2 to 5 year outcomes of 503 fixed bearing ankle arthroplasties

D. Townshend, A. Bing, T. Clough, I. Sharpe, C. Blundell, J. Davenport, H. Davies, J. Davis, S. Dhar, A. Goldberg, M. Karski, S. Hepple, R. Kakwani, J. McKinley, A. Murty, M. Ragland, H. Shalaby, R. Smith, H. Taylor

Introduction: This is a multi-centre, prospective, observational study of 503 INFINITY fixed bearing total ankle arthroplasties. We report the minimum two-year results of this prosthesis which was introduced to the UK Market in 2014 and is now the most used ankle arthroplasty in the National Joint Registry of England and Wales.

Methods: Patients were recruited from 11 centres in the United Kingdom between June 2016 and November 2019. Demographic, radiographic, and functional outcome data (Ankle Osteoarthritis Scale, Manchester Oxford Foot Ankle Questionnaire and Euroquol 5D-5L) were collected preoperatively, at 6 months, 1 year and 2 years and 5 years. The average age was 67.8 (range 23.9 to 88.5) and average BMI 29.3 (18.9 to 48.0). The COFAS grading system was used to stratify deformity. There were 261 (51.9%) COFAS Type 1, 122 (24.2%) COFAS Type 2, 31(6.2%) COFAS 3 and 89 (17.7%) COFAS type 4. 38 patients (7.6%) presented with inflammatory arthritis. 99 (19.7%) implantations utilised patient specific instrumentation. Complications and reoperations were recorded as adverse events. Radiographs were assessed for lucencies, cysts and/or subsidence.

Results: The mean follow up was 34.2 months (range 24-64).15 patients have died, 8 withdrawn and 3 lost to follow up. 8 implants (1.6%) have been revised. According to the Glazebrook classification there were low grade complications in 6.6%, medium grade in 1.4% and high grade in 1.6%. There have been an additional 13 non revision re-operations (2.6%) at the latest follow up. There was a significant (p<0.01) improvement across all functional outcome scores at a minimum of 2yr follow up.

Discussion and conclusion: This large cohort has shown a low early revision rate and high functional outcomes with a low-profile fixed bearing prosthesis.