The Effect of BMI on Outcomes, Complications, and Union Rate following Midfoot and Hindfoot Arthrodesis Procedures

Research Type: Level 3 - Retrospective cohort study, Case-control study, Meta-analysis of Level 3 studies Introduction/Purpose: BMI is a patient factor that has previously been found to influence patient outcomes following various orthopaedic procedures. This phenomenon has been highlighted repetitively in the context of hip and knee arthroplasty; meanwhile, literature in the foot and ankle community remains limited. More specifically, there is a significant deficit in current literature to describe how BMI may impact outcomes following arthrodesis procedures about the foot and ankle. Accordingly, the current study analyzed the interaction between a patient’s BMI and the rate of fusion, complications, and improvement in patient reported outcomes following midfoot and hindfoot arthrodesis. Methods: A retrospective review was performed on patients who underwent forefoot, midfoot, or hindfoot arthrodesis procedures between March 2021 and May 2023 at a single academic institution. All patients were > 18 years of age at the time of surgery; all had > 12 months of follow-up. A total of 197 joints in 136 patients were included in the current study. Demographic information, graft specifications, Patient Reported Outcome Measurement Information System (PROMIS) scores and postoperative complications were recorded for each patient. Outcomes were compared in relation to BMI and with respect to location of procedure (midfoot/hindfoot). Categorical and continuous data were compared using Chi-squared test and analysis of variance (ANOVA), respectively; all p< 0.05 (*) were considered statistically significant. Results: In patients who underwent midfoot arthrodesis, a significant improvement in PROMIS pain (p=0.011*), function (p=0.015*), and mobility scores (p=0.034*) were observed in the BMI < 40 cohort in comparison to the BMI > 40 cohort. There was no significant difference observed in the union rate or other postoperative complications following midfoot arthrodesis between cohorts. In patients that underwent hindfoot arthrodesis, a significant difference in PROMIS function scores (p=0.028*) was observed between cohorts. There was no difference in the union rate observed between BMI cohorts following hindfoot arthrodesis. However, a higher rate of wound infections (p=0.046*), wound dehiscence (p=0.046*), and overall complications (p=0.043*) was observed in patients who underwent hindfoot arthrodesis with a BMI > 40 in comparison to those with a BMI < 40. Conclusion: Patients with a BMI < 40 were found to have a greater improvement in patient reported outcomes following midfoot arthrodesis when compared to patients of a BMI > 40. Following hindfoot arthrodesis, a reduction in wound and overall complications were observed in patients with a BMI < 40 in comparison to patients with a BMI > 40. While there was no difference in the union rate between BMI cohorts in patients who underwent midfoot arthrodesis or hindfoot arthrodesis, data in the current study suggest BMI may serve as a predictor of patient outcomes and/or complications following various arthrodesis procedures.