Atypical Subtrochanteric Femoral Fractures in Patients with Skeletal Malignant Involvement Treated with Intravenous Bisphosphonates

Background: Atypical subtrochanteric femoral fractures have been identified as a potential complication of long-term bisphosphonate therapy for the treatment of osteoporosis. Patients with skeletal malignant involvement, who receive much higher cumulative doses of bisphosphonates than do patients with osteoporosis, may be at higher risk for the development of these fractures. Methods: A retrospective review of the imaging studies and case notes was done for patients with skeletal malignant involvement who received a minimum of twenty-four doses of intravenous bisphosphonates between 2004 and 2007 and were followed until death or the time of the latest review. Patients were classified as having an atypical subtrochanteric femoral fracture if they had a transverse subtrochanteric fracture following low-energy trauma or an impending fracture, together with radiographic findings of diffuse diaphyseal cortical thickening and cortical beaking at the subtrochanteric area. Results: In the study cohort of 327 patients, we identified four patients who developed an atypical subtrochanteric femoral fracture. All four patients were female, three had breast cancer, and one had myeloma. There was no significant difference between patients who developed an atypical subtrochanteric femoral fracture and those who did not with regard to the doses of intravenous bisphosphonates or the duration of treatment. Conclusions: The prevalence of atypical subtrochanteric femoral fractures in patients with skeletal malignant involvement who are managed with high doses of intravenous bisphosphonates is low. All patients in our study who had development of these fractures had prodromal symptoms of thigh pain.