medical Education and Research Institute (Memphis TN). For each specimen tested, the skin and muscle tissue was removed, and the femur and tibia were cut transversely 180 mm from the joint center. Specimens were fixed in extension in a custom knee testing platform (Little Rock AR) and subjected to a 10 Nm varus and valgus torque and a 1.5 Nm internal and external rotational torque. The angle at which these moments occurred was recorded, and each test was repeated for 0, 30, 60, and 90 degrees of flexion. After tests were performed on retrieved TKA specimens, a fellowship trained orthopedic surgeon vented the knee capsule by making an incision with a number 10 scalpel blade in a horizontal nature to provide a landmark for anatomic reapproximation. Tests were repeated as before, after which the surgeon performed a standard arthrotomy and repaired it using #0 suture and a neutral alignment. Sutures were cut and the repair was repeated using upward 5 mm shift and downward 5 mm shift of the medial side of the arthrotomy during the repair. All tests were repeated after each repair technique. Any increase or decrease in laxity after capsule repair was referenced to the TKA laxity tested prior to an arthrotomy being performed.


Sherrod Woods Elizabeth Hippensteel Chase Maag

Statement of Purpose:

The wear rate of Ultra High Molecular Weight Polyethylene (UHMWPE) in joint replacements has been correlated to both contact area and contact stress in the literature, [1], [2]. In both publications and our experiment, UHMWPE articulated with a polished surface of cobalt-chromium alloy was evaluated using a Pin-On-Disk (POD) apparatus (AMTI) implementing bi-directional movement.

In publication [1], volumetric wear was independent of normal load and dependent upon increasing contact area. The results demonstrated that increasing contact stress decreased wear rates twofold. In publication [2], at maximum cross-shear, wear was proportional to nominal contact area and wear factors normalized to area are more appropriate than load based wear factors. In both studies, the contact surface areas of the POD pins were reduced by decreasing the diameters of the POD Pins.

In our experiment, the contact area was dependent on textured POD Pin 390 (T390) which had low wear [3]. T390 reduced the normal POD contact area from 71 mm2 to 8.26 mm2. Hydroxylapatite (HA) particles were introduced to the serum to simulate third body wear debris. We hypothesized that the normal POD Pins would have greater wear rates than the textured POD Pins. A measurement of 0.14 mg HA particles per 250 mL of serum was used for each test 0.33 million cycles.

Methods:

The GUR 1020 resin XLK POD Pins were gamma irradiated to 50 kGy in a vacuum package and then remelted. Three (3) T390 POD pins and nine (9) untextured XLK POD Pins were used. Three untextured XLK POD Pins were tested against three T390 POD pins. The other six (6) untextured XLK POD Pins were used as soak controls. Each pin articulated against a polished, high carbon wrought CoCr metal alloy counterface (ASTM F1537; diameter = 38.1 mm; thickness = 12.7 mm). Wear rate tests were for 1.98 million cycles. In order to perform the t-test analysis, the wear rates for each pin were given by the slope of the linear regression line through the individual data points (cycle count, cumulative wear), excluding the (0, 0) point.


Timothy Wright Kirk Gunsallus Joseph Lipman Robert Hotchkiss Mark P. Figgie

Implant designs for hip and knee arthroplasty have undergone a continual improvement process, but development of implants for total elbow arthroplasty (TEA) have lagged behind despite the marked mechanical burden placed on these implants. TEA is not as durable with failure rates approaching thirty percent at five years. The Coonrad-Morrey (Zimmer, Warsaw, IN), a linked design, remains the standard-bearer, employing polyethylene bushings through which a metal axle passes. A common failure mode is bushing wear and deformation, causing decreased joint function as the bushing-axle constraint decreases and osteolysis secondary to release of large volumes of wear debris.

