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trauma

Atypical Femoral Fracture

advanced
6 min
26 marks
6 questions
Clinical Scenario
A 76-year-old woman presents after sudden onset of left thigh pain while walking across her living room. She has been on alendronate for 9 years for osteoporosis. She reports prodromal left thigh pain for 4 months. Examination reveals a shortened, externally rotated left leg with proximal thigh tenderness. She also mentions occasional right thigh discomfort.
AP radiograph of the proximal femur showing transverse subtrochanteric fracture with classic atypical features: lateral cortical beaking (spike), localized periosteal/endosteal thickening, minimal comminution, and transverse orientation. Note the medial cortical thickening representing stress reaction.
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AP radiograph of the proximal femur showing transverse subtrochanteric fracture with classic atypical features: lateral cortical beaking (spike), localized periosteal/endosteal thickening, minimal comminution, and transverse orientation. Note the medial cortical thickening representing stress reaction.

Image source: Open Access medical literature (NIH/PubMed Central) • CC-BY License

Questions

Question 1 (4 marks)

What is the diagnosis and describe the ASBMR criteria that define this condition.

Question 2 (4 marks)

Explain the pathophysiology of atypical femoral fractures and the role of bisphosphonates.

Question 3 (5 marks)

What are the challenges in surgical management and how do you address them?

Question 4 (6 marks)

Describe your surgical technique for fixation of this fracture.

Question 5 (4 marks)

What medical management and investigations are required post-operatively?

Question 6 (3 marks)

The patient mentions right thigh discomfort. How do you evaluate and manage this?

Exam Day Cheat Sheet

Must Mention

  • •ASBMR criteria: 4 of 5 major features required
  • •Lateral cortical beaking = pathognomonic
  • •Transverse pattern, minimal comminution, prodromal pain
  • •FULL-LENGTH cephalomedullary nail (protect entire femur)
  • •Blocking screws to prevent varus
  • •Check contralateral femur (25-50% bilateral)
  • •Drug holiday + teriparatide

Common Pitfalls

  • •Not recognizing atypical fracture pattern (lateral beaking, transverse)
  • •Short nail that doesn't protect entire femur
  • •Varus malreduction from lateral cortex defect
  • •Not using blocking screws
  • •Not imaging contralateral femur (25-50% bilateral)
  • •Not stopping bisphosphonate (drug holiday essential)
  • •Not considering teriparatide for delayed healing
  • •Expecting rapid union (delayed union is typical)