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Purpose Unicompartmental knee arthroplasty (UKA) is an effective treatment for late knee osteoarthritis (OA). Young age ( Methods The primary objective was to compare the UKA revision rate in young patients with that of old patients, using the age thresholds of 60 and 55 years. Secondary objectives were patient-reported outcome measures (PROMs) and implant design. Five databases were searched in December 2021 for original comparative studies with a minimum of 1-year follow-up. No restrictions were placed on the type of UKA prosthesis. Results A total of 11 observational studies with 6130 knees were included. A mean MINORS score of 19 was assigned to the review. The mean age of patients was 64 years, with average follow-up of 7.5 ± 2.98 years. There was no significant difference in revision rate, incident or PROMs between young and old patients in the analysis for each age threshold. Further sub-analysis adjusting for implant type in mobile- and fixed-bearing prostheses also showed similar results between those above and under 60 and 55 years. Conclusion Young age was not associated with a higher revision rate or lower functional scores. Thus, this review provides evidence that age alone is not a contraindication to UKA, but the surgical choice must be based on several elements, and this finding should be applied in context, given the binary division and heterogeneity of patients. Level of evidence III.

Background Isolated lateral compartment knee arthritis is less prevalent than medial. While the reported results of medial unicompartmental knee replacement (UKR) have been good and comparable to total knee replacement, the results of lateral UKR have been mixed. We present the short-term results and survivorship of a fixed-bearing UKR designed specifically for the lateral compartment. Methods We report the result of 130 primary fixed-bearing lateral Oxford (FLO) UKRs (123 patients) performed between 2015 and 2019 with a minimum follow-up of 1 year. The indications for lateral UKR were: isolated lateral osteoarthritis (n = 122), post-trauma (n = 5) and osteonecrosis (n = 3). The mean age was 69.1 (± 11.6), mean BMI 28.4 (± 4.9), 66.9% female, 60% right-sided, and mean follow-up 3 (range 1–4.8 years, standard deviation ± 1) years. The primary outcome measure was the Oxford knee score (OKS). Survival analysis was performed with “revision for any reason”, “reoperation”, and “implant failure” as the endpoints. Results Six patients died from unrelated reasons. None of the implants failed. One required the addition of a medial UKR for medial arthritis. There were no other reoperations. At 4 years, the survival for implant failure was 100% and for both revision and all reoperations was 99.5% (95% CI 96.7–99.9%). At the last review, at a mean of 3 years, the mean Oxford knee score was 41. Conclusion The good survivorship and outcome scores suggest that UKR designed for the lateral compartment is an excellent alternative to total knee replacement in selected patients with isolated lateral tibiofemoral arthritis at short-term follow-up.

Objectives To estimate threshold prices for computer- and robot-assisted knee and hip replacement. Methods A lifetime cohort Markov model provided the framework for analysis. Linked primary care and inpatient hospital records informed estimates of outcomes under current practice. Outcomes were estimated under a range of hypothetical relative improvements in quality of life if unrevised and in revision risk after computer or robot-assisted surgery. Threshold prices, a price at which the net health benefit from funding the intervention would be zero, for these improvements were estimated for a cost-effectiveness threshold of £20 000 per additional quality-adjusted life-year (QALY) gained. Results For average patient profiles under current knee and hip replacement practice, lifetime QALYs were 10.3 (9.9 to 10.7) and 11.0 (10.6 to 11.4), with costs of £6060 (£5947 to £6203) and £6506 (£6335 to £6710) for knee and hip replacement, respectively. A combined 50% relative reduction in risk of revision and 5% improvement in postoperative quality of life if unrevised would, for example, result in QALYs increasing to 10.9 (10.4 to 11.3) and 11.6 (11.2 to 12.0), and costs falling to £5880 (£5816 to £5956) and £6258 (£6149 to £6376) after knee and hip replacement, respectively. These particular improvements would have an associated threshold price of £11 182 (£10 691 to £11 721) for knee replacement and £12 134 (£11 616 to £12 701) for hip replacement. The 50% reduction in revision rate alone would have associated threshold prices of £1094 (£788 to £1488) and £1347 (£961 to £1842), and the 5% improvement in quality of life alone would have associated threshold prices of £9911 (£9476 to £10 296) and £10 578 (£10 171 to £10 982). Conclusions At current prices, computer- and robot-assisted knee and hip replacement will likely need to lead to improvements in patient-reported outcomes in addition to any reduction in the risk revision.