Improving upon this poor performance requires determining which factors most influence failure, so that failure can be avoided through design improvements. The approach integrates clinical observations of failed TEAs with implant retrieval analysis, followed by measurements of loads across the elbow for use in stress analyses to assess the performance of previous designs, and, finally, new design approaches to improve performance.

Examination of the clinical failures of more than seventy Coonrad-Morrey TEAs revealed patterns of decreased constraint and stem loosening. Implant retrieval analysis from more than thirty of these cases showed excessive bushing deformation and wear and burnishing of the fixation stems consistent with varus moments across the joint.

To determine loads across the elbow, motion analysis data were collected from eight TEA patients performing various activities of daily living. The kinematic data were input into a computational model to calculate contact forces on the total elbow replacement. The motion that produced the maximum contact force was a feeding motion with the humerus in 90° of abduction. For this motion, the joint reaction forces and moments at the point of maximum contact were determined from a computational model.

We applied these loads to numerical models of the articulating bushings and axle of the Coonrad-Morrey to examine polyethylene strains as measures of damage and wear. Strain patterns in response to the large varus moment applied to the elbow during feeding activities showed extensive plastic deformation in the locations at which deformation and wear damage were observed in our retrieved implants (Fig. 1).

Finally, we examined a new semi-constrained design concept intended to meet two goals: transfer contact loads away from the center of the joint, thus allowing contact to provide a larger internal moment to resist the large external varus moment; and reduce polyethylene strains by utilizing curved contacting surfaces on both the axle and the bushings (Fig. 2). After a sensitivity analysis to determine optimal dimensional choices (e.g., bushing and axle radii), we compared the resulting polyethylene strains between the Coonrad-Morrey and new design at locations that experienced the largest strains (Fig. 3). Substantial decreases were achieved, suggesting far less deformation and wear, which should relate to marked improvements in performance.

Currently, we are incorporating this new design concept, along with alterations in stem design achieved from examination of load transfer at the fixation interfaces based on the same loading conditions, to achieve an implant system intended to improve the performance of TEA.


Thomas Wright Bryan Conrad Aimee Struk

Introduction:

The subscapularis muscle experiences significant strain as it accommodates common movements of the shoulder. Little is known about what happens with this obligatory strain once the subscapularis insertion is disrupted and repaired in the course of shoulder arthroplasty. Subscapularis failure is a serious known complication after shoulder arthroplasty. It is not known what the effect of increasing the thickness of the shoulder head will have on subscapularis strain. It is our hypothesis that the use of large or expanded humeral heads during shoulder replacement will cause increased tension in the repaired subscapularis. The primary purpose of this study was to identify the optimal manner to perform a passive range of motion (PROM) program without invoking a significant increase in strain in the repaired subscapularis. The secondary purpose was to determine the impact of varying the thickness of the humeral head on subscapularis strain using the same PROM protocol.

Methods:

Eight fresh-frozen, forequarter cadaver (four female, four male) specimens were obtained following IRB approval. An extended deltopectoral incision was performed so that the subscapularis insertion site could be well visualized. PROM exercises with the following motions were evaluated: external rotation, abduction, flexion and scaption. An optical motion analysis system was used to measure strain in the subscapularis. The same measurement protocol was repeated after performing a subscapularis osteotomy and after placement of an anatomic hemiarthroplasty of three different thicknesses (short, tall, expanded).


Sally Wright John Hollingdale Jasvinder Kandola

Total knee replacement (TKR) is an established treatment for end stage joint disease of the knee. Trabecular metal is one of the design experiments seeking to improve the bone-implant interface and wear patterns in order to increase the longevity of primary joint replacements and reduce the revision burden. Uncemented implants retain bone stock, reduce third body wear, and require a shorter operative time. Although only 4% of knee replacements currently being implanted are uncemented TKRs, there has been considerable recent interest in uncemented designs with a hope of improving the survival time of primary implants. National Joint Registry data has been less favourable of uncemented designs thus far. We report our experience with these comparative implants and present our functional and radiological mid-term results.

