Atypical Subtrochanteric Femur Fracture in Patient with Metastatic Breast Cancer Treated with Zoledronic Acid

Several case series have suggested an association exists between atypical femoral subtrochanteric fractures and long-term use of bisphosphonates. It is thought that prolonged use of bisphosphonates may lead to adynamic, fragile bone. The radiologic features of atypical fractures include diffuse cortical thickening, transverse fracture, and beaking at the lateral subtrochanteric area. Atypical subtrochanteric femur fractures have been reported after use of alendronate, but there have been rare reports of atypical femur fractures occurring after administration of zoledronic acid. A 56-year-old female with metastatic breast cancer treated with zoledronic acid presented with pain in the right hip. X-rays showed a right subtrochanteric fracture, and she underwent operation. Four months later after having undergone an operation, the patient struggled with walking and X-ray showed delayed union of the fracture site.