Does the cervical canal to body ratio predict spinal stenosis?

The exact size of the bony cervical spinal canal and the vertebral body was measured in 368 cadaveric adult male vertebrae. A comparison of radiographic and direct measurements was also undertaken. The mean sagittal diameter of the spinal canal for C3-C7 was close to 14 mm (14.07 +/- 1.63 mm; N = 272). The mean ratio of the sagittal canal diameter to the vertebral body diameter (canal to body ratio) was 86.68 +/- 13.70 mm. Thirty-one percent of subaxial vertebrae would be diagnosed as having spinal stenosis if a canal to body ratio of less than 80% was considered abnormal. Measurements from plain radiographs overestimate the canal diameter. The average diameter for the lower cervical spinal canal is about 14 mm. The canal to body ratio is independent of radiographic magnification, but may produce misleading results.