Methods

Impaction data was collected from experienced shoulder surgeons (n=5) during a cadaver lab. Testing groups (n=5 each) were: 1) small ceramic, 2) big ceramic, 3)small metal and 4) large metal. Twenty centric, anatomic humeral heads (DJO surgical, Vista, CA, TURONTM, material: CoCrMo or BIOLOX®delta, size: 38×14mm or 54×22mm) were paired with a corresponding humeral neck (TURON™, DJO surgical, type: neutral modular, material: CoCrMo). Each taper was always used with the same humeral head throughout testing.

The impaction force sequence was recorded using an instrumented impactor (Piezo sensor, model 208 C05, PCB PIEZOTRONICSINC, Depew, NY, ±1%). The surgeons impacted all samples into the cadaver using their typical pattern of hammer strikes (Figure 1). The engaged humeral head and taper were removed by hand and then disengaged using an instrumented (U93, HBM, Darmstadt, Germany, load limit: 5kN) hand-held pulloff-device.

Statistics and data analysis were performed in MATLAB (2014b, Mathworks, Natick, MA, α=0.05). Two-tailed, pearson's linear correlation coefficients are reported. Group differences were determined using Kruskal Wallis test. Pair-wise comparisons were performed using a Tukey correction.

Results

Extremely high and variable impaction forces were measured (Table 1, Figure 2). The maximum force was nearly 27 kN; however, that value reduced to ∼18kN when the data from an outlier surgeon was removed. Maximum impaction forces were 12.45±4.36 kN, and the average was 10.47±3.63 kN. The pulloff force ranged from 0.94 kN to 5.54 kN with an average of 2.76±1.19 kN. Higher impaction forces required higher pulloff forces to disengage the taper connection (p<0.001, R>−0.608).

Ceramic humeral heads showed a 24% higher fixation strength (p=0.004) under similar engagement conditions (p=0.18) in comparison to metal components.

Head size does not appear to influence either the magnitude of the impaction force surgeons use (p>0.20) nor the force needed to disengage the taper (p=0.25).

The surgeon performing the insertion had a significant influence on the impaction strike timing (p<0.001), number of strikes (p<0.001), and the impaction forces (p<0.03) and the pulloff force (p<0.001).

Introduction

Wear and survival of total joint replacements do not depend on the duration of the implant in situ, but rather on the amount of its use, i.e. the patient's activity level [1]. With this in mind, the present study was driven by two questions: (1) How does total knee replacement (TKR) respond to the simulation of daily highly demanding activities? (2) How does implant size affect wear response of total knee replacement (TKR)?

Materials & Methods

Two sets of the same total knee prosthesis (TKP), different in size (#2 and #6), equal in design, were tested on a three-plus-one knee joint simulator for two million cycles using a highly demanding daily load waveform [2], replicating a stair-climbing movement. The results were compared with two sets of TKP previously tested with the ISO level walking task. Gravimetric and micro-Raman spectroscopic analyses were carried out on the polyethylene inserts. Visual comparison with in vivo explants was carried out and digital microscopy was used to characterize the superficial structure of all the TKPs and explanted components.

Introduction

Total knee arthroplasty (TKA) is a consolidated orthopaedic procedure and success of such operation depends on the prosthetic design [1]. Unfortunately, as there is a good survival rate of primary TKA, failures occur for factors concerning the polyethylene composition of the implants, secondary osteolysis, and ultimately loosening of the implants are the usual causes of failure after normal use [2]. Dynamic in vitro testing of the human knee continues to be an area of interest to the orthopaedic biomechanics community. The scope of this work was to assess pre-clinically the wear behaviour of polyethylene knee insert under a realistic stair climbing activity using a displacement knee simulator.

Materials & Methods

Four commercial posterior-stabilized fixed-bearing component prosthesis for TKA were tested in this study (Stryker®-Orthopaedics, Mahwah, NJ-USA). These were new and delivered in sterilized packages. Particularly, corresponding UHMWPE tibial inserts (size #7) were made of conventional surgical grade polyethylene resin (GURâ�¨1020), consolidated by compression moulding (accordingly to ISO 5834/1-2), and EtO sterilized. These were tested in conjunction with corresponding CoCrMo alloy femoral components.

For the implementation of realistic loading scenarios during in vitro wear testing for human joint prostheses, an in vitro protocol was designed to simulate the flexion/extension angle, intra/extra rotation angle, and antero/posterior translation. These movements were obtained in patients by three- dimensional video-fluoroscopy. Axial load data were collected by gait analysis [3].

Introduction

To meet the demands of younger more active patients more robust pre-clinical wear testing methods are required, in order to simulate a wider range of activities. A new electromechanical simulator (Simulation Solutions, UK) with a greater range of motion, a driven abduction/adduction axis and improved input kinematic following has been developed to meet these requirements, as well as requirements of the relevant international standards. This study investigated the wear of a fixed bearing total knee replacement using this new electromechanical knee simulator, comparing with previous data from a pneumatic simulator.

Materials/Methods

The wear of six Sigma CR fixed bearing TKRs (DePuy, UK) with curved moderately cross-linked polyethylene inserts (XLK) was determined in pneumatic and electromechanical Prosim knee simulators (Simulation Solutions, UK). Standard gait displacement controlled kinematics were used, with a maximum anterior-posterior displacement of either 10mm (high) or 5mm (intermediate) [1]. The output profiles from the simulators were obtained and compared to the demand input profiles. The lubricant used was 25% new-born calf serum and wear determined gravimetrically. Statistical analysis was performed using the one-way ANOVA with 95% confidence interval and significance was taken at p<0.05.

Background

The femoral head center shift on reduction time in total hip arthroplasty (THA) causes alteration of the muscle tension around the hip joint. Many studies about the shift of the femoral head in the cranio-caudal direction or medio-lateral direction on coronal plane have been reported. It has been known widely that the shift on these directions influence tension of the abductor muscle around the hip joint. Nevertheless few studies about the three-dimensional shift including the antero-posterior direction have been reported.

Purpose

The purpose of this study is to evaluate the three-dimensional shift of the femoral head center in THA using three-dimensional THA templating software.

Introduction

The systematic effects of joint replacement in rheumatoid arthritis (RA) patients are that inflamed synovium and pathological articular cartilage has dissipated. Expectations of total knee arthroplasty (TKA) are reduction of inflammatory cytokines, decreased disease activity and improvement of drug efficacy and ADL. Remission of rheumatoid arthritis is defined as having a Disease Activity Score DAS28 (ESR) of less than 2.6 and Health Assessment Questionnaire (HAQ) – Disability Index, less than 0.5.

Purpose

We investigated whether TKA could reduce disease activity and improve ADL, and subsequent remission levels of DAS and HAQ or not.

Introduction

Stress shielding and wear induced aseptic loosening cause failure in total joint arthroplasty. To improve long-term outcomes in total knee arthroplasty (TKA), the use of a low modulus, low wearing biomaterial may be a suitable alternative to cobalt chromium (CoCr) femoral components. Based on its favorable mechanical properties and observed clinical success especially in spinal surgery, polyetheretherketone (PEEK) is investigated as a candidate material for a metal free TKA. An all polymer TKA has several theoretical advantages, these include a more physiological stress in the distal femur, elimination of biological reaction to metal, better radiographic visualisation of the bone implant interface especially with CT and MRI. In addition, polymers afford a cheaper option for the manufacture of prostheses.

Aims and Hypothesis

This study investigated the wear performance of PEEK and carbon reinforced PEEK (CFR-PEEK) as bearing materials in an all polymer TKA using a unidirectional pin on plate test. Our hypothesis was that reduced wear is generated from PEEK or CFR-PEEK bearings when compared with metal on polyethylene (MoP) bearings and that this combination may provide a suitable alternative in TKA.

INTRODUCTION

There is ongoing debate about the possible advantages of unicompartmental (UNI) knee replacement versus total knee replacement (TKR), such as for young, active patients. The purpose of this study was to investigate functional, radiographic, and device survivorship outcomes of UNI knee replacement with a newer generation UNI through 2-years post-op.

METHODS

A retrospective review of 188 cemented, fixed bearing unicompartmental (UNI) knee replacements implanted between January 2009 and June 2012 at 3 centers. The purpose of this study was to evaluate the survivorship, reasons for revision, radiographic and clinical results. A chart review was performed to collect demographics, operative details, American Knee Society (AKS) scores and adverse events (AE) through 2-years post-op. Kaplan-Meier (KM) device survivorship rates for the partial knee construct were estimated for post-op years in which at least 40 subjects had later follow-up. The definition of revision was the removal of any component for any reason, and device survivorship was the lack of revision. The time variable was the time to revision if the knee had been revised, or the time to last clinical follow-up or death if the knee had not been revised.

The average follow-up was 2.03 years (SD=0.4). The mean age was 64 years (SD=10.5), 56% of the patients were 65 years or younger, mean BMI was 27.5 kg/m2 (SD=4.9), 60% of patients were women, and 89% had a diagnosis of OA (9.6% had AVN). Data were collected through April 2015.

Background

Polyetheretherketone (PEEK) may be advantageous as an alternative material to metal alloys in some orthopaedic applications. However, it is bioinert and does not osseointegrate1. A novel accelerated neutral atom beam technique (ANAB) has been developed to improve the bioactivity of PEEK where the surface is modified to a depth of 5 nm without affecting the integrity of the underlying PEEK structure2.

Aim

The aim of this study was to investigate the growth of human Mesenchymal Stem Cells (hMSCs), adult human Osteoblasts (hOB) and skin Fibroblasts (BR3G) on PEEK and ANAB treated PEEK.

Introduction

Primary stability is essential for long-term performance of cementless femoral components. There is debate as to whether collars contribute to primary stability. The results from experimental studies and finite element (FE) analysis have been variable and contradictory. Subtle differences in performance are often swamped by variation between cadaveric specimens in vitro, whereas FE studies tend to be performed on a single femur. However, FE studies have the potential to make comparisons of implant designs within the same cohort of femurs, allowing for subtle performance differences to be identified if present. This study investigates the effect of a collar on primary stability of a femoral prosthesis across a representative cohort of femurs.

Materials and Methods

FE models were generated from QCT scans of eight cadaveric femurs taken from the Melbourne Femur Collection (4 male and 4 female; BMI: 18.7 – 36.8 kg.m-2; age: 59 – 80 years) which were of joint replacement age. Heterogeneous bone material properties were assigned based on the CT greyscale information. Each femur was implanted with the collared and collarless version of Corail femoral stem (DePuy, Leeds, United Kingdom). The stems were sized and positioned so that the prosthesis filled the medullary canal with minimal gap between the prosthesis and the inner boundary of the cortical bone. The peak muscle and joint contact forces associated with level gait were applied and the distal femur was rigidly fixed. The forces were scaled based on the body weight for each subject. Micromotion, as well as microstrains at the bone-prosthesis interface were measured for each subject. Paired t-test was run to compare the micromotion and the microstrains measured for the collared and collarless prosthesis.

Background

Cement restrictors are used for maintaining good filling and pressurization of bone cement during hip and knee arthroplasties. The limitations of certain cement restrictors include the inability to accommodate for large medullary canals particularly in revision procedures. We describe a technique using SurgicelTM (Johnson & Johnson) and SPONGOSTAN™ (Johnson & Johnson) (Fig 1) to form a cement restrictor that can accommodate for large canal diameters and provide excellent pressurisation.

Technique

The technique involves the application of SPONGOSTAN™ (Johnson & Johnson) foam onto a SurgicelTM (Johnson & Johnson) mesh which is then rolled onto the SPONGOSTAN™ foam forming a uniform cylindrical structure Figs 2,3. The diameter of the restrictor can be adjusted according to the desired femoral canal diameter through increasing the thickness of the SPONGOSTAN™ (Johnson & Johnson) foam. The restrictor is then inserted into the desired position in the medullary canal where it expands uniformly creating an effective restrictor and bone plug Fig 4. Bone cement is then applied and pressurisation commenced prior to the insertion of the implant Fig5.

SPONGOSTAN™ is an absorbable haemostatic sponge intended for haemostatic use by applying to a bleeding surface. It consists of a sterile, water-insoluble, malleable, porcine gelatin absorbable sponge.

Surgicel ™ is an absorbable hemostatic agent composed of oxidized regenerated cellulose. It is a sterile, absorbable knitted fabric that is flexible and adheres readily to bleeding surfaces. Both products are routinely used for their haemostatic properties in various surgical disciplines.

Purpose

The minimally invasive surgery (MIS) approach has been popularised as an alternative to the standard open approach in acute Achilles tendon ruptures. Advocates of this technique suggest earlier functional recovery, due to less injury to the surrounding tissues. However, the critics argue that due to the reduced exposure risk and complications of such surgery are higher in comparison to the open technique.

Methods

A systematic review and meta-analysis of randomised and prospective studies were conducted to compare the MIS and open surgery in acute Achilles tendon ruptures.

Introduction

Translational surgical mismatch in the centres of rotation of the femoral head and acetabular cup in hip joint replacements can lead to dynamic microseparation resulting in edge loading contact [1]. Increased wear in retrieved ceramic-on-ceramic bearings has been associated with edge loading [2]. Hip joint simulators were used to replicate increased wear rate, stripe wear and bimodal wear debris size distribution, as seen clinically [3,4]. Recently developed electromechanical simulators are able to comply with the latest international standards, which include three axes of rotation conditions [5]. Previous simulators had applied two axes of rotation under microseparation conditions [6]. Therefore, the aim of this study was to compare the wear of ceramic-on-ceramic bearings obtained under edge loading due to microseparation conditions during gait using the same electromechanical hip joint simulator with two axes of rotation and three axes of rotation conditions.

Materials and Methods

A six-station electromechanical hip joint simulator (ProSim EM13, Simulation Solutions, UK) was set up with 36mm diameter ceramic-on-ceramic (BIOLOX® delta, PINNACLE®, DePuy Synthes, UK) hip replacements. The wear was determined for two million cycles under standard conditions with two axes of rotation conditions (n=6), two million cycles under microseparation conditions with two axes of rotation conditions (n=6) (Figure 1a), and two million cycles under microseparation conditions with three axes of rotation conditions (n=6) (Figure 1b). The loading profiles [5,7] comprised of 3kN twin peak loads and 300N swing phase load under standard conditions. The swing phase load was reduced to approximately 70N under microseparation conditions. Approximately 0.5mm of dynamic microseparation between the head and the cup was applied in the medial/lateral direction. The components were lubricated with 25% new-born calf serum supplemented with 0.03% sodium azide to minimise bacterial growth. The gravimetric wear rates were compared over two million cycles for each test (XP205, Mettler Toledo, UK). The mean wear rates of the head and cup were calculated with 95% confidence limits and statistical analysis was carried out (t-test) with significance levels taken at p<0.05. A coordinate-measurement machine (Legex 322, Mitutoyo, UK) was used to construct a three-dimensional map of the femoral head surface wear.

Conclusion

This treatment has preserved the joints of fourteen patients. Of the four revised, two patients had clinical grades or bone quality contra-indicated for the device and three had lesions occupying more than 30% of the femoral head: Improved criteria for patient selection may be required. The device is only partially load-bearing and incapable of stabilising fractures: The radiolucent band associated with fibrous tissue formation may be an early indication of failure.

Introduction

Total knee arthroplasty (TKA) can effectively treat end-stage knee osteoarthritis. For cruciate-retaining (CR) TKA, the posterior tibial slope (PTS) of the reconstructed proximal tibia plays a significant role in restoring normal knee kinematics as it directly affects the tension of the posterior cruciate ligament (PCL) [1]. However, conventional cadaveric testing of the impact of PTS on knee kinematics may damage/stretch the PCL, therefore impact the test reproducibility. The purpose of this study was to assess the reproducibility of a novel method for the evaluation of the effects of PTS on knee kinematics.

