Corticosteroid treatment is a major predictor of osteonecrosis in patients with systemic lupus erythematosus (SLE); a daily dose of 20 to 39 mg of prednisone for more than 1 month or prednisone greater than 40 mg per month is associated with an increased risk for osteonecrosis, according to study results published in Arthritis Care & Research.
Osteonecrosis, most commonly seen in the femoral head, is a serious complication of SLE. The objective of the current study was to identify predictors of osteonecrosis in patients with SLE.
Using data from the Hopkins Lupus Cohort, a longitudinal cohort of patients with SLE at the Johns Hopkins Hospital, the researchers assessed the impact of prednisone dose and duration as predictors of osteonecrosis. The diagnosis for osteonecrosis was based on the Systemic Lupus International Collaborating Clinics/American College of Rheumatology (SLICC/ACR) Damage Index using imaging data.
Data from 2428 patients were included in the analysis, based on a total of 224,295 person-months of follow-up (approximately 18,691 person-years). During follow-up, a total of 122 incident events of osteonecrosis occurred, with an incidence rate of 6.5 per 1000 person-years.
In the multivariable analysis, risk factors for osteonecrosis included African American ethnicity (age-adjusted rate ratio, 2.27; 95% CI, 1.56-3.30, P <.0001) and male gender (age-adjusted rate ratio, 1.80; 95% CI, 1.05-3.08; P=.0340). Furthermore, smokers vs nonsmokers had a 50% increased risk for osteonecrosis. Risk for osteonecrosis decreased by 20% with every 10-year increase in age, and patients diagnosed after the 1990s had a 70% reduced risk for osteonecrosis compared with those diagnosed before the 1980s.
Risk for osteonecrosis was significantly increased with a daily prednisone dose of 20 to 39 mg for more than 1 month compared with a daily dose of less than 20 mg (rate ratio, 3.48; P =.0044). Risk for osteonecrosis was also greater with a daily prednisone dose of 40 to 59 mg, even when administered for 1 month (rate ratio, 4.14; P =.0012). Risk for osteonecrosis increased further with a daily prednisone dose of greater than 60 mg, whether it was administered for 1 month (rate ratio, 10.12) or more (rate ratio, 8.32; both P <.0001).
Use of pulse methylprednisolone or intramuscular triamcinolone was not associated with an increased risk for osteonecrosis.
The study had several limitations, such as the inclusion of patients evaluated for osteonecrosis after it became symptomatic, the exclusion of patients with osteonecrosis prior to study entry, and the considerable African American representation with a higher risk for osteonecrosis.
“Our study highlighted that the risk [for] oral prednisone is both dose- and duration-dependent. A daily prednisone dose of 20 [to] 39 mg increased the risk [for osteonecrosis] when administered for more than  month. A daily dose of 40 mg or more, even when administered for  month, predicted an even higher increased risk [for osteonecrosis],” the researchers wrote.
Kallas R, Li J, Petri M. Predictors of osteonecrosis in systemic lupus erythematosus: A prospective cohort study. Arthritis Care Res (Hoboken). Published online December 20, 2020. doi:10.1002/acr.24541