Introduction and aim

TKR remains one of the most successful surgeries in orthopedics. Still a sizeable number of patients remain dissatisfied reaching to a level of 30%. Our aim was to examine the excised synovium from the suprapatellar region in all osteoarthritic knees and evaluate the histopathological report to know if in a few cases the unrelenting pain and discomfort could be due to some undiagnosed pathology within the joint.

Materials and Methods

We selected 40 consecutive knees at our institution operated from Oct 2014 to Jan 2015. Of the total knees 7 patients were operated as single stage bilateral TKR. Supra patellar synovium was thoroughly excised and sent for histopathology examination. Patients who were clinically, serologically and radiologically diagnosed as rheumatoid arthritis or sero negative arthritis were excluded. The implant used was Maxx Freedom knee (PS design).

Introduction

Cruciate retaining knee replacements are only implanted into patients with “healthy” ligaments. However, partial anterior cruciate ligament (ACL) tears are difficult to diagnose with conventional MRI. Variations of signal intensity within the ligament are suggestive of injury but it is not possible to confirm damage or assess the collagen alignment within the ligaments. The potential use of Magic Angle Directional Imaging (MADI) as a collagen contrast mechanism is not new, but has remained a challenge. In theory, ligament tearing or joint degeneration would decrease tissue anisotropy and reduce the magic angle effect. Spontaneous cruciate ligament rupture is relatively common in dogs. This study presents results from ten canine knees.

Methods

Ethical approval was obtained to collect knees from euthanized dogs requiring a postmortem (PM). A Siemens Verio 3T MRI scanner was used to scan a sphere containing the canine knees in 9 directions to the main magnetic field (B₀) with an isotropic 3D-T1-FLASH sequence. After imaging, the knees were dissected and photographed. The images were registered and aligned to compare signal intensity variations. Segmentation using a thresholding technique identified voxels containing collagen. For each collagen-rich voxel the orientation vector was computed using Szeverenyi and Bydder's method. Each orientation vector reflects the net effect of all fibers comprised within a voxel. The assembly of all unit vectors represents the fiber orientation map and was visualised in ParaView using streamlines. The Alignment Index (AI) is defined as a ratio of the fraction of orientations within 20° (solid angle) centred in that direction to the same fraction in a random (flat) case. By computing AI for a regular gridded orientation space we can visualise differences in AI on a hemisphere. AI was normalised so that AI=0 indicates isotropic collagen alignment. Increasing AI values indicate increasingly aligned structures: AI=1 indicates that all collagen fibers are orientated within the cone of 20° centred at the selected direction.

Introduction

Although weight-bearing CT of the foot definitely reflects the morphology and deformity of joint, it is hard to obtain the standing CT due to difficulty of availability. Although 3D imaging reconstruction using radiographs has been reported in other joints, there is no study about foot joint. The purpose of this study is to develop a semi-automatic method based on a deformable surface fitting for achieving the weight-bearing 3D model reconstruction from standing radiographs for foot.

Methods

Our method is based on a Laplacian surface deformation framework using a template model of foot. As pre- processing step, we obtained template surface meshes having the average shapes of foot bones (talus, calcaneus) from standing CT images (Planmed Verity) in 10 normal volunteers. In the reconstruction step, the surface meshes are deformed following guided user inputs with geometric constraints to recover the target shapes of 30 patients while preserving average bone shape and smoothness. Finally, we compared reconstructed 3D model to original standing CT images. Analysis was performed using Dice coefficients, average shape distance, maximal shape distance.

Introduction

We have investigated the long-term (minimum follow-up period; 10 years) clinical results of the total hip arthroplasty (THA) using K-MAX HS-3 tapered stem.

Materials and Methods

In K-MAX HS-3 THA (Kyocera Medical, Kyoto, Japan), cemented titanium alloy stem and all polyethylene cemented socket are used. This stem has the double tapered symmetrical stem design, allowing the rotational stability and uniform stress distribution. The features of this stem are; 1. Vanadium-free high-strength titanium alloy (Ti-15Mo-5Zr-3Al), 2. Double-tapered design, 3. Smooth surface (Ra 0.4µm), 4. Broad proximal profile, 5. Small collar.

Previous type stem, which was made of the same smooth-surface titanium alloy, has the design with cylindrical stem tip, allowing the maximum filling of the femoral canal. Osteolysis at the distal end of the stem had been reported in a few cases in previous type with cylindrical stem tip, probably due to the local stress concentration. Therefore the tapered stem was designed, expecting better clinical results.

157 THAs using HS-3 taper type stem were performed at Kitano Hospital between March 2004 and March 2008. And 101 THAs, followed for more than 10 years, were investigated (follow-up rate; 64.3%). The average age of the patients followed at the operation was 61.7 years and the average follow-up period was 10.9 years. The all-polyethylene socket was fixed by bone cement, and the femoral head material was CoCr (22mm; 5 hips, 26 mm; 96 hips).

INTRODUCTION

The primary goal of THA or TKA is to relieve pain and restore mobility. The success is determined by the longevity of prostheses and early return to routine activities, such as driving. With enhanced recovery regimens, patients are being discharged within 24–48hrs post-op.. The aim of this study was to determine when our patients returned to driving after anterior hip replacements and patient specific knee replacements.

METHODOLOGY

This study included 207 soft tissue sparing anterior bikini THA and 146 patient specific instrumented (PSI) TKAs between Feb 2017 and March 2018. All patients included drove before surgery. Non-drivers were excluded. A detailed questionnaire was sent to all patients 3 to 6 weeks after surgery to record their driving status. 50 patients were randomly selected to assess flexion at the hip, knee, and ankle joints whilst seated in the driver's seat of their vehicle.

Introduction

Density-modulus relationships are often used to map the mechanical properties of bone based on CT- intensity in finite element models (FEMs). Although these relationships are thought to be site-specific, relationships developed for alternative anatomic locations are often used regardless of bone being modeled. Six relationships are commonly used in finite element studies of the shoulder; however, the accuracy of these relationships have yet to be compared. This study compares each of these six relationships ability to predict apparent strain energy density (SED_app) in trabecular bone cores from the glenoid.

Methods

Quantitative-CT (QCT) (0.625 mm isotropic voxels), and µ-CT scans (0.032 mm isotropic voxels) were obtained for fourteen cadaveric scapulae (7 male, 7 female). Micro finite element models (µ-FEMs) were created from 98 virtual ‘cores’ using direct conversion to hexahedral elements. Two µ-FEM cases were considered: homogeneous tissue modulus of 20 GPa, and heterogeneous tissue modulus scaled by CT intensity of the µ-CT images (196 models). Each µ- FEM model was compressively loaded to 0.5% apparent strain and apparent strain energy density (SED_app) was calculated. Additionally, each of the six density-modulus relationships were used to map heterogeneous material properties to co- registered QCT-derived models (588 models in total). The loading and boundary conditions were replicated in the QCT-FEMs and the SED_app was calculated and compared to the µ-FEM SED_app. To account for more samples than donors, restricted maximum likelihood estimation (REML) linear regression compared µ-FEM SED_app and QCT-FEM SED_app for each relationship.

Introduction

Trabecular bone transmits loads to the cortical shell and is therefore most active in bone remodeling. This remodeling alters trabecular material strength thereby changing the bending stiffness. Accounting for trabecular material heterogeneity has been shown to improve empirical-µFEM correlations by allowing for more realistic trabecular bending stiffness. In µFEMs to reduce computation time, region averaging is often used to scale image resolution. However, region averaging not only alters trabecular architecture, but inherently alters the CT-intensity of each trabeculae. The effect of CT-intensity variations on computationally derived apparent modulus (E_app) in heterogenous µFEMs has not been discussed. The objectives of this study were to compare trabecular E_app among i) hexahedral and tetrahedral µFEMs, ii) µFEMs generated from 32 µm, 64 µm, and 64 µm down-sampled from 32 µm µ-CT scans, and iii) µFEMs with homogeneous and heterogeneous tissue moduli.

Methods

Fourteen cadaveric scapulae (7 male; 7 female) were micro-CT scanned at two spatial resolutions (32 µm & 64 µm). Virtual bone cores were extracted from the glenoid vault, maintaining a 2:1 aspect ratio, to create µFEMs from the 32 µm, 64 µm, and down-sampled 64 µm scans. Custom code was used to generate µFEMs with 8-node hexahedral elements (HEX8), while maintaining the bone volume fraction (BV/TV) of each HEX8 32 µm model (BV/TV=0.24±0.10). Each virtual core was also generated as a 10-node tetrahedral (TET10) µFEM. All µFEMs were given either a homogeneous tissue modulus of 20 GPa, or a heterogeneous tissue modulus scaled by CT-intensity. All FEMs were constrained with identical boundary conditions and compressed to 0.5% apparent strain. The apparent modulus of each model was compared.

Introduction & aims

The magnitude and pattern of acceptable migration in clinically successful cementless stems is not well understood. Radiostereometric analysis (RSA) is a well-recognised method of assessing implant migration.

Previous studies have reported long term RSA results for cemented stems. The aim of this study was to assess the long-term migration characteristics of the Corail hydroxyapatite-coated cementless stem at 10 years using RSA.

Method

A prospective cohort of 30 patients undergoing primary total hip arthroplasty for primary hip osteoarthritis were enrolled into a study to characterise the migration behaviour of a cementless stem. Tantalum markers were attached to the stem and placed in the bone intraoperatively, allowing for RSA measurements to be taken in vivo. Previous 5-year results have been presented.

A total of 14 patients (total 15 hips, one bilateral) with mean age 82 years (range, 69–92 years) underwent repeat long-term RSA radiographs at minimum 10 years post op. The mean time to follow up was 13.9 years (range, 13.3–14.4 years). The RSA radiographs were analysed to assess for implant rotation and translation.

Aims

Spontaneous osteonecrosis of the knee (SONK) mainly affects the medial femoral condyle, would be a good indication for UKA. The primary aim of this study was to assess the clinical, functional and radiographic outcomes at middle to long-term follow-up, of a consecutive series of fifty UKA used for the treatment of SONK. The secondary aim was to assess the volume of necrotic bone and determine if this influenced the outcome.

Patients and Methods

We reviewed 50 knees who were treated for SONK. Patients included ten males and 38 females. The mean age was 73 years (range, 57 to 83 years). The mean height and body weight were, respectively 153 cm (141 ∼171 cm) and 57 kg (35 ∼75kg). All had been operated on using the Oxford mobile-bearing UKA (Zimmer-Biomet, Swindon, United Kingdom) with cement fixation. The mean follow-up period was 8.4 years (range, 4 to 15years). We measured the size (width, length and depth) and the volume to be estimated (width x length x depth) of the necrotic bone mass using MRI in T1-weighted images.

The clinical results were evaluated using the Knee Society Scoring System (KSS) and Oxford Knee Score (OKS). The flexion angle of the knee was evaluated using lateral X-ray images in maximum flexion.

Materials and Methods

This study included with 50 knees of the 43 patients (6 males, 37 females) who had undergone TKA with ADLER GENUS system from March 2015 to January 2017. The mean age was 71.1±8.1 years. All patients were diagnosed with medial osteoarthritis of the knee. All implants was cruciate substituted type (CS type) and mobile bearing insert.

We developed a new ligament balancer that could be fixed to the tibia with keel and insert trial could be rotated on the paddle. We measured the medial and lateral soft tissue balance during TKA with the new balancer. The A-P position of the balancer was fixed on tibia in parallel with the Akagi line (A-P axis 0 group) and 20 degrees internal rotation (IR group) and 20 degrees external rotation (ER group). Soft tissue balance was measured in extension and 90 degrees of knee flexion on each rotational position.

Results

The mean angle of valgus and varus in IR group, 0 group and ER group were 4.6±2.2 degrees varus, 1.9±1.6 degrees varus and 0.4±2.4 degrees varus respectively in extension, and 5.5±3.0 degrees varus, 2.1±2.2 degrees varus and 0.7±3.2 degrees varus respectively in 90 degrees of knee flexion. There were significant differences between three groups in extension (p<0.0001) and flexion (p<0.0001). In other words, when the balancer was fixed on tibia with internal rotation against the Akagi line, the soft tissue balance indicated medial tightness. Conversely, when the balancer was fixed on tibia with external rotation against the Akagi line, the soft tissue balance showed lateral tightness.

The insert trial significantly rotated to opposite side against the position of balancer fixed.

Introduction

Soft tissue artefact (STA) affects the kinematics retrieved with skin marker-based motion capture, and thus influences the outcomes of biomechanical models that rely on such kinematics. To date, compensation for STA remains an unsolved challenge due to its complexity. Factors include its dependency on subject, on motion activity and on skin-marker configuration, its non-linearity over the movement cycle, and the scarcity of reference in-vivo estimations. The objective of this study was extending the existing knowledge of the effects of STA on the kinematics of the hip joint and on the hip joint center location, by quantifying them for a sample total hip arthroplasty (THA) population, for a broader range of activities of daily living (ADLs).

Methods

Four activities of daily living (overground gait, stairs descent, chair rise and putting on socks) were measured simultaneously with optical motion capture (MC) at 100 Hz and with a movable single-plane video-fluoroscopy system (VF) at 25 Hz, for fifteen patients with successful total hip arthroplasty (THA). The joint segment positions were computed by least-square fitting for MC and by semi-automatic 2D/3D registration for VF. Anatomical coordinate systems were defined for each joint segment based on skin markers location at a reference standing position. Errors induced by STA on the retrieved joint motion were computed as the difference between MC-based kinematics and the reference VF-based kinematics. Statistical analysis was carried out to determine the whether the differences between the kinematics obtained with the two methods were significant.

Background

Distal femoral replacements (DFR) are used in children for limb-salvage procedures after bone tumor surgery. These are typically modular devices involving a hinged knee axle that has peripheral metal-on-polyethylene (MoP) and central metal-on-metal (M-M) articulations. While modular connections and M-M surfaces in hip devices have been extensively studied, little is known about long-term wear or corrosion mechanisms of DFRs. Retrieved axles were examined to identify common features and patterns of surface damage, wear and corrosion.

Methods

The cobalt chromium alloy axle components from 13 retrieved DFRs were cleaned and examined by eye and with a stereo microscope up to 1000× magnification. Each axle was marked into 6 zones for visual inspection: the proximal and distal views, and the middle (M-M) and 2 peripheral (MoP) zones. The approximate percentage of the following features were recorded per zone: polishing, abrasion or scratching, gouges or detectable wear, impingement wear (i.e. from non- intentional articulation), discoloration and pitting.

Introduction

There is current debate concerning the most biomechanically advantageous knee implant systems, and there is also currently great interest in improving patient satisfaction after knee arthroplasty. Additionally, there is no consensus whether a posterior-stabilized (PS) total knee device is superior to a more congruent, cruciate-substituting, medially-stabilized device (MS). This study compared the clinical outcomes of two such devices. The primary hypothesis was that the clinical outcomes, and specifically the patient satisfaction as measured by the Forgotten Joint Score, would be better in the MS group.

Methods

This prospective, randomized, blinded Level 1 study compared the outcomes of 100 patients who received a Medacta GMK PS device and 101 patients who received a Medacta GMK medially-stabilized Sphere device (Medacta Intl., Lugano, Switzerland). All patients undergoing elective primary total knee arthroplasty were eligible for participation. Institutional Review Board approval and informed consent from participants were obtained. The devices were implanted using an anatomic alignment/calipered- measured resection surgical approach. Clinical and radiographic assessments were performed preoperatively, 6 weeks, 6 months, and annually. Data were compared using T-test with a significance level of 0.05.

Background

Kohnodai Hospital merged with the National Center of Neurology and Psychiatry in Japan in 1987. Accordingly, we treat more patients with mental disorders than other hospitals. I treated two patients with schizophrenia for TKA.

Case 1

A 44 year-old female with schizophrenia and malignant rheumatoid arthritis presented with bilateral knee pain and difficulty walking. Her range of motion (ROM) was: right knee; extension −95°, flexion 120°, left knee; extension −95°, flexion 120°. Her Knee Society Bilateral Score was 19 points, X-ray grade: Larsen 5, Steinbrocker grade: Stage 3, class 4. Pre-TKA, corrective casts improved her ROM (extension; right −75°, left −70°). She received right TKA in September, 2013, and left TKA in December 2015. Post-operation bilateral ROM: extension −15° and flexion 120°. After operation, she wore corrective casts.

Post TKA, she received manipulation for bilateral knee contractions in 2015, and she began in-patient rehabilitation. Her progress was normal, and became able to stand easily with a walker. However, after discharge, she discontinued treatment for schizophrenia and refused outpatient rehabilitation, possibly due to her schizophrenia. Thereafter, she lost her ability to stand up easily. Her ROM worsened, right: extension −95°, flexion 115°, left: extension −75°, flexion 115°Knee Society Score; Bilateral 13 points.

INTRODUCTION

Shoulder joint prostheses have become the most commonly replaced after knee and hip artificial implants. Reverse shoulder arthroplasty (RSA) is the treatment option for patients with severe osteoarthritis, rotator cuff arthropathy or a massive rotator cuff tear with pseudoparalysis. Though successful, the long-term survival of such implants are limited by wear of the materials in contact [1, 2]. The aim of this study was to investigate RSA wear in vitro using a clinically relevant activities of daily living (ADLs).

MATERIALS AND METHODS

Four new JRI Orthopaedics Reverse Shoulder 42 mm diameter VAIOS with cobalt-chromium (CoCr) glenospheres and ultra-high molecular weight polyethylene (UHMWPE) humeral components were tested. A five million cycles wear test was undertaken using the unique Newcastle Shoulder Wear Simulator with dilute bovine serum as a lubricant. “Mug to mouth” was performed as the ADL to the test prostheses in intervals of 100 cycles, following by 5 seconds of high load (450N) with no motion simulating an ADL such as “lifting an object”. This combined load cycle was then repeated. A fifth reverse shoulder prosthesis was subject to dynamic loading only in a soak control station. Wear was assessed gravimetrically and roughness (Sa) of the articulating surfaces was measured with a non-contacting profilometer.

Introduction

The bearing surfaces of ceramic-on-ceramic (CoC) total hip replacements (THR) show a substantially lower wear rate than metal-on-polyethylene (MoP) THR in-vitro. However, revision rates for CoC THR are comparable with MoP. Our hypothesis that an explanation could be adverse reaction to metal debris (ARMD) from the trunnion led us to investigate the wear at both the bearing surfaces and the taper-trunnion interface of a contemporary CoC THR in an in-vitro study.

Methods

Three 36mm CoC hips were tested in a hip simulator for 5 million cycles (Mc). BIOLOX^®delta ceramic femoral heads were mounted on 12/14 titanium (Ti6Al4V) trunnions. Wear of femoral heads, acetabular liners and trunnions was determined gravimetrically using the analytical balance. Roughness measurements (Sa) were taken on the articulating surfaces (pre and post-test) and on the trunnion surfaces (worn and unworn). Furthermore, Energy Dispersive X-ray Spectroscopy (EDX) was used to identify and quantify the wear debris present in the lubricant using scanning electron microscope (SEM).

Introduction

Metal-on-polyethylene (MoP) is the most commonly used bearing couple in total hip replacements (THRs). Retrieval studies (Cooper et al, 2012, JBJS, Lindgren et al, 2011, JBJS) report adverse reactions to metal debris (ARMD) due to debris produced from the taper-trunnion junction of the modular MoP THRs. A recent retrospective observational study (Matharu et al, 2016, BMC Musc Dis) showed that the risk of ARMD revision surgery is increasing in MoP THRs. To the authors' best knowledge, no hip simulator tests have investigated material loss from the taper-trunnion junction of contemporary MoP THRs.

Methods

A 6-station anatomical hip joint simulator was used to investigate material loss at the articulating and taper-trunnion surfaces of 32mm diameter metal-on-cross-linked polyethylene (MoXLPE) joints for 5 million cycles (Mc) with a sixth joint serving as a dynamically loaded soak control. Commercially available cobalt-chromium-molybdenum (CoCrMo) femoral heads articulating against XLPE acetabular liners (7.5Mrad) were used with a diluted new-born-calf-serum lubricant. Each CoCrMo femoral head was mounted on a 12/14 titanium alloy trunnion. The test was stopped every 0.5Mc, components were cleaned and gravimetric measurements performed following ISO 14242-2 and the lubricant was changed. Weight loss (mg) obtained from gravimetric measurements was converted into volume loss (mm³) and wear rates were calculated from the slopes of the linear regression lines in the volumetric loss versus number of cycles plot for heads, liners and trunnions. Additionally, volumetric measurements of the head tapers were obtained using a coordinate measuring machine (CMM) post-test. The surface roughness (Sa) of all heads and liners was measured pre and post-test. At the end of the test, the femoral heads were cut and the roughness of the worn and unworn area was measured. Statistical analysis was performed using a paired-t-test (for roughness measurements) and an independent sample t-test (for wear rates).

