The Spine in Sports Injuries: The Cervical Spine

The Spine in Sports Injuries: Cervical Spine Paul M. Parizel, Jan l. Gielen, and Filip M. Vanhoenacker

CONTENTS

Box 22.1. Plain radiographs

22.1

Introduction 377

● Remain useful in mild cervical spine trauma

22.2

Anatomical Considerations 378

22.3

Biomechanics of the Cervical Spine

22.4

Radiological Examination 383

22.5

Cervical Disc Herniation 384

22.6

Impingement Syndromes and Spinal Stenosis 384

22.7

Burners and Stingers

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Catastrophic Athletic Cervical Spine Injuries 386

Box 22.2. CT

22.9

Nerve Root and Plexus Avulsion

● Preferred technique in more severe trauma (fracture-dislocation)

22.10 Differential Diagnosis

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● Underestimate fractures, especially near the cervico-thoracic junction ● Flexion-extension views are useful to show instability

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Things to Remember 388 References 388

● Very fast (MDCT requires only seconds to scan the cervical spine) ● Provides limited soft tissue contrast

22.1 Introduction Injuries to the spine are commonly associated with all kinds of sports activities, both contact and noncontact sports, and at all levels of competition ranging from the high school level to the professional level (Tall and DeVault 1993). The spectrum of potential spinal injuries is wide; some resolve on their own, others might require conservative therapy, and still others might require surgical intervention. Sports injuries involving the cervical spine include intervertebral disc lesions, acute cervical sprain/strain, P. M. Parizel, MD, PhD, Professor of Radiology J. L. Gielen, MD, PhD, Associate Professor F. M. Vanhoenacker, MD, PhD Department of Radiology, University Hospital Antwerpen, Wilrijkstraat 10, 2650 Edegem, Belgium

Box 22.3. Myelography and CT myelography ● Have been largely supplanted by non-invasive cross-sectional imaging techniques ● Remain useful in the diagnosis of nerve root and brachial plexus avulsion

Box 22.4. MR ● Method of choice for assessing spinal cord, ligaments, muscles and soft tissues ● Fat-suppressed sequences are sensitive to bone marrow edema

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nerve root and brachial plexus injuries, transient (or in rare cases permanent) quadriplegia, unstable injuries with and without fracture dislocation. In the media covering sports events, tragic cervical spine injuries of well-known professional athletes are often brought to national attention. These catastrophic cervical spine injuries most commonly occur in collision sports or motorized sports and can lead to devastating consequences for the athlete (Banerjee et al. 2004). Fortunately, these serious injuries are rare in sports. An elaborate review of epidemiologic studies, involving all types of sports activities at all levels of competition, reveals that the overwhelming majority of sports injuries related to the spine are soft-tissue injuries (sprains and strains) and are self-limiting (Tall and DeVault 1993). It is relatively rare for athletic injuries to the spine to result in significant neurologic compromise. However, in cases with neurologic symptoms, the cervical spine is most commonly involved. Accurate and timely radiological examination of the cervical spine in athletes is therefore essential to establish a correct diagnosis and to prevent further injury.

22.2 Anatomical Considerations Before proceeding with the radiological examination of the spine, we shall present a brief reminder of cervical spine anatomy. The cervical spine consists of seven vertebrae, numbered from C1 to C7. Cervical vertebrae are the smallest of the true vertebrae, and can be readily distinguished from those of the thoracic or lumbar regions by the presence of a foramen in each transverse process. They are ring-shaped with the vertebral body anteriorly, the pedicles laterally, and the laminae and spinous process posteriorly. The first cervical vertebra, C1 or also known as the atlas because it supports the globe of the head, does not possess a vertebral body, but has two lateral masses, which articulate with the occipital condyles. The second cervical vertebra, C2 or also known as the axis because it forms the pivot on which the first vertebra rotates, has a vertical toothlike projection called the dens or odontoid process, on which the atlas (C1) pivots. Embryologically, the odontoid process can be thought of as representing the vertebral body of C1, and articulates with the anterior arch of C1. With the

