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Back and Spinal Cord
Thoracic Spine
Clinical Note
Excessive kyphosis is an abnormal increase in the thoracic curvature. This occurs frequently in osteoporotic women who develop anterior wedging–type compression fractures of thoracic vertebrae.
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The thoracic region of the vertebral column is the least mobile of the presacral vertebral column because of thin intervertebral discs, overlapping spinous processes, and the presence of ribs. This minimizes the potential for disruption of respiratory processes and maximizes stability of the thoracic spine.
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The normal thoracic curvature (kyphosis) is due almost entirely to the bony configuration of the vertebrae, whereas in the cervical and lumbar regions thicker discs also contribute to the respective curvatures in these regions.
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The overlapping of angled osseous structures of the thoracic spine's posterior elements and costovertebral junctions may result in confusion pertaining to bone changes caused by trauma or tumors on radiographs or cross-sectional images. Volume rendered displays can, in such cases, provide anatomic clarity not easily perceived on other image displays.
Lumbar Vertebrae
Clinical Note
Lumbar spinal stenosis may be congenital or acquired. Symptoms include pain, numbness, or weakness in the lower back or lower limbs; the symptoms may be temporally variable and are often worse after prolonged standing or walking.
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Spondylolisthesis refers to the anterior displacement of a vertebra in relation to the inferior vertebra; it is most commonly found at L5/S1because of a defect or non-united fracture at the pars interarticularis (the segment of the vertebral arch between the superior and inferior facets).
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There are typically five lumbar vertebrae, but the fifth lumbar may become fused with the sacrum (sacralization of L5) or the first sacral vertebrae may not be fused with the remaining sacral vertebrae (lumbarization of S1).
Structure of Lumbar Vertebrae
Clinical Note
Degenerative disc disease is associated with dehydration of the nucleus pulposus, which typically occurs with aging.
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Contrast material that had been injected into the nucleus pulposus has extravasated through a tear in the anulus fibrosus in this CT scan.
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Note that the main (axial) section shows the spinous process, lamina, and inferior facets of the vertebra above and the superior facets of the segment below.
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The vertebral arch is composed of the two (right and left) pedicles and lamina.
Lumbar Spine
Clinical Note
Vertebral bodies are most frequently fractured by excessive flexion (compression) forces, whereas the vertebral arches tend to fracture when the vertebral column is excessively extended.
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The parasagittal CT image is at the level of the blue lines in the coronal and axial views. The axial section is at the level indicated by the red line . The coronal reconstruction is at the level of the green line .
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It is clinically important that the lumbar intervertebral foramina (also called neuroforamina or nerve root canals) extend superior to the associated disc. Herniated L4/5 disc fragments that extend upward and laterally may impinge on the exiting L4 root within the L4/5 intervertebral foramen, whereas herniation of an L4/5 disc fragment posteriorly and inferiorly may impinge on the L5 nerve root.
Sacrum
Clinical Note
A caudal epidural block, often used during parturition, is administered by inserting an indwelling catheter into the sacral hiatus to release an anesthetic agent that eliminates sensation primarily from the S2-S4 spinal nerves. These nerves carry sensations from the uterine cervix, vagina, and perineum.
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The division of spinal nerves into dorsal and ventral rami occurs within the sacral canal so that the primary rami exit the sacrum via the anterior and posterior sacral foramina.
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The auricular surface of the sacrum is for articulation with the ilium forming the complicated sacroiliac joint (SIJ). Arthritis in this joint may be a source of lumbago.
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In osteoporotic patients, the sacrum is less able to resist the shearing force associated with the transfer of upper body weight to the pelvis; this may result in a vertical “insufficiency” fracture.
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