Clinical comparison of mobile-bearing versus fixed-bearing total ankle arthroplasty

Aims: The aim of this study was to compare the clinical outcomes and implant survival of mobile-bearing (Zenith) and fixed-bearing (Infinity) total ankle arthroplasties (TAAs) in two consecutive demographically similar groups of patients, from a single, non-designer centre. Methods: Between December 2010 and May 2016, 118 consecutive mobile-bearing TAAs (Zenith), and between September 2017 and November 2019, 118 consecutive fixed-bearing TAAs (Infinity), were implanted in a total cohort of 230 patients. Demographic, clinical, and patient-reported outcome measures (PROMs) were collected. The endpoint of the study was failure of the implant requiring revision of one or more of the components. Kaplan-Meier survival tables were generated. Results: Demographic data were similar in both groups. A total of 32 patients (36 TAAs) died during the follow-up period, but none required revision. Of the surviving 198 patients (200 TAAs; 93 Zenith, 107 Infinity), the mean follow-up was 9.1 years (6.0 to 13.1) in the Zenith and 5.0 years (3.8 to 7.0) in the Infinity group. A total of 11 TAAs (9.3%) in the Zenith group and one (0.8%) in the Infinity group required revision. The mean time to failure was 3.2 years (0.4 to 10.5) in the Zenith group and 4.1 years for the one patient requiring revision in the Infinity group. Implant survival at five years, using revision as an endpoint, was 91.3% (95% CI 96.9 to 85.6) for Zenith and 98.7% (95% CI 99.5 to 97.8) for Infinity. There was an improvement in the mean Manchester-Oxford Foot and Ankle Questionnaire score from 85.0 (SD 12.6) to 32.8 (SD 22.9) in the Zenith group and 76.2 (SD 14.5) to 21.7 (SD 22.7) in the Infinity group, and in the mean visual analogue scale scores for pain from 7.0 (SD 1.4) to 3.2 (SD 1.7) in the Zenith group and 6.9 (SD 1.6) to 2.7 (SD 2.0) in the Infinity group. The most common indication for revision was aseptic loosening in both groups. Conclusion: These findings showed significantly better survival for the fixed-bearing (Infinity) compared with the mobile-bearing (Zenith) TAAs. While the Infinity group had better PROM scores, the difference was not statistically significant.