Chapter 71 Spinal Injuries in Sports
Section One
Sports-Specific Epidemiology
Each year, approximately 10,000 cases of SCI occur in the United States.1 Participation in sporting activities accounts for nearly 10% of these and is the fourth most common cause of SCI (after motor vehicle accidents, violence, and falls).2,3 Sports-related SCIs also occur at a younger mean age of 24 and are the second most common cause of SCI in the first three decades of life.4,5
Spinal injuries are more common in nonorganized sports such as diving and surfing than in organized sports.1,6 The challenge in this population is that rules, supervision, and training are limited. These limitations make it difficult to improve injury patterns by enforcing safety guidelines and manufacturer standards. Although less frequent, spinal injury in organized sports have a much higher public profile. Several organized sports, including football, ice hockey, rugby, skiing, snowboarding, and equestrian sports, have been identified as placing the participant at high risk for SCI.7–10
Sport-Specific Risks to the Spine
American Football
American football involves approximately 1.4 million athletes at the junior/senior high school level, 75,000 in college, and 1000 in professional play.11 This total contrasts roughly with 60,000 rugby players in the United States. With the innumerable high-velocity collisions incurred during practice and games, it is the most dangerous sport for SCI in terms of exposure and is responsible for the highest risk of cervical spine trauma among organized sports participants. Although American football has a lower per participant rate of catastrophic cervical spine injuries than ice hockey or gymnastics, the huge number of participants translates into the largest overall number with catastrophic cervical spine injuries.11
Notably, a significant increase in catastrophic cervical trauma coincided with the development of the modern football helmet. However, rule changes in 1976 prohibiting playing techniques that used the top of the helmet as the initial point of contact for blocking and tackling (spearing) have significantly reduced this trend. From 1976 to 1987, the rate of cervical injuries decreased 70%, from 7.72 per 100,000 to 2.31 per 100,000 at the high school level.12 Traumatic quadriplegia decreased approximately 82% over the same period.13 Since most football players are injured during tackling, defensive players (defensive backs, members of the kickoff teams, and linebackers) are at the highest risk of injury. Almost all cervical spine injuries occur when a player strikes an opponent with high velocity using the vertex of the helmet or with the head down. This action results in a significant axial load, often with a degree of flexion. The cervical musculature that is responsible for maintaining extension is much stronger than that used in maintaining flexion. Thus, a player who lowers his head in blocking or tackling increases his vulnerability to cervical injury by placing his cervical spine in a position that is less able to absorb the consequent energy.
Baseball and Softball
Minor spinal injuries are fairly common in baseball and softball, but catastrophic injuries do occur. Participants who slide headfirst into a base have the most risk of catastrophic SCI. If the hands of the runner separate, the top of his head can collide with the leg of the defensive player, creating a great deal of axial load transmission to the vertebral column. Although the use of breakaway bases substantially decreases the risk for occurrence of sliding-related injuries, serious injuries can still occur. The use of even lower profile bases and the outlawing of sliding have also been suggested.14
Basketball
Basketball involves rapid changes in direction and explosive movements, causing repeated stresses to the spinal vertebrae. Thus, it is not surprising that the most common neurologic risk in basketball is to the player’s spine. A variety of acute back injuries, such as lumbosacral sprains, contusions, and facet joint and pars interarticularis injuries, are common.15,16 In addition, this sport is a leading cause of sports-related disc disease and has been reported to be the second most common cause of disc herniation among athletes.17 Herniated discs usually arise dorsally or dorsolaterally and occur as a consequence of numerous microtraumas to the intervertebral disc compounded by chronic overstraining. Cervical cord neurapraxia has also been reported in basketball players.
Cycling
Neck and back pain are common complaints in cyclists, occurring in over half of participants. The odds of female cyclists developing neck and shoulder overuse problems have been reported to be 1.5 and 2.0 times greater, respectively, than for their male counterparts.18 Neck pain is partially the result of a combination of increased load on the arms and shoulders required to support the cyclist and hyperextension of the neck in the horizontal, bent forward position of riding. These stresses are compounded in bicycles improperly fitted to the cyclist. Lower back pain often results from hyperextension of the angle between the spine and pelvis, which increases stress at the promontorium.
