Association of Complication Rates and Severe Obesity in Patients Undergoing Ankle Arthrodesis.

Background: Tibiotalar arthrodesis (TTA) is a common operation for end-stage ankle arthritis. Elevated body mass index (BMI) is believed to contribute to complications following TTA. Previous studies involved national registries or small, underpowered cohorts. This study aimed to determine the effects of elevated BMI on nonunion and complication rates following TTA with a large cohort from a single academic institution.

Methods: A retrospective study identified 514 patients (527 ankles) who underwent primary TTA from 2005-2017. Mean age was 60 years. Patients were stratified by BMI according to the World Health Organization classification. A reference group of 203 patients (208 ankles) included normal weight or mildly overweight patients (BMI 18.5 to <30). Ankle radiographs were evaluated to determine union or nonunion. Other outcomes included revision TTA, reoperations, subsequent adjacent joint arthrodesis, infection, and readmission. Data were analyzed using Pearson χ² and odds ratios for categorical variables. Analysis of variance and Kaplan-Meier estimation assessed continuous variables and time-to-event outcomes, respectively. Mean follow-up was 34.3 months.

Results: Obesity class III patients had elevated risk of complications compared with normal weight patients including nonunion (odds ratio [OR] 3.96, P = .002), revision (OR 3.69, P = .03), superficial infection (OR 9.36, P = .002), and readmission (OR 10.90, P = .01). Superficial infection rates were elevated in class I (OR 6.36, P = .007) and readmissions in class II (OR 9.98, P = .01). No differences were found in reoperation (P = .448), symptomatic implant removal (P = .805), adjacent joint arthrodesis (P = .353), or deep infection (P = .507) rates.

Discussion: In this retrospective review after TTA, increased rates of nonunion, revision, superficial infection, and readmission were found in obesity class III patients, compared with the reference group of normal weight or mildly overweight patients. Superficial infection rates were likewise relatively elevated in class I and readmission rates in class II patients.