A 72-year-old woman on long-term bisphosphonate therapy for osteoporosis presents with thigh pain for 2 months. X-ray shows a transverse cortical stress fracture of the subtrochanteric femur with lateral cortical beaking. This pattern is MOST consistent with:
- A Pathological fracture from metastatic disease
- B Stress fracture secondary to osteoporosis (insufficiency fracture)
- C Atypical femoral fracture associated with prolonged bisphosphonate use ✓
- D Paget's sarcoma presenting as a transverse fracture
Explanation
Atypical femoral fractures (AFF) are a recognized complication of long-term bisphosphonate therapy. They are characterised by: transverse or short oblique orientation, subtrochanteric or diaphyseal location, lateral cortical beaking (focal cortical thickening), and a prodrome of thigh/groin pain. The American Society for Bone and Mineral Research (ASBMR) task force criteria require these specific radiological features. Pathological fractures from metastasis are typically lytic and irregular; insufficiency fractures in osteoporosis usually occur in the femoral neck or vertebrae and lack beaking; Paget sarcoma is extremely rare and shows aggressive lytic destruction.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
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Written and medically reviewed by the StethoPrep medical team.