Review Question - QID 217501

Continuation of bisphosphonates after atypical femur fractures is associated with the progression of fracture of the contralateral femur.

Atypical femur fractures are typically the result of prolonged bisphosphonate treatment (>5 years) and occur in the presence of altered bone metabolism. The most common region is the subtrochanteric femur which is exposed to tremendous forces. Atypical fractures are characterized by a transverse fracture pattern with a medial spine and thickened lateral cortex. Fractures may be preceded by lateral cortical beaking, which is an abnormal reaction to stress. Fractures are often treated with intramedullary nail fixation and are associated with prolonged healing times, increased complications, and higher reoperation rates. Often, the contralateral femur is affected and can lead to an atypical femur fracture if not closely monitored. Patients reporting current thigh pain in the contralateral femur should be treated with prophylactic nailing. Continuation of bisphosphonates is associated with progression to fracture of the contralateral femur.

Lee et al. performed a retrospective study of 53 patients that were treated for complete atypical femur fractures and monitored for the progression on the contralateral side. They reported a 34% progression rate and an average of 25.6 months which was significantly associated with post-operative bisphosphonate treatment. The authors concluded post-operative bisphosphonate use was associated with the progression of the contralateral femur.

Koh et al. performed a retrospective study of 33 patients with femoral cortical stress lesions. They reported all cases (4 patients) with a dreaded black line eventually fractured and all cases that resulted in fractures (12 patients) reported antecedent thigh pain. They concluded cortical stress reaction from long-term bisphosphonate treatment is associated with atypical femur fractures.

Shane et al. reviewed the epidemiology, pathogenesis, and medical management of atypical femur fractures. They reported the relative risk of an atypical femur fracture for patients taking bisphosphonate is high, the absolute risk remains relatively low, but may increase with longer treatment duration. They concluded discontinuation of bisphosphonates can decrease the risk of atypical femur fractures and there is inconsistent evidence to support advanced healing with teriparatide.

Figure A is an AP radiograph of the left hip with an atypical femur fracture characterized by a transverse fracture pattern, medial spike, and thickened lateral cortex. Figure B is an AP radiograph of the right proximal femur with a stress reaction in the subtrochanteric region and thickened lateral cortex.

Incorrect answers
Answer 1: Longer bisphosphonate use is associated with a higher risk of fracture progression with most studies reporting average use >5 years.
Answer 3: Asian race has been associated with an increased risk of atypical femur fractures.
Answer 4: The presence of a varus proximal femur is associated with an increased risk of atypical femur fracture progression.
Answer 5: Gender has not been associated with the progression of atypical femur fractures, but they do occur more frequently in females due to the higher incidence of osteoporosis.