The advent of modular implants aims to minimise morbidity associated with revision of hemiarthroplasty or total shoulder arthroplasty (TSA) to reverse shoulder arthroplasty (RSR) by allowing retention of the humeral stem. This systematic review aimed to summarise outcomes following its use and reasons why modular humeral stems may be revised. A systematic review of Pubmed, Medline and EMBASE was performed according to PRISMA guidelines of all patients undergoing revision of a modular hemiarthroplasty or TSA to RSR. Primary implants, glenoid revisions, surgical technique and opinion based reports were excluded. Collected data included demographics, outcomes and incidence of complications. 277 patients were included, with a mean age of 69.8 years (44-91) and 119 being female. Revisions were performed an average of 30 months (6-147) after the index procedure, with the most common reason for revision being cuff failure in 57 patients. 165 patients underwent modular conversion and 112 underwent stem revision. Of those that underwent humeral stem revision, 18 had the stem too proximal, in 15 the stem was loose, 10 was due to infection and 1 stem had significant retroversion. After a mean follow up of 37.6 months (12-91), the Constant score improved from a mean of 21.8 to 48.7. Stem revision was associated with a higher complication rate (OR 3.13, 95% CI 1.82-5.39). The increased use of modular stems has reduced stem revision, however 40% of these implants still require revision due to intra-operative findings. Further large volume comparative studies between revised and maintained humeral stems post revision of modular implants can adequately inform implant innovation to further improve the stem revision rate.
In 2020 almost 90% of femoral heads for total hip implants in Germany were made of ceramic. Nevertheless, the cellular interactions and abrasion mechanisms in vivo have not been fully understood until now. Metal transfer from the head-neck taper connection, occurring as smear or large-area deposit, negatively influences the surface quality of the articulating bearing. In order to prevent metal transfer, damage patterns of 40 Biolox delta ceramic retrievals with CoC and CoPE bearings were analysed. A classification of damage type and severity for each component (n=40) was done according to an established scoring system. To investigate the physical properties, the surface quality was measured using confocal microscopy, quantitative analysis of phase composition were performed by Raman spectroscopy and qualitative analysis of metal traces was done by scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX). The periprosthetic tissue was analysed for abrasion particles with SEM and EDX. Both bearing types show different damage patterns. Dotted/ drizzled metal smears were identified in 82 % of CoC (n=16) and 96 % of CoPE (n=24) bearings. Most traces on the ceramic heads were identified in the proximal area while they were observed predominantly in the distal area for the ceramic inlays. The identified marks are similar to those of metallic bearings. Metallic smears lead to an increase of up to 30 % in the monoclinic crystalline phase of the ceramic. The roughness increases by up to six times to Ra=48 nm. Ceramic and metallic wear particles from the articulating surfaces or head neck taper junctions were found in the periprosthetic tissue. Damage patterns on CoC hip implants seem to be similar to those of metallic implants. More detailed analysis of CoC implants are needed to understand the described damage patterns and provide advice for prevention.
