Background/Purpose: To study the prevalence of osteonecrosis (ON) in patients with systemic lupus erythematosus (SLE) and to identify the risk factors for development of this complication and predictors of total hip/knee arthroplasty.

Methods: The sample comprised 243 patients with SLE treated between 1980 and 2013 at a tertiary university hospital that does not attend pediatric populations. Patients were registered in a specific database. Patients with ON were selected for analysis. The diagnosis was confirmed in all cases with imaging techniques (conventional radiography and bone scan, CT scan or MRI). The variables associated with the occurrence of this complication were analyzed using a backward logistic regression model.

Results: During the follow-up period, 11 patients (4.5%) had 12 episodes of ON (one patient developed two). The mean age of the patients (nine women) was 52 ± 15 years and median time to progression of SLE at the time of diagnosis of ON was 149 months (range: 24-323). Three out of 11 cases of ON (27%) occurred within the first five years of the course of the disease.

The condition was monoarticular in eight episodes (66%) and multifocal in four (34%); in the latter case it simultaneously affected two or more joints (range 2-4). The most common site was the femoral head (75% of episodes), followed by the knee (33%) and the humeral head (8%). In 90% of the affected joints, ON presented with pain and functional impotence (the asymptomatic joints were detected in the scintigraphic study).

The mean dose of prednisone at the time of diagnosis of ON was 11 ± 8.2 mg/day and the total cumulative dose was 30.4 ± 16.7 g. Seven patients (64%) had received a prednisone dose of at least 0.5 mg/kg/day at some point of the disease; 5 (45%) of these had received a dose of 1 mg/kg/day for serious complications. However, at the time of ON diagnosis, disease was inactive or mild in all patients according to the SLEDAI score (mean 1.3, range 0-4).

Antiphospholipid antibodies were positive in two patients (18%); both were on antiplatelet therapy. We did not identify any other risk factors that have been associated with the development of ON in SLE.

Outcome was unfavorable in seven patients (64%), who required total hip/knee replacement. There was no increase in mortality.

Both in the comparisons between groups using univariate analysis and in the multivariate analysis, the only predictor of risk for development of this complication was the total cumulative prednisone dose (OR = 19.07 [95% CI: 2.7 – 133.7], p = 0.0002). No associations were found with the presence of antiphospholipid antibodies, immunosuppressive therapy, presence of arthritis or degree of disease activity according to the SLEDAI. In the Cox proportional hazards model, advanced radiological stage was the only statistically significant predictor for arthroplasty.

Conclusion: ON is a rare complication in patients with SLE (4.5%). In the majority of the cases it is symptomatic and occurs in advanced stages of the disease. The major risk factor associated with the development of this complication is the cumulative dose of glucocorticoids. ON was not associated with increased mortality, but it was associated with physical disability.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/osteonecrosis-in-patients-with-systemic-lupus-erythematosus-risk-factors-and-clinical-outcome/