Introduction
Background
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% (Boden, 1990). In a more recent study, the incidence of cervical focal disc protrusions in asymptomatic volunteers was 50% and of annular tears at one or more levels was 37% (Ernst, 2005).
Functional Anatomy
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 (White, 1991).
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 (White, 1991).
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. 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 (Mercer, 1999).
Sport Specific Biomechanics
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 (Torg, 1989). 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 (Torg and Corcoran, 1997).
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 (NCAA 1976). 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 (AAP, 1981). 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 (Tator, 1984). Similar guidelines for diving prohibit diving in water that is less shallow than twice one's height (Torg, 1989).
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 (Mochida, 1998).
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. 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 (Nachemson, 1976).
Clinical
History
Athletes with symptomatic cervical disc injuries commonly present with segmental neck pain, muscle spasm, loss of ROM, and referred pain in both radicular and nonradicular distribution. Nerve root involvement leads to radicular upper extremity pain, weakness, and sensory changes. Pain symptoms may be exacerbated with motion, lifting, and Valsalva maneuvers.
Physical
- Information obtained from the physical examination is often of limited benefit.
- Examination generally demonstrates reduced segmental motion at involved levels.
- Pain with mobilization may or may not be present.
- ROM may or may not be present, depending on the chronicity of the condition and its severity.
- Neurologic examination is generally within the reference range. (see Cervical Radiculopathy.)
- Cervical cord neuropraxia (CCN) is a transient neurologic syndrome occurring in athletes with cervical spine injury. CCN is especially common in cervical spine injuries resulting from contact sports. The presentation can range from bilateral paresthesias in the arms to complete quadriplegia. Typical episodes can last from 15 minutes to 48 hours with complete recovery. The mechanism is thought to be due to brief compression of the spinal cord resulting in transient interruption of the spinal pathways. The incidence of cervical spinal stenosis is as high as 86% in athletes who have experienced this condition (Torg and Corcoran, 1997).
Causes
Cervical disc injuries are relatively common in athletes involved in both contact and noncontact sports. Information on cervical injuries has primarily been obtained from evaluation of football players; however, this information can be applied to athletes who play other high-risk sports. Sports associated with cervical injuries include football, rugby, ice hockey, wrestling, gymnastics, cheerleading, baseball (headfirst slides), and swimming (diving into shallow water).
- Injuries are often the result of axial applied forces, with secondary forces of hyperflexion, hyperextension, and rotation adding to the overall injury pattern. Cervical disc disease is most often limited to a single segment and is usually unilateral. In symptomatic athletes, nerve root compression may be the result of an extruded posterolateral disc, combined disc degeneration, osteophytes, and disc fragment extrusion. Preexisting cervical spondylosis or developmental stenosis may lead to central disc herniation resulting in long-tract neurologic findings.
- Age-related morphologic changes
- In regards to the continuum of cervical degenerative disc disease, the age-related morphologic changes also must be considered. The intervertebral disc is a hydrostatic load-bearing structure. The nucleus pulposus is a confined and well-localized fluid that exists within the annulus fibrosis. The nucleus pulposus functions in converting axial loads into tensile strain on the annular fibers and the vertebral endplates.
- During the first 20 years of life, the development of disc protrusion through the cartilaginous endplates is observed. These protrusions are known as Schmorl nodes. Degenerative changes manifest during the third through fifth decades of life, with loss of intervertebral disc height and development of osteophytes, particularly at the origins of the vertebral endplates. The facets, facet joint capsule, and ligamentum flavum hypertrophy potentially compromise the intervertebral foramen and central canal. As the discs become degenerative, the hydrostatic pressure declines.
- Because of intradiscal compressive forces, disc material has a tendency to follow the radial fissure because it is the path of least resistance. Once the radial fissure becomes complete, the disc is predisposed to herniate. Penetration through the outer annular wall defines herniation (extrusion). An extruded disc penetrating through the posterior longitudinal ligament (PLL) represents an extrusion that is noncontained. One that remains confined by the PLL is termed an extrusion contained by the PLL. Primary annular disruption initially may occur in the periphery. This is called a rim lesion. As the process continues to progress and the margins of the annulus and nucleus coalesce with infiltration of type III collagen, the gelatinous nucleus becomes replaced. The disc becomes increasingly fibrotic (Coventry, 1945; Gower, 1969; Lipson, 1981; Pearce, 1987).
- The greatest risk for herniation occurs in the younger age group because the nuclear material in this group can still generate significant turgor, enabling it to produce a focal herniation. A severely degenerative disc lacks nuclear tissue; therefore, it cannot generate the forces needed to create a disruption. Therefore, disc herniation is rare in elderly persons. When disc herniation occurs, it is primarily in the posterolateral aspect of the disc just lateral to the margin of the posterior longitudinal ligament. This is an obvious area of compromised reinforcement (Lipson, 1981).
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Further Reading
Keywords
acute cervical spine injury, annular tear with herniation of the nucleus pulposus, annular tear without herniation of the nucleus pulposus, cervical degenerative disease
