Review Question - QID 4533

The patient's injury is most consistent with a bisphosphonate induced atypical femur fracture.

Atypical subtrochanteric femoral fractures have been identified as a potential complication of long-term bisphosphonate therapy for the treatment of osteoporosis. Prodromal symptoms of thigh pain are common prior to fracture, and bony failure is usually associated with low energy mechanisms.

Puhaindran et al. performed a retrospective review of the imaging studies and case notes for patients with skeletal malignant involvement who received a minimum of twenty-four doses of intravenous bisphosphonates. Patients were classified as having an atypical subtrochanteric femoral fracture if they had a transverse subtrochanteric fracture following low-energy trauma or an impending fracture, together with radiographic findings. In the study cohort of 327 patients, four patients developed an atypical subtrochanteric femoral fracture. All four patients were female, three had breast cancer, and one had myeloma.

Feldman et al. reviewed the imaging presentations on routine radiographs, alternate imaging modalities, and associated pitfalls in nine atypical femur fractures in six patients. The author states that effects may differ with each bisphosphonate's route of administration and prolongation of activity, despite discontinuation. The review also discusses the theoretical mechanisms of bisphosphonates as a class rather than with a specific alendronate association and provides a broader basis for evaluating the recently observed clinical and radiographic complications.

Figure A shows a transverse subtrochanteric femur fracture. Figure B shows diaphyseal cortical thickening and cortical beaking at the subtrochanteric area.

Incorrect Answers:
Answer 1: The radiographic findings are not consistent with a fibrous cortical defect.
Answer 2: The radiographic findings are not consistent with the presence of a metastatic lesion.
Answer 3: Subtrochanteric fractures are typically associated with high energy trauma, and this patients mechanism of injury is atypical.
Answer 5: There is no radiographic or clinical evidence supporting the presence of chronic osteomyelits.