Lumbar spinal canal morphometry from computed tomography scans: reproducibility, results and clinical implications

The reproducibility of measurements of the lumbar spine taken from computed tomography (CT) scans was assessed. The overall variaton in 53 patients scanned on more than one occasion was only 2.8%. Factors which reduced the reproducibility were increasing angle of scan from the mid-discal plane, measurement of oblique structures and measurement of dimensions with soft-tissue boundaries. Measurements from 142 patients are presented and compared with both other published series and the results from 17 patients with spinal stenosis. Whereas the sagittal diameter of the bony canal and the interpedicular distance of the patients with spinal stenosis did not differ from the control group, a new measurement described in this paper, the oblique sub-facet distance, demonstrated significant differences between the two groups.