MRI of transient osteoporosis of the hip.

Among the available imaging techniques such as conventional radiography, radionuclide bone scan, and computed tomography (CT), magnetic resonance imaging (MRI) has made significant contributions to the diagnosis of acute hip joint disease in adults by enabling early differentiation between such conditions as idiopathic avascular femoral head necrosis, septic coxitis, degenerative disease, and tumors. In this study we investigated the use of MRI for evaluation of patients with transient osteoporosis (TO). MRI with T1- and T2-weighted sequences in coronal, transverse, and sagittal sections was performed in 12 patients with retrospectively confirmed TO, both at the onset of the disease and later as follow-up procedure. MRI revealed three typical stages of TO: a diffuse stage, a focal stage, and a residual stage. Characteristic symptoms of TO are hip pain and a need for protective splinting of the hip joint. Conventional radiographs show demineralization of the hip joint without joint space narrowing. Clinical, radiologic, and MRI findings normalize within 6-10 months, indicating that TO has a good prognosis with complete restoration of bone density.