The developmental segmental sagittal diameter of the cervical spinal canal in patients with cervical spondylosis.

The role of the narrow cervical spinal canal in the expression of clinical syndromes in the cervical spine was investigated in a retrospective review of 63 patients with symptomatic cervical spondylosis refractory to conservative therapy. The measurement of the developmental segmental sagittal diameter, determined at the level of the pedicle, and of the spondylotic segmental sagittal diameter, determined at the level of the disc, were applied. When divided into groups based on anatomic variance around an average size midcervical diameter of 17 mm, 40 patients were found to have less than the average size of midcervical canal. A spondylosis index was computed for the narrow canal group at 2.08 mm per segment and for the wide canal group at 3.29. Canal dimensions are determinants of symptom production and neurologic compromise.