notable exception of C1–C2, the cervical vertebrae articulate with one another anteriorly via the intervertebral disc and two uncovertebral joints. Laterally, they articulate via the facet joints (also known as zygoapophyseal joints). The successive openings in the articulated ringshaped vertebrae, which are stacked upon one another, enclose the spinal canal (also known as vertebral or neural canal). On cross section, the spinal canal presents an isosceles triangular shape, with the base of the triangle anteriorly (formed by the posterior wall of the vertebral bodies and intervertebral discs), and the sides posterior and lateral (formed by the lamina on either side). The angle between the laminae (interlaminar angle) determines to a large extent the anteroposterior diameter of the spinal canal. The spinal canal contains the spinal cord, nerve roots, blood vessels, and meninges. At each intervertebral disc level, cervical spinal nerves originate from the spinal cord as the anterior (motor) and posterior (sensory) rootlets. Posterior and anterior rootlets join to form a spinal nerve, which lies within the intervertebral foramen. The posterior rootlet has a nerve root ganglion at the inner portion of the intervertebral foramen. The spinal nerve divides into a posterior and anterior ramus at the outlet of the intervertebral foramen. In the cervical spine, the spinal nerves exit the intervertebral foramen above the same-numbered cervical vertebra (e.g. the seventh spinal nerve exits at the C6–C7 level). Though there are only seven cervical vertebrae, there are eight spinal nerves on either side. The eighth cervical nerve exits between the C7 and T1 segment. The cervical intervertebral disc constitutes a separate anatomic and functional entity, and is distinctly different from the lumbar intervertebral disc (Mercer and Bogduk 1999). The anulus fibrosus of the cervical intervertebral disc does not consist of concentric laminae of collagen fibers, as in the lumbar discs. Rather, the anulus forms a crescent-shaped mass of collagen, which is thickest anteriorly and tapers laterally toward the uncinate processes. Posteriorly, the anulus is merely a thin layer of paramedian vertically oriented fibers. The anterior longitudinal ligament (ALL) covers the front of the disc, and the posterior longitudinal ligament (PLL) reinforces the deficient posterior anulus fibrosus with longitudinal and alar fibers. In this way, the cervical anulus fibrosus is likened to a crescentic anterior interosseous ligament, rather than a ring of fibers surrounding the nucleus pulposus (Mercer and Bogduk 1999).

The Spine in Sports Injuries: The Cervical Spine

22.3 Biomechanics of the Cervical Spine The cervical spine is the most mobile of all the segments of the vertebral column. It allows an extensive range of motion in flexion and extension, which is mainly due to the upwardly oriented inclination of the superior articular surfaces. In flexion (forward movement), the anterior longitudinal ligament (ALL) is relaxed, while the posterior longitudinal ligament (PLL), the ligamenta flava, and the interand supraspinous ligaments are stretched. During flexion, the intervertebral discs are compressed anteriorly, the interspaces between the laminæ are widened, and the inferior articular processes glide upward, upon the superior articular processes of the subjacent vertebræ. Flexion of the cervical spine is arrested just beyond the point where the cervical convexity is straightened. In extension (backward movement), the opposite motions occur. Extension can be carried farther than flexion and is limited by stretching of the anterior longitudinal ligament (ALL), and by the approximation of the spinous processes. In the cervical spine lateral flexion and rotation always occur as combined movements. The upward and medial inclinations of the superior articular facet joint surfaces convey a rotary movement during lateral flexion, while pure rotation is prevented by their slight medial slope. During lateral flexion, the sides of the intervertebral discs are compressed, and the extent of motion is limited by the resistance offered by the surrounding ligaments. In sports-related injuries, the most common mechanism of cervical spine trauma is neck flexion with axial loading (Torg et al. 1987). Neck flexion causes the physiological cervical lordosis to disappear. The axial loading of the head is thus dissipated through a straight spine (Torg et al. 1987). Examples of axial loading injuries to the cervical spine are found in a variety of sports, such as: ● American football (Fig. 22.1) (player striking opponent with the crown of his helmet) or rugby (Fig. 22.2) (during the scrum phase of the game) ● Ice hockey (player striking his head on the board while doing a push or check) ● Diving in shallow water (Figs. 22.3–22.4) (head striking the ground) ● Gymnastics (Fig. 22.5) (athlete accidentally landing head down while performing a somersault on a trampoline) (Torg 1987).

