We analyzed three factors involved in fractures and dislocations of the cervical spine and their relation to the degree of injury of the spinal cord. The three factors were the space available for the spinal cord at the level of the injury the sagittal diameter of the spinal canal at the uninjured levels, and the Pavlov ratio at the uninjured levels. Of the 288 patients analyzed, eighty three had a complete injury of the spinal cord, ninety-two had an incomplete injury of the spinal cord, thirty had an isolated nerve-root, injury, and eighty-three had no neurological deficit. The mean space available for the spinal cord at the level of the injury was 10.5 millimeters for the patients who had a complete injury of the spinal cord, 13.1 millimeters for those who had an incomplete injury of the spinal cord, 15.9 millimeters for those who had an isolated nerve-root injury, and 16.7 millimeters for those who had no neurological deficit. The difference between the groups was significant (p < 0.001) except for the difference between the patients who had an isolated nerve-root injury and those who had no neurological deficit. The mean sagittal diameter of the canal at the uninjured levels was 16.1 millimeters for the patients who had a complete injury of the spinal cord, 16.1 millimeters for those who had an incomplete injury of the spinal cord, 17.9 millimeters for those who had an isolated nerve-root injury, and 18.1 millimeters for those who had no neurological deficit. The difference between the patients who had a complete injury of the spinal cord and those who had an incomplete injury of the spinal cord and that between the patients who had an isolated nerve-root injury and those who had no neurological deficit were not significant (p > 0.05). However, the patients who had a complete injury of the spinal cord and those who had an incomplete injury of the spinal cord were significantly different from the patients who had an isolated nerve-root injury and those who had no neurological deficit (p < 0.001). The mean Pavlov ratio at the uninjured levels was 0.82 for the patients who had a complete injury of the spinal cord, 0.84 for those who had an incomplete injury of the spinal cord, 0.96 for those who had an isolated nerve-root injury, and 0.96 for those who had no neurological deficit. The difference between the patients who had a complete injury of the spinal cord and those who had an incomplete injury of the spinal cord and that between the patients who had an isolated nerve-root injury and those who had no neurological deficit were not significant (p > 0.05). However, the patients who had a complete Injury of the spinal cord and those who had an incomplete injury were significantly different from the patients who had an isolated nerve-root injury and those who had no neurological deficit (p < 0.005). These findings demonstrated quantitatively that the severity of the injury of the spinal cord was in part associated with the space available for the cord after the injury, as measured on plain lateral radiographs. In addition, the patients who sustained a permanent injury of the cord had had a narrower sagittal diameter of the spinal canal before the injury. Patients who have a large sagittal diameter of the canal may be more likely to be spared a permanent injury of the spinal cord following a fracture or dislocation of the cervical spine compared with patients who have a narrow canal.
