see also:

• hip pain

• avascular necrosis of the femoral head is responsible for some 12% of hip arthroplasties
• incidence tends to be bimodal:
  • as Perthe's disease in pre-pubescent children
  • in adults under age 50 years, especially men aged 30-50.
    • ~70% progress to bilateral disease

• alcohol abuse
• chemotherapy / radiotherapy
• chronic liver disease
• chronic pancreatitis
• coagulopathy
• diabetes mellitus
• gout
• hyperlipidaemia
• pregnancy
• long term corticosteroids
• systemic lupus erythematosus (SLE)
• Gaucher's disease
• sickle cell disease (SCD)

• plain XR hip
  • stages 0 and 1 - usually normal Xray
  • stage 2 - sclerosis, cysts, osteopenia
  • stage 3 - subchondral collapse producing a classic “crescent sign”
  • stages 4 to 6 - collapse of femoral head with destruction of joint in stages 5 and 6
• consider MRI scan if XRay not diagnostic
• early referral to orthopaedics as 80% on non-operative Rx patients progress to total collapse of femoral head necessitating THR.