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Incomplete atypical femoral fracture associated with long-term bisphosphonate therapy — SCE Rheumatology MCQ

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ModerateFracture ManagementIncomplete atypical femoral fracture associated with long-term bisphosphonate therapySCE Rheumatology

A 72-year-old woman with rheumatoid arthritis and a previous osteoporotic vertebral fracture has taken alendronic acid 70 mg weekly for 8 years. She develops progressive left lateral thigh pain over 6 weeks without preceding trauma. The pain is now present on weight-bearing. Plain radiographs show focal lateral cortical thickening in the proximal femoral diaphysis with a transverse radiolucent line extending through the lateral cortex but not the medial cortex. There is no comminution, displacement or destructive bone lesion. Her adjusted calcium, phosphate, alkaline phosphatase, 25-hydroxyvitamin D and renal function are normal. Which is the most appropriate next management plan?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: E — Withhold alendronic acid, image the contralateral femur and arrange urgent orthopaedic assessment for prophylactic intramedullary nailing

Explanation lettering: B = shown as A · D = shown as B · E = shown as C · C = shown as D · A = shown as E

This is a symptomatic incomplete atypical femoral fracture. The discriminating features are prolonged bisphosphonate exposure, prodromal atraumatic thigh pain, lateral cortical thickening and a transverse fracture line confined to the lateral cortex. Alendronic acid should be withheld while the fracture and future osteoporosis treatment are reassessed. Atypical femoral fractures are frequently bilateral, so the contralateral femur requires imaging even if asymptomatic. The visible fracture line and weight-bearing pain indicate a substantial risk of progression to a complete fracture; urgent orthopaedic assessment for prophylactic intramedullary fixation is therefore appropriate. B is inadequate because observation is more defensible for an incomplete lesion without a visible fracture line and with minimal symptoms; delaying assessment here risks completion. C correctly recognises the fixation threshold and bilateral association but continuing the implicated bisphosphonate conflicts with regulatory advice. D is inappropriate because immediate substitution with another potent antiresorptive does not address the impending fracture and denosumab has also been associated with atypical femoral fractures. E is attractive because anabolic therapy may subsequently be considered in selected high-risk patients, but evidence that teriparatide heals conservatively managed incomplete atypical fractures is uncertain, and it must not replace surgical assessment when a symptomatic radiolucent line is present.

Reference: Bisphosphonates: atypical femoral fractures (Published 11 December 2014; article date June 2011) — https://www.gov.uk/drug-safety-update/bisphosphonates-atypical-femoral-fractures Alendronic Acid 70 mg Tablets — Summary of Product Characteristics (Revised May 2026) — https://www.medicines.org.uk/emc/product/100151/smpc Update on Atypical Femoral Fractures (2024) — https://pubmed.ncbi.nlm.nih.gov/39172879/