This study investigated the relationship between cervical spine sagittal canal diameter and neurologic injury in cases of spinal fracture-dislocation. A group of 98 patients with such injuries was reviewed; 45 had no neurologic deficits, 39 had incomplete quadriplegia, and 14 had complete quadriplegia. Spinal canal sagittal diameter was measured in all, and large diameter and small canals were defined. Small diameter canals were correlated significantly with neurologic injury, while large diameter canals allowed protection from neurologic injury in cervical fracture dislocation.