AUTHOR AND EDITOR INFORMATION

Section 1 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

INTRODUCTION

Section 2 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

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

Section 3 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

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).

DIFFERENTIALS

Section 4 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

WORKUP

Section 5 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

Imaging Studies

• Plain radiography
• • Plain radiography is a useful screening tool to demonstrate associated osseous injury. Although disc space reduction is seen in chronic disc degeneration, plain films may not necessarily demonstrate reduced disc space secondary to acute disc injury.
  
  
  
  • Plain films have a role for assessment of cervical spinal stenosis, as this is associated with a higher incidence of cervical cord injury. The Torg ratio is used to assess cervical spinal stenosis. The Torg ratio is the sagittal canal/vertebral body ratios measured on cervical spine lateral radiographs. The normal value is 1.0. A ratio of 0.8 and below has been considered indicative of cervical spinal stenosis (Torg and Corcoran, 1997).
  
  
  
  • Plain radiography helps diagnose spear tackler spine, which is an entity seen in a subset of football players. Permanent neurologic injury is higher in this population due to axial loading of a relatively straight spine (Torg, 1993). Spear tackler spine is characterized by the following:
    
    
    • Developmental narrowing (stenosis) of the cervical canal
    
    
    
    • Persistent straightening or reversal of the normal cervical lordotic curve on erect lateral radiographs obtained in the neutral position
    
    
    
    • Concomitant preexisting posttraumatic radiographic abnormalities of the cervical spine
    
    
    
    • Documentation of having employed spear tackling techniques
       
• MRI
• • MRI may demonstrate decreased disc height and reduced signal intensity as well as spondylotic spurs. MRI is more important to evaluate spinal cord or nerve root compression secondary to the disc herniation.
  
  
  
  • Interpretation of MRIs is important, as many abnormal MRI findings are noted in individuals who are asymptomatic.

Other Tests

• Electrodiagnostic studies may be necessary to correlate clinical and radiological findings.


• Discography is indicated in intractable axial neck pain not responding to conservative measures. Discography is a provocative procedure and is performed by injecting the lower cervical discs with normal saline to reproduce the patient's pain complex.

TREATMENT

Section 6 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

Acute Phase

Rehabilitation Program

Physical Therapy

Physical therapy emphasizes segmental mobilization, postural training, and reconditioning.

Surgical Intervention

Surgery is indicated in acute cervical disc herniation causing central cord syndrome and in cervical disc herniations refractory to conservative measures. Studies have shown that an anterior discectomy with fusion is the recommended procedure for central or anterolateral soft disc herniation, while a posterior laminotomy-foraminotomy may be considered when technical limitations for anterior access exist (eg, short thick neck) or when the patient has had prior surgery at the same level (Herkowitz, 1990).

Other Treatment

Translaminar cervical epidural injections can decrease the inflammation secondary to acute disc herniation and help the patient to tolerate physical therapy.

Recovery Phase

Rehabilitation Program

Physical Therapy

This phase of rehabilitation focuses on soft tissue overload and biomechanical dysfunction. Goals of this phase are to eliminate pain, normalize spinal mechanics, and improve neuromuscular control of the injured cervical spine. Restoration of the resting muscle length and full, pain-free, cervical ROM are necessary. Strengthening exercises start in simple planes and progress to complex muscle patterns.

Surgical Intervention

Surgical treatment for cervical disc herniation is needed in only a very small percentage of athletes. This includes those with any evidence of a cervical myelopathy or progressive neurologic deficits and those in whom conservative treatment has failed for a period of 3 months. Radiographically confirmed evidence of cervical disc disease should be available before performing this surgery. The common surgical procedures for cervical disc injuries include (1) anterior decompression and fusion (ADCF), (2) laminectomy, laminotomy-facetectomy, and (3) laminoplasty.

Anterior decompression and fusion

A herniated disc in the neck is commonly approached anteriorly. Both lateral and central discs can be removed through this approach. Other indications include progressive neurologic deficit and unremitting pain.

The results from cervical discectomy have shown an approximately 95% chance of good-to-excellent relief from the radiating arm pain (Gore, 1984). Numbness in the upper extremity generally improves. Weakness in the affected arm may require some physical therapy to maximize recovery. Three to 6 months following surgery, the patient may resume full, unrestricted activities.

Complications from this surgery are very rare. The most common complications following anterior decompression and fusion are transient sore throat, hoarseness, and difficulty swallowing. Other complications include failure of bony fusion, which occurs in 5-8% of patients. Pseudarthrosis is commonly related to the number of levels fused. When it occurs, half of the patients have no symptoms from it and nothing further is required. No correlation exists between radiologic appearance of pseudarthrosis alone and the clinical outcome. Careful considerations must be made before reoperating. For the 50% of patients who do develop neck pain as a result of the failure of fusion, additional surgery may be required to obtain a solid fusion of the disc and to alleviate the neck pain.

