Anterior approach total hip arthroplasty (AA-THA) has a steep learning curve, with higher complication rates in initial cases. Proper surgical case selection during the learning curve can reduce early risk. This study aims to identify patient and radiographic factors associated with AA-THA difficulty using Machine Learning (ML). Consecutive primary AA-THA patients from two centres, operated by two expert surgeons, were enrolled (excluding patients with prior hip surgery and first 100 cases per surgeon). K- means prototype clustering – an unsupervised ML algorithm – was used with two variables - operative duration and surgical complications within 6 weeks - to cluster operations into difficult or standard groups. Radiographic measurements (neck shaft angle, offset, LCEA, inter-teardrop distance, Tonnis grade) were measured by two independent observers. These factors, alongside patient factors (BMI, age, sex, laterality) were employed in a multivariate logistic regression analysis and used for k-means clustering. Significant continuous variables were investigated for predictive accuracy using Receiver Operator Characteristics (ROC). Out of 328 THAs analyzed, 130 (40%) were classified as difficult and 198 (60%) as standard. Difficult group had a mean operative time of 106mins (range 99–116) with 2 complications, while standard group had a mean operative time of 77mins (range 69–86) with 0 complications. Decreasing inter-teardrop distance (odds ratio [OR] 0.97, 95% confidence interval [CI] 0.95–0.99, p = 0.03) and right-sided operations (OR 1.73, 95% CI 1.10–2.72, p = 0.02) were associated with operative difficulty. However, ROC analysis showed poor predictive accuracy for these factors alone, with area under the curve of 0.56. Inter-observer reliability was reported as excellent (ICC >0.7). Right-sided hips (for right-hand dominant surgeons) and decreasing inter-teardrop distance were associated with case difficulty in AA-THA. These data could guide case selection during the learning phase. A larger dataset with more complications may reveal further factors.
The Posterior and Lateral approaches are most commonly used for Total Hip Arthroplasty (THA) in the United Kingdom (UK). Fewer than 5% of UK surgeons routinely use the Direct Anterior Approach (DAA). DAA THA is increasing, particularly among surgeons who have learned the technique during overseas fellowships. Whether DAA offers long-term clinical benefit is unclear. We undertook a retrospective analysis of prospectively collected 10-year, multi-surgeon, multi-centre implant surveillance study data for matched cohorts of patients whose operations were undertaken by either the DAA or posterior approach. All operations were undertaken using uncemented femoral and acetabular components. The implants were different for the two surgical approaches. We report the pre-operative, and post operative six-month, two-year, five-year and 10-year Oxford Hip Score (OHS) and 10-year revision rates. 125 patients underwent DAA THA; these patients were matched against those undergoing the posterior approach through propensity score matching for age, gender and body mass index. The 10-year revision rate for DAA THA was 3.2% (4/125) and 2.4% (3/125) for posterior THA. The difference in revision rate was not statistically significant. Both DAA and Posterior THA pre-operative OHS were comparable at 19.85 and 19.12 respectively. At the six-month time point, there was an OHS improvement of 20.89 points for DAA and 18.82 points for Posterior THA and this was statistically significant (P-Value <0.001). At the two, five and 10-year time-points the OHS and OHS improvement from the pre-operative review were comparable. At the 10-year time point post-op the OHS for DAA THA was 42.63, 42.10 for posterior THA and the mean improvement from pre-op to 10-years post op was 22.78 and 22.98 respectively. There was no statistical difference when comparing the OHS or the OHS mean improvements at the two, five and 10-year point. Whilst there was greater improvement and statistical significance during the initial six month time period, as time went on there was no statistically significant difference between the outcome measures or revision rates for the two approaches.
Over 8000 total hip arthroplasties (THA) in the UK were revised in 2019, half for aseptic loosening. It is believed that Artificial Intelligence (AI) could identify or predict failing THA and result in early recognition of poorly performing implants and reduce patient suffering. The aim of this study is to investigate whether Artificial Intelligence based machine learning (ML) / Deep Learning (DL) techniques can train an algorithm to identify and/or predict failing uncemented THA. Consent was sought from patients followed up in a single design, uncemented THA implant surveillance study (2010–2021). Oxford hip scores and radiographs were collected at yearly intervals. Radiographs were analysed by 3 observers for presence of markers of implant loosening/failure: periprosthetic lucency, cortical hypertrophy, and pedestal formation. DL using the RGB ResNet 18 model, with images entered chronologically, was trained according to revision status and radiographic features. Data augmentation and cross validation were used to increase the available training data, reduce bias, and improve verification of results. 184 patients consented to inclusion. 6 (3.2%) patients were revised for aseptic loosening. 2097 radiographs were analysed: 21 (11.4%) patients had three radiographic features of failure. 166 patients were used for ML algorithm testing of 3 scenarios to detect those who were revised. 1) The use of revision as an end point was associated with increased variability in accuracy. The area under the curve (AUC) was 23–97%. 2) Using 2/3 radiographic features associated with failure was associated with improved results, AUC: 75–100%. 3) Using 3/3 radiographic features, had less variability, reduced AUC of 73%, but 5/6 patients who had been revised were identified (total 66 identified). The best algorithm identified the greatest number of revised hips (5/6), predicting failure 2–8 years before revision, before all radiographic features were visible and before a significant fall in the Oxford Hip score. True-Positive: 0.77, False Positive: 0.29. ML algorithms can identify failing THA before visible features on radiographs or before PROM scores deteriorate. This is an important finding that could identify failing THA early.
