How long do ankle arthroplasties last?

Abstract

Despite the increasing numbers of ankle arthroplasties, there are limited studies on their survival and comparisons between different implants. The primary aim of this study was to determine the failure rates of primary ankle arthroplasties commonly used in the UK. A data linkage study combined National Joint Registry (NJR) data and NHS Digital data. The primary outcome of failure was defined as the removal or exchange of any components of the implanted device. Life tables and Kaplan-Meier survival charts were used to illustrate survivorship. Cox proportional hazards regression models were fitted to compare failure rates between 1 April 2010 and 31 December 2018. Overall, 5,562 primary ankle arthroplasties were recorded in the NJR. Linked data show a one-year survivorship of 98.8% (95% confidence interval (CI) 98.4% to 99.0%), five-year survival in 2,725 patients of 90.2% (95% CI 89.2% to 91.1%), and ten-year survival in 199 patients of 86.2% (95% CI 84.6% to 87.6%). The five-year survival for fixed-bearing implants was 94.3% (95% CI 91.3% to 96.3%) compared to 89.4% (95% CI 88.3% to 90.4%) for mobile-bearing implants. A Cox regression model for all implants with over 100 implantations using the implant with the best survivorship (Infinity) as the reference, only the STAR (hazard ratio (HR) 1.60 (95% CI 0.87 to 2.96)) and INBONE (HR 0.38 (95% CI 0.05 to 2.84)) did not demonstrate worse survival at three and five years. Ankle arthroplasties in the UK have a five-year survival rate of 90.2%, which is lower than recorded on the NJR, because we have shown that approximately one-third of ankle arthroplasty failures are not reported to the NJR. There are statistically significant differences in survival between different implants. Fixed-bearing implants appear to demonstrate higher survivorship than mobile-bearing implants.