Dual mobility (DM) hip implants whereby the polyethylene liner is “free-floating” are being used increasingly clinically. The motion of the liner is not well understood and this may provide insight into failure mechanisms; however, there are no published methods on tracking liner motion while testing under clinically relevant conditions. The aim was to develop and evaluate a bespoke inertial tracking system for DM implants that could operate submerged in lubricant without line-of-sight and provide 3D orientation information. Trackers (n=5) adhered to DM liners were evaluated using a robotic arm and a six-degree of freedom anatomical hip simulator. Before each set of testing the onboard sensor suites were calibrated to account for steady-state and non-linearity errors. The trackers were subjected to ranges of motion from ±5° to ±25° and cycle frequencies from 0.35Hz to 1.25Hz and the outputs used to find the absolute error at the peak angle for each principle axis. In total each tracker was evaluated for ten unique motion profiles with each sequence lasting 60 cycles.Abstract
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Methods
Impingement of total hip replacements (THRs) can cause rim damage of polyethylene liners, and lead to dislocation and/or mechanical failure of liner locking mechanisms[1]. A geometric model of a THR in situ was previously developed to predict impingement for different component orientations and joint motions of activities[2]. However, the consequence of any predicted impingement is unknown. This study aimed to develop an in-vitromethod to investigate the effects of different impingement scenarios. A ProSim electro-mechanical single-station hip simulator (Simulation Solutions) was used, and the 32mm diameter metal-on-polyethylene THRs (DePuy Synthes) were assessed. The THR was mounted in an inverted orientation, and the input (motion and loading) applied simulated a patient stooping over to pick an object from the floor[3]. The impingement severity was varied by continuing motion past the point of impingement by 2.5° or 5°, and compressive load applied in the medial-lateral direction was varied from 100N to 200N. Each test condition was applied for 40,000 cycles (n=3). Rim penetration was assessed using a CMM and component separation was measured during the tests.Abstract
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Method
The current average tariff of a total knee replacement (TKR) is £5500. The approximate cost of each knee prosthesis is £2500. Therefore, length of patient stay (LOS) and the cost of patient rehabilitation influence the total costs significantly. Previous studies have shown a mean LOS of between 5 and 9.4 days for patients undergoing primary unilateral TKR but none looked at the factors influencing length of stay following bilateral primary total knee replacements (BTKR) at the same sitting. To identify significant factors that influence the LOS following BTKR at the same sitting in a single centre in the UK.Background
Objectives
Total joint replacement is a successful clinical intervention. However, aseptic loosening due to wear related particulate debris is still one of the most frequent reasons for late revision of total joint replacement. This lecture gives an overview about the application of methods to study wear and friction in total joint replacements (e.g. hip, knee, shoulder). This involves complex joint simulation conditions as well as analytical assessments. Regarding joint simulation the focus will be on ligament stabilized joints. New approaches will be shown and discussed. Furthermore, analytical methods to study the release of wear products in term of solid particles and soluble complexes like metal ions will be presented.
As the demand for primary total knee arthroplasty (TKA) has been on the rise, so will be the demand for revision knee surgery. Nevertheless, our knowledge on the modes of failure and factors associated with failure of knee revision surgery is considerably lower to that known for primary TKA. To date, this has been mostly based on case series within the literature. Therefore, the aim of this study was to evaluate the survivorship of revision TKA and determine the reasons of failure. A retrospective study was conducted with prior approval of the institutional audit department. This involved evaluation of existing clinical records and radiographs of patients who underwent revision knee surgery at our institution between 2003 and 2015. Re-revision was identified as the third or further procedure on the knee in which at least one prosthetic component was inserted or changed.Introduction
Methods
Ruling out an infection in one-stage knee and hip revisions for presumed aseptic failure by conventional tissue cultures takes up to 14 days. Multiplex polymerase chain reaction (PCR) is a quick test (4–5 hours) for detecting infections. The purpose of this study was to evaluate the negative predictive value of an automated multiplex PCR for the detection of microorganisms in synovial fluid obtained intraoperatively in unsuspected knee and hip revisions. The NPV of the multiplex PCR U-ITI system of synovial fluid compared to tissue cultures of knee and hip revisions was 95.7% and 92.5%, respectively. Cultures required several days for growth whereas the automated mPCR U-ITI system provided results within five hours. The multiplex PCR U-ITI system is a quick and reliable test in ruling out infection in presumed aseptic knee and hip revisions. With this test the number of unsuspected infected revisions can be lowered and antibiotic overtreatment as well as undertreatment after one-stage revision arthroplasty can be avoided. This directly results in a reduction in length of hospital stay, hospital costs and possible antibiotic resistance development.
