Factors affecting fracture location in atypical femoral fractures: A cross-sectional study with 147 patients.

INTRODUCTION: Many studies have tried to determine the characteristics of atypical femoral fractures (AFFs) through age-, sex-, and ethnicity-matched comparison with non-AFFs. However, we hypothesized that diaphyseal AFFs would have characteristics different from those of subtrochanteric AFFs. The aim of this study was to evaluate the clinical features of diaphyseal/subtrochanteric AFFs and determine the factors related to fracture location.

PATIENTS AND METHODS: One hundred forty-seven patients with AFF were enrolled, 114 patients (78%) had a history of bisphosphonate use. Forty-nine patients (33%) had bilateral lesion, and 35% of patients had thigh pain. Patients were divided into two groups according to fracture location: 52 patients (35.4%) with subtrochanteric AFF and 95 patients (64.6%) with diaphyseal AFF. The patient demographics and fracture characteristics of the two groups were compared. Multivariate logistic regression analysis was used to adjust for variables related to fracture location.

RESULTS: The patients in the diaphyseal AFFs group were older and had lower BMI, lower BMD, and larger lateral and anterior bowing. Multivariate analysis revealed that age greater than 65 years and low BMD were related with diaphyseal location. With greater lateral bowing angle, the AFF location was moved from the subtrochanteric area to the diaphyseal area.

CONCLUSION: This study demonstrated that patients with diaphyseal AFFs had different characteristics compared with those with subtrochanteric AFFs.