The unexpected high revision rates of large-diameter (femoral head sizes of 36 mm or greater) metal-on-metal hip arthroplasties (MoMHAs) have led to worldwide regulatory authorities recommending regular surveillance, even for asymptomatic individuals. However, these recommendations are not evidence-based and are very costly. The rapidly evolving evidence base requires an update regarding the investigation and management of MoMHA patients. This article is the first of 2 (the second article in this series will consider the threshold for performing revision, and the outcomes following ARMD revision surgery: Matharu et al., Revision surgery of metal-on-metal hip arthroplasties for adverse reactions to metal debris: A clinical update. Acta Orthop 2018; in press), and considers the various investigative modalities used during surveillance, with specific focus on blood metal ion sampling and cross-sectional imaging. No single investigation can universally be used during MoMHA patient surveillance. Recent studies have now provided important information on interpreting blood metal ions (effective in identifying patients at low risk of problems), clarifying the roles of cross-sectional imaging (reserve combined ultrasound and MARS-MRI for complex cases), and providing parameters to safely exclude many asymptomatic patients from regular surveillance. This information will be useful when designing future surveillance protocols for MoMHA patients.

Objectives: In total hip arthroplasty the restoration of hip offset (HO) determines abductor muscle function and is considered essential in order to prevent adverse events such as impingement, dislocation and wear. The objectives of the present study were to (1) evaluate the accuracy and reliability[for full text, please go to the a.m. URL], Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2019)

Background and purpose — A risk-stratification algorithm for metal-on-metal hip arthroplasty (MoMHA) patients was devised by US experts to help clinicians make management decisions. However, the proposed algorithm did not cover all potential patient or surgical abnormalities. Therefore we adapted the US risk-stratification algorithm in MoMHA patients revised for adverse reactions to metal debris (ARMD) to determine the variability in the revision threshold, and also whether high-risk patients had inferior outcomes following revision. Patients and methods — We analysed 239 MoMHA revisions for ARMD between 2001 and 2016 from 2 centres with pre-revision blood metal ions and imaging. Patients were stratified (low risk, moderate risk, high risk) using pre-revision factors (implant, radiographic, blood metal ions, cross-sectional imaging) by adapting a published algorithm. The risk categories for each factor were assessed against revision year, revision centre, and post-revision outcomes (re-revision surgery, and any poor outcome). Results — Compared with hips revised before 2012, hips revised from 2012 onwards included more high-risk implants (44% vs. 17% pre-2012), high-risk radiographic features (85% vs. 69% pre-2012), and low-risk metal ions (41% vs. 19% pre-2012). 1 centre more frequently revised patients with high-risk implants (48% vs. 14%) and low-risk blood metal ions (45% vs. 15%) compared with the other. All these comparisons were statistically significant (p < 0.05). With the limited sample size available, implant, radiographic, blood metal ion, and cross-sectional imaging risk groups did not statistically significantly affect the rates of re-revision surgery or frequency of poor outcomes post-revision. Interpretation — When applying the adapted risk-stratification algorithm the threshold for ARMD revision changed over time, presumably due to increasing evidence, patient surveillance, and investigation since 2012. Lower blood metal ion thresholds were used from 2012 for ARMD revisions; however, there was evidence that centres attached different importance to metal ions when managing patients. High-risk patients did not have inferior outcomes following ARMD revision.

The motion of image edge detectors is used to infer 3D scene information by simultaneously solving the aperture and structure-from-motion problems. It is shown how additional constraints or information are required and two formal solutions are given. In one the motion of edge features at eight or more image points is used to solve for the motion and surface parameters (the 8-point algorithm). In the other it is assumed that the motion is known as a priori (the 3-point algorithm). This algorithm is used to illustrate the numerical stability of these solutions.

Aims and objectives: To explore the patients' perspective of surgery and early recovery when undergoing lower limb (hip or knee) arthroplasty. Background: Lower limb arthroplasty is a commonly performed procedure for symptomatic arthritis, which has not responded to conservative medical treatment. Each patient's perspective of the surgical process and early recovery period impacts on their quality of life. Design: Open, semistructured qualitative interviews were used to allow for a deeper understanding of the patient perspective when undergoing a hip or knee arthroplasty. Methods: Following ethical approval, 30 patients were interviewed between August and November 2016 during the perioperative period while undergoing an elective hip or knee arthroplasty (n = 30). The interviews were performed between the day of surgery and a nine‐week postoperative clinic appointment. Data were analysed using an in‐depth narrative thematic analysis method. NVivo qualitative data analysis software was used. Results: Seven main themes evolved from the interviews: “improving function and mobility”, “pain”, “experiences of health care”, “support from others”, “involvement and understanding of care decisions”, “behaviour and coping” and “fatigue and sleeping”. Conclusions: The early postoperative recovery period is of vital importance to all surgical patients. This is no different for the orthopaedic patient. However, identifying key self‐reported areas of importance from patients can guide clinical focus for healthcare professionals. Relevance to clinical practice: To have specific patient‐reported information regarding key areas of importance during the perioperative phase is invaluable when caring for the orthopaedic surgical patient. It gives insight and understanding in to this increasing population group. This study has also served as a starting point in the development of a questionnaire which could be used to assess interventions in the lower limb arthroplasty population. These results will influence both items and content of the questionnaire.

