Osteonecrosis/avascular necrosis

• What is it:

  • Lack of blood supply to bone resulting in necrosis and collapse
  • Anyone can be affected but most common in people aged 30-50
  • Most common site = femoral head/hip
  • Other common sites = knee, talus, humeral head, scaphoid bone
  • Less common sites include jaw - secondary to bisphosphonates
• Causes:

  • Idiopathic e.g. Perthes' disease - idiopathic avascular necrosis of femoral epiphysis in children
  • Trauma e.g. NOF fracture, scaphoid fracture
  • Non traumatic - issues with lipid deposition or issues with vessels
• Issues with lipid deposition:

  • Prolonged corticosteroid use - mechanism not fully understood
  • Excess alcohol
  • Hyperlipidaemia
  • Gaucher's disease - missing enzyme to break down lipids and get lipid build up
• Issues with vessels:

  • Smoking
  • Blood disorders e.g. sickle cell, clotting disorders
  • Autoimmune disorders e.g. SLE - side effects of steroids, thromboembolism and vasculitis
  • Cancer treatment - chemotherapy and radiotherapy (directly damages blood supply)
• Symptoms:

  • In non-traumatic cases it can have an insidious onset and take weeks or months for symptoms to appear
  • Minimal early joint pain - usually when weight bearing, pain eases with rest. Can be referred to groin or anterior thigh
  • Increased pain/stiffness as bone collapses - pain at rest or at night
  • Limping
  • Can affect one or both hips
• Examination:

  • Initially examination may be unremarkable, as progresses:
  • Antalgic gate
  • Tenderness around joint
  • Restricted and painful active and passive movement
  • Joint deformity
  • Muscle wasting
  • Neurological deficit where adjacent nerves are impinged
• Investigations:

  • Bloods if looking for underlying cause
  • X-ray can be normal in early disease but useful to look for other differentials e.g. fractures, OA
  • MRI is most sensitive modality
• Management:

  • Complex and need specialist input from orthopaedic team
  • Non surgical - NSAIDs, physio, steroid injections
  • Most people will need surgery as the disease progresses - core decompression, osteotomy, bone graft, total joint replacement