Post-operative acute kidney injury is significant complication following surgery. Patients who develop AKI have an increased risk for progression into chronic kidney disease, end-stage renal failure and increased mortality risk. The patient outcomes following total knee replacement (TKR), who develop AKI has been a topic of interest in recent years as it may have patient and medicolegal implications. Nevertheless, there are no studies looking at the incidence, risk factors and outcomes of AKI following bilateral TKRs at the same sitting. To determine the incidence, risk factors and outcomes of post-operative AKI following bilateral TKRs surgery at the same sitting.Background
Objectives
Experimental simulation is the gold standard wear testing method for total knee replacements (TKR), with reliable replication of physiological kinematic conditions. When combined with a computational model, such a framework is able to offer deeper insight into the biomechanical and wear mechanisms. The current study developed and validated a comprehensive combined experimental and computational framework for pre-clinical biomechanics and wear simulation of TKR. A six-station electro-mechanical knee simulator (SimSol, UK), capable of replicating highly demanding conditions with improved input kinematic following, was used to determine the wear of Sigma fixed bearing curved TKRs (DePuy, UK) under three different activities; standard-walking, deep-squat, and stairs-ascending. The computational model was used to predict the wear under these 3 conditions. The wear calculation was based on a modification of Archard's law which accounted for the effects of contact stress, contact area, sliding distance, and cross-shear on wear. The output wear predictions from the computational model were independently validated against the experimental wear rates. The volumetric wear rates determined experimentally under standard-walking, deep-squat, and stairs-ascending conditions were 5.8±1.4, 3.5±0.8 and 7.1±2.0 [mm3/mc] respectively (mean ± 95% CI, n=6). The corresponding predicted wear rates were 4.5, 3.7, and 5.6 [mm3/mc]. The coefficient of determination for the wear prediction of the framework was 0.94. The wear predictions from the computational model showed good agreement with the experimental wear rates. The model did not fully predict the changes found experimentally, indicating other factors in the experimental simulation not yet incorporated in the framework, such as plastic deformation, may play an additional role experimentally in high demand activities. This also emphasises the importance of the independent experimental validation of computational models. The combined experimental and computational framework offered deeper insight into the contact mechanics and wear from three different standard and highly demanding daily activities. Future work will adopt the developed framework to predict the effects of patients and surgical factors on the mechanics and wear of TKR.
Total ankle replacement (TAR) is a substitute to ankle fusion, replacing the degenerated joint with a mechanical motion-conserving alternative. Compared with hip and knee replacements, TARs remain to be implanted in much smaller numbers, due to the surgical complexity and low mid-to-long term survival rates. TAR manufacturers have recently explored the use of varying implant sizes to improve TAR performance. This would allow surgeons a wider scope for implanting devices for varying patient demographics. Minimal pre-clinical testing has been demonstrated to date, while existing wear simulation standards lack definition. Clinical failure of TARs and limited research into wear testing defined a need for further investigation into the wear performance of TARs to understand the effects of the kinematics on varying implant sizes. Six medium and six extra small BOX® (MatOrtho) TARs will be tested in a modified knee simulator for 5 million cycles (Mc). The combinations of simulator inputs that mimic natural gait conditions were extracted from ankle kinematic profiles defined in previous literature. The peak axial load will be 3.15 kN, which is equivalent to 4.5 times body weight of a 70kg individual. The flexion profile ranges from 15° plantarflexion to 15° dorsiflexion. Rotation about the tibial component will range from −2.3° of internal rotation to 8° external rotation, while the anterior/posterior displacement will be 7mm anterior to −2mm posterior throughout the gait cycle. The components will be rotated through the simulation stations every Mc to account for inter-station variability. Gravimetric measurements of polyethylene wear will be taken at every Mc stage. A contact profilometer will also be used to measure average surface roughness of each articulating surface pre-and-post simulation. The development of such methods will be crucial in the ongoing improvement of TARs, and in enhancing clinical functionality, through understanding the envelope of TAR performance.
Patients with knee prosthetic joint infection (PJI) frequently receive one- or two-stage revision. To explore the feasibility of a randomised controlled trial (RCT) comparing methods, we analysed a UK registry, interviewed patients and surgeons, systematically reviewed literature, held a consensus meeting, and assessed progress of an RCT in hip PJI. In 2014, in England and Wales, knee PJI was treated with one- or two-stage procedures in 19% and 71% of patients respectively. Between 2007 and 2014, use of one-stage procedures doubled and, in major centres, up to 42% of treatments were one-stage. We conducted in-depth interviews with 16 patients with knee PJI and 11 surgeons performing one- or two-stage revision. Patients considered randomisation acceptable with appropriate counselling and, depending on infecting organisms and health status, surgeons would randomise treatments. In meta-analysis, two-year re-infection rates in 10 one-stage series (423 patients) and 108 two-stage series (5,129 patients) were 7.6% (95%CI 3.4,13.1) and 8.8% (7.2,10.6) respectively. In a series of patients with knee PJI, surgeons from 2 major centres considered 6/15 patients eligible for either treatment, with 4 more potentially eligible after treatment of soft tissue infection. In an ongoing RCT of surgical treatment of hip PJI, 116 patients have been randomised at 14 centres in 3 years. Randomising patients with PJI is feasible but, as knee PJI is uncommon, a multicentre RCT would be required. Based on WOMAC score outcome and appropriate assumptions on eligibility and acceptability, 170 patients would need to be randomised over 4 years at 14 major centres.
