Morphometric analysis of the cervical spinal canal on MRI

Abstract

Two useful numerical values, called the Torg ratio and the spinal canal diameter (SC diameter) are widely accepted as reliable morphometric determinants of spinal stenosis. The aims of the study were to examine morphometric determinants of the cervical spinal canal on MRI in both sexes and analyse them as reliable indicators of spinal stenosis. Measurements were made on 50 MR images (sagittal T2 weighted images from C3 to C7) of the cervical spine of patients from the Emergency Centre who had undertaken MRI of the cervical spine in addition to CT for various diagnostic indications. Torg ratio, used in evaluation of the spinal canal stenosis on plain x-ray radiographs, cannot be used as a spinal canal stenosis indicator due to the gender differences in the vertebral bodies’ width. Sagittal canal diameters were more spread out in males than in females. MRI enables the value of the space available for the spinal cord, (SAC) to be determined, by subtracting the sagittal diameter of the spinal cord from the sagittal diameter of the spinal canal. Not gender, but individual and level differences in the SAC values were evident (cervical cord enlargement). SAC values relied more on the spinal canal than on the spinal cord, so that the differences in the dimensions of the spinal cord accounted for less variability in the SAC values. MR imaging of the cervical spine provides more accurate cervical canal and spinal cord measurements that could serve as morphometric determinants of the cervical canal stenosis.