Trabecular metal is made of tantalum. It has an interconnecting 3-dimensional lattice structure which is 80% porous. It closely resembles the microstructural architecture of cancellous bone. Bone grows into the porous structure creating a strong bond between bone and implant. In this design, the tibial pegs are seated in a peripheral position, in denser cancellous bone when compared with a central peg. Tantalum offers an appropriate modulus of elasticity, reducing the likelihood of component lift-off and stress shielding.

Over a 4.5 year period, between April 2007 and December 2011, 132 knees in 127 patients with a diagnosis of end stage osteoarthritis, underwent TKR at a single hospital (CMH), performed by a single surgeon (JH). All surgeries were performed with a thigh tourniquet, medial parapatellar approach, antibiotic and VTE prophylaxis, patellar resurfacing, and rapid recovery rehabilitation. 86 cemented TKRs in 78 patients (mean age 76 years), and 66 uncemented TKRs in 49 patients (mean age 68 years). All components were standard NexGen (Zimmer) implants. Follow-up was a mean of 40 months (range 6–87 months).

We analysed the patient postoperative routine standing and recumbent anterior-posterior and lateral radiographs using the knee society TKA scoring system. All linear measurements were made using a PACS viewing system and analysed by 2 of the authors independently. There was no significant radiological lucent lines, and no single KSS > 4. Patients completed Oxford Knee Scores and Knee Society Scoring questionnaires to evaluate their functional outcomes. The mean OKS was 41, and KSS 89. In this period there were revisions in 3 cemented prostheses and 2 uncemented prostheses. 2 revisions were for infection, 2 for peri-prosthetic fracture following trauma, and 1 for unexplained pain.

The uncemented TKR performs equally as well as its cemented counterpart in our experience, both clinically and radiologically, at mid-term follow-up of up to 7 years (mean 3.3 years).


Daniel Choi Timothy Wright

Retrieval analysis has been valuable in the assessment of in-vivo surface damage of orthopedic devices. Historically, subjective techniques were used to grade damage on the implant's surface. Microscopy improved the ability to localize and quantify damage, but cannot measure volumetric wear due to this damage. Laser scanning provides volumetric wear, but lacks image data. Recent techniques superimpose image data on laser scan data (photorendering) and combine the strengths of both methods. Our goal is to use such methods to improve our damage assessment and potentially correlate this assessment to volumetric wear.

This project focused on two areas: image-stitching and photorendering. Image-stitching registers multiple images into large-scale high-resolution composites. Six total disc replacement components were imaged with a digital microscope (Moticam 2, Motic). Three sets were taken of each component: a single template at 10x zoom (1×1), a 4-image composite at 18x zoom (2×2), and a 9-image composite at 18x zoom (3×3). The 2×2 and 3×3 sets were image-stitched to resemble their template counterpart. Measurement error was defined using common pixels identified between the composite and template images for comparison with a semi-automated feature detection algorithm (Figure 1).

For photorendering, a pilot study was performed on a single retrieved tibial bearing. The component was imaged with a digital microscope (VHX-2000, Keyence) under a 3D image-stitching setting, providing a high-resolution photo embedded with height values. MATLAB was used to convert the image into a photo-rendered point cloud approximating the surfaces. The component was then laser scanned, creating a 3D point cloud with resolution 0.127 mm. The photo-rendered point cloud data was registered to the laser scan data using an iterative closest point algorithm (Geomagic Studio, Geomagic).

An analysis of all composite images showed a mean error of 0.221 mm. Figure 2 compares regions of images for the template, 2×2, and 3×3 composites. Zooming in shows the effect of the increased resolution contained in the composite. The 2×2 and 3×3 composites had mean errors of 0.231 mm and 0.209 mm, respectively; these were not significantly different. Comparisons among image types showed that components with less features exhibited larger errors during image-stitching. Figure 3 shows images resulting from each step of the photorendering process. The final image of the figure shows a qualitative result of our ability to photorender the tibial bearing surface of the component.