In revision knee arthroplasty, rotating hinge implants (RHK) have been considered to result in higher complication rates and lower survivorship when compared to constrained condylar implants (CCK). The aims of this study were to compare patient reported outcome measures (PROMs), complication rates and survivorship of RHK and CCK used in revision arthroplasty at a single, high volume elective orthopaedic centre with previously validated bespoke database. One hundred and eight patients who underwent revision knee arthroplasty with either CCK or RHK and matched our inclusion criteria were identified. EQ5D, Health State and Oxford Knee Scores were collected pre-operatively and at 1 year post-operatively. Complication data was collected at 6 weeks, 6 months, 1 year and 2 years post-operatively. NJR data was interrogated, in addition to our own database, to investigate implant survival.Abstract
Introduction
Methodology
Patient Reported Outcome Measures (PROMs) can be completed using paper and postal services (pPROMS) or via computer, tablet or smartphone (ePROMs). We have investigated whether there are differences in scores depending on the method of PROMs acquisition for the Oxford Knee (OKS) and the EQ-5D scores, at one and two years post operatively. Patient demographics, mode of preferred data collection and pre-and post-operative PROMs for Total Knee Replacements (TKRs) performed between 1st January 2018 and 31st December 2018 were collected. During the study period, 1573 patients underwent TKRs. The average OHS and EQ-5D pre-operatively scores was 19.47 and 0.40 respectively. 71.46% opted to undertake post-operative questionnaires using ePROMs. The remaining 28.54% opted for pPROMS. The one and two-year OHS for ePROMS patients increased to 37.64 and 39.76 while the OHS scores for pPROMS patients were 35.71 and 36.83. At the one and two-year post-operative time intervals, a Mann-Whitney test showed statistical significance between the modes of administration for OHS (P-Value = 0.044 and 0.01 respectively). The one and two-year EQ-5D for ePROMS patients increased to 0.76 and 0.78 while the EQ-5D scores for pPROMS patients were 0.73 and 0.76. The P-Value for Mann-Whitney tests comparing the modes of administration for EQ-5D were 0.04 and 0.07 respectively. There is no agreed mode of PROMs data acquisition for the OKS and EQ-5D Scores. While we have demonstrated an apparent difference in scores depending on the mode of administration, further work is required to establish the influence of potentially confounding factors.Abstract
Disease specific or generic Patient Reported Outcome Measures (PROMs) can be completed by patients using paper and postal services (pPROMS) or via computer, tablet or smartphone (ePROMs) or by hybrid data collection, which uses both paper and electronic questionnaires. We have investigated whether there are differences in scores depending on the method of PROMs acquisition for the Oxford Hip Score (OHS) and the EQ-5D scores, at one and two years post operatively. Patients for this study were identified retrospectively from a prospectively compiled arthroplasty database held at the study centre. Patient demographics, mode of preferred data collection and pre- and post-operative PROMs for Total Hip Replacements (THRs) performed at this centre between 1st January 2018 and 31st December 2018 were collected. During the study period, 1494 patients underwent THRs and had complete one and two-year PROMs data available for analysis. All pre-operative scores were obtained by pPROMS. The average OHS and EQ-5D pre-operatively scores were 19.51 and 0.36 respectively. 72.02% of the patients consented to undertake post-operative questionnaires using ePROMs. The remaining 27.98% opted for pPROMS. The one and two-year OHS for ePROMS patients increased to 41.31 and 42.14 while the OHS scores for pPROMS patients were 39.80 and 39.83. At the one and two-year post-operative time intervals, a Mann-Whitney test showed statistical significance between the modes of administration for OHS (P-Value =0.044 and 0.01 respectively). The one and two-year EQ-5D for ePROMS patients increased to 0.83 and 0.84 while the EQ-5D scores for pPROMS patients were 0.79 and 0.81. The P-Value for Mann-Whitney tests comparing the modes of administration for EQ-5D were 0.13 and 0.07 respectively. Within Orthopaedics, PROMs have become the most widely used instrument to assess patients’ subjective outcomes. However, there is no agreed mode of PROMs data acquisition. While we have demonstrated an apparent difference in scores depending on the mode of administration, further work is required to establish the influence of potentially confounding factors such as patient age, gender and familiarity with computer technology.
Clinical decision-making is often based on evidence of outcome after a specific treatment. Surgeons and patients may, have different perceptions and expectations of what to achieve following a Total Hip Replacement (THR). Several studies have shown that unfulfilled expectations are a principal source of patient dissatisfaction and patients are typically overly optimistic with regards to expected outcomes following surgery. Published data on clinical and functional outcomes show that persistence of symptoms, such as pain, and failure to return to preoperative levels of function are normal. To measure patient's expectations we undertook prospective study reviewing patients' expectations in 1800 THRs over a 21-year period (1997–2018). Of the whole cohort, 48.98% patients reported they wanted a THR to overcome unbearable pain. 11.75 % wanted a THR to be able to walk without a limp. 9.69% wanted to a THR to increase walk endurance. 61.97% reported it was extremely important to decrease pain following a THR. In 2001, the most important reason for a THR reported by patients was to relieve unbearable pain and this remained the same most important reason in 2018. This result was also statistically significant with a p-value of 0.001. 80.36% reported they anticipated ‘no pain’ after recovery from a THR, 16.75% reported they anticipated ‘some pain’ and 2.89% reported they anticipated ‘extreme pain’ following a THR. 74.71% reported it was extremely important to increase their ability to undertake normal activities. 22.06% reported it was very important, 2.40% reported it was moderately important, 0.55% slightly important and 0.28% reported it was not all to important to increase their ability to undertake normal activity. In conclusion patients' want to reduce their pain, walk normally and increase their level activities. Differences in expectation fulfilment may be due to unrealistic expectations. To achieve optimal outcome managing patient expectations is vital.