The spectrum of cervical spine injury is related to the mechanism, the force involved, and the point of application of the force (Tall and DeVault 1993). Axial loading injuries of the cervical spine include vertebral fractures (Figs. 22.2 and 22.3), cervical disc herniations (Fig. 22.1), ligament rupture, facet fracture, and dislocations (Figs. 22.5 and 22.6). Neurologic deficits tend to be greater in athletes with spinal stenosis (Fig. 22.7), either developmental, or acquired through degenerative disease (Torg et al. 1997). Moreover, the biochemistry and biomechanics of the intervertebral disc and spine are age related. Thus, the adolescent and older athlete may have different concerns with regards to diagnosis, treatment, and prognosis after injury to the spine. Recent studies have indicated that there also is a gender differential regarding injuries of the cervical spine (Kelley 2000). Cervical strain injuries are more prevalent in female athletes than male athletes. For cervical disc injury and cervical disc herniation, the male to female incidence is approximately equal. With increasing participation of women in contact sports that cause major structural injury, a greater incidence of these injuries may be seen in women. The radiologist examining an athlete with cervical spine trauma, should recognize and understand the mechanism of injury (Pavlov and Torg 1987).

Fig. 22.1. Acute cervical disc herniation in a 32-year-old man who was injured during a football game. Contrast-enhanced CT scan of the cervical spine. At C5–C6, there is a disc herniation extending into the left lateral recess and into the intervertebral foramen. Note the asymmetric deformation of the dural sac and impingement on the left C6 nerve root

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Fig. 22.2a,b. Hyperflexion injury with simple anterior wedge fracture of C7 in a 23-year-old rugby player. MRI scan with sagittal T2-weighted (a) and sagittal T1weighted (b) images. The anterosuperior corner of the vertebral body C7 is depressed, and there is band of bone marrow edema subjacent to the upper endplate. The posterior wall is not displaced, the diameter of the spinal canal remains normal, and there is no medullary contusion

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a Fig. 22.3a–c. Jefferson fracture of C1 in a 26-year-old man patient who was injured in a diving accident. Non-contrast axial CT scan (a) with coronal (b) and three-dimensional reformatted images (c). There is a comminuted fracture of the anterior arch and a linear fracture of posterior arch (a). The coronal reformatted image shows lateral displacement of the lateral masses of C1 with respect to the superior articular surfaces of C2 (b). The 3-D volume rendered image confirms the comminuted fracture in the anterior arch of C1 (c)

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The Spine in Sports Injuries: The Cervical Spine

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Fig. 22.4a–c. Catastrophic neck injury (diving accident) with contusion and partial transsection of the spinal cord in a 23-yearold man. MRI examination with sagittal T1-weighted (a), sagittal T2-weighted (b) and coronal T2-weighted (c) scans. The study was obtained after anterior fixation at C5–C6–C7 with titanium plate. Despite the magnetic susceptibility artifacts caused by the instrumentation, the spinal cord contusion is clearly identified as a focal intramedullary high intensity abnormality on the T2-weighted scans

a

b Fig. 22.5a,b. Distracted hyperflexion injury in a young gymnast with anterior subluxation at C6–C7. Plain radiographs of the cervical spine in AP (a) and cross-table lateral (b) projection. The marked anterior displacement of C6 indicates disruption of all ligamentous structures and interfacetal dislocation. This finding is only visible on the lateral view. The cervicothoracic prevertebral soft tissue shadow is widened, indicating the presence of a hematoma secondary to the injury

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b

Fig. 22.6a–c. Bilateral interfacetal dislocation with anterior translation of C6 with regard to C7 in a 34-year-old woman following a catastrophic skiing injury. Non-contrast CT scans with axial images (a,b) and mid-sagittal reformatted image (c) show anterior displacement of C6 on C7 with marked steplike deformation of the spinal canal

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Fig. 22.7a,b. Cord contusion secondary to spinal stenosis in a 49-yearold recreational tennis player, who complained of neck pain and paresthesias in both arms after a collision with another player. MRI examination with sagittal T1-weighted (a) and sagittal T2-weighted images (b). Sagittal images show severe narrowing of the spinal canal due to chronic disc herniations and posterior osteophytes. There is a focal intramedullary area of increased signal intensity indicating cord contusion

The Spine in Sports Injuries: The Cervical Spine

Accurate radiological evaluation of the cervical spine must be performed immediately following the possibility of injury and in such a manner as not to compromise the neurologic status of the patient. Subtle radiographic findings indicating ligamentous injuries must be recognized in order to prevent cervical spine instability. Occult fractures are often difficult to diagnose on plain films. Therefore, in many trauma centers, computed tomography (CT) is increasingly being used to detect fractures.