Materials and Methods

Cemented CR TKAs (Logic CR, Exactech, Gainesville, FL, USA) were performed using a computer-assisted surgical guidance system (ExactechGPS®, Blue-Ortho, Grenoble, FR) on six fresh frozen non-arthritic knees (PCL presumably intact). The tibial baseplate was specially designed (Fig. 1) with a mechanism to modify the PTS in-situ. Knee kinematics, including anteroposterior (AP) translation, internal/external (IE) rotation, and hip-knee-ankle angles, were evaluated by performing a passive range of motion from extension up to ∼110° of flexion, three separate times at 5 PTSs: 10°, 7°, 4°, 1°, and then 10° again. The repeatability of the test was investigated by comparing the kinematics between the first and the last 10° tests. Any clinically relevant deviation (1.5° for the hip knee ankle angle, 1.5mm for anterior-posterior translation and 3° for internal-external rotation) would reflect damage to the soft-tissue envelope or the PCL during the evaluation. Potential damage of PCL was investigated by comparing the kinematic parameters from the first and last 10° slope tests at selected flexion angles (Table 1) by paired t-test, with statistical significance defined as p<0.05.

INTRODUCTION

Cemented total knee arthroplasty (TKA) is a widely accepted treatment for end-stage knee osteoarthritis. During this procedure, the surgeon targets proper alignment of the leg and balanced flexion/extension gaps. However, the cement layer may impact the placement of the component, leading to changes in the mechanical alignment and gap size. The goal of the study was to assess the impact of cement layer on the tibial mechanical alignment and joint gap during cemented TKA.

MATERIAL

Computer-assisted TKAs (ExactechGPS®, Blue-Ortho, Grenoble, FR) were performed by two fellowship trained orthorpaedic surgeons on five fresh-frozen non-arthritic pelvis-to-ankle cadaver legs. All the surgeries used a cemented cruciate retaining system (Optetrak Logic CR, Exactech, Gainesville, FL). After the bony resection, the proximal tibial resection plane was acquired by manually pressing an instrumented checker onto the resected tibial surface (resection plane). Once the prosthesis was implanted through standard cementing techniques, the top surface of the implanted tibial component was probed and recorded using an instrumented probe. A best fit plane was then calculated from the probed points and offset by the thickness of the prosthesis, representing the bottom plane of the component (component plane).

The deviation of component alignment caused by the cement layer was calculated as the coronal and sagittal projection of the three-dimensional angle between the resection plane and the component plane. The deviation of the component height, reflecting a change in the joint gap, was assessed as the distance between the two planes calculated at the lowest points on the medial and lateral compartments of the proximal tibial surface. Statistical significance was defined as p≤0.05.

Introduction

When evaluating the biomechanical performance of a total knee arthroplasty (TKA) implant design, device companies are usually required to select the “worst case scenario” for testing by the regulatory bodies. However, most test standards (e.g., ASTM, ISO) do not explicitly specify how the “worst case” should be determined. It is quite often that an extreme size (the smallest or the largest) in a system is taken as the “worst case” size. The smallest size is sometimes selected under the rationale that it has the smallest geometry thus the weakest mechanical structure. While the largest size is sometimes selected under the rationale that it is used on the biggest patients associated with the highest loads. However, implant geometry and in vivo load are two compounding factors that together determine the implant's biomechanical challenge. As the result, the true “worst case” must be determined considering both factors, and the choice could be design-specific. This study evaluated the femorotibial contact stress of a TKA implant system, and demonstrated that the extreme sizes may not simply be the “worst case”.

Methods

The femorotibial contact stress of a posterior-stabilizing TKA implant system was assessed using finite element analysis. Multiple sizes ranging from size 0 to 6 were analyzed. For each size, the CAD models were assembled at knee extension. A load equivalent to 4 times of patient body weight was applied. Average patient body weights were calculated based on the company's clinical database: 72.5, 76.0, 80.0, 87.4, 95.2, 103.4, and 111.0 kg for sizes 0, 1, 2, 3, 4, 5 and 6, respectively. Von Mises stresses in the polyethylene tibial insert were examined and compared among different sizes.

Introduction

Patellofemoral joint is an important aspect of the tri-compartmental knee joint complex. Total knee arthroplasty (TKA) replaces the articulating surfaces of distal femur and proximal tibia, and often times the patella as well. Understanding the size relationship between the femur and patella bones can provide valuable information for new prosthesis design and biomechanical analysis. However, taking anthropometric measurements on a large population of patients or even cadaveric specimens could be a challenge. As a result, there are currently little quantitative data existing in the literature regarding the size relationship between TKA patient's femur and patella. This study attempted to attack this question using a novel statistical approach and a large TKA patient database.

Methods

A multi-site clinical database operated by Exactech was used in this study. The database contains patient information of Optetrak TKA implant recipients from over 30 physicians in US, UK, and Colombia since 1995. Nine femoral implant sizes (0, 1, 2, 2.5, 3, 3.5, 4, 5 and 6) and six patellar implant sizes (26, 29, 32, 35, 38, 41 mm) were seen in these patients. Due to the low usage, femoral sizes 0 and 6 were excluded from this analysis. Taking primary TKA only, a total of 2,698 cases were included in this study. The size relationship between femoral implant and patellar implant was analyzed in this patient population. Gender effect was also examined.

Introduction

Previous studies of long-term CoCr alloy femoral components for TKA have identified 3rd body abrasive wear and inflammatory cell induced corrosion (ICIC). The extent of femoral condyle surface damage in contemporary CoCr femoral components is currently unclear. The purpose of this study was to investigate the prevalence and morphology of damage (3rd body scratches and ICIC) at the bearing surface in retrieved TKA femoral components from contemporary designs.

Methods

308 CoCr femoral TKA components were collected as part of an ongoing, multi-institutional orthopedic implant retrieval program. The collection included contemporary designs from Stryker (Triathlon n=48, NRG n=10, Scorpio n=31), Depuy Synthes (PFC n=27) and Zimmer (NexGen n=140, Persona n=1) and Biomet (Vanguard n=51). Hinged knee designs and unicondylar knee designs were excluded. Components were split into groups based on implantation time: short-term (1–3y, n=134), intermediate-term (3–5y, n=73) and long-term (6–15y, n=101). Each grouping was mainly revised for instability, infection and loosening.

Third-body abrasive wear of CoCr was evaluated using a semi-quantitative scoring method similar to the Hood method (Figure 1). A score of 1 had minimal damage and a score of 4 corresponded to damage covering more than 50% of the evaluated area. ICIC damage was reported as location of affected area. A white light interferometer (Zygo New View 5000) was also used to analyze the topography of severe damage of the bearing surface. For this analysis, three representative components from each cohort were selected and analyzed in three locations on the apex of the bearing surface. We analyzed the following roughness parameters: Ra, Rsk, and Rku.

Objective

The purpose of this study was to evaluate the efficacy and safety of the drained-clamped method with intra-articular infusion of tranexamic acid (TA) for reducing blood loss in total knee arthroplasty (TKA).

Material and Methods

From November 2011 to July 2014 inclusive, 72 patients with a diagnosis of osteoarthritis underwent unilateral primary TKA using a computed tomography (CT) free navigation system. Patients were randomly divided into two groups: group T (n=40) was given 2000 mg (40 ml) of TA and group W (n=32) was given 40 ml sterile saline only. All operations were performed under total anaesthesia through the medial mid-vastus approach. Cemented posterior stabilised or cruciate retaining prostheses were used. The patella was resurfaced. After tourniquet release and wound suture, TA or saline was infused into the knee joint in addition to the drained-clamped method for 2 hours. For VTE prophylaxis, all patients received bilateral intermittent pneumatic calf compressors, thromboembolic deterrent stockings, and subcutaneous injection of enoxaparin (4000IU daily). We evaluated the hematocrit, hemoglobin and the postoperative estimate of bleeding. At postoperative days 4, extremity venous ultrasonography was performed for the investigation of venous thromboembolism in the latest 40 patients and contrast-enhanced CT was performed in the latest 34 patients without a previous history of asthma and diminished renal function. The present study received institutional review board approval, and informed consent was obtained from all patients.

Introduction

Total knee arthroplasty (TKA) has achieved excellent clinical outcomes and functional performances. However, there is a need for greater implant longevity and higher flexion by younger and Asian patients. We determined the relationship between mobility and stability of TKA product because they are essential for much further functional upgrading. This research evaluated the geometry characteristics of femorotibial surfaces quantitatively by measuring their force of constraint by computer simulation and mechanical test.

Methods

We measured the force of constraint of femorotibial surfaces in order to evaluate the property of femorotibial surfaces. A total knee system was used for this evaluation, and has an asymmetrical joint surface, which restores the anatomical jointline in both sagittal and coronal planes, and is expected to permit normal kinematics, with cruciate-retaining fixed type.

We performed computer simulation using finite element analyses (FEA) and mechanical tests using knee simulator 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. In the FEA, Young's modulus and Poisson's ratio were set to 213 GPa and 0.3 for Co-Cr-Mo alloy as the femoral component, and 1 GPa and 0.3 for UHMWPe as the tibial insert, respectively. 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 710 N was loaded on the femoral component during these measurements.

Introduction

Oxide-based alumina (Al2O3) is used to manufacture femoral heads for total hip arthroplasty (THA). Silicon nitride (Si3N4) is a non-oxide ceramic used to make spinal implants. Ceramic materials are believed to be bioinert, (i.e., stable under hydrothermal conditions). Indeed, clinical data have shown 15–20 year longevity of Al2O3 bearings in THA. In this work, we examined the surfaces of Al2O3 and Si3N4 after exposure to physiologic conditions to see if these ceramics are truly inert.

Materials and Methods

Four self-mated Ø28 mm diameter Al2O3 femoral heads (n=2 each of BIOLOX®forte, CeramTec, Plochingen, Germany; and BIOCERAM®, Kyocera Co., Kyoto, Japan), were retrieved during revision THA, between 7.7–10.7 years post-implantation. To simulate in vivo material aging, comparable, new Al2O3 and Si3N4 femoral heads (AMEDICA Corporation, Salt Lake City, UT, USA) were exposed to autoclave conditions (100°C-121°C; 300 hrs; n=3 heads, per material). Advanced Raman and cathodoluminescence spectroscopy, and electron microscopy were used to examine surface characteristics of each specimen, and quantify oxygen ion vacancy formation and composition.

Background

The use of robotics in joint arthroplasty was initiated in 1992 with the introduction of the ROBODOC® Surgical Assistant device for planning and active robotic preparation of the femoral canal in THA. From 1993–1996, an FDA trial was undertaken using pin-based fiduciary markers to register the CT to the robot coordinate system. From 2000–2006, a second FDA trial was initiated using a point-to-surface matching “pinless” registration system. Combined, these two studies offer the first long-term follow-up of robot-assisted THA using an active robotic system for preparation of the femoral canal during THA.

Methods

Due to the support of an open implant architecture, patients were implanted with either the Depuy AML, Howmedica Osteoloc, or Zimmer VerSys FMT. Combining patients from the two studies, 86 THA's were performed in 63 patients using the active robotic system. Of these 63 patients, 7 were confirmed to have died and 5 have been lost to follow-up, 2 declined to participate due to infirmity, 37 are still recruiting, and 12 are currently enrolled (16 hips). Data collected included: Harris Hip Scale, HSQ-12, WOMAC, UCLA Activity Score, VAS Pain Score as well as radiographic analysis. The demographics at follow-up were:

Introduction

Postoperative dislocation remains a vexing problem for patients and surgeons following total hip arthroplasty (THA). It is the commonest reason for revision THA in the US. Dual mobility (DM) THA implants markedly decrease the risk of THA instability. However, DM implants are more expensive than those used for conventional THA. The purpose of this study was to perform a cost-effectiveness analysis of DM implants compared to conventional bearing couples for unilateral primary THA using a computer model-based evaluation.

Methods

A state-transition Markov computer simulation model was developed to compare the cost-utility of dual mobility versus conventional THA for hip osteoarthritis from a societal perspective (Figure 1). The model was populated with health outcomes and probabilities from registry and published data. Health outcomes were expressed as quality-adjusted life years (QALYs). Direct costs were derived from the literature and from administrative claims data, and indirect costs reflected estimated lost wages. All costs were expressed in 2013 US dollars. Health and cost outcomes were discounted by 3% annually. The base case modeled a 65-year-old patient undergoing THA for unilateral hip osteoarthritis. A lifetime time horizon was analyzed. The primary outcome was the incremental cost-effectiveness ratio (ICER). The willingness-to-pay threshold was set at $100,000/QALY. Threshold, one-way, two-way, and probabilistic sensitivity analyses were performed to assess model uncertainty.

Introduction

Neutral mechanical alignment in TKA has been shown to be an important consideration for survivorship, wear, and aseptic loosening. However, native knee anatomy is described by a joint line in 3° of varus, 2–3° of mechanical distal femoral valgus, and 2–3° of proximal tibia varus. Described kinematic planning methods replicate native joint alignment in extension without changing tibiofemoral alignment, but do not account for native alignment through a range of motion. An asymmetric TKA femoral component with a thicker medial femoral condyle and posterior condylar internal rotation paired with an asymmetric polyethylene insert aligns the joint line in 3° of varus while maintaining distal femoral and proximal tibial cuts perpendicular to mechanical axis. The asymmetric components recreate an anatomic varus joint line while avoiding tibiofemoral malalignment or femoral component internal rotation, a risk factor for patellofemoral maltracking. The study seeks to determine how many patients would be candidates for a kinematically planned knee without violating the principle of a neutral mechanical axis (0° ± 3°).

Methods

A cohort comprised of 55 consecutive preoperative THA patients with asymptomatic knees and 55 consecutive preoperative primary unilateral TKA patients underwent simultaneous biplanar radiographic imaging. Full length coronal images from the thoracolumbar junction to the ankles were measured by two independent observers for the following: mechanical tibiofemoral angle (mTFA), mechanical lateral distal femoral angle (mLDFA), and mechanical medial proximal tibial angle (mMPTA). Patients who met the following conditions: mTFA 0°±3°; mLDFA 87°±3°; and mMPTA 87°±3°, were considered candidates for TKA with an asymmetric implant that would achieve a kinematic joint line and neutral mechanical axis. Similarly, patients with the following conditions: mTFA 0°±3°; mLDFA 90°±3°; and mMPTA 90°±3°, were considered candidates for TKA with a symmetric implant that would achieve a kinematic joint line and neutral mechanical axis.

Introduction

Dual modular hip prostheses were introduced to optimize the individual and intra-surgical adaptation of the implant design to the native anatomics und biomechanics of the hip. The downside of a modular implant design with an additional modular interface is the potential susceptibility to fretting, crevice corrosion and wear [1–2]. The purpose of this study was to characterize the metal ion release of a modular hip implant system with different modular junctions and material combinations in consideration of the corrosive physiological environment.

Methods

One design of a dual modular hip prosthesis (Ti6Al4V, Metha®, Aesculap AG, Germany) with a high offset neck adapter (CoCrMo, CCD-angle of 130°, neutral antetorsion) and a monobloc prosthesis (stem size 4) of the same implant type were used to characterize the metal ion release of modular and non-modular hip implants. Stems were embedded in PMMA with 10° adduction and 9° flexion according to ISO 7206-6 and assembled with ceramic (Biolox® delta) or CoCrMo femoral heads (XL-offset) by three light impacts with a hammer. All implant options were tested in four different test fluids: Ringer's solution, bovine calf serum and iron chloride solution (FeCl3-concentration: 10 g/L and 114 g/L). Cyclic axial sinusoidal compressive load (Fmax = 3800 N, peak load level of walking based on in vivo force measurements [3]) was applied for 10 million cycles using a servohydraulic testing machine (MTS MiniBionix 370). The test frequency was continuously varied between 15 Hz (9900 cycles) followed by 1 Hz (100 cycles). The metal ion concentration (cobalt, chromium and titanium) of the test fluids were analysed using ICP-OES and ICP-MS at intervals of 0, 5·105, 2·106 and 10·106 cycles (measuring sensitivity < 1 µg/L).

Introduction

The optimal bearing for hip arthroplasty is still a matter of debate. in younger and more active patients ceramic-on-polyethylene (CoP) bearings are frequently chosen over metal-on-polyethylene (MoP) bearings to reduce wear and increase biocompatibility. However, the fracture risk of ceramic heads is higher than that of metal heads. This can cause serious issue, as ceramic fractures pose a serious complication often necessitating major revision surgery – a complication more frequently seen in ceramic-on-ceramic bearings. To date, there are no long-term data (> 20 years of follow-up) reporting fracture rates of the ceramic femoral heads in CoP bearings.

