Predictors of atypical femoral fractures during long term bisphosphonate therapy: A case series & review of literature

BACKGROUND & OBJECTIVES: Bisphosphonates (BPs) are the most widely prescribed medicines for the treatment of osteoporosis because of their efficacy and favourable safety profile. There have been, several reports on an increased incidence of atypical femoral fractures after long term treatment with BPs. The objective of this study was to evaluate the clinical presentation including prodromal symptoms, skeletal radiograph findings, type and duration of BPs received and treatment outcome of patients who developed atypical femoral fractures during bisphosphonate therapy. METHODS: In this retrospective study, eight patients with atypical femoral fractures were analysed based on clinical features, biochemical and radiological investigations. RESULTS: Of the eight patients, who sustained atypical femoral fractures, six were on alendronate and two were on zoledronate therapy before the fractures. In addition to BPs, two patients were on long term corticosteroid therapy for rheumatoid arthritis and Addison's disease. Three patients had bilateral atypical femoral fractures. Except one, all of them had prodromal symptoms prior to fracture. Skeletal radiograph showed cortical thickening, pointed (beaking of) cortical margin and transverse fracture in meta-diaphyseal location. Serum calcium, phosphate, alkaline phosphatase (ALP) and intact parathyroid hormone (iPTH) concentrations were within the reference range in all patients. INTERPRETATION & CONCLUSIONS: Long term bisphosphonate therapy may increase the risk of atypical femoral fractures. Presence of prodromal pain, thickened cortex with cortical beaking may be an early clue for predicting the atypical fractures. High risk patients need periodical skeletal survey and a close follow up for early detection of cases.