'The bigger they come ...': the relationship between body mass index and severity of ankle fractures.

Ankle fractures requiring either manipulation under anaesthetic or open reduction and internal fixation can lead to prolonged morbidity. This prospective study investigates the possible relationship between obesity and the severity of ankle fractures following low velocity injuries. The body mass index (BMI) of patients with displaced malleolar fractures was compared with that of patients with undisplaced malleolar fractures. A BMI of 18 to 25 kg/m2 is considered to be the 'desirable' range for both men and women. Fractures considered 'severe' were those associated with disruption of the ankle joint, with more than one malleolar fragment, and requiring manipulation under anaesthesia or open reduction and internal fixation. The mean BMI of patients with displaced fractures (28.25 kg/m2) was significantly higher than that (24.58 kg/m2) of those with undisplaced fractures (P = 0.0001). Obesity is associated with increased severity of ankle fractures following low velocity injuries.