While combining microscopy and laser scan data works anecdotally, further analyses must be performed to assure the robustness of the technique. The digital microscope's embedded image-stitching software is limited in its maximum field of view; we look to extend this by taking multiple scans and using in-house software to generate a composite of a whole implant. The improved resolution provided by microscopy offer an opportunity to automate damage assessment, yielding damage mapped images which can also be overlaid on laser scan data. This may provide a means to better quantify observed damage and yield meaningful correlations with volumetric loss due to wear.


Chandra Shekhar Yadav Ashok Kumar Devdutta Neogi Samarth Mittal Vivek Shankar

Background:

Is routine use of suction drain after joint replacement is justified.

Material & Methods:

Prospective evaluation was done to compare the effects of postoperative suction drain in 56 patients with no postoperative drain in 56 patients, undergoing total knee arthroplasty at our institute. Patients having severe systemic diseases, disturbed liver function, obesity, unstable diabetes and coagulation disorders were excluded from the study. Comparative evaluation was done for the blood loss, no of units of blood transfusion, wound hematoma, wound healing, duration of hospital stay, pain and range of motions.


Chandra Shekhar Yadav Sumit Banerjee Ashok Kumar Devdutta Neogi Samarth Mittal Vivek Shankar

Background:

Modified posterior approach and its effect on stability and functional outcome in total hip arthroplasty.

Material & Methods:

A retrospective comparative evaluation was done to assess the functional outcome and rate of dislocation in 233 hips (Group A) operated before 2007 by convention posterior approach and 567 hips (Group B) were operated by modified posterior approach.(2007–2011) In this modified posterior approach technique, 2–3 stay sutures (non-absorbale Nylon) are applied in the piriformis tendon, short external rotator and proximal part of Quadratous muscle. Then a conjoint- myocapsular sleeve is raised by starting cutting (with cautery) linearly over the capsule with adherent fibers of gluteus minimus to piriformis tendon, short rotators and part of quadratus to expose and dislocate the head. After inserting the definite prosthesis, upper part of sleeve (capsule, piriformis tendon) is sutured with same nonabsorbable Nylon at the lower part of tip of greater trochanter by passing through the bone with needle or by drilling the bone; lower part of the sleeve is tied with lateral trochanteric bone. Additional stability to repair was given by closing the tendinous part of the gluteus maximus by horizontal cross mattress sutures up its attachment to the proximal femoral shaft.


Takaharu Yamazaki Ryogo Kamei Hideki Yoshikawa Kazuomi Sugamoto

Purpose:

To materialize 3D kinematic analysis of total knee arthroplasty (TKA), 2D/3D registration techniques, which use X-ray fluoroscopic images and the knee implants CAD, have been applied to clinical cases. However, most conventional methods have needed time-consuming and labor-intensive manual operations in some process. In previous study, we addressed a manual operations problem when setting initial pose of implants model for 2D/3D registration, and reported a semi-automated initial pose estimation method based on an interpolation technique. However, this method still required appropriate initial pose estimation of the model with manual operations for some X-ray images (key frames). Additionally, in the situation like fast knee motion and use of low frame rate, good registration results were not obtained because of the large displacement between each frame silhouette. To overcome these problems, this study proposes an improved semi-automated 3D kinematic estimation method.

Methods:

Our 2D/3D registration technique is based on a robust feature-based algorithm. In improved initial pose estimation method, for the only first frame, the initial pose is manually adjusted as close as possible. That is, we automatically estimate appropriate initial pose of the model for X-ray images except for the first frame.

