[Osteonecrosis of the femoral head. MRI study of 60 cases]

Normal and pathologic femoral heads have been studied by MRI at 1.5 Tesla. The study was centered upon avascular necrosis (53 lesions). Twenty normal subjects and three patients with algodystrophy were examined. The osteonecrosis patterns were established from known lesions. A low signal rim surrounds an upper polar zone of conserved (Type I) or decreased (Type II) signal. The lesions age correlates significantly with their type: amongst type I lesions, 6 are asymptomatic and the 21 others have a mean age of 5.5 months; Type II lesions have a mean age of 12.7 months. Fourteen lesions were not seen on plain radiographs and six were not detected by bone scan. The older lesions with femoral head deformation are better depicted by standard radiologic techniques. Conservatively MRI is the most efficient examination for recent avascular necrosis lesions.