Permanent spinal cord injury is the most dreaded complication and occurs at a rate of 1 in 1000 (Flynn, 1982). The infection rate is less than 1 in 100. Other rare complications include recurrent injury to the laryngeal nerve, laceration of vertebral and carotid vessels, and injury to the trachea or esophagus.

Laminectomy

A cervical laminectomy is a procedure designed to resect the lamina on one or both sides to increase the axial space available for the spinal cord. The procedure is typically indicated for spinal stenosis. The indication in the context of cervical disc disease is when more than 3 levels of disc degeneration with anterior spinal cord compression are present. Single-level cervical disc herniation is ideally managed from the anterior approach. The complications of the posterior approach include instability leading to kyphosis, recalcitrant myofascial pain, and occipital headaches.

Postlaminectomy kyphosis requires revision surgery. If preexistent kyphosis is present, an anterior approach is favorable because in a patient with kyphosis, laminectomy may accelerate kyphosis. As an alternative to laminectomy, a foraminotomy can be used to remove a single-level unilateral lateral disc herniation. This involves removal of 50% of the facet joint on one side. This procedure is effective when radicular arm pain is greater than axial neck pain. Foraminotomy can also be performed anteriorly and has a success rate of 91% in relieving radicular pain (Johnson, 2000).

Laminaplasty

Kyphotic deformity is a well-known complication of laminectomy. This prompted a group of Japanese surgeons to preserve the posterior wall of the spinal canal while decompressing the spinal canal using a Z-plasty technique for the lamina. The variant of the procedure uses a hinge door for the lamina. Laminaplasty is commonly indicated for multilevel spondylotic myelopathy. Comparative studies with laminectomy have shown that patients with laminaplasty have superior functional recovery in spondylotic myelopathy (Miyazaski, 1994). The incidence of spinal cord injury with laminaplasty is approximately 10 times lower than that of laminectomy. Nerve root injury is commonly seen in about 11% of the surgeries. This complication is unique to laminaplasty, and the suggested etiology is traction on the nerve root with posterior migration of the spinal cord.

Recent advances in surgical intervention

Spinal fusion at the cervical disc produces a painless, stable spinal segment at the cost of mobility. In the field of cervical disc prostheses, research is focusing on how to maintain both stability and mobility at the spinal segment. However, only a few studies have been performed and the results have been variable. A study by Pointillart showed that a cervical disc prosthesis failed to achieve the intended mobility in 8 of 10 patients and that pain developed in the other 2 patients in whom mobility persisted (Pointillart, 2001). However, a larger more recent study with 60 patients showed clinical success rates at 6 months and 1 year after implantation of 86% and 90%, respectively (Goffi, 2003).

Other recent surgical interventions include microsurgical posterior herniotomy with en bloc laminoplasty and a minimally invasive anterior contralateral approach for the treatment of cervical disc herniation (Aydin, 2005).

Maintenance Phase

Rehabilitation Program

Physical Therapy

The final phase of rehabilitation requires functional, nonpainful, cervical ROM and proper spinal and shoulder girdle mechanics. Sport appropriate flexibility, strength, and skills are necessary prior to return to play. Sport-specific activities should be reviewed to ensure correct techniques, especially in contact and collision sports.

MEDICATION

Section 7 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

Oral nonsteroidal anti-inflammatory drugs (NSAIDs) can help decrease pain and inflammation. Various oral NSAIDs can be used, and none of these holds a clear distinction as the drug of choice. The choice of NSAIDs is largely a matter of convenience (how frequently doses must be taken to achieve adequate analgesic and anti-inflammatory effects) and cost.

Drug Category: Nonsteroidal anti-inflammatory drugs

Have analgesic, anti-inflammatory, and antipyretic activities. Their mechanism of action is not known, but they may inhibit cyclo-oxygenase activity and prostaglandin synthesis. Other mechanisms may exist as well, such as inhibition of leukotriene synthesis, lysosomal enzyme release, lipoxygenase activity, neutrophil aggregation, and various cell membrane functions.

FOLLOW-UP

Section 8 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

Return to Play

Guidelines for return to play following cervical spine injuries have been published by several authors with little consensus.

Torg et al have published guidelines for return to play following cervical spine injuries (Torg and Ramsey-Emrhein, 1997). The following is described in the context of cervical disc injury.

• No contraindications (Experience and data indicate no increase in risk of serious injury.)
  
