To evaluate the degree of injury of the spinal cord in relation with the space available for the spinal cord at the level of injury, the sagittal diameter of the spinal canal at the uninjured levels, and the Pavlov ratio at the uninjured levels in fractures and dislocations of the lower cervical spine.

We retrospectively reviewed the records and radiographs of patients who had sustained an acute fracture or dislocation of the cervical spine from 1990 to 1995. We collected patients from Orthopedic and Neurosurgical department of Chonbuk University Hospital and at Orthopedic department of Presbyterian Medical Center. Of the 69 patients analyzed, twelve had no neurological deficit, eleven had an isolated nerve-root injury, twenty-two had an incomplete injury of the spinal cord, and twenty-four had a complete injury. We measured above three parameters from the plain lateral radiographs and assessed the difference by one-way ANOVA and unpaired t-test.

1. The mean space available for the spinal cord at the level of injury was 12.9 millimeter for the complete injury of the spinal cord,13.8 millimeter for the incomplete injury, 14.7 millimeter for an isolated nerve-root injury, and 15.7 millimeter for no neurological deficit group. The overall difference among the groups was significant (F=6.98, P=0.0004). 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 neurologic deficit (P=0.002). 2. The mean sagittal diameter of the canal at the proximal and distal uninjured level was 14.3 and 14.6 millimeter for the complete injury of the spinal cord, 14.9 and 14.9 millimeter for the incomplete injury, 15.5 and 16.6 millimeter for an isolated nerve-root injury, and 16.9 and 16.5 millimeter for no neurological deficit group. 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 neurologic deficit (P=0.001). 3. The mean Pavlov ratio at the proximal and distal uninjured level was 0.90 and 0.86 for no neurologic deficit group, 0.85 and 0.87 for an isolated nerve-root injury, 0.76 and 0.75 for the incomplete injury of the spinal cord, and 0.76 and 0.76 for the complete injury. 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 neurologic deficit (P=0.001).

The patients who sustained a permanent injury of the cord usually had had a narrower sagittal diameter (<14mm) and a lower Pavlov ratio (<0.80) of the spinal canal before injury. Patients who had 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. These findings demonstrated that the severity of the injury of the spinal cord was in part associated with the space available for the cord (at risk:<13mm) after the injury, as measured on plain lateral radiographs.