Cervical Disc Injuries 

Acute cervical spine injury has been associated with sports such as football, gymnastics, rugby, ice hockey, and diving. Athletes with cervical disc injury may present with neck pain, radicular pain, quadriparesis, or quadriplegia secondary to myelopathy.

Cervical disc injury includes 2 entities. The more common form involves annular tears with herniation of the nucleus pulposus (ie, soft disc herniation). The second type of disc injury is an annular tear without herniation of the nucleus pulposus (ie, internal disc disruption).

When considering the term cervical disc injury, it is important to recognize the natural history of cervical degenerative disease. It is this process that may insidiously predispose one to cervical disc injury of either an acute or chronic nature. Cervical disc injuries can be treated conservatively or by surgery, depending on the clinical presentation.

Return to play is an important but controversial issue following successful treatment of cervical disc injury. No accepted universal guidelines regarding return to play exist.

This article intends to outline the etiopathology, evaluation, and treatment of cervical disc disease. Available guidelines for return to play following cervical disc injury are also presented.

Frequency

United States

In a study of asymptomatic individuals younger than 40 years, the incidence of cervical disc herniation was 10%, the incidence of disc degeneration was 25%, and the incidence of foraminal stenosis was 4%.^[1] In another study, the incidence of cervical focal disc protrusions in asymptomatic volunteers was 50% and of annular tears at one or more levels was 37%.^[2]

Seven cervical vertebrae articulate with one another anteriorly via the interbody joint with an intervening intervertebral disc and 2 uncovertebral joints. Laterally, they articulate via the paired posterolaterally placed zygapophyseal (facet) joints.

Each cervical vertebra forms a ring with the vertebral body anteriorly, the pedicles laterally, and the laminae posteriorly. The ring is known as the spinal or neural canal. As the vertebrae stack upon one another, the connection of the spinal foramina is known as the spinal canal. Through the spinal canal runs the spinal cord, nerve roots, vessels, and meninges (membranous covering of the spinal cord and nerve roots).

The cervical spinal nerves take origin from the spinal cord as the anterior and posterior rootlets. The posterior rootlet has a segmental brain that lies on its most lateral extent at the inner portion of the intervertebral foramen. The posterior and anterior rootlets join to form a spinal nerve, which is only approximately 2 cm long and lies within the intervertebral foramen. The spinal nerve divides into a posterior and anterior ramus at the outlet of the intervertebral foramen. The spinal nerves exit the intervertebral foramen above the numbered cervical vertebrae, and the thoracic and lumbar nerves exit the intervertebral below the numbered vertebra. Consequently, the eighth cervical nerve exits between the C7 and T1 segment

The symptoms related to pathology at each of the intervertebral disc segments have been well described and are not elaborated on in this article. Note that during dynamic range of motion (ROM), the intervertebral foramen, which houses the exiting cervical nerves, becomes very dynamic. In flexion, the intervertebral foramen enlarges in patency, and it decreases with extension. In rotation, the ipsilateral side becomes smaller, and the contralateral side becomes larger. The extreme changes of the foramina are magnified when motions are coupled with flexion and extension.

Distinctiveness of the cervical disc

The predominance of literature has addressed the lumbar spine; much of the lumbar spine literature has been extrapolated and applied to the cervical spine. Bogduk, using microdissection, systematically evaluated 59 human cadaveric intervertebral discs.^[3] The orientation, location, and attachments of each strip bundle of collagen were recorded photographically and in sketches. He concluded that the cervical annular fibrosus did not consist of concentric laminae of collagen fibers, as noted in lumbar discs. Rather, the annulus forms a crescentic mass. The primary thickness is anterior and tapers laterally toward the uncinate processes. Posterolaterally, it is essentially deficient; posteriorly, it is represented by a thin layer of paramedian vertically oriented fibers. The anterior crescentic mass is likened to an interosseus ligament more so than a ring of concentric fibers surrounding the nucleus pulposus.^[4]

Cervical spine injury is commonly associated with axial loading with the neck in flexion. In flexion of the neck to 30°, the normal lordosis of the cervical spine is obliterated and axial loading of the head is dissipated through a straight spine.^[5] Examples of axial loading in players include a football player striking his opponent with the crown of his helmet, an ice hockey player striking his head on the board while doing a push or check, a diver striking the ground with his head after diving in shallow water, and a gymnast accidentally landing head down while performing a somersault on a trampoline.

The effects of axial loading of the cervical spine include fracture of vertebrae, cervical disc herniations, ligament rupture, facet fracture, and dislocations. The neurologic deficits are greater in athletes with congenital spinal stenosis.^[6]

New guidelines in athletic sports have decreased the incidence of spinal cord injury. For example, permanent cervical quadriplegia has decreased significantly in high school and college level football, secondary to changes in the rules involving tackling. The Guidelines of NCCA Football rules committee banned spear tackling in football.^[7] In 1977, The American Academy of Pediatrics published a statement banning the use of trampolines in schools because of the high incidence of quadriplegia associated with this apparatus.^[8] The Canadian Committee on the prevention of spinal injury due to hockey recommends rules against boarding and crosschecking and on education to avoid spearing and impact with boards.^[9] Similar guidelines for diving prohibit diving in water that is less shallow than twice one's height.^[5]

Disc herniation resorption

Absorption of a cervical herniated disc has been appreciated. Mochida followed the regression of cervical disc herniation by using MRI. He noted that acutely, active resorption of herniated material occurred. The MRI findings did suggest that part of the resorbed material may have consisted of hemorrhagic substance. Mochida noted that extruded material exposed to the epidural space was resorbed more quickly than subligamentous herniation probably because of increased exposure to the immune system.^[10]

Resorption of herniated disc material should not be confused with repair. Injured or degenerative disc material does not repair itself to a significant extent. In review of intervertebral segment physiology and metabolic turnover, Nachemson drew some remarkable conclusions.^[11] He cited that diffusion of solutes can take place through the central portion of the endplates, as well as through the annulus fibrosus. There are also vascular contacts between the marrow spaces, the vertebral body, and the hyaline cartilaginous endplates. These vascular contacts are significantly less in discs that show advanced degenerative changes. He also cited that the area between the nucleus and annulus posteriorly is proportionally less than the area of the anterior margins, lending itself to possible nutrient deficiency and hastened fibrotic infiltration.

The surface area for diffusion is smaller posteriorly. Combining the relative diffusion limitations posteriorly and the mechanics of posterolateral disc herniation, it becomes rather apparent why a possible pattern of failure exists in this region.^[11]