2024 Volume 15 Issue 8 Pages 1079-1083
Although decompression is the basic surgical treatment for lumbar spinal canal stenosis, its endpoint is unclear in many manuals. Last year we reported on the importance of adequate decompression at the level of the intervertebral disc, since the compression site in spinal canal stenosis is at the disc level. In spinal canal stenosis, the cauda equina and nerve roots are compressed within the spinal canal. Because the cauda equina within the dural sac is relatively free to move, decompression of the dural sac itself is not always necessary to the lateral border. In contrast, the nerve root is less mobile, so sufficient decompression to the lateral border of the nerve root is necessary. On the other hand, the branching of nerve roots from the dural sac is known to vary with lumbar spine level. Therefore, if the nerve root has already branched at the cephalad level of the intervertebral disc, decompression at the intervertebral disc is necessary to the more lateral side, and if the nerve root branches caudal to the intervertebral disc, it is not necessary to the lateral border.
The purpose of this study was to investigate the relationship between nerve root bifurcation from the dural sac and the intervertebral disc by lumbar spine level using a CT after myelography and to determine the relationship with the endpoint of decompression surgery.
The subjects were 50 patients who underwent myelography during lumbar disc herniation surgery at our hospital. The bifurcation was defined as the point at which the nerve root begins to bifurcate from the dural sac, using a horizontal section of a CT after myelography.
The results showed that the nerve root branch was located cephalad of the caudal margin of the intervertebral disc in L3: 0%, L4: 6%, L5: 58%, and S1: 96% of the cases.
In vertebrae more cephalad than L3/4, the nerve root bifurcates caudal to the intervertebral disc, so it is not always necessary to reach the lateral border of the dural sac. However, more than half of the cases in L4/5 and almost all cases in L5/S require adequate decompression to the lateral border of the nerve root at the intervertebral disc because the nerve root bifurcation is more cephalad than the caudal margin of the intervertebral disc.
