Mid- to Long-Term Outcomes of the STAR Total Ankle Replacement

Abstract

Category: Ankle Arthritis; Ankle Introduction/Purpose: The Scandinavian Total Ankle Replacement (STAR) is a widely used ankle prosthesis, but mid- to long-term follow up remains limited. In thirteen different studies involving 939 STAR total ankle prostheses, the average duration of follow- up for recipients was 3.9 years. Thus, we sought to evaluate the STAR at the mid- to long-term interval with regards to survivorship, complications, and patient reported outcomes (PROs) in one of the largest series with the longest-term follow up to date. Methods: All patients managed with a primary STAR prosthesis at our institution from March 2002 through January 2017 were included in the analysis. Demographic characteristics including gender, race, age, diabetes status, body mass index (BMI), smoking status, American Society of Anesthesiologist (ASA) score, and surgery time were summarized. The cumulative incidence of implant failure was at 5 years and the last recorded time to event (8 years) were reported with 95% confidence intervals (CI). Paired t- tests were used to compare pre-operative and 5 year post-operative (±1 year) for PROs including Visual Analog Scale (VAS), Short Musculoskeletal Function Assessment (SMFA), Short-form-36 (SF-36), and American Orthopaedic Foot & Ankle Society (AOFAS) hindfoot subscales. Additionally, intra- and post-operative complications were recorded. All statistical analysis were conducted in SAS 9.4 (Cary, NC). Statistical significance was assessed at α = 0.05. Results: 247 patients with a unilateral STAR procedure were included in this analysis. Demographics are listed in Table 1. The average number of years of follow-up was 5.71 ± 4.07 years. The cumulative incidence of implant failure at 5 years was 7.7% (95% CI 4.3%-12.5%). The last failure event occurred at 8 years post-implant. The cumulative incidence of implant failure at 8 years was 11.1% (95% CI 6.3%-17.3%) (Table 2, Figure 1). The most common post-operative complications were impingement (N = 39, 15.8%), ankle pain (N = 22, 8.9%), and implant failure (N = 16, 6.5%) (Table 3). With regards to PROs, patients significantly improved between baseline and 5-year follow up in all measures (all p< 0.001; Table 4). Conclusion: At mid- to long-term follow up, patients receiving the STAR prosthesis experienced a significant and durable improvement in PROs across multiple functional indices. Complication and failure rates were lower than those reported in previous series evaluating the STAR, with an observed survivorship of 88.9% at 8-year follow up.