We determined the predictors of osteonecrosis in a longitudinal lupus cohort, emphasizing the role of maximal prednisone dose and duration.
Data from 2428 patients were included in the analysis based on 224295 person-months of follow-up. We used pooled logistic regression to assess the relationship between risk factors and rates of osteonecrosis. After identifying a set of variables related to osteonecrosis incidence, we fit a final multivariable model to identify the most important risk factors for incident osteonecrosis.
In 18691 person-years of follow up after cohort entry, 122 incident osteonecrosis event were observed. In the multivariable analysis, African-Americans had twice the risk of osteonecrosis compared to Caucasians. Males and smokers had 80% and 50% increased risk of osteonecrosis compared to females and non-smokers, respectively. For every 10 year increase in the age of diagnosis, there was a 20% reduced risk of osteonecrosis. Patients diagnosed after the 1990's had a 50% reduced risk of osteonecrosis compared to those diagnosed before the 1990's. A daily dose of prednisone of 20-39 mg or higher, when administered for more than a month, or a daily prednisone dose of 40 mg or higher, even when administered for one month, significantly increased the risk of osteonecrosis. Use of pulse methylprednisolone or intramuscular triamcinolone was not associated with an increased risk of osteonecrosis.
Oral prednisone at 20-39 mg for more than one month, or 40 mg daily for even one month remained the most important corticosteroid predictor of osteonecrosis.