Factors associated with atypical femoral fracture.

We aimed to investigate the proportion of atypical femoral fractures (AFF) among Korean femoral fracture patients and examined the factors associated with the development of AFF. Between 2003 and 2013, 607 female patients with low-energy femoral fractures who were hospitalized at a single university hospital were retrospectively enrolled in this study. Patients were classified into two groups according to the fracture site: Patients with subtrochanteric or diaphyseal femoral fractures were included in the AFF group, while patients with intertrochanteric or neck fractures were included in the typical femoral fracture (TFF) group. After comparing clinical and radiographic characteristics between groups, we used multivariable logistic regression analysis to explore risk factors for AFF. Thirty patients (4.9 %) with AFF and 577 patients (95.1 %) with TFF were identified. The AFF group was younger than the TFF group (p < 0.01), and more patients with AFF were treated with bisphosphonate (BP) (p < 0.01) or proton-pump inhibitor (p = 0.02). When comparing the radiographic parameters, the AFF group tended to have a higher cortical thickness index (p = 0.02) and lateral-to-medial cortex ratio (p < 0.01). After adjusting for clinical variables, BP use (OR 8.09, CI 3.09-21.19) and younger age (OR 1.06, CI 1.01-1.11) were associated with AFF. The proportion of AFF was 4.9 % among patients with femoral fractures. Younger age and use of BP before fracture increased the risk of development of AFF in Korean patients.