osteonecrosis / avascular necrosis bone (AVN)

see also:

• orthopaedics in the ED
• corticosteroids

• osteonecrosis / avascular necrosis bone (AVN) is usually a slowly progressive condition which results in significant morbidity
• 90% of atraumatic cases are due to either corticosteroids or chronic alcoholism
• 75% of cases are between 30 years of age and 60 years of age and with the average age in the late 30s with male-to-female ratio is about 4:1 ¹⁾

• corticosteroids
  • glucocorticoid-induced AVN (steroid-associated AN or SAON) causes significant morbidity and accounts for around 10% of all cases of total hip replacement in the US ²⁾
  • 90% of atraumatic AVN is due to glucocorticoid-induced AVN or alocoholism
  • prevalence of glucocorticoid-induced AVN is between 11% and 41% for those taking long term high doses, depending on the underlying diseases, glucocorticoid dosage and route of administration
    • risk factors for SAON include:
      • high cumulative dose
      • long Rx course
      • systemic lupus erythematosus (SLE)
      • renal transplant
      • SARS virus
        • rate ratio (RR) of osteonecrosis was 1.29 (95% CI 1.09–1.53, P = 0.003) for every 10 days of treatment. The relationship was nonlinear.
        • incidence rate increased by 3.6% for every 10 mg increase in the dose with risk mainly in those given over 40mg/day
        • risk was 0.6% in patients receiving less than 3 g of prednisolone equivalent dose and 13% for doses greater than 3 g.³⁾
      • inherited thrombophilia
    • potential risk reduction factors:
      • statins ⁴⁾
      • antioxidants such as vitamin E
  • those exposed to high-dose glucocorticoids with a longer treatment period were considered to be at higher risk of development of AVN as cumulative dose appears to be an important risk factor
  • average interval between initiation of treatment and the first symptoms of hip pain was 33 months, but several cases of osteonecrosis were noted after only 3 months ⁵⁾
• ethanol (alcohol and alcohol withdrawal)
• bisphosphonates
• risk is higher in those with:
  • renal transplants
  • systemic lupus erythematosus (SLE) male-to-female ratio is 7:3
  • radiation Rx

• disruption of blood supply to the bone
  • fracture (eg. scaphoid fractures)
  • joint dislocation
  • damage to nearby blood vessels

• paediatric causes