Background Metal-on-metal hip replacement (MoMHR) revision surgery for adverse reactions to metal debris (ARMD) has been associated with an increased risk of early complications and reoperation and inferior patient-reported outcome scores compared with non-ARMD revisions. As a result, early revision specifically for ARMD with adoption of a lower surgical threshold has been widely recommended with the goal of improving the subsequent prognosis after ARMD revisions. However, no large cohorts have compared the risk of complications and reoperation after MoMHR revision surgery for ARMD (an unanticipated revision indication) with those after non-ARMD revisions (which represent conventional modes of arthroplasty revision). Questions/purposes (1) Does the risk of intraoperative complications differ between MoMHRs revised for ARMD compared with non-ARMD indications? (2) Do mortality rates differ after MoMHRs revised for ARMD compared with non-ARMD indications? (3) Do rerevision rates differ after MoMHRs revised for ARMD compared with non-ARMD indications? (4) How do implant survival rates differ after MoMHR revision when performed for specific non-ARMD indications compared with ARMD? Methods This retrospective observational study involved all patients undergoing MoMHR from the National Joint Registry (NJR) for England and Wales subsequently revised for any indication between 2008 and 2014. The NJR achieves high levels of patient consent (93%) and linked procedures (ability to link serial procedures performed on the same patient and hip; 95%). Furthermore, recent validation studies have demonstrated that when revision procedures have been captured within the NJR, the data completion and accuracy were excellent. Revisions for ARMD and non-ARMD indications were matched one to one for multiple potential confounding factors using propensity scores. The propensity score summarizes the many patient and surgical factors that were used in the matching process (including sex, age, type of primary arthroplasty, time to revision surgery, and details about the revision procedure performed such as the approach, specific components revised, femoral head size, bearing surface, and use of bone graft) using one single score for each revised hip. The patient and surgical factors within the ARMD and non-ARMD groups subsequently became much more balanced once the groups had been matched based on the propensity scores. The matched cohort included 2576 MoMHR revisions with each study group including 1288 revisions (mean followup of 3 years for both groups; range, 1-7 years). Intraoperative complications, mortality, and rerevision surgery were compared between matched groups using univariable regression analyses. Implant survival rates in the non-ARMD group were calculated for each specific revision indication with each individual non-ARMD indication subsequently compared with the implant survival rate in the ARMD group using Cox regression analyses. Results There was no difference between the ARMD and non-ARMD MoMHR revisions in terms of intraoperative complications (odds ratio, 0.97; 95% confidence interval [CI], 0.59-1.59; p = 0.900). Mortality rates were lower after ARMD revision compared with non-ARMD revision (hazard ratio [HR], 0.43; CI, 0.21-0.87; p = 0.019); however, there was no difference when revisions performed for infection were excluded from the non-ARMD indication group (HR, 0.69; CI, 0.35-1.37; p = 0.287). Rerevision rates were lower after ARMD revision compared with non-ARMD revision (HR, 0.52; CI, 0.36-0.75; p < 0.001); this difference persisted even after removing revisions performed for infection (HR, 0.59; CI, 0.40-0.89; p = 0.011). Revisions for infection (5-year survivorship = 81%; CI, 55%-93%; p = 0.003) and dislocation/subluxation (5-year survivorship = 82%; CI, 69%-90%; p < 0.001) had the lowest implant survival rates when compared with revisions for ARMD (5-year survivorship = 94%; CI, 92%-96%). Conclusions Contrary to previous observations, MoMHRs revised for ARMD have approximately half the risk of rerevision compared with non-ARMD revisions. We suspect worldwide regulatory authorities have positively influenced rerevision rates after ARMD revision by recommending that surgeons exercise a lower revision threshold and that such revisions are now being performed at an earlier stage. The high risk of rerevision after MoMHR revision for infection and dislocation is concerning. Infected MoMHR revisions were responsible for the increased mortality risk observed after non-ARMD revision, which parallels findings in non-MoMHR revisions for infection. Level of Evidence Level III, therapeutic study.