Patients and Methods

We retrospectively evaluated the clinical and radiographic results of 348 cementless THAs treated with 2nd generation Biolox® Al2O3 Ceramic-on-Polyethylene (CoP) bearings, which had been consecutively implanted between January 1985 and December 1989. At implantation the mean patient age was 57 years. The cohort was subsequently followed for a minimum of 20 years. At the final follow-up 111 patients had died, and 5 were lost to follow-up (Fig. 1). A Kaplan-Meier survivorship analysis was used to estimate the cumulative incidence of ceramic head fractures over the long-term.

Background

Total knee arthroplasty (TKA) is a cost-effective surgical procedure for degenerative knee disease and has good long-term results. However, these results are not always related to patient satisfaction and functional outcome. With an increasing demand of surgeons and patients on functioning of total knee implants, the need for adequate objective outcome measures is high. Imaging of the knee is commonly used in clinical practice and research to objectively measure many different outcome parameters concerning the implant, such as alignment and complications.1 However, techniques on comparison of the sagittal contour of the knee before and after implant placement are scarce.

Goal

To develop and describe a standardized method for measuring the sagittal contour of the implant in a 3D model of the knee before and after implant placement.

Acknowledgements

This work was partially supported by Italian Ministry of Health, Grant ‘Early diagnosis of pending failure.’ and by Regione Emilia Romagna, cofounding of RIPO. All orthopedic Units of the Region are gratefully acknowledged for providing data to the Register

Introduction

Patient-specific cutting guides entered into clinical practice few years ago, first introduced in total knee replacement and recently also for other joint replacements. Advantages claimed are improving accuracy and repeatability in implant placement. New patient-specific guides to perform an accurate femoral neck resection and provide a precise alignment reference for acetabular reaming in total hip arthroplasty (THA) were recently developed by Medacta International: MyHip Technology. To date femoral guides can be designed for both anterior and posterior approaches, whereas acetabular guides are available only for posterior approach.

Evaluation of the repeatability and reproducibility of MyHip guides placement on cadavers is performed using a navigation system. Accuracy of femoral MyHip guides is evaluated also through one author's clinical experience (RP).

Materials and Methods

During each cadaveric session one body (2 hips) was available. A pre-operative CT scan has been obtained and used in order to create the 3D bone model of the pelvis and proximal femurs. Afterwards, a surgical planning for THA has been performed for each case, and, once it was approved by the surgeons, the designed patient-specific blocks were made.

Intraobserver and interobserver agreement in positioning the guides was assessed getting measures of femoral head resection height (mm), femoral head plane inclination/anteversion (°) and acetabular reaming axis orientation (°). 9 surgeons, through 2 cadaveric sessions, positioned each guide, removed it and re-positioned it 5 times alternatively. The system is judged as accurate if all measures differ less than 3mm and 5°for lengths and angles respectively from the average among all the acquisitions.

Clinical experience includes 68 THA which were performed between March 2014 and April 2015. Anterior femoral MyHip guides were used for the femoral head resection, while the acetabular side was prepared using the standard metal instrumentation for minimally invasive anterior approach. Intra-operative complications, as well post-operative leg length difference and implant positioning are assessed.

Objective

In total knee arthroplasty, three-dimensional “criss-cross” line locate femoral osteotomy and conventional osteotomy were used. By comparing the two methods osteotomy in patients before and after surgery and imaging-related information data, to evaluate the recent post operative efficacy, at the same time to find out if there has clinical evidence that three-dimensional “criss-cross” line locate femoral osteotomy can be used in total knee arthroplasty.

Methods

From July 2012 to July 2014, 64 patients who undertook the artificial total knee arthroplasty were divided into 2 groups: conventional osteotomy group(group A)and three-dimensional “criss-cross” line locate femoral osteotomy group(group B). In the X-ray of the two groups, it was measured that the hip-knee-ankle angle and the joint gap symmetry of 90°flexion degree. It was also measured that the two group joints range of motion. Those data were statistically analyzed. The KSS score of the two groups were compared.

Introduction

Good outcomes in reverse shoulder arthroplasty (RSA) rely in part on stability of the humeral component. Traditionally humeral components have been cemented, however there has been recent interest in press-fit fixation of humeral components in RSA. Lateralization of the head center in RSA can impart larger moments on the humeral component than for anatomic reconstructions, increasing the importance of distal humeral canal preparation for implant stability. To date, the primary stability of any type of press-fit humeral prosthesis has been largely unexplored. The goal of this study is to evaluate the effect of over-reaming the distal humeral canal in a press-fit humeral component in RSA.

Methods

Computed tomography (CT) data of the shoulder were obtained from 55 shoulders. Images were segmented to produce digital models of the humerus. Humeral components for RSA (2mm diameter size increments) were sized and placed per the surgical technique, including preparation of the humerus with the appropriate reamers (1mm increments). Finite element models for each specimen were created with heterogeneous bone properties derived from the CT scan. Pressfit between the bone and stem was resolved to quantify the initial contact pressure on the stem; each stem was then loaded at 566N oriented 20° lateral and 45° anterior. Overall motion of the stem was measured, as well as interfacial micromotion in the porous coating region (Fig. 1). The effect of line-to-line (L2L) reaming and over-reaming by 1 mm was evaluated using an unpaired Student's t-test, with significance defined at p<0.05.

Introduction

Fretting corrosion at the taper interface has been implicated as a possible cause of implant failure. Using in-vitro testing, fretting wear observed at tapers of retrieved implants may be reproduced (Marriott, EORS-2014). In order to reduce time and cost associated with experimental testing, a validated finite element method (FE) can be employed to study the mechanics at the taper. In this study we compared experimental and representative FE simulations of an accelerated fretting test set-up. Comparison was made by between the FE wear score and volumetric material loss from the testing.

Methods

Experimental test set-up: An accelerated wear test was developed that consistently reproduced fretting wear features observed in retrievals. Biomet stems with smooth 4° Type-1 tapers were combined with Ti6Al4V Magnum +9 mm adaptors using a 2 or 15 kN assembly force. The head was replaced with a custom head fixture to increase the offset and apply a torque at the taper interface. The stems were potted according to ISO 7206-6:2013. The set-up was submerged in a test medium containing PBS and 90gl-1 NaCl. The solution was pH adjusted to 3 using HCl and maintained at 37°C throughout the tests. For each assembly case, n=3 tests were cyclically loaded between 0.4–4 kN for 10 Million cycles. Volumetric wear measurements were performed using a Talyrond-365 roundness measurement machine. The FE model was created to replicate the experimental set up. Geometries and experimental material data were obtained from the manufacturer (Biomet). The same assembly forces of 2 and 15 kN were applied, and the same head fixture was used for similar offset and loading conditions. The 4 kN load was applied at the same angles in accordance with ISO 7206-6:2013. Micromotions and contact pressures were calculated, and based on these a wear score was determined by summation over all contact points.

Introduction

Silicon nitride (Si3N4) is a ceramic material presently implanted during spine surgery. It has a fortunate combination of material properties such as high strength and fracture toughness, inherent phase stability, scratch resistance, low wear, biocompatibility, hydrophilic behavior, easier radiographic imaging and resistance to bacterial biofilm formation, all of which make it an attractive choice for orthopaedic applications beyond spine surgery. Unlike oxide ceramics, (e.g., alumina or Al2O3) the surface chemistry and topography of Si3N4 can be precisely engineered to address in vivo demands. Si3N4 can be manufactured to have an ultra-smooth, or highly fibrous, or porous morphology. Its chemistry can be varied from that of a silica-like surface composed of silanol moieties to one which is predominately comprised of silicon-amine functional groups.

Methods

In the present study, a Si3N4 bioceramic formulation was exposed to thermal, chemical, and mechanical treatments in order to induce changes in surface composition and features. The treatments included grinding and polishing, etching in hydrofluoric acid solution, and heating in nitrogen or air. Resulting surfaces were characterized using a variety of microscopy techniques to assess morphology. Surface chemical and phase composition were determined using x-ray photoelectron and Raman spectroscopy, respectively. Streaming potential measurements evaluated surface charging, and sessile water drop techniques assessed wetting behavior.

Background

The adult acquired flat foot is caused by a complete or partial tear of the tibialis posterior tendon. We present the results of flexor digitorum longus transfer and medializing calcaneal osteotomy for recontruction of the deformity.

Material & Methods

Twenty-six patients (31 feet) with an average age of 58 years (36–75) were operated for an acquired flat foot deformity. The patients were seen before surgery, one year after surgery and an average of 85 months after surgery to assess the following parameters: AOFAS Score, VAS Score for pain (0–10). Foot x-rays in full weightbearing position (dorsoplantar and lateral) were done at every visit in order to assess the following parameters: tarsometatarsale angle on the dorsoplantar and lateral x-ray, talocalcaneal angle on the lateral x-ray, calcaneal pitch angle and medial cuneiforme height on the lateral x-ray.

Goals of the study

(1) to investigate the relationships between the bony contours of the knee and the Popliteus Tendon (PT) in the healthy knee and after implantation of a TKA and (2) to analyze the influence of implant sizing.

Hypothesis

With an apparently well-sized TKA, the position of the PT during knee flexion is modified compared with the preoperative situation.

Introduction

Total knee arthroplasty (TKA) using conventional instrumentation has been shown to be a safe and effective way of treating end stage osteoarthritis by restoring function and alleviating pain. As robotic technology is developed to assist surgeons with intra-operative decision making such as joint balancing and component positioning, the safety of these advancements must be established. Furthermore, functional recovery and clinical outcomes should achieve comparable results to the gold standard of conventional instrumentation TKA.

Methods

Eighty-seven subjects (89 knees) underwent robotic arm assisted TKA by one of three investigators as part of an FDA and IRB approved Investigational Device Exemption (IDE). To achieve the primary endpoint of intra-operative patient safety using a robotic arm assisted cutting tool, the investigators completed questionnaires to assess a series of complications related to soft tissue damage associated with conventional TKA. Western Ontario and McMaster Universities Arthritis Index (WOMAC) and Knee Society Knee Scores (KSS) were collected pre-operatively and at three month follow-up.

Introduction

The Center for Medicare Services (CMS) recently proposed its phase 3 “Quality metrics” which include a section on patient engagement. CMS uses a fitness monitor as an example of an acceptable way for patients to contribute to the health record. Wearable technology allows measurement of activity, blood glucose, heart rate, sleep, and other health metrics, all of which can be useful in the management of patients in the orthopaedic practice. The purpose of this study is to thoroughly review existing fitness devices; and evaluate their potential uses in orthopaedic practice.

Methods

Several fitness devices exist; we focused on the top 27 based on popularity mentioned in reputable tech review articles. Features of each device were reviewed including type, specifications, interfaces, measurable outcomes (HR, steps, distance, sleep, weight, calorie intake), cost to the patient, barriers to compliance and strengths. Ultimately all these factors were taken into consideration to look into potential uses for orthopaedic surgery. The orthopedic applications of these devices were reviewed. Nonsurgical management applications were: compliance with physiotherapy, distance walked and stairs completed, and compliance with activity restrictions. Preoperative optimization included detection of sleep apnea, blood glucose monitoring, preoperative weight, and preoperative activity level. Postoperative outcomes included postoperative activity level, stairs, and distance walked.

Introduction

Cross-linked polyethylene in total hip arthroplasty has demonstrated excellent long-term wear resistance, leading to its acceptance as the standard bearing used in hip replacement. Adoption in knee replacement has been tentative, as the cross-linking process can decrease the polyethylene mechanical properties. The current study's purpose was examining survivorship of a fixed bearing knee replacement system featuring a moderately cross-linked polyethylene (MXLK) bearing, a cobalt chrome (CoCr) tibial tray with a highly polished top surface, and a new polyethylene-to-tray locking mechanism. The MXLK is made of ultra-high molecular weight GUR1020 resin irradiated with 5 Mrad gamma radiation, followed by a free radical quenching remelting annealing process, above the 135 degree melting point, that provides wear and fatigue resistance, and oxidative stability.

Materials & Methods

From November 2005 to June 2008, 539 PFC Sigma primary total knee replacements (TKA's) were prospectively entered into this non-comparative, multicenter, multinational study. Average age at time of surgery was 67 years, 57% were female, average body mass index was 30.4 kg/m2, and the dominant diagnosis was osteoarthritis (97%). Kaplan-Meier (KM) survivorship was the primary endpoint with primary event definition being removal of any component for any reason. The time variable was one of the following: time to revision, time to death, or time to last follow-up. Additional endpoints included: American Knee Society scores (knee and function), Oxford Knee score (range 12 to 60), SF-12 scores; radiographically assessed rates of radiolucent lines (RLL's) and osteolysis. RLL's greater than 2mm were counted. Progressive RLL's were those increasing in width from an earlier follow-up interval. Adjacent RLL's were defined as RLL's in adjacent zones. Complete RLL's were defined as RLL's completely around a component. This report provides 5-year results in this ongoing study with a 10-year final endpoint.

Purpose

To describe a 10-year long history of recurrent displacement and infection in a 37 yo female patient, HIV+/HCV+, with an history of drug addiction.

Clinical History

Starting from avascular necrosis of the hip (caused by prolonged HAART therapy), the patient underwent first uncemented THA in 2003. One month after implant a septic mobilization due to local abscess was treated with first two stage revision surgery (modular stem with use of retention liner for intraoperatory instability and dislocation of the implant) that lasted for almost 6 years. After 6 years of apparent good clinical condition and stability of the implants, the patient came back with a septic state of the hip, and recurrent instability, caused by complete abruption of the cup from acetabulum (Figure 1) Another two stage revision was planned; patient suffered dislocation of the spacer in first hours after intervention and 3 months later was performed second stage revision (stem with modular neck and head, cup with augmentation metal liner). Three days later patient suffered from another dislocation, so implant was further revised (change of modular neck + dual mobility head/cup), and a pelvipodalic cast was even made, considering the poor compliance of the patient,. One month later, due to another local septic state of the hip and in consideration of clinical history, a DAIR procedure was performed with revision of limited modular components until intraoperative stability was assessed (metal spacer + metal liner + dual mobility head and cup). For further assurance, an external fixator was placed around the hip (Figure 2).

Significance

Increasing health care costs are bankrupting the United States and other industrialized countries. To control and/or reduce costs in health care, hospitals, payers, and patients are turning to evidence-based meta-analyses and health economic analyses to identify medical treatments that provide value (value=outcome/cost). Objective: To determine if clinical outcome (patient reported outcomes) analyses or value/economic analyses are more likely to provide the evidence needed for adoption of new technologies in arthroplasty.

Methods

A proprietary joint arthroplasty database of patient reported outcomes (PROs) was analyzed to determine the minimum clinically important differences (MCIDs) for PROs used for total knee replacement surgery. The PROs analyzed were: (1) European quality of life (EQ-5D); Oxford Knee Score (OKS); (3) Lower Extremity Activity Scale (LEAS); and (4) Likert Pain Scale (LPS). The MCID was calculated using a distribution method where the MCID equals one half the standard deviation of the score change, MCID = σΔ/2. For clinical meta-analyses, new technologies must demonstrate statistically significant better PROs and the difference must be greater than the MCID. For economic analyses, quality adjusted life years (QALYs) are used. For example, if a total knee replacement (TKR) improved a patient's health-related quality of life by 10% (0.10) and the assumed implant life is 15 years, the patient received 1.5 QALYs (0.10 × 15 years). If the total cost of care for the knee replacement surgery is $30,000, the cost per QALY is $20,000 ($30,000/1.5 QALYs).

Significance

In spite of evidence that total knee replacement (TKR) surgery is effective, numerous studies have demonstrated that approximately 20 percent of patients who have undergone TKR surgery are not satisfied. This relatively high rate of patients who are not satisfied is the result of unmet patient expectations. The strongest predictor of dissatisfaction after TKR is unmet expectations (RR = 10.7, Bourne, Chesworth, et al, 2010). This is confirmed by Dunbar, Richardson, and Robertsson (2013): “Unmet expectation seems to be a major cause of unsatisfactory outcomes and satisfaction is most strongly correlated with relief of pain, followed by improvement in physical function.” Objective: To develop patient reported outcome (PRO) recovery graphs for knee function, activity level, and pain relief to be used as a shared decision making tool for total knee replacement surgery.

