Background: Extension of a vertebral exostosis into the spinal canal is rare, but many isolated cases have been reported in the literature. Three existing patients with multiple hereditary exostoses at our institution had development of neurologic findings and were found to have exostoses in the spinal canal. These findings led us to perform magnetic resonance imaging or computed tomographic scans for the remaining patients with multiple hereditary exostoses at our institution.

Methods: Forty-four patients at our institution (including twenty-six male patients and eighteen female patients) had multiple hereditary exostoses. Forty-three patients were evaluated with magnetic resonance imaging and one was evaluated with computed tomography to look for spinal column involvement.

Results: Thirty (68%) of the forty-four patients had exostoses arising from the spinal column, and twelve (27%) had lesions encroaching into the spinal canal. Thirty-six of the forty-four patients also had plain radiographs, but only six had radiographs that accurately identified the lesions and another six had radiographs that mistakenly identified lesions that were not confirmed with magnetic resonance imaging or computed tomography. Patients with lesions inside the spinal canal were typically asymptomatic and neurologically normal, with radiographs that did not demonstrate the lesion. Compared with female patients, male patients were more likely to have spinal lesions and more likely to have lesions encroaching into the spinal canal (p = 0.014).

Conclusions: The risk that a patient with multiple hereditary exostoses has a lesion within the spinal canal is much higher than previously suspected (27%). Because the potential exists for serious neurologic injury to occur, we have begun to use magnetic resonance imaging to screen all patients who have multiple hereditary exostoses at least once during the growing years.