Mid-Term Outcomes of Total Ankle Arthroplasty in High-Risk Populations

Submission Type: Total Ankle Arthroplasty Research Type: Level 3 - Retrospective cohort study, Case-control study, Meta-analysis of Level 3 studies Introduction/Purpose: Total ankle arthroplasty (TAA) preserves ankle motion and avoids complications associated with ankle arthrodesis. However, initial designs demonstrated poor outcomes and implant survivorship. Modern TAA designs mimic the ankle anatomy, minimize bone cuts and rely on cementless fixation. Current literature suggests that 4th generation implants have favorable clinical outcomes compared to older generations. However, heterogeneity of outcome reporting and lack of long-term outcomes in the reported studies is common. Evaluation of the mid-to-long term outcomes is warranted to guide appropriate patient selection and manage patient expectations. The purpose of this study is to evaluate the mid-term clinical and radiographic outcomes of modern TAA implants with particular focus on high-risk populations including obese patients, diabetics, smokers, and those with severe pre-operative tibiotalar coronal deformity. Methods: This is a retrospective review of patients who underwent primary TAA at a tertiary referral center from January 1, 2018 to September 20, 2022. Inclusion criteria included age ≥18 years and pre-operative diagnosis of primary osteoarthritis or post-traumatic tibiotalar arthritis. Exclusion criteria included fusion takedown TAA, pre-operative diagnosis of inflammatory tibiotalar arthritis, less than 2 years follow up, and patients lost to follow-up. A total of 170 primary TAAs were identified, and 78 were ultimately included. Mean follow-up was 3.9 years (range 2.0-8.3). There were 6(7.7%) smokers, 17(21.8%) diabetics, 2(37%) with BMI 30-34.9, and 26(33%) with BMI≥35. Implants included 65(83%) Inbone II, 9(12%) Vantage, and 4(5%) Infinity. Revision surgery was defined as removal or exchange of the metal components. Radiographic tibiotalar coronal deformity was evaluated at four time periods: pre-operative as well as 3 months, 1 year, and most recent post-operative. Severe pre-operative coronal deformity was defined as ≥10 degrees. Results: TAA survivorship was 96% at mean follow-up. There were 47 complications in 23(30%) ankles. Revision surgery was required in 15(19%) ankles due to deep infection (10, 67%), component subsidence (4, 27%), and talar AVN (1, 7%). Primary revision included revision TAA (10, 67%), tibiotalocalcaneal arthrodesis (2, 13%), ankle arthrodesis (1, 7%), total talus (1, 7%), and BKA (1, 7%). Six ankles required a second revision: 5 (83%) conversion to TTC, 1(7%) revision TAA. Diabetes mellitus, tobacco, BMI ≥ 30 had no increased complication or revision rates. BMI ≥ 35 had significantly higher likelihood of any individual or total complication and infection. Pre-operative coronal deformity ≥10 degrees had no increased revision rates. Post-hoc analysis showed significantly increased revision surgery rate with pre-operative coronal deformity ≥19 degrees. Conclusion: At mid-term follow-up, 4th generation TAA demonstrated excellent implant survivorship (96%). Revision surgery was required in 15(19%) ankles, primarily due to deep infection (10, 65%). Post-hoc analysis showed significantly increased revision surgery rate with pre-operative coronal deformity ≥19 degrees. Morbid obesity (BMI ≥ 35) was associated with higher rates of any individual complication, total complications, and infection, but was not associated with increased rates of revision surgery. Future studies with larger sample size and longer follow-up periods are needed to further delineate the long-term effects of medical comorbidities and severe deformity on implant survivorship and outcomes after total ankle arthroplasty.