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Recognizing Nontraumatic Abnormalities of the Spine


Back pain, particularly low back pain, is the leading cause of years lived with a disability worldwide, a measure reflecting the impact an illness has on quality of life. In 2017, studies estimated that at any given moment 577 million people were suffering with low back pain globally, making it the world’s leading cause of limitation of activity and absenteeism from work.

Case Quiz 22 Question

This is a close-up conventional radiograph of the lumbosacral junction in a 28-year-old male with back pain. The cause of his back pain is revealed in the radiograph. What is it? The answer is at the end of this chapter.

  • Magnetic resonance imaging , with its superior soft-tissue differentiation, is the study of choice for most diseases of the spine because of its ability to visualize and detect abnormalities in soft tissues, such as bone marrow, the spinal cord, and the intervertebral disks, along with its ability to display images in any plane and the lack of exposure to radiation.

  • MRI studies remain relatively expensive and their availability is not as widespread as CT or conventional radiographs, patients with pacemakers and certain internal ferromagnetic materials (e.g., certain aneurysm clips) are not able to be scanned , the procedure takes more time to complete, and some patients cannot tolerate the claustrophobia they experience in some of the high-field-strength MRI scanners (see Chapter 20 ).

The Normal Spine ( FIG. 22.1 )

Vertebral Body

  • Almost every vertebra has a body composed of inner cancellous bone and marrow and posterior elements made of compact dense bone consisting of the pedicles, laminae, facets, transverse processes, and a spinous process ( Fig. 22.2A ).

    Fig. 22.1, Normal Spine.

    Fig. 22.2, Normal Spine, Axial CT and Frontal Radiograph.

  • From the level of C3 through the level of L5 the vertebral bodies are more or less rectangular in shape and of about equal height posteriorly as anteriorly.

  • The endplates of contiguous vertebral bodies are roughly parallel to each other.

  • The articular facets of the superior and inferior articular processes are lined with cartilage and these facet joints are true synovial joints.

  • In the frontal projection, each vertebral body displays two ovoid pedicles visible on each side of the vertebral body. The pedicles of L5 are frequently difficult to visualize, even in normal individuals, because of the lordosis of the lumbar spine ( Fig. 22.2B ).

  • On conventional radiographs of the lumbar spine performed in the oblique projection, the anatomic structures normally superimpose to produce a shadow that resembles the front end of a Scottish terrier, the Scottie dog sign ( Fig. 22.3 ).

    Fig. 22.3, Normal Scottie Dog.

Intervertebral Disks

  • The intervertebral disks have a central gelatinous nucleus pulposus surrounded by an outer annulus fibrosus that is, in turn, made up of inner fibrocartilaginous fibers and outer cartilaginous fibers (Sharpey’s fibers) . The nucleus pulposus is located near the posterior aspect of the disk ( Fig. 22.4 ).

    Fig. 22.4, Normal Spine and Soft Tissues.

Spinal Ligaments

  • Several ligaments traverse the spine ( Table 22.1 ) (see Fig. 22.4 ).

    TABLE 22.1
    Ligaments of the Spine
    Ligament Connects
    Anterior longitudinal ligament Anterior surfaces of vertebral bodies
    Posterior longitudinal ligament Posterior surfaces of vertebral bodies
    Ligamentum flavum Laminae of adjacent vertebral bodies; lies in posterior portion of spinal canal
    Interspinous ligament Between spinous processes
    Supraspinous ligament Tips of spinous processes

Spinal Cord and Spinal Nerves

  • The spinal cord extends from the medulla oblongata to the level of L1-L2, ending as the conus medullaris. The cauda equina extends inferiorly from that point as a collection of nerve roots, with each root exiting below its respectively numbered vertebral body.

  • Each of the paired neural foramina of the spine contains a spinal nerve, blood vessels, and fat.

  • Spinal nerves are named and numbered according to the site they exit from the spinal canal. From C1-C7, nerves exit above their respective vertebrae. The C8 nerve exits between the seventh cervical and first thoracic vertebrae. The remaining nerves exit below their respectively numbered vertebrae.

Important Points

  • The relative height of the disk space varies in each part of the spine.

    • In the cervical spine, the disk spaces are about equal to each other in height.

    • In the thoracic spine, they are usually slightly decreased in size from the cervical spine , but equal in height to each other.

    • In the lumbar spine, the disk spaces progressively increase in height with each successive interspace, except for L5-S1, which can be equal to or slightly less than the height of L4-L5 on conventional radiographs.

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