Introduction

Roentgen stereophotogrammetric analysis (RSA) is currently the gold standard to measure early prosthetic migration which can predict aseptic loosening. However, RSA has some limitations such as the need for perioperative placed markers and exposure to X-radiation during follow up. Therefore, this study evaluates if low field MRI could be an alternative for RSA. Low field MRI was chosen because it is less hampered by metal artifacts of the prosthesis than high field MRI.

Methods

3D models of both the tibial component of a total knee prosthesis (Genesis II, Smith and Nephew) and the porcine tibia were made. The tibial component was implanted in the tibial bone. Consequently, 17 acquisitions with the low field MRI scanner (Esaote G-scan 0.25T) in transverse direction with a 2D PD weighted metal artifact reducing sequence PD-XMAR (TE/TR 10/1020ms, slice thickness 3mm, FOV 180×180×120 mm³, matrix size 224×224) were made. The first five acquisitions were made without repositioning the cadaver, the second twelve after slightly repositioning the cadaver within limits that are expected to be encountered in a clinical setting. Hence, in these 17 acquisitions no prosthetic-bone motions were induced.

The scans were segmented and registered with Mimics. Virtual translation and rotation of the prosthesis with respect to the bone between two scans were calculated using a Procrustes algorithm. The first five scans without repositioning were used to calculate the measurement error, the following twelve to calculate the precision of low field MRI to measure prosthetic migration. Results were expressed as the maximum total point motion, mean error and 95% CI and expressed in boxplots.

Background

Failed ingrowth and subsequent separation of revision acetabular components from the inferior hemi-pelvis constitutes a primary mode of failure in revision total hip arthroplasty (THA). Few studies have highlighted other techniques than multiple screws and an ischial flange or hook of cages to reinforce the ischiopubic fixation of the acetabular components, nor did any authors report the use of porous metal augments in the ischium and/or pubis to reinforce ischiopubic fixation of the acetabular cup. The aims of this study were to introduce the concept of extended ischiopubic fixation into the ischium and/or pubis during revision total hip arthroplasty [Fig. 2], and to determine the early clinical outcomes and the radiographic outcomes of hips revised with inferior extended fixation.

Methods

Patients who underwent revision THA utilizing the surgical technique of extended ischiopubic fixation with porous metal augments secured in the ischium and/or pubis in a single institution from 2014 to 2016 were reviewed. 16 patients were included based on the criteria of minimum 24 months clinical and radiographic follow-up. No patients were lost to follow-up. The median duration of follow-up for the overall population was 37.43 months. The patients' clinical results were assessed using the Harris Hip Score (HHS), Western Ontario and McMaster Universities Osteoarthritis (WOMAC) index and Short form (SF)-12 score and satisfaction level based on a scale with five levels at each office visit. All inpatient and outpatient records were examined for complications, including infection, intraoperative fracture, dislocation, postoperative nerve palsy, hematoma, wound complication and/or any subsequent reoperation(s). The vertical and horizontal distances of the center of rotation to the anatomic femoral head and the inclination and anteversion angle of the cup were measured on the preoperative and postoperative radiographs. All the postoperative plain radiographs were reviewed to assess the stability of the components.

Aims

Severe, superior acetabular bone defects are one of the most challenging aspects to revision total hip arthroplasty (THA). We propose a new concept of “superior extended fixation” as fixation extending superiorly 2 cm beyond the original acetabulum rim with porous metal augments, which is further classified into intracavitary and extracavitary fixation. We hypothesized that this new concept would improve the radiographic and clinical outcomes in patients with massive superior acetabular bone defects.

Patients and Methods

Twenty eight revision THA patients were retrospectively reviewed who underwent reconstruction with the concept of superior extended fixation from 2014 to 2016 in our hospital. Patients were assessed using the Harris Hip Score (HHS) and the Western Ontario and McMaster Universities Osteoarthritis Index score (WOMAC). In addition, radiographs were assessed and patient reported satisfaction was collected.

Introduction

Trabecular Titanium is a biomaterial characterized by a regular three-dimensional hexagonal cell structure imitating trabecular bone morphology. Components are built via Electron Beam Melting technology in aone- step additive manufacturing process. This biomaterial combines the proven mechanical properties of Titanium with the elastic modulus provided by its cellular solid structure (Regis 2015 MRS Bulletin). Several in vitro studies reported promising outcomes on its osteoinductive and osteoconductive properties: Trabecular Titanium showed to significantly affect osteoblast attachment and proliferation while inhibiting osteoclastogenesis (Gastaldi 2010 J Biomed Mater Res A, Sollazzo 2011 ISRN Mater Sci); human adipose stem cells were able to adhere, proliferate and differentiate into an osteoblast-like phenotype in absence of osteogenic factors (Benazzo 2014 J Biomed Mater Res A). Furthermore, in vivo histological and histomorphometric analysis in a sheep model indicated that it provided bone in-growth in cancellous (+68%) and cortical bone (+87%) (Devine 2012 JBJS). A multicentre prospective study was performed to assess mid-term outcomes of acetabular cups in Trabecular Titanium after Total Hip Arthroplasty (THA).

Methods

89 patients (91 hips) underwent primary cementless THA. There were 46 (52%) men and 43 (48%) women, with a median (IQR) age and BMI of 67 (57–70) years and 26 (24–29) kg/m2, respectively. Diagnosis was mostly primary osteoarthritis in 80 (88%) cases. Radiographic and clinical evaluations (Harris Hip Score [HHS], SF-36) were performed preoperatively and at 7 days, 3, 6, 12, 24 and 60 months. Bone Mineral Density (BMD) was determined by dual-emission X-ray absorptiometry (DEXA) according to DeLee &Charnley 3 Regions of Interest (ROI) postoperatively at the same time-points using as baseline the measureat 1 week. Statistical analysis was carried out using Wilcoxon test.

INTRODUCTION

Variability in placement of total shoulder arthroplasty (TSA) glenoid implants has led to the increased use of 3D CT preoperative planning software. Computer assisted surgery (CAS) offers the potential of improved accuracy in TSA while following a preoperative plan, as well as the flexibility for intraoperative adjustment during the procedure. This study compares the accuracy of implantation of reverse total shoulder arthroplasty (rTSA) glenoid implants using a CAS TSA system verses traditional non-navigated techniques in 30 cadaveric shoulders relative to a preoperative plan from 3D CT software.

METHODS

High resolution 1mm slice thickness CT scans were obtained on 30 cadaveric shoulders from 15 matched pair specimens. Each scan was segmented and the digital models were incorporated into a preoperative planning software. Five fellowship trained orthopedic shoulder specialists used this software to virtually place a rTSA glenoid implant as they deemed best fit in six cadavers each. The specimens were randomized with respect to side and split into a cohort utilizing the CAS system and a cohort utilizing conventional instrumentation, for a total of three shoulders per cohort per surgeon. A BaSO₄ PEEK surrogate implant identical in geometry to the metal implant used in the preoperative plan was used in every specimen, to maintain high CT resolution while minimizing CT artifact. The surgeons were instructed to implant the rTSA implants as close to their preoperative plans as possible for both cohorts. In the CAS cohort, each surgeon used the system to register the native cadaveric bones to each respective CT, perform the TSA procedure, and implant the surrogate rTSA implant. The surgeons then performed the TSA procedure on the opposing side of the matched pair using conventional instrumentation.

Postoperatively, CT scans were repeated on each specimen and segmented to extract the digital models. The pre- and postoperative scapulae models were aligned using a best fit match algorithm, and variance between the virtual planned position of the implant and the executed surgical position of the implant was calculated [Fig 1].

Introduction

Acetabular bone defects are still challenging to quantify. Numerous classification schemes have been proposed to categorize the diverse kinds of defects. However, these classification schemes are mainly descriptive and hence it remains difficult to apply them in pre-clinical testing, implant development and pre-operative planning. By reconstructing the native situation of a defect pelvis using a Statistical Shape Model (SSM), a more quantitative analysis of the bone defects could be performed. The aim of this study is to develop such a SSM and to validate its accuracy using relevant clinical scenarios and parameters.

Methods

An SSM was built on the basis of segmented 66 CT dataset of the pelvis showing no orthopedic pathology. By adjusting the SSM's so called modes of shape variation it is possible to synthetize new 3D pelvis shapes. By fitting the SSM to intact normal parts of an anatomical structure, missing or pathological regions can be extrapolated plausibly.

The validity of the SSM was tested by a Leave-one-out study, whereby one pelvis at a time was removed from the 66 pelvises and was reconstructed using a SSM of the remaining 65 pelvises. The reconstruction accuracy was assessed by comparing each original pelvis with its reconstruction based on the root-mean-square (RMS) surface error and five clinical parameters (center of rotation, acetabulum diameter, inclination, anteversion, and volume). The influence of six different numbers of shape variation modes (reflecting the degrees of freedom of the SSM) and four different mask sizes (reflecting different clinical scenarios) was analyzed.

Introduction

Bone fracture toughness is an important parameter in resistance of bone to monotonic and fatigue failure. Earlier studies on bone fracture toughness were focused on either cortical or cancellous bone, separately [1, 2]. Reported fracture toughness values indicated that cortical bone is tougher to break as compared to cancellous bone. In order to understand complete fracture of a whole bone, the interface between cortical and cancellous bone (named as corticellous bone) might play a crucial role and is interesting topic of research. The goal of this study was to identify fracture toughness in terms of J integral and fracture mechanism of the corticellous bone.

Material and Methods

Corticellous bone samples (single edge notch bend specimen or SENB) were prepared from bovine proximal femur according to ASTM E399-90 standard (Fig.1). For corticellous bone, samples were prepared in such way that approximately half of the sample width consist of cortical bone and another half is cancellous bone. Precaution was taken while giving notch and pre-crack to corticellous bone that pre-crack should not enter from cortical to cancellous portion. All specimens were tested using a universal testing machine (Tinius Olsen, ± 100 N) under displacement rate of 100 µm/min until well beyond yield point. The fracture toughness parameter in terms of critical stress intensity (K_IC) was calculated according to ASTM E399-90 as given by, (1)KIC=PS/BW1.5*f(a/W)…

Where, P = applied load in kN, S = loading span in cm, B = specimen thickness in cm, W = specimen width in cm, a = total crack length, f(a/W) = geometric function. After the fracture test the J integral of each specimen was calculated using following equation. [ASTM E1820]. (2)Jtotal=Jel+Jpl=KIC2/E′+2Apl/Bb0…

Where, J_el is J integral of the elastic deformation, J_pl is J integral of the plastic deformation, E′=E for plane stress condition and E′= E/(1−ν²) for plane strain condition (E is elastic modulus; ν is Poisson's ratio), b_o = W−a_o, height of the un-cracked ligament, and A_pl is the area of the plastic deformation part in the load–displacement curve.

INTRODUCTION

Component positioning of an artificial hip joint plays a key role in durability of implant. Despite the fact that a number of numerical, experimental and clinical studies have been carried out to investigate the effects of cup inclination on polyethylene wear, steep inclination has been reported to be associated with both high and low volumetric wear. Moreover, how cup anteversion affects wear and its interaction with inclination are still unclear. To address these knowledge gaps, in this study wear and contact mechanics of a hip joint under various cup positioning has been investigated by using FEA (Finite Element Analysis).

METHOD

A Pinnacle^® Marathon neutral liner 36×56mm was chosen to model the wear and creep over 3 million cycles (mc) based on the Archard's law and modified time hardening model in ANSYS, respectively. Central composite design of response surface method was used to generate 9 FEA runs, where the operative inclination angles varied from 35º, 45º to 55º and operative anteversion angles differed amongst 0º, 15º and 30º. The range of cup angles were chosen to be similar to the Lewinnek “golden” safe zone for dislocation. The gait cycle as specified in ISO 14242-1 was applied to the femoral head.

Introduction

The knowledge of the right amount of tension of the collateral ligaments in native knees is one of the hot topics to restore the normal kinematics in TKA. To guarantee stability in TKA there should be enough tension necessary but no overtensioning. In this study we could confirm that the tension of the ligaments is not more than 20–25N on each side (in total 40–50N) to achieve stability in the knee joint.

Methods and materials

During an experimental activity we examined 5 cadaveric knee specimenwith intact ligaments. With the knee in full extension, a constant force was applied on the femoral bone and the displacement was measured up a plateau was reached. This test was conducted for a knee joints with intact cruciates, then we sacrificed the anterior cruciate and in a third step the posterior cruciate even to find out if there is any change in extending the joint comparing distance and tension.

Introduction

An increasing trend in the incidence of primary and revision bone replacements has been observed throughout the last decades, mainly among patients under 65 years old.10-year revision rates are estimated in the 5–20% range, mainly due to peri-implant bone loss. Recent advances allow the design of implants with custom-made geometries, nanometer-scale textured surfaces and multi-material structures. Technology also includes (bio)chemical modifications of the implants' surfaces. However, these approaches present significant drawbacks, as their therapeutic actuations are unable to: (1) perform long-term release of bioactive substances, namely after surgery; (2) deliver personalized stimuli to target bone regions and according to bone-implant integration states.

The Innovative Concept

Here we propose the design of instrumented active implants with ability to deliver personalized biophysical stimuli, controlled by clinicians, to target regions in the bone-implant interface throughout the patients' lifetime. The idea is to design bone implants embedding actuators, osseointegration sensors, wireless communication and self-powering systems. This work proposes an advanced therapeutic actuator for personalized bone stimulation, and a self-powering system to electrically supply these advanced implants.

BACKGROUND

Total hip revision surgery in cases with previous multiple reconstructive procedures is a challenging treatment due to difficulties in treatment huge bone defects with standard revision prosthetic combinations. A new specially made production system in Electron-Beam Melting (EBM) technology based on a precise analysis of patients' preoperative CT scans has been developed.

METHODS

Objectives of design customization in difficult cases are to correctly evaluate patient's anatomy, to plan a surgical procedure and to obtain an optimal fixation to a poor bone stock. The 3D Printing (EBM) technology permits to create an extremely flexible patient matching implant and instrument, with material performances not viable with standard manufacturing process. Dedicated visual 3D tools and instrumentations improve implants congruency according to preoperative plan. Primary stability is enhanced and tailored on patient's anatomy by means of press-fit, iliac stems and the high friction performances of Trabecular Titanium matrix. The use of bone screws and their position is designed to enhance primary stability, even in critical bone conditions, avoiding implant stress shielding and allowing bone integration. 4 cases (2 men and 2 women) of acetabular customized implants were performed. Mean age at surgery was 51.5 years (range 25–72). Patients were reviewed clinically and radiographically at follow-up.

Introduction

Tibial component malrotation is one of the commonest causes of pain and stiffness following total knee arthroplasties, however, the assessment of tibial component malrotation on imaging is not a clear-cut.

Aim

The objective of this study was to assess tibial component rotation in cases with pain following total knee replacement using MRI with metal artifact reduction technique.

Introduction

Partial knee arthroplasty (PKA) has demonstrated the potential to improve patient satisfaction over total knee arthroplasty. It is however perceived as a more challenging procedure that requires precise adaptation to the complex mechanics of the knee. A recently developed PKA system aims to address these challenges by anatomical, compartment specific shapes and fine-tuned mechanical instrumentation. We investigated how closely this PKA system replicates the balance and kinematics of the intact knee.

Materials and Methods

Eight post-mortem human knee specimens (age: 55±11 years, BMI: 23±5, 4 male, 4 female) underwent full leg CT scanning and comprehensive robotic (KUKA KR140 comp) assessments of tibiofemoral and patellofemoral kinematics. Specimens were tested in the intact state and after fixed bearing medial PKA. Implantations were performed by two experienced surgeons.

Assessments included laxity testing (anterior-posterior: ±100 N, medial-lateral: ±100 N, internal-external: ±3 Nm, varus- valgus: ±12 Nm) under 2 compressive loads (44 N, 500 N) at 7 flexion angles and simulations of level walking, lunge and stair descent based on in-vivo loading profiles. Kinematics were tracked robotically and optically (OptiTrack) and represented by the femoral flexion facet center (FFC) motions. Similarity between intact and operated curves was expressed by the root mean square of deviations (RMSD) along the curves. Group data were summarized by average and standard deviation and compared using the paired Student's T-test (α = 0.05).

Introduction

In knee biomechanics the concept of the envelope of motion (EOM) has proven to be a powerful method to characterize joint mechanics and the effect of surgical interventions. It is furthermore indispensable for numerical model validation. While commonly used for tibiofemoral kinematics, there is very little report of applying the concept to patellofemoral kinematics. EOM measurements require precise and reproducible displacement and load control in all degrees of freedom (DOF), which robotic testing has proven to provide. The objectives of this study were therefore to (1) develop a robotic method to assess patellofemoral EOM as a function of tibiofemoral EOM, (2) compare resulting patellofemoral kinematics to published data, and (3) determine which DOFs in the tibiofemoral EOM mostly account for the patellofemoral EOM.

Material and Methods

The developed robotic (KUKA KR140 comp) method was evaluated using 8 post-mortem human leg specimens of both genders (age: 55±11 years, BMI: 23±5). Firstly, tibiofemoral neutral flexion was established as well as the EOM by applying anterior-posterior (±100 N), medial-lateral (±100 N), internal-external (±4 Nm) and varus-valgus (±12 Nm) loads under low compression (44 N) at 7 flexion angles. Secondly, patellofemoral flexion kinematics and EOM were measured during a robotic playback of the previously established tibiofemoral kinematics. During these measurements, the quadriceps tendon was loaded with a hanging weight (20 kg) via a pulley system directing the force to the anterior superior iliac spine. Kinematics were tracked optically (OptiTrack) and registered to CT scans using co-scanned aluminum cylinders and beads embedded in the patella.

The overall patellofemoral EOM was calculated as the extent of patellar motion observed during manipulating the tibia inside the tibiofemoral EOM in all DOFs. Additionally, patellofemoral EOMs were calculated for tibial manipulations along individual DOFs to analyze the importance of these DOFs.

Introduction and aims

The International Orthopaedic community is eagerly adopting Robotic Assisted Arthroplasty (RAA) technology. However, the evidence for the benefits of this technology are unproven and at best equivocal. This study is a comprehensive bibliometric analysis of all published research in the field of RAA.

Methods

A systematic literature search was conducted to retrieve all peer-reviewed, English language, publications studying robot- assisted hip and knee arthroplasty between 1992 and 2017. Review articles were excluded. Articles were classified by type of study and level of evidence according to the Oxford Centre for Evidence-based Medicine (OCEBM) Levels of Evidence System. The number of citations, authorship, year of publication, journal of publication, and country and institution of origin were also recorded for each publication.

Introduction and aims

Robotic Assisted Arthroplasty (RAA) is increasingly proliferative in the international orthopaedic environment. Traditional bibliometric methods poorly assess the impact of surgical innovations such as robotic technology. Progressive Scholarly Acceptance (PSA) is a new model of bibliographic analysis which quantitatively evaluates the impact of robotic technology in the orthopaedic scientific community.

Methods

A systematic literature search was conducted to retrieve all peer-reviewed, English language publications studying robotic assisted hip and knee arthroplasty between 1992 and 2017. Review articles were excluded. Articles were classified as either “initial investigations” or “refining studies” according to the PSA model, described by Schnurman and Kondziolka. The PSA end-point is defined as the point in time when the number of studies focussed on refining or improving a novel technique (RAA) outnumbers the number of initial studies assessing its efficacy.

INTRODUCTION

Lumbar total disc replacement (TDR) is an alternative treatment to avoid fusion related adverse events, specifically adjacent segment disease. New generation of elastomeric non-articulating devices have been developed to more effectively replicate the shock absorption and flexural stiffness of native disc. This study reports 5 years clinical and radiographic outcomes, range of motion and position of the center of rotation after a viscoelastic TDR.

Material and methods

This prospective observational cohort study included 61 consecutive patients with monosegmental TDR. We selected patients with intermediate functional activity according to Baecke score. Hybrid constructs had been excluded. Only cases with complete clinical and radiological follow-up at 3, 6, 12, 24 and 60 months were included. Mean age at the time of surgery was 42.8 +7.7 years-old (27–60) and mean BMI was 24.2 kg/m² +3.4 (18–33). TDR level was L5-S1 in 39 cases and L4-L5 in 22 cases.