22.4 Radiological Examination The radiological investigation of the cervical spine must be guided by the clinical presentation. Three major issues should be addressed (Mintz 2004): ● Stability of the cervical spine is essential element in sports. Instability of the cervical spine indicates damage to one or several of structural elements including the intervertebral disc, the ligaments, the osseous structures (vertebral bodies, facet joints) and the facet joint capsule. Instability should be suspected when there is lack of alignment of the vertebral bodies or facet joints, which may reflect subluxation (White and Panjabi 1987). ● Impingement can be defined as encroachment on either the spinal cord (through narrowing of the spinal canal) or the nerve roots (through narrowing of the intervertebral foramina). ● The term impairment indicates loss of function, ranging from pain to paraplegia. Impairment can be due to structural causes (e.g. disc herniation, fracture-luxation, ligament injury) or to mild functional causes. The purpose of the radiological investigation in the injured athlete is to document lesions that must be treated, such as disc disease or instability. Pain in itself is not an indication for imaging (for example, most acute burner or stinger injuries do not require imaging, see section 22.7) (Mintz 2004). On the other hand, when the athlete shows signs or symptoms of instability or neurological deficit, imaging studies are required to document potentially serious lesions. In most cases, the radiological examination of the cervical spine in sports injuries starts with plain radiographs, including frontal, lateral and odontoid projections. Additional views should be added as

needed, in order to decrease the incidence of missed fractures. When instability due to ligamentous injury is suspected, flexion and extension views should be obtained; this can only be done when a fracture has been ruled out. In more severe sports injuries, the use of computed tomography (CT) is required. Since the 1980s it has been shown that CT can document cervical spine fractures that are difficult or impossible to see on plain radiographs (Mace 1985). With new generation multi-row detector CT (MDCT) scanners, it only takes a few seconds to examine the entire cervical spine, from the clivus to the upper thoracic segments. The volumetric MDCT dataset can be used to make multiplanar reformations in axial, sagittal and coronal planes. The cervico-thoracic junction, which is often difficult to assess on plain radiographs to overprojection of the shoulders, is well depicted on CT. Moreover, CT is now the first choice modality to demonstrate osseous causes of instability such as fractures of the vertebral bodies, the posterior elements (facet joints, laminae and pedicles), and the odontoid. The less time-consuming CT examination, with sagittal and coronal reconstructions, has replaced conventional tomography for the detection of odontoid fractures and provides equivalent or greater diagnostic accuracy (Weisskopf et al. 2001). The most important limitations of MDCT in assessing the cervical spine are its relative inability to demonstrate damage to the neural elements (spinal cord, cervical nerve roots) and to the ligaments (transverse, alar, facet joint capsule, supraspinous, anterior and posterior longitudinal ligament). This is where magnetic resonance imaging (MRI) becomes useful, because of its intrinsically higher soft tissue contrast resolution. In an in vitro model with cadaver spine specimens, it has been shown that MRI reliably and directly allows assessment of spinal ligament tears of various types (White and Panjabi 1987; Emery et al. 1989; Kliewer et al. 1993). The foundation of any cervical spine MRI protocol consists of sagittal and axial T1- and T2-weighted scans. For sagittal scans, we use turbo spin echo (TSE) sequences with flow compensation to eliminate artifacts from CSF pulsations. Excellent T2-weighted contrast, with bright CSF signal can be obtained through the use of Restore (Siemens) or Drive (Philips) sequences which add a supplementary 90q pulse at the end of the TSE pulse train. For axial images with bright CSF, T2- or T2*-weighted sequences can be used; it is important to use thin section (3 mm or less slice thickness) contiguous axial images, to prevent miss-

