Predictors of Osteonecrosis in Systemic Lupus Erythematosus: A Prospective Cohort Study

Objective. We aimed at determining the predictors of osteonecrosis (ON) in a longitudinal lupus cohort. Methods. Data were reviewed from the initiation of the cohort in 1987 until October 2019. In total, 2,428 patients were included in the analysis based on 224,295 person-months of follow-up. We used pooled logistic regression to assess the relationship between risk factors and rates of ON events. After identifying a set of variables related to ON incidence, we fit a final multivariable model to identify the most important risk factors for incident ON. Results. In 18,691 person-years of follow-up after cohort entry, 122 incident ON events were observed (rate = 6.5/ 1,000 person-years). In the multivariable analysis, African American patients were at twice the risk for ON compared to White patients. Male patients and smokers had an increased risk for ON of similar to 80% and 50% compared to female patients and nonsmokers, respectively. For every 10-year increase in the age at diagnosis, there was a 20% reduced risk for ON. Patients diagnosed after the 1990s had a 50% reduced risk of ON compared to those diagnosed before the 1990s. A highest daily dosage of prednisone of 40 mg or higher, even when administered for a month or less, significantly increased the risk of ON. Use of pulse methylprednisolone or intramuscular trianncinolone was not associated with an increased risk of ON. Conclusion. African American patients with systemic lupus erythematosus are at double the risk of experiencing ON compared to White patients. Oral prednisone at 20-39 mg for more than 1 month, or 40 mg daily for even 1 month, at any point in the disease course, remained the most important glucocorticoid predictor of ON.