In addition, there is an adjacent region of decreased density which likely represents adjacent fat. These findings are consistent with a well-marginated cartilaginous cap measuring approximately 1.5 cm. These findings are highly characteristic for osteochondroma. Osteochondromas represent a developmental growth defect where there is lateral growth of the epiphyseal cartilage plate instead of the normal downward growth toward the metaphysis. Osteochondromas are most often located in the long tubular bone but may on occasion be located in other unusual places such as small bones of the hands or the spine.
Vertebral osteochondromas predominate in posterior osseous elements.
All osteochondromas have a direct communication with the cortex as well as narrow cavity. The majority of osteochondromas are solitary in nature, but there is a hereditary form in which patients have multiple exostoses. Osteochondromas generally are nontender, painless, and slow-growing to the time of epiphyseal closure, after which time they undergo little if any growth. However, when an osteochondroma becomes large, or is in certain anatomic sites, it can lead to symptoms with potential complications. An osteochondroma is characterized radiographically by an osseous protuberance arising from the external surface of a bone demonstrating corticomedullary continuity.