For total hip arthroplasty (THA), cognitive training prior to performing real surgery may be an effective adjunct alongside simulation to shorten the learning curve. This study sought to create a cognitive training tool to perform direct anterior approach THA, validated by expert surgeons; and test its use as a training tool compared to conventional material. We employed a modified Delphi method with four expert surgeons from three international centres of excellence. Surgeons were independently observed performing THA before undergoing semi-structured cognitive task analysis (CTA) before completing successive rounds of electronic surveys until consensus. The agreed CTA was incorporated into a mobile and web-based platform. Forty surgical trainees (CT1-ST4) were randomised to CTA-training or a digital op-tech with surgical videos, before performing a simulated DAA THA in a validated fully-immersive virtual reality simulator.Background
Methods
Patients need to know the benefits, risks and alternatives to any proposed treatment. Surgeons discussing the risk of a revision procedure becoming necessary, after a hip replacement can draw upon the orthopaedic literature and arthroplasty registries for long-term implant survival. However, early revision is required in a minority of cases. We have investigated the probability for revision hip replacement patients in terms of time-point and indication for revision. Of the 9,411 Primary Total Hip Replacements (THR), undertaken by 22 surgeons, over an eleven-year period, between January 2004 and March 2015, 1.70% (160) were subsequently reported to the National Joint Registry (NJR) as revised. Each revision case was reviewed under the supervision of senior hip specialist consultants. The modes of failure of were identified through clinical, laboratory and imaging (x-rays, CT, MRI and Isotope scans) studies. The revision rate for THRs was 0.58% in the first year. This was statistically higher than all subsequent years, P-Value <0.001. There was no statistical difference between any pair of subsequent years. Thereafter, the average revision rate was 0.30% per annum. The odds ratio for revision during the first post–operative year against the subsequent year average was 1.67. The indications for the early hip revisions in the first three years were infection, dislocation and peri-prosthetic fracture. The data from this study can help better inform patients of the revision rates after a primary THR and allow surgeons to develop implant surveillance strategies among high-risk patients.
Historically, the clinical performance of novel implants was usually reported by designer surgeons who were the first to acquire clinical data. Regional and national registries now provide rapid access to survival data on new implants and drive ODEP ratings. To assess implant performance, clinical and radiological data is required in addition to implant survival. Prospective, multi-surgeon, multi-centre assessments have been advocated as the most meaningful. We report the preliminary results of such a study for the MiniHip™femoral component and Trinity™ acetabular component (Corin Ltd, UK). As part of a non-designer, multi-surgeon, multi-centre prospective surveillance study to assess the MiniHip™stem and Trinity™ cup, 535 operations on 490 patients were undertaken. At surgery, the average age and BMI of the study group was 58.2 years (range 21 to 76 years) and 27.9 (range 16.3 to 43.4) respectively. Clinical (Harris Hip Score, HHS) and radiological review have been obtained at 6 months, 3 and 5 years. Postal Oxford Hip Score (OHS) and EuroQol- 5D (EQ5D) score have been obtained at 6 months and annually thereafter. To date, 23 study subjects have withdrawn or lost contact, 11 have died, and 9 have undergone revision surgery. By the end of March 2018, 6 month, 1, 2, 3, 4, and 5 year data had been obtained for 511, 445, 427, 376, 296 and 198 subjects respectively.INTRODUCTION
METHODS
We have investigated whether the pattern of subchondral acetabular cyst formation reflects hip pathology and may provide a prognostic indicator for treatment. A single surgeon series of sequential hip arthroscopies was reviewed to identify the most recent 200 cases undertaken on a previously un-operated joint with pre-operative plain radiographs and computed tomography or magnetic resonance scan available for review. Also, serial “non-arthritic hip scores” (NAHS) recorded pre-operatively, at 6 weeks and 3 months post-surgery. The acetabular Lateral Centre Edge Angle, the Acetabular Index, the FEAR index and the Kallgren and Lawrence grade were determined. All images were reviewed by two independent assessors and divided into four groups according to acetabular subchondral cyst distribution. No association was identified between gender and patient reported outcomes. SDC patients were significantly younger than the other three groups (p <0.001). At three months after surgery, the average increase of the NAHS in the four groups was 25.3, 23.5, 4.2 and 4.9 respectively. Acetabular dysplasia was identified in 72% of the SDC group compared to 18%, 16% and 33% in NC, SPC and MC groups. Degenerative change was identified in 86% of the MC group compared to 18%, 40% and 41% of the NC, SPC and SDC groups. The early patient reported outcome following hip arthroscopy was significantly affected by the location and number of acetabular subchondral cysts. A Solitary Dome Cyst is indicative of underling hip dysplasia. Multiple Cysts are indicative of degenerative disease. The majority of patients in these groups have poor three-month outcomes after hip arthroscopy.
Total Hip Replacement (THR) is widely assumed to resolve sleep disturbance commonly experienced by individuals with hip osteoarthritis (OA). We report a study of 329 THRs with mean age of 71.9 years comparing pre-operative and one and two year post-operative patient reported outcomes for sleep disturbance to determine the veracity of this expectation. Data was collected from the validated Oxford Hip Patient Reported Questionnaire. Specifically, Question 12: “During the past four weeks, have you been troubled by pain from your hip in bed at night?” Answers to the question were multiple choice: No nights (4 points), Only 1 or 2 nights (3 points), Some nights (2 points), Most nights (1 point) and Every Night (0 points) Pre-operatively, the mean score for patients with hip OA was 1.2/4. This increased to 3.5 at one year and was also maintained at two years. The pre- to post-operative improvement was significant at both one and two years for THR with p <0.00001. Pre-operatively, only 6% of patients with arthritic hips reported that they were never woken from sleep because of their painful hip. One year after THR 72% always enjoyed pain free sleeping and at two years this had risen to 75%. When patients who only experienced disturbance one or two nights per month were included, the three figures increased from 13% to 83% and 83% respectively. The study confirms that sleep disturbance affects over 90% of patients with arthritic hip joints. Over 80% of THR patients will enjoy sleep that is seldom or never disturbed by their artificial hip. The improvement achieved by THR occurs within a year of surgery and is preserved at two years. In this regard, hip replacement is a highly effective intervention.
