The present retrospective cohort study assessed the association of body mass index (BMI) with the pattern of ankle fractures using 2 classifications systems. Of the 1011 consecutive patients who underwent surgery for ankle fractures in 2 hospitals from January 2009 to December 2011, 837 had a classifiable fracture according to 1 of 2 classification systems and complete information available for covariates. The association of BMI, adjusted for age, sex, corticosteroid use, diabetes, and smoking status with having a more proximal fibula fracture (Weber class A to C) and an increasing number of malleoli involved (uni-, bi-, or trimalleolar) was assessed using multivariable ordered logistic regression analysis. The mean age of the patients was 50.9 ± 16.9 years, and 461 (55%) were female. On multivariable analysis, BMI and male sex were associated with having a more proximal fibula fracture using the Weber classification, with an odds ratio (OR) of 1.07 (95% confidence interval [CI] 1.04 to 1.11; p < .001) per 1 kg/m2 increase and OR of 2.96 (95% CI 2.13 to 4.11; p < .001) compared with female sex, respectively. Age was not associated with this fracture classification. In an analysis of uni-, bi-, and trimalleolar fractures, age per 10 years showed higher odds (OR 1.24, 95% CI 1.14 to 1.36; p < .001) and male sex lower odds compared with female sex (OR 0.36, 95% CI 0.27 to 0.48; p < .001) of having trimalleolar fractures than uni- or bimalleolar fractures. An increasing BMI did not seem to be a risk factor, although an inverse U-shaped relationship was seen between quintiles of BMI and the OR of having trimalleolar versus uni- or bimalleolar fractures. Corticosteroid use, diabetes, and smoking status were not significantly associated with the pattern of the ankle fractures using either classification system. In conclusion, an increasing BMI and male sex were risk factors for proximal fibula fractures, and female sex and age were risk factors for bi- and trimalleolar fractures.
Level of Clinical Evidence: 3