Introduction/Purpose: Total ankle replacement (TAR) is increasingly used to treat end-stage ankle osteoarthritis, but failure and complication rates remain significant. These are often attributed to implant and patient factors, including obesity, which affects 42.4% of U.S. adults (BMI ≥30 kg/m²). While obesity is well established as a risk factor for higher complication, infection, and revision rates in total knee and hip replacement, there is a limited literature investigating the impact of obesity on TAR outcomes. This study evaluates complication, infection, and revision rates of primary TAR in patients across BMI cohorts. We hypothesized that TAR patients with BMI 35-39.9 kg/m2 and BMI >40.0kg/m2 would have higher short-term complications and long-term infection and revision rates compared to those without obesity.
Methods: This is a retrospective database cohort study using the TriNetX research database. Patients ≥18 years who underwent primary TAR from database inception to 2025 with minimum 2-years of follow-up were included. Patients were stratified by BMI: non-obese (BMI<30) (control), BMI 30.0-34.9, BMI 35.0- 39.9, and BMI≥40. Outcomes of interest included 90-day surgical site infections and major complications, as well as 1- and 5-year implant failure and PJI rates. Major complications included death, stroke, myocardial infarction, pulmonary embolism, acute kidney injury, and sepsis. Implant failure included mechanical loosening, displacement, osteolysis, periprosthetic fractures (PPF), revisions, and any ORIF. Categorical variables were analyzed using chi-squared tests and Fisher’s exact tests. Continuous variables were analyzed with student’s t-test. Kaplan-Meier survival analysis with log-rank tests compared implant survival. A total of 3,533 patients (44.9% female, mean age of BMI cohorts ranged 59.2-64.3 years) were included.
Results: At 90-days postoperatively, patients with BMI≥40 had higher risk of major complications (4.7% vs 2.0%, p=0.005) (Table). A higher risk of PPF was observed in patients with BMI 35.0-39.9 (4.7% vs 2.4%, p=0.025) and BMI≥40 (4.3% vs 2.4%, p=0.030) (Table). No significant differences in implant failures or PJI were observed across all BMI groups at 1- and 5-years postoperatively (p>0.05 for all). Kaplan-Meier analysis showed no significant differences in survival rates between cohorts (5-year survival: BMI<30: 90.0%, BMI 30.0-34.9: 90.3% (p=0.949), BMI 35.0-39.9: 91.6% (p=0.364), and BMI≥40: 86.4% (p=0.106)).
Conclusion: TAR demonstrates good 5-year survivorship across BMI groups. However, at 90-days, patients with BMI ≥35 face increased risk of periprosthetic fractures and those with BMI ≥40 have increased medical complications. These findings suggest that while obesity does not appear to compromise overall 5-year implant survivorship, careful preoperative patient optimization and patient selection is needed to reduce early postoperative risks in patients with elevated BMI. In addition, patients with BMI ≥35 are at a higher risk for periprosthetic fracture and may benefit from prophylactic malleolar fixation.
