MUSCLE IMPINGEMENT - MR-IMAGING OF A PAINFUL COMPLICATION OF OSTEOCHONDROMAS

The purpose of this study was to describe the magnetic resonance (MR) appearance of a newly recognized complication of osteochondromas. Two patients presented with pain and swelling over known osteochondromas. Plain radiographic studies were unrevealing. MR examinations were obta ined to characterize the exostoses further and evaluate areas of palpa ble fullness. Increased signal was present in the muscles on T2-weight ed images, which correlated with physical findings and was believed to represent muscle injury due to the osteochondroma. Pain and fullness may result from a number of osteochondroma-related complications, the most worrisome of which is malignant degeneration. Muscular impingemen t and injury should be considered in the differential diagnosis of pai n and swelling in the region of an exostosis. MR imaging allows distin ction of this entity, which may be radiographically occult and confuse d clinically with fracture, bursitis, or malignant degeneration.