The clinical evaluation was based on Visual Analog Scale (VAS) for pain, Oswestry Disability Index (ODI) score, Short Form-36 (SF36) including physical component summary (PCS) and mental component summary (MCS) and General Health Questionnaire GHQ28. The radiological outcomes were range of motion and position of the center of rotation at the index and the adjacent levels and the adjacent disc height changes.

Introduction

Manipulation under anesthesia (MUA) after total knee arthroplasty (TKA) helps restore range of motion. This study identifies MUA risk factors to support early interventions to improve functionality.

Methods

Data was retrospectively reviewed in 2,925 primary TKAs from October 2013 through December 2015 from 13 orthopedic surgeons using hospital and private practice electronic medical records (EMR).

Statistical analysis evaluated MUA and non-MUA groups, comparing demographic, operative, hospital-visit, and clinical factors. T-test, chi-square test, ANOVA and regression analysis were performed. Significance was set at p<0.05.

Aim

The objective of this study was to evaluate the intermediate term clinical and radiological results of a new short stem hip implant.

Methods

In 20 consecutive patients suffering from osteoarthritis with 25 affected hip joints (five cases were bilateral), the clinical and radiological results of 25 hip arthroplasties performed in one hospital between October 2009 and May 2014 through a minimally invasive anterolateral approach using a cementless short stem prosthesis type Aida and a cementless cup type Ecofit with a ceramic on ceramic pairing were evaluated prospectively. The median age of patients at time of surgery was 60 years (range, 42–71 years), 15 male (4 were bilateral) and 5 female patients (one was bilateral) were included in the study. The median clinical follow up was 30 months (range, 2–88 months), and the median radiological follow up was 30 months (range, 2–88 months).

Introduction

Uncemented porous coated acetabular components have gained more research emphasis in recent years compared to their cemented counterparts, largely owing to the natural biological fixation they offer. Nevertheless, sufficient peri-prosthetic bone ingrowth is essential for long-term fixation of such uncemented acetabular components. The phenomenon of bone ingrowth can be predicted based on mechanoregulatory principles of primary bone fracture healing. Literature review reveals that the surface texture of implant plays a major role in implant-bone fixation mechanism. A few insilico models based on 2-D microscale finite elements (FE) were reported in literatures to predict the influence of surface texture designs on peri-prosthetic bone ingrowth. However, most of these studies were based on FE models of dental implants. The primary objective of this study, therefore, is to mechanobiologically predict the influence of surface texture on bone- ingrowth in acetabular components considering a novel 3-D mesh-shaped surface texture on the implant.

Materials/Methods

The 3-D microscale model [Fig.1] of implant-bone interface was developed using CATIA^® V5R20 software (DassaultSystèmes, France) and was modelled in ANSYS V15.0 FE software (Ansys Inc., PA, USA) using coupled linear elastic ten-noded tetrahedral finite elements. The model consists of cast-inbeaded mesh textured implant having finely meshed inter-bead spacing. Linear, elastic and isotropic material properties considering Young's modulus of 210 GPa and Poisson's ratio of 0.3 for stainless steel implant were employed in the model. Boundary of bone was assumed to be rich in Mesenchymal Stem Cells(MSC) with periodic boundary conditions at contralateral surfaces. The linear elastic material properties in the model were updated iteratively through a tissue differentiation algorithm that works on the principle of mechanotransduction driven by local mechanical stimuli, e.g. hydrostatic pressure and equivalent deviatoric strain.

Background

Postural change after total hip arthroplasty (THA) is still a matter of discussion. Previous studies have mainly concentrated on the pelvic motions. We report the postoperative changes of the global sagittal posture using pelvic, spinal and lower extremities parameters.

Methods

139 patients (primary THA, without previous spinal or lower extremity surgery) were included. We measured pelvic parameters [SS: Sacral Slope, PI: Pelvic Incidence, PT: Pelvic Tilt, APP angle: Anterior Pelvic Plane angle] and the global posture parameters (SVA: Sagittal Vertical Angle, GSA: Global Sagittal Angle, TPA: T1 pelvic angle). Patients were categorized into low PI group <45°, 45°< medium PI <65° and high PI >65°.

Introduction

Literature describes pelvic rotation on lateral X rays from standing to sitting position. EOS full body lateral images provide additional information about the global posture. The projection of the vertical line from C7 (C7 VL) is used to evaluate the spine balance. C7 VL can also measure pelvic sagittal translation (PST) by its horizontal distance to the hip center (HC). This study evaluates the impact of a THA implantation on pelvic rotation and sagittal translation.

Materials and Method

Lumbo-pelvic parameters of 120 patients have been retrospectively assessed pre and post- operatively on both standing and sitting acquisitions (primary unilateral THA without complication). PST is zero when C7VL goes through the center of the femoral heads and positive when C7VL is posterior to the hips' center (negative if anterior). Three subgroups were defined according to pelvic incidence (PI): low PI <45°, 45°<normal PI<65° or high PI>65°.

Objective

We explanted NeuFlex metacarpophalangeal (MP) joint prostheses to identify common features, such as position of fracture, and thus better understand the reasons for implant failure.

Methods

Explanted NeuFlex MP joint prostheses were retrieved as part of an-ongoing implant retrieval programme. Following revision MP joint surgery the implants were cleaned and sent for assessment. Ethical advice was sought but not required. The explants were photographed. The position of fracture, if any, was noted. Patient demographics were recorded.

Introduction

Stand to sit pelvis kinematics is commonly considered as a rotation around the bicoxofemoral axis. However, abnormal kinematics could occur for patients with musculoskeletal disorders affecting the hip-spine complex. The aim of this study is to perform a quantitative analysis of the stand to sit pelvis kinematics using 3D reconstruction from bi-planar x-rays.

Materials and Methods

Thirty healthy volunteers as a control group (C), 30 patients with hip pathology (Hip) and 30 patients with spine pathology (Spine) were evaluated. All subjects underwent standing and sitting full-body bi-planar x-rays. 3D reconstruction was performed in each configuration and then translated such as the middle of the line joining the center of each acetabulum corresponds to the origin. Rigid registration quantified the finite helical axis (FHA) describing the transition between standing and sitting with two specific parameters. The orientation angle (OA) is the signed 3D angle between FHA and bicoxofemoral axis and the rotation angle (RA) represents the signed angle around FHA. Pelvic incidence, sacral slope and pelvic tilt were also measured. After checking normality of distribution, parameters were compared statistically between the 3 groups (p<0.05).

Background

Established hip and knee arthroplasty registers exist in many countries but this is not the case with spinal implants. Moreover, in the case of a rod intended to guide spinal growth in a child and then be removed, the definition of ‘failure’ (revision) used for hip or knee arthroplasty is inappropriate. How can the performance of such spinal implants be judged?

Methods

Ninety-six MAGnetic Expansion Control (MAGEC) spinal rods were obtained from multiple centres after removal from the spines of 52 children with scoliosis. Clinical details were assessed and divided between unplanned revision operations (‘failures’) and those which were planned. Of the explanted rods, 49 were tested for the amount of force they could output, using the manufacturer's supplied test jig. Sixty-five rods were cut apart so that the internal components (bearings, O-ring seals, drive pins) could be assessed, alongside if there was evidence of internal wear.

INTRODUCTION

There is great potential for the use of computational tools within the design and test cycle for joint replacement devices.

The increasing need for stratified treatments that are more relevant to specific patients, and implant testing under more realistic, less idealised, conditions, will progressively increase the pre-clinical experimental testing work load. If the outcomes of experimental tests can be predicted using low cost computational tools, then these tools can be embedded early in the design cycle, e.g. benchmarking various design concepts, optimising component geometrical features and virtually predicting factors affecting the implant performance. Rapid, predictive tools could also allow population-stratified scenario testing at an early design stage, resulting in devices which are better suited to a patient-specific approach to treatment.

The aim of the current study was to demonstrate the ability of a rapid computational analysis tool to predict the behaviour of a total hip replacement (THR) device, specifically the risk of edge loading due to separation under experimental conditions.

METHODS

A series of models of a 36mm BIOLOX^® Delta THR bearing (DePuy Synthes, Leeds, UK) were generated to match an experimental simulator study which included a mediolateral spring to cause lateral head separation due to a simulated mediolateral component misalignment of 4mm. A static, rigid, frictionless model was implemented in Python (PyEL, runtime: ∼1m), and results were compared against 1) a critically damped dynamic, rigid, FE model (runtime: ∼10h), 2) a critically damped dynamic, rigid, FE model with friction (µ = 0.05) (runtime: ∼10h), and 3) kinematic experimental test data from a hip simulator (ProSim EM13) under matching settings (runtime: ∼6h). Outputs recorded were the variation of mediolateral separation and force with time.

Introduction and Aims

A recent submission to ASTM, WK28778 entitled “Standard test method for determination of friction torque and friction factor for hip implants using an anatomical motion hip simulator”, describes a proposal for determining the friction factor of hip implant devices. Determination of a friction factor in an implant bearing couple using a full kinematic walking cycle as described in ISO14242-1 may offer designers and engineers valuable input to improve wear characteristics, minimize torque and improve long term performance of hip implants. The aim of this study was to investigate differences in friction factors between two commercially available polyethylene materials using the procedure proposed.

Methods

Two polyethylene acetabular liner material test groups were chosen for this study: commercially available Marathon^® (A) and AltrX^® (B). All liners were machined to current production specifications with an inner diameter of 36mm and an outer diameter of 56mm. Surface roughness (Ra) of the liner inner diameters were measured using contact profilometry in the head-liner contact area, before and after 3Mcyc of wear testing. Liners were soaked in bovine serum for 48 hours prior to testing. Friction factor measurements were taken per ASTM WK28778 prior to, and after wear testing using an external six degrees of freedom load cell (ATI Industrial Automation) and a reduced maximum vertical load of 1900N.

Friction factor and wear testing was conducted in bovine serum (18mg/mL total protein concentration) supplemented with 0.056% sodium azide (preservative) and 5.56mM EDTA (calcium stabilizer) on a 12-station AMTI (Watertown, MA) ADL hip simulator with load soak controls per ISO 14242-1:2014(E). The liners were removed from the machine, cleaned and gravimetric wear determined per ISO 14242-2:2000(E) every 0.5 million cycles (MCyc) through a total of 3Mcyc to evaluate wear.

Introduction

PEEK-OPTIMA™ has been considered as an alternative to cobalt chrome in the femoral component of total knee replacements. Wear simulation studies of both the tibiofemoral and patellofemoral joints carried out to date have shown an equivalent wear rate of UHMWPE tibial and patella components against PEEK and cobalt chrome (CoCr) femoral components implanted under optimal alignment conditions. In this study, fundamental pin-on-plate studies have been carried out to investigate the wear of UHMWPE-on-PEEK under a wider range of contact pressure and cross-shear conditions.

Methods

The study was carried out in a 6 station multi-axial pin-on-plate reciprocating rig. UHMPWE pins (conventional, non- sterile) were articulated against PEEK-OPTIMA™ plates, initial Ra ∼0.02µm. The lubricant used was 25% bovine serum (17g/l) supplemented with 0.03% sodium azide. The contact pressure and cross-shear ratio conditions were selected to replicate those in total knee replacements and to be comparable to previously reported studies of UHMPWE-on-CoCr tested in the same pin-on-plate simulators. Contact pressures from 2.1 to 25.5MPa were created by changing the diameter of the contact face of the pin, the cross-shear ratios ranged from 0 (uniaxial motion) to 0.18. Wear of the UHMWPE pins was measured gravimetrically and the surface topography of the plates assessed using a contacting Form Talysurf. N=6 was carried out for each condition and statistical analysis carried out using ANOVA with significance taken at p<0.05.

Introduction

Mechanical property relationships used in the computational modeling of bones are most often derived using mechanical testing of normal cadaveric bone. However, a significant percentage of patients undergoing joint arthroplasties exhibit some form of pathologic bone disease, such as osteoarthritis. As such, the objective of this study was to compare the micro-architecture and apparent modulus (E_app) of humeral trabecular bone in normal cadaveric specimens and bone extracted from patients undergoing total shoulder arthroplasty.

Methods

Micro-CT scans were acquired at 20 µm spatial resolution for humeral heads from non-pathologic cadavers (n=12) and patients undergoing total shoulder arthroplasty (n=10). Virtual cylindrical cores were extracted along the medial-lateral direction. Custom-code was used to generate micro finite element models (µFEMs) with hexahedral elements. Each µFEM was assigned either a homogeneous tissue modulus of 20 GPa or a heterogeneous tissue modulus scaled by CT- intensity. Simulated compression to 0.5% apparent strain was performed in the medial-lateral direction. Morphometric parameters and apparent modulus-bone volume fraction relationships were compared between groups.

Introduction

The Walch Type B2 glenoid has the hallmark features of posteroinferior glenoid erosion, retroversion, and posterior humeral head subluxation. Although our understanding of the pathoanatomy of bone loss and its evolution in Type B's has improved, the etiology remains unclear. Furthermore, the morphology of the humerus in Walch B types has not been studied. The purpose of this imaging based anthropometric study was to examine the humeral torsion in Walch Type B2 shoulders. We hypothesized that there would be a compensatory decrease in humeral retroversion in Walch B2 glenoids.

Methods

Three-dimensional models of the full length humerus were generated from computed tomography data of normal cadaveric (n = 59) and Walch Type B shoulders (n = 59). An anatomical coordinate system referencing the medial and lateral epicondyles was created for each model. A simulated humeral head osteotomy plane was created and used to determine humeral version relative to the epicondylar axis and the head-neck angle. Measurements were repeated by two experienced fellowship-trained shoulder surgeons to determine inter-rater reliability. Glenoid parameters (version, inclination and 2D critical shoulder angle) and posterior humeral head subluxation were calculated in the Type B group to determine the pathologic glenohumeral relationship. Two-way ANOVAs compared group and sex within humeral version and head-neck angle, and intra-class correlation coefficients (ICCs) with a 2-way random effects model and absolute agreement were used for inter-rater reliability.

Introduction

Spatial orientation of the pelvis in the sagittal plane is a key parameter for hip function. Pelvic extension (or retroversion) and pelvic flexion(or anteversion) are currently assessed using Sacral Slope (SS) evaluation (respectively SS decrease and SS increase). Pelvic retroversion may be a risk situation for THA patients. But the magnitude of SS is dependant on the magnitude of pelvic incidence (PI) and may fail to discriminate pelvic position due to patient's anatomy and the potential adaptation mechanisms: a high PI patient has a higher SS but this situation can hide an associated pelvic extension due to compensatory mechanisms of the pelvic area. A low PI patient has a lower SS with less adaptation possibilities in case of THA especially in aging patients. The individual relative pelvic version (RPV) is defined as the difference between « measured SS » (SSm) minus the « normal SS »(SSn) described for the standard population. The aim of the study was to evaluate RPV in standing and sitting position with a special interest for high and low PI patients.

Materials and Methods

96 patients without THA (reference group) and 96 THA patients were included. Pelvic parameters (SS and PI) were measured on standing and sitting EOS images. RPV standing (SSm-SSn) was calculated using the formula SSm – (9 + 0.59 × PI) according to previous publications. SSn in sitting position was calculated according to PI using linear regression: RPV sitting was calculated using the formula RPV = SS – (3,54+ 0,38 × PI). Three subgroups were defined according to pelvic incidence (PI): low PI <45°, 45°<normal PI<65° or high PI>65°.

Introduction

Total joint arthroplasty (TJA) is projected to be the most common elective surgical procedure in the coming decades, however TJA now accounts for the largest expenditure per procedure for Medicare and Medicaid provided interventions. This is coupled with increasing complexity of surgical care and concerns about patient satisfaction. The Perioperative Surgical Home (PSH) model has been proposed as a method to both improve patient care and reduce costs. The PSH model provides evidence-based protocols and pathways from the time of surgical decision to after postoperative discharge. PSH pathways can further be standardized with integration into electronic medical records (EMRs). The purpose of this study is to see if the implementation of PSH with and without EMR integration effects patient outcomes and cost.

Methods

A retrospective review was performed for all patients who underwent elective primary total joint arthroplasty at our institution from January 1, 2012 to April 1, 2018. Three cohorts were compared. The first cohort included patients before the implementation of the PSH model (January 1, 2012 - December 31, 2014). The second cohort included patients in the PSH model without EMR integration (January 1, 2015 – August 1, 2016). The third cohort included patients in the PSH model with EMR integration (August 1, 2016 - April 1, 2018). The clinical outcome criteria measured were average hospital length of stay (LOS), 30-day readmission rates, and discharge disposition. Financial data was collected for each cohort and primary measurements included average total cost, diagnostic cost, anesthesia cost, laboratory cost, room and board cost, and physical therapy cost.

Introduction

Cementless total knee arthroplasty (TKA) designs are clinically successful and allow for long term biological fixation. Utilizing morselized bone to promote biological fixation is a strategy in cementless implantation. However, it is unknown how bone debris influences the initial placement of the tray. Recent findings show that unseated tibia trays without good contact with the tibial resection experience increased motion. This current study focuses on the effect of technique and instrument design on the initial implantation of a cementless porous tibia. Specifically, can technique or instrument design influence generation of bone debris, and thereby change the forces required to fully seat a cementless tray with pegs?

Methods

This bench top test measured the force-displacement curve during controlled insertion of a modern cementless tibia plate with two fixation pegs. A total of nine pairs of stripped human cadaver tibias were prepared according to the surgical technique. However, the holes for the fixation pegs were drilled intentionally shallow to isolate changes in insertion force due to the hole preparation. A first generation instrument set (Instrument 1.0) and new instrument set design (Instrument 2.0), including a new drill bit designed to remove debris from the peg hole, were used. The tibias prepared with Instrument 1.0 were either cleaned to remove bone debris from the holes or not cleaned. The tibias prepared with the Instrument 2.0 instruments were not cleaned, resulting in three groups: Instrument 1.0 (n=7), Instrument 1.0 Cleaned (n=5), and Instrument 2.0 (n=6). Following tibia resection and preparation of holes for the fixation pegs, the tibias were cut and potted in bone cement ensuring the osteotomy was horizontal. The tibial tray was mounted in a load frame (Enduratec) and the trays were inserted at a constant rate (0.169mm/sec) while recording the force. The test was concluded when the pegs were clearly past the bottom of the intentionally shallow holes.

Introduction

Total-knee-arthroplasty (TKA) is a well-established method to restore the joint function of the human knee. Different types of TKA designs are clinically available which can be divided in two main groups, the posterior-cruciate- ligament (PCL) sacrificing and retaining group. However, pre-operatively it is often difficult to plan for one or the other. Therefore, the research question was: Is it possible to develop a TKA bearing design which works for both the cruciate sacrificing and retaining technique? A medial-congruent (MC) bearing design was developed, characterized by a high medial sagittal conformity and lower lateral sagittal conformity, which can be used for both cruciate ligament states. This study compares the laxity and kinematics of this MC design to a contemporary PS design for the cruciate sacrificing technique and to a contemporary CR design for the cruciate retaining technique.

Methods

Four specimen-specific computer models of the human knee, consisting of a femur, tibia and fibula bone as well as the contribution of the ligaments and capsule, were virtually implanted with three TKA designs in four constellations: 1) MC without PCL, 2) MC with PCL, 3) contemporary PS without PCL and 4) contemporary CR with PCL following the design specific surgical technique and tibia slopes. Laxity tests in internal-external rotation (moment ± 4 Nm) were performed with the implanted models for a weight bearing case (500N compression). In addition, a high demanding activity (lunge) was simulated. The resulting averaged laxities and kinematics were analysed and compared to each other.

Aims

Metal-on-metal total hip replacements (MoM THRs) are frequently revised. However, there is a paucity of data on clinical outcomes following revision surgery in this cohort. We report on outcomes from the largest consecutive series of revisions from MoM THRs and consider pre-revision factors which were prognostic for functional outcome.

Materials and Methods

A single-centre consecutive series of revisions from MoM THRs performed during 2006–2015 was identified through a prospectively maintained, purpose-built joint registry. The cohort was subsequently divided by the presence or absence of symptoms prior to revision. The primary outcome was functional outcome (Oxford Hip Score (OHS)). Secondary outcomes were complication data, pre- and post-revision serum metal ions and modified Oxford classification of pre-revision magnetic resonance imaging (MRI). In addition, the study data along with demographic data was interrogated for prognostic factors informing on post-revision functional outcome.