To automatically estimate the initial pose of the model, we utilize a transformation with feature points extracted from the previous and next frames. A transform matrix which has three DOF (translations parallel to the image, and a rotation perpendicular to the image) is calculated by registration of corresponding feature points between the previous and next frame extracted with SURF algorithm. While, the corresponding point sets extracted by SURF sometimes include some error sets. Therefore, in this study, LmedS method was employed to detect the error corresponding sets and calculate a transform matrix accurately. In Fig. 1(a) and (b), the orange square shows the region defined with the boundary box of the model, and some lines show the combined corresponding point sets. The blue lines are correct corresponding point sets, and the pink lines are error corresponding point sets detected with LmedS method.

Finally, 3D pose of the model estimated in previous frame is transformed with accurately calculated transform matrix, and the transformed pose is used as an initial 3D pose of the model in next frame.


Masaaki Maruyama Kazushige Yoshida Kazumi Kitagawa

We reported a case of the acetabular depression fracture in conjunction with a central fracture dislocation of the hip that was treated with a unique surgical technique.

CASE REPORT:

A 76-year-old man suffered a left acetabular fracture with severe left hip joint pain and walking disability. Acetabular fracture was not apparent on the initial radiographs including anteroposterior and oblique views of the pelvis. However, computed tomography (CT) scanning showed displaced acetabular depression fracture (a third fracture fragment) in the center of the weight-bearing area with fracture of the ilium and spontaneous reposition of central dislocation of the hip (Fig. 1, 2). It seemed that this fracture fragment created incongruity of the acetabular articular surface and the potential for hip joint instability. Therefore, the patient was treated with open reduction and internal fixation.

SURGICAL TECHNIQUE:

To perform the procedure, the patient was placed in the lateral decubitus position. A direct lateral approach to the hip was used for exposure. The vastus lateralis was released 1 cm distal from its origin, trochanteric osteotomy was done by the Gigli saw. To observe the hip articular surface and to identify the fracture fragment, the femoral head was posterior dislocated with excision of teres ligamentum after T-shaped capsulotomy. The depressed fragment in the acetabulum was identified under direct vision but could not be reduced. Therefore, the outer cortex of the ilium was fenestrated in a size of 2 × 2 cm so that a 1-cm-wide levator was inserted to the depressed fragment at 2 cm proximal from the hip articular surface through the fenestrated window (Fig. 3). Subsequently, the displaced bone fragment was pushed down by using the levator to the adequate articular joint level. The fragment was stabilized with packed cancellous bone graft harvested from the osteotomized greater trochanter. The removed outer cortex of the ilium from fenestrated site was repositioned and fixed by a reconstruction plate and screws. The osteotomized greater trochanter was reattached and fixed with two cannulated cancellous hip screws.


Shinji Yoshioka Yoshiji Kanematsu Norio Yamamoto Hibino Naohito Masami Takahashi Henmi Tatsuhiko

We report an intertrochanteric fracture in a patient who had undergone hip arthrodesis 30 years previously. A 53-year-old man was injured in a head-on car crash and was referred to our hospital for treatment. Plain radiographs showed an intertrochanteric fracture of the right proximal femur and deformity of the right hip joint. He had undergone hip arthrodesis surgery 30 years previously at another hospital. Computed tomography scan showed marked atrophy of the gluteus and iliopsoas muscles. He preferred undergoing total hip arthroplasty (THA) to internal fixation. THA was performed using the anterolateral approach with the patient in the supine position as he had undergone hip arthrodesis through the Smith–Petersen approach, and we were concerned about damaging the gluteus muscle and dislocation if we took the posterolateral approach. The femoral head was removed using curved chisels under fluoroscopy. A cementless THA (J Taper stem, Aquala polyethylene liner; Kyocera Medical Corporation, Osaka, Japan) was inserted and fixed appropriately. Full weight-bearing using a walking frame was allowed 2 weeks after the surgery. Six months after the operation, he was able to walk independently and had good range of movement of the hip joint but continued to have weakness in the abductor muscles.