Methods

A proprietary joint arthroplasty database of patient reported outcomes (PROs) was analyzed to determine the recovery curve means and standard deviations of four PROs at six time points: pre-operatively, 6 weeks, 3 months, 6 months, 1 year, and 2 years post-operatively for total knee replacement surgery. The recovery graphs are stratified by percentile (10%, 26%, 50%, 75%, and 90%) The PROs analyzed were: (1) European quality of life (EQ-5D); Oxford Knee Score (OKS); (3) Lower Extremity Activity Scale (LEAS); and (4) Likert Pain Scale (LPS). The minimum clinically important difference (MCID) was calculated using a distribution method where the MCID equals one half the standard deviation of the score change, MCID = σΔ/2. The LEAS and LPS are used to measure patients’ expectations for pain relief and activity improvement. Prior to discussing surgery, patients are asked to report their pre-operative pain and activity levels and to specify their expected pain relief and activity improvement one year after surgery.

Introduction

Orthopaedic departments are increasingly put under pressure to improve services, cut waiting lists, increase efficiency and save money. It is in the interests of patients and NHS organisations to ensure that operating theatre resources are used to best effect to ensure they are cost effective, support the achievement of waiting time targets and contribute to a more positive patient experience.

Patients in the UK are expected to have undergone surgery once decided within 18 weeks. A good system of planning and scheduling in theatre enables more work, however is largely delegated to non-clinical managerial and administrative staff. After numerous cancellations of elective cases due to incomplete pre-operative work-up, unavailable equipment and patient DNAs, we decided to introduce a surgeon-led scheduling system.

Intervention

The surgeon-led scheduling diary involved surgeons offering patients a date for surgery in clinic. This allowed for appropriate organisation of theatre lists and surgical equipment, and pre-operative assessment.

Introduction

Failure of the neck-stem taper in one particular bi-modular primary hip stem due to corrosion and wear of the neck piece has been reported frequently1, and stems were recalled. A specific pattern of material loss on the CoCr neck-piece taper in the areas of highest stresses on the proximal medial male taper was observed in a retrieval study of 27 revised Rejuvenate implants revised after 3 to 38 month time in situ (Stryker, Kalamazoo, MI, USA) (Figure 1). One neck piece exhibited additionally wear marks at the distal end of the flat male neck taper indicating contact with the female taper of the stem. The purpose of this study was to understand the observed failure scenario of bottoming-out by investigating the stem taper morphologies.

Materials and Methods

The geometry of taper contact surfaces was determined using a Coordinate Measurement Machine (BHN 805, Mitutoyo, Japan). An algorithm based on the individual unworn areas of the respective taper surfaces was applied to all retrievals. One retrieval is additionally investigated by infinite focus microscopy (G4, Alicona, Austria) in the main wear areas on the neck piece taper, and the bottom, facing each other inside the junction (surfaces of the distal end of the male and the bottom of the female taper).

Introduction

In orthopaedics one of the most common complications is infection. The occurrence of a postoperative infection significantly increases the failure rate; both in the case of prosthetic and trauma surgery. Some patients despite a meticulous antiseptic procedures, a close monitoring of controls peri- and post-operative undergo the development of infection of the fixation devices with the risk of developing osteomyelitis. This risk is highly increased in the distal leg because of the known problems with blood supply and poor muscle coverage. The functionality of the affected segment is impaired, quoad fuctionem, with increased risk of amputation and sometimes with poor prognosis, quoad vitam. The therapeutic strategy proposed by our group is to treat an osteomyelitic site as a pseudo-tumor with a megaimplant following a ladder strategy driven by the NUSS classification. This work shows our experience with a developing system by Waldemar-LINK highlighting critical issues and preliminary results.

Objectives

The purpose of this study is to evaluate retrospectively the early outcome after the implantation of this megaprosthesis of the lower leg in infected post-traumatic bone defects and septic peri-device bone loss. We registered all the complications and infection recurrence.

Introduction

Throughout the world the number of large joint arthroprosthetic implants continues to increase and consequently the number of septic complications with prosthesis mobilizations, periprostehtic bone loss or non-unions. The implant of large resection prosthesis (megaprosthesis) in selected patients could be a good solution both in hip and knee infected prosthesis with bone defects.

The two stage techniques with a first operation to debride, prosthesis components removal and antibiotic spacer implantation followed by a subsequent final prosthetic implant offer great results even in highly complex patients.

Objectives

The purpose of this study is to evaluate retrospectively the outcome after the implantation of megaprosthesis of the lower limbs in prosthetic infected revision.

Introduction

Various anti-infective agents can be added to the surface of orthopaedic implants to actively kill bacteria and prevent infection. Silver (Ag) is a commonly used agent in various anti-infective applications. Silver disrupts bacterial membranes and binds to bacterial DNA and to the sulfhydryl groups of metabolic enzymes in the bacterial electron transport chain, thus inactivating bacterial replication and key metabolic processes. Recently we are implanting Silver coated megaprosthesis for the treatment of post-traumatic septic non unions/bone defects and for infected hip or knee prosthesis revision. We treat these complications utilizing a two steps procedure: 1° step: devices removal, resection, debridment and antibiotic spacer implantation; 2° step: spacer removal and megaprosthesis implantation. This technique produce a reactive pseudosynovial membrane, well known in traumatology (Masquelet technique), following the Chamber Induction Technique principles. This chamber creates the perfect environment in which implant the prosthesis with safety. We are nowadays investigating if this membrane could optimize the Silver antimicrobical effects reducing the Silver ions dispersion and reducing toxicity on the human body.

Objectives

The aim of this study is to perform a review of the literature about Silver coated implants in Orthopaedics and Trauma and to analyze our cases treated with this implants in order to measure their efficacy and the ion dispersion in urine and blood.

INTRODUCTION

The hip arthroplasty implant is currently growing up both in orthopedic and trauma practice. This increases the frequency of prosthesis revision due to implant loosening often associated with periprosthetic osteolysis that determine the failure and lead to a loss of bone substance. Nowadays there are numerous biotechnologies seeking to join or substitute the autologous or omologous bone use. These biotechnologies (mesenchymal stromal cells, growth factors and bone substitutes) may be used in such situations, however, the literature doesn't offer class 1 clinical evidences in this field of application.

MATERIALS AND METHODS

We performed a literature review using the universally validated search engines in the biomedical field: PubMed / Medline, Google Scholar, Scopus, EMBASE. The keywords used were: “Growth Factors”, “Platelet Rich Plasma”, “OP-1”, “BMP”, “BMP-2”, “BMP-7”, “Demineralized Bone Matrix”, “Stem Cell”, “Bone Marrow”, “Scaffold”, “Bone Substitutes” were crossed with “hip”, “revision”, “replacement” / “arthroplasty”, “bone loss” / “osteolysis.”

Methods

The PubMed database was searchedbetween 2000 and 2015 for papers using “metal sensitivity /allergy /hypersensitivity, Adverse Local Tissue Reaction (ALTR): osteolysis, metallosis, lymphocytic infiltration, Aseptic Lymphocytic Vasculitis-Associated Lesions (ALVAL), Adverse Reaction to Metal Debris (ARMD) or pseudotumor/ pseudotumour” as well as metal-on-metal / metal-metal AND hip arthroplasty/replacement. Reports lacking soft tissue histological analysis were excluded.

Results

131 articles describing M-M tissue histology were found. In earlier studies, the terms metal sensitivity / hypersensitivity /allergy implied or stated the potential for a Type IV delayed type hypersensitivity response as a reason for revision. More recently those terms have largely been replaced by broader terms such as ALTR, ALVAL and ARMD. ALVAL and metal hypersensitivity were often used interchangeably, both as failure modes and histological findings. Several histology scoring systems have been published but were only used in a limited number of studies. Correlations of histological features with metal levels or component wear were inconclusive, typically because of a high degree of variability. Interestingly, there were very few descriptions that concluded that the observed reactions were benign / normal or anticipated i.e. regardless of the histological features, extent of debris or failure mode, the histology was interpreted as showing an adverse reaction.

Methods

Twenty-six monoblock, CoCr Birmingham Hip Resurfacing (BHR, Smith and Nephew, TN, USA) cups with macroscopic beads and hydroxyapatite coating were studied. Seventeen were revised for acetabular malposition with the remainder revised for femoral loosening (4), pain (1), infection (1), dislocation (1) or lysis (2). Median time to revision was 35 months (10 – 70 months). Ten patients were female; the median age of all patients was 54 years. The pre-revision radiographs were visually ranked for cup-bone integration as follows: 0 = none, 1 = < 50%, 2 = 50 – 75%, 3 = 76 – 95%, 4 = > 96% integration. Rankings were made for the superior and inferior aspects, without knowledge of the appearance of bone on the retrievals. The revised cups were photographed at an angle so the dome and the cup periphery were visualized. The area of bone in four equal segments in each of the superior and inferior aspects was measured with image analysis software. A probe was used to differentiate bone from soft tissue. Only bone that covered the beads was counted. Correlation coefficients were calculated for the radiographic and image analysis data.

Results

Radiographically, most cups were assessed as having more than 50% of bone attachment and 7 cups were ranked as having almost total integration with bone. Only 2 cups were assessed radiographically as fully loose. Measured total bone attachment ranged from none to 55%. Superior and inferior percent ingrowth were highly correlated (corr=0.68, p<0.001) but there was no correlation between percent bone and x-ray rank (inferior corr=0.01, p=0.96; superior corr=0.23, p=0.26). There was no correlation between cup malpositioning as a reason for revision and x-ray integration ranking (superior p=0.34; inferior p=0.80).

BACKGROUND

This scientific work is a non-interventional, experimental and prospective comparative study of two very high-viscosity PMMA bone cements: DePuy CMW 2G and Palacos® fast R+G. Reference product: Palacos® R+G.

Fast-setting PMMA bone cements are used in the endoprothetics of the patella and knee (in Australia) and are also used to cement an artificial acetabulum (in the UK). Are there any differences regarding the characteristics of the two fast-setting PMMA bone cements?

MATERIALS AND METHODS

All cements were mixed as specified by the manufacturer and analysed on the following parameters: handling properties (mixing, waiting, working and hardening phase), powder/liquid-ratio, mechanical properties (ISO 5833:2002 and DIN 53435), fatigue strength (ISO 16402) and elution profile. All tests were done in an acclimatised laboratory with temperatures set at 23.5°C ± 0.5°C and a humidity of >40%. Of two batch numbers, 11 units of each bone cement were tested.

INTRODUCTION

Wettability of bearing couples has always been related to the tribological performance of implants, and it is understood to affect lubrication of surfaces. So far researchers fail to understand the real mechanisms governing the lubrication process of prostheses. Different models attempt to explain the phenomena, but more research is needed. To add more difficulties, some classical measuring techniques have provided inaccurate values of surface properties. For instance, wettability may seem a priori a simple technique capable of providing easy-to-read cost-effective information. However, ignoring surface preparation may lead to wrong values of wettability and mis-understanding of the results.

OBJECTIVES

The dependence of wettability of commercial bearing materials used in arthroplasty has been studied as a function of the cleaning procedure, showing the variability of the results, and providing a series of guidelines to understand and perform wettability measurements.

Introduction

Superficial wound complications can occur in up to 10% of total knee arthroplasty (TKA) patients and have been associated with deep infection. The ideal material for TKA closure should fulfill the following requirements: 1) fast intraoperative application, 2) minimal wound complications and discomfort, and 3) can be removed by patients without a home care visit. We present our experience with a novel, non-invasive, removable skin closure system compared to conventional staple closure.

Methods

We prospectively evaluated 105 consecutive patients who underwent unilateral or bilateral primary TKA and received skin closure consisting of the Zip 16 Surgical Skin Closure System (Zipline) for skin. All procedures were performed a by single surgeon (SBH) using a mini-midvastus approach. All patients were mobilized on the day of surgery and received 2 weeks of Rivaroxaban thromboprophylaxis. Patient demographics, medical comorbidities, in-hospital complications and wound healing and complications during the first 6-week post-operatively were recorded. Data was compared to a previous TKA cohort of 1,001 patients from the same surgeon who received staples for closure and warfarin for thromboprophylaxis.

Introduction

Positioning of a femoral sizing guide has been cited as being a critical intraoperative step during measured-resection based TKA as it determines femoral component rotation. Consequently, modern femoral sizing guides permit surgeons to ‘dial in’ external rotation when placing the guide. Although this feature facilitates guide placement, its effect on posterior femoral condylar resection and flexion gap stability is unknown. This study examines the effect of rotation on posterior femoral condylar resection among different posterior-referencing TKA designs.

Methods

Left-sided posterior-referencing femoral sizing guides and cutting blocks from nine posterior-referencing femoral sizing guides belonging to six TKA manufacturers were collected. Each guide underwent high-resolution photography at a setting of zero, three and greater than three degrees of external rotation. The axis of rotation for each guide was then identified and its location from the posterior condylar axis was recorded (figure). Cutting blocks from each system were then photographed and the amount of posterior condylar resection from the medial and lateral condyles was calculated for each setting of external rotation (figure). The posterior resection was then compared to the standard distal resections for each system.

Introduction

Cementless fixation is the current preferred method for acetabular reconstruction in total hip arthroplasty (THA). Despite promising long-term results among several designs, theoretic concerns regarding the high modulus of elasticity, low friction against bone and low volumetric porosity of contemporary cementless cups have spurred the introduction of novel porous surfaces that are designed to improve osseointegration and decrease aseptic loosening. Although several novel surfaces have been introduced into clinical use over the past decade, very little literature regarding their clinical and radiographic performance exists. The current study investigates the performance of one such novel surface, Tritanium (Stryker, Mahwah, NJ).

Methods

We prospectively evaluated 121 consecutive THAs performed in 94 patients by a single arthroplasty surgeon using the Tritanium Primary Acetabular Component (Stryker, Mahwah, NJ). 109 hips (90.1%) had adequate clinical and radiological follow-up for analysis. Clinical parameters recorded included implant survivorship, Harris Hip Scores, WOMAC and SF-12. Furthermore, radiographs at the 6-week, 1 year and most recent clinical visit were evaluated by two blinded observers for implant position, evidence of radiolucency, sclerosis and component migration.

Introduction

The longevity of total hip arthroplasty (THA) is dependent on acetabular component position. We measured the reliability and accuracy of a CT-based navigation system to achieve the intended acetabular component position and orientation using three dimensional imaging. The purpose of the current study was to determine if the CT-guided robotic navigation system could accurately achieve the desired acetabular component position (center of rotation (COR)) and orientation (inclination and anteversion). The postoperative orientation and location of the components was determined in 20 patients undergoing THA using CT images, the gold standard for acetabular component orientation.

Methods

Twenty primary unilateral THA patients were enrolled in this IRB-approved, prospective cohort study to assess the accuracy of the robotic navigation system. Pre- and post-operative CT exams were obtained and aligned 3D segmented models were used to measure the difference in center of rotation and orientation (anteversion and inclination). Patients with pre-existing implants, posttraumatic arthritis, contralateral hip arthroplasty, septic arthritis, or previous hip fracture were excluded. All patients underwent unilateral THA using robotic arm CT-guided navigation (RIO Makoplasty; MAKO Surgical Corp).

Introduction

The current recommendation by the AAOS in the 2010 clinical practice guidelines for the use of MRI to diagnose a periprosthetic joint infection (PJI) is “inconclusive” given the lack of evidence to support its use. The purpose of this study was to determine the utility of MRI with metal reduction artifact sequencing in diagnosing a periprosthetic joint infection (PJI) after total hip arthroplasty (THA).

Methods

176 patients who underwent MRI with multi-acquisition variable resonance image combination (MAVRIC) to reduce metal artifact for a painful THA between the years of 2009–2013 were retrospectively evaluated. All MRIs were read by one of four radiologists with extensive experience in interpreting MRIs after THA. All MRIs were performed using a 1.5 Tesla magnet. Of the 176 patients examined, 16 patients were found to have a deep periprosthetic joint infection using Musculoskeletal Infection Society (MSIS) criteria after the MRI was performed. MRI reads were classified as either positive (read as “evidence of active infection” or “suspicious for infection”) or negative (read as no evidence of infection). Only one patient who had a positive MRI read was excluded because of loss to followup after the MRI was performed.

