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Article Excerpt
After completing this article, the reader should be able to:
* Identify and label the parts of a vertebra and describe the differences between the vertebrae in each section of the spine.
* Distinguish between and describe the appearance of normal vs abnormal spinal curves.
* Explain the 3 treatment options for scoliosis and describe how a treatment is chosen.
* Discuss the role of medical imaging in the diagnosis and treatment of scoliosis.
* Summarize basic procedural differences for radiographing the spine in patients with scoliosis.
* Identify radiation safety methods necessary for imaging young scoliosis patients.
The spine, or vertebral column, is located centrally and posteriorly in the body. It is an important part of the body and has many functions. The spine is necessary for providing structure, flexibility, support and movement for our bodies. It acts as an attachment site for the muscles of the back, as well as the posterior ribs. (1) The spine also encloses and helps to protect the spinal cord. (1)
According to Merrill's Atlas, the adult spine is composed of 24 true vertebrae that are separated into 3 segments based on body location. The cervical segment in the neck consists of 7 vertebrae. The thoracic segment in the upper back and thorax consists of 12 vertebrae, and the lumbar segment in the lower back consists of 5 vertebrae. The vertebral column is supported and held together by ligaments and joints. (1) Also considered part of the vertebral column are the sacrum and coccyx, which together are referred to as the pelvic section of the spine. (1)
During prenatal development and in early childhood, the vertebral column consists of approximately 33 individual segments that include the pelvic segments of the spine. (2) Figure 1A shows the lateral lumbar spine and lateral sacrum in a toddler. The lateral sacral image, Figure 1B, shows the individual sacral bodies before fusion. When the pelvic segments fuse, they are called false or fixed vertebrae. (1) The fusion of these vertebrae results in the appearance of 2 separate bones: the sacrum and the coccyx.
As medical imaging professionals we know that our vertebral column is not perfectly straight, even though it may appear so in the posterior and anterior views. When seen from the side, 4 slight curves are visible, arching anteriorly and posteriorly from the coronal plane and forming an elongated "S" shape. (1) These curves are normal and help us in our daily activities by keeping us balanced and flexible. The curves also help to absorb stresses placed on our bodies through impact activities such as running and jumping. (2) Normal curves of the spine develop as we grow and learn motor skills. (1,2)
According to the National Scoliosis Foundation, 2% to 3% of the population has an abnormal curve to their spine called scoliosis. (3) A common lay definition of scoliosis is an abnormal side-to-side curvature of the spine. As imaging technologists, we frequently see evidence of scoliosis on lumbar and thoracic spine exams but may know little about this condition beyond its definition.
[FIGURE 1 OMITTED]
This article is meant to enlighten imaging technologists about the curves of the spine, including information on scoliosis and imaging considerations for patients with scoliosis. Although there are several categories of scoliosis that affect people of different ages, this Directed Reading will focus on the most common form, which affects adolescents.
Normal Spinal Anatomy
Anatomy of the Vertebrae
Adult vertebrae vary slightly in size and shape according to their location in the spine. With the exception of the first and second cervical vertebrae, the spinal vertebrae have similar structural components that can be divided into 2 distinct sections: the body and the vertebral arch. (1,2)
The body is the thick, rounded anterior part of the vertebra. It is the weight-bearing part. (2) The superior and inferior surfaces of the vertebral body are referred to as endplates and are the attachment sites for the intervertebral disks. (2)
Intervertebral disks separate the bodies of the vertebrae in the vertebral column. The disks are composed of 2 sections and act as shock absorbers for the body during activities such as running, jumping and other activities that increase the axial load on the spine. The outer section of the disk is composed of fibrocartilaginous material and is termed the annulus fibrosus. (1,2) The inner section of the disk is called the nucleus pulposus and is filled with a semigelatinous material. (1,2) The intervertebral disks are best demonstrated through magnetic resonance (MR) and computed tomography (CT) imaging. The disks are not radiopaque and, therefore, are not visible on radiographs.
