Atypical Femoral Fracture on Long-Term Bisphosphonate
A 68-year-old woman on alendronate for 11 years presents with 3 weeks of dull, aching lateral thigh pain that is worse with weight-bearing. She has no history of trauma. Radiographs show a transverse radiolucent line in the lateral cortex of the subtrochanteric femur with localized cortical thickening ('beaking') and no displacement. She is otherwise healthy, has a T-score of −1.8, and asks whether she should stop her bisphosphonate and whether she needs surgery. She is scheduled for a dental extraction in 6 weeks.
1. What is the diagnosis and how do you counsel her about stopping the bisphosphonate?
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This is an incomplete atypical femoral fracture (AFF) - a judgment question about risk stratification and drug holiday, not just a diagnosis.
Diagnosis: transverse lateral cortical lucency with beaking in the subtrochanteric region, prodromal thigh pain, and long-term bisphosphonate use. This is the classic AFF prodrome. The T-score of −1.8 means she is not in the high-risk osteoporosis category that would argue strongly for continuing.
Stopping the drug: yes, stop the bisphosphonate. Long-term use (>5–7 years) is associated with AFF and osteonecrosis of the jaw; a drug holiday is appropriate, especially with a modest T-score. The antiresorptive effect persists for years, so stopping does not immediately reverse risk but reduces further exposure.
Dental extraction: AFF and ONJ are both bisphosphonate-related; coordinate with the dentist/oral surgeon. A drug holiday before extraction is reasonable, but do not delay urgent dental care; document the risk discussion.
Do not simply reassure her that the pain is 'muscular.' A prodromal AFF can progress to a complete fracture with minimal trauma.
2. Does she need prophylactic surgery now, and what are the criteria and options?
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This is the core judgment call: when to prophylactically fix an incomplete AFF.
Criteria favoring prophylactic fixation:
- Severe prodromal pain limiting activity.
- A radiolucent line involving the lateral cortex with a high risk of completion (e.g., a visible fracture line extending across a substantial portion of the cortex, or a 'dreaded black line').
- Bilateral involvement (screen the other femur).
- Failure of conservative management.
Options:
- Prophylactic intramedullary nailing - the standard for high-risk incomplete AFF. It stabilizes the femur and prevents completion. Use a long, cephalomedullary or reconstruction nail; avoid short nails that can create a stress riser. Be aware of the risk of iatrogenic fracture during reaming and of nonunion (AFFs heal slowly).
- Conservative management - protected weight-bearing, activity modification, and close radiographic follow-up - is reasonable for a minimally symptomatic, non-displaced incomplete AFF without a high-risk line. But this patient has 3 weeks of pain, which pushes toward surgery.
My recommendation: given prodromal pain and a visible lateral cortical line, offer prophylactic IM nailing after discussing risks (nonunion, iatrogenic fracture, reoperation). Screen the contralateral femur with full-length radiographs. If she declines, strict protected weight-bearing and repeat imaging in 4–6 weeks, with clear return precautions.
Key teaching point: do not treat an incomplete AFF like a routine stress fracture; the completion risk and the need for full-length imaging and contralateral screening are what the exam tests.