Very few cases of proximal femur fracture in a previously arthrodesed hip have been reported. Manzotti et al. reported a similar case but they performed open reduction and internal fixation. No previous reports in the literature describe THA for intertrochanteric fracture in an arthrodesed hip. The conversion of an arthrodesed hip to THA is technically challenging. It has a high risk of complications such as nerve injuries and hip instability. We were able to treat the patient successfully, but surgeons should carefully decide the treatment method depending on the case.


Scott Banks Lawrence D Dorr Zhinian Wan Zenan Zhang Nicholas Dunbar

Introduction

There is great interest in technologies to improve the accuracy and precision in placing implants for total hip arthroplasty (THA). Malik et al. (J Arthroplasty, 2010) showed that an imageless navigation system could be used to produce accurate measures of acetabular cup alignment compared to a CT-based alignment method using an imaging phantom. In this study we sought to compare the precision of an image-based navigation system with post-operative CT scans in a clinical patient cohort who received navigation-assisted THA.

Methods

Eighteen patients with 20 hips consented to this IRB-approved analysis of intra- and post-operative THA cup alignment. All patients received THA with image-assisted alignment (MAKO Surgical, Fort Lauderdale). Nominal cup placement, subject to intraoperative surgeon adjustment and approval, was 40° radiographic inclination (RI) and 20° radiographic anteversion (RA) according to the definitions of Murray (JBJS-Br, 1993). Intraoperative cup alignment was measured by collecting five points on the cup rim with an optically tracked stylus. Postoperative cup alignment was measured by registering pre- and post-operative pelvic models generated from CT scans, and determining the postoperative cup orientation relative to the pre-operative pelvis coordinate system (Figure 1). Repeated measures testing of the CT-based measurements on 10 patient scans showed precision and bias of 0.7° and 0° for radiographic inclination, and 0.6° and 0.1° for radiographic anteversion.


Hanbing Zhou Joshua Shaw Xinning Li

Introduction:

Due to improvement in overall prosthesis designs and surgical methods, there have been increasing numbers of total ankle arthroplasty performed with encouraging intermediate results. While European registries have been able to perform long term follow-ups and analysis on total ankle arthroplasty patients, majority of the US studies have been based on experiences at a single institution. There is currently limited data on the recent trends of total ankle arthroplasty. The purpose of our study is to evaluate the in-patient demographics, complications and readmission rate in patients after total ankle arthroplasty at academic medical centers in United States.

Patients & Methods:

We queried the University Healthsystems Consortium (UHC) administrative database from 2007 to 2011 for patients who underwent total ankle arthrolasty by ICD-9 procedure code 81.56. A descriptive analysis of demographics was performed, followed by a similar analysis of patient clinical benchmarks, including hospital length of stay, hospital direct cost, in-hospital mortality, and 30-day readmission rates.


Thomas Zumbrunn Kartik Mangudi Varadarajan Harry E Rubash Guoan Li Orhun Muratoglu

INTRODUCTION

ACL retaining (BCR) Total Knee Arthroplasty (TKA) provides more normal kinematics than ACL sacrificing (CR) TKA. However, in the native knee the ACL and the asymmetric shape of the tibial articular surface with a convex lateral plateau are responsible for the differential medial/lateral femoral rollback (medial pivot). Therefore, the hypothesis of this study was that an asymmetric biomimetic articular surface together with ACL preservation would better restore native knee kinematics than retention of the ACL alone. Normal knee kinematics from bi-planar fluoroscopy was used to reverse engineer the tibial articular surface of the biomimetic implant. This was achieved by moving the femoral component through the healthy knee kinematics and removing material from a tibial template.

METHODS

LifeModeler KneeSIM software was used to analyze a biomimetic BCR implant (asymmetric tibia with convex lateral surface), a contemporary BCR (symmetric shallow dished tibia) and a contemporary CR (symmetric dished tibia) implant during simulated deep knee bend and chair sit. Components were mounted on an average bone model created from Magnetic Resonance Imaging (MRI) data of 40 normal knees. The soft-tissue insertions were obtained from the average knee model and the mechanical properties were obtained from literature. Femoral condyle center motions relative to the tibia were used to compare different implant designs. In vivo knee kinematics of healthy subjects from published literature was used for reference.


