Atypical femoral fracture following bisphosphonate treatment in a woman with osteogenesis imperfecta—a case report

A 75-year-old woman presented with acute pain and deformity of her right lower extremity after a fall from standing height. She had suffered from diffuse pain in the right thigh for 4 months, which had begun after some physical exercise with no trauma. Radiographs revealed an atypical fracture of the right femoral shaft, short oblique, with thickening of the entire lateral cortex (9.3 mm as compared to 7.2 mm at the same level on the contralateral nailed femur) and localized cortical reaction at the level of the fracture (Figure). Figure. The atypical fracture of the right femur. The patient had been diagnosed in childhood with a familial form of osteogenesis imperfecta caused by a de novo mutation. Her parents and siblings had no evidence of bone fragility, but 5 of her 6 children had had multiple fractures starting in childhood, associated with typical clinical signs of type-I collagen abnormalities (Rauch and Glorieux 2004). Since childhood, our patient had sustained at least 35 fractures, all of which had healed within a normal period of time. The first to be documented was a femoral fracture at the age of 2, followed by many others involving tibia, radius, ulna, humerus, fingers and toes, bilaterally, until the age of 12. From 12 to 27 years of age there were no fractures reported. At the age of 27 the patient had sustained a wrist fracture, and at the age of 35 she had presented with multiple vertebral compression fractures after falling from a tree. More recent events included a high-energy left midshaft femoral fracture during sports at the age of 62, followed by a fracture of the great toe when she was 71. Because of multiple fractures and osteoporosis (the femoral neck T-score dropped to –2.8 standard deviation when she was 72), she had been administered alendronate (70 mg/week) for the following 3 years, together with calcium and vitamin D supplements (Calcimagon-D3 2 tablets/day). Prior to that, she had been on estrogen replacement therapy (Estraderm day patch) for 13 years. Efficacy of treatment was determined by repeated densitometric evaluations and bone resorption level measurements; the deoxypyridinoline/creatinine ratio was 11 when she was 68 years old, 17 at the age of 72, and 12 one year later (normal range: 8–20). The patient’s femoral fracture was stabilized with an intramedullary nail. Her postoperative course was uneventful and she was discharged 12 days after surgery. At 1-year follow-up, the fracture was well healed. Alendronate was discontinued a few weeks after the atypical fracture.