Introduction

Deformity of knee joint causes deviation of mechanical axis in the coronal plane, and the mechanical axis deviation also could adversely affect biomechanics of the ankle joint as well as the knee joint. Particularly, most of the patients undergoing total knee arthroplasty (TKA) have significant preoperative varus malalignment which would be corrected after TKA, the patients also may have significant changes of ankle joint characteristics after the surgery. This study aimed 1) to examine the prevalence of coexisting ankle osteoarthritis (OA) in the patients undergoing TKA due to varus knee OA and to determine whether the patients with coexisting ankle OA have more varus malalignment, and 2) to evaluate the changes of radiographic parameters for ankle joint before and 4 years after TKA.

Methods

We evaluated 153 knees in 86 patients with varus knee OA who underwent primary TKA. With use of standing whole-limb anteroposterior radiographs and ankle radiographs before and 4 years after TKRA, we assessed prevalence of coexisting ankle OA in the patients before TKA and analyzed the changes of four radiographic parameters before and after TKA including 1) the mechanical tibiofemoral angle (negative value = varus), 2) the ankle joint orientation relative to the ground (positive value = sloping down laterally), 3) ankle joint space, and 4) medial clear space.

Introduction

Glenoid loosening, still a main complication in shoulder arthroplasty, could be related to glenohumeral orientation and conformity, cementing techniques, fixation design and periprosthetic bone quality [1,2]. While past numerical analyses were conducted to understand the relative role of these factors, so far none used realistic representations of bone microstructure, which has an impact on structural bone properties [3]. This study aims at using refined microFE models including accurate cortical bone geometry and internal porosity, to evaluate the effects of fixation design, glenohumeral conformity, and bone quality on internal bone tissue and cement stresses under physiological and pathological loads.

Methods

Four cadaveric scapulae were scanned at 82µm resolution with a high resolution peripheral quantitative computer tomography (XtremeCT Scanco). Images were processed and virtually implantated with two anatomical glenoid replacements (UHMWPE Keeled and Pegged designs, Exactech). These images were converted to microFE models consisting of nearly 43 million elements, with detailed geometries of compact and trabecular bone, implant, and a thin layer of penetrating cement through the porous bone. Bone tissue, implant and cement layer were assigned material properties based on literature. These models were loaded with a central load at the glenohumeral surface, with the opposite bone surface fully constrained. Effects of glenohumeral conformity were simulated with increases of the applied load area from 5mm-radius to a fully conformed case with the entire glenoid surface loaded. The models were additionally subjected to a superiorly shifted load mimicking torn rotator cuff conditions. These models were solved and compared for internal stresses within the structures (Figure 1) with a parallel solver (parFE, ETH Zurich) on a computation cluster, and peak stresses in each region compared by design and related to apparent bone density.

Background

Joint replacement surgery has been shown to be successful in post solid organ transplantation patients. However, complication rates, revision rates, and overall mortality can be higher in this population compared to patients who have not undergone solid organ transplantation. Many transplant patients have a decreased life expectancy. Therefore, literature suggests that joint replacement surgery be offered to qualifying patients early on when symptomatic. This study compares the outcomes of patients who have undergone solid organ transplantation as well as a joint replacement to patients that have only undergone joint replacement surgery.

Methods

We retrospectively gathered 42 transplant (T) patients over a ten year period, 2003–2013, that underwent a liver (21) or kidney (21) transplant as well as primary total knee arthroplasty (TKA) (23) or total hip arthroplasty (THA) (19). We then gathered 42 non-transplant (NT) patients matched for procedure, age, body mass index (BMI), American Society of Anesthesiologists (ASA) score, and age adjusted Charlson co-morbidity index (ACCI) score who only underwent TKA or THA with no transplant. We used Chi-Square, T test, and multivariate analysis to compare the two groups with regard to number of complications (NOC), readmissions at 30 and 90 days post surgery, length of stay (LOS), number of intensive care unit (ICU) admissions, and total direct cost (TDC) per hospital stay.

Background

The Perioperative Surgical Home (PSH) is a multi-disciplinary rapid recovery pathway aimed at transforming surgical care by delivering value and improving outcomes and patient satisfaction. Our institution developed a PSH pathway for total hip arthroplasty (THA) patients in March 2014. The Orthopaedic and Anesthesia Services co-managed the patients throughout the entire surgical process. Weekly meetings were held to discuss medical and social requirements for upcoming patients including disposition planning. All patients received day of surgery physical therapy, and anesthesia post-surgical pain control and medical co-management. We hypothesized that the PSH would provide enhanced care for THA patients. To our knowledge this is the first report on the PSH in a total joint population

Methods

We prospectively followed 180 THA patients from the PSH group (SH) and compared them to a group matched for age, body mass index (BMI), American society of anesthesiologist score (ASA), and Charleson comorbidity index score (CCI) that were not involved in the PSH (NSH). We used Wilcoxon, Chi square, and multivariate analysis to compare the groups for length of stay (LOS), total direct cost (TDC), complications, readmissions at 30 days, and discharge disposition location.

Introduction

Failure of acetabular components has been reported to lead to large bone defects, which determine outcome and management after revision total hip arthroplasty (THA). Although Kerboull-type (KT) plate (KYOCERA Medical Corporation, Kyoto, Japan) has been used for compensating large bone loss, few studies have identified the critical risk factors for failure of revision THA using a KT plate. Therefore, the aim of this study is to evaluate the relationship between survival rates for radiological loosening and the results according to bone defect or type of graft.

Patients and methods

This study included patients underwent revision THA for aseptic loosening using cemented acetabular components with a KT plate between 2000 and 2012. Bone defects were filled with beta Tricalcium phosphate (TCP) granules between 2000 and 2003 and with Hydroxyapatite (HA) block between 2003 and 2009. Since 2009, we have used femoral head balk allografts. Hip function was evaluated by using the Japanese Orthopaedic Association (JOA) score and University of California, Los Angeles (UCLA) activity. Acetabular defects were classified according to the American Academy of Orthopedic Surgeons (AAOS) classification. The postoperative and final follow-up radiographs were compared to assess migration of the implant. Kaplan–Meier method for cumulative probabilities of radiographic failure rate, and the comparison of survivorship curves for various subgroups using the log-rank test were also evaluated. Logistic regression was performed to examine the association of such clinical factors as the age at the time of operation, body mass index, JOA score, UCLA activity score, and AAOS classification with radiographic failure. Odds ratios (ORs) and 95% CIs were calculated. Multivariate analysis was performed to adjust for potential confounders by clinical factors. Values of p < 0.05 were considered significant.

Purpose

To perform comparative analysis between the results of internal fixation using proximal femoral nail system and bipolar hemiarthroplasty in pantrochanteric hip fracture in elderly patients.

Materials and Methods

From January 2006 to February 2012, we reviewed 43 patients, who were treated surgically for pantrochanterichip fractures, with a minimum of 2 years follow up. The patient's age was older than 70 year old. The patients were divided into three groups and evaluated, retrospectively. The fracture reduction were regarded as satisfactory in S-OR-IF group(17 cases) and unsatisfactory in US-OR-IF group(9 cases) and the other group was treated with bipolar hemiarthroplasty (BHA group, 17 cases.)

Introduction

The supercapsular percutaneously-assisted total hip (SuperPath) replacement surgical technique was developed as a hybrid of the supercapsular (SuperCap) and percutaneously-assisted total hip (PATH) approaches. The technique does not require any muscle release and preserves the external rotators with the objectives of reducing hospital length of stay, increasing the percentage of subjects discharged home, and decreasing complications (e.g. dislocation). The purpose of this study was to evaluate these perioperative outcomes associated with a large consecutive cohort of prospectively followed subjects.

Patients and Methods

Four hundred eighty-six (486) consecutive total hip replacements (THRs) were performed using the SuperPath technique in 469 subjects between April 29, 2010 and December 31, 2013 and prospectively followed. Perioperative outcomes including length of stay, discharge status, skin-to-skin surgical time, estimated blood loss, transfusions, and complications were collected. Subjects were also evaluated using Harris Hip Scores (HHS), UCLA Activity Scores, range of motion, and Numeric Rating Scale (NRS-11) Scores.

Purpose

The purpose of this study was to evaluate and compare the clinical, radiological outcomes of the group of patients with distal femoral cortical hypertrophy (DFCH) and without DFCH after hip arthroplasty using a cementless double tapered femoral stem and to analyze a correlation between patients factors and DFCH.

Materials and Methods

Four hundreds four patients (437 hips) who underwent total hip arthroplasty (n = 293) or hemiarthroplasty (n = 144) using a Accolade TMZF femoral stem between Jun 2006 and March 2012 and were follow up period more than 24 months after surgery were enrolled in this study. They were divided into 2 groups, the one group (n = 27) included patients with DFCH, and the other group (n = 410) included patients without DFCH. The mean follow up period was 54.5 months (range, 24 to 85 months) and 56.2 months (range, 24 to 92 months) for patients with DFCH and without DFCH.

Background

The optimal strategy for postoperative deep venous thrombosis (DVT) prophylaxis remains among the most controversial topics in hip and knee arthroplasty. Warfarin, the most commonly used chemical anticoagulant, initially causes transient hypercoagulability; however the optimal timing of treatment with respect to surgery remains unclear. Our purpose was to evaluate the effects of pre- versus postoperative initiation of warfarin therapy with a primary endpoint of perioperative change in hemoglobin (pre- minus post-operative level), with secondary endpoints of postoperative International Normalized Ratio (INR), drain output, and bleeding/thrombotic events.

Methods

A quasi-experimental study design was employed, under which patients were assigned to begin taking warfarin the night prior to surgery or the night following surgery based on day of the week seen in clinic. An a priori power analysis was conducted in order to ensure appropriate enrollment to detect a 0.5 g/dL difference in perioperative change in hemoglobin between groups, given an alpha level of 0.05 and beta of 0.80. Based on the results, the study included all primary, elective total hip and knee arthroplasties performed by a single surgeon over a 12 month period. Fifteen patients were excluded (7 chronic anticoagulation, 3 hip fractures, 2 medical contraindications, 3 simultaneous procedures), leaving 165 cases (108 hips, 57 knees) available for study. Of these, 73 received warfarin preoperatively (49 hips, 24 knees) and 92 postoperatively (59 hips, 33 knees). Warfarin was dosed according to a standard nomogram in both groups. INR (on postoperative days 1 and 2), perioperative decrease in hemoglobin (difference between level preoperatively and on postoperative days 1 and 2), and drain outputs were compared between groups using a student t test. Adverse events (transfusions, hematomas, epidural complications, and pulmonary embolus) were compared using two-tailed Fischer's exact test.

Results

PROMs for the two groups were almost identical, while HRA scored higher in the PCOM. The 9% difference was significant (p<0.05). At top walking speed, HRA were 10% faster, with a 9% longer stride length, both of these metrics also reached significance.

Discussion

Function following hip replacement is very good, with high satisfaction rates, but the use of a PCOM, and objective measures of function reveal substantial inferiority of THA over THR in two well matched groups. This 9% difference is well over the 5% difference that is considered ‘clinically relevant’. When coupled with the very strong data regarding life expectancy and infection, this functional data makes a compelling case for the use of resurfacing in active adults.

Materials and Methods

Of 201 patients measured following knee arthroplasty, 31 unicondylar patients and 35 total knee patients, with a single primary arthroplasty, and no co-morbidities, over 1 year post-operatively were identified. Two control groups of controls, a younger cohort of 112 people and 17 in an age matched older cohort.

All operations were performed by the same surgeon. The total knees were cruciate retaining devices, inserted in mechanical alignment, and the unicondylar knees were inserted retaining the native alignment and joint-line obliquity.

The gait of all subjects was analysed on an instrumented, calibrated treadmill with underlying force plates. Patients start by walking at a comfortable speed for them for 5 minutes, before the speed of the treadmill is increased at 1/2 km/h increments until maximum walking speed obtained, spending 30 seconds at each. After the flat test, it was then repeated on a downhill slope of 6°.

Base of Support is interpreted as the distance between the centre point of heel strike and toe off from one foot to that of the other.

The top walking speed in the unicondylar group was significantly greater than that of the total knee group, as we reported in 2013.

TKA patients have an average BoS of 14cm, while UKA patients and controls have a 12cm BoS. The BoS did not reduce with speed. This 2cm, or 17% increase in BoS is significant. Shapiro-Wilk tests demonstrate a normal distribution to the results, and ANOVA testing reveals a significant difference (p<0.05) within the groups between the speeds of 4.5 to 9. Post-Hoc Bonferroni testing reveal a significant difference between the TKA group and each of the other three groups.

On the downhill test (figure 1), the mean BoS in the TKA group increased to 16cm. This increase is highly significant, with a p value of <0.001, while the increase in the UKA group at higher speeds failed to reach significance, and the controls both stayed at 12cm. 6 Bi-uni knees tested acted just like the UKAs.

Discussion

A narrow base of support minimises excessive loads across the joint line. Maintenance of jointline obliquity and an ACL enables this feature to be returned to normal following uni, or bi-uni, while a well aligned TKA seems to prevent it.

Introduction

Preoperative templating of femoral and tibial components can assist in choosing the appropriate implant size prior to TKA. While weight bearing long limb roentograms have been shown to provide benefit to the surgeon in assessing alignment, disease state, and previous pathology or trauma, their accuracy in size prediction is continually debated due to scaling factors and rotated views. Further, they represent a static time point, accounting for boney anatomy only. A perceived benefit of robotic-assisted surgery is the ability to pre-operatively select component sizes with greater accuracy based on 3D information, however, to allow for flexibility in refining based on additional data only available at the time of surgery.

Methods

The purpose of this study was to determine the difference of pre-operative plans in size prediction of the tibia, femur, and polyethylene insert. Eighty four cases were enrolled at three centers as part of an Investigational Device Exemption to evaluate a robotic-assisted TKA. All patients had a CT scan as part of a pre-operative planning protocol. Scans were segmented and implant sizes predicted based on the patients boney morphology and an estimated 2mm cartilage presence. Additional information such as actual cartilage presence and soft tissue effects on balance and kinematics were recorded intra-operatively. Utilizing this additional information, surgical plans were fine tuned if necessary to achieve minimal insert thickness and balance. Data from the Preoperative CT plan sizing and final size were compared to determine the percentage of size and within one size accuracy.

Introduction

Total knee arthroplasty (TKA) is a well established treatment option for patients with end stage osteoarthritis. Conventional TKA with manual instruments has been shown to be a cost effective and time efficient surgery. While robotic-assisted operative systems have been shown to have benefits in surgical accuracy, they have also been reported to have longer surgical times. The purpose of this work was to determine surgical time and learning curve for a novel robotic-assisted TKA platform.

Methods

Eighty-five subjects underwent robotic-assisted TKA by one of three investigators as part of an FDA and IRB approved Investigational Device Exemption (IDE). All patients received a cruciate retaining total knee implant system. Intra-operative safety, Western Ontario and McMaster Universities Arthritis Index (WOMAC) and Knee Society Scores (KSS) were collected pre-operatively and at three month follow-up. In addition, surgical times were collected as part of a TKA work flow. To identify activities related to surgical steps required for robotic procedures specific time stamps were determined from the system. Capture of the hip center to final bone cut was used to define case time and identify robotic learning curve. Descriptive statistics were used to analyze results.

INTRODUCTION

Bicompartmental knee arthroplasty (BKA) is an alternative to total knee arthroplasty (TKA) for degenerative joint disease when present in only two compartments. BKA spares the cruciate ligaments and preserves bone in the healthy compartment, possibly leading to better knee kinematics and clinical outcomes when compared to TKA. While BKA is a technically demanding procedure when performed with manual instrumentation, robotic assistance allows for accurate implant placement and soft tissue balancing of the joint. Robotic unicompartmental knee arthroplasty (UKA) has shown favorable clinical outcomes and survivorship at short term (2 year) follow up compared to manual UKA. The purpose of this study is to evaluate the short term functional outcomes and survivorship of patients undergoing robotically assisted BKA.

