Atypical femoral fracture after long-term alendronate treatment: report of a case evidenced with magnetic resonance imaging.

Postmenopausal osteoporosis is commonly treated with alendronate, one of the bisphosphonates used for the prevention and treatment of osteoporotic fractures. However, the correlation between atypical femoral fractures and long-term bisphosphonate therapy has not been clearly identified. We report here the case of a 69-year-old woman with postmenopausal osteoporosis who presented with an atypical femoral subtrochanteric fracture on magnetic resonance imaging (MRI) confirmation after having received alendronate therapy for about 3 years. The fracture united after refixation and after administration of alendronate was stopped. Several published reports were reviewed, and some clinical characteristics of this atraumatic fracture were revealed, including the clinical symptoms of thigh pain, stress reaction or stress fracture, and transverse fracture with unicortical beak in an area of cortical hypertrophy. In addition to a regular radiographic survey, MRI, which may provide early information, and bone biopsy for pathologic analysis may be used as tools for early detection and final diagnosis. Once an insufficiency fracture is suspected or proved to be related to bisphosphonate, the withholding of bisphosphonate should be highly recommended to enhance fracture healing. Prophylactic fixation should be considered if fracture healing is not good or if the patient cannot tolerate protection of weight-bearing.