Effect of Body Mass Index on Femur Fracture Location: A Retrospective Database Study

Objectives:Use a large database design and multivariable analyses to assess the associations between body mass index (BMI) and femur fracture patterns after controlling for other risk factors.Design:Retrospective cohort study.Setting:National insurance claims database of patient records from 2010 to 2018.Patients/Participants:Patients with femur fracture diagnoses were identified. Patients with multiple fractures within 1 week (polytrauma patients), patients without a BMI diagnosis code within 6 months of fracture, and patients with multiple BMI diagnosis codes (implying a substantial change in weight) were excluded.Intervention:N/A.Main Outcome Measurements:Patients were divided into groups based on fracture location: Proximal (OTA/AO 31), shaft (OTA/AO 32), or distal (OTA/AO 33). The distribution of femur fractures was compared across BMI categories.Results:A total of 57,042 patients with femur fracture were identified: 45,586 proximal fractures, 4216 shaft fractures, and 7240 distal fractures. Patients with BMI <29.9 have increased odds (P < 0.0001) of proximal fracture and decreased odds (P < 0.0001) of shaft or distal fractures. Patients with BMI >30.0 have decreased odds (P < 0.0001) of proximal fracture and increased odds (P < 0.0001) of distal fractures.Conclusions:Increasing BMI is associated with a decreased proportion of proximal femur fractures and a corresponding increase in the proportion of shaft and distal fractures. Regression analyses determined that age, sex, osteoporosis, diabetes, and tobacco use are not the cause of this trend.Level of Evidence:Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.