Thomas Zumbrunn Kartik Mangudi Varadarajan Harry E Rubash Guoan Li Orhun Muratoglu

INTRODUCTION

Contemporary PCL sacrificing Total Knee Arthroplasty (TKA) implants (CS) consist of symmetric medial and lateral tibial articular surfaces with high anterior lips designed to substitute for the stability of the native PCL. However, designs vary significantly across implant systems in the level of anteroposterior constraint provided. Therefore, the goal of this study was to investigate kinematics of two CS designs with substantially different constraint levels. The hypothesis was that dynamic knee simulations could show the effect of implant constraint on kinematics of CS implants.

METHODS

LifeModeler KneeSIM software was used to analyze contemporary CS TKA (X) with a symmetric and highly dished tibia and contemporary CS TKA (Y) with a symmetric tibia having flat sections bounded by high anterior and posterior lips, during simulated deep knee bend and chair sit. The flat sections of CS-Y implant are designed to allow freedom prior to motion restriction by the implant lips. Components were mounted on an average knee model created from Magnetic Resonance Imaging (MRI) data of 40 normal knees. Relevant ligament/tendon insertions were obtained from the MRI based 3D models and tissue properties were based on literature values. The condyle center motions relative to the tibia were used to compare the different implant designs. In vivo knee kinematics of healthy subjects from published literature was used for reference.


Thomas Zumbrunn Kartik Mangudi Varadarajan Michael Duffy Harry E Rubash Henrik Malchau Andrew Freiberg Orhun Muratoglu

INTRODUCTION

Femoral head diameter has a major influence on stability and dislocation resistance of the hip joint after Total Hip Arthroplasty (THA). Dual Mobility (DM) implants can also reduce the risk of dislocation due the large diameter mobile liner which forms the femoroacetbular articulation. However, recent studies have shown that large head prostheses can directly impinge against native soft tissues, particularly the iliopsoas, leading to anterior hip pain. Dual mobility systems have emerged as a revision option in the treatment of failed metal on metal devices because of the high incidence of post revision instability secondary to abductor loss and need for capsulectomy. We hypothesized that an Anatomically Contoured Dual Mobility (ACDM) liner could provide joint stability while better accommodating the soft tissues surrounding the hip joint.

METHODS

The dislocation resistance of a 44 mm ACDM implant was compared to that of a 44 mm conventional DM liner. Both implants consisted of a 28 mm inner small diameter head and the liner was abducted to be in the worst case position for dislocation (Fig. 1). The ACDM liner was based on a 44 mm sphere with smaller radii used to contour the peripheral region below the equator of the liner. MSC Adams was used for dynamic simulations based on two previously described dislocation modes: (A) Posterior dislocation (at 90° hip flexion) with internal rotation of the hip and a posterosuperior directed joint force; (B) Posterior dislocation (starting at 90° flexion) with combined hip flexion and adduction and a posteromedial force direction (Fig. 2). Impingement-free motion (motion without neck impingement against the acetabular cup) and jump distance (head separation from acetabulum at dislocation) were measured for each implant. The acetabular cup was placed at 42.5° abduction and 19.7° anteversion, while the femoral component was anteverted by 9.75° based on published data.


Thomas Zumbrunn Kartik Mangudi Varadarajan Michael Duffy Harry E Rubash Henrik Malchau Andrew Freiberg Orhun Muratoglu

INTRODUCTION

Femoral head diameter has a major influence on stability and dislocation resistance after Total Hip Arthroplasty (THA). Although routine use of large heads is common, several recent studies have shown that contemporary large head prostheses can directly impinge against native soft tissues, particularly the iliopsoas which wraps around the femoral head, leading to refractory anterior hip pain. To address this, we developed a novel Anatomically Contoured large diameter femoral Head (ACH). We hypothesized that anatomical contouring of the ACH implant for soft tissue relief would not compromise dislocation resistance, and the ACH implant would provide increased stability compared to small heads.

