[Changes in lumbosacral canal length during flexion and extension--dynamic effect on the elongated spinal cord in the tethered spinal cord].

This clinical research has been conducted to extend the understanding of pathophysiological mechanism involved in the tethered cord syndrome. In normal individuals, the filum terminale has elasticity similar to the rubber band. This allows cephalad or caudad movement of the lumbosacrococcygeal spinal cord while the spine is flexed or extended. This is based on the observation that the lowest pair of dentate ligaments spans from the T12 and L1 junction of cord segments to the dura between the dural exit of T12 and L1 nerve roots, and the spinal cord below T12 can freely ascends on flexion and descends in the spinal canal on extension of the spine. In 50 healthy human subjects, x-ray films of the thoracolumbosacral spine were studied. Lateral films of the spine were taken in the neutral, hyperextended and hyperflexed positions. The first group included 10 individuals whose ages ranged from 27 to 42 years. The distance between the middle of the T10 vertebra and L1-L2 interspace was measured. This distance was considered to represent the length of the lumbosacral cord segment (L1 through coccygeal cord segments). The second group included 40 individuals whose ages ranged from 17 to 50 years. The distance between the L1-L2 interspace and S1-S2 interspace was measured. The distance signified the distance between the caudal end of the spinal cord and attachment of filum terminale to the sacrum. There was a 3.5% (4.6mm by X-ray films) increase during hyperflexion in the distance measured in the first study.(ABSTRACT TRUNCATED AT 250 WORDS)