Introduction: Enhanced recovery programmes (ERPs) reduce patient morbidity and mortality, and provide significant cost savings by reducing length of stay. Currently, no uniform ERP guidelines exist for lower limb arthroplasty in the UK. The aim of this study was to identify variations in ERPs and determine adherence to local policy. Methods: Hospitals offering elective total knee arthroplasty (TKA) and total hip arthroplasty (THA) (23 and 22 centres respectively) contributed details of their ERPs, and performed an audit (15 patients per centre) to assess compliance. Results: Contrasting content and detail of ERPs was noted across centres. Adherence to ERPs varied significantly (40–100% for TKA, 17–94% for THA). Analysis identified perioperative use of dexamethasone, tranexamic acid and early mobilisation for TKA, and procedures performed in teaching hospitals for THA as being associated with a reduced length of stay. Conclusions: This study highlights variation in practice and poor compliance with local ERPs. Given the proven benefits of ERPs, evidence-based guidelines in the context of local skillsets should be established to optimise the patient care pathway.

Aims To determine the outcomes following revision surgery of metal-on-metal hip arthroplasties (MoMHA) performed for adverse reactions to metal debris (ARMD), and to identify factors predictive of re-revision. Patients and Methods We performed a retrospective observational study using National Joint Registry (NJR) data on 2535 MoMHAs undergoing revision surgery for ARMD between 2008 and 2014. The outcomes studied following revision were intra-operative complications, mortality and re-revision surgery. Predictors of re-revision were identified using competing-risk regression modelling. Results Intra-operative complications occurred in 40 revisions (1.6%). The cumulative five-year patient survival rate was 95.9% (95% confidence intervals (CI) 92.3 to 97.8). Re-revision surgery was performed in 192 hips (7.6%). The cumulative five-year implant survival rate was 89.5% (95% CI 87.3 to 91.3). Predictors of re-revision were high body mass index at revision (subhazard ratio (SHR) 1.06 per kg/m2 increase, 95% CI 1.02 to 1.09), modular component only revisions (head and liner with or without taper adapter; SHR 2.01, 95% CI 1.19 to 3.38), ceramic-on-ceramic revision bearings (SHR 1.86, 95% CI 1.23 to 2.80), and acetabular bone grafting (SHR 2.10, 95% CI 1.43 to 3.07). These four factors remained predictive of re-revision when the missing data were imputed. Conclusion The short-term risk of re-revision following MoMHA revision surgery performed for ARMD was comparable with that reported in the NJR following all-cause non-MoMHA revision surgery. However, the factors predictive of re-revision included those which could be modified by the surgeon, suggesting that rates of failure following ARMD revision may be reduced further.

Few studies have assessed outcomes following non-metal-on-metal hip arthroplasty (non-MoMHA) revision surgery performed for adverse reactions to metal debris (ARMD). We assessed outcomes following non-MoMHA revision surgery performed for ARMD, and identified predictors of re-revision.We performed a retrospective observational study using data from the National Joint Registry for England and Wales. All non-MoMHAs undergoing revision surgery for ARMD between 2008 and 2014 were included (185 hips in 185 patients). Outcome measures following ARMD revision were intra-operative complications, mortality and re-revision surgery. Predictors of re-revision were identified using Cox regression.Intra-operative complications occurred in 6.0% (n = 11) of the 185 cases. The cumulative four-year patient survival rate was 98.2% (95% CI 92.9 to 99.5). Re-revision surgery was performed in 13.5% (n = 25) of hips at a mean time of 1.2 years (0.1 to 3.1 years) following ARMD revision. Infection (32%; n = 8), dislocation/subluxation (24%; n = 6), and aseptic loosening (24%; n = 6) were the most common re-revision indications. The cumulative four-year implant survival rate was 83.8% (95% CI 76.7 to 88.9). Multivariable analysis identified three predictors of re-revision: multiple revision indications (hazard ratio (HR) = 2.78; 95% CI 1.03 to 7.49; p = 0.043); selective component revisions (HR = 5.76; 95% CI 1.28 to 25.9; p = 0.022); and ceramic-on-polyethylene revision bearings (HR = 3.08; 95% CI 1.01 to 9.36; p = 0.047).Non-MoMHAs revised for ARMD have a high short-term risk of re-revision, with important predictors of future re-revision including selective component revision, multiple revision indications, and ceramic-on-polyethylene revision bearings. Our findings may help counsel patients about the risks of ARMD revision, and guide reconstructive decisions. Future studies attempting to validate the predictors identified should also assess the effects of implant design (metallurgy and modularity), given that this was an important study limitation potentially influencing the reported prognostic factors.Cite this article: G. S. Matharu, A. Judge, D. W. Murray, H. G. Pandit. Outcomes following revision surgery performed for adverse reactions to metal debris in non-metal-on-metal hip arthroplasty patients: Analysis of 185 revisions from the National Joint Registry for England and Wales. Bone Joint Res 2017;6:405-413. DOI: 10.1302/2046-3758.67.BJR-2017-0017.R2.

