What are osteochondroma (exostosis) spinal tumors?

Updated: Nov 01, 2018
  • Author: Andrew A Sama, MD; Chief Editor: Jeffrey A Goldstein, MD  more...
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Osteochondromas make up 4% of all solitary spine tumors. [19]  They also are commonly referred to as exostosis. Spinal lesions are encountered in 7-9% of patients with multiple hereditary exostoses (MHE). Osteochondromas occur in patients aged 20-30 years. Patients with MHE tend to develop the osteochondroma at a younger age; they also tend to experience neurologic deficits and myelopathy more frequently (77% of the time) than the patient with solitary osteochondroma (34%). A male predominance exists.

Osteochondromas are more common in the cervical spine, especially at C2. The posterior elements usually are involved. The lesions are believed to arise secondary to trapping of the physeal cartilage outside the growth plate during skeletal development.

Making the diagnosis of osteochondroma in the spine on plain radiography can be difficult unless the lesion is large and protruding posteriorly from a spinous process. In fact, 15% of patients with osteochondromas of the spine have normal appearing x-rays. CT is the study of choice for detecting the exostosis and determining its relation to the surrounding soft tissue and spinal canal.

T1-weighted MRI reveals a central area of high signal intensity, which represents yellow marrow. This area has intermediate intensity on T2-weighted images. The cortex of the exostosis has low signal intensity. The hyaline cartilage cap of the exostosis is best evaluated with MRI and appears with low signal intensity on T1 and high intensity on T2. The cartilage cap should be less than 2 cm in adults. Lesions with cartilage caps greater than 2 cm should be suspected of malignant transformation to chondrosarcoma.

Qualitatively, the bone composing an osteochondroma is normal. Abnormal bone growth occurs at and as a result of the cartilage cap. A continuity of the lesion with the marrow and cortex of the underlying bone is present. The exostosis may be sessile or pedunculated.

Complete surgical resection is usually curative. Clinical symptoms improve in 89% of patients following removal of the exostosis. Incomplete resection can lead to recurrence of the lesion.

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