osteonecrosis / avascular necrosis bone (AVN)

Introduction

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⁾

Aetiology

atraumatic

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