The Impact of GLP-1 Agonist Therapy in Tibiotalar and Subtalar Fusion: A Propensity-Matched Analysis

Category: Diabetes; Ankle Introduction/Purpose: The rising prevalence of obesity and diabetes mellitus have rendered the usage of GLP-1 agonists increasingly commonplace since their introduction in 2005. Foot and ankle surgeons consistently provide orthopedic care to diabetic patients through tibiotalar and subtalar fusion. There is, however, a dearth of evidence to suggest whether outcomes of ankle fusion differ in patients treated with GLP-1 agonists. This study retrospectively compares rates of infection and failed fusion in patients who underwent tibiotalar or subtalar fusion with and without concurrent GLP-1 agonist therapy. Methods: The TriNetX Diamond Network was queried using CPT and ICD codes for patients with diabetes mellitus undergoing tibiotalar or subtalar fusions from 2005 to 2024. Diagnosis codes occurring within 1 year of the index procedure for: infection following a procedure (T81.4) and pseudoarthrosis after attempted fusion (M96.0) were compared using chi-squared statistical testing. Cohort balancing was performed categorically according to age at procedure, race, sex, and nicotine dependence. Cohort balancing was performed continuously for index BMI, Hemoglobin A1C, estimated Glomerular Filtration Rate (eGFR). Significance was set at p< 0.05 with associated 95% confidence intervals. Results: Overall, two propensity-matched cohorts of 708 patients were included in our analysis. Cohorts were not significantly different across any of the balancing parameters (p>.05). The postoperative infection rate was found to be significantly higher in the GLP-1-treated group (9.0%) than the non-treated group (5.6%) (p=0.02). No statistical significance was observed in the rate of postoperative pseudoarthrosis amongst patients who underwent fusion with (9.0%) and without (12.0%) GLP-1 agonist usage (p=0.08). Conclusion: Although GLP-1 agonists have provided significant benefit in the treatment of obesity and diabetes mellitus, results of this study suggest a previously unreported risk of postoperative infection associated with GLP-1 agonist use following ankle arthrodesis. Further investigation is needed GLP-1 agonists' effects on foot and ankle surgery. It is our hypothesis that previously demonstrated anti-inflammatory properties attenuate immune response and predispose patients to postoperative infection. Past inquiries have also demonstrated reduced osteoclast activity with GLP-1 agonist administration. Therefore, we suspect that decreased osteoclast activity at fusion margins may disrupt resorption of heat-necrosed bone, leaving a nidus for infection.