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ing a facet, pedicle or soft-tissue injury (Mintz 2004). Gradient echo T2*-weighted scans provide excellent myelographic contrast, but are less sensitive for the detection of intramedullary lesions such as edema or contusion. Gradient echo images can be degraded by susceptibility (“blooming”) artifacts; this can be avoided through the use of 3D gradient echo scans with thinner slices. Fat suppression techniques, either with spectral fat saturation or inversion recovery, are important to demonstrate osseous and soft tissue injuries. In addition to the sagittal and axial imaging planes, a coronal sequence with intermediate to long TE is useful to show muscle injury (Mintz 2004). Diffusion-weighted imaging, with optional diffusion tensor fiber tracking techniques, is under study for the spinal cord.

22.5 Cervical Disc Herniation Traumatic sports injuries of the cervical spine can occur at the level of the disc, resulting in disc herniation, disc degeneration, and ultimately developmental stenosis. Acute disc pathology is the most common cause of sports-induced impingement syndromes. It can cause a variety of neurological complications including paraplegia, neuralgia and spasticity of the lower extremities due to compression of the spinal nerve roots and/or of the spinal cord. For example, acute traumatic herniation of a cervical intervertebral disk may lead to spinal cord injury. In one reported case, the injury was sustained during a “tugof-war” game, and the patient also suffered a brachial plexus injury in addition to a ruptured spleen (Lin et al. 2003). The radiological examination should focus on the detection of narrowing of the intervertebral foramina and spinal canal. Recent disc herniations tend to have a higher signal intensity on T2- or T2*-weighted images, whereas osteophytes present a low signal intensity. T2-weighted MR images are the method of choice to demonstrate abnormal intramedullary signal intensity due to extrinsic compression by an intervertebral disc. On MRI it can be difficult to distinguish between a disc herniation (“soft” disc) and an osteophyte (“hard” disc). The association between participation in several specific sports, and herniated lumbar or cervical intervertebral discs has been examined in a case-

controlled multicenter epidemiologic study (Mundt et al. 1993). The authors analyzed 287 patients with lumbar disc herniation and 63 patients with cervical disc herniation, each matched by sex, source of care, and decade of age to one control who was free of disc herniation and other conditions of the back or neck. Specific sports considered were baseball or softball, golf, bowling, swimming, diving, jogging, aerobics, and racquet sports. The authors found that most sports are not associated with an increased risk of herniation, and may in fact be protective. Relative risk estimates for the association between individual sports and lumbar or cervical herniation were generally less than or close to 1.0. There was, however, a weak positive association between bowling and herniation at both the lumbar and cervical regions of the spine. Use of weight lifting equipment was not associated with herniated lumbar or cervical disc, but a possible association was indicated between use of free weights and risk of cervical herniation (relative risk, 1.87; 95% confidence interval, 0.74 to 4.74). Cervical disc herniation occurring in close association with playing football (soccer) has also been reported (Fig. 22.1) (Tysvaer 1985).

22.6 Impingement Syndromes and Spinal Stenosis Neurological symptoms indicating a cervical spinal cord lesion, which occur after a spine injury from contact sports, require a precise work up to detect cervical spinal stenosis. In these instances, advanced imaging techniques such as CT and MRI more accurately identify true spinal stenosis than radiographic bone measurements alone can provide (Cantu 1998). The presence of a narrow cervical spinal canal constitutes a significant risk factor for the development of traumatic neck injuries (including sportsrelated injuries) even without a fracture or dislocation (Epstein et al. 1980). In a study of 39,377 athletes, a decreased antero-posterior diameter of the spinal canal was found to be a predisposing factor to the occurrence of cervical spinal cord neurapraxia with transient quadriplegia (Torg and Pavlov 1987). This distinct clinical syndrome is characterized by sensory changes (including burning pain, numbness, tingling, and loss of sensation) as well as motor changes (ranging from weakness to complete paraly-

The Spine in Sports Injuries: The Cervical Spine

sis) (Torg et al. 1986). Neuropraxia of the cervical spinal cord with transient quadriplegia is caused by spinal cord compression during forced hyperextension or hyperflexion, in athletes with diminution of the anteroposterior diameter of the spinal canal. In one study, there was a statistically significant spinal stenosis (p