Introduction

Total-knee-arthroplasty (TKA) is used to restore knee function and is a well-established treatment of osteoarthritis. Along with the widely used fixed bearing TKA design, some surgeons opt to use mobile bearing designs. The mobile-bearing TKA is believed to allow for more freedom in placement of the tibial plate, greater range of motion in internal-external (IE) rotation and greater constraint through the articular surface. This current study evaluates 1) the kinematics of a high constraint three condyle mobile bearing TKA, 2) the insert rotation relative to the tibia, and 3) compares them with the intact knee joint kinematics during laxity tests and activities-of-daily-living (lunge, level walking, stairs down). We hypothesize that 1) in contrast to the intact state the anterior-posterior (AP) stability of the implanted joint increases when increasing compression level while 2) maintaining the IE mobility, and that 3) the high constraint does not prevent differential femorotibial rollback during lunge.

Methods

Six fresh-frozen human cadaveric knee joints with a mean donor age of 64.5 (±2.4) years and BMI of 23.3 (±7.3) were tested on a robot (KR140, KUKA) in two different states: 1) intact, 2) after implantation of a three condyle mobile bearing TKA. The tibia plateau and the insert of each tested specimen were equipped with a sensor to measure the insert rotation during testing. Laxity tests were done at extension and under flexion (15°, 30°, 45°, 60° 90°, 120°) by applying subsequent forces in AP and medial-lateral (ML) of ±100N and moments in IE and varus-valgus (VV) rotation (6Nm/4Nm, 12 Nm/-). Testing was performed under low (44N) and weight bearing compression (500N). Loading during the lunge, level walking and stairs descent activity was based on in-vivo data. Resulting data was averaged and compared with the kinematics of the intact knee.

Background

The aim of this study is to analysis the ability of these patients, treated with MOMHR, to resume sport activities by gait analysis and clinical evaluations. Metal on metal hip resurfacing (MOMHR) is indicated to treat symptomatic hip osteoarthritis in young active patients. These patients require a high level of function and desire to resume sport activities after surgery.

Study Design & Methods

30 consecutive male patients playing high impact sports with unilateral hip osteoarthritis and normal contralateral hip were included in the study, they were treated with MOMHR by the same surgeon. No patients were lost to follow. The mean age at operation was 39.1 years (range 31 to 46). Primary diagnosis was osteoarthritis. OHS, HHS, UCLA activity score were completed at pre-operative time, six months and one year after surgery. Functionally, gait analysis was performed in all patients 6 months and one year after surgery. A stereophotogrammetric system (Smart-DX, BTS, Milano, Italy, 10 cameras, 250Hz) and two platforms (9286BA Kistler Instrumente AG, Switzerland) were used. Cluster of 4 markers were attached on the skin of each bone segment, a number of anatomical landmarks were calibrated and segment anatomical frames defined, markers were positioned by the same operator. Walking, running and squat jump were analyzed and strength and range of movement of the hips and knees were calculated.

Introduction

While TKA procedures have demonstrated clinical success, medial/lateral overhang of the femoral component in total knee arthroplasty (TKA) of ≥3mm may be associated with an increased risk of knee pain, and distal femoral size may vary across ethnic populations. The aim of this study was to determine and compare the prevalence of femoral component overhang among an inclusive (non-segmented) and Asian-identified (Asian-segmented) population, using a flexible intramedullary-rod, posterior referencing method.

Methods

CT Scans from bilateral lower limbs of skeletally mature subjects (981 inclusive, 267 Asian-identified), without bone pathology were prospectively acquired. Bones were segmented and landmarks were modeled using a flexible intramedullary-rod, posterior referencing method. Femoral components were virtually positioned by aligning the lateral implant edge with the lateral bone edge, where the anterior flange meets the anterior chamfer. Medial and lateral component overhang was measured at three zones: (1) intersection of the anterior flange and anterior chamfer (medial only), (2) anterior chamfer mid-line, and (3) distal face mid-line. The central tendency of the samples was determined using the observed mean and median and the 95% confidence interval.

INTRODUCTION

Preoperative planning software for anatomic total shoulder arthroplasty (ATSA) allows surgeons to virtually perform a reconstruction based off 3D models generated from CT scans of the glenohumeral joint. The purpose of this study was to examine the distribution of chosen glenoid implant as a function of glenoid wear severity, and to evaluate the inter-surgeon variability of optimal glenoid component placement in ATSA.

METHODS

CT scans from 45 patients with glenohumeral arthritis were planned by 8 fellowship trained shoulder arthroplasty specialists using a 3D preoperative planning software, planning each case for optimal implant selection and placement. The software provided three implant types: a standard non-augmented glenoid component, and an 8° and 16° posterior augment wedge glenoid component. The software interface allowed the surgeons to control version, inclination, rotation, depth, anterior- posterior and superior-inferior position of the glenoid components in 1mm and 1° increments, which were recorded and compared for final implant position in each case.

INTRODUCTION

Preoperative planning software for reverse total shoulder arthroplasty (RTSA) allows surgeons to virtually perform a reconstruction based off 3D models generated from CT scans of the glenohumeral joint. While anatomical studies have defined the range of normal values for glenoid version and inclination, there is no clear consensus on glenoid component selection and position for RTSA. The purpose of this study was to examine the distribution of chosen glenoid implant as a function of glenoid wear severity, and to evaluate the inter-surgeon variability of optimal glenoid component placement in RTSA.

METHODS

CT scans from 45 patients with glenohumeral arthritis were planned by 8 fellowship trained shoulder arthroplasty specialists using a 3D preoperative planning software, planning each case for optimal implant selection and placement. The software provided four glenoid baseplate implant types: a standard non-augmented component, an 8° posterior augment wedged component, a 10° superior augment wedged component, and a combined 8° posterior and 10° superior wedged augment component. The software interface allowed the surgeons to control version, inclination, rotation, depth, anterior-posterior and superior-inferior position of the glenoid components in 1mm and 1° increments, which were recorded and compared for final implant position in each case.

Introduction

There are over ½ million total knee replacement (TKR) procedures performed each year in the United States and is projected to increase to over 3.48 million by 2030. Concurrent with the increase in TKR procedures is a trend of younger patients receiving knee implants (under the age of 65). These younger patients are known to have a 5% lower implant survival rate at 8 years post-op compared to older patients (65+ years), and they are also known to live more active lifestyles that place higher demands on the durability and functional performance of the TKR device. Conventional TKR designs increase articular conformity to increase stability, but these articular constraints decrease patient range of knee motion, often limiting key measures of femoral rollback, A/P motion, and deep knee flexion. Without this articular constraint however, many patients report TKR “instability” during activities such as walking and stair descent, which can significantly impede confidence of movement. Therefore, there is a need for a TKR system that can offer enhanced stability while also maintaining active ranges of motion.

Materials and Methods

A novel knee arthroplasty system has been designed that uses synthetic ligament systems that can be surgically replaced, to provide ligamentous stability and natural motion to increase the functional performance of the implant. A computational anatomical model (AnyBody) was developed that incorporated ligaments into an existing Journey II TKR. Ligaments were modeled and given biomechanical properties from literature. Simulated A/P drawer tests and knee flexion were analyzed for 2,916 possible cruciate ligament location and length combinations to determine the effects on the A/P stability of the TKR. A physical model was then constructed, and the design was verified by performing 110 N A/P drawer tests under 710 N of simulated body weight.

Introduction

While manual total knee arthroplasty (MTKA) procedures have demonstrated excellent clinical success, occasionally intraoperative damage to soft tissues can occur. Robotic-arm assisted technology is designed to constrain a sawblade in a haptic zone to help ensure that only the desired bone cuts are made. The objective of this cadaver study was to quantify the extent of soft tissue damage sustained during TKA through a robotic-arm assisted (RATKA) haptically guided approach and conventional MTKA approach.

Methods

Four surgeons each prepared six cadaveric legs for CR TKA: 3 MTKA and 3 RATKA, for a total of 12 RATKA and 12 MTKA knees. With the assistance of an arthroscope, two independent surgeons graded the damage of 14 knee structures: dMCL, sMCL, posterior oblique ligament (POL), semi-membranosus muscle tendon (SMT), gastrocnemius muscle medial head (GMM), PCL, ITB, lateral retinacular (LR), LCL, popliteus tendon, gastrocnemius muscle lateral head (GML), patellar ligament, quadriceps tendon (QT), and extensor mechanism (EM). Damage was defined as tissue fibers that were visibly torn, cut, frayed, or macerated. Percent damage was averaged between evaluators, and grades were assigned: Grade 1) complete soft tissue preservation to ≤5% damage; Grade 2) 6 to 25% damage; Grade 3) 26 to 75% damage; and Grade 4) 76 to 100% damage. A Wilcoxon Signed Rank Test was used for statistical comparisons. A p-value <0.05 was considered statistically significant.

Background

Clinical and anatomical complications from total knee replacement (TKR) procedures are debilitating, and include weakness, damage, and the loss of native anatomy. As the annual number of primary TKR surgeries in the United States has continued to rise, to a projected 3.48 million in 2030, there has been a concomitant rise in revision surgery. Damage to or loss of native knee anatomy as a result of TKR revision can leave the patient with irreversible knee dysfunction, which is a contra-indication for most TKR systems on the market. This leaves the multi-revision patient with limited medical options. Complete fusion of the joint, known as arthrodesis, is indicated in some cases. Arthrodesis is also commonly indicated for traumatic injury, bone loss, quadriceps extensor mechanism damage, and osteosarcoma. While this treatment may resolve pain and allow a patient to walk, the inability to flex the knee results in considerable functional complications. Patients with arthrodesis are unable to drive, sit in close-quarter spaces, or engage in a significant number of activities of daily living.

Product Statement

The authors have developed and patented the Engage Knee System, a novel TKR system that allows a patient to lock and unlock the knee joint by means of a handheld, non-invasive device. An internal locking mechanism is constructed of materials that have been used in orthopedic joint replacements that have been approved through the FDA 510(k) process. A lightweight, handheld magnetic device is used to actuate the locking mechanism. No percutaneous components are required or present. This device allows a patient to lock their knee joint in full extension to ambulate with the functional equivalence of an arthrodesis, but allows a patient to unlock the device and bend the knee to engage in passive activities that would be otherwise difficult or impossible. The IP portfolio for this technology is owned by Clemson University, and they are seeking a partner/licensee to pursue further technology development and validation.

Introduction

While advances in joint-replacement technology have made total ankle arthroplasty a viable treatment for end-stage arthritis, revision rates for ankle replacements are higher than in hip or knee replacements [1]. The questions asked in this study were (1) what retrieved ankle devices demonstrate about ankle arthroplasty failures, and (2) how do these failures compare to those seen in the hip and the knee?

Materials and Methods

An IRB-approved retrieval laboratory received retrieved polyethylene inserts and surgeon-supplied reason for revision from 70 total-ankles (7 designs, including five currently-marketed designs) from 2002 to the present. All retrievals were rated for clinical damage. Polyethylene inserts received six months or less after retrieval (n=45) were analyzed for oxidation using Fourier Transform Infrared (FTIR) spectroscopy, reported as maximum ketone oxidation index [2]. Insert sterilization method was verified using trans-vinylene index [3]. Oxidation measured in the 45 ankle inserts versus their time in vivo was compared to oxidation rates previously published for gamma-sterilized hip and knee polyethylene retrievals [6]. Statistical analysis was performed using IBM SPSS v.22.

Aims

The aim of this study was to optimize screw hole placement in an acetabulum cup implant to improve secondary initial fixation by identifying the region of thickest acetabulum bone. The “scratch fit” of modern acetabular cup implants with highly porous coatings is often adequate for initial fixation in primary total hip arthroplasty. Initial fixation must limit micromotion to acceptable levels to facilitate osseointegration and long term cup stability. Secondary initial fixation can be required in cases with poor bone quality or bone loss and is commonly achieved with bone screws and a cup implant with multiple screw holes. To provide maximum secondary initial fixation, the cup screw holes should be positioned to allow access to the limited region of thick pelvic bone.

Patients and Methods

Through a partnership with Materialise, a statistical shape model of the pelvis was created utilizing 80 CT scans (36 female, 44 male). To limit the effect of variation outside the area of cup implant fixation, the shape model includes only the inferior pelvis (cut off at the greater sciatic notch and above the anterior inferior iliac spine).

A virtual implantation protocol was developed which creates instances of the pelvis shape model that accurately simulate the intraoperative reaming of the acetabulum to accept the cup implant. First a sphere is best fit to the native acetabulum and the diameter is rounded to the nearest whole millimeter. The diameter of the best fit sphere is increased by 1mm to simulate bone removal during the spherical reaming procedure. The sphere is translated medially and superiorly such that it is tangent to the teardrop and removes 2mm of superior acetabulum. The sphere is used to perform a Boolean subtraction from the shape model to create a virtually reamed pelvis shape model.

The Materialise 3-Matic software was used to perform a thickness analysis of the prepared shape models. The output of the thickness analysis is displayed as a color “heat map” where green represents thin bone and red is thick bone. The region of thickest bone was identified and used to drive ideal screw hole placement in the cup implant to access this region.

Introduction

Wear of polyethylene tibial inserts has been cited as being responsible for up to 25% of revision surgeries, imposing a very significant cost burden on the health care system and increasing patient risk. Accurate measurement of material loss from retrieved knee bearings presents difficult challenges because gravimetric methods are not useful with retrievals and unworn reference dimensions are often unavailable. Geometry and the local anatomy restrict in vivo radiographic wear analysis, and no large-scale analyses have illuminated long-term comparative wear rates and their dependence on design and patient factors. Our study of a large retrieval archive of knee inserts indicates that abrasive/adhesive wear of polyethylene inserts, both on the articular surface and on the backside of modular knees is an important contributor to wear, generation of debris and integrity of locking geometry.

The objective of the current study is to quantify wear performance of tibial inserts in a large archive of retrieved knees of different designs. By assessing wear in a large and diverse series, the goal is to discern the effect on wear performance of a number of different factors: patient factors that might help guide treatment, knee design factors and bearing material factors that may inform a surgeon's choice from among the array of arthroplasty device options.

Methods

An IRB approved retrieval database was queried for TKA designs implanted between 1997 and 2017. 1385 devices from 5 TKA designs were evaluated. Damage was ranked according to Hood's method, oxidation was determined through FTIR, and wear was determined through direct measurement of retrieved inserts using a previously established protocol. Design features (e.g. materials, conformity, locking mechanisms, stabilization, etc.) and patient demographics (e.g. age, weight, BMI, etc.) were cataloged. Multivariate analysis was performed to isolate factors contributing to wear, oxidation, and damage.

INTRODUCTION

Wedge femoral stems used in total hip arthroplasty (THA) have evolved with modifications including shorter lengths, reduced distal geometries, and modular necks. Unlike fit and fill stems which contact most of the metaphysis, tapered wedge femoral stems are designed to achieve proximal medial/lateral fixation. These single taper, wedge stems have demonstrated positive clinical outcomes. The tapered wedge stem evaluated in this study has further reduced distal geometry to provide a wedge-fit within the metaphysis of the proximal femoral canal for all femur types (Dorr A, B, C). The objective of this study was to evaluate the early clinical outcomes, including femoral stem subsidence, of a tapered wedge femoral stem.

METHODS

Fifty subjects (28 males, 22 females; mean age: 64.7±9.7 years; mean BMI: 29.6±4.6) underwent primary THA with a tapered wedge femoral stem. IRB approval was received prior to conducting the study and all participants signed the informed consent. Clinical data outcomes for this study included the Harris Hip Score (HHS), the Oxford Hip Score (OHS), revisions, and subsidence at the 6-week, 3-month, 1-year, and 2-year post-operative time points. Femoral stem subsidence was measured by an independent third party. Student t-tests were used to identify significant mean differences between genders (p<0.05).

INTRODUCTION

Loosening is concerned to be the major cause of revision in the artificial prosthesis. Wear debris of UHMWPE dispersed into the implant-bone interface are phagocytosed by macrophages releasing inflammatory cytokines such as TNF-α which leads to osteolysis and loosening eventually. It is known that the size and structure [1] as well as attached substances on particle surface such as endotoxin could affect the amount of cytokines released [2]. An in vivo study using rat femurs showed that the presence of polyethylene particles around implants could result in accumulation of lipopolysaccharide (LPS) from exogenous sources that may affect bone remodeling around implants [3]. It is also reported that LPS is transported throughout the body with lipoproteins or LPS binding proteins [4] and Circulating LPS may originate from local sites of infection or via bloodborne bacteria [5]. In this study, we evaluated the effects of LPS that attached to UHMWPE particle surface by measuring TNF-α released from macrophages.

MATERIALS AND METHODS

We cultured mouse macrophage cell line RAW 264 with spherical UHMWPE particles (8.7µm and 23µm diameter in average, Mitsui chemicals Co., LTD.) and LDPE particles (3.6µm and 5.8µm diameter in average, Sumitomo Seika Chemicals Co., LTD.) using the Inverse Culture Method for 24 hours before estimating the TNF-α generation by TNF- ALPHA QUANTIKINE ELISA KIT (R&D). Spherical UHMWPE particles (10µm diameter in average, Mitsui chemicals Co., LTD.) with E.coli original LPS (Enzo Life Sciences) attached to them were incubated with cells to see the effects of LPS on the bio-reactivity tests.

Objectives

Total hip arthroplasty (THA) is one of the most successful surgical procedures; several bearing technologies have been used, however none of these is optimal. Metal on polycarbonate-urethane (PCU) is a new bearing technology with several potential advantages: PCU is a hydrophilic soft pliable implant quite similar in elasticity to human cartilage, offers biostability, high resistance to hydrolysis, oxidation, and calcification, no biodegradation, low wear rate and high corrosion resistance and can be coupled with large metal heads (Tribofit Hip System, THS).

The aim of this prospective study was to report the survivorship and the clinical and radiographic outcomes and the metal ions dosage of a group of patients operated with metal on PCU arthroplasty featuring large metal diameter heads, at 5 years from surgery.

Study Design & Methods

68 consecutive patients treated with the THS were included. The patients have been contacted by phone call and invited to return to our centre for clinical (Oxford Hip Score, OHS, and Harris Hip Score, HHS), radiographic exam and metal ion levels evaluation. All the patients were operated with uncemented stems.

Introduction

Total hip replacement (THR) patients are often considered a homogenous group whereas in reality, patients are heterogeneous. Variation in revision rates between patient groups suggest that implants are exposed to different environmental conditions in different patients [1]. Previous reports suggest that for every unit increase of BMI, there is a 2% increased risk of revision of a THR [2]. The aim of this study was to better understand the effect of patient-specific characteristics such as BMI on hip motions and to explore the possible impact on wear.

Methods

137 THR patients, at least 12 months post-surgery, underwent 3D kinematic (Vicon, Oxford, UK) and kinetic (AMTI, USA) analysis whilst walking at self-selected walking speed. 3D kinematic data were then mapped onto a modelled femoral cup at 20 pre-determined points to create pathways for femoral head contact, which were then quantified by deriving the aspect ratio (AR). Patients were stratified into three groups determined by BMI scores; healthy weight (BMI ≤25 kg/m²) (n=34); overweight (BMI >25kg/m² to ≤ 30 kg/m²) (n=66) and obese patients (BMI > 30 kg/m²) (n=37). Comparisons were made using 95% confidence intervals (CI) and one way ANOVAs.

Introduction

One of the known mechanisms which could contribute to the failure of total hip replacements (THR) is edge contact. Failures associated with edge contact include rim damage and lysis due to altered loading and torques. Recent study on four THR patients showed that the inclusion of pelvic motions in a contact model increased the risk of edge contact in some patients. The aim of current study was to determine whether pelvic motions have the same effect on contact location for a larger patient cohort and determine the contribution of each of the pelvic rotations to this effect.

Methods

Gait data was acquired from five male and five female unilateral THR patients using a ten camera Vicon system (Oxford Metrics, UK) interfaced with twin force plates (AMTI) and using a CAST marker set. All patients had good surgical outcomes, confirmed by patient-reported outcomes and were considered well-functioning, based on elective walking speed. Joint contact forces and pelvic motions were obtained from the AnyBody modelling system (AnyBody Technologies, DK). Only gait cycle regions with available force plate data were considered. A finite element model of a 32mm head on a featureless hemispherical polyethylene cup, 0.5mm radial clearance, was used to obtain the contact area from the contact force. A bespoke computational tool was used to analyse patients' gait profiles with and without pelvic motions. The risk of edge contact was measured as a “centre proximity angle” between the cup pole and centre of the contact area, and “edge proximity angle” between the cup pole and the furthest contact area point away from the pole. Pelvic tilt, drop and internal-external rotation were considered one at a time and in combinations.