Instability accounts for one third of revision total hip arthroplasty(rTHA) performed in the United Kingdom. Removal of well-fixed femoral stems in rTHA is challenging with a risk of blood loss and iatrogenic damage to the femur. The Bioball Universal Adaptor (BUA) (Merete, Germany), a modular head neck extension adaptor, provides a mechanism for optimisation of femoral offset, leg length and femoral anteversion. This can avoid the need for femoral stem revision in selected cases. There is a relative paucity of clinical data available with the use of this device. The aim of this study is to present the clinical results and rate of instability following revision with this head neck adaptor at a minimum of two years' follow up.Introduction
Aim
The Metasul articulation was introduced in the early 1990's. It comprises a 28mm forged, cobalt-chrome head and a forged metal inlay, set into the polyethylene element of the acetabular component. During the 1990's and early 2000's anatomic sized MoM articulations were re-introduced for hip resurfacing and stemmed implant designs. Adverse tissue reactions to metal debris and corrosion products subsequently led to a decline in MoM usage. Between January 1995 and December 1998, 133 hips underwent primary THR using the Metasul 28mm bearing. Patients were routinely sent an annual postal Oxford Hip Score (OHS) and radiographs were obtained from the second post-operative year. We have retrospectively reviewed the clinical and radiographic dataset following the 15 year follow-up time point.Introduction
Materials & Methods
This study examines variations in knee arthroplasty patient reported outcome measures according to patient age. We analysed prospectively collected outcome data (OKS, Eq5D, satisfaction, and revision) on 2456 primary knee arthroplasty patients. Patients were stratified into defined age groups (< 55, 55–64, 65–74, 75–84, and ≥85 years). Oxford Knee Score and Eq5D were analysed pre-operatively, and postoperatively at 6 months and 2 years. Absolute scores and post-operative change in scores were calculated and compared between age groups. Satisfaction scores (0–100) were analysed at 6 months post-operatively. Linear, logistic and ordinal regression modelling was used to describe the association between age and outcomes, for continuous, binary and ordinal outcomes, respectively. Kaplan-Meier analysis was performed to describe revision rates at 2 years.Objectives
Methods
Using general practitioner records, hospital medical notes and through direct telephone conversation with patients, we investigated the accuracy of nine patient-reported complications after elective joint replacement surgery of the hip and knee. A total of 402 post-discharge complications were reported after 8546 elective operations that were undertaken within a three-year period. These were reported by 136 men and 240 women with an overall mean age of 71.8 years (34.3–93.2). A total of 319 (79.4%; 95% confidence interval, 75.4%–83.3%) reported complications were confirmed to be correct. Very high rates of correct reporting were demonstrated for infection (94.5%) and further surgery (100%), whereas the rates of reporting deep venous thrombosis (DVT), pulmonary embolism, myocardial infarct and stroke were lower (75%–84.2%). Dislocation, periprosthetic fractures and nerve palsy were associated with modest rates of correct reporting (36%–57.1%). More patients who had had knee surgery delivered incorrect reports of dislocation (p = 0.001) and DVT (p = 0.013). Despite these variations in accuracy, it appears that post-operative complications may form part of a larger patient-reported outcome programme for monitoring outcome after elective joint replacement surgery.
Total hip arthroplasty (THA) is undertaken to relieve pain and to restore mobility. The orthopaedic community remains divided on the influence of surgical approach in achieving functional recovery most quickly and effectively. We report a study comparing THA performed through a posterior (Posterior) against anterior approach (Heuter). Fifty patients were prospectively enrolled and randomized for Posterior or Heuter procedures. Informed patient consent and local ethics approval was obtained. All patients received an uncemented, ceramic-on-ceramic prosthesis performed by a single surgeon. Functional outcome was assessed by time to achieve milestones of walking, stair climbing, hip movement and balance. Kinematic data on level-ground walking and the effect of fatigue was assessed using a portable gait analysis system at 6-, 12-, and 24-weeks post-operatively.Introduction
Methods
The outcomes programme of our institution has been developed from a system first used at Epsom and St Helier NHS Trust 15 years ago. The system was implemented at our institution when it opened in 2004, and has been used to collect data on over 17,000 joint replacement operations so far. A bespoke database is used to collect, analyse and report outcome data. An integrated system allows the collection of patient-reported outcome measures (PROMS), patient satisfaction scores, radiological assessment, and medical or surgical complications. Functionality allows the transfer of data from existing clinical management programmes, and the generation of customised letters and questionnaires to send to patients. Analysis of data and report production is fully automated. Data is collected pre-operatively, during the inpatient stay, and post-operatively at 6 weeks, 6, 12 and 24 months. Results are disseminated to the surgeons, the senior management team and the Clinical Governance Committee.Introduction
Methods
The MITCH PCR is an anatomic, flexible, horse-shoe shaped acetabular component, with 2 polar fins. The rationale of the PCR cup design is to reproduce a near-physiological stress distribution in the bone adjacent to the prosthesis. The thin composite cup is designed to fuse and flex in harmony with the surrounding bony structure. Only the pathological acetabular cartilage and underlying subchondral bone of the horseshoe-shaped, load-bearing portion of the acetabular socket is replaced, thus preserving viable bone stock. The PCR is manufactured from injection moulded carbon fibre reinforced polyetheretherketone (PEEK), with a two layer outer surface comprising hydroxyapatite and plasma sprayed commercially pure titanium. It is implanted in conjunction with a large diameter low wear femoral head, producing a bearing that will generate minimal wear debris with relatively inert particles. Pre-clinical mechanical testing, finite element analysis and biocompatibility studies have been undertaken. FEA evaluation predicts preservation of host bone density in the load bearing segments. A pilot clinical study was completed on a proto-type version of the PCR cup (the “Cambridge” cup), achieving excellent 5 and 10 year results. We report the three-year results from a two-centre, prospective clinical evaluation study of the MITCH PCR cup. Patient outcome has been assessed using standardised clinical and radiological examinations and validated questionnaires. The change in physical level of activity and quality of life has been assessed using the Oxford Hip Score, Harris Hip score and the EuroQol-5D score, at scheduled time-points. Serial radiographs have been analysed to monitor the fixation and stability of the components.Introduction
Subjects and Methods
