Figure 1.

A representative 42-year-old female case of steroid-induced osteonecrosis of femoral head (ONFH, ARCO stage IV). (A) Radiographs delineating the crescent sign (red arrow), flattening of the articular surface of femoral head, and osteoarthritic acetabular changes (red dashed circles). (B) Coronal T1- and T2-weighted magnetic resonance images (MRI) highlighting a medium-sized necrotic lesion of the left femoral head (red dashed circles). (C) Gross appearance of sequentially sliced sections of the femoral head obtained at surgery, showing the deformation of the femoral head (red arrow) and subchondral necrotic bone (green arrow). ARCO, Association Research Circulation Osseous.