Atypical Femoral Fracture — SCE Rheumatology MCQ

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ModerateMetabolic Bone DiseaseAtypical Femoral FractureSCE Rheumatology

A 70-year-old woman who has taken oral alendronic acid for osteoporosis for 7 years reports 3 months of atraumatic mid-thigh pain. A femoral radiograph shows focal lateral cortical thickening with a transverse lucent line originating in the lateral cortex and extending medially, but not across the full width of the femur. What is the most likely diagnosis?

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Correct answer: C — Incomplete atypical femoral fracture

This is an incomplete atypical femoral fracture. The discriminating features are prolonged alendronate exposure, atraumatic prodromal thigh pain, focal lateral cortical beaking and a transverse lucency beginning at the lateral cortex. It is incomplete because the fracture line has not crossed the full femoral shaft. A conventional fatigue stress fracture lacks this characteristic antiresorptive-associated pattern. A Pagetic fissure fracture would arise in otherwise radiographically abnormal Pagetic bone, while an osteomalacic pseudofracture usually occurs with evidence of defective mineralisation. Metastatic fractures generally have an underlying destructive or infiltrative bone lesion. The contralateral femur should also be assessed because atypical femoral fractures may be bilateral. Alendronate should be withheld or discontinuation considered pending specialist evaluation and an individual benefit–risk assessment.

Reference: Electronic Medicines Compendium. Alendronic Acid 70 mg tablets, Summary of Product Characteristics, sections 4.2 and 4.4: Atypical fractures of the femur. Updated 2026. https://www.medicines.org.uk/emc/product/5206/smpc