A 70-year-old woman on long-term bisphosphonate therapy (alendronate 10 years) presents with a fracture of the subtrochanteric femur after minimal trauma. X-ray shows a transverse fracture with cortical thickening ('beaking') of the lateral cortex. This pattern is most consistent with:

• A Pathological fracture through a bone metastasis
• B Osteomalacic insufficiency fracture (Looser zone)
• C Paget's disease sarcomatous transformation fracture
• D Atypical femoral fracture (AFF) — bisphosphonate-associated stress fracture of the subtrochanteric/femoral shaft region due to suppressed bone remodelling ✓

Explanation

Atypical femoral fractures (AFF) are a recognised rare complication of prolonged bisphosphonate use (>3–5 years), resulting from over-suppression of bone remodelling which impairs micro-crack repair. The American Society for Bone and Mineral Research (ASBMR) major criteria include: transverse or short oblique configuration, subtrochanteric or femoral shaft location, non-comminuted, prodromal thigh pain, lateral cortical beaking (stress reaction at the tension cortex). Bilateral screening X-rays are mandatory. Management involves withdrawing bisphosphonate, initiating teriparatide to stimulate bone formation, and prophylactic IM nailing of the contralateral side if incomplete AFF is identified. Looser zones are bilateral symmetrical pseudofractures in osteomalacia at characteristic sites.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.