Corticosteroid-associated avascular necrosis: dose relationships and early diagnosis.

Corticosteroids are the most common etiological factor in nontraumatic avascular necrosis (AVN) of bone, accounting for about 10% of arthroplasties performed annually in the United States. Evidence is conflicting on the relative importance of peak dose, daily dose, or cumulative dose, and most likely all three represent "high dose" corticosteroid administration and play a role in AVN. The etiology may be multifactorial with corticosteroids superimposed on genetic or pathological predispositions. Joint preservation depends upon early diagnosis and treatment before fracture of the subchondral trabeculae and joint incongruity. Early intervention depends upon identifying at-risk patients and quantifying their risk by understanding clinical and pathophysiological contributions to that risk. Our data and that of others suggest that a screening MRI of at-risk populations will permit detection of AVN at a prefracture stage when preservation of the joint is possible.