METHODS

45 patients (48 knees) were identified in an initial and consecutive single surgeon series receiving robotically assisted BKA to correct disease in the medial and patellofemoral compartments. As part of an IRB approved study, every patient in the series was contacted at a minimum two year (±2 months) follow up and asked a series of questions to determine implant survivorship and functional outcomes (using the patient portion of the Knee Society Score). 9 patients were lost to follow up and 1 patient was deceased. 35 patients (38 knees) at a minimum two year follow up enrolled in the study for an enrollment rate of 79%. There are 22 male patients and 13 female patients; the average age at time of surgery is 67.0 ± 6.8 and the average BMI is 29.5 ± 4.6. Five patients in this series also qualified for a 5 year follow up assessment.

Introduction

There is a demand for longer lasting arthroplasty implants driving the investigation of novel material combinations. PEEK has shown promise as an arthroplasty bearing material, with potentially relatively bio inert wear debris [1]. When coupled with an all-polyethylene tibial component this combination shows potential as a metal-free knee. In this study, the suitability of PEEK Optima® as an alternative to cobalt chrome for the femoral component of total knee replacements was assessed using experimental knee wear simulation under two kinematic conditions.

Methods

Three cobalt chrome and three injection moulded PEEK Optima® (Invibio Biomaterial Solutions, UK) femoral components of similar geometry and surface roughness (mean surface roughness (Ra) ∼0.02µm) were coupled with all-polyethylene GUR1020 (conventional, unsterilised) tibial components in a 6 station ProSim knee simulator (Simulation Solutions, UK). 3 million cycles (MC) of wear simulation were carried out under intermediate kinematics (maximum anterior-posterior (AP) displacement 5mm) followed by 3MC under high kinematics (AP 10mm) [2] with 25% serum as the lubricant. The wear of the tibial component was assessed gravimetrically. At each measurement point, the surface roughness of the femoral components was determined using contacting profilometry and throughout testing, the bulk lubricant temperature was monitored close to the articulating surfaces.

Statistical analysis was carried out using ANOVA, with significance at p<0.05.

Introduction

Computer-assisted orthopaedic surgery (CAOS) provides great value in ensuring accurate, reliable and reproducible total knee arthroplasty (TKA) outcomes [1,2]. Depending on surgeon preferences or patient factors (e.g. BMI, ligament condition, and individual joint anatomy), resection planning (guided adjustment of cutting blocks) is performed with different knee flexion, abduction/adduction (ABD/ADD) and internal/external (I/E) rotation angles, potentially leading to measurement errors in the planned resections due to a modified tracker/localizer spatial relationship. This study assessed the variation in the intraoperative measurement of the planned resection due to leg manipulation during TKA, and identified the leg position variables (flexion, ABD/ADD, and I/E rotation) contributing to the variability.

Materials and Methods

Computer-assisted TKA (ExactechGPS®, Blue-Ortho, Grenoble, FR) was performed on a neutral whole leg assembly (MITA knee insert and trainer leg, Medial Models, Bristol, UK) by a board-certified orthopaedic surgeon (BH) at his preferred leg flexion, ABD/ADD, and I/E rotation angles. A cutting block was adjusted and fixed to the tibia, targeting the resection parameters listed in Table 1A. An instrumented resection checker was then attached to the cutting block to measure the planned resection at the same leg position (baseline). Next, the surgeon moved the leg to 9 sampled positions, representing typical leg position/orientation associated with different steps during TKA [Table 1B]. The planned resection was tracked by the CAOS system at each leg position.

Tibial resection parameters at each sampled position were compared to the baseline. Regression was performed to identify the variables (flexion, ABD/ADD, I/E rotation) that significantly contribute to the measured variation (p<0.05).

Introduction

Evaluations of Computer-assisted orthopaedic surgery (CAOS) systems generally overlooked the intrinsic accuracy of the systems themselves, and have been largely focused on the final implant position and alignment in the reconstructed knee [1]. Although accuracy at the system-level has been assessed [2], the study method was system-specific, required a custom test bench, and the results were clinically irrelevant. As such, clinical interpolation/comparison of the results across CAOS systems or multiple studies is challenging. This study quantified and compared the system-level accuracy in the intraoperative measurements of resection alignment between two CAOS systems.

Materials and Methods

Computer-assisted TKAs were performed on 10 neutral leg assemblies (MITA knee insert and trainer leg, Medial Models, Bristol, UK) using System I (5 legs, ExactechGPS®, Blue-Ortho, Grenoble, FR) and System II (5 legs, globally established manufacturer). The surgeries referenced a set of pre-defined anatomical landmarks on the inserts (small dimples). Post bone cut, the alignment parameters were collected by the CAOS systems (CAOS measured alignment). The pre- and post- operative leg surfaces were scanned, digitized, and registered (Comet L3D, Steinbichler, Plymouth, MI, USA; Geomagic, Lakewood, CO, USA; and Unigraphics NX version 7.5, Siemens PLM Software, Plano, TX, USA). The alignment parameters were measured virtually, referencing the same pre-defined anatomical landmarks (baseline). The signed and unsigned measurement errors between the baseline and CAOS measured alignment were compared between the two CAOS systems (significance defined as p<0.05), representing the magnitude of measurement errors and bias of the measurement error generated by the CAOS systems, respectively.

Objectives

To examine mortality and revision rates among patients with osteoarthritis undergoing hip arthroplasty and to compare these rates between patients undergoing cemented or uncemented procedures and to compare outcomes between men undergoing stemmed total hip replacements and Birmingham hip resurfacing.

Main outcome measures

Hip arthroplasty procedures were linked to the time to any subsequent mortality or revision (implant failure). Flexible parametric survival analysis methods were used to analyse time to mortality and also time to revision. Comparisons between procedure groups were adjusted for age, sex, American Society of Anesthesiologists (ASA) grade, and complexity.

Background

KAR™ prosthesis was introduced following the success of Corail® femoral stem to tackle difficult revision cases (Paprosky type1, 2a, 2b and 3a). The ARTO group reported a success rate of 94% at 17 years follow-up. Only two independent studies reported similar success rate to date.

Purpose

To analyse the short-term performance of the KAR™ prosthesis used in our unit.

Purpose

External rotation of the femoral component is one factor that favors a satisfactory clinical result. New technologies have been developed to precisely implant the components of a total knee arthroplasty, including computer-assisted surgery (CAS) and patient-specific instruments (PSIs). The aim of this study was to compare the precision of CAS and PSIs when determining the orientation of the femoral component.

Methods

A total of 65 patients operated on in 2008 with CAS had pre- and post-operative computed tomography (CT) in which the posterior condylar angle (PCA) was measured. The same pre- and post-operative measurements were performed for 27 patients operated on in 2010 with the assistance of PSI. For both populations, the antero-posterior femoral cuts were directed to implant the femoral component 3° of external rotation from the pre-operative posterior condylar line (PCL).

Introduction

A previous computational study on an all-polymer PEEK-on-UHMWPE total knee replacement implant showed improved periprosthetic bone loading, compared to a conventional implant [1]. That study used a simulated gait cycle to determine distal loading, but a patella was not included. Substantial distal decrease of bone remodeling stimulus was found, in accordance with previous reports [2], but it was not consistent with other clinical and post-mortem DEXA results, which found the largest loss of bone stock in the anterior region [3,4]. As patellofemoral forces are relatively low during gait compared to squatting, we simulated a deep squat, expecting that a high-demand activity would provide similar indications of bone loss as literature [3,4]. Consequently, we applied both high tibiofemoral and patellofemoral loads, to provide more insight in the potential benefits of a new PEEK-Optima® femoral component on periprosthetic bone stock.

Methods

We adopted a deep squat finite element model from Zelle et al. and included quasi-static deep flexion and load sharing at the posterior condyles [6]. A new implant design was inserted, with three variations in material properties: intact, CoCr and PEEK. The stiffness of the femoral elements was mapped from CT and applied to either the cut femur only (CoCr and PEEK) or the entire femoral construct (intact). The strain energy density (SED) was evaluated in the periprosthetic region as a measure for bone remodeling stimulus. To examine the effects of the entire exercise, SED values were integrated over all increments.

Background and aim

Arthroplasty registries and consecutive series indicate significantly worse results of conventional metal-on-polyethylene total hip arthroplasty (THA) in patients younger than 50 years compared to older patients, with inferior clinical outcomes and 10-year survivorship ranging between 70 and 90%. At our institution, patients under 50 needing a THA receive either a metal-on-metal hip resurfacing (MoMHRA) or a ceramic-on-ceramic (CoC)THA. In order to evaluate the outcome of these options at minimum 10 years, we conducted a retrospective review of all MoMHRA and CoCTHA with more than 10 years follow-up implanted in patients under 50.

Methods

From a single surgeon patients’ prospective database, we identified all consecutive THA performed before May 2005 in patients under 50. All patients are contacted by phone and asked to present for a clinical exam and patient reported outcome questionnaires, standard radiographs and metal ion measurements unless the hip arthroplasty has been revised. Complications and reasons for revision are noted. Kaplan-Meier survivorship is analysed for the whole cohort and sub-analysis is performed by type hip arthroplasty, gender, diagnosis and component size.

Introduction

Revision of total hip replacements (THRS) is predominantly due to aseptic loosening, pain and infection [1]. The current method used to address the risk of infection is to administer antibiotics and to include antibacterial agents into bone cement (if used) and on implant coatings [2–4]. Currently, silver (Ag) coatings have only been applied to titanium hip stems [3]. Cobalt chromium alloy (CoCr) is a widely used orthopaedic alloy which is commonly used as a bearing surface; revisions of joints using this material often describe adverse reactions to the particulate wear debris [1]. This study considers an Ag containing CrN based coating on a CoCr substrate with the aim to reduce cobalt (Co) release and promote antibacterial silver release.

Methods

Silver Chromium Nitride (CrNAg) coatings were developed and applied onto the bearing surfaces of 48 mm diameter metal-on-metal THRs. Three coatings were evaluated: high Ag at the surface (CrNAg+), low Ag at surface (CrNAg-) and uniform Ag (CrNAg=). All bearings were tested under ISO 14242-3 conditions for 0.17 million cycles (mc) representing approximately 2 months use in vivo. Wear was determined gravimetrically; Ag and Co levels in the lubricant were measured using graphite furnace atomic absorption spectroscopy. Testing of the CrNAg= bearings were continued to 2mc under standard conditions; CrNAg- bearings to 5mc incorporating lateralisation, which created separation at swing phase and rim contact at heel strike. Wear volume and Ag/Co release were monitored at 0.33, 0.67, 1mc and every mc thereafter.

Materials and methods

Two different polyethylenes (UHMWPE and vitamin E blended HXLPE) and ceramics (pure aluminum PAL and alumina-toughened zirconia ATZ) were tested with a hip simulator and compared to metal-on-metal results. The inclination angle was selected at 45°, 65° and 80°. In addition, the ceramic-on-ceramic barings were tested at conditions that produced microseparation.

Results

Contrary to metal-on-metal that is highly susceptible to edge loading, the wear rate of ceramic-on-ceramic and metal-on-polyethylene articulations does not increase with increasing cup inclination. In fact, the polyethylenes showed a contra-intuitive behaviour as its wear rate decreased slightly but significantly with increasing inclination angle. This behaviour can be explained when looking closely at the contact stresses and areas. (Figure 1 shows the wear area of the vitamin E blended HXLPE at 45° and figure 2 at 80° cup inclination).

The newest biomaterials, vitamin E blended HXLPE and ATZ, showed markedly lower wear rates compared to their conventional counterparts, UHMWPE and PAL. The ATZ ceramic-on-ceramic articulation showed the lowest wear rate (even when microseparation is included) of all tested pairings, but the new vitamin-doped HXLPE seems to be the most forgiving materials when it comes to implant mal-orientation. It shows low wear rate even at an extremely high cup inclination angle. Therefore, a surgeon that discovers a mal-positioned polyethylene cup at the first post-op X-ray will not need to worry unduly about increased wear (but “only” about a potential dislocation).

Introduction

The vascular anatomy of the femoral head and neck has been previously reported, with the primary blood supply attributed to the deep branch of the Medial Femoral Circumflex Artery (MFCA). This understanding has led to development of improved techniques for surgical hip dislocation for multiple intra-capsular hip procedures including Hip Resurfacing Arthroplasty (HRA). However, there is a lack of information in the literature on quantitative analysis of the contributions of the Lateral Femoral Circumflex Artery (LFCA) to femoral head and neck. Additionally, there is a lack of detailed descriptions in the literature of the anatomic course of the LFCA from its origin to its terminal branches.

Materials & Methods

Twelve fresh-frozen human pelvic cadaveric specimens were studied (mean age 54.3 years, range 28–69). One hip per specimen was randomly assigned as the experimental hip, with the contralateral used as a control. Bilateral vascular dissection was performed to cannulate the MFCA and LFCA. Specimens were assigned as either LFCA-experimental or MFCA-experimental. All specimens underwent a validated quantitative-MRI protocol: 2mm slice thickness with pre- and post- MRI contrast sequences (Gd-DTPA diluted with saline at 3:1). In the LFCA-experimental group 15ml of MRI contrast solution was injected into the LFCA cannula. In the MFCA-experimental group 15ml of contrast solution was injected into the MFCA cannula. On the control hip contrast solution was injected into both MFCA and LFCA cannulas, 15ml each (30ml total for the control hip). Following MRI, the MFCA and LFCA were injected with polyurethane compound mixed with barium sulfate (barium sulfate only present in either MFCA or LFCA on each hip). Once polymerization had occurred, hips underwent thin-slice CT scan to document the extra- and intra-capsular course of the LFCA and MFCA. Gross dissection was performed to visually assess all intra-capsular branches of both the MFCA and LFCA and assess for extravasation. Quantitative-MRI analysis was performed based on Region of Interest (ROI) assessment. Femoral heads were osteotomized at the level of the largest diameter proximal to the articular margin and perpendicular to the femoral neck, for placement of a 360° scale. Measurements using the 360° scale were recorded. For data processing, we used right-side equivalents and integrated our 360° data into the more commonly used imaginary clock face.

Introduction

By all developments of new technologies on the improvement of the Total Knee implantation, the discussion about the optimum Alignment is in full way. Besides, is to be considered, that Alignment contains not only static, but also dynamic factors and beside the frontal plan also the sagittal plan as well as in particular the rotation in femur and tibia have a great importance for the outcome after TKR. However, beside the bone alignment, the kapsulo-igamentous structures also play an important role for the results after TKR. If a Varus-Malalignment was valid, in the past the „older” literature described it as a big risk factor for pain, less function and durability. However, in the present literature, we discuss more and more about the optimum Alignment during TKR. In particular, newer publications show no interference of the durability with coronar Alignment also outside from 3 °, also the score results and patient's satisfaction seem to deliver no worse results with slight untercorrection of the varus alignment. Some publications described even better score results and Patient satisfaction with slight untercorrection. Condition for it is probably an exact balancing of the extension and flexion gap.

Material and method

With a new developed instruments it was examined with a tibia and extensions-Gap-First-Technique, to what extent a correction of the AMA opposed after digital planning within from 3 ° in distal femur a balancierung of the extension gap could be reached under avoidance of 3° releases with a varusarthritis oft the knee. 103 directly knee arthroplasties following on each other were selected with Varus-OA without exclusion criteria.

Background

Despite the success of total knee arthroplasty (TKA) restoration of normal function is often not achieved. Soft-tissue balance is a major factor leading to poor outcomes including malalignment, instability, excessive wear, and subluxation. Mechanical ligament balancers only measure the joint space in full extension and at 90° flexion. This study uses a novel electronic ligament balancer to measure the ligament balance in normal knees and in knees after TKA to determine the impact on passive and active kinematics.

Methods

Fresh-frozen cadaver legs (N = 6) were obtained. A standard cruciate-retaining TKA was performed using measured resection approach and computer navigation (Stryker Navigation, Kalamazoo, MI).

