Is It a Simple Stress Fracture or Bisphosphonate-related Atypical Fracture?
A 76-year old woman visited our out-patient clinic in May 2010 complaining of a left thigh pain while walking. Medical history taking revealed a diagnosis of a left femur neck fracture fixed with a DHS in July 2006, and in January 2010, she had undergone surgery due to a right distal radius and ulnar fracture and a right femoral intertrochanteric fracture. She had been treated with 70 mg alendronate per week since 2006. A physical examination revealed no limitation of range of motion of the left hip joint, and a radiologic evaluation, including a computed tomography scan, showed no suspicious lesion, such as, hypertrophied cortical bone or a fracture line on the left proximal femoral shaft area. However, a bone scan showed increased uptake in the proximal femoral area just below the fixed plate (). The average T-score of bone mineral density was -3.9 for lumber spine. She was managed conservative treatment using analgesics, and the anti-osteoporosis medication was continued.\nIn June 2011, she was transferred from a local hospital due to left thigh pain. The pain started after rising from a sitting position without any trauma history. Pelvic plain anteroposterior radiography revealed a displaced subtrochanteric fracture at the left femur. The fracture site was located at the contact margin at the end of the plate. The characteristics of fracture were cortical hypertrophy, medical spike, and a transverse fracture line, which are features commonly associated with atypical femoral subtrochanteric fracture. On the other hand, the fracture line is just distal to the DHS plate where the maximal stress is concentrated which is a definite feature commonly presented at stress related fatigue fracture. The fracture was fixed by replacing the 2 hole DHS plate with a with a 6 hole plate. Alendronate was stopped after reoperation, and six months after the reoperation the patient was asymptomatic and the fracture had united without any complication ().