Functional myelograhy in spondylolisthesis.

Flexion and extension radiographs in myelography in preoperative spondylolisthesis patients were studied. Dural sac motion at the level of the mid-vertebral bodies was essentially anterior in extension. At the level of the intervertebral disc, the motion is obstructed by the disc bulging posteriorly in extension. Axial motion is variable and not linearly correlated with spinal column length change. The dural sac undergoes a localized narrowing at the level of the spondylolisthesis. This becomes more prominent during extension. In 21 cases studied completely, no disc herniation was encountered myelographically of surgically. The anterior epidural space is of a greater value at the level of the spondylolisthesis than reported normal values. The change in this space from dorsiflexion to ventral flexion is much less at the level of olisthesis than either the adjacent areas of a comparable adjacent intervertebral level.