The posterior portion of a vertebra, the vertebral arch, is composed of the pedicles and the lamina. (1,2) The pedicles are short columns of bone that protrude posteriorly from the vertebral body. (1) The superior and inferior concave portions of the pedicle (called the superior and inferior vertebral notches) form the intervertebral forainen in the articulated spine) The foramen allows for passage of spinal nerves and blood vessels. (1)
The laminae are flat sections of bone that project from the pedicles in a posterior and medial direction. Together, the pedicles and laminae create the opening between the body of the vertebrae and the vertebral arch. This opening is called the vertebral foramen.
The series of articulated vertebrae and vertebral foramen form the vertebral canal, through which the spinal cord and nerve roots pass. (1,2) The canal houses and protects the spinal cord beginning at the foramen magnum, where the spinal cord exits the skull.
The pedicles and the laminae support 7 processes of bone that have specific functions. (1) Posteriorly and somewhat inferiorly from the center of the laminae projects the spinous process. (1) The spinous process is the most posterior aspect of the vertebrae and is felt as a bony knob or protrusion at the center of the back. Projecting laterally from the pedicles are the transverse processes. The transverse processes act as attachment sites for various muscles and ligaments of the back. (4)
The final 4 processes include the 2 superior and 2 inferior articular processes. Each superior and inferior articular process connects to form a column of bone called the articular pillar. (1) The articular pillars are found behind each transverse process at the junction of the pedicle and lamina. (1) The articulations between vertebrae occur at the inferior articular processes of the superior vertebra with the superior articular processes of the inferior vertebra. Fibrocartilage covers each of the articulating surfaces of the articular processes. These articular surfaces often are called facets. (1,2) The joints formed between the vertebrae at these facets are called zygapophysealjoints or facet joints. (1,2)
[FIGURE 2A OMITTED]
[FIGURE 2B OMITTED]
[FIGURE 3A OMITTED]
Figure 2A demonstrates the superior aspect of a vertebra, and Figure 2B shows the posterior aspect of a lumbar vertebra. Note that when the posterior aspect of the lamina, which is located between the superior and inferior articular processes, appears in the lumbar vertebra it is called the pars interarticularis.
[FIGURE 3B OMITTED]
Basic Sectional Differences
The individual vertebrae get progressively larger the more distally located they are in the spine. The first section of the spine, the cervical section, has the smallest vertebrae. These vertebrae are adapted especially to support the weight and movement of the head. (2,5) The first and second cervical vertebrae, respectively called the atlas and axis, are adapted especially for rotational movements. (5) The atlas (C-l) has no vertebral body and is composed of a ring of bone specially adapted to articulate with the head. (1,2,5,6) The axis (C-2) contains the upward-pointing odontoid process. This adaptation is useful in allowing extreme rotational movements of the head and neck. (1,5,6) It also is important to note that there is no intervertebral disk between the first and second cervical vertebrae due to the unique structure of each. (1,2) Figure 3A shows the atlas (C-1) and Figure 3B shows the axis (C-2).
All 7 cervical vertebrae have transverse foramen. (1,2) These openings are located in the transverse processes and are important passageways for the vertebral artery, nerves and veins. (1,2) Other sectional differences found in the cervical vertebrae include the bifid spinous tips on C-2 through C-6 and the overlapping vertebral bodies of C-3 through C-6. (1,2)
The thoracic vertebrae are larger than the cervical vertebrae but provide much less movement capability. (5,6) The thoracic vertebrae, along with the ribs, are adapted for organ protection and stability and form the posterior portion of the bony thorax. (2,6)
The thoracic vertebrae are unique in that they have facets on all 12 vertebral bodies and on the transverse processes of T-1 through T-10. (2) These facets form the costovertebral and costotransversejoints with the ribs. (1,2,5)
Moving distally from T-1 through T-12, the thoracic vertebral bodies gradually increase in size. (l) The upper thoracic vertebrae more closely resemble the cervical vertebrae, while the distal thoracic vertebrae resemble those of the lumbar spine. (1,2) The middle section of thoracic vertebrae, referred to as typical thoracic vertebrae, have a spinous process that angles sharply downward. (1,2)
The vertebrae of the lumbar spine are the largest and strongest in the body. (2) This is necessary to help support the weight of the body's torso. (2,5,6) The bodies of the lumbar vertebrae also progress in size from L-1 to L-5. (1,2) The lumbar section of the spine has more movement capability than the thoracic section and is more likely to be injured. (1,5,6)
Normal Vertebral Curves
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