Outcome of Conversion to Fusion for a Failed Ankle Replacement: A Data Linkage Study using the National Joint Registry and NHS Digital

Abstract

Category: Ankle Arthritis Introduction/Purpose: There are limited studies on the outcomes of conversion to fusion following a failed ankle replacement. The primary aim of this NJR data linkage study is to determine the outcomes of conversion to fusion following a failed ankle replacement. Methods: A data linkage study combined National Joint Registry Data and NHS Digital data. The primary outcome of failure is defined as a further fusion procedure or amputation. Life tables and Kaplan Meier survival charts demonstrated survivorship. Cox proportional hazards regression models with the Breslow method used for ties were fitted to compare failure rates. Results: 131 patients underwent conversion to fusion. The mean time from primary replacement was 33.8 months (range 1-100). The mean age was 63.3 (range 33-85), there were 73 males (55.7%). The mean BMI was 30.7 (SD 5.3) mean ASA was 2.0 and the mean Charlson co-morbidity score was 2.5. The most commonly revised implant was the Mobility in 45.0%, Zenith in 16.8% and Box in 11.5%.105 (80.2%) were as a single stage and 26 (19.8%) as a 2 stage procedure. The 1 year survivorship was 96.0% (95% CI 90.6%-98.3%), 2 year survivorship was 83.8% (95% CI 75.4%-89.5%) and 5 year survivorship was 72.4% (95% CI 62.0%-80.4%) A Cox regression model adjusting for individual factors did not find any risk factor significantly increased the risk of failure. Conclusion: Conversion to fusion following a failed ankle replacement has high rates of further surgery. Further prospective studies are required to determine risk factors for failure to improve outcomes for these patients.