The need for the stringent surveillance of new devices was recognised by the NICE review of hip replacement surgery in 2000 and led to the Orthopaedic Data Evaluation Panel (ODEP) developing criteria for post-marketing surveillance (PMS) studies. This requirement has been reinforced by the recent recall of ASR devices. The South West London Elective Orthopaedic Centre's (EOC's) comprehensive outcomes programme has been adapted to manage and coordinate multi-centre, multi-surgeon, PMS studies. The system allows any schedule and combination of patient-reported outcome measures (PROMS), clinical and radiological assessments, and complications to be collected. Typically, PROMS are collected pre-operatively and yearly by post. Baseline clinical assessment is undertaken pre-operatively, with baseline radiological assessments pre- and post-operatively. Subsequent clinical and radiological assessments are usually obtained at the ODEP-mandated time points of 3, 5, 7 and 10 years post-operatively. Patients are telephoned twice yearly to document complications and any impending change of address.Introduction
Methods
Femorotibial malalignment exceeding ±3° is a recognised contributor of early mechanical failure after total knee replacement (TKR). The angle between the mechanical and anatomical axes of the femur remains the best guide to restore alignment. We investigated where the femoral head lies relative to the pelvis and how its position varies with respect to recognised demographic and anatomic parameters. We have tested the hypothesis of the senior author that the position of the centre of the femoral head varies very little, and if its location can be identified, it could serve to outline the mechanical axis of the femur without the need for sophisticated imaging. The anteroposterior standing, plain pelvic radiographs of 150 patients with unilateral total hip replacements were retrospectively reviewed. All patients had Tönnis grade 0 or 1 arthritis on the non-operated hip joint. All radiographs were obtained according to a standardised protocol. Using the known diameter of the prosthetic head for calibration, the perpendicular distance from the centre of the femoral head of the non-operated hip to the centre of pubic symphysis was measured with use of TraumaCad software. Anatomic parameters, including, but not limited to, the diameter of the intact femoral head, were also measured. Demographic data (gender, age, height, weight) were retrieved from our database.Introduction
Patients & Methods
To examine the clinical characteristics of patients undergoing knee arthroplasty with a pre-operative Oxford Knee Score >34 (‘good’/‘excellent’), and assess the appropriateness of surgical intervention for this group. In the current cost-constrained health economy, justification of surgical intervention is increasingly sought. As a validated disease-specific outcome measure, the pre-operative Oxford Knee Score (OKS) has been suggested as a possible threshold measurement in knee arthroplasty. However, contrary to expectations, analysis of pre-operative OKS in the joint registry population demonstrates a normal distribution curve with a sub-group of high-scoring patients. This suggests that either the baseline OKS does not accurately define surgical threshold, or that patients with a high OKS are inappropriately having knee replacements.Purpose
Background
The Oxford Knee Score (OKS) is a validated and widely used PROM that has been successfully used in assessing the outcome of knee arthroplasty (KA). It has been adopted as the nationally agreed outcome measure for this procedure and is now routinely collected. Increasingly, it is being used on an individual patient basis as a pre-operative measure of osteoarthritis and the need for joint replacement, despite not being validated for this use. The aim of this paper is to present evidence that challenges this new role for the OKS. We have analysed pre-operative and post-operative OKS data from 3 large cohorts all undergoing KA, totalling over 3000 patients. In addition we have correlated the OKS to patient satisfaction scores. We have validated our findings using data published from the UK NJR.Purpose
Method
The Oxford Knee Score (OKS) is a valid and reliable self-administered patient questionnaire that enables assessment of the outcome following total knee replacement (TKR). There is as yet no literature on the behavioral trends of the OKS over time. Our aim is to present a retrospective audit of the OKS for patients who have undergone TKR during the past ten years. We retrospectively analysed 3276 OKS of patients who had a primary TKR and had been registered as part of a multi-surgeon, outcome-monitoring program at St. Helier hospital. The OKS was gathered pre-operatively and post-operatively by means of postal questionnaires at annual intervals. Patients were grouped as per their age at operation into four groups: 60, 61-70, 71- 80 and >80. A cross-sectional analysis of OKS at different time points was performed. The numbers of OKS available for analysis were 504 pre-operatively, 589 at one-year, 512 at two-year and gradually decreasing numbers with 87 knees ten-year post-operatively. There was as expected a significant decrease (improvement) of the OKS between pre-operative and one-year post-operative period and then reached a plateau. Beyond eight years, there is a gradual rise in the score (deterioration). The younger patients (60) showed a significant increase in their average OKS between one and five-years post-operatively. However beyond five years, they followed the trend of their older counterparts. When the twelve questions in the OKS were analysed, certain components revealed greater improvement (e.g. description of knee pain and limping) than others (e.g. night pain). The OKS is seen to plateau a year after TKR. According to the OKS the outcome of the TKR is not as good in the younger age group as compared to the older age group. Further investigation is required to ascertain the cause of this observed difference.
The performance of total knee arthroplasty in deeply flexed postures is of increasing concern as the procedure is performed on younger, more physically active and more culturally diverse populations. Several implant design factors, including tibiofemoral conformity, tibial slope and posterior condylar geometry have been shown directly to affect deep flexion performance. The goal of this study was to evaluate the performance of a fixed-bearing, asymmetric, medial rotation arthroplasty design during kneeling activities. Thirteen study participants (15 knees) with primary total knee arthroplasty (Medial Rotation Knee, Finsbury, Surrey, UK) were observed while doing a step activity and kneeling on a padded bench from 90° to maximum comfortable flexion using lateral fluoroscopy. Subjects averaged 74 years of age and nine were female. Subjects were an average of 17 months post-operative, and scored 94 points on the International Knee Score and 99 on the Functional Score. Digitised fluoroscopic images were corrected for geometric distortion and 3D models of the implant components were registered to determine the 3D position and orientation of the implants in each image. During the step activity, the medial and the lateral femoral contact point stayed fairly constant with no axial rotation from 0 to 100° of flexion. At maximum kneeling flexion, the knees exhibited 119° of implant flexion (101°-139°), 7° (-7° to 17°) tibial internal rotation, and the lateral condyle translated backwards by 11 mm. Patients with medial rotation knee arthroplasty exhibited medial pivot action with no paradoxical translation. The knees exhibited excellent kneeling flexion and posterior translation of the femur with respect to the tibia. The axial rotation in MRK was within the range of normal knee kinematics from -10 to 120 (perhaps 140).
