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Atypical Femoral Fracture — SCE Rheumatology MCQ

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ModerateMetabolic Bone DiseaseAtypical Femoral FractureSCE Rheumatology

A 65-year-old woman with rheumatoid arthritis has received weekly oral alendronate for 8 years. She develops gradually worsening thigh pain without a fall or recent increase in physical activity. A femoral radiograph shows focal thickening of the lateral diaphyseal cortex and a transverse lucent line originating at the lateral cortex, without a destructive bone lesion. What is the most likely diagnosis?

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Correct answer: A — Bisphosphonate-associated atypical femoral fracture

The diagnosis is a bisphosphonate-associated atypical femoral fracture. These fractures occur in the subtrochanteric or diaphyseal femur, usually after minimal or no trauma, and may be preceded by weeks or months of thigh or groin pain. A transverse fracture line beginning at the lateral cortex with focal cortical thickening or “beaking” is characteristic. Long-term bisphosphonate exposure, particularly beyond 3–5 years, increases the risk, although the absolute risk remains low. An exercise-related fatigue fracture requires a relevant repetitive-loading history and lacks this classic drug-associated pattern. Metastatic fracture would usually show a destructive lesion, while typical osteoporotic hip fractures generally involve the femoral neck or intertrochanteric region after a fall. Paget disease would produce features such as bone expansion, cortical thickening and coarsened trabeculation beyond the focal fracture site.

Reference: Sandoz Limited. Alendronic Acid 70 mg Film-coated Tablets, Summary of Product Characteristics, sections 4.4 and 4.8. Updated 18 March 2026. https://www.medicines.org.uk/emc/product/101969/smpc