The 5-year follow-up of a cortical stress fracture resulting in a spontaneous atypical subtrochanteric femoral fracture in a female patient with severe osteoporosis and bisphosphonate therapy over 15 years.

Atypical fractures under long term treatment with bisphosphonates (BP) have been reported, although no causal connection has been known. As an explanation the suppression of bone turnover with poor bone metabolism and consequently deterioration of bone microarchitecture has been suggested. In our case we describe retrospectively the course of radiological and clinical changes in a 75 years old female patient who has been treated with oral BP due to postmenopausal osteoporosis over 15 years. After 10 years of treatment she developed a cortical stress fracture in the subtrochanteric region of the femoral shaft, which finally caused a spontaneous atypical subtrochanteric fracture 5 years later.