To establish the cost of primary hip (THR) and knee (TKR) arthroplasty in an elective orthopaedic centre in the UK and to compare it with current government reimbursement to NHS hospitals and the costs in North America. In 2004 an elective orthopaedic centre was set up in South West London which performs mainly primary lower limb arthroplasty. We used a retrospective analysis of financial statements from September 2004-June 2005 inclusive to establish operative costs (including implant), perioperative costs and post-operative costs until discharge.Aims
Methods
Patient demographics were similar between both groups. There was no significant difference in intra-operative blood loss between both groups. The early post-operative blood loss and total blood loss were significantly less in the tranexamic acid group. This effect of tranexamic acid was more significant in females who showed a dose-related relationship between tranexamic acid dose and blood loss. Fewer patients in the tranexamic acid group required blood transfusion. There was no increased incidence of DVT in the tranexamic acid group. The use of a single pre-operative 1g bolus of tranexamic acid administered before surgery is a safe, cost-effective method of reducing post-operative blood loss following total hip arthroplasty. The effect is more significant in females at this dose.
The HA coated implants remained asymptomatic. Three uncoated components required revision for migration. No evidence of accelerated UHMWPE wear was seen on retrievals or radiographs. Histological analysis of the retrieved HA coated specimens showed excellent bony fixation, uncoated cups showed predominantly fibrous tissue.
Publication of normal and expected outcome scores is necessary to provide a benchmark for auditing purposes following arthroplasty surgery. We have used the Oxford knee score to monitor the progress of knee replacements undertaken since 1995, the start of our review programme. 4847 Oxford assessments were analysed over an 8 year follow-up period. The mean pre-operative Oxford knee score was 39.2, all post-operative reviews showed a significant improvement. Patients with a BMI >
40, and the under 50 age group showed early deterioration in outcome scores, returning to pre-operative levels by 5 and 7 years respectively. There was no significant difference in outcome between surgeons performing <
20 knee replacements a year and those performing >
100 / year. The age of the patient at the time of surgery and the pre-operative body habitus have been identified as factors affecting long term outcome of total knee replacement surgery. Awareness of these factors may assist surgeons in advising patients of their expected outcomes following surgery.
Sectioned femoral components retrieved from failed hip resurfacing arthroplasties show resorption of proximal femoral bone or formation of a fibrous membrane at the bone cement interface. Our study uses Finite Element Analysis (FEA) to examine the effects of the implant orientation on bone remodelling following hip resurfacing arthroplasty. A radiographic analysis of the proximal femur following hip resurfacing was conducted in order to draw a comparison to the FEA findings. A 3D FEA model of the Birmingham Hip Resurfacing (BHR) was created based on the geometry and material properties of a 45 year-old female donor hip. Hip joint and muscle loads were applied. Bone remodelling stimuli was determined using changes in strain energy. A range of implant orientations were compared to study the affect on bone remodelling. A retrospective radiological analysis was undertaken on 100 hips with a minimum of 5 years follow up. Femoral neck diameter was measured at post-op, 2 and 5 years, as well as neck and stem shaft angles. FEA showed that valgus orientation was associated with increased resorption underneath the shell. Varus orientation showed increased bone formation at the stem tip. The radiological analysis identified 2 distinct patterns of neck thinning. Slow thinners (76%) had <
5% reduction in neck diameter at 2 years and <
10% at 5 years. Rapid thinner (24%) had >
5% thinning at 2 years and >
10% at 5 years. The mean percentage reduction in neck diameter was significantly different between the two groups at the two time points (p<
0.01). The rapid group had a higher proportion of valgus aligned implants (88%) and a significant decrease in reconstructed offset (p=0.0023). The FEA results have shown that stem alignment can affect bone resorption resurfacing. FEA results were consistent with the radiological findings. Additional retrieval studies are necessary to help understand aetiology of implant failures.
Adverse bone remodeling in the proximal femur may be detrimental to the long term survival of resurfacing prosthesis. Bone resorption beneath the femoral shell and thinning of the femoral neck have been observed. We present a radiological analysis of the incidence, rate, site of neck thinning and changes observed within the femoral neck, in 100 cases, with a minimum of five years follow-up. Femoral neck diameter was measured at zero, two and five years post-operatively, at the head neck junction and five mm distally. Pre and post-operative head to neck ratios, natural and reconstructed offset, femoral neck-shaft and stem-shaft angles and cup inclination angle were measured. Two distinct patterns of neck thinning were observed. In 76 cases (slow thinning group), we observed a reduction of <
5% of original neck diameter at two years and <
10 % at five years (mean 1.5%, sd+/− 1.5). In 24 cases (rapid thinning group), a reduction of >
5% of original neck diameter at two years and >
10% at five years (mean 10.4%, sd+/− 4.8) was observed. The difference in the percentage reduction in neck diameter was significantly different between the two groups at both time points (p<
0.01). Larger head-neck ratios were observed in the rapid thinning group, both pre and post operatively (p<
0.01). The viability of bone underneath the femoral head may be compromised as a consequence of a non-physiological bone loading mechanism. FEA has predicted stress shielding underneath the femoral head and loading of the mini stem. Compromised blood supply of the retained epiphyseal remnant may play a part in femoral head resorption. Femoral neck thinning is a phenomenon of unproven aetiology which affects almost 25% of our resurfacing cases.
The patients were divided into 5 groups based on their BMI, BMI<
25(normal), 25–29.9(overweight), 30–34.9(obese), 35–39.9(moderately obese), 40 or more(morbidly obese). BMI <
25 was treated as a control group for comparison. Statistical analysis was done using t test.
The potential for bone remodeling in the proximal femur may be detrimental to the long term survival of resurfacing prosthesis. A retrospective analysis of radiological changes in the femoral neck was undertaken for 96 patients (100 hips, 76 males and 24 females), with a minimum of 5 years following hip resurfacing. The mean age at surgery was 53.8 years. Femoral neck diameter was measured post-operatively, at 2 and 5 years. Pre and post-operative head to neck ratios, femoral head-shaft offset, femoral neck and implant stem-shaft angles were also measured. Two groups of patients were identified with differing rates of reduction in their femoral neck diameter. Over the first 2 years, Group A (24%) mean reduction was 2.02mm/year while Group B (76%) mean reduction was 0.33 mm/year. At 5 years, the Group A mean reduction was 5.64mm (sd±2.03mm) while Group B reduction was 1.16mm, (sd±0.97mm). The difference was significant at both time points (p<
0.01). Larger head-neck ratios were observed in the group A, both pre and post operatively (p<
0.01). Finite Element Analysis has predicted stress shielding underneath the femoral head and loading of the mini stem. This may explain bone resorption underneath the shell and remodeling around the mini stem. Compromised blood supply of the retained epiphyseal remnant may also play a part in femoral head resorption. Group A with a larger proportion of females and femoral heads will potentially have a larger proportion of epiphyseal remnant retained. A further mechanism that could be influential in the development of neck thinning and bone resorption may be due to fluid pumping mechanism causing osteolytic erosion at the bone cement interface. In conclusion, femoral neck thinning is a phenomenon of unproven aetiology which is affecting almost 25% of our resurfacing cases. Further investigations are needed to determine its aetiology and remedy.