Aims It is not clear whether anterior knee pain and osteoarthritis (OA) of the patellofemoral joint (PFJ) are contraindications to medial unicompartmental knee arthroplasty (UKA). Our aim was to investigate the long-term outcome of a consecutive series of patients, some of whom had anterior knee pain and PFJ OA managed with UKA. Patients and Methods We assessed the ten-year functional outcomes and 15-year implant survival of 805 knees (677 patients) following medial mobile-bearing UKA. The intra-operative status of the PFJ was documented and, with the exception of bone loss with grooving to the lateral side, neither the clinical or radiological state of the PFJ nor the presence of anterior knee pain were considered a contraindication. The impact of radiographic findings and anterior knee pain was studied in a subgroup of 100 knees (91 patients). Results There was no relationship between functional outcomes, at a mean of ten years, or 15-year implant survival, and pre-operative anterior knee pain, or the presence or degree of cartilage loss documented intra-operatively at the medial patella or trochlea, or radiographic evidence of OA in the medial side of the PFJ. In 6% of cases there was full thickness cartilage loss on the lateral side of the patella. In these cases, the overall ten-year function and 15-year survival was similar to those without cartilage loss; however they had slightly more difficulty with descending stairs. Radiographic signs of OA seen in the lateral part of the PFJ were not associated with a definite compromise in functional outcome or implant survival. Conclusion Severe damage to the lateral side of the PFJ with bone loss and grooving remains a contraindication to mobile-bearing UKA. Less severe damage to the lateral side of the PFJ and damage to the medial side, however severe, does not compromise the overall function or survival, so should not be considered to be a contraindication. However, if a patient does have full thickness cartilage loss on the lateral side of the PFJ they may have a slight compromise in their ability to descend stairs. Pre-operative anterior knee pain also does not compromise the functional outcome or survival and should not be considered to be a contraindication.

This paper has two goals. The first is to develop a variety of robust methods for the computation of the Fundamental Matrix, the calibration-free representation of camera motion. The methods are drawn from the principal categories of robust estimators, viz. case deletion diagnostics, M-estimators and random sampling, and the paper develops the theory required to apply them to non-linear orthogonal regression problems. Although a considerable amount of interest has focussed on the application of robust estimation in computer vision, the relative merits of the many individual methods are unknown, leaving the potential practitioner to guess at their value. The second goal is therefore to compare and judge the methods. Comparative tests are carried out using correspondences generated both synthetically in a statistically controlled fashion and from feature matching in real imagery. In contrast with previously reported methods the goodness of fit to the synthetic observations is judged not in terms of the fit to the observations per se but in terms of fit to the ground truth. A variety of error measures are examined. The experiments allow a statistically satisfying and quasi-optimal method to be synthesized, which is shown to be stable with up to 50 percent outlier contamination, and may still be used if there are more than 50 percent outliers. Performance bounds are established for the method, and a variety of robust methods to estimate the standard deviation of the error and covariance matrix of the parameters are examined. The results of the comparison have broad applicability to vision algorithms where the input data are corrupted not only by noise but also by gross outliers.

Hydroxyapatite (HA) coatings have been used to improve implant fixation by promoting bone formation around the prosthesis. A macrophage response to HA particulates has been noted around loosened HA-coated prostheses. As biomaterial wear particle-associated macrophages are known to be capable of differentiating into osteoclasts that are capable of bone resorption, we examined whether particulate HA could similarly induce macrophage-osteoclast differentiation. HA-associated macrophages were isolated from granulomas, formed by subcutaneous implantation of HA, and co-cultured with UMR 106 osteoblast-like cells in the presence of 1,25-dihydroxyvitamin D(3) for up to 14 days on glass coverslips and bone slices. HA-associated macrophage-osteoclast differentiation was evidenced by the formation of numerous multinucleated tartrate resistant acid phosphatase (TRAP)-positive cells which formed lacunar resorption pits on bone slices. Polymethylmethacrylate (PMMA) particle-associated macrophages, isolated from subcutaneous PMMA-containing granulomas, caused significantly more osteoclast formation and bone resorption than HA-associated macrophages. These results indicate that macrophages responding to HA particles are capable of osteoclast differentiation. They also suggest that particles derived from uncemented (HA-coated) implants are likely to induce less osteoclast formation and osteolysis than cemented implants.