INTRODUCTION

In gap balancing technique, we decided the femoral component rotation according to the ligament balance in flexion. Component and limb alignment are important considerations during TKA. Three-dimensional positioning of TKA implants and exact mechanical axis has an effect on implant loosening, polyethylene stresses, and gait.

According to the recent report, the navigation system made it possible to achieve aligned implants more than conventional TKA. Hybrid Navigation technique which is our procedure is combination of navigation system and modified gap technique. In other words, exact mechanical axis is gained by navigation system, stable stability of knee joint is gained by modified gap technique.

PURPOSE

The purpose of this study is to carry out clinical evaluation and image evaluation of the patients who underwent hybrid navigation technique TKA.

Introduction

Reverse Shoulder Arthroplasty (RSA) is recognized to be an effective solution for rotator cuff deficient arthritic shoulders, but there are still concerns about impingement and range of motion (ROM). Several RSA biomechanical studies have shown that humeral lateralization can increase ROM in planar motions (e.g. abduction). However, there is still a debate whether humeral lateralization should be achieved with a larger sphere diameter or by lateralizing the center of rotation (COR). The latter has shown to decrease the deltoid moment arm and increase shear forces, where the former may pose challenges in implanting the device in small patients. The aim of this study was to evaluate how humeral lateralization achieved by varying COR lateral offset and glenosphere diameter in a reverse implant can affect impingement during activities of daily living (ADLs).

Methods

Nine shoulder CT scans were obtained from healthy subjects. A reverse SMR implant (LimaCorporate, IT) was virtually implanted on the glenoid and humerus (neck-shaft angle 150°) as per surgical technique using Mimics software (Materialise NV). Implant positioning was assessed and approved by a senior surgeon. The 3D models were imported into a validated shoulder computational model (Newcastle Shoulder Model) to study the effects of humeral lateralization. The main design parameters considered were glenosphere diameter (concentric Ø36mm, Ø40mm, Ø44mm) and COR offset (standard, +2mm, +5mm), for a total of 9 combinations for each subject; −10°, 0° and 10° humeral components versions were analyzed. The model calculated the percentage of impingement (intra-articular, contact of cup with scapula neck and glenoid border; extra-articular, contact of humerus with acromion and coracoid) during 5 ADLs (hand to opposite shoulder, hand to back of head, hand to mouth, drink from mug and place object to head height).

Introduction

The number of young and more active patients requiring total knee replacement (TKR) is increasing. Preclinical evaluation and understanding the long-term failure of TKR is therefore important. Preclinical wear simulation of TKR is usually performed according to the International Standards Organization (ISO) recommendations. Two international standards for preclinical wear simulation of TKRs have been developed so that the anterior-posterior (AP) translation and internal-external (IE) rotation can be driven in either force or displacement control. However, the effects of using different control regimes on the kinematics and wear of the same TKR have not been investigated. The current study investigated the kinematics, contact mechanics and wear performance of a TKR when running under ISO force and displacement control standards using an experimentally validated computational model.

Materials/Methods

Three different ISO control standards were investigated using a size C Sigma curved TKR (DePuy, UK), with moderately cross-linked UHMWPE curved inserts; ISO-14243-3-2004, ISO-14243-3-2014 and ISO- 14243-1-2009. Axial force and flexion-extension angle are common for the three standards. AP and IE motions are displacement controlled in ISO-14243-3-2004 and ISO-14243-3-2014, with the only difference being a reversal of AP polarity between the two standards, and are force controlled in ISO-14243-1-2009. The test setup and soft tissue constraints were defined in accordance with ISO recommendations. The wear model was based on the modification of Archard's law where the wear volume is defined as a function of contact area, sliding distance, cross-shear and contact stress. The simulation framework has been independently validated against experimental wear rates under three different standard and highly demanding daily activities (Abdelgaied et al. 2018).

Introduction

Modified gap technique has been reported to be beneficial for the intraoperative soft tissue balancing in posterior-stabilized (PS) -TKA. We have found intraoperative ligament balance changed depending on joint distraction force, which might be controlled according to surgeons' fells.

We have developed a new surgical concept named as “medial preserving gap technique (MPGT)” to preserve medial knee stability and provide quantitative surgical technique according to soft tissue balance measurement using a tensor device.

The purpose of this study was to compare 3-years postoperative knee stability after PS-TKA in varus type osteoarthritic (OA) knees between MPGT and measured resection technique (MRT).

Material & Method

The subjects were 94 patients underwent primary unilateral PS-TKA for varus type OA knees. The surgical technique was MPGT in 47 patients and MRT in 47 patients.

An originally developed off-set type tensor device was used to evaluate intraoperative soft tissue balance. In MPGT, medial release was limited until the spacer block corresponding to the bone thickness from proximal lateral tibial plateau could be easily inserted. Femoral component size and external rotation angle were adjusted depending on the differences of center gaps and varus angles between extension and flexion before posterior femoral condylar resection.

The knee stabilities at extension and flexion were assessed by stress radiographies at 1 and 3 years after TKA; varus-valgus stress test at extension and stress epicondylar view at flexion. We measured medial and lateral joint openings (MJO, LJO) at both knee extension and flexion.

MJOs and LJOs at 2 time periods were compared in each group using paired t-test. Each joint opening distance was compared between 2 groups using unpaired t-test. The significance level was set as P < 0.05.

BACKGROUND

Telerehabilitation has been shown to both promote effective recovery after shoulder arthroplasty and may improve adherence to treatment. Such systems require demonstration of feasibility, ease of use, efficacy, patient and clinician satisfaction, and overall cost of care, and much of this data has yet to be provided. Few augmented reality rehabilitation approaches have been developed to date. Evidence suggests augmented reality rehabilitation may be equivalent to conventional methods for adherence, improvement of function, and relief of pain seen in these musculoskeletal conditions. We proposed that the development of an augmented reality rehabilitation platform during the pre and postoperative period (including post-shoulder arthroplasty) could be used to track patient activity and range of motion as well as promote recovery.

METHODS

A prototype augmented reality platform equipped with a motion sensor system optimised for the upper arm was developed to be used to validate 4 arcs of shoulder motion and complete directed upper arm exercises designed for post-shoulder arthroplasty rehabilitation was built and tested. This system combined augmented reality instructions and motion tracking to follow patients over the course of their therapy, along with a telehealth patient-clinician interface.

BACKGROUND

The obesity crisis in the United States has caused a significant increase of hip arthritis. Surgical complication rates are higher in this population and guidelines are being used to select patients who are acceptable candidates for surgical intervention. This retrospective study evaluated the complication rates for obese patients undergoing total hip replacement compared to non-obese patients as defined by the World Health Organization (WHO). Additionally, we compared complication rates of the direct anterior approach (ATHA) versus the posterior approach (PTHA) in a consecutive group of patients using similar protocols.

METHODS

This study is an IRB approved retrospective review of 210 patients undergoing ATHA and 201 patients undergoing PTHA during the same time period by 2 experienced, high-volume total joint surgeons. Non-obese patients were compared to obese patients using WHO body mass index (BMI) classification. Minor and major complications were reviewed as well as surgical time, length of stay, disposition, and short-term outcome measures (including pain scores, narcotic use, and assistive device use).

Background

The posterior slope of the tibial component in total knee arthroplasty (TKA) has been reported to vary widely even with computer assisted surgery. In the present study, we analyzed the influence of posterior tibial slope on one-year postoperative clinical outcome after posterior-stabilized (PS) -TKA to find out the optimal posterior slope of tibial component.

Materials and Method

Seventy-three patients with varus type osteoarthritic (OA) knees underwent PS-TKA (Persona PS^R) were involved in this study. The mean age was 76.6 years old and preoperative HKA angle was 14.3 degrees in varus. Tibial bone cut was performed using standard extra-medullary guide with 7 degrees of posterior slope.

The tibial slopes were radiographically measured by post-operative lateral radiograph with posterior inclination in plus value. The angle between the perpendicular line of the proximal fibular shaft axis and the line drawn along the superior margin of the proximal tibia represented the tibial slope angle. We assessed one-year postoperative clinical outcomes including active range of motion (ROM), patient satisfaction and symptoms scores using 2011 Knee Society Score (2011 KSS).

The influences of posterior tibial slope on one-year postoperative parameters were analyzed using simple linear regression analysis (p<0.05).

Introduction

The use of Additive Manufacturing (AM) to 3D print titanium implants is becoming widespread in orthopaedics, particularly in producing cementless porous acetabular components that are either custom-made or off-the-shelf; the primary design rationale for this is enhanced bony fixation by matching the porosity of bone. Analysis of these retrieved components can help us understand their performance; in this study we introduce a non-destructive method of the retrieval analysis of 3D printed implants.

Material and methods

We examined 11 retrieved 3D printed acetabular cups divided into two groups: “custom-made” (n = 4) and “off-the-shelf” (n = 7). A macroscopic visual analysis was initially performed to measure the area of tissue ongrowth. High resolution imaging of each component was captured using a micro-CT scanner and 3D reconstructed models were used to assess clinically relevant morphometric features of the porous structure: porosity, porous structure thickness, pore size and strut thickness. Optical microscopy was also used as a comparison with microCT results. Surface morphology and elemental composition of the implants were investigated with a Scanning Electron Microscope (SEM) coupled with an Energy Dispersive X-ray Spectroscope (EDS). Statistical analysis was performed to evaluate possible differences between the two groups.

Background

In the late 1980's Michael Freeman conceived the idea that knee replacement would most closely replicate the natural knee joint, if the medial Tibio-Femoral articulation was configured as a “ball-in-socket”. Over the last three decades, medial rotation and medial pivot designs have proved successful in clinical use. Freeman's final iteration of the medial ball-in-socket concept was the Medial Sphere knee. We report the three-year survivorship, clinical outcomes, patient reported outcome measures (PROMs) and radiographic analysis of this implant in a multi-centre, multi-surgeon, prospective observational study.

Methods

Patients awaiting total knee replacement were recruited by four centres. They had no medical contraindication to surgery, were able to provide informed consent and were available for follow-up. Primary outcome was implant survival at six months, one, two, three and five years. Secondary outcomes were patient reported outcome measures: Oxford Knee Score (OKS), Euroqol (EQ-5D), International Knee Society Score (IKSS), IKSS Functional score and Health State score, complications and radiographic outcomes. Radiographic analysis was undertaken using the TraumaCad software and data analysis was undertaken using SPSS.

Background

The cruciate ligaments are important structures for biomechanical stability of the knee. For total knee arthroplasty (TKA), understanding of the exact function of the (PCL) and anterior (ACL) cruciate ligament during walking is important in the light of recent designs of bicruciate TKAs. However, studies evaluating in vivo function of the PCL during daily activities such as walking are scarce. We aimed to assess the role of the PCL during gait by measuring kinematics and kinetics of individuals with PCL deficiency and compare them with individuals with ACL deficiency and healthy young adults.

Methods

Individuals with unilateral PCL deficiency (PCLD; n=9), unilateral ACL deficiency (n=10) and healthy young adults performed (n=10) 10 walk trials (5 for each leg) in which they walked over a force platform. Motion analysis (Vicon Motion Capture System) was used to calculate joint angles and internal moments around the knee, hip and ankle in the sagittal plane. Joint angles and moments of the injured knee (in PCLD and ACLD) or left knee (in HYA) were compared between groups at weight acceptance, mid-stance and push-off phases (see Fig. 1). Clinical assessment included passive knee laxity (Kneelax) for anterior (in 20–30° knee flexion) and posterior tibia translation (in 70–90° knee flexion) and Lysholm questionnaires.

Introduction

Little is known about the relationship between head-neck corrosion and its effect on periprosthetic tissues and distant organs in the majority of patients hosting apparently well-functioning devices. We studied the degree and type of taper damage and the histopathologic response in periprosthetic tissue and distant organs.

Methods

A total of 50 contemporary THRs (34 primary, 16 revision) retrieved postmortem from 40 patients after 0.4–26 years were studied. Forty-three femoral stems were CoCrMo and 7 were Ti6Al4V. In every case, a CoCrMo-alloy head articulated against a cementless polyethylene cup (19 XLPE and 31 UHMWPE). H&E and IHC sections of the joint pseudocapsules and liver were graded 1–4 for the intensity of various inflammatory cell infiltrates and tissue necrosis. The nature of the tissue response in the joint capsule, liver, spleen, kidneys and lymph nodes was assessed. Wear and corrosion products in the tissues were identified using SEM and EDS. Taper surfaces were graded for corrosion damage using modified Goldberg scoring and examined by SEM to determine the acting corrosion mode. Correlations between damage scores and the histologic variables were generated using the Spearman test.

Introduction

PEEK-OPTIMA™ has been considered as an alternative to cobalt chrome in the femoral component of total knee replacements. Whole joint wear simulation studies of both the tibiofemoral and patellofemoral joints carried out to date have shown an equivalent wear rate of UHMWPE tibial and patella components against PEEK and cobalt chrome (CoCr) femoral components. In this study, the influence of third body wear on UHMWPE-on-PEEK was investigated, tests on UHMWPE-on-CoCr were carried out in parallel to compare PEEK to a conventional femoral component material.

Methods

Wear simulation was carried out in simple geometry using a 6-station multi-directional pin-on-plate simulator. 5 scratches were created on each PEEK and CoCr plate perpendicular to the direction of the wear test using a diamond stylus to produce scratches with a geometry similar to that observed in retrieved CoCr femoral components. To investigate the influence of scratch lip height on wear, scratches of approximately 1, 2 and 4µm lip height were created. Wear simulation of GUR 1020 UHMWPE pins (conventional, non-sterile) against the plates was carried out for 1 million cycles (MC) using 17g/l bovine serum as a lubricant using kinematic conditions to replicate the average contact pressure and cross-shear in a total knee replacement. Wear of UHMWPE pins was measured gravimetrically and the surface topography of the plates assessed using a contacting Form Talysurf. Wear factors of the pins against the scratched plates were compared to unscratched controls (0µm lip height). Minimum n=3 for each condition and statistical analysis carried out using ANOVA with significance taken at p<0.05.

INTRODUCTION

Postoperative functional limitations after Total Knee Arthroplasty (TKA) are caused, in part, by a mismatch between a patient's natural anatomy and conventional “off-the-shelf” implants. To address this, we propose a new concept combining off-the-shelf femur and tibia implants with custom polyethylene tibial inserts designed to account for a patient's unique anatomy. Our goal in this study was to use knee specific computational modeling to determine the neutral path of motion and laxity of an intact knee under axial compression and shear forces through full flexion and compare intact motion against the same knee implanted with a conventional off-the-shelf vs. a custom tibial insert.

METHODS

3D models of a healthy knee joint were acquired from an open development repository funded by the National Institute of Biomedical Imagining and Bioengineering (Harris et al., 2016). The knee model was virtually implanted with conventional (off-the-shelf) posterior cruciate retaining (CR) components including the femoral component, tibial tray, and a conventional insert. A custom CR tibial insert was designed taking into account native articular geometry and compatibility with placement of the off-the-shelf femoral/tibial tray. Bone, cartilage and implant models were imported into ANSYS Workbench. Ligaments were calibrated using data from in-vitro experimental tests (Harris et al., 2016). The following load conditions were applied to the femur: 20 N axial compression (neutral path), 20 N axial compression with 80 N anterior shear force, and 20 N axial compression with 80 N posterior shear force. Simultaneously for each loading condition, the knee was flexed from 0 – 120 degrees. A circular axis system was used to describe the motion of the femur relative to the tibia.

Background

Acromegaly, which stems from high level of serum growth hormone secreted by a benign tumour in the anterior pituitary gland, is likely to cause severe peripheral joint pains due to hypertrophic changes in such joints. Recently, the life expectancy of such patients has been improved and more patients with acromegaly have undergone joint surgeries to mitigate joint pain and malfunctions. However, little is known about to what extent surgical procedures can improve the joint functions of acromegalic patients compared to non-acromegalic cases.

Methods

First, we qualitatively analysed prognosis of total hip arthroplasty (THA) of acromegalic patients by investigating 11 cases in which direct anterior approach (DAA) THAs were performed to 8 acromegalic patients in our hospital between 2012 and 2015.

Second, we quantitatively compared the functional prognosis of the 11 cases with that of 107 non-acromegalic cases. Technically, to control the difference in age, sex, height, and weight between the two patient groups, we first identified a model that could predict 3month-/6month-/12month-functional prognosis in the control cases. We estimated differences in functional outcomes between the two groups by calculating how accurately the control-case-based model could predict the prognosis of the acromegalic cases.

Introduction

Aseptic loosening is the main reason for total knee arthroplasty (TKA) failure, responsible for more than 25% of the revision procedures, with most of the problems occurring with the tibial component. While early loosening can be attributed to failure of primary fixation, late implant loosening is associated with loss of fixation secondary to bone resorption due to altered physiological load transfer to the tibial bone. Several attempts have been made to investigate these changes in bone load transfer in biomechanical simulations and bone remodeling analyses, which can be useful to provide information on the effect of patient, surgery, or design-related factors. On the other hand, these factors have also been investigated in clinical studies of radiographic changes of bone density following TKA. In this study we made an overview of the knowledge obtained from these clinical studies, which can be used to inform clinical decision making and implant design choices.

Methods

A literature search was performed to identify clinical follow-up studies that monitored peri-prosthetic bone changes following TKA. Within these studies, effects of the following parameters on bone density changes were investigated: post-operative time, region of interest, alignment, body weight, systemic osteoporosis, implant design and cementation.

Moreover, we investigated the effect of bone density loss on implant survival. Results

A total of 19 studies was included in this overview, with a number of included patients ranging from 12 to 7,760. Most studies used DEXA (n=16), while a few studies performed analyses on calibrated digital radiographs (n=2), or computed tomography (n=1). Postoperative follow-up varied from 9 months to 10 years.

Studies consistently report the largest bone density reduction within the first postoperative year. Bone loss is mainly seen in the medial region. This has been attributed to the change in alignment following surgery, during which often the pre-operative varus knee is corrected to a more physiological alignment, resulting in a load shift towards the lateral compartment. Measurements in unoperated contralateral legs were performed in 3 cases, and two studies performed standardized DEXA measurements to provide information on systemic osteoporosis. While on the short term no changes were observed, significant negative correlations have been found between severity of osteoporosis and peri-prosthetic bone density. No clear effects of bodyweight and cementation on bone loss have been identified. Although some studies do find differences between implant types, the variation in the data makes it difficult to draw general conclusions from these findings.

Several studies reported no effect of bone loss on implant migration. In another study, a medial collapse was associated with a medial increase in density, suggesting that altered loading and increased stresses are responsible for both bone formation and the overload leading to collapse.

INTRODUCTION

Additive manufacturing (3D printing) is used to create porous surfaces that promote bone ingrowth in an effort to improve initial stability and optimize long-term biological fixation. The acetabular cup that was studied is manufactured with titanium alloy powder via electron beam melting. Electron beam melting integrates the porous and solid substrate rather than sintering a porous coating to a solid surface. The 3D-printed acetabular cup's high surface coefficient of friction (up to 1.2), combined with its geometry, creates a predictable press-fit in the acetabulum, improving initial mechanical stability and ultimately leading to reproducible biologic fixation. The objective of this study was to evaluate the early clinical outcomes and implant fixation of this 3D-printed acetabular cup in total hip arthroplasty (THA).

METHODS

Four hundred twenty-eight subjects from 8 US and international research sites underwent primary THA with the 3D-printed acetabular cup. All sites received IRB approval prior to conducting the study, and all participants signed the informed consent. Screw usage and number used during surgery were used as a surrogate measurement for initial implant fixation. Clinical performance outcomes included pre- and post-operative Harris Hip Scores (HHS) and Oxford Hip Scores (OHS), patient satisfaction, and revision assessment. 215 patients had a minimum 1-year post-operative follow-up visit.

Student t-tests were used to identify significant mean differences (p<0.05).

