Atypical femoral fractures and bisphosphonate use: current evidence and clinical implications

Abstract

Osteoporosis is a disease characterized by a low bone volume and deterioration of the bone quality, which increases the risk of low-energy fractures. Bisphosphonate (BP) treatment increases the bone mass and reduces the risk of fractures in patients with osteoporosis by suppressing bone resorption. In spite of its clinical benefits, the long-term use of BPs has been linked to the occurrence of atypical femoral fractures (AFFs). Although the evidence had been controversial regarding the association between the occurrence of AFFs and BP use, more recent studies with radiographic adjudication have indicated the significant associations between them. However, the pathogenesis of AFFs is not completely understood. The most popular hypothesis has suggested that the suppression of bone turnover by BPs is responsible; however, some recent reports have implied the involvement of pathophysiological alterations of the bone quality and fracture repair process. In this review, we summarize and discuss the epidemiology, risk factors and pathology of AFFs.

Keywords: atypical femoral fracture; bisphosphonate; epidemiology; femoral geometry; lower limb alignment; pathogenesis; risk factor.

Figure 1.

Lower limb alignment and location of AFFs [Saita et al. 2014b]. Standing full-length lower-limb radiographs in patients with subtrochanteric AFF (a) and femoral shaft AFF with bowed femur (b) are shown. Dotted lines indicate mechanical axes of lower limb. White arrows indicate fracture location of AFFs. In patient (a), the right femur sustained complete fracture, while the left femur sustained incomplete fracture with periosteal and endosteal focal hypertrophy in the lateral cortex. Mechanical axes path through knee joint in patient (a) but does not in patient (b). AFF, atypical femoral fracture.