We conducted this pilot cadaver study to investigate whether the use of a navigation system during minimally invasive unicompartmental knee arthroplasty leads to more consistent results than the conventional hand-guided technique. We describe the accuracy of implant positioning in using standard instrumentation and computer navigation. Radiographic assessment showed that accurate component placement was achieved using both methods. These results were not statistically significant. The computer navigated femoral component placement without intramedullary (IM) rod was as accurate as the conventional method with IM rod. The study showed that computer navigation can produce accurate results even without an intramedullary rod. Image guidance can maintain the accuracy of the standard instrumentation and enhance 3D vision and the intraoperative orientation of the surgeon.

1 Introduction: This demo showcases breakthrough results in the general field real-time simultaneous localisation and mapping (SLAM) using vision and in particular its vital role in enabling a wearable robot to assist its user. It accompanies the full paper by the same authors at ISMAR2003 [1]. In our approach, a wearable active vision system ("wearable robot") is mounted at the shoulder. As the wearer moves around his environment, typically browsing a workspace in which a task must be completed, the robot acquires images continuously and generates a map of natural visual features on-the-fly while estimating its ego-motion. Naturally such real-time camera localisation permits the annotation of the scene with rigidly-registered graphics, but further it permits automatic control of the robot's active camera: for instance, fixation on a particular object can be maintained during extended periods of arbitrary user motion, then shifted at will to another object which has potentially been out of the field of view. This kind of functionality is the key to the understanding or "management" of a workspace which the robot needs to have in order to assist its wearer usefully in tasks. We believe that the techniques and technology developed are of prime importance towards the goal of a fully autonomous wearable assistant and of particular immediate value in scenarios of remote collaboration, where a remote expert is able to annotate, through the robot, the environment the wearer is working in.

A consecutive series of 40 periprosthetic femoral fractures, treated with revision hip surgery using the Oxford trimodular femoral stem, were retrospectively studied, with an average follow-up of 7.9 years. Fractures were classified according to the Vancouver classification. There were 5 type B1 fractures, 28 type B2, and 7 type C. Radiographic union was achieved in 38 (95%) hips. The mean time to fracture union was 3.5 months. The prosthesis survival at 5 years was 95% (confidence interval, 88%-100%). Clinical results were good with a mean Oxford hip score of 30 (hip score maximum, 48). Complications included 1 nonunion, 1 infection, 1 dislocation, and 2 aseptic loosening. The Oxford trimodular femoral component is a safe and reliable prosthesis for the treatment of periprosthetic femoral fractures with satisfactory medium-term results.

The Charnley Elite and the Exeter stems have different design concepts: The former is designed not to subside, whereas the latter is expected to subside. This radiostereometric analysis study compares the early migration of the 2 stems. For both implants, the 1st year migration was about 4 times faster than the 2nd year. The Exeter migration was predominantly distal (1 mm/y in the 1st year). It also showed slight collapse into valgus, and the head migrated slowly posteriorly (0.3 mm/y in the 1st year). In contrast, the Elite had slow distal migration (0.2 mm/y in the 1st year) and rapid posterior head migration (0.8 mm/y in the 1st year). Four Elites and no Exeters had rapid posterior head migration rates (mean 2.8 mm/y in the 1st year and 0.8 mm/y in the 2nd year). The Elite and the Exeter stems have fundamentally different early patterns of migration, which affect their long-term function; 20% of the Elites and none of the Exeters had rapid posterior head migration in the 1st year and the 2nd year and are likely to fail early. Polished, collarless, tapered designs, such as the Exeter, may be more forgiving than conventional stems designed not to subside.

This paper develops a Square Root Unscented Kalman Filter (SRUKF) for performing video-rate visual simultaneous localization and mapping (SLAM) using a single camera. The conventional UKF has been proposed previously for SLAM, improving the handling of nonlinearities compared with the more widely used Extended Kalman Filter (EKF). However, no account was taken of the comparative complexity of the algorithms: In SLAM, the UKF scales as O(N;{3}) in the state length, compared to the EKF's O(N;{2}), making it unsuitable for video-rate applications with other than unrealistically few scene points. Here, it is shown that the SRUKF provides the same results as the UKF to within machine accuracy and that it can be reposed with complexity O(N;{2}) for state estimation in visual SLAM. This paper presents results from video-rate experiments on live imagery. Trials using synthesized data show that the consistency of the SRUKF is routinely better than that of the EKF, but that its overall cost settles at an order of magnitude greater than the EKF for large scenes.

