The Stabilizers of the Cervical Spine
This is the eighth in a series of articles that address how muscles work synergistically to create efficient movement at each joint. The previous article examined the muscles that support the thoracic spine; this discussion covers the posterior muscles of the cervical spine. The cervical spine’s muscle functions are more intricate and delicate than those of other spinal muscles. To decrease the potential for injury, be extremely conservative when using the joint range of motion (ROM) exam and suggested exercises. Under no circumstances should the movements or exercises be applied to any client with current injury or pain.
To understand the function of the muscles that stabilize the cervical spine and occiput, we must first look at the muscles’ anatomy and study their function in cervical and capital motion. As with the muscles that extend the lumbar and thoracic spine, there is significant overlay between the muscles that extend the cervical spine and occiput. Such overlay makes it important to recognize the functional similarities between these muscles when you evaluate ROM or recommend exercises.
Although integrated, the associated muscles have different functions relative to their insertions on the cervical spine or occiput. In general, the cervicis muscles regulate cervical extension; the capitis muscles regulate occipital extension.
1. The Splenius Capitis
This muscle runs superficially to the semispinalis capitis. With the splenius cervicis, it has an excellent lever arm for both cervical and capital extension. In addition, the splenius capitis both rotates and laterally bends the head to the same side when working unilaterally.
2. The Splenius Cervicis
This muscle runs superficially to the semispinalis cervicis. With the splenius capitis, it has an excellent lever arm for cervical spinal extension. The splenius cervicis also rotates and laterally bends the cervical spine to the same side when working unilaterally.
3. The Semispinalis Capitis
This large muscle runs up the cervical spine and deep to the splenius capitis. With the semispinalis cervicis, it has a major role in extending the cervical spine and maintaining cervical lordosis. Working bilaterally and with the cervical spine stabilized, it has a great mechanical advantage for capital extension: The muscle’s attachments are placed well behind the axis, creating a long lever arm for extension. Working unilaterally, the semispinalis capitis rotates the head to the opposite side while laterally bending to the same side.
4. The Semispinalis Cervicis
This large muscle runs up the cervical spine and deep to the splenius cervicis. With the semispinalis capitis, it also helps extend the cervical spine and maintain cervical lordosis. Through its attachment on the axis, the semispinalis cervicis stabilizes the axis, which provides an anchoring mechanism so the suboccipitals can function properly. The positioning of the attachments places the muscle well behind the axis and creates a long lever arm for extension. Working unilaterally, the semispinalis cervicis creates rotation of the cervical spine to the opposite side while laterally bending to the same side.
5. The Longissimus Capitis
This muscle runs deep to the splenius capitis and laterally to the semispinalis capitis and functions in extension of the cervical spine and occiput. It has a greater lever arm when functioning unilaterally to bend laterally and rotate the head to the same side.
6. The Longissimus Cervicis
This muscle runs deep to the splenius cervicis and laterally to the semispinalis cervicis and functions in extension of the cervical spine. Like the longissimus capitis, it has a greater lever arm when functioning unilaterally to bend laterally and rotate the cervical spine to the same side.
7. The Multifidus Cervicis
These deep muscles of the erector spinae run obliquely from the upper thoracic and lower cervical transverse processes and two to four levels up the spinous processes to C2. The multifidus cervicis stabilizes the cervical spine and regulates the anterior shear of each segment.
8. The Iliocostalis Cervicis
These deep muscles run laterally, originating from ribs 3 through 6 and running up and into the transverse processes of C4 through C6. Lateral to medial fiber alignment positions the iliocostalis cervicis to assist in cervical rotation to the same side.
9. The Spinalis Cervicis
These deep muscles of the erector spinae run vertically up the spinous processes from the upper thoracic vertebrae to C2. This muscle group has a poor mechanical position for movement and is noted more for segmental stability and proprioceptive feedback.