The Oxford Unicompartmental Knee Replacement's (OUKR's) fully-congruent design minimises polyethylene wear. Consequently, wear is a rare failure mechanism. Phase-3 OUKR linear wear at 5 years was higher than previous OUKR phases, but very low compared to fixed-bearing UKRs. This study aimed to measure OUKR bearing wear at 10 years and investigate factors that may affect wear. Bearing thickness for 39 OUKRs from a randomised study was calculated using radiostereometric analysis at regular intervals up to 10 years. Data for 39 and 29 OUKRs was available at 5 and 10 years, respectively. As creep occurs early, wear rate was calculated using linear regression between 6 months and 10 years. Relationships between wear and patient factors, fixation method, Oxford Knee Score (OKS), bearing position, and component position were analysed.Abstract
Introduction
Methodology
Unicompartmental knee arthroplasty (UKA) offers significant advantages over total knee arthroplasty (TKA) but is reported to have higher revision rates in joint registries. In both the New Zealand and the UK national registry the revision rate of cementless UKR is less than cementless. It is not clear whether this is because the cementless is better or because more experienced surgeons, who tend to get better results are using cementless. We aim to use registry data to compare cemented and cementless UKA outcomes, matching for surgical experience and other factors. We performed a retrospective observational study using National Joint Registry (NJR) data on 10,836 propensity matched Oxford UKAs (5418 cemented and 5418 cementless) between 2004 and 2015. Logistic regression was utilized to calculate propensity scores to match the cemented and cementless groups for multiple confounders using a one to one ratio. Standardised mean differences were used before and after matching to assess for any covariate imbalances. The outcomes studied were implant survival, reasons for revision and patient survival. The endpoint for implant survival was revision surgery (any component removal or exchange). Cumulative patient and implant survival rates were determined using the Kaplan-Meier method. Patients not undergoing revision or death were censored on the study end date. The study endpoints implant and patient survival were compared between cemented and cementless groups using Cox regression models with a robust variance estimator.Introduction
Methods