Medial unicompartmental knee replacement (UKR) has many advantages over total replacement (TKR) including better function and reduced morbidity. However, the long-term failure rates of fixed-bearing UKR are high, especially because of polyethylene wear. The fully congruent mobile bearing of the Oxford UKR exhibits minimal polyethylene wear, failure from this cause does not seem to occur before 10 years.The instrumentation allows precise implantation to restore isometric function of the ligaments. During its 20 years development, the limits of usefulness of the implant have been established and found to include about one in four knees requiring replacement for osteoarthritis. In an independent series, using these criteria, the 15 year survival was 94%. Since 1998, the phase 3 implant has been used with modified instruments through a small incision, avoiding damage to the extensor mechanism. Patients now recover about three times faster than after TKR, and regain much better flexion (mean 135°). The current evidence supports that the minimally invasive Oxford UKR should be seriously considered as primary treatment for anteromedial compartment osteoarthritis - provided the appropriate surgical expertise is available.

We conducted this pilot cadaver study to investigate whether the use of a navigation system during minimally invasive unicompartmental knee arthroplasty leads to more consistent results than the conventional hand-guided technique. We describe the accuracy of implant positioning in using standard instrumentation and computer navigation. Radiographic assessment showed that accurate component placement was achieved using both methods. These results were not statistically significant. The computer navigated femoral component placement without intramedullary (IM) rod was as accurate as the conventional method with IM rod. The study showed that computer navigation can produce accurate results even without an intramedullary rod. Image guidance can maintain the accuracy of the standard instrumentation and enhance 3D vision and the intraoperative orientation of the surgeon. © Springer Medizin Verlag 2005.

OBJECTIVES: To examine national practice, and variations in practice, concerning total hip replacement; in particular the choice of prosthesis and the involvement of consultants in NHS operations. DESIGN: Pre-operative survey of patients undergoing total hip replacement. SETTING: Five English regions serving combined population of 16.8 million people. SUBJECTS: 13,343 total hip replacement operations in one year commencing September 1996, either in NHS or private sector. MAIN OUTCOME MEASURES: Prosthesis used for surgery, status of surgeons involved in operation, use of laminar flow operating theatre. RESULTS: Prostheses without well documented 5-year survival were used in 5504 (58%) of 9417 operations for which information was available. The consultant was the operator in 4810 (64%) of 7499 NHS operations. In 1352 trainee-led operations, the consultant was present for only 637 (47%); this figure was 54% for trainees in years 1-4 of their training. Substantial variation between NHS consultant firms occurred both for use of prostheses with well documented survival data, and supervision of trainees by the consultant. CONCLUSIONS: This large study is the first attempt to describe national practice for primary total hip replacement. Substantial variation among consultant firms was observed for all indices of practice reported.

Aims An evidence based radiographic Decision Aid for meniscal-bearing unicompartmental knee replacement (UKR) has been developed and this study investigates its performance at an independent centre. Patients and Methods Pre-operative radiographs, including stress views, from a consecutive cohort of 550 knees undergoing replacement (UKR or TKR) by a single-surgeon were assessed. Suitability for UKR was determined using the Decision Aid with the assessor blinded to treatment received. Results The sensitivity and specificity of the Decision Aid was 92% and 88% respectively. Excluding knees where a clear pre-operative plan was made to perform TKR, i.e. patient request, the sensitivity was 93% and specificity 96%. The false-positive rate was low (2.3%) with all readily identifiable during joint inspection at surgery. In patients meeting Decision Aid criteria and receiving UKR the 5-year survival was 99% (95%CI 97 to 100%). The false-negatives (3.3%), who received UKR, but did not meet criteria, had significantly worse functional outcomes (flexion (p Conclusion The radiographic Decision Aid safely and reliably identifies appropriate patients for meniscal-bearing UKR and achieves good results in this population. The widespread use of the Decision Aid should improve the results of UKR.

Locally destructive soft tissue pseudotumor has been reported in patients following metal-on-metal hip resurfacing arthroplasty (MoMHRA). A delayed hypersensitivity reaction type IV to nickel (Ni), chromium (Cr), or cobalt (Co) has been suggested to play a role in its aetiology. The aim of this study was to investigate the incidence and level of metal-induced systemic hypersensitivity in patients with MoMHRA, both with and without pseudotumor by measuring lymphocyte proliferation responses to metals. A total of 92 patients were investigated: (1) MoMHRA patients with pseudotumors (nine female, one male); (2) MoMHRA patients without pseudotumors (30 female, 30 male); and (3) age-matched control subjects without metal implants (9 female, 13 male). The venous blood samples were collected for serum Ni, Co, and Cr ion level measurements and lymphocyte transformation tests (LTT). A higher incidence and level of enhanced lymphocyte reactivity only to Ni was found in patients with MoMHRA compared to the patients without MoM implants, reflecting exposure and immune reactivity. However, lymphocyte reactivity to Co, Cr, and Ni did not significantly differ in patients with pseudotumors compared to those patients without pseudotumors. This suggests that systemic hypersensitivity type IV reactions, as measured by lymphocyte proliferation response to these metals, may not be the dominant biological reaction involved in the occurrence of the soft tissue pseudotumors.