As there had been no previous studies correlating the two scoring systems, we investigated whether a correlation exists between the two scores at 2, 5 and 10 year periods. A correlation would allow us to determine what OKS value would achieve 90% sensitivity in identifying patients requiring clinical review at the above time points. This strategy would reduce the number of clinical visits required and its associated cost.
We recommend that at 2 years, all patients complete an OKS questionnaire and if this is above 24, a clinical evaluation maybe required. Using this OKS value as a screening technique would allow a reduction of up to 50% in clinic visits and outpatient costs at the 2 year follow-up. This reduction is not as great at the 5 and 10 year periods. At these time periods, we recommend a clinical follow-up.
Computer navigation assistance in total knee arthroplasty (TKA) results in more consistently accurate postoperative alignment of the knee prostheses. However the medium and long term clinical outcomes of computer-navigated TKA are not widely published. Our aim was to compare patient perceived outcomes between computer navigation assisted and conventional TKA using the Oxford knee score (OKS). We retrospectively collected data on 441 primary TKA carried out by a single surgeon in a dedicated arthroplasty centre over a period of four years. These were divided according to use of computer navigation (group A) or standard instrumentation (group B). There were no statistical differences in baseline Oxford knee score (OKS) and demographic data between the groups. 238 of these had at least a one-year follow-up with 109 in group A and 129 in group B. Two year follow-up data was available for 105 knees with 48 in group A and 57 in group B and a three year follow-up for 45 with 21 and 24 in groups A and B respectively. 12 patients had completed four year follow-up with seven and five knees in groups A and B respectively. The mean OKS at 1-year follow up was 24.98 (range 12– 54, SD 9.34) for group A and 26.54 (range 12– 51, SD 10.18) for group B (p = 0.25). Similarly at 2-years the mean OKS was 25.40 (range 12– 53, SD 9.51) for group A and 25.56 (range 12– 46, SD 9.67) for group B (p = 0.94). The results were similar for three and four-year follow ups with p values not significant. This study thus revealed that computer assisted TKA does not appear to result in better patient satisfaction when compared to standard instrumentation at midterm follow up. It is known from long term analysis of conventional TKA that mal-aligned implants have significantly higher failure rates beyond eight to ten years. As use of computer navigation assistance results in a less number of mal-aligned knee prostheses, we believe that these knees will have improved survivorship. The differences in OKS between the two groups should therefore be evident after eight to ten years.
To compare tourniquet times of standard and computer assisted total knee arthroplasty in patients with BMI more than 30 To evaluate the change in this variable as a surgeon gained experience over a three year period.
Group1 had average tourniquet times of 95.69 and 111.67 minutes in the standard and computer assisted groups respectively (p 0.01). Group 2 tourniquet times were 80.75 and 92.33 minutes (p 0.05). Group 3 tourniquet times were 84.5 and 87.5 minutes; these were not significantly different.
There has been renewed interest in metal-on-metal bearings as hip resurfacing components for treatment in young, active patients. This study examines the effects of fixation (cemented or uncemented heads) and bone-implant interface conditions (stem-bone and head-bone) on the biomechanics of the Birmingham hip resurfacing (BHR) arthroplasty, using high resolution, 3-d computational models of the bilateral pelvis from a 45-year-old donor. Femoral bone stress and strain in the natural and BHR hips were compared. Bone remodelling stimuli were also determined for the BHR hips using changes in strain energy. Proximal femoral bone stress and strain were non-physiological when the BHR femoral component was fixed to bone. The reduction of strain energy within the femoral head was of sufficient magnitude to invoke early bone resorption. Less reduction of stress was demonstrated when the BHR femoral component was completely debonded from bone. Bone apposition around the distal stem was predicted based on the stress and strain transfer through the stem. Femoral stress or strain patterns were not affected by the type of fixation medium used (cemented vs. Uncemented). Analysis of proximal stress and strain shielding in the BHR arthroplasty provides a plausible mechanism for overall structural weakening due to loss of bony support. It is postulated that the proximal bone resorption and distal bone formation may progress to neck thinning as increasing stress and strain transfer occurs through the stem. This may be further exacerbated by additional proximal bone loss through avascular necrosis. Medium term retrieval specimens have shown bone remodelling that is consistent with our results. It is unclear if the clinical consequences of neck thinning will become more evident in longer-term follow-ups of the BHR.
One potential limitation with uncemented, hemispherical metal-backed acetabular components is stress shielding of bony structures due to the mismatch in elastic modulus between the metal backing and the peri-prosthetic bone. A proposed substitute is a horseshoe-shaped acetabular component, which replicates the bony anatomy. One such device, the Cambridge cup, has shown successful clinical and radiological outcomes at five years follow-up (Brooks 2004, Field 2005). We conducted a study of the Cambridge cup from a biomechanical perspective, using validated, high-resolution computational models of the bilateral hip. Peri-prosthetic stress and strain fields associated with the Cambridge cup were compared to those for the natural hip and a reconstructed hip with a conventional metal-backed hemispherical cup during peak gait loading. We found that the hemispherical cup caused an unphysiologic distribution of bone stresses in the superior roof and unphysiologic strain transfer around the acetabular fossa. These stress distributions are consistent with bone remodelling. In contrast, the peri-acetabular stresses and strains produced by the Cambridge cup differed from the natural hip but were more physiologic than the conventional hemispherical design. With the Cambridge cup, stresses in the superior acetabular roof, directly underneath the central bearing region, were greater than with the conventional design. Despite the thin bearing, the peak liner stresses in the Cambridge cup (max. tensile stress: 1.2 MPa; yield stress: 4.5 MPa) were much lower than the reported material strengths. Fossa loading by the hemispherical cup has been suggested as a possible mechanism for decreased implant stability (Widmer 2002). Conversely, the Cambridge cup produced semi-lunar peri-prosthetic stress fields, consistent with contact regions measured in natural hips (Widmer 2002). These analyses provide a better understanding of the biomechanics of the reconstructed acetabulum and suggest that a change in component geometry may promote long-term fixation in the pelvis.