  
  • Spina bifida occulta
  
  
  
  • Type II Klippel-Feil anomaly with no evidence of spinal instability
  
  
  
  • Developmental stenosis of spinal canal (canal-vertebral body ratio <0.8)
  
  
  
  • Healed intervertebral disc bulge
  
  
  
  • Asymptomatic cervical disc herniations treated conservatively in the past
  
  
  
  • Stable, one-level anterior or posterior fusion at C-3 or below (only if the individual is neurologically normal, is free of pain, and has a normal range of cervical motion)
     
• Absolute contraindication (Experience and data clearly indicate an increase in risk of serious injury.)
  
  
  • Odontoid agenesis, hypoplasia, or os odontoideum; atlanto-occipital fusion
  
  
  
  • Type 1 Klippel-Feil mass fusion
  
  
  
  • Developmental canal stenosis with ligamentous instability, cervical cord neuropraxia with signs or symptoms lasting longer than 36 hours, or multiple episodes of cervical cord neuropraxia.
  
  
  
  • Atlantoaxial instability or atlantoaxial rotatory fixation
  
  
  
  • Spear tackler's spine
  
  
  
  • Ligamentous laxity (>3.5 mm anteroposterior displacement or 11° rotation)
  
  
  
  • Intervertebral disc herniation with neurologic signs or symptoms, pain, or limitation of cervical ROM
  
  
  
  • Anterior or posterior fusion of more than 3 levels
     
• Relative contraindication (No clear evidence of an increase in the risk of serious injury exists, but sequelae may include recurrent injury or temporary noncatastrophic injury. The player, coach, and parents must understand that there is some risk and agree to assume it.)
  
  
  • Developmental canal stenosis with one episode of cervical cord neuropraxia, presence of intervertebral disc disease, or evidence of cord compression
  
  
  
  • Ligamentous sprain with mild laxity (<3.5 mm anteroposterior displacement and 11° rotation)
  
  
  
  • Healed intervertebral disc herniation
  
  
  
  • Stable, 2-anterior or posterior fusion (if the individual is neurologically normal, asymptomatic, and has full painless cervical motion)
     
• The presence of congenital spinal stenosis should be a taken into consideration for participation in contact sports after an athlete experiences an attack of transient cervical neuropraxia. Cantu and colleagues support the view that athletes with cervical spinal stenosis should not participate in contact sports because of an inherent risk of cervical cord injury (Cantu, 1993). Cantu and Torg both agree that athletes who experience multiple episodes of cervical cord neuropraxia should not be allowed to return to their respective sports (Torg and Ramsey-Emrhein, 1997)

Prevention

Injury prevention is accomplished best through good coaching, adequate preparticipation training, and implementation of proper techniques of sport-specific activity and appropriate safety measures. Studies imply that protective gear may not aid in injury prevention. Instruction and regulations that help educate players about how to avoid an axial loaded straight to the spine may have the greatest impact on cervical injury prevention. A recent review emphasizes these points by recommending that athletes avoid spear tackling, diving in unknown or shallow water, diving while intoxicated, checking from behind in hockey, or using a trampoline without spotting equipment (Morganti, 2003).

Prognosis

Prognosis is generally excellent for the individual with degenerative disc changes. This condition is usually asymptomatic, unless the individual has received trauma to a degenerative segment. As long as the individual maintains a good neck hygiene program emphasizing mechanical balance and conditioning, he or she generally returns to an asymptomatic state.

Education

For excellent patient education resources, visit eMedicine's Back, Ribs, Neck, and Head Center. Also, see eMedicine's patient education articles Shoulder and Neck Pain and Neck Strain.