Purpose

Total knee replacement is the one of the most performed surgeries. However, patient's satisfaction rate is around 70–90 % only. The sacrifice of cruciate ligament might be the main reason, especially in young and active patients. ACL stabilizes the knee by countering the anterior displacing and pivoting force, absorbs the shock and provides proprioception of the knee. However, CR knees has been plagued by injury of PCL during the surgery and preservation of the ACL is a demanding technique. Stiffness is more common comparing to PS designed knee. To insert a tibial baseplate with PE is usually thicker than 8 mm comparing to 2–4 mm of removed tibial bone. The stuffing of joint space may put undue tension on preserved ACL and PCL. Modern designed BCR has been pushed onto market with more sophisticated design and instrumentation. However, early results showed high early loosening rate. Failure to bring the tibia forward during cementing may be the main cause. The bone island where ACL footprint locates is frequently weak, intraoperative fracture happens frequently. A new design was developed by controlled elevation and reattachment of the ACL footprint to meet all the challenges.

Method

A new tibial baseplate with a keel was designed. The central part of the baseplate accommodates elevated bony island with ACL footprint. The fenestrations at the central part is designed for reattachment of bony island under proper tension with heavy sutures and fixed at anterior edge of the baseplate in suture bridge fashion and also for autograft to promote bony healing after reattachment. The suture bridge method has been used by arthroscopists for ACL avulsion fracture without the need of immobilization. The elevation of bony island release the tension in the ACL which come from stuffing of baseplate and PE insert and greatly facilitate cementing of the baseplate. The keel improve the weakness of traditional U shape design of BCR knees.

Instead of keeping the bony island intact by separately cutting the medial and lateral tibial plateau in BCR knees in the past, we choose to saw the tibial plateau in one stroke as in PS knees, then removes the two condyles. The bony island includes the footprint both ACL and PCL. The central part of tibial baseplate will push the bony island upward which release the undue tension in the cruciate ligaments.

Introduction

The viscoelastic cervical disk prosthesis CP-ESP is an innovative one-piece deformable but cohesive interbody spacer. It is an evolution of the LP-ESP lumbar disk implanted since 2006. The implant provides 6 full degrees of freedom including shock absorption. The design allows a limitation for rotation and translation with resistance to motion (elastic return property) aimed at avoiding overload of the posterior facets. The rotation center can vary freely during motion. It thus differs substantially from current prostheses.

This study reports the clinical results of a prospective observational study series of 89 patients who are representative of the current use of the ESP implant since 2012.

The radiological results are focused on the evolution of the mean center of rotation (MCR) as an additional information to the range of motion (ROM) for the evaluation of the quality of spine movement.

Materials and Methods

89 patients (33 males, mean age 45 years [28–60], 107 implants) were included for an open, prospective and non-randomized study between October 2012 and December 2015.

One level patients were at C3C4 (3), C4C5 (3), C5C6 (41) C6C7 (24) C7T1 (1)

Two levels patients were C4C5/C5C6 (3), C5C6/C6C7 (12), C6C7/C7D1 (1) and 3 levels C4C5/C5C6/C6C7 (1)

Introduction

Hip resurfacing arthroplasty (HRA) is an alternative to traditional total hip arthroplasty (THA) in young active patients. While comparative implant survival rates are well documented, there is a paucity of studies reporting the patient mortality rates associated with these procedures. The purpose of this study was to evaluate the mortality rates in patients age 55 years and younger who underwent HRA versus THA and to assess whether the type of operation was independently associated with mortality.

Patients and Methods

The database of a single high-volume surgeon was reviewed for all consecutive patients age 55 years and younger who underwent hip arthroplasty between 2002 and 2010. HRA became available in the United States in 2006. This yielded 504 patients who had undergone HRA from 2006 to 2010 and 124 patients who had undergone a THA. Patient characteristics were collected from the electronic medical record including age, gender, body mass index, Charleston comorbidity index, smoking status, and primary diagnosis. Mortality was determined through a combination of electronic chart reviews, patient phone calls, and online obituary searches. Univariate analysis was performed to identify a survival difference between the two cohorts. Multivariable Cox-Regression analyses were used to determine whether the type of operation was independently associated with mortality.

Background

Tigecycline, the first member of glycylcycline family, has effective antimicrobial activity against resistant and implant associated infectious organisms. The objectives of this study are to assess the compressive and tensile mechanical strength characteristics of tigecycline loaded bone cement and to compare them with vancomycin and daptomycin loaded bone cements which are used in prosthetic joint infections with resistant microorganisms.

Methods

A control group without antibiotics and three antibiotic loaded bone cement groups with varying concentrations (1g, 2g and 3g vancomycin, 0.5g, 1g and 1.5g daptomycin and 50mg, 100mg and 150mg tigecycline) were prepared and tested according to ASTM F451 and ISO 5833 standards. Statistical analysis of the obtained data done by using LSD (least significant difference) and Bonferroni corrected Mann Whitney tests.

Background

Effectiveness of computer-assisted joint replacement (CA-TJR) compared to conventional TJR has been evaluated by a large body of literature. Systematic reviews provide a powerful, widely accepted, evidence-based approach to synthesize the evidence and derive conclusions, yet the strength of these conclusions is dependent on the quality of the review. Multiple systematic reviews compared CA-TJR and conventional TJR with conflicting results. We aimed to assess the quality of these reviews.

Methods

We searched MEDLINE, EMBASE, the Cochrane, and Epistemonikos to identify SRs published through May 2017. Full-text articles that met inclusion criteria were retrieved and assessed independently by two reviewers. Evidence was qualitatively synthesized and summarized. Outcome measures were categorized into functional, radiological, and patient safety related. The corrected covered area (CCA) was calculated to assess the degree of overlap between SRs in analyzing the same primary studies. The AMSTAR 2, a valid and reliable tool, was applied to rate the confidence in the results of the SRs (Shea et al., 2017). AMSTAR-2 has 16 domains, of which 7 are critical (e.g., justification for excluding individual studies) and 9 are non-critical (e.g., not reporting conflict of interest for individual studies). Reviews are rated as high (no critical or non-critical flaws), moderate (only non-critical flaws), low (1 critical flaw) and critically low (more than one critical flaw). Disagreement between the 2 reviewers was resolved by discussion with the senior author to achieve consensus. We reported the quality ratings of these studies and the frequency of critical and non-critical flaws.

Background

Revision total knee arthroplasties (rTKA) are performed with increasing frequency due to the increasing numbers of primary arthroplasties, but very little is known regarding the influence of muscle strength impairments on functional limitations in this population.

Objectives

The aim of this study was to assess relationship between muscle strength and functional level in patient with rTKA.

Introduction

A search of the literature indicates several constrained total knee arthroplasty (TKA) systems are at risk for articular surface lockdown bolts backing out. The backing out of a lockdown bolt may lead to an unstable and/or painful knee and may necessitate revision. Upon backing out, the bolt may damage implant components and surrounding tissues. To date, studies in the literature have not simulated or replicated loosening of bolts in TKA. Therefore, the objectives of this study were to 1) develop a set of physiological loading parameters that challenge bolted articular surfaces; 2) evaluate whether significant bolt torque is lost during application of this loading to a CCK device with a bolt as a secondary locking mechanism.

Materials and Methods

Physical test parameters to loosen lockdown bolts were developed based on loading experienced during activities of daily living. Sinusoidal waveforms and timing were used to simulate worst case walking gait conditions. Compared to data from everyday activities in instrumented TKR patients, anterior posterior loads and internal/external torques exceeding the absolute maximums observed were selected. To transfer more shear and torsion to the joint interface, compressive load lower than typically reported for walking gait was used. Frequency was representative of walking gait motion.

The offset in torsional waveform enables a ratcheting motion to drive a loose bolt out of the joint: during external femoral rotation of a left knee, reduced compressive load and posterior directed femoral loading on a CCK spine creates a potential articular surface lift-off. The lift-off may grab the underside of the front bolt shoulder while external (CCW) rotation loosens the bolt. These loading conditions exist during toe-off of walking gait. Two CCK devices were evaluated to capture potential difference in performance: a medium articular surface combination and a smaller articular surface combination. Testing was performed on a load frame capable of rotation and vertical / horizontal translation.

Background

Total knee arthroplasty (TKA) is offered to patients who have end-stage knee osteoarthritis to reduce pain and improve functional performance. Knee edema and pain deteriorate the patients' outcomes after TKA at early period. By quantifying the patients' early outcome deficits and their potential relationships to edema and pain may assist in the design of in-patient rehabilitation programs.

Objectives

The aim of this study was to investigate of the effect of knee swelling on early patients' outcomes after primary TKA.

Background

Kinesiophobia is simply defined as a fear of movement and physical activity. It can be seen in patients as a result of any injury, which results in pain or a fear of injury recurrence. It leads to decreased motion and disuse that may result in a chronic pain syndrome and decreased physical function. High levels of fear-avoidance have been found in subjects with total knee arthroplasty (TKA) and knee injuries, which predisposes them to the development of chronic pain conditions and seriously affect functional outcomes and their return to previous activity levels. However, the relationship between pain, kinesiophobia and performance-based outcomes in assessment of patients with TKA is unclear.

Purpose

The aim of our study was to investigate relationship between pain, kinesiophobia and performance-based tests in assessment of patients with TKA.

Introduction

Computer navigation is a highly sophisticated tool in orthopedic surgery for component placement in total hip arthroplasty (THA). A number of recommendations have been published. Although Lewinnek's safe-zone is the best-known among these its significance is questioned in recent years since it addresses the acetabular socket only ignoring the femoral stem. Modern target definitions consider both socket and stem and provide well-defined recommendations for complementary component positioning. We present a new small-sized hand-held imageless navigation system that implies these targets and supports the surgeon in realizing the concept of combined anteversion and combined Target-Zone (cTarget- Zone) in THA and to control leg length and offset without altering the standard surgical work-flow and we report initial results.

Methods

The targets for positioning the components of a total hip as expressed by radiographic cup inclination (cRI) and anteversion (cRA), stem antetorsion (sAT) and neck-to-shaft angle (sNSA) are determined for a specific prosthesis system using a computerized 3D-model. The optimizing goal is maximizing the size of the cSafe-Zone providing the largest target zone for an impingement-free prosthetic range of motion (pROM) in order to minimize the risk for dislocation in physiologic and combined movements. Independent parameters like head size, head-to-neck ration and also component orientations like cRI, cRA, sAT and sNSA were varied systematically and the optimal cSafe-Zone was computed in semi-automated batch runs. These optimized prosthesis-specific results were introduced into the software of the hand-held navigation system. This system measures leg length, offset, acetabular and femoral head centers intraoperatively.

INTRODUCTION

Since the early 2000s, highly cross-linked (HXL) UHMWPE's have become a popular option with multiple experimental and clinical studies showing that gamma or electron radiation doses between 50–100kGY reduce wear and potentially extend the bearing life of UHMWPE. However, the increased wear resistance came at a compromise to mechanical properties due to the cross-linking process. Vitamin E has been added to some HXL UHMWPE materials to offer a solution to the compromise by increasing oxidation resistance and maintaining sufficient fatigue strength. However, limited data is available on the effect of the fabrication process, especially the method of irradiation, on the properties of the Vitamin E blended HXL UHMWPE. The purpose of this study was to evaluate the effects of adding the antioxidant vitamin E to highly crosslinked UHMWPE on wear rates.

METHODS

Wear testing was performed on six highly crosslinked UHMWPE acetabular liners containing vitamin E (0.1% wt. alpha tocopherol) fabricated using the Cold Irradiation Mechanically Annealed (CIMA) process, initially cross-linked with approximately 100 kGy gamma irradiation, and terminally gamma sterilized. The liners were paired with three 40mm CoCr femoral heads and 40mm three ceramic femoral heads. Testing was completed per ASTM F1714 and ISO 14242 on an orbital hip joint wear simulator (Shore Western, California) and lubricated with 90% bovine calf serum, 20mM EDTA, 0.2% wt. NaN₃ and DI water. A 1.1Hz Paul-type loading waveform with a peak of 2kN was used for a total of 5E6 wear cycles. Three loaded soak controls were used in parallel to adjust for fluid absorption. Samples were weighed every 5E5 wear cycles.

Introduction

Removal of primary components during revision TKA procedure can damage underlying bone, resulting in defects that may need filled for stability of the revision reconstruction. Special revision components including cones and/or augments are often used to compensate for the missing bones. Little work has been done to characterize metaphyseal geometry in the vicinity of the knee joint, however, in order to motivate proper size and shape of cones and augments. The objective of this study was to use statistical shape modelling to evaluate variation in endosteal anatomy for revision TKA.

Methods

Digital models of the femur and tibia were generated through segmentation of computed tomography scans, for the femur and the tibia (n∼500). Custom software was used to perform virtual surgery and statistical shape analysis of the metaphyseal geometry.

A representative and appropriately sized revision femoral component was placed on each bone, assuming anterior referencing with an external rotation of 3 degrees from the posterior condyle axis. The outer and inner boundaries of the cortical bone were determined at the resection level and at 5 mm increments proximally, up to 40 mm. Similar analyses were performed on the tibia, using a typical revision resection (0 degrees medial and posterior slope), with outer and inner boundaries of the cortical bone were determined in 5 mm increments up to 40mm distal to the resection.

Metaphyseal contours were exported relative to the central fixation feature of the implant, and average geometries were calculated based on size, and across the entire cohort. Principal Component Analysis (PCA) was used to quantify the variability in shape, specifically to evaluate the +/− 1 and 2 standard deviation geometries at each cross section level of Principal Component 1 (PC1).

Introduction

The objective of our study was to determine the extent to which the quality of the biomechanical reconstruction when performing hip replacement influences gait performances. We aimed to answer the following questions: 1) Does the quality of restoration of hip biomechanics after conventional THR influence gait outcomes? (question 1), and 2) Is HR more beneficial to gait outcomes when compared with THR? (question 2).

Methods

we retrospectively reviewed 52 satisfied unilateral prosthetic hip patients (40 THRs and 12 HRs) who undertook objective gait assessment at a mean follow-up of 14 months. The quality of the prosthetic hip biomechanical restoration was assessed on standing pelvic radiograph by comparison to the healthy contralateral hip.

Background

Aseptic loosening is the leading cause of total knee arthroplasty (TKA) failure in the long term, of which osteolysis from polyethylene wear debris remains a problem that can limit the lifetime of TKA past the second decade. To help speed up design innovations, our goal was to develop a computational framework that could efficiently predict the effect of many sources of variability on TKA wear—including design, surgical, and patient variability.

Methods

We developed a computational framework for predicting TKA contact mechanics and wear. The framework accepts multiple forms of input data: patient-specific, population-specific, or standardized motions and forces. CAD models are used to create the FEA mesh. An analytical wear model, calibrated from materials testing (wheel-on-flat) experiments, is fully integrated into the FEA process. Isight execution engine runs a design of experiments (DOE) analysis with an outcome variable, such as volumetric wear, to guide statistical model output. We report two DOE applications to test the utility of the computational framework for performing large variable studies in an efficient manner: one to test the sensitivity of TKA wear to the femoral center of rotation, and the second to test the sensitivity of TKA wear to gait input perturbations.

INTRODUCTION

Experience with Metal on Metal (MoM) hip resurfacing devices has shown adequate cementation of the femoral head is critical for implant survival. Bone necrosis can be caused by the temperature change in the peri-prosthetic bone whilst the cement cures during implantation. This can lead to implant loosening, head/neck fracture and implant failure. During the implantation it is known that implants change shape potentially altering joint clearance and causing loosening.

Given the history of Metal on Metal implant failure due adverse tissue reactions from Cobalt and Chromium particles we sought to test a novel Ceramic on Ceramic (CoC) bearing which may mitigate such problems.

AIM

We set out to compare the behaviour of a novel ceramic femoral head component to a standard metal component in a hip resurfacing system after cemented implantation in a physiological warmed cadaveric model.

Our first aim was to perform heat transfer analysis: To document time to, and extent of, maximum temperature change on the metal/ceramic surface and inside the resurfaced femoral head bone.

Our second aim was to perform a dimensional analysis: To document any resulting deformation in the metal/ceramic femoral head bearing diameter during cementation.

Objectives

Investigate the incorporation of an antibiotic in bone cement using liposomes (a drug delivery system) with the potential to promote osseointegration at the bone cement interface whilst maintaining antibiotic elution, anti-microbiological efficacy and cement mechanical properties.

Prosthetic joint infection and aseptic loosening are associated with significant morbidity. Antibiotic loaded bone cement is commonly used and successfully reduces infection rates; however, there is increasing resistance to the commonly used gentamicin.

Previous studies have shown gentamicin incorporated into bone cement using liposomes can maintain the cement's mechanical properties and improve antibiotic elution.

The phospholipid phosphatidyl-l-serine has been postulated to encourage surface osteoblast attachment and in a liposome could improve osseointegration, thereby reducing aseptic loosening.

Preliminary clinical isolate testing showed excellent antimicrobial action with amoxicillin therefore the study aims were to test amoxicillin incorporated into bone cement using liposomes containing phosphatidyl-l-serine in terms of antibiotic elution, microbiological profile and mechanical properties.

Methods

Amoxicillin was encapsulated within 100nm liposomes containing phosphatidyl-L-serine and added to PMMA bone cement (Palacos R (Heraeus Medical, Newbury, UK)).

Mechanical testing was performed according to Acrylic Cement standards (ISO BS 5833:2002). Elution testing was carried out along with microbiological testing utilising clinical isolates.

INTRODUCTION

The cup component of modern resurfacing systems are often coated creating a cementless press-fit fixation in the acetabulum based on surgical under-reaming, also enabling osseoconduction/integration. Due to the higher density of cortical bone along the antero-superior and postero-inferior regions of the acetabulum, the greatest forces occur between the anterior and posterior columns of the pelvis. This produces pinching of the implant that can result in deformation of the cup. Metal shell/modularpress-fit acetabular cups are susceptible to substantial deformation immediately after implantation. This deformation may affect the lubrication, producing point loading and high friction torques between the head and the cup that increase wear and may lead to head clamping and subsequent cup loosening. We sought to test a novel ceramic on ceramic (CoC) hip resurfacing system that should allay any concerns with the Adverse Reaction to Metal Debris associated with metal on metal (MoM) resurfacing devices.

AIM

We sought to quantify the deformation of a novel CoC hip-resurfacing cup after implantation, using a standard surgical technique in a cadaveric model, and compare to the MoM standard. We also assessed if the design clearances proposed for this CoC hip resurfacing implant are compatible with the measured deformations, allowing for an adequate motion of the joint.

INTRODUCTION

The medial-stabilised (MS) knee implant, characterised by a spherical medial condyle on the femoral component and a medially congruent tibial bearing, was developed to improve knee kinematics and stability relative to performance obtained in posterior-stabilised (PS) and cruciate-retaining (CR) designs. We aimed to compare in vivo six-degree-of-freedom (6-DOF) kinematics during overground walking for these three knee designs.

METHODS

Seventy-five patients (42 males, 33 females, age 68.4±6.6 years) listed for total knee arthroplasty (TKA) surgery were recruited to this study, which was approved by the relevant Human Research Ethics committees. Each patient was randomly- assigned a PS, CR or MS knee (Medacta International AB, Switzerland) resulting in three groups of 23, 26 and 26 patients, respectively. Patients visited the Biomotion Laboratory at the University of Melbourne 6±1.1 months after surgery, where they walked overground at their self-selected speed. A custom Mobile Biplane X-ray (MoBiX) imaging system tracked and imaged the implanted knee at 200 Hz. The MoBiX system measures 6-DOF tibiofemoral kinematics of TKA knees during overground gait with maximum RMS errors of 0.65° and 0.33 mm for rotations and translations, respectively.

INTRODUCTION

Ceramic heads are used in hip revision surgery to mitigate corrosion concerns. Manufacturers recommend using a pristine titanium sleeve in conjunction with a well-fixed metal stem to prevent early failure of the ceramic head. However, the influence of impact force, head size, and sleeve offset on pull-off strength and seating displacement of a revision head assembly is not fully understood. Therefore, the purpose of this study was to investigate the pull-off strength and displacement of commercially available revision ceramic heads and titanium taper sleeve offsets (BIOLOX OPTION, CeramTec GmbH, Plochingen, Germany) while covering a range of clinically relevant impaction forces.

METHODS

Two head sizes (28 mm, n = 12 and 36 mm, n = 12) and two taper adapter sleeve offsets (small, n = 12 and extra-large, n =12) were tested in this study. A dynamic impaction rig was constructed to seat the head, sleeve, and stem assembly. Consistent impaction forces were achieved by a dropping a hammer fixed to a lever arm from a pre-determined height onto a standard impactor instrumented with a piezoelectric force sensor (PCB Piezotronics Inc.). Axially applied forces of 2 kN and 6 kN were used to cover a range of typical impaction forces. Three non-contact differential variable reluctance transducers (LORD Sensing Systems) were used to track the displacement of the head relative to the stem. Subsequently, samples were transferred a servo hydraulic testing machine, and a pull-off test was carried out per ISO 7206- 10 to measure the disassembly force.

