MRI-detected double low-intensity bands in osteonecrosis of the femoral head

When treating osteonecrosis of the femoral head (ONFH), it is important to define the site and size of necrotic lesions, in general based on the detection of the demarcating area. Although a plain radiograph is routinely performed, it does not always make the lesion clear, especially in early stage cases. On the other hand, magnetic resonance (MR) imaging usually detects the necrotic lesion more clearly even at the early stage [1, 2], and therefore MR imaging is widely used in both the diagnosis and the selection of treatment for ONFH [3, 4].