6. Lumbosacral Spine

Figure 6.1 illustrates the surface anatomy of the LS spine. The LS spine is typically composed of five vertebrae (see Fig. 6.2). Unlike the cervical spine, whose facets allow for multidirectional movement, the primary motion of the L spine is flexion and extension with some side bending. The spinal cord itself ends around L1 or L2, but spinal nerves continue down the canal as the cauda equina. Each nerve root exits the bony spinal canal hugging the pedicle and is named for that vertebra. At each level, the exiting nerve leaves the canal just above the disk, and another traversing nerve exits at the next level. When disk herniations occur, the traversing nerve usually is affected, while if the facet joints are involved, the exiting nerve root will be affected. (See Fig. 6.3) [1–3].