Association Between Obesity and Short- and Midterm Complications Following Total Ankle Replacement

Background: Total ankle replacement (TAR) is increasingly used to treat end-stage ankle osteoarthritis, but the effect of obesity on complications and implant failure remains understudied. This study evaluates short- and midterm outcomes of TAR across body mass index (BMI) categories. Methods: This is a retrospective database cohort using TriNetX Research Database, a federated national database of deidentified electronic medical records from more than 100 health care organizations (HCOs). Patients ≥18 years who underwent primary TAR from 2014 to 2025 with minimum 2 years of follow-up were included. Patients were stratified by BMI: <30 (nonobese), 30.0 to 34.9, 35.0 to 39.9, and ≥40. Our primary outcome was 5-year implant failure rate. Secondary outcomes included 90-day surgical site infections and major complications, as well as 1-year implant failure and 1- and 5-year periprosthetic joint infection (PJI) rates. Propensity-score matching (PSM) was performed comparing BMI <30 and BMI ≥35. Results: A total of 3533 patients (50% female; mean age across cohorts ranged 59-64 years) were analyzed, including 1511 nonobese patients, 1118 with BMI 30.0 to 34.9, 608 with BMI 35.0 to 39.9, and 296 with BMI ≥40. At 90 days postoperatively, patients with BMI ≥40 had higher rates of major medical complications vs nonobese patients (OR 2.45, 95% CI 1.28-4.68; P = .005). Also, by 90 days, periprosthetic fracture risk was also elevated in patients with BMI 35.0 to 39.9 (OR 1.78, 95% CI 1.07-2.97; P = .025) and ≥40 (OR 1.98, 95% CI 1.06-3.71; P = .030). In propensity score matching, only the risk of 90-day medical complications remained elevated in patients with BMI ≥35. With the numbers available, no significant differences were observed in 5-year implant failure, with implant survival of 90.0% in patients with BMI <30, 90.3% in BMI 30.0 to 34.9, 91.6% in BMI 35.0 to 39.9, and 86.4% in BMI ≥40. However, the study is underpowered to exclude clinically meaningful differences. Discussion: While 5-year implant survivorship appeared comparable across cohorts, patients with BMI ≥40 demonstrated a significantly higher risk of early postoperative medical complications. However, the study lacked sufficient power to definitively exclude clinically meaningful differences in long-term failure, particularly given the non-significantly lower survivorship in the morbidly obese. Level of Evidence: Level III, retrospective comparative study.