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Background The primary aim was to assess survival of opening wedge high tibial osteotomy (HTO) for medial compartment osteoarthritis. The secondary aim was to identify independent predictors of early conversion to total knee arthroplasty (TKA). Methods During the 18-year period (1994–2011) 111 opening wedge HTO were performed at the study centre. Mean age was 45 years (range 18–68) and the majority male (84%). Mean follow-up was 12 (range six to 21) years. Failure was defined as conversion to TKA. Kaplan–Meier, Cox regression and receiver operating curve (ROC) analyses were performed. Results Forty (36.0%) HTO failed at a mean of 6.3 years (range one to 15). By Kaplan–Meier analysis, the five-year survival rate was 84% (95% confidence interval (CI) 82.6–85.4), 10-year rate 65% (95% CI 63.5–66.5) and 15-year rate 55% (95% CI 53.3–56.7). Cox regression analysis identified older age (hazard ratio (HR) 1.07 for each additional year, 95% CI 1.03–1.11, p b 0.001) and female gender (HR 2.37, 95% CI 1.06–5.33, p = 0.04) as independent predictors of failure. ROC analysis identified a threshold age of 47 years above which the risk of failure increased significantly (area under curve 0.72, 95% CI 0.62–0.81, p b 0.001). Cox regression analysis, adjusting for covariates, identified a significantly greater (HR 2.49, 95% CI 1.26–4.91, p = 0.01) risk of failure in patients aged 47 years old or more. Conclusion The risk of early conversion to TKA is significantly increased in females and those older than 47. These risk factors should be considered pre-operatively when planning intervention for isolated medial compartment osteoarthritis.

Background The low contact stress (LCS) mobile-bearing total knee replacement (TKR) was designed to minimise polyethylene wear, aseptic loosening and osteolysis. However, registry data suggests there is a significantly greater revision rate associated. The primary aim of this study was to assess long-term survivorship of the LCS TKR performed at a single high-volume centre. Secondary aims were to assess survival by mechanism of failure and identify predictors of revision. Methods During a 13-year period (1993–2006) 1091 LCS TKRs were performed by two senior surgeons. Thirty-three with incomplete data were excluded. The patients were retrospectively identified from an arthroplasty register. Mean age was 69 (range 30–96) years. Five hundred seventy-seven TKRs were performed in females, 481 in males. Mean follow-up was 14 years (SD 4.3). Results There were 59 revisions during the study period: 14 (23.7%) for infection, 18 (30.5%) for instability, and 27 (45.8%) for polyethylene wear. Three hundred ninety-two patients died. All-cause survival at 10 years was 95% (95%CI 91.7–98.3) and at 15 years was 93% (95%CI 88.6–97.8). Survival at 10 years according to mechanism of failure was: infection 99% (95%CI 94–100%), instability 98% (95%CI 94–100%), and polyethylene wear 98% (95%CI 92–100). Of the 27 with polyethylene wear, only 19 (70.4%) had osteolysis requiring component revision, the other eight (29.6%) had polyethylene exchanges. Cox regression analysis identified younger age as the only predictor of revision (HR 0.96, 95%CI 0.94–0.99, p = 0.003), with a four percent decreased risk of revision for each increase in year of age. Conclusions The LCS TKR demonstrates excellent long-term survivorship with a low rate of revision for osteolysis, however this risk is increased in younger patients.