Musculoskeletal Imaging

Bone within bone appearance

a radiographic finding in which discrete linear bands are observed beneath the cortical bone. This appearance is caused by formation of an inner layer of new bone in the cortex that does not merge with the overlying cortical bone. It is diagnostic of osteonecrosis and is seen in sickle cell anaemia, Gauchers disease, sarcoidosis and osteopetrosis. Also, see osteopetrosis (III:1), Fig. 1.

A similar finding with ghost vertebra may be seen in children who have received injections of the contrast agent thorium dioxide in dextran (Thorotrast). This agent causes temporary growth arrest, and the size of the ghost vertebra corresponds to the size it was at the time of injection.

DR