Background Osteonecrosis of the femoral head (ONF) occurs frequently (3–40%) in patients who receive corticosteroid therapy for SLE. MRI can accurately visualize pathological abnormalities of the femoral head, being much more sensitive than plain radiography. To analyze the risk factors associated with steroid-induced ONF, the best approach would be to examine early changes in the femoral head using MRI and any early clinical events attributable to steroid therapy. For treatment of SLE, a number of strategies may be selected according to the clinical conditions of patients, and treatments may differ slightly among hospitals. Therefore, for better clarification of the background factors associated with ONF, the optimum approach would be to analyze the treatment strategy, selection of steroid, initial dose of steroid and drugs used together with steroid in a cohort of patients treated at a single hospital.
Objectives To clarify the factors related to silent ONF in patients with SLE treated at a single institution.
Methods One hundred six patients (12 males and 94 females) with SLE were selected on the basis of having been newly diagnosed and requiring high-dose prednisolone, including pulse therapy with methylprednisolone, as the initial treatment. All the patients initially underwent plain radiography and MRI at the start of corticosteroid treatment to detect any early changes in the femoral head, and subsequent examinations were performed three months later. Laboratory parameters were evaluated at the start of steroid treatment and one month thereafter. All statistical analyses were performed with SPSS v. 13 (SPSS Inc., Chicago, IL, USA). Differences demonstrated by 2-tailed tests were considered statistically significant at P (two-sided) <0.05, and marginally significant at P=0.05–0.10.
Results By three months after the start of corticosteroid treatment, asymptomatic ONF was diagnosed by MRI in 30 patients (28.3%), being bilateral in 17 and unilateral in 13. Serological activity (C3, C4, CH50 and anti-ds DNA antibody), renal function (eGFR, serum creatinine and urinary protein), anti-phospholipid antibodies, and SLEDAI were not correlated with asymptomatic ONF. BMI, BSA, and the initial dose of prednisolone per unit body weight, BMI and BSA were also not correlated with asymptpmatic ONF. No preventive effect of ONF was observed by pretreatment with statins. However, patients with angiitis and a elevated total cholesterol level at 4 weeks after the start of steroid treatment tended to show a higher incidence of ONF. Patients with a higher triglyceride level both before and 4 weeks after the start of steroid treatment showed a significantly higher frequency of asymptomatic ONF (P<0.001).
Conclusions Asymptomatic ONF is common in patients with SLE. A high triglyceride level is a significant risk factor for ONF, and large epidemiologic surveys would help to shed light on early events such as silent ONF in patients receiving steroid therapy.
Acknowledgements This study was supported by a research grant from the Research Committee on Idiopathic Osteonecrosis of the Femoral Head of the Ministry of Health, Labour, and Welfare of Japan.
Disclosure of Interest None declared