Dynamic changes in longitudinal stretching of the spinal cord in thoracic spine: Focus on the spinal cord occupation rate of dural sac.

OBJECTIVES

This study aimed to evaluate the anteroposterior diameters and cross-sectional areas of the dural sac and spinal cord in the thoracic spine, to elucidate the spinal cord occupation rate of the dural sac in these dynamic changes for each level using multidetector-row computed tomography (MDCT).

PATIENTS AND

METHODS

Fifty patients with cervical or lumbar spinal disease were prospectively enrolled. After preoperative myelography, MDCT was performed at maximum passive flexion and extension. The anteroposterior diameter and cross-sectional area of the dural sac and spinal cord in the axial plane and the thoracic spinal cord length in the sagittal plane were measured. The spinal cord occupation rate in the dural sac was calculated.

RESULTS

The spinal cord occupation rate of the dural sac in anteroposterior diameter was lower on flexion than on extension, with significant differences from the T1/T2 to T11/T12 levels (p < 0.0001). The spinal cord occupation rate of the dural sac in cross-sectional area was lower on flexion than on extension, with significant differences except from T3/T4 to T6/T7 levels (p < 0.01). There was a bimodal increase in the occupation rate with elevations at the cervicothoracic junction and thoracolumbar junction. The thoracic spinal cord length on flexion was significantly longer than that on extension (p < 0.0001).

CONCLUSIONS

The spinal cord occupation rate of the dural sac was lower on flexion than on extension, despite thoracic spine being considered a rigid region. The dynamic changes in longitudinal stretching and shrinkage of the spinal cord affected the occupation rate.