Avascular necrosis of the hip in systemic lupus erythematosus: the role of magnetic resonance imaging.

The value of magnetic resonance imaging (MRI) in the early diagnosis of avascular necrosis (AVN) of the hip in SLE was investigated. Twenty females with severe SLE were studied prospectively. Each underwent 6-monthly X-rays, technetium -99m (Tc-99m) pyrophosphate bone scans and MRI of the hips over a 3-yr period. AVN was diagnosed in five hips of three patients (15%) during the study period. It was confirmed histologically in three hips of two patients who underwent core decompression. Radiological evidence of AVN was present in two patients at diagnosis. One patient developed progressive radiological changes despite core decompression. Bone scintigraphy was abnormal at some stage in all three patients with AVN however failed to detect the early ischaemic stage of AVN. MRI was the most reliable investigation and was able to detect asymptomatic AVN prior to the appearance of radiological or scintigraphic abnormalities.