The nerve supply to the intervertebral disc is limited to only the outer annulus through the sinuvertebral nerve. The annulus fibrosus is made of organized collagen I fibers that encircle and maintain the integrity of the inner nucleus pulposus. The nucleus pulposus has a gelatinous composition that allows for dissipation of force and protection against injury. Intervertebral discs are composed of two main components: the nucleus pulposus centrally, and the annulus fibrosus, circumferentially. The intervertebral disc allows for flexibility of the spine while concomitantly conferring strength and shock absorptive ability. Computed tomography (CT) has been found to be a primary imaging modality for demonstrating osteological pathology, including trauma, fractures, scoliosis, and in pre- and postoperative patients. While in the adult spine, the spinal cord typically ends at the level of L1-L2 as the conus medullaris, both dura mater and the filum terminale, which is a ligamentous condensation of pia mater, extends down from the conus through the sacral canal to the coccyx and serves as an anchor for the spinal cord. Within the sacrum itself lies the continuation of the vertebral canal, the sacral canal, that terminates at an apex termed the sacral hiatus. The inferior portion of the sacrum articulates with the coccyx, which is another small triangular bone at the bottom of the spine that is thought, by many, to be a vestigial structure. In addition to the intrinsic stability imparted by the intervening intervertebral disc, this joint is further strengthened by the iliolumbar and lumbosacral ligaments. The sacral promontory, the most anterior part of the sacrum, articulates with L5, forming part of the lumbosacral joint. With the exception of the L5-S1 intervertebral disc, due to ultimate fusion of the sacral vertebrae by adulthood, the sacral segments are not typically separated by intervertebral discs.
The five sacral vertebrae are fused together to form the sacrum, an upside-down triangular bone that resides at the base of the lumbar spine. Stability is further conferred to the lumbar spine through the anterior and posterior longitudinal ligaments that run vertically on the ventral and dorsal aspects of the vertebral column, respectively. Intervertebral discs are cartilaginous structures that provide additional cushioning between each vertebra. The larger bodies are a testament to the lumbar region’s duty to bear a significant proportion of the weight of the upper limbs and trunk. They have characteristically larger vertebral bodies, and shorter, thicker spinous processes. The lumbar vertebrae have several unique properties that distinguish them from vertebrae of other vertebral levels. They therefore are integral to the overall function of the spine, including its ability to move, bear-weight, and maintain proper alignment. The seven processes of vertebrae serve as both origin and insertion points of the paraspinal muscles. Approximately 20% of the axial load placed on the lumbosacral spine is transmitted through the facet joints.
The superior and inferior processes articulate with the inferior and superior processes of the adjacent vertebrae, respectively, to create the facet joints. Each vertebra has additional inferior processes. From this, bony intersections arise the transverse processes, which are present bilaterally. The arches contain pedicles on each side that predominantly blend into the superior articular process.
The vertebral arches and the dorsal part of the vertebral body along the vertebral column collectively form the spinal canal that houses the thecal sac. The vertebral bodies are responsible for absorbing most of the axial forces exerted on the vertebrae. Each vertebra consists of a vertebral body, vertebral arch, and seven processes.
The lumbosacral spine consists of five lumbar (L1–L5) and five sacral vertebrae (S1–S5) and their associated intervertebral discs, nerves, muscles, ligaments, and blood vessels.
0 kommentar(er)
