Obesity and Ankle Fractures: Are Outcomes and Complications Really Worse?

Abstract

Category: Ankle; Trauma Introduction/Purpose: Existing literature has established that obese patients have nearly double the risk of sustaining an ankle fracture when compared to a non-obese population. However, few studies have investigated obesity’s effect on fracture complications and patient reported outcomes (PROs) when patients are stratified by fracture type. Furthermore, as the average body mass index (BMI) of our population steadily rises, it becomes prudent to investigate variations in complications rates and patient reported outcomes in various stages of obesity. The aim of this study is to identify trends in complication rates and patient reported outcome scores among patients of different BMI before and after dividing by fracture complexity. Methods: We retrospectively assessed clinical and surgical data from 595 patients who underwent ankle fracture surgery at a single institution between 2017 and 2021 for surgical related complications. All patients had a minimum of 18 months follow up (mean-42.2 [18.2-71.4] months). PROMIS Physical Health and Visual Analog Scale pain scores surveys were available only for patients receiving surgery after November 2019. We aggregated survey data for timepoints between three months and two years post-operatively to assess only patients with meaningful clinical data in regard to their recovery. Patients were divided based on BMI and fracture type. BMI subgroups were classified as: Non-obese (18.5-24.9 kg/m 2 , n=88), Overweight/Obese I (25-34.9 kg/m 2 , n=314), Obese II/III (≥35 kg/m 2 , n=192). Fracture subgroups were divided into two groups: Simple (Unimalleolar types) and complex (Bimalleolar and Trimalleolar variants). Data analysis was performed using Chi-Square and T-Tests with statistical significance set at an alpha (α) of ≤ 0.05. Results: We observed a whole cohort complication rate of (15.3%, n=91/594). Complication rates when stratified by BMI were: Non-obese (12.3%, n=9), Overweight/Obese class I (19.4%, n=61), Obese class II/III (10.3%, n=20). Complication rates for Overweight/Obese I patients were significantly higher when compared to Non-obese patients (p=0.044, OR=2.11). However, there was no significant difference when comparing Non-obese to Class II/III (p=0.972). We observed no significant differences in complications when performing a sub analysis on specific fracture types, regardless of BMI group. Pain scores were significantly higher in both Overweight/Obese I and Obese II/III groups when compared to Non-Obese patients (p= < 0.001, p=0.015). Physical health scores were significantly lower only in the Obese II/III group when compared to Non-Obese patients (p=0.011). Conclusion: Our results indicate that patients who are Overweight/Obese I have a significantly higher risk of complication when compared to patients of normal BMI. Surprisingly, our cohort demonstrated nearly equivalent risk between Obese II/III and Non- obese patient groups. Patient reported outcome data shows different trends with worse pain scores and lower physical health outcomes in the Obese II/III group. These findings add to the growing debate surrounding obesity’s effect on ankle fracture complication rates as well as patient reported outcomes and suggest that increased BMI cannot be viewed purely as a one-to-one relationship with negative outcomes.