CLINICALLY OCCULT AVASCULAR NECROSIS OF THE HIP IN SYSTEMIC LUPUS-ERYTHEMATOSUS

Objective. To study the natural history of clinically occult avascular necrosis (AVN) of the hip in patients with systemic lupus erythematos us (SLE). Methods. Sixty-six patients with SLE (without symptoms refer able to the hip) receiving at least 5 mg/day prednisone for greater th an or equal to 6 months were screened by magnetic resonance imaging (M RI) for AVN of the hip. A complete MRI evaluating class and percentage of femoral head involvement, AP and lateral radiographs of the hips, bone scant and physical examination were performed for patients with p ositive MRI. Medical records were reviewed for serologic and clinical variables that might predict AVN. Repeat MRI were obtained at 3, 6, an d 12, months to assess possible progression or resolution of the lesio n. Patients with negative screening MRI underwent repeat screening aft er one year to assess the one year incidence rate. Results. Eleven asy mptomatic hips (8%) in 8 patients (12%) had MRI documented AVN. The pe rcentage of femoral head involvement ranged from 1 to 46%. One lesion was MRI class B, the remaining lesions were class A. The radiographic stage of 10 hips was stage 1, the MRI class B hip was stage 2. Risk fa ctors for clinically occult AVN included Afro-American origin, Raynaud 's phenomenon, migraine headaches, and a maximal corticosteroid dose o f at least 30 mg/day. After 12 months, 43 of 58 patients with an initi ally negative MRI underwent repeat screening examinations; no new lesi ons were observed. Conclusion. Clinically occult AVN of the hip is com mon in patients with SLE. The short term natural history of these lesi ons appears stable without spontaneous healing or clinical or radiogra phic progression. Risk factors for these asymptomatic lesions ore simi lar to the risks for symptomatic AVN and surgical intervention appears not to be indicated in these patients.