We report a prospective study of clinical data collected pre, intra and post operation to remove both cup and head components of 118 failed, current generation metal on metal (MOM) hips. Whilst component position was important, the majority were unexplained failures and of these the majority (63%) had cup inclination angles of less than 55 degrees. Poor biocompatibility of the wear debris may explain many of the failures. Morlock et al reported a retrospective analysis of 267 MOM hips but only 34 head and cup couples (ie most were femoral neck fractures) and without data necessary to define cause of failure. The commonest cause of failure in the National Joint Registry (NJR) is unexplained.SUMMARY
BACKGROUND
Patient reported outcome measures (PROMs) are important for assessing the results of lower limb arthroplasty. Unrealistic or uneducated expectations may have a significant negative impact on PROMs even when surgery is technically successful. This study's aim was to quantify pre-operative expectations of Scottish patients undergoing total hip and knee replacement (THR/TKR). 100 THR and 100 TKR patients completed validated questionnaires (from the Hospital for Special Surgery) prior to their operation after receiving standard pre-operative information (booklet, DVD, consultations). Each patient rated expectations from very important to not having the expectation. A total score was calculated using a numerical scale for the grading of each expectation. Univariate regression analysis was used to investigate the relationship between demographics and expectation score. The THR cohort had mean age 66.2 (SD 10.5), 53% female, mean BMI 29.0 (SD 5.1) and mean Oxford score 44 (SD 7). The TKR cohort had mean age 67.6 (SD 8.5), 59% female, mean BMI 32.8 (SD 5.8) and mean Oxford score 44 (SD 8). 100% THR and 96% TKR patients had 10 or more expectations of their operation. All expected pain relief. Other improvements expected were: walking for 100% THA and 99% TKA patients; daily activities for 100% THAs and 96% TKAs; recreational activities for 96% THAs and 93% TKAs; sexual activity for 66% THAs and 59% TKAs; psychological well-being for 98% THAs and 91% TKAs. Regression analysis showed increasing age lowered expectations in both THR (p=0.025) and TKR (p=0.031) patients but that gender, BMI and Oxford score were not significantly related to expectations. This study highlights that patients expect far more than pain relief and improved post-operative mobility from their operation. It is important to discuss and manage these expectations with patients prior to surgery. By doing so, patient satisfaction and PROMs should further improve.
Prosthetic UHMWPE added with vitamin E and crosslinked UHMWPE are able to decrease significantly the adhesion of various bacterial and fungal strains limiting biomaterial associated infection and consequent implant failure. Polyethylene abrasive and oxidative wear induces overtime Summary
Introduction
Total hip arthroplasties (THAs) in young patients are associated with high failure rates. We always use cemented total hip implants, however, in cases with acetabular bone stock loss we perform bone impaction grafting. Our purpose was to evaluate the outcome of 69 consecutive primary cemented total hips in patients younger than 30 years followed between 2 to 18 years. Between 1988 and 2004, 69 consecutive primary cemented THAs (mainly Exeters) were performed in 48 patients (32 women, 16 men) younger than thirty years. Average age at time of operation was 25 years (range, 16 to 29 years). Twenty-nine hips (42%) underwent acetabular bone impaction grafting because of acetabular bone loss. Mean follow-up was 10 years (range, 2 to 18 years). Revisions were determined, Harris Hip Score (HHS), and Oxford Hip Questionnaire Score (OHQS) were obtained and radiographs were analyzed. Survival was calculated using the Kaplan-Meier method.Introduction
Methods