Symptomatic abnormal periprosthetic soft-tissue reactions ("pseudotumors") have been reported after metal-on-metal hip resurfacing arthroplasty (MoMHRA). The aims of this study were (1) to determine the prevalence of asymptomatic pseudotumors after MoMHRA and (2) to measure metal ion levels in these patients. A total of 201 hips in 158 patients were evaluated at a mean follow-up of 61 months (range, 36-88) using ultrasound/magnetic resonance imaging and serum/hip aspirate cobalt and chromium measurements. Pseudotumors found in 7 patients (4%) were associated with significantly higher cobalt and chromium levels and inferior functional scores. Elevated levels of cobalt and chromium ions suggest that pseudotumors are associated with increased wear generated from metal-on-metal articulations. Clinicians need to be aware of pseudotumors as a differential diagnosis during clinical evaluation of MoMHRA patients, and further imaging such as ultrasound or magnetic resonance imaging is recommended to confirm the diagnosis.

We assessed the variation in proximal femoral canal shape and its association with geometric and demographic parameters in primary hip OA. In a retrospective cohort study, the joint geometry of the proximal femur was evaluated on radiographs and corresponding CT scans of 345 consecutive patients with end-stage hip OA. Active shape modeling (ASM) was performed to assess the variation in endosteal shape of the proximal femur. To identify natural groupings of patients, hierarchical cluster analysis of the shape modes was used. ASM identified 10 independent shape modes accounting for >96% of the variation in proximal femoral canal shape within the dataset. Cluster analysis revealed 10 specific shape clusters. Significant differences in geometric and demographic parameters between the clusters were observed. ASM and subsequent cluster analysis have the potential to identify specific morphological patterns of the proximal femur despite the variability in proximal femoral anatomy. The study identified patterns of proximal femoral canal shape in hip OA that allow a comprehensive classification of variation in shape and its association with joint geometry. Our data may improve future stem designs that will optimize stem fit and simultaneously allow individual restoration of hip biomechanics.

This paper describes a system for visual telepresence that slaves the motion of an electromechanical stereo head/eye platform to that of an operator's head. Features on the operator's head are detected using an external static camera and tracked over time, using three or more features to find pose (orientation and translation) with a novel algorithm which avoids explicit recovery of the features' 3D positions. The recovered pose is then transformed into demands for the pan and elevation axes of the head platform. The process of capturing images, tracking features, recovering pose, and generating demands runs at 50Hz with a latency of 23ms, with the controller and platform typically taking another 20ms to satisfy a demand. Experiments show that the dynamic performance of the entire system, including head platform, is sufficient to copy head movements of up to 400° s-1.

Fragestellung: Für die Orientierung der Implantatkomponenten im endoprothetischen Ersatz des Hüftgelenkes sind sogenannte sichere Zonen beschrieben worden, um adverse Konsequenzen wie Impingement, Abrieb und Luxationen zu minimieren. Ziele der vorliegenden Studie waren (1) die native, dreidimensionale[for full text, please go to the a.m. URL], Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2012)

Objectives: The clinical importance of a leg length discrepancy (LLD) following total hip arthroplasty (THA) remains controversial. This study was undertaken to determine the effects of LLD on clinical outcomes at up to 3 years follow-up. Design and setting: Prospective, multicentre study. Participants: Nine hundred and eighty-seven cases of primary THA, categorised into two main groups: the NoLLD group (LLD of less than 10 mm) and the LLD group (LLD of 10 mm or more). Main outcome measures: The primary outcome measure was the change in Oxford Hip Score (ΔOHS) at up to 3 years follow-up. Secondary outcome measures were length of operating time and hospital stay, and revision and dislocation rates. Potential predisposing factors for LLD, including body mass index, age and type of anaesthesia employed, were examined. Results: At 3 years, the LLD group had a significantly worse ΔOHS [22.0; 95% confidence interval (CI) 20.5 to 23.5] compared with the NoLLD group (23.8; 95% CI 23.1 to 24.5) (P = 0.034). There were no significant differences in revision (P = 0.389) or dislocation (P = 0.220) rates between the two groups. Use of an epidural was associated with a decreased incidence of developing an LLD of 10 mm (P = 0.004). Conclusion: A postoperative LLD of 10 mm or more leads to poorer functional outcomes. Further studies are needed to assess the impact of an LLD on clinical outcomes in the longer term. © 2008 Chartered Society of Physiotherapy.