Wavy pelvis sign in CT of multiple hereditary osteochondromatosis.

We report three patients with multiple hereditary osteochondromatosis with pelvic CT findings indicating the presence of multiple small osteochondromata. Despite normal appearance of plain radiography in these cases, a characteristic wavy appearance of pelvic brim, which has not been described to date, was clearly shown in all three cases. The finding of wavy pelvis may indicate that pelvic osteochondromata are not as rare as indicated by plain radiographic studies and that malignant degeneration in pelvic osteochondromata may be related to their high incidence. One of these patients had an intracapsular hip joint loose body, originating from femoral neck osteochondroma. This complication is previously unreported.