REFERENCES

Section 9 of 9

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

• American Academy of Pediatrics. Trampoline. Pediatrics. 1981;67:438.
• Aydin Y, Kaya RA, Can SM, Türkmenoglu O, Cavusoglu H, Ziyal IM. Minimally invasive anterior contralateral approach for the treatment of cervicaldisc herniation. Surg Neurol. Mar 2005;63(3):210-8; discussion 218-9. [Medline].
• Boden SD, McCowin PR, Davis DO, Dina TS, Mark AS, Wiesel S. Abnormal magnetic-resonance scans of the cervical spine in asymptomatic subjects. A prospective investigation. J Bone Joint Surg Am. Sep 1990;72(8):1178-84. [Medline].
• Bogduk N, Tynan W, Wilson AS. The nerve supply to the human lumbar intervertebral discs. J Anat. Jan 1981;132(Pt 1):39-56. [Medline].
• Cantu RC. Functional cervical spinal stenosis: a contraindication to participation in contact sports. Med Sci Sports Exerc. Mar 1993;25(3):316-7. [Medline].
• Cantu RC, Bailes JE, Wilberger JE Jr. Guidelines for return to contact or collision sport after a cervical spine injury. Clin Sports Med. Jan 1998;17(1):137-46. [Medline].
• Coventry MB, Ghormley RK, Kernahan JW. The intervertebral disc: Its microscopic anatomy and pathology. Part III: Pathologic changes in the intervertebral disc. J Bone and Joint Surg. 1945;27:460-474.
• Duggal N, Pickett GE, Mitsis DK, Keller JL. Early clinical and biomechanical results following cervical arthroplasty. Neurosurg Focus. Sep 15 2004;17(3):E9. [Medline].
• Ernst CW, Stadnik TW, Peeters E, Breucq C, Osteaux MJ. Prevalence of annular tears and disc herniations on MR images of the cervicalspine in symptom free volunteers. Eur J Radiol. Sep 2005;55(3):409-14. [Medline].
• Flynn TB. Neurologic complications of anterior cervical interbody fusion. Spine. Nov-Dec 1982;7(6):536-9. [Medline].
• Goffin J, Casey A, Kehr P, Liebig K, Lind B, Logroscino C. Preliminary clinical experience with the Bryan Cervical Disc Prosthesis. Neurosurgery. Sep 2002;51(3):840-5; discussion 845-7. [Medline].
• Gore DR, Sepic SB. Anterior cervical fusion for degenerated or protruded discs. A review of one hundred forty-six patients. Spine. Oct 1984;9(7):667-71. [Medline].
• Gower WE, Pedrini V. Age-related variations in proteinpolysaccharides from human nucleus pulposus, annulus fibrosus, and costal cartilage. J Bone Joint Surg Am. Sep 1969;51(6):1154-62. [Medline].
• Johnson JP, Filler AG, McBride DQ, Batzdorf U. Anterior cervical foraminotomy for unilateral radicular disease. Spine. Apr 15 2000;25(8):905-9. [Medline].
• Lipson SJ, Muir H. Experimental intervertebral disc degeneration: morphologic and proteoglycan changes over time. Arthritis Rheum. Jan 1981;24(1):12-21. [Medline].
• Mercer S, Bogduk N. The ligaments and annulus fibrosus of human adult cervical intervertebral discs. Spine. Apr 1 1999;24(7):619-26; discussion 627-8. [Medline].
• Miyazaski K, Hirohuji E, Ono S, et al. Extensive simultaneous multisegment laminectomy and posterior decompression with posterolateral fusion. Jpn Spine Res Soc. 5:167.
• Mochida K, Komori H, Okawa A, Muneta T, Haro H, Shinomiya K. Regression of cervical disc herniation observed on magnetic resonance images. Spine. May 1 1998;23(9):990-5; discussion 996-7. [Medline].
• Morganti C. Recommendations for return to sports following cervical spine injuries. Sports Med. 2003;33(8):563-73. [Medline].
• Nachemson, Alf L. The lumbar spine: An orthopedic challenge. Spine. 1976;1(1).
• National Collegiate Athletic Association. Article 2-1,2-N 1976; Rule 2, Section 24; Rule 9, Section 1. In: Football rule changes and modifications. 1976.
• North American Spine Society. Orthopaedic Knowledge Update: Spine. American Academy of Orthopaedic Surgeons; 1997:75, 97-101.
• Pearce RH, Grimmer BJ, Adams ME. Degeneration and the chemical composition of the human lumbar intervertebral disc. J Orthop Res. 1987;5(2):198-205. [Medline].
• Pointillart V. Cervical disc prosthesis in humans: first failure. Spine. Mar 1 2001;26(5):E90-2. [Medline].
• Sasai K, Saito T, Ohnari H, Yamamoto T, Kasuya T, Wakabayashi E, et al. Microsurgical posterior herniotomy with en bloc laminoplasty: alternative methodfor treating cervical disc herniation. J Spinal Disord Tech. Apr 2005;18(2):171-7. [Medline].
• Tator CH, Edmonds VE. National survey of spinal injuries in hockey players. Can Med Assoc J. Apr 1 1984;130(7):875-80. [Medline].
• Torg J. Epidemiology, pathomechanics, and prevention of athletic injuries to the cervical spine. In: The Cervical Spine. 1989:442-463.
• Torg JS, Corcoran TA, Thibault LE, Pavlov H, Sennett BJ, Naranja RJ Jr, et al. Cervical cord neurapraxia: classification, pathomechanics, morbidity, and management guidelines. J Neurosurg. Dec 1997;87(6):843-50. [Medline].
• Torg JS, Ramsey-Emrhein JA. Suggested management guidelines for participation in collision activities with congenital, developmental, or post-injury lesions involving the cervical spine. Med Sci Sports Exerc. 1997;29:256-272.
• Torg JS, Sennett B, Pavlov H, Leventhal MR, Glasgow SG. Spear tackler's spine. An entity precluding participation in tackle football and collision activities that expose the cervical spine to axial energy inputs. Am J Sports Med. Sep-Oct 1993;21(5):640-9. [Medline].

Article Last Updated: Apr 6, 2006