Objective: To determine asymptomatic avascular osteonecrosis (AVN) of the hip in new patients diagnosed as Systemic Lupus Erythematosus (SLE) in Ramathibodi Hospital.
Material and Method: A prospective descriptive study of new SLE patients with asymptomatic hip at the Rheumatology clinic of Ramathobodi Hospital was conducted from February 2005 to November 2005. The information of steroid and immunosuppressive drug treatment was recorded. Plain film (AP and frog leg views) and MR study of both hips were analyzed.
Results: Twenty-two hips (11 patients) were enrolled in the present study (women 100%; mean age 27.8 years; range 16-50). Four hips (2 patients, 18%) had AVN, without other abnormal imaging findings of the hips and pelvis. Seventeen hips of nine patients had joint effusion; none of them had AVN. No marrow edema, secondary osteoarthritis, collapsed femoral head or pelvic insufficiency fracture in all patients is detected. In the present study, the 2 AVN patients had longest duration of steroid treatment before MR study (105 & 99 days) and rather high cumulative dose of prednisolone or its equivalent dose (4,920 & 4,540 mg), compared to non-AVN patients.
Conclusion: SLE patients without hip pain may have AVN of the hips. Joint effusion and marrow edema do not necessarily associate with early AVN, and the authors found early AVN without joint effusion. Cumulative dose and duration of steroid treatment seem to relate to AVN in the present study. However, a larger number of cases, prospective clinical data, and long-term follow up will help better evaluate the prevalence of asymptomatic AVN of the hips, as well as to evaluate the benefit of MRI as a screening tool for patients at risk of AVN.

Keywords: Avascular necrosis, Steroid, Magnetic resonance imaging (MRI)