Introduction

The osteogenic capability of any biomaterial is governed by a number of critical surface properties such as surface energy, surface potential, and topography. Prior work suggested that the Si-Y-O-N phase(s) present in the form of a thin (<150 nm), interrupted film at the surface of an annealed silicon nitride bioceramic may be responsible for an observed upregulation of osteoblastic activity due to passive surface properties and dissolution of chemical species. In this study high- resolution analytical electron microscopy was utilized to identify the Si-Y-O-N phase present on the annealed silicon nitride surface, and dissolution studies were employed to elucidate mechanisms of the material's favorable cell interactions.

Materials and Methods

Si₃N₄ discs (12.7 mm diameter × 1 mm thick) containing Y₂O₃ and Al₂O₃ sintering aids were processed using conventional techniques and subsequently subjected to annealing in a nitrogen atmosphere. Pre-cultured SaOS-2 osteosarcoma cells at a concentration of 5 × 10⁵ cells/ml were seeded onto sterile polished nitrogen-annealed Si₃N₄ discs in an osteogenic medium consisting of DMEM supplemented with about 50 µg/mL ascorbic acid, 10 mM β-glycerol phosphate, 100 mM hydrocortisone, and 10% fetal bovine calf serum. The samples were incubated for up to 7 days at 37°C with two medium replenishments. Transmission electron microscopy (TEM) images were acquired from focused ion beam (FIB)-prepared samples using a Hitachi HF-3300 TEM (300 kV). Scanning transmission electron microscopy (STEM) images were recorded using a Nion UltraSTEM 100 (60 kV). STEM high-angle annular dark-field (HAADF) imaging and energy dispersive X-ray spectroscopy (EDS) analyses were performed on a JEOL JEM2200FS (200 kV) equipped with a third-order CEOS aberration corrector and a Bruker XFlash silicon drift detector.

Introduction

Support of appositional bone ingrowth and resistance to bacterial adhesion and biofilm formation are preferred properties for biomaterials used in spinal fusion surgery. Although polyetheretherketone (PEEK) is a widely used interbody spacer material, it exhibits poor osteoconductive and bacteriostatic properties. In contrast, monolithic silicon nitride (Si₃N₄) has shown enhanced osteogenic and antimicrobial behavior. Therefore, it was hypothesized that incorporation of Si₃N₄ into a PEEK matrix might improve upon PEEK's inherently poor ability to bond with bone and also impart resistance to biofilm formation.

Methods

A PEEK polymer was melted and compounded with three different silicon nitride powders at 15% (by volume, vol.%), including: (i) α-Si₃N₄; (ii) a liquid phase sintered (LPS) ß-Si₃N₄; and (iii) a melt-derived SiYAlON mixture. These three ceramic powders exhibited different solubilities, polymorphic structures, and/or chemical compositions. Osteoconductivity was assessed by seeding specimens with 5 × 10⁵/ml of SaOS-2 osteosarcoma cells within an osteogenic media for 7 days. Antibacterial behavior was determined by inoculating samples with 1 × 10⁷ CFU/ml of Staphylococcus epidermidis (S. epi.) in a 1 × 10⁸/ml brain heart infusion (BHI) agar culture for 24 h. After staining with PureBlu™ Hoechst 33342 or with DAPI and CFDA for SaOS-2 cell adhesion or bacterial presence, respectively, samples were examined with a confocal fluorescence microscope using a 488 nm Krypton/Argon laser source. Images were also acquired using a FEG-SEM in secondary and backscattered modes on gold sputter-coated specimens (∼20–30Å). Hydroxyapatite (HAp) deposition was measured using a laser microscope. Raman spectra were collected for samples in backscattering mode using a triple monochromator using a 532 nm excitation source (Nd:YVO₄ diode-pumped solid-state laser).

Introduction

Titanium and its alloys are attractive biomaterials attributable to their desirable corrosion, mechanical, biocompatibility and osseointegration properties. Ti6Al4V alloy in particular remains a prominent biomaterial used in Total Hip Arthroplasty (THA) today. This is partly due to biocompatibility and stress shielding issues with CoCrMo alloys, resulting in its increasing side-lining from the THA construct. For several decades now, research efforts have been dedicated to understanding wear, corrosion and surface degradation processes in implant materials. Only recently have researchers shown interest in understanding the subsurface implications of fretting and the role it plays on implant fracture. The purpose of this study was to utilise advanced microscopy and spectroscopy techniques to characterise fretting-induced subsurface transformations in Ti6Al4V. This makes mapping specific regions that are most prone to wear and fatigue failures at the modular taper interface of THA probable. Thus, informing a proactive approach to component design and material selection.

Method

A ball-on-flat configuration was utilised in this study to achieve a Hertzian point contact for a CoCrMo – Ti6Al4V material combination. Four fretting displacement amplitudes were assessed: ±10, ±25, ±50 and ±150 µm. An initial contact pressure of 1 GPa was used for all fretting tests in this study and each fretting test lasted 6000 cycles at a frequency of 1 Hz. The simulated physiological solution consisted of Foetal Bovine Serum (FBS) diluted to 25% with Phosphate Buffered Saline (PBS) and 0.03% Sodium Azide (SA) balance. The temperature was kept at ∼37°C. Subsurface transformations in the Ti6Al4V alloy was characterised using the Transmission Electron Microscopy (TEM) to obtain high resolution micrographs. The samples were prepared using a FIB-SEM. Bright-field, dark-field and selected area electron diffraction (SAED) patterns were all captured using a scanning TEM (STEM) and Energy Dispersed X-Ray spectroscopy (EDX) mapping was carried out.

Introduction

In total knee arthroplasty, the aim is to relieve pain and provide a stable, functional knee. Sagittal stability is crucial in enabling a patient to return to functional activities. Knee implants with a medial pivot (MP) design are thought to more accurately reproduce the mechanics of the native joint, and potentially confer greater antero-posterior stability through the range of flexion than some other implant designs.

Aim

This study aims to compare the sagittal stability of four different total knee arthroplasty implant designs. Method

Comparison was made between four different implant designs: medial pivot (MP), two different types of cruciate retaining (CR1 and CR 2) and deep dish (DD). A cohort of 30 Medial Pivot (MP) knees were compared with matched patients from each of the other designs, 10 in each group. Patients were matched for age, body mass index and time to follow up.

Clinical examination was carried out by an orthopaedic surgeon blinded to implant type, and sagittal stability was tested using a KT1000 knee arthrometer, applying 67N of force at 30˚ and 90˚.

Background

Accurate placement of the glenoid component in total shoulder arthroplasty (TSA) is critical to optimize implant longevity. Commercially available patient-specific instrumentation systems can improve implant placement, but may involve considerable expense and production delays of up to six weeks. The purpose of this study was to develop a novel technique for in-house production of 3D-printed, patient-specific glenoid guides, and compare the accuracy of glenoid guidepin placement between the patient-specific guide and a standard guide using a cadaveric model.

Methods

Twenty cadaveric shoulder specimens were randomized to receive glenoid guidepin placement via standard TSA guide (Wright Medical, Memphis, TN) or patient-specific guide. Three-dimensional scapular models were reconstructed from CT scans with Mimics 20.0 imaging software (Materialise NV, Leuven, Belgium). A pre-surgical plan was created for all specimens for the central glenoid guidepin of 0º version and inclination angles. Central pin entry and exit points were also calculated. Patient-specific guides were constructed to achieve the planned pin trajectory in Rhino3D software (Robert McNeel & Associates, Seattle, WA). Guides were 3D-printed on a Form2 printer with Formlabs Dental SG Resin (Formlabs, Somerville, MA). Glenoid labrum and cartilage were removed with preservation of other soft tissues in all specimens to mimic intraoperative TSA conditions. A fellowship-trained, board-eligible orthopaedic surgeon placed a 2.5 mm diameter titanium guidepin into each glenoid using the assigned guide for each specimen. After pin placement, repeat CT scans were performed, and a blinded measurer used superimposed 3D scapular reconstructions to calculate deviation from the pre-surgical plan in version and inclination angles, dot product angle, and guide pin entry and exit points. Student's t tests were performed to detect differences between pin placements for the two groups.

Introduction

Robotic systems have been used in TKA to add precision, although few studies have evaluated clinical outcomes. We report on early clinical results evaluating patient reported outcomes (PROs) on a series of robotic-assisted TKA (RAS-TKA) patients, and compare scores to those reported in the literature.

Methods

We prospectively consented and enrolled 106 patients undergoing RAS-TKA by a single surgeon performing a measured-resection femur-first technique using a miniature bone-mounted robotic system. Patients completed a KOOS, New Knee Society Score (2011 KSS) and a Veterans RAND-12 (VR-12) pre-operatively and at 3, 6 and 12 months (M) post- operatively. At the time of publication 104, 101, and 78 patients had completed 3M, 6M, and 12M PROs, respectively.

Changes in the five KOOS subscales (Pain, Symptoms, Activities of Daily Living (ADL), Sport and recreation function (Sport/Rec) and Knee-related Quality of Life (QOL)) were compared to available literature data from FORCE – TJR, a large, prospective, national cohort of TJR patients enrolled from diverse high-volume centers and community orthopaedic practices in the U.S, as well as to individual studies reporting on conventional (CON-TKA) and computer-assisted (CAS- TKA) at 3M, and on conventional TKA at 6M. The 2011 KSS is a validated method for quantifying patient's expectations and satisfaction with their TKA procedure. Improvements in the 2011 KSS were compared with literature data at 6M post-operatively.

INTRODUCTION

Studies of retrieved TKR components demonstrate that in vivo wear on the articular surface of polyethylene liners exhibits a much higher variability on their in vitro counterparts. Only one study has attempted to validate a patient-specific model of wear with a clinically retrieved component. The purpose of this study is to investigate the relationship between observed TKR contact conditions during gait and measured volume loss on retrieved tibial components.

METHODS

Eleven retrieved ultra-high molecular weight polyethylene (UHMWPE) cruciate-retaining tibial liner components from ten separate patients (implantation time = 8.6±5.6 years) had matching gait trials of normal level walking for each knee. Volume loss on retrieved components was calculated using a coordinate measuring machine and autonomous reconstruction. Motion analysis of normal level walking gait had been conducted between 1986 and 2005 for various previous studies and stored in a consented Human Mechanics Repository, ranging from pre-operative to long-term post- operative testing. Contact location between the femoral component and the tibial component on the medial and lateral plateaus were calculated throughout stance. A previously validated and fine-tuned parametric numerical model was used to calculate TKR contact forces for each gait trial. Vertical contact forces and contact paths on the medial and lateral plateaus were input as normal force and sliding distance to a simplified Archard equation for wear with material wear constant averaged from literature (2.42 × 10⁻⁷ mm³/Nm) to compute average wear per gait cycle. Wear rates were calculated using linear regression, and Pearson correlation examined correlations between modeled and measured wear.

Background/Introduction

As a new generation of robotic systems is introduced into the world of arthroplasty, Robotic-Assisted Total Knee Arthroplasty (TKA) represents a growing proportion of a reconstructive surgeon's operative volume. This study aims to compare the post-operative readmission rate, pain scores, costs, as well as the effects on surgeon efficiency one year after adoption of these technologies into clinical practice.

Methods

A retrospective chart review was conducted regarding all conventional and robotic-assisted TKAs performed by a single surgeon in the year following January 1, 2017, the date MAKO Robotic-Assisted TKAs were introduced at our intuition. All patients over age 18 with a diagnosis of primary osteoarthritis of the knee who underwent TKA during this period were identified. Records were analyzed for differences in readmission, pain scores, tourniquet time, and operating room charges.

Introduction

Current CMS reimbursement policy for total joint replacement is aligned with more cost effective, higher quality care. Upon implementation of a standardized evidenced-based care pathway, we evaluated overall procedural costs and clinical outcomes over the 90-day episode of care period for patients undergoing TKA with either conventional (Conv.) or robotic-assisted (RAS) instrumentation.

Methods

In a retrospective review of the first seven consecutive quarters of Bundled Payment for Care Improvement (BPCI) Model 2 participation beginning January 2014, we compared 90-day readmission rates, Length of Stay (LOS), discharge disposition, gains per episode in relation to target prices and overall episode costs for surgeons who performed either RAS-TKA (3 surgeons, 147 patients) or Conv. TKA (3 surgeons, 85 patients) at a single institution. All Medicare patients from all surgeons performing more than two TKA's within the study period were included. An evidence-based clinical care pathway was implemented prior to the start of the study that standardized pre-operative patient education, anesthesia, pain management, blood management, and physical/occupational therapy throughout the LOS for all patients. Physician specific target prices were established from institutional historical payment data over a prior three year period.

Background

Over 10% of total hip arthroplasty (THA) surgeries performed in England and Wales are revision procedures¹. Malorientation of the acetabular component in THA may contribute to premature failure. Yet with increasingly younger populations receiving THA surgery (through higher incidences of obesity) and longer life expectancy in general, the lifetime of an implant needs to increase to avoid a rapid increase in revision surgery in the future.

The Evaluation of X-ray, Acetabular Guides and Computerised Tomography in THA (EXACT) trial is assessing the pelvic tilt of a patient by capturing x-rays from the patient in sitting, standing and step-up positions. It uses this information, along with a CT scan image, to deliver a personalised dynamic simulation that outputs an optimised position for the hip replacement. A clinical trial is currently in place to investigate how the new procedure improves patient outcomes².

Our aim in this project was to assess whether accurate functional assessment of pelvic tilt could be further obtained using inertial measurement units (IMUs). This would provide a rapid, non-invasive triaging method such that only patients with high levels of tilt measured by the sensors would then receive the full assessment with x-rays.

Methods

Recruited patients were fitted with a bespoke device consisting of a 3D-printed clamp which housed the IMU and fitted around the sacrum area. A wide elastic belt was fitted around the patient's waist to keep the device in place. Pelvic tilt is measured in a standing, flexed seated and step-up position while undergoing X-rays with the IMU capturing the data in parallel. Patients further completed another five repetitions of the movements with the IMU but without the x-ray to test repeatability of the measurements. Statistical analysis included measures of correlation between the X-ray and IMU measurements.

Introduction

To control anteversion of the acetabular cup and femoral stem within an appropriate angle range is extremely important in total hip arthroplasty. The sum of these angles is called the “combined anteversion” (CA), and a navigation system is necessary for its accurate intraoperative evaluation. However, navigation is too expensive and time-consuming to be commonly used. Therefore, a cheaper and easier tool for intraoperative CA evaluation is desired in the clinical field. I had an idea of marking ruler-like scales on a trial femoral head ball for this purpose. The purpose of this study was to introduce the idea in a computer simulation.

Materials and Methods

An acetabular cup, a femoral head, and a femoral stem were designed virtually using three- dimensional computer graphics software (FreeCAD). The head was assembled with the femoral stem, and the axis of the stem was tilted 7 degrees to the vertical axis, referring the angle between mechanical and anatomical axes of the femur. Ruler-like scales and a horizontal line were marked on the surface of the head. The cup inclination angle was fixed at 40 degrees and paired with the head and stem assembly. The cup axis was on the stem–neck plane, which meant that CA was zero before rotating the cup and the stem. The scale at an intersecting point of the inner edge of the cup and the horizontal line was read before and after rotating the cup and the stem. I confirmed if the sum of the rotated angles of the cup and stem and the angle indicated by the scales were consistent when they were rotated at an arbitrary angle.

Introduction

Total knee replacement (TKR) is an established and effective surgical procedure in case of advanced osteoarthritis. However, the rate of satisfied patients amounts only to about 75 %. One common cause for unsatisfied patients is the anterior knee pain, which is partially caused by an increase in patellofemoral contact force and abnormal patellar kinematics. Since the malpositioning of the tibial and the femoral component affects the interplay in the patellofemoral joint and therefore contributes to anterior knee pain, we conducted a computational study on a cruciate-retaining (CR) TKR and analysed the effect of isolated femoral and tibial component malalignments on patellofemoral dynamics during a squat motion.

Methods

To analyse different implant configurations, a musculoskeletal multibody model was implemented in the software Simpack V9.7 (Simpack AG, Gilching, Germany) from the SimTK data set (Fregly et al.). The musculoskeletal model comprised relevant ligaments with nonlinear force-strain relation according to Wismans and Hill-type muscles spanning the lower extremity. The experimental data were obtained from one male subject, who received an instrumented CR TKR. Muscle forces were calculated using a variant of the computed muscle control algorithm. To enable roll-glide kinematics, both tibio- and patellofemoral joint compartments were modelled with six degrees of freedom by implementing a polygon-contact-model representing the detailed implant surfaces. Tibiofemoral contact forces were predicted and validated using data from experimental squat trials (SimTK). The validated simulation model has been used as reference configuration corresponding to the optimal surgical technique. In the following, implant configurations, i.e. numerous combinations of relative femoral and tibial component alignment were analysed: malposition of the femoral/tibial component in mediolateral (±3 mm) and anterior-posterior (±3 mm) direction.

Introduction

Implant associated infections are responsible for over 10 % of recorded orthopaedic revision surgeries across the UK, with higher infection rates commonly observed for other endoprostheses such as cranioplasties. To prevent colonization and biofilm formation on implant surfaces, the use of silver coatings has shown positive results in clinical setting due to its synergistic function with conventional antibiotic prophylaxes. Additive manufacturing allows manufacture of entirely new implant geometries such as lattice structures to enhance osseointegration, however this limits the ability to uniformly coat implants. Direct integration of silver into the powder feedstock for selective laser melting (SLM) may allow manufacture of a biomedical alloy with innate, long lasting antimicrobial properties without compromising possible geometries and with no coating process necessary.

Methods

Feedstock powders of 15–45 micron Grade 5 Ti-64 (Renishaw Plc) and Ag-999 powder (CooksonGold) were characterized using laser particle size analysis, ICP-OES, LECO-ONH, and morphological analysis in SEM. A blend of Ti-64 with 3 wt% Ag-999 powder (Ti-643) was produced by tumble blending, and validated by SEM and EDS. Parameters for manufacture were established using a 17 point design of experiment (DoE) exploring a 2D parameter space of applied laser power and laser scanning speed. Samples were manufactured using a ConceptLaser M2 LaserCusing SLM. Density was assessed by He pycnometry, and cross-sections analysed for defects by optical microscopy. Silver distribution was mapped by micro X-Ray Fluoroscopy (µXRF) and energy-dispersive X-ray spectroscopy (EDS). Optimum parameters were identified and used to manufacture all subsequent samples.

Cylindrical Ti-643 samples were manufactured for further physical characterization and bacterial investigation, alongside control Ti-64 samples manufactured using existing optimum parameters. Samples were polished using silicon carbide papers to a 4000-grit surface finish. Contact angle measurements were made by goniometry. Silver elution characteristics were assessed by immersion in water refreshed on a daily basis, and sampled over a 14 day period using ICP-OES. Viability of S. aureus was compared to control samples according to the Japanese standard test method, JIS Z 2801:2000.

Introduction

A careful evaluation of new technologies such as robotic-arm assisted total knee arthroplasty (RATKA) is important to understand the reduction in variability among users. While there is data reviewing the use of RATKA, the data is typically presented for experienced TKA surgeons. Therefore, the purpose of this cadaveric study was to compare the variability for several surgical factors between RATKA and manual TKA (MTKA) for surgeons undergoing orthopaedic fellowship training.

Methods

Two operating surgeons undergoing orthopaedic fellowship training, each prepared six cadaveric legs for cruciate retaining TKA, with MTKA on one side (3 knees) and RATKA on the other (3 knees). These surgeons were instructed to execute a full RATKA or MTKA procedure through trialing and achieve a balanced knee. The number of recuts and final poly thickness was intra-operatively recorded. After completion of bone cuts, the operating surgeons were asked if they would perform a cementless knee based on their perception of final bone cut quality as well as rank the amount of mental effort exerted for required surgical tasks. Two additional fellowship trained orthopaedic assessment surgeons, blinded to the method of preparation, each post-operatively graded the resultant bone cuts of the tibia and femur according to the perceived percentage of cut planarity (grade 1, <25%; grade 2, 25–50%; grade 3, 51–75%; and grade 4, >76%). The grade for medial and lateral tibial bone cuts was averaged and a Wilcoxon signed rank test was used for statistical comparisons. Assessment surgeons also determined whether the knee was balanced in flexion and extension. A balanced knee was defined as relatively equal medial and lateral gaps under relatively equal applied load.