Ligament balance was measured using a novel electronic balancer (Fig 1, XO1, XpandOrtho, Inc, La Jolla, CA, USA). The XO1 balancer generates controlled femorotibial distraction of up to 120N. The balancer only requires a tibial cut and can be used before or after femoral cuts, or after trial implants have been mounted. The balancer monitors the distraction gap and the medial and lateral gaps in real time, and graphically displays gap measurements over the entire range of knee flexion. Gap measurements can be monitored during soft-tissue releases without removing the balancer.

Knee kinematics were measured during active knee extension (Oxford knee rig) and during passive knee extension under varus and valgus external moment of 10Nm in a passive test rig.

Sequence of testing and measurement:

Ligament balance was recorded with the XO1 balancer after the tibial cut, after measured resection of the femur, and after soft-tissue release and/or bone resection to balance flexion-extension and mediolateral gaps.

INTRODUCTION

Deformation of modular acetabular press-fit shells is of much interest for surgeons and manufacturers. Initial fixation is achieved through press-fit between shell and acetabulum with the shell mechanically deforming upon insertion. Shell deformation may disrupt the assembly process of modular systems and may adversely affect integrity and durability of the components and tribology of the bearing. The aim of the study was to show shell deformation as a function of bone and shell stiffness.

METHODS

The stiffness of the generic shells was determined using a uniaxial/ two point loading frame by applying different loads, and the change in dimension was measured by a coordinate measurement machine (CMM). Cadaver lab deformation measurements were done before and after insertion for 32 shells with 2 wall thicknesses and 11 shell sizes using the ATOS Triple Scan III (ATOS) optical system previously validated as a suitable measurement system to perform those measurements. Multiple deformation measurements per cadaver were performed by using both hip sides and stepwise increasing the reamed acetabulum by at least 1 mm, depending on sufficient residual bone stock. The under-reaming was varied between 0mm and 1mm, respectively. From the deformations, the resulting forces on the shells and bone stiffness were calculated assuming force equilibrium as well as linear-elastic material behaviour in each point at the rim of the shell.

Background

Robotics assisted surgery are tools that provide successful biomechanical reconstruction of the hip. We compare the accuracy of cup placement in the safe zones described by Lewinnek et al. and Callanan et al., leg length discrepancy (LLD) and global offset (GO) measurement in total hip arthroplasty (THA) using five diferent image guided techniques performed by six diferent surgeons.

Methods

Between June 2008 and April 2014, 2330 THRs were performed by six different surgeons. Ninety-three (4.69%) patients underwent robotic-assisted THA anterior approach, 135 (6.8%) had robotic-assisted THA posterior approach, 942 (47.5%) patients underwent fluoroscopic guided THA anterior approach, 708 (35.7%) had THA without guidance using posterior approach, 43 (2.1%) patients underwent navigation-guided anterior approach and 59 (2.9%) patients underwent radiographic-guided posterior approach THAs (Figure 1).

Background

Preservation of acetabular bone during primary total hip arthroplasty (THA) is important, because proper stability of cementless acetabular cup during primary THA depends largely on the amount of bone stock left after acetabular reaming. Eccentric or excessive acetabular reaming can cause soft tissue impingement, loosening, altered center of rotation, bone-to-bone impingement, intraoperative periprosthetic fracture, and other complications. Furthermore, loss of bone stock during primary THA may adversely affect subsequent revision THA.

Questions/Purposes

We sought to compare the conventional THA (CTHA) approach to robotic-guided THA (RGTHA) to determine which of these techniques preserves more acetabular bone, as interpreted from the size of the acetabular component compared with the size of the native femoral head.

Foreword

Silver coatings, used in many surgical devices, have demonstrated good antimicrobial activity and low toxicity. Oncological musculoskeletal surgery have an high risk of infection, so in the last decades, silver coated mega-prostheses have been introduced and are becoming increasingly widespread.

Material and methods

We performed a retrospective analysis of 158 cases of bone tumors, primary or metastatic, treated between 2002–2014 with wide margins resection and reconstruction with tumoral implants. The average age was 59 years (range 11–78 years), all patients were treated by the same surgeon, with antibiotic prophylaxis according to a standard protocol. In 58.5% of patients were implanted silver-coated prostheses, in the remaining part, standard tumor prosthesis. Patients were re-evaluated annually and were recorded complications, with particular attention to infectious diseases.

Objective

The purpose of this study was to investigate how rim poly locking scallop cutting depth could affect the rigidity of acetabular cup.

Materials and Methods

(11) generic FEA models including (5) 50mm OD Ti6Al4VELI hemispherical acetabular shells with thicknesses of 3.0, 3.5, 4.0, 4.5 and 5.0mm, and (6) 4mm thick hemispherical shells with standard rim poly indexing scallops varied in cutting depths from inner diameter of the cup in 1.0, 1.5, 2.0, 2.5, 3.0 and 3.5mm. All cups were analyzed in ANSYS® Workbench™ FEA software with a loading condition of 2000N applied to the cup rim per V15 ISO/TC 150/SC 4 N. Verification was carried out by the physical test of a same generic Ti6Al4VELI 50mmOD and 5mm thick solid hemispherical shell under 2000N rim directed load. The cup deformation was compared with FEA results. The maximum deformation of FEA scalloped cups were compared with that of solid hemispherical cups with different shell thickness.

Introduction

Mechanical properties of irradiated Ultra High Molecular Weight Polyethylene (UHMWPE) after aging have been well documented. However there was no sufficient data for the dimensional change due to irradiation and aging. This change may have adverse effects to the implant modular locking mechanism. The purpose of this study was to characterize the dimensional change of UHMWPE after irradiation and aging.

Materials and Method

Total (30) ø15mm × 50mm virgin GUR 1050 UHMWPE rods were cleaned, dried, inspected, vacuum packaged and stored in 20°C environment for 2 days. Among them, (20) samples were measured along the 50mm length at 20°C +/-2°C before and after two conditions: 1, (10) were submerged in 40°C DI water for 2 hours and dried in 40°C to simulate the cleaning process and 2, (10) were soaked in 37°C saline for 14 days to simulate initial in-vivo environment. Remaining (10) samples were measured in the same way after irradiation of 30KGy dosage and then measured again after soaking in 37°C saline for 14 days to simulate the actual radiation sterilization and in-vivo soaking conditions. Same samples were measured once more after accelerated aging per ASTM-1980-07 for 80 days to simulate the 3 year in vivo life. The differences in measurements between virgin and end conditions were documented as the percentage dimensional change. After the measurements, in the groups of DI water, saline soaking and radiation + aging, (3) samples were randomly selected for DSC measurements. The results were compared with dimensional measurements. Statistical analysis was performed by the student t test to compare virgin condition and the conditions after each treatment. 95% significance level was assumed.

Introduction

The use of reverse total shoulder arthroplasty (RSA) is becoming increasingly common in the treatment of rotator cuff arthropathy. Standard RSA technique involves medialising the centre of rotation (COR) maximising the deltoid lever arm and compensating for rotator cuff deficiency. However reported complications include scapular notching, prosthetic loosening and loss of shoulder contour. As a result the use of Bony Increased Offset Reverse Shoulder Arthroplasty (BIO-RSA) has been gaining in popularity. The BIO-RSA is reported to avoid these complications by lateralising the COR using a modified base plate, longer central post and augmentation with cancellous bone graft harvested from the patients humeral head.

Objectives

This study aims to compare the outcome in terms of analgesic effect, function and satisfaction, in patients treated with standard RSA and BIO-RSA.

Introduction

The use of reverse total shoulder arthroplasty (RSA) is becoming increasingly common in the treatment of rotator cuff arthropathy. In recent years indications for use have expanded to include elderly patients in whom either internal fixation is not possible due to fracture configuration, poor bone quality, or presence of a rotator cuff deficiency. There is however relatively little evidence to support its use in these circumstances.

Objective

This study aims to assess the viability of RSA as a salvage procedure in the treatment of complex proximal humeral fractures or irreducible dislocations, quantified in terms of functional outcome, complication rates and patient reported satisfaction.

Introduction

Total hip arthroplasty has seen a transition from cemented acetabular components to press-fit porous coated components. Plasma sprayed titanium implants are often press-fit with 1mm under-reaming of the acetabulum; however, as porous coating technologies evolve, the amount of under-reaming required for initial stability may be reduced. This reduction may improve implant seating due to lowered insertion loads, and reduce the risk of intraoperative fracture. The purpose of this study was to investigate the initial fixation provided by a high porosity coating (P2, DJO Surgical), and a plasma sprayed titanium coating under rim loading with line-to-line and 1mm press-fit surgical preparation.

Methods

Five, 52mm high porosity acetabular cups (60% average porosity) and five 52mm plasma sprayed titanium coated cups were inserted into low density (0.24g/cc) biomechanical test foam (Pacific Research Laboratories). Foam test material was cut into uniform 90×90×40mm blocks. Reaming was performed using standard instrumentation mounted on a vertical mill. Cups were first inserted into foam blocks prepared with line-to-line (52mm) reaming. Following mechanical testing, cups were removed from the foam, cleaned, and inserted into foam blocks prepared with 1mm under reaming (51mm). In total 4 test conditions were evaluated:

Group A: P2 + line-to-line

Acetabular cup impaction was carried out using a single axis servohydraulic test machine (Instron 8500). Cups were inserted at 1mm/s to a load of 5kN. Insertion load was calculated as a 0.1mm offset from the linear portion of the force/displacement curve; insertion energy was the area under the curve.

Tangential rim loading was applied at 0.0254mm/s by a conical indenter to the implant rim. Load data were recorded at 1kHz. Cup displacement was recorded by a 3D, marker-based tracking system at 15Hz (DMAS, Spicatek). Six markers were attached to a disk secured in the acetabular cup (Figure 1). Yield failure was defined as 0.331o of angular displacement (150µm of relative displacement). Angular displacement was derived by calculating the normal vector of a best-fit plane based on marker centroids.

Purpose

It is well known that meniscus extrusion is associated with structural progression of knee OA. However, it is unknown whether medial meniscus extrusion promotes cartilage loss in specific femorotibial subregions, or whether it is associated with a increase in cartilage thickness loss throughout the entire femorotibial compartment. We applied quantitative MRI-based measurements of subregional cartilage thickness (change) and meniscus position, to address the above question in knees with and without radiographic joint space narrowing (JSN).

Methods

60 participants with unilateral medial OARSI JSN grade 1–3, and contralateral knee OARSI JSN grade 0 were drawn from the Osteoarthritis Initiative. Manual segmentation of the medial tibial and weight-bearing medial femoral cartilage was performed, using baseline and 1-year follow-up sagittal double echo steady-state (DESS) MRI, and proprietary software (Chondrometrics GmbH, Ainring, Germany). Segmentation of the entire medial meniscus was performed with the same software, using baseline coronal DESS images. Longitudinal cartilage loss was computed for 5 tibial (central, external, internal, anterior, posterior) and 3 femoral (central, external, internal) subregions. Meniscus position was determined as the % area of the entire meniscus extruding the tibial plateau medially and the distance between the external meniscus border and the tibial cartilage in an image located 4mm posterior to the central image (a location commonly used for semi-quantitative meniscus scoring). The relationship between meniscus position and cartilage loss was assessed using Pearson (r) correlation coefficients, for knees with JSN and without JSN.

Purpose

The study aim was to assess how the periprosthetic bone density of the MiniHip™ changed in the course of the first year. Is there a correlation between the decrease in bone density with CCD angle or stem size? Are there other variables influencing the changes in bone density?

Material and Methods

62 patients aged 25–78 years (34 women, 28 men) were implanted with a MiniHip total hip replacement during 2011 and 2012 through an anterolateral minimally invasive (ALMI) approach. Pre-operative diagnosis was osteoarthritis in 49 patients, dysplasia in 7, femoral necrosis in 4 and femoral neck fracture in 2 cases. As a primary variable the periprosthetic bone mineral density (BMD) was measured postoperatively within the first 2 weeks as a baseline measurement. Follow-up measurements were performed at 3, 6 and 12 months postoperatively. Statistical analysis was conducted to show any differences.

Introduction

Implant position plays a major role in the mechanical stability of a total hip replacement. The standard modality for assessing hip component position postoperatively is a 2D anteroposterior radiograph, due to low radiation dose and low cost. Recently, the EOS® X-Ray Imaging Acquisition System has been developed as a new low-dose radiation system for measuring hip component position. EOS imaging can calculate 3D patient information from simultaneous frontal and lateral 2D radiographs of a standing patient without stitching or vertical distortion, and has been shown to be more reliable than conventional radiographs for measuring hip angles[1]. The purpose of this prospective study was to compare EOS imaging to computer tomography (CT) scans, which are the gold standard, to assess the reproducibility of hip angles.

Materials and Methods

Twenty patients undergoing unilateral THA consented to this IRB-approved analysis of post-operative THA cup alignment. Standing EOS imaging and supine CT scans were taken of the same patients 6 weeks post-operatively. Postoperative cup alignment and femoral anteversion were measured from EOS radiographs using sterEOS® software. CT images of the pelvis and femur were segmented using MIMICS software (Materialise, Leuven, Belgium), and component position was measured using Geomagic Studio (Morrisville, NC, USA) and PTC Creo Parametric (Needham, MA). The Anterior Pelvic Plane (APP), which is defined by the two anterior superior iliac spines and the pubic symphysis, was used as an anatomic reference for acetabular inclination and anteversion. The most posterior part of the femoral condyles was used as an anatomic reference for femoral anteversion. Two blinded observers measured hip angles using sterEOS® software. Reproducibility was analysed by the Bland-Altman method, and interobserver reliability was calculated using the Cronbach's alpha (∝) coefficient of reliability.

Introduction

Polyethylene (PE) wear is clearly linked to total hip arthroplasty (THA) failure, leading to osteolysis and decreasing survivorship rates. Dual mobility cups (DMC) are widely used to prevent or treat THA instability. However some studies have pointed PE wear risk as a “dual wear” risk. Hip wear simulation is usually used to understand factors influencing wear and to differentiate design, PE types and materials performances. To date, few works have been published studying dual mobility insert wear.

Objectives

Our objective was to evaluate wear of DMC with comparison with a fixed single articulating hip design and to measure wear under same conditions (loading cycle, temperature, sterilization, material and surface roughness).

INTRODUCTION

Total Knee Arthroplasty (TKA) survival is directly dependent on precise component placement. As showed by Mason meta-analysis in 2007, only 68.2% of TKAs achieved axis less than 3° with conventional methods versus 91% with Computer Assisted Surgery (CAS). However, if CAS seems to have more accuracy its use is in less than 10% procedures in United States because of its cost, operative time and need of extra pin sites. Smart technology, providing no requirement or arrays for registration, no need of pre operative images and lest cost effective seems to be an encouraging way.

OJBECTIVES

We report our experience of a new system that is an accelerometer-based portable navigation with a disposable display console and reference sensor; gyrometer is like smartphone ones. This system permits to realize femoral distal cut, and tibial proximal cut, adjusting varus-valgus, flexion-extension and tibial slope regardless implants used. Goal of the study was to determine accuracy and reliability of the system.

Background

Several studies have shown that Staphylococcus aureus (S.aureus) nasal colonization is associated with postoperative surgical site infection and that preoperative decolonization can reduce infection rates. Up to 30% of joint replacement patients have positive S.aureus nasal swabs and patient risk factors for colonization remain largely unknown. Many joint replacement patients continue to undergo surgery without being screened.

Study Question

Is there a specific patient population at increased risk of S.aureus nasal colonization?

Introduction

Realistic in-vivo loads on knee implants from telemetric analyses were recently published. Impacting an implant, especially a ceramic one, will produce high peak stresses within the component. Data for loads occurring during implantation of a knee implant are scarce. To ensure a safe impaction of ceramic tibial trays the stresses caused by it need to be known.

Materials and Methods

Impaction testing including force measurements (using Kistler piezo load cell 9351B) was performed on a ceramic tibial tray. The same test was simulated by computational analysis using FEM (Finite-Element-Method). Because the forces measured and those calculated by FEM were significantly different, an in vitro impaction study was performed to obtain realistic loads for a ceramic tibial tray. A surgeon was asked to perform heavy hammer blows which may occur during implantation. Using a high speed camera (phantom V7.2) the velocity of the hammer at the time of impaction was determined. Using this parameter instrumented ceramic tibial trays (BPK-S Knee, P. Brehm) were implanted into a biomechanical Sawbones® model. Linear strain gauges were attached to the four fins of the tibial tray as these are the regions of highest stresses. Simulating the surgeon's highest impacts measurements were conducted at a frequency of 1 MHz. The identical hammer was used in this in vitro study and the velocity of the hammer was measured by using the same high speed camera. To investigate the damping effect of bone cement Palacos®R bone cement was used. Only worst-case impacts within the range achieved by the surgeon were applied to evaluate the stress distribution within the ceramic tibial tray.

