Midterm Survivorship of 106 Infinity Total Ankle Replacements: A Case Series From 2 Non-designer UK Centers

Background: The Infinity Total Ankle System is the total ankle replacement (TAR) with market leading share in the United Kingdom and has been implanted in patients since 2014. We report the longest prospective series of Infinity TAR, with mean 8-year survivorship data from 2 nondesigner centers in the United Kingdom. This is a dual-center, prospective, observational study. The primary aims were to assess survivorship and complications of the Infinity TAR. The secondary aims were to assess functional and radiologic outcomes. Methods: A total of 102 patients, comprising 106 primary TARs, were recruited into the study. Revision TAR and conversion from ankle arthrodesis were excluded from the study. Survivorship, complication, and patient-reported outcome measure score data were collected prospectively, during preoperative and annual, postoperative appointments. Plain weightbearing radiographs were assessed by 2 nonmasked authors for Canadian Orthopaedic Foot and Ankle Society (COFAS) grade, coronal and sagittal deformity, and formation of periimplant lucencies. Results: Mean follow-up time was 98 months (range 83-113). Four patients were lost to follow-up, and 12 patients died. Twelve patients underwent secondary surgeries: 8 revision TAR and 4 nonrevision reoperations. The current survivorship of the remaining 90 patients is 91.1% (95% CI, 83.0%-95.4%). Fifteen patients (14%) had complications of surgery. The most common reason for revision surgery was unexplained pain (5 of 8 patients). Manchester-Oxford Foot Questionnaire scores improved from 60 to 22 ( P < .01). EQ-5D-5L scores improved from 0.420 to 0.696 ( P < .01). The revision rate for this series is 9% at 8 years with a proven deep infection rate of 1%. Lucencies (35% of patients) were mostly asymptomatic. Conclusion: This prospective series of 106 modern fixed-bearing TAR shows an 8-year survivorship of 91%. The fixed-bearing Infinity TAR appears to be a safe, effective intervention in the treatment of end-stage ankle osteoarthritis and gives significant improvement in disease-specific and general health status outcomes.