Low-dose corticosteroids and avascular necrosis of the hip and knee

Background - Although high-dose corticosteroid use constitutes a well-known risk factor for avascular necrosis (AVN), the risk of AVN with low-dose corticosteroids is not well established. Objective - To assess AVN risk for high-dose and low-dose oral corticosteroid exposure compared to baseline risk. Methods - We employed a nested case-control study design. AVN of the hip and knee was determined from coded diagnoses and full text record review. Corticosteroid exposure was ascertained through outpatient automated pharmacy dispensing files. Results - Thirty-one cases occurred during approximately 720,000 person years. Eleven of 22 cases that met all eligibility criteria received oral corticosteroids during the 3 years before diagnosis. There was a cumulative dose-related corticosteroid effect from no excess risk (relative risk = 0, 95% Confidence Interval = 0-5) for doses 1-430 mg, to a relative risk of 6 (95% CI 1-43) for doses of 440-1290 mg, and an undefined relative risk (95% Lower CI 26) for doses greater than 1290 mg. Conclusions - Systemic corticosteroids were strongly associated with AVN, however, the effect was not clearly evident at 3-year cumulative doses less than or equal to 430 mg. Copyright (C) 2000 John Wiley & Sons, Ltd.