Objective To analyse the reasons of failure of metal- backed patellar component and observe the clinical outcome of the revision procedure. Methods Thirty isolated patellar revision for failed metal- backed patellar components following total knee arthroplasty in 22 patients were reviewed. All had similar total condylar knee prosthesis inserted with retention of the posterior cruciate ligament and resurfacing of the patella. There were 4 males and 18 females. Knee Society Score rating system was used for the final evaluation. Results In average the failure occurred in 62.3 months (ranged from 26 to 96 months). The majority of patients presented with metallic crepitus(80％ ) and pain of the knee(70％ ). At surgery, full thickness polyethylene wear exposing the metal- backing was present in 76.7％ with surface damage of the femoral components in 36.7％ . There was tilting of patella in 9 knees and dislocation of patella in 2 knees. All 30 knees underwent successful isolated patellar component revision with cemented polyethylene patellar buttons. Final follow- up averaged 42.5 months, all manifestations were reported significant improvement in 22 patients. The average knee score improved from 73 points(ranged from 27 to 88) pre- revision to 87 points(ranged from 60 to 100) at the final follow- up. Conclusion Resurfacing of the patella in total knee arthroplasty with metal- backed patellar components carries a significant risk of early failure. Malalignment and maltracking of patella may be a predisposing factor to early failure in metal- backed patellar components.

Introduction: This study aims to investigate whether patients undergoing two-stage revision total hip arthroplasty (THA) for prosthetic joint infection (PJI) and one-stage revision THA for aseptic reasons have similar clinical outcomes and patient satisfaction during their post-operative follow-up. We hypothesise that the two-stage revision THA for PJI is associated with poorer outcomes as compared to aseptic revision THA. Materials and Methods: We reviewed prospectively collected data in our tertiary hospital arthroplasty registry and identified patients who underwent revision THA between 2001 and 2014, with a minimum of two years follow-up. The study group (two-stage revision THA for PJI) consists of 23 patients and the control group (one-stage revision THA for aseptic reasons) consists of 231 patients. Patient demographics, Western Ontario and McMaster Universities Arthritis Index (WOMAC), Oxford Hip Score (OHS), Short Form-36 (SF-36) scores and patient reported satisfaction were evaluated. Student’s t-test was used to compare continuous variables between the two groups. Statistical significance was defined as p <0.05. Results: The pre-operative demographics and clinical scores were relatively similar between the two groups of patients. At two years, patients who underwent revision THA for PJI reported a better WOMAC Pain Score and OHS as compared to aseptic revision THA. A similar proportion of patients were satisfied with their results of surgery in both groups (p=0.093). Conclusions: Although patients who underwent revision THA for PJI had poorer pre-operative functional scores (WOMAC function and SF-36 PF), at two years follow-up, these two groups of patients have comparable post-operative outcomes. Interestingly, patients who had revision THA for PJI reported a better clinical outcome in terms of OHS and WOMAC Pain score as compared to the aseptic group. We conclude that the revision THA for PJI is not inferior to aseptic revision THA in terms of patient satisfaction and clinical outcomes.