INTRODUCTION

Early postoperative strength loss is pronounced following total knee arthroplasty (TKA) and is largely the result of reduced muscular activation. High-intensity progressive rehabilitation may limit postoperative weakness and improve long-term outcomes, but no randomized controlled trials have examined its use after TKA. The purpose of this trial was to examine the efficacy of a high-intensity progressive rehabilitation protocol (HI) compared to a lower intensity (LI) rehabilitation protocol after TKA.

METHODS

One hundred and sixty-two subjects (aged 63±7 years, 89 females) were randomized to either the HI group or LI groups after TKA. The HI intervention consisted of an early initiation of intensive rehabilitation using progressive resistance exercise. The LI intervention was based on a synthesis of previously published standard TKA rehabilitation programs. Both groups were treated 2–3 times per week for 12 weeks. Outcomes included the stair climbing test, timed-up-and-go test, five-times sit-to-stand test, 6-minute walk test, isometric quadriceps and hamstring strength, quadriceps activation, surgical knee range of motion, and WOMAC. Secondary analysis evaluated whether outcomes differed depending on post-operative quadriceps activation. Outcomes were assessed preoperatively and at 1, 2, 3, 6, and 12 months postoperatively.

Introduction

Pain related to knee osteoarthritis (OA) is a complex phenomenon that cannot be fully explained by radiographic disease severity. We hypothesized that pain phenotypes are likely to be derived from a confluence of factors across multiple domains: knee OA pathology, psychology, and neurophysiological pain processing. The purpose of this study was to identify distinct phenotypes of knee OA, using measures from the proposed domains.

Methods

Data from 3494 subjects participating in the Osteoarthritis Initiative (OAI) study was analyzed. Variables analyzed included: radiographic OA severity (Kellgren-Lawrence grade), isometric quadriceps strength, Body Mass Index (BMI), comorbidities, CES-D Depression subscale score, Coping Strategies Questionnaire Catastrophizing subscale score, number of pain sites, and knee tenderness on physical examination. Variables used for comparison across classes included pain severity, WOMAC disability score, sex and age. Latent Class Analysis was performed. Model solutions were evaluated using the Bayesian Information Criterion. One-way ANOVAs and post hoc least significance difference tests were used for comparison of classes.

Introduction

Trial reduction while performing total hip replacement is an essential step of the procedure. This is to check the stability of the hip joint with the selected implant sizes and to assess the leg length to avoid discrepancy.

Disengagement of the femoral head trial from the femoral rasp stem, with subsequent migration of the trial head into the pelvic cavity is a rare occurrence, but can be a very frustrating complication to both the surgeon and occasionally the patient.

We present our experience with this exceptional situation and different management options, together with systematic review of the literature.

Patients and methods

We conducted Medline database search via Pubmed interface. MeSH search was used. Systematic review of English literature case reports was performed.

15 reports were found discussing intra-pelvic migration of different arthroplsty related materials.

The total number of reported cases was 24 cases, out of those, 21 cases were related to migration of femoral trial head, 2 cases of migrated modular hemiarthroplasty bipolar heads and one case of migrated femoral head definitive implant.

Aim

The aim of this study is to outline the steps and techniques required to create a patient specific 3D printed guide for the accurate placement of the origin of the femoral tunnel for single bundle ACL reconstruction.

Introduction

Placements of the femoral tunnels for ACL reconstruction have changed over the years 1,2. Most recently there has been a trend towards placing the tunnels in a more anatomic position. There has been subsequent debate as to where this anatomic position should be 3. The problem with any attempt at consensus over the placement of an anatomic landmark is that each patient has some variation in their positioning and therefore a fixed point for all has compromise for all, as it is an average 4. Our aim was to attempt to make a cost effective and quick custom guide that could allow placement of the center of the patients’ newly created femoral tunnel in the mid position of their contralateral native ACL femoral footprint.

Introduction

Modularity in total hip arthroplasty offers many potential benefits, however the consequences of mechanically associated corrosion continue to be concerning. Micromotion and settling of the modular components at the taper interface are thought to contribute to the etiology of this problem. The purpose of this study was to investigate the effect of hammer blows delivered in different directions on the force transmitted to the head-neck and neck-stem interface in modular hip implants.

Methods

One-hundred and forty-four impact tests were performed in six different directions: one on axis and five 10° off axis. Four different simulations were performed measuring the head-neck only and three different necks: 0°, 8°, and 15°. A constant height delivered on-axis hammer blows at a constant 4,500 Newton (N). Load cells positioned in the hammer and at the neck-stem junction transmitted voltage to an oscilloscope which measured forces.

Introduction

Total knee arthroplasty (TKA) is the definitive treatment for osteoarthritis of the knee. The primary goal of the operation is to minimize or eliminate pain associated with osteoarthritis and secondarily to regain functional mobility and stability around the knee joint in order improve overall quality of life. The vast majority of techniques utilized for this procedure involves removal of the anterior cruciate ligament (ACL). In a native knee the ACL is a primary stabilizing ligament and essential for providing proprioceptive feedback. In the absence of the ACL, the kinematics of the knee are compromised. In an effort to more accurately replicate normal knee stability, new implant designs have emerged which maintain an intact ACL. Described herein is a cadaveric study looking at ACL competency after implantation of a TKA in which the cruciate ligaments are preserved.

Methods

Twenty fresh, frozen cadaveric knees were utilized in which the ACL was intact. Specimens were excluded if there was concern for ACL stability as determined by physical examination, direct visualization during the arthrotomy and a KT-1000 measurement of anterior tibial translation in millimeters at 67N and 89N of anterior force. Each KT-1000 measurement was repeated three times using three individual examiners at both force values for a total of six data points. Bicruciate retaining components were implanted into each knee using a medial parapatellar approach. After adequate sagittal and coronal balancing was obtained, the knee was reexamined using the KT-1000 protocol described above to assess for any changes in ACL competency. The ACL was then transected and the knee was examined for a third time with the same KT-1000 protocol. For statistical analysis, a 2-way repeated-measures ANOVA was utilized. Pairwise differences were assessed utilizing Fisher's least significant difference method.

Introduction

The use of metal-on-metal (MOM) and modular total hip arthroplasty (THA) is associated with potentially serious complications including elevated serum metal ion levels, pseudotumor, cardiomyopathy and neurologic abnormalities. The primary aim of this analysis was to identify any associations between the presence of pseudotumor, serum metal ion levels, and specific dual modular implant components.

Methods

We evaluated prospectively collected data from 49 patients, mean age 58.4 years, who underwent implantation of modular THA from 01/2004-01/2010. The collected data spanned a 5–11 year period from the time of index procedure. Serum metal ion levels, including titanium, cobalt and chromium, were collected in 2012 and 2015. Hip ultrasounds were performed on each patient by a trained musculoskeletal radiologist for evaluation of the presence of soft-tissue pseudotumor. Univariate nonparametric tests were used to compare the two groups: Fisher's exact tests for categorical variables, and Wilcoxon two-group tests for continuous variables. For the purposes of analysis, values that were below the level of detection (LOD) were set to half the LOD. All analyses were performed using SAS 9.4 (SAS Institute Inc, Cary, NC, USA). Statistical significance is set at p<0.05.

Object

CT-based navigation system in total hip arthroplasty(THA) is widely used to achieve accurate implant placement. However, its internal structure was a trade secret. Therefore, it was hard to analyze optimal reference points. Now, we developed our own CT-based navigation system originally, and since then we have been conducting various analyses in order to use the system more effectively. The purpose of this study was to analyze the optimal area and the number of registration points, which enables to move initial errors into the acceptable range.

Methods

We set the anterior pelvic plane(APP) as the reference plane, and defined the coordinates as follows: X-axis for external direction, Y-axis for anterior direction, and Z-axis for proximal direction. We made pelvic bone models after THA, a normal shape and acetabular dysplasia model, and performed registration using an originally developed CT based navigation system. At first, we registered point paired matching at 4 points, and surface matching was performed at 53 points, which were placed around the acetabulum. 20 points were on anterosuperior, 10 points were on posterosuperior, 20 points were on posterior around the acetabulum, and 3 points were on the pubis. We selected surface matching points based on the actual operation approach, calculated the accuracy of the error correction, and searched the optimal area and the number of surface matching points.

Materials and Methods

We treated 60 hips in 60 patients (8 males and 52 females) with cementless THA that were performed from January 2007 to December 2009 in our hospital. 48 osteoarthritis hips, 5 rheumatoid arthritis hips and 7 idiopathic osteonecrosis hips were included. All patients were performed THA with VectorVision Hip navigation system (BrainLAB, Feldkirchen, Germany). We used AMS HA cups and PerFix stems (KYOCERA Medical co., Osaka, Japan). The mean age of surgery was 61 years old (35–79 years old). The pelvic inclination angles (PIA) were measured with anteroposterior radiographic image in accordance with the Doiguchi's method.

Results

The amount of change of the pelvic inclination angle between supine and standing position was 0.6 degrees prior to surgery, 0.7 degree at 1 year after surgery and 2.4 degrees at 5 years after surgery. 7 patients prior to surgery, 7 patient at 1 year after surgery and 18 patient at 5 year after surgery changed more than 5 degrees between supine and standing position. The pelvic inclination angles of 23 patients prior to surgery, 19 patients at 1 year after surgery and 35 patients at 5 years after surgery changed in the retroverted direction with posture change. It tended to increase after surgery.

Introduction

The use of antibiotic-loaded polymethylmethacrylate bone-cement spacers during two-stage exchange procedures is the standard in the treatment of patients with delayed prosthetic joint infection. The real antimicrobial activity of these spacers is unclear because the adherence of bacteria to cement might result in clinical recurrence of infection. The purpose of the study is to evaluate the in vitro formation of Pseudomonas Aeruginosa (PA) and Staphylococcus spp. biofilm on antibiotic-loaded bone cement.

Materials and methods

Cement disks (diameter = 6 mm) impregnated with gentamicin and colistin were submerged in bacterial suspensions of Methicillin-resistant Staphylococcus Aureus(MRSA), Staphylococcus epidermidis (SE), and PA. Negative controls (specimen disks without antibiotic) were similarly prepared. Biofilm formation was visualized by confocal scanning laser microscopy (CSLM), after staining the discs with the live/dead BacLight viability stain containing SYTO 9 dye and propidium iodide. Images from five randomly selected areas were acquired for each disc. Sequential optical sections of 2 µm were collected in sequence along the z-axis over the complete thickness of the sample. The resulting stacks of images were analyzed, quantified and rendered into three-dimensional (3D). The biofilm thickness on antibiotic bone cement compared with the controls was automatically evaluated.

Materials and Methods

433 hips implanted in patients over 75 years old were identified from our Local Joint Registry. Group A consisted of 139 tapered cemented hips, group B of 140 tapered grit-blasted uncemented hips and group C of 154 tapered porous-coated uncemented hips. A 28 mm femoral head size on polyethylene was used in all cases. The mean age was greater in group A and the physical activity level according to Devane was lower in this group (p<0.001 for both variables). Primary osteoarthritis was the most frequent diagnoses in all groups. The radiological acetabular shape was similar according to Dorr, however, an osteopenic-cylindrical femur was most frequently observed in group A (p<0.001). The pre- and post-operative clinical results were evaluated according to the Merle-D'Aubigne and Postel scale. Radiological cup position was assessed, including hip rotation centre distance according to Ranawat and cup anteversion according to Widmer. We also evaluated the lever arm and height of the greater trochanter distances and the stem position. Kaplan-Meier analysis was done for revision for any cause and loosening.

Results

The hip rotation centre distance was greater and the height of the greater trochanter was lower in group B (p=0.003, p<0.001, respectively). The lever arm distance was lower in group C (p<0.001). A varus stem position was more frequently observed in group B (p<0.001). There were no intra- or post-operative fractures in group A, although there were five intra-operative fractures in the other groups plus two post-operative fractures in group B and four in group C. The rate of dislocation was similar among groups and was the most frequent cause for revision surgery (8 hips for the whole series). The mean post-operative clinical score improved in all groups. The overall survival rate for revision for any cause at 120 months was 88.4% (95% CI 78.8–98), being 97.8% (95% CI 95.2–100) for group A, 81.8% (95% CI 64.8–98.8) for group B and 95.3% (95% CI 91.1–99.6) for group C (log Rank: 0.416). Five hips were revised for loosening. The overall survival rate for loosening at 120 months was 91.9% (95% CI 81.7–100), being 99.2%(95% CI 97.6–100) for group A, 85.5 (95% CI 69.9 −100) for group B and 100% for group C (Log Rank 0.093).

Introduction

Alumina-on-alumina in total hip replacement has been used for avoiding osteolysis and loosening. Published series report no ceramic wear and low rates for fractures and noises, but report poor results because of acetabular fixation failure. From 1999 to 2005, we used the “first generation” of a cementless cup, tri-radius relatively-smoothed HA coated (group 1), and from 2006 we have used a “second-generation” of this same cementless cup design with a macrotextured surface (group 2). We compare the perioperative conditions of two groups of patients using these two different cups and the clinical and radiological results.

Material and Methods

We analysed 679 (612 patients) consecutive and non-selected primary cementless alumina-on-alumina prostheses. There were 342 hips in group 1 and 337 in group 2. The stem used for all patients in this series was the same and fitted with an Al2O3 liner and femoral head. The use of screws were according to the intraoperative stability of the cup (pull-out test). Patients’ mean age was 48.7+13.6 years and the average follow-up until revision or the last evaluation was 11.7 years for group 1 and 5.4 years for group 2.

Background and aim

Recent proposals have been introduced to modify stem design and/or femoral fixation in total hip replacement (THR). New designs need to consider previous design features and their results. The aim of this study has been to evaluate the clinical and radiological results of six different designs of tapered uncemented stems implanted in our Institution.

Methods

1918 uncemented hips were prospectively assessed from 1999 to 2011 (minimum follow-up of five years for the unrevised hips). All hips had a 28 or 32 mm femoral head and metal-on-polyethylene or alumina-on-alumina bearing surface. Six uncemented femoral designs that shared a femoral tapered stem incorporating a coating surface were included in the study. The different design features included the type of coating, metaphyseal filling, and sectional shape.

Introduction

The use of screws is frequent for additional fixation, however, since some disadvantages have been reported a cup press-fit is desirable, although this can not always be obtained. Cup primary intraoperative fixation in uncemented total hip replacement (THR) depends on sex, acetabular shape, and surgical technique. We analyzed different factors related to primary bone fixation of five different designs in patients only diagnosed with osteoarthritis, excluding severe congenital hip disease and inflammatory arthritis, and their clinical and radiological outcome.

Materials y Methods

791 hips operated in our Institution between 2002 and 2012 were included for the analysis. All cases were operated with the same press-fit technique, and screws were used according to the pull-out test. Two screws were used if there was any movement after the mentioned manoeuvres. Acetabular and femoral radiological shapes were classified according to Dorr et al. We analyzed radiological postoperative cup position for acetabular abduction angle, the horizontal distance and the vertical distance. Cup anteversion was evaluated according to Widmer and the hip rotation centre according to Ranawat.

Introduction

The optimal management of severe tibial and/or femoral bone loss in a revision total knee arthroplasty (TKA) has not been established. Reconstructive methods include structural or bulk allografts, impaction bone-grafting with or without mesh augmentation, custum prosthetic components, modular metal augmentations of prosthesis and tumor prosthesis. Recently metaphyseal fixation using porous tantalum cones (Zimmer, Warsaw, IN) has been proposed as alternative strategy for severe bone loss.

Objectives

The purposes of this study were to determine the clinical and radiographic outcomes in patients who underwent revision knee arthroplasty with tantalum cones with a minimum of 5-year follow-up.