Mid Term Survivorship of the Infinity Ankle Replacement in the National Joint Registry

Category: Ankle Arthritis; Ankle Introduction/Purpose: The Infinity ankle replacement is a two component fixed bearing implant. It was introduced to the market in in 2014 is now the most commonly implanted ankle replacement globally. The National Joint Registry of England Wales and Northern Ireland is the largest ankle replacement registry in the world which captures outcomes of ankle replacements in a voluntary but mandated fashion. The primary aim of this study was to determine the failure rates of the Infinity ankle replacement in the UK. Methods: Data was collected prospectively by the NJR with all primary ankle replacements captured on proforma forms known as the NJR A1. All failures of ankle replacements are recorded using an NJR A2 form. Results: Overall 3781 implants have been implanted. The mean age was 68.5 and median BMI of 29, 60.5% male. 82.7% of patients were ASA 1 or 2 and the indication was osteoarthritis in 92.5%. Overall 60 implants have been revised. The most common reason was infection in 33 cases, followed by aseptic loosening of the tibia. Aseptic loosening of the talus only occurred in 2 cases. The failure rate of the Infinity was significantly better (P< 0.001) when compared to the expected number of revisions of 96.03. 20 revisions were exchange of polyethylene, with 15 revisions of both components. The 1 year failure rate is 0.5% (95% CI 0.3-0.7%). The 5 year failure rate is 2.2% (1.7%-2.8%), and 7 year survival in 225 patients is 3.5% (2.3-4.8%). Conclusion: The Infinity ankle replacement has lower failure rates than expected when compared to other contemporary ankle replacements. This data highlights the improvement in outcomes of a new fourth generation fixed bearing ankle replacement