METHODS

In this study the dislocation resistance of a 36 mm ACH was compared to that of 28 mm and 36 mm contemporary heads. The ACH implant was based on a 36 mm sphere with smaller radii used to contour the peripheral region below the equator of the head. MSC Adams was used for dynamic simulations based on two previously described dislocation modes: (A) Posterior dislocation (at 90° hip flexion) with internal rotation of the hip and a posterosuperior directed joint force; (B) posterior dislocation (starting at 90° flexion) with combined hip flexion and adduction and a posteromedial force direction (Fig. 1). Impingement-free motion (motion without neck impingement against the acetabular liner) and jump distance (head separation from acetabulum prior to dislocation) were measured to evaluate the dislocation risk of each implant. The acetabular cup was placed at 42.5° abduction and 19.7° anteversion, while the femoral component was anteverted by 9.75° based on published data.


Hani Haider John Sperling Thomas Throckmorton

As reverse total shoulder arthroplasty (RTSA) systems expand with longer durations in vivo, so does the concern and potential complications of wear, debris and osteolysis. Despite some other profound attempts, no wear testing method has stood out to compare implants across systems and labs. The main reasons may have been the diverse sources of forces and motions used in testing, widely different wear amounts which resulted and the general lack of dedicated shoulder simulators. To add a dedicated shoulder simulator to hip and knee simulators would burden the resources of any testing lab. In this study we propose a shoulder wear test method which addresses the above.

Harnessing the wealth of force-motion data from telemetrized shoulder implants from the Bergman's group in Berlin, we synthesized their results to devise a wholistic multi-axes simulation regime for reverse shoulders. The alignment and motions of the humeral cup and the glenosphere were kept anatomically correct (relative to each other) and yielded a physiologically realistic wear-inducing articulation. However, we opted for a very unusual installation/orientation of the whole implant system to allow a twelve station AMTI (hip) simulator to be adapted for this study. The shoulder constructs were aligned with novel fixtures such that the machine's vertical compressive force mimicked the average forces of the shoulder found from the in vivo telemetry data in magnitude and nominal direction. Aligned thus, a patient with a shoulder installed would neither stand, nor lie down, but be oriented in a composite angle relative the simulator original axes. Each anatomic shoulder motion would be achieved by unique computed combinations of the three simulator motion actuators, none of which would be aligned anatomically for the shoulder on its own.

The maximum ranges of cyclic shoulder motion achieved with the constraints of the simulator were 38°–79° of forward elevation repeated in two separate (15°and 45°) elevation planes. The change of elevation plane inherently involved abduction-adduction motion, and simultaneously also involved variation of internal-external rotation within a 57° range. Each elevation rise (twice per cycle) was also accompanied by a sinusoidally rising and falling compressive load in the range 50N–1700N.

The test method was tested (!) by simulating for 2.5 million of the above (double-elevation) cycles and gravimetrically measuring wear of twelve 36 mm size RTSA systems. We compared six systems having vitamin E-infused highly cross-linked polyethylene bearings (100 kGy radiation) to six controls with a medium cross-linked polyethylene of half the radiation dose. Significant wear resulted for the control bearing material (average 17.9 ± 0.851 mg/MC) which was no less than many hips and knees. Multiply (and statistically significantly, p < 0.001) less average wear (3.42 ± 0.22 mg/MC) resulted for the highly cross linked bearings.

The above demonstrated the effectiveness of the test method. Significant wear resulted under physiologically realistic cyclic motion and forces with strong discrimination between two systems whose bearing materials were known to be different in resilience to wear. Using novel fixtures and unusual orientation to utilize a standard commercially available joint simulator promises efficacy of the test method and utility across different labs.