Femoral-head osteonecrosis

Early avascular necrosis of the femoral head. Patchy sclerosis seen within the superior aspect of the femoral head. Corresponding signal abnormality seen on the coronal STIR MRI (arrowheads).
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Femoral-head osteonecrosis

Characteristics

  • Occurs most commonly in the 20–50 age group.
  • Bilateral: 50% of idiopathic cases, or 80% in steroid-induced cases.
  • Commonly seen following intracapsular fractures of the femoral neck. Increased risk if displaced (up to 80%).
  • Risk factors: steroid use, alcohol abuse, metabolic disease (e.g. Gaucher’s disease), vasculitis (SLE), sickle cell disease, occupational causes (e.g. deep sea divers – caisson disease), venous thromboembolism and bone-marrow transplant.

Clinical features

  • Classically present with pain of insidious onset.
  • Pain often worse at night.
  • Pain is usually severe but may become more bearable after several weeks.

Radiological features

  • The initial radiograph if taken early may be normal.
  • The affected bone becomes sclerotic with later collapse and remodelling.
  • Ficat staging (1968 Ficat and Arlet).
    • 0 – pre-clinical – not included in original classification – normal X-ray and MRI.
    • 1 – pre-radiological – pain, normal X-ray, early MR changes.
    • 2 – sclerosis on X-ray but congruent head.
    • 3 – flattened head with crescent sign.
    • 4 – secondary degenerative changes.

Management

  • Remove any causative factors.
  • Management is targeted towards preservation/restoration of vascularity where possible, or reconstruction in late disease.
  • Techniques used in each disease stage include:
    • 1 – core decompression.
    • 2 – core decompression and strut graft (free or vascularised).
    • 3 – strut graft/total hip replacement.
    • 4 – total hip replacement.

Reference

James R. D. M., Erskine J. H., Rakesh R. M. (2008). Musculoskeletal Radiology. A-Z Musculoskeletal and Trauma Radiology, 1st edition, Cambridge University Press, Cambridge, 1, 1-176.

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