The cross-sectional area and the sagittal and transverse diameters of
the cervical spinal canal were measured, using high-resolution,
thin-section computerized-tomography images, in 100 control subjects and
forty-two patients who had a traumatic injury to the spinal cord. No
significant differences were found between the control and the spinal
cord-injured group with regard to the cross-sectional area of the spinal
canal; however, the differences between the two groups were significant
with regard to mean sagittal and transverse diameters of the spinal canal.
The sagittal diameters of the spinal canal of the control group were
significantly larger than those of the spinal cord-injured group.
Conversely, the transverse diameters of the spinal canal of the spinal
cord-injured group were significantly larger than those of the control
group. These findings suggest that certain patients may be predisposed to
spinal cord injury, given sufficient trauma. It is not the total volume of
space in the spinal canal that is the critical factor; rather, it is the
shape. An index of shape is the ratio of the sagittal to the transverse
diameter. The difference between the two groups, based on the ratio of
sagittal to transverse diameter, was highly significant. Because this
measure is a ratio, there is no need to evaluate an individual on the basis
of measurements of absolute values.