Introduction

Aseptic loosening of total knee replacements is a leading cause for revision. It is known that micromotion has an influence on the loosening of cemented implants though it is not yet well understood what the effect of repeated physiological loading has on the micromotion between implants and cement mantle. This study aims to investigate effect of physiological loading on the stability of tibial implants previously subjected to simulated intra-operative lipid/marrow infiltration.

Methods

Three commercially available fixed bearing tibial implant designs were investigated in this study: ATTUNE^®, PFC SIGMA^® CoCr, ATTUNE^® S+. The implant designs were first prepared using a LMI implantation process. Following the method described by Maag et al tibial implants were cemented in a bone analog with 2 mL of bone marrow in the distal cavity and an additional reservoir of lipid adjacent to the posterior edge of the implant. The samples were subjected to intra- operative range of motion (ROM)/stability evaluation using an AMTI VIVO simulator, then a hyperextension activity until 15 minutes of cement cure time, and finally 3 additional ROM/stability evaluations were performed.

Implant specific physiological loading was determined using telemetric tibial implant data from Orthoload and applying it to a validated FE lower limb model developed by the University of Denver. Two high demand activities were selected for the loading section of this study: step down (SD) and deep knee bend (DKB). Using the above model, 6 degree of freedom kinetics and kinematics for each activity was determined for each posterior stabilized implant design.

Prior to loading, the 3-D motion between tibial implant and bone analog (micromotion) was measured using an ARAMIS Digital Image Correlation (DIC) system. Measurement was taken during the simulated DKB at 0.25Hz using an AMTI VIVO simulator while the DIC system captured images at a frame rate of 10Hz. The GOM software calculated the distance between reference point markers applied to the posterior implant and foam bone. A Matlab program calculated maximum micromotion within each DKB cycle and averaged that value across five cycles.

The implant specific loading parameters were then applied to the three tibial implant designs. Using an AMTI VIVO simulator each sample was subjected to 50,000 DKB and 120,000 SD cycles at 0.8Hz in series; equating to approximately 2 years of physiological activity. Following loading, micromotion was measured using the same method as above.

Introduction

Although total knee replacement became a widespread procedure for the purpose of knee reconstruction, osteotomies around the knee were regularly performed. Total knee arthroplasty should be performed for advanced arthritis of the knee. With the advent of biplanar open wedge high tibial osteotomy (HTO) combined with locking plate fixation, HTO has been expanded and its surgical outcome has been improved in recent years. However, post-operative joint-line obliquity has been raised as a concern with this procedure, which may affect the outcome especially in the knees with severe varus deformity. Hence the purpose of this study is to analyze the compression and shear stresses in the knee cartilage with joint line obliquity after HTO.

Methods

Using a three-dimensional computer aided design software, the digital knee model with soft tissues was developed. The geometrical bone data used in this study were derived from commercially available human bone digital anatomy media (3972 and 3976, Pacific Research Laboratories, Inc., WA, USA). The three-dimensional knee model was transferred to finite element model. Material properties of the soft tissues and bones were derived from previous studies. The loading condition was adjusted to the load during a single-leg stance of the gait cycle, which resulted in an axial compressive load of 1200 N. Two different conditions were subjected to the analysis: normal alignment and joint-line obliquity after HTO. For the normal alignment, a static force of 1200 N was applied along the mechanical axis. For the joint-line obliquity models, a single force of 1200 N was applied rotating force directions in the frontal plane from the normal direction by 2.5º, 5º, 7.5º, and 10º, respectively.

Introduction

Joint kinematics following total knee replacement (TKR) is important as it affects joint loading, joint functionality, implant wear and ultimately patient comfort and satisfaction. It is believed that restoring the natural motion of the joint (such as the screw-home mechanism) with a medial pivot knee implant will improve clinical outcomes. Daily activities such as stair climbing and stair descent are among the most difficult tasks for these patients. This study analysed dynamic knee joint motion after implantation of a medial pivot knee implant using fluoroscopy during stair ascent and descent activity.

Methods

Ethics approval was granted by Macquarie University to undertake fluoroscopic testing. Four patients who had undergone a TKR were asked to participate in the study. All patients were operated by a single surgeon (JS) and were implanted with a medial pivot knee prosthesis (Sphere, Medacta International). Participants were tested at the 12 month post-operative time- point.

Participants were asked to step up or down a short stair-case at a comfortable self-selected speed. Fluroscopic images were taken using a flat panel Artis Zeego (Siemens Healthcare GmbH, Erlangen) angiography system during the dynamic activity. Images were processed using Joint Track Auto (Banks, University of Florida), whereby the specific femoral and tibial component CAD files were superimposed onto the fluoroscopic images, ensuring an optimised match to the outlined components. Joint kinematics were calculated using custom written code in Matlab 2017a.

Introduction

Fifteen percent of the primary total knee arthroplasties (TKA) fails within 20 years. Among the main causes for revision surgery are instability and patellofemoral pain. Currently, the diagnostic pathway requires various diagnostic techniques to reveal the original cause for the failed knee prosthesis and is therefore time consuming and inefficient.

Accordingly, there is a growing demand for a diagnostic tool that is able to simultaneously visualize soft tissue structures, bone and TKA. Magnetic resonance imaging (MRI) is capable of visualising all the structures in the knee although a trade- off needs to be made between metal artefact reducing capacities and image quality. Low-field MRI (0.25T) results in less metal artefacts and a lower image quality compared with high-field MRI (1.5T). The aim of this study is to develop a MRI imaging guide to image the problematic TKA and to evaluate this guide by comparing low-field and high-field MRI on a case study.

Method

Based on literature and current differential diagnostic pathways a guide to diagnose patellofemoral pain, instability, malposition and signs of infection or fracture with MRI was developed. Therefore, methods as Insall Salvati, patellar tilt angle and visibility of fluid and soft tissues were chosen. Visibility was scored on a VAS scale from 0 to 100mm (0mm zero visibility, 100mm excellent visibility).

Subsequently, this guide is used to analyse MRI scans made of a volunteer (female, 61 years, right knee) with primary TKA (Biomet, Zimmer) in sagittal, coronal and transversal direction with a FSE PD metal artefact reducing (MAR) sequence (TE/TR 12/1030ms, slice thickness 4.0mm, FOV 260×260×120mm³, matrix size 224×216) on low-field MRI (Esaote G-scan Brio, 0.25T) and with a FSE T₁-weighted high bandwidth MAR sequence (TE/TR 6/500ms, slice thickness 3.0mm, FOV 195×195×100mm³, matrix size 320×224) on high-field MRI (Avanto 1.5T, Siemens).

Scans were analysed three times by one observer and the intra observer reliability was calculated with a two-way random effects model intra class correlation coefficient (ICC).

Background

Degeneration of the shoulder joint is a frequent problem. There are two main types of shoulder degeneration: Osteoarthritis and cuff tear arthropathy (CTA) which is characterized by a large rotator cuff tear and progressive articular damage. It is largely unknown why only some patients with large rotator cuff tears develop CTA. In this project, we investigated CT data from ‘healthy’ persons and patients with CTA with the help of 3D imaging technology and statistical shape models (SSM). We tried to define a native scapular anatomy that predesignate patients to develop CTA.

Methods

Statistical shape modeling and reconstruction:

A collection of 110 CT images from patients without glenohumeral arthropathy or large cuff tears was segmented and meshed uniformly to construct a SSM. Point-to-point correspondence between the shapes in the dataset was obtained using non-rigid template registration. Principal component analysis was used to obtain the mean shape and shape variation of the scapula model. Bias towards the template shape was minimized by repeating the non-rigid template registration with the resulting mean shape of the first iteration.

Eighty-six CT images from patients with different severities of CTA were analyzed by an experienced shoulder surgeon and classified. CT images were segmented and inspected for signs of glenoid erosion. Remaining healthy parts of the eroded scapulae were partitioned and used as input of the iterative reconstruction algorithm. During an iteration of this algorithm, 30 shape components of the shape model are optimized and the reconstructed shape is aligned with the healthy parts. The algorithm stops when convergence is reached.

Introduction

Titanium and its alloys are attractive biomaterials attributable to their desirable corrosion, mechanical, biocompatibility and osseointegration properties. In particular, β – titanium alloys like the TMZF possess other advantages such as its lower modulus compared to Ti6Al4V alloy. This reduces stress shielding effect in Total Hip Arthroplasty (THA) and the replacement of V in the Ti6Al4V alloy, eliminates in-vivo V-induced toxicity. Unfortunately, implants made of TMZF were later recalled by the FDA due to higher than acceptable revision rates. The purpose of this study was to compare the fretting corrosion characteristics of Ti6Al4V and TMZF titanium alloys. It is hoped the findings will inform better design of β – titanium alloys for future applications in THA.

Method

A ball-on-flat configuration was utilised in this study to achieve a Hertzian point contact for CoCrMo – Ti6Al4V and CoCrMo – TMZF material combinations. These were assessed at a fretting displacement of ±50 µm at an initial contact pressure of 1 GPa. Each fretting test lasted 6000 cycles at a frequency of 1 Hz. A two-electrode cell set-up was used to monitor in-situ open circuit potential (OCP). The simulated physiological solution consisted of Foetal Bovine Serum (FBS) diluted to 25% with Phosphate Buffered Saline (PBS) and 0.03% Sodium Azide (SA) balance. The temperature was kept at ∼37°C. Corrosion products on the worn surfaces and subsurface transformations in both alloys were characterised using the Scanning and Transmission Electron Microscopy (SEM/TEM) to obtain high resolution micrographs. The samples were prepared using a FIB-SEM. Bright-field, dark-field and selected area electron diffraction (SAED) patterns were all captured using a scanning TEM (STEM) and Energy Dispersed X-Ray spectroscopy (EDX) mapping was carried out.

Background

Recently, a larger number of elderly individuals with osteoporosis has undergone total knee arthroplasty (TKA). Intuitively, such vulnerable bone condition should deteriorate post-TKA functional recovery compared to a non-osteoporotic condition, but this hypothesis has not been directly examined.

Methods

To address this issue, we analysed prognosis of patients who underwent TKA in Toranomon Hospital in Japan between April 2016 and March 2017 (27 of 40 cases, age 75.0±8.2 years old, BMI 24.5±3.1), and evaluated effects of osteoporosis on the changes in functions of the knees three/six/twelve months after the operation. The knee functions were quantified based on Knee Society Score (KSS), and the severity of the pre-operative osteoporosis was evaluated by T-score. We examined the relationships between these scores using multiple regression analyses with age, BMI, and sex as covariates. We excluded patients with rheumatoid arthritis.

Introduction

Rotational or axial alignment is an important concept in total knee surgery. Malrotation of the femoral component can lead to patellofemoral maltracking, pain and stiffness. In reconstruction surgery of the knee, achievement of correct rotation is even more difficult because of the lack of anatomical landmarks. The linea aspera is often the only remaining landmark, but its reliability is questionable.

Goal of research

Can custom-made 3D-guides help with rotational alignment of the knee after a wide resection of the distal femur?

Background

Alignment and soft tissue (ligament) balance are two variables that are under the control of a surgeon during replacement arthroplasty of the knee. Mobile bearing medial unicompartmental knee replacements have traditionally advocated sizing the prosthesis based on soft tissue balance while accepting the natural alignment of the knee, while fixed bearing prosthesis have tended to correct alignment to a pre planned value, while meticulously avoiding overcorrection. The dynamic loading parameters like peak adduction moment (PKAM) and angular adduction Impulse (Add Imp) have been studied extensively as proxies for medial compartment loading. In this investigation we tried to answer the question whether correcting static alignment, which is the only alignment variable under the control of the surgeon actually translates into improvement in dynamic loading during gait. We investigated the effect of correction of static alignment parameter Hip Knee Ankle (HKA) angle and dynamic alignment parameter in coronal plane, Mean Adduction angle (MAA) on 1st Peak Knee Adduction Moment (PKAM) and Angular Adduction Impulse (Add Imp) following medial unicompartmental knee replacements.

Methods

Twenty four knees (20 patients) underwent instrumented gait analysis (BTS Milan, 12 cameras and single Kistler force platform measuring at 100 Hz) before and after medial uni compartmental knee replacement. The alignment was measured using long leg alignment views, to assess Hip Knee Ankle (HKA) angle. Coronal plane kinetics namely 1st Peak Knee Adduction Moment (PKAM) and angular adduction impulse (Add Imp)- which is the moment time integral of the adduction moment curve were calculated to assess medial compartment loading. Single and multiple regression analyses were done to assess the effect of static alignment parameters (HKA angle) and dynamic coronal plane alignment parameters (Mean Adduction Angle – MAA) on PKAM and Add Imp.

Introduction

Impingement of total hip arthroplasties (THAs) has been reported to cause rim damage of polyethylene liners, and in some instances has led to dislocation and/or mechanical failure of liner locking mechanisms in modular designs. Elevated rim liners are used to improve stability and reduce the risk of dislocation, however they restrict the possible range of motion of the joint, and retrieval studies have found impingement related damage on lipped liners.

The aim of this study was to develop a tool for assessing the occurrence of impingement under different activities, and use it to evaluate the effects a lipped liner and position of the lip has on the impingement-free range of motion.

MATERIALS & METHOD

A geometrical model incorporated a hemi-pelvis and femur geometries of one individual with a THA (DePuy Pinnacle® acetabular cup with neutral and lipped liners; size 12 Corail® stem with 32mm diameter head) was created in SOLIDWORKS (Dassault Systèmes). Joint motions were taken from kinematic data of activities of daily living that were associated with dislocation of THA, such as stooping to pick an object off the floor and rolling over. The femoral component was positioned to conform within the geometry of the femur, and the acetabular component was orientated in a clinically acceptable position (45° inclination and 20° anteversion). Variation in orientation of the apex of the lip was investigated by rotating about the acetabular axes from the superior (0°) in increments of 45° (0°−315°), and compared to a neutral liner.

Introduction

Corrosion at modular junctions of total hip replacements has been identified as a potential threat to implant longevity, resulting in efforts to determine appropriate countermeasures. Visual scoring and volumetric material loss measurements have been useful tools to elucidate various clinical and design factors associated with corrosion damage. However, corrosion involves electron exchange that results in chemical changes to biomedical alloys, and electrochemical assessment may therefore be a more appropriate approach to understand the phenomenon. The purpose of this pilot study was to electrochemically distinguish the severity of corrosion in retrieved femoral heads. A secondary goal was to identify the potential of electrochemical impedance spectroscopy (EIS) as a method to identify different forms of corrosion damage.

Methods

Twenty femoral heads were identified from a larger study of total hip replacements, obtained as part of an ongoing multi- center IRB-approved retrieval program. Using a previously established 4-point scoring method, components were binned by taper damage: 10 components were identified as having severe damage, 7 with moderate damage and 2 with mild damage. One (1) unimplanted control was included to represent minimal corrosion damage. All components were then characterized using electrochemical impedance spectroscopy under the frequency domain: a 10 mV sinusoidal voltage, ranging from 20 kHz to 2 mHz, was applied to the taper of a femoral head (working electrode) filled with a 1M solution of PBS, a platinum counter electrode and a chlorided silver reference electrode. Absolute impedance at 2 mHz (|Z_0.002|), and max phase angle (θ) were assessed relative to taper damage severity. After least-squares fitting of the EIS data to a Randles circuit with a constant phase element, circuit elements: polarization resistance (Rp), CPE-capacitance, and CPE-exponent were also evaluated. The seven (7) most severely corroded components were further examined with scanning electron microscopy to identify corrosion modes. For all statistical analyses, significance was determined at alpha=0.05.

Introduction

Osteoarthritis (OA), a painful, debilitating joint disease, often caused by excessive joint stress, is a leading cause of disability (World Health Organisation, 2003) and increases with age and obesity. A 5° varus malalignment increases loading in the medial knee compartment from 70% to 90% (Tetsworth and Paley, 1994). Internal unloading implants, placed subcutaneously upon the medial aspect of the knee joint, are designed to offload the medial compartment of the knee without violating natural joint tissues. The aim of this study is to investigate the effect of an unloading implant, such as the Atlas™ knee system, on stress within the tibiofemoral joint with different grades of cartilage defects.

Methods

To simulate surgical treatment of medial knee OA, a three-dimensional computer-aided design of an Atlas™ knee system was virtually fixed to the medial aspect of a validated finite element knee model (Mootanah, 2014), using CATIA v5 software (Dassault Systèmes, Velizy Villacoublay, France). The construct was meshed and assigned material properties and boundary conditions, using Abaqus finite element software (Dassault Systèmes, Velizy Villacoublay, France). A cartilage defect was simulated by removing elements corresponding to 4.7 mm². The international cartilage repair society (ICRS) Grade II and III damage were simulated by normalized defect depth of 33% and 67%, respectively. The femur was mechanically grounded and the tibia was subjected to loading conditions corresponding to the stance phase of walking of a healthy 50-year-old 68-Kg male with anthropometrics that matched those of the cadaver. Finite element analyses were run for peak shear and von Mises stress in the medial and lateral tibiofemoral compartments.

Background

Stress fractures at tracker after computer navigated total knee replacement are rare. Periprosthetic fracture after Minimally Invasive Plate Osteosynthesis (MIPO) of stress fracture through femoral tracker is unique in orthopaedic literature. We are reporting this unique presentation of periprosthetic fractures after MIPO for stress fracture involving femoral pin site track in computer assisted total knee arthroplasty, treated by reconstruction nail (PFNA).

Methods

A 75-year old female, who had computer navigated right total knee replacement, was admitted 6 weeks later with increasing pain over distal thigh for 3 weeks without trauma. Prior to onset of pain, she achieved a range of movements of 0–105 degrees. Perioperative radiographs did not suggest obvious osteoporosis, pre-existent benign or malignant lesion, or fracture. Radiographs demonstrated transverse fracture of distal third of femur through pin site track. We fixed the fracture with 11-hole combihole locking plate by MIPO technique. Eight weeks later, she was readmitted with periprosthetic fracture through screw hole at the tip of MIPO Plate and treated by Reconstruction Nail (PFNA), removal of locking screws and refixation of intermediate segment with unicortical locking screws. Then she was protected with plaster cylinder for 4 weeks and hinged brace for 2 months.

Background

Mechanics and kinematics of the knee following total knee replacement are related to the mechanics and kinematics of the normal knee. Restoration of neutral alignment is an important factor affecting the long-term results of total knee replacement. Tibial cut is a vital and crucial step in ensuring adequate and appropriate proximal tibial resection, which is essential for mechanical orientation and axis in total knee replacement. Tibial cut must be individually reliable, reproducible, consistent and an accurate predictor of individual anatomical measurements. Conventional tibial cuts of tibia with fixed measurements cannot account for individual variations. While computer navigated total knee replacement serves as a medium to achieve this objective, the technology is not universally applicable for differing reasons. Therefore we evolved the concept and technique of Condylar Differential for planned tibial cuts in conventional total knee replacement, which accounts for individual variations and reflects the individual mechanical orientation and alignment.

Methods

We used the Condylar Differential in 37 consecutive total knee replacements. We also applied the technique in valgus knees and severe advanced osteoarthritis. First a vertical line is drawn on the digital weight bearing anteroposterior radiograph for mechanical axis of tibia. Then a horizontal line is drawn across and perpendicular to the mechanical axis of tibia. The distances between the horizontal line and the lowest reproducible points of the articular surfaces of the medial and lateral tibial condyles respectively are measured. The difference between the two measurements obviously represents the Condylar Differential. Condylar Differential, adjusted to the nearest millimeter, is maintained in executing the tibial cuts, if necessary successive cuts.

OBJECTIVE

Debridement, Antibiotics and Implant Retention (DAIR) procedure is well established for Prosthetic Joint Infection (PJI) in acute setting after total hip and knee replacements. We present our perspective of DAIR in a relatively a small cohort following hip and knee replacements in a District General Hospital (DGH) in United Kingdom, where we delivered comparable results to leading tertiary centers in short to mid-term followup.

METHODS

We undertook a retrospective study involving 14 patients, who underwent DAIR in our DGH between August 2012 and December 2015. Patient cohort included primary, complex primary and revision hip and knee replacements. Multiple samples were taken intraoperatively for cultures and histology. mMicrobiological support was provided by a microbiologist with interest in musculoskeletal infections.