Study of magnetic resonance imaging in transient osteoporosis of the hip.

To better define the magnetic resonance imaging (MRI) features during transient osteoporosis of the hip, we carried out sequential MRI of 8 patients with transient osteoporosis of the hip showing the typical radiographic pattern of diffuse osteoporosis of the femoral head. These cases displayed the same MRI changes in the femoral head and neck characterized by low signal intensity on the T1 weighted images and high signal intensity on the T2 weighted images. The MRI signal became normal within 11 months, but surprisingly, migration of the MRI abnormalities was observed during the course of the disease in 5 cases: abnormal MRI signals were first observed in the anterior area, then migrated to the posterior part, while a normal MRI signal reappeared in the anterior part. We conclude that MRI seems to show some particular features in transient osteoporosis of the hip, which normalize after a few months of evolution; this could represent a migration of MRI abnormalities. Such findings could help in the differential diagnosis of hip diseases such as aseptic bone necrosis.