COFAS Grade is not Associated with Outcomes following Infinity Total Ankle Arthroplasty: A Multicenter Study with Minimum Five-Year Follow-Up

Abstract

Background: Total ankle arthroplasty (TAA) is increasingly used for end-stage ankle arthritis, with modern fixed-bearing designs demonstrating improved survivorship. The Canadian Orthopaedic Foot and Ankle Society (COFAS) classification stratifies patients by intra-articular and extra-articular deformity and adjacent joint arthritis. However, limited evidence exists on the impact of COFAS grade on mid-term TAA outcomes. This study reports the minimum 5-year outcomes of the Infinity fixed-bearing TAA and examines whether COFAS grade influences survivorship (defined as freedom from revision), complications, reoperations, revisions, radiographic findings, or patient-reported outcomes (PROMs). Methods: A prospective, multi-center observational study included 502 ankles in 496 patients who underwent primary Infinity TAA across 11 UK centers. Patients were stratified by preoperative COFAS grade. Outcomes included implant survivorship, complications, reoperations, revisions, radiographic assessment of radiolucencies, and PROMs (the Manchester-Oxford Foot Questionnaire; the Ankle Osteoarthritis Scale [AOS]; and the EuroQol 5-dimension, 5-level index) collected preoperatively and at 2 and 5 years postoperatively. Patient-specific instrumentation (PSI) use was also recorded. Results: Five-year implant survivorship was 98.2%, and reoperation without revision was 5.8%. There was no significant association between COFAS grade and revision or reoperation rates. Radiographic analysis demonstrated 5.7% linear radiolucencies >2 mm and 10.9% cystic radiolucencies >5 mm, with no correlation to COFAS grade. PROMs improved significantly across all domains from baseline to 5 years, with no differences between COFAS grades. PSI, used in 20.1% of cases, was associated with improved AOS scores at 5 years, though PSI and site effects could not be fully disentangled, and did not influence complication, revision, or radiographic outcomes. Conclusion: In this large multicenter cohort, higher COFAS grades were not associated with inferior outcomes in patients undergoing Infinity fixed-bearing TAA. Survivorship, complications, reoperations, radiographic outcomes, and PROMs were not statistically different across all grades. In this cohort, Infinity TAA was associated with favorable outcomes across all COFAS grades, including those with complex deformity or adjacent joint disease. Level of Evidence: Level II, prospective cohort study.