Operation data is now entered onto the database by the surgeon or co-ordinator at the time of surgery. Thereafter, the database automatically produces annual Oxford Hip Questionnaires, EQ-5D questionnaires and invite letters to patients for clinical review at stipulated time-points. Questionnaires are returned by patients and scanned. This data is then electronically imported to the database without transcription error. Patients attend special Outcome clinics, staffed by Research Fellows and SpR’s, who examine the relevant hip and review their radiographs. The findings are recorded and the paper forms scanned and imported into the database. Non-responders are identified from the database and are chased up via telephone by the coordinator. Data is extracted from the database with queries and presented using database reports.
We report a three year Medical Devices Agency and Local Ethical Committee approved prospective study for a new tri-tapered polished cannulated cemented femoral component. Our stem was implanted in 53 primary total hip replacements. Eleven male patients (11 hips) and 39 female patients (39 hips). The mean age at surgery was 73 (range 65 to 84). The mean weight was 71.76 kg (range 49.3 kg to 94.6 kg) with a mean BMI of 28 (range 20.20 to 40.26). All patients had a pre operative diagnosis of osteoarthritis. All the hips were implanted via the anterolateral approach. Twenty-six (51%) hips were implanted by a single consultant and 24 (49%) were implanted by six different registrars. Pre-operative and sequential post-operative clinical and radiological evaluations were undertaken. The mean pre-operative Oxford hip score was 47 points.which declined 19 points at three years. Radiological analysis, using the Johnston criteria, did not reveal any untoward features. Prosthetic stem migration was measured using a technique developed in our unit and validated as accurate to 0.61 mm; as previously reported. Stem migration measured averaged 1.38 mm (n=52; sd ±1.38) 6 months post implantation. This progressed to 1.71 mm (n=50; SD=1.18) at one year; 1.61mm (n=48; sd ±1.17) at 2 years. and 1.55 mm (n=28; SD 1.13). At 3 years average stem migration for hips implanted by the registrar group and the consultant group was not sig-nificantly different (p=0.2048) and the migration curve, against time was similar for both groups. Our study has demonstrated initial component migration, comparable to that of other polished tapered cemented stem designs. The improvement in Oxford hip score parallels other reported series and no adverse radiological signs have been observed. Long-term surveillance of our cohort will provide further data to compare the new design with substantial equivalents. More sophisticated studies, such as RSA analysis would provide further data on early femoral component migration.
Radiographic results showed no evidence of loosening of HA coated cups, in contrast to non HA coated cups which migrated significantly in 80% of cases. Four patients with loose non HA coated cups underwent revision surgery.
Hip resurfacing is widely recognised as a bone conserving procedure with respect to proximal femoral resection. However, it has been argued that this is not the case for the acetabulum due to the thickness of the acetabular component and the large diameter bearing surfaces. We have investigated whether the Birmingham Hip is a bone conserving procedure with respect to the acetabular bone stock. Data was obtained from 257 consecutive Midland Medical Technology (MMT) surface replacements and 458 primary hybrid total hip replacements implanted under our care. The surface replacement group comprised 185 males (185 hips) and 72 females (72 hips) with a mean age at surgery of 55 years. The hybrid primary total hip replacement group comprised 207 males (207) and 251 females (251 hips). The mean age at surgery was 65 years old. In the surface replacement group the mean uncemented acetabular size implanted was 54.88 mm (females = 51.9 mm; males = 57.8 mm). In the hybrid primary total hip replacement group the mean uncemented acetabular size of 55.04 mm (females =52.9 mm; males = 57.2 mm). Statistical analysis was undertaken to compare the uncemented acetabular sizes in the surface replacement group with the uncemented acetabular sizes implanted in the primary hybrid total hip replacement group. We report no significant difference in the size of acetabular component used for the two groups (p = 0.4629; 95% C.I. −0.28 to 0.61). The effect of gender was analysed and the mean size of uncemented acetabular component implanted in males for the surface replacement group was not significantly different (p = 0.06) to the hybrid primary total hip replacement group. However the mean size of uncemented acetabular component in females for the surface replacement group was significantly smaller (p = 0.016) compared to the primary total hip replacement group. We conclude hip resurfacing is not bone sacrificing on the acetabular bone stock and can be bone conserving for females.
The novel horseshoe shaped cup was designed by the senior authors to minimise the resection of healthy bone in total hip arthroplasty. It replaces the cartilage and underlying sub-chondral bone of the acetabulum socket with a cup that is designed to flex in harmony with the surrounding bony structure. Fifty female patients with a displaced, subcapital, femoral neck fractures were chosen for the study. In half of the group of patients, the composite support shell was coated with HA, with the other half remaining uncoated. Clinical and radiological assessments were undertaken regularly for five years. To date 20 patients have died and 13 have withdrawn from the study due to poor medical health unrelated to the study. Charnley modified Merle d’Aubigne score at five years was as good as the preoperative score with 80% of patients having full range of movement, no pain and walking unaided. Radiographic results showed no evidence of loosening of HA coated cups, in contrast to non HA coated cups which migrated significantly in 80% of cases. Four patients with loose non HA coated cups underwent revision surgery. This trial has demonstrated success at 5 years with the HA coated Cambridge Acetabular Cup. Cups from which HA coating has been removed have migrated significantly in 80% of cases. There is an advantage of the HA fixation which will be taken into account before wider clinical usage is advocated.