Figure 1.

Steroid osteonecrosis of the femoral head: (a–d) represents the coronal section of a necrotic femoral head specimen (a), the corresponding CT sectional image (b), and MR T₁ weighted (T1W) (c) and T₂ weighted (T2W) images (d), respectively. There were four distinct layers on the coronal sectional specimen: cartilage (black arrowhead), necrotic area (black arrow), brownish boundary area (white arrows) and extralesional area. CT and MR could clearly show the necrotic, boundary and surrounding normal areas on the specimen. The boundary region was shown as high signal density line on the CT image (white arrows), low signal intensity band on MR T1W and T2W images. Compared with normal tissue, the necrotic region was shown as isodense on CT and isointense on MR images (black arrows).