Atypical subtrochanteric and femoral shaft fractures and possible association with bisphosphonates.

Several case series and multiple individual case reports suggest that some subtrochanteric and femoral shaft fractures might occur in patients who have been treated with long-term bisphosphonates. Several unique clinical and radiographic features are emerging: prodromal thigh pain prior to the fracture, complete absence of trauma precipitating the fracture, and bilateral fractures in some patients. Radiographic features include presence of stress reaction, transverse or short oblique fractures, and thick femoral cortices. The overall incidence of subtrochanteric and shaft fractures combined is below 30 per 100,000 person-years, so this type of fracture is much less common than proximal femur (hip) fracture. Furthermore, the unique "atypical" fracture type is a subset of all subtrochanteric and femoral shaft fractures. The putative mechanism is unknown, and more research is needed to identify distinctive characteristics and the pathophysiology of these atypical fractures. There is no rationale to withhold bisphosphonate therapy from patients with osteoporosis, although continued use of bisphosphonate therapy beyond a treatment period of 3 to 5 years should be re-evaluated annually.