Impact of Obesity on Severity of Ankle Fracture

Abstract

Category: Trauma; Ankle Introduction/Purpose: Ankle fractures are one of the most common types of foot and ankle trauma requiring surgery. Prior studies have investigated the association between obesity and ankle fracture on a general level, but not all studies have broken down the data by ankle fracture pattern subtypes. The aim of this study was to investigate the association between obesity and severity of ankle fractures, as classified by single malleolar (isolated fibular, posterior malleolar or medial malleolar), bimalleolar, trimalleolar and pilon subtypes. Methods: We retrospectively investigated the patient charts of 1,326 treated ankle fractures from 2011 to 2021 at a level 1 trauma center as identified by CPT codes. Collected data included age, diagnosis, BMI (obese > 30 kg/ m2), and vitamin D. For this study, we excluded patients who did not have a fracture of a malleoli or a pilon fracture (n=129). Severity of fracture was determined by number of malleoli fractured with the addition of pilon fracture as the most severe. Inferential statistics were performed using ANOVA and chi-squared tests. Results: Of 1,197 patients with an operatively managed ankle fracture (median age 28.7 years), 516 (43.2%) were obese. There were 434 (36.3%) unimalleolar fractures, 396 (33.1%) bimalleolar fractures, 294 (24.6%) trimalleolar fractures, and 73 (6.1%) pilon fractures. Obesity represented 39.4% (n=171) of unimalleolar fractures, 42.7% (n=169) of bimalleolar fractures, 50.0% (n=147) of trimalleolar fractures, and 39.7% (n=29) of pilon fractures (P<0.037). There were 273 (62.9%) lateral malleolar fractures, 127 (29.3%) medial malleolar fractures, and 34 (7.8%) posterior malleolar fractures. Obesity represented 45.4% (n=124) of lateral malleolar fractures, 29.1% (n=37) of medial malleolar fractures, and 29.4% (n=10) of posterior malleolar fractures (P<0.004). Obese patients had a higher probability of a trimalleolar fracture compared to a unimalleolar (OR 1.54; 95% CI, 1.14-2.07; P=0.005) as well as having a lateral malleolar fracture compared to a medial malleolar (OR 2.02; 95% CI, 1.29-3.18; P=0.002). Conclusion: This review of all operatively treated ankle fractures at a level 1, academic trauma center suggests that obesity is associated with increasing severity of ankle fracture patterns, with the exception of pilon fractures. Obese patients have a higher probability of having a trimalleolar fracture than a unimalleolar fracture. Obese patients are also more likely to have a lateral malleolar fracture compared to a medial malleolar fracture. Patients and clinicians should be aware of this higher risk of trimalleolar fractures as these fractures are commonly associated with worse outcomes and a higher probability of developing osteoarthritis.