Equestrian Sports
Approximately 20% of the injuries sustained by an equestrian involve the CNS. One study found that 13% of the patients had injury to the spinal cord, with the cervical region most commonly involved.19 There does not seem to be any correlation between risk of injury and the participant’s age, gender, or experience.20 Equipment failure has been shown to be a common cause of injury. Although jumping events have garnered the majority of attention in the past decade due to catastrophic injuries to celebrities such as Christopher Reeves, the particular type of equestrian activity with the most risk to the spinal cord is unequivocally rodeo rough-stock riding (bull, bareback bronco, and saddle bronco riding).21 Common spinal injuries include cervical and lumbar sprain, acute torticollis secondary to being thrown, and cervicothoracic strain secondary to missing the animal in the steer wrestling competition.
Gymnastics
Gymnasts are a group of athletes with perhaps the greatest risk of back injury. A National Registry of Gymnastic Catastrophic Injury was established in 1978, and 20 gymnasts injured the cervical spine in its first 4 years. Of these, 17 remained quadriplegic and 3 died secondary to their injury. Notably, most of the injuries occurred in experienced gymnasts during practice.22 The sport accounts for a significant proportion of all sports-related SCIs, and an 18-month study of elite and subelite female gymnasts reported a back injury rate of 14.9%.23 Injuries are commonly to the cervical spine, and the sport is by far the leading cause of quadriplegia in women’s sports.
Ice Hockey
The sport of ice hockey has experienced a marked increase in the occurrence of cervical spine injuries through its history.24 Major vertebral column injury occurred at an increased rate between 1982 and 1993, with a mean of 16.8 fracture-dislocations per year during that period. Checking an opponent from behind, which typically produces a headfirst collision of the checked player with the boards, has been identified as an important causative factor in cervical spine trauma in hockey. Changes in the rules that prohibit checking from behind and checking of an opponent who is no longer controlling the puck seem to be decreasing the incidence of these injuries, and data suggest that fewer cases of complete quadriplegia have been caused by these playing techniques since the rule changes have been instituted.24
Mixed Martial Arts
Mixed martial arts (MMA) is a full-contact sport combining elements of boxing, kickboxing, and wrestling. It has evolved since 2001 to become a mainstream sport with improved regulations to minimize injury.25 Most competitions now forbid head butting; stomping or kneeing on an opponent on the ground; and striking the throat, spine, or back of the head. Also, athletes must fight within a predetermined weight class. Despite the dramatic impacts that a participant receives during competition, the overall injury rate in MMA competitions has been determined to be similar to other combat sports, including boxing.25,26 While no catastrophic spinal injury has been reported during competition in the past decade, many of the maneuvers seem to be particularly risky.
Maneuvers known as “spinal locks” are often employed in competition. A spinal lock is performed by forcing the spine beyond its normal ranges of motion and is typically accomplished by bending or twisting the opponent’s head or upper body into abnormal positions. These maneuvers can be separated into two categories based on their primary area of effect on the spinal column: spinal locks on the neck are called neck cranks, and locks on the lower parts of the spine are called spine cranks. Spine cranks are less commonly performed in competition than neck cranks because they are more difficult to apply. These can commonly strain the spinal soft tissue and musculature and if forcefully and/or suddenly applied could theoretically result in ligament damage, bony fracture or displacement, and SCI.
Four of the most commonly utilized maneuvers in the sport are the O goshi (judo), in which the fighter uses his shoulders to swing the opponent over his hips; the suplex (jujitsu), in which the fighter grabs the opponent around the waist and lifts him up over his shoulder to fall forward onto his face; the souplesse, a variant of the suplex, in which the opponent is rotated and slammed down onto his back; and the guillotine drop (a choke hold). A detailed kinematic and biomechanical analysis of these maneuvers showed that the forces involved are of the same order as those involved in whiplash injuries and of the same magnitude as compression injuries of the cervical spine.27
Rugby
Spinal injuries, especially to the cervical region, are common in the traditional tackle games of rugby union, rugby league, and Australian rules football. A retrospective study of SCIs in rugby from 1960 through 1989 identified 117 catastrophic neck injuries. It was also reported that for every serious rugby-associated SCI, 10 severe neck injuries occurred that did not involve the cord.28
Three specific activities during the game of rugby—the tackle, tight scrum, and loose play (ruck and maul)—result in the majority of injuries to the cervical spine.29 Cervical spine injury often results from impact between the tackler’s head and the ground or the body of the opponent (usually the thigh). The immediate halt of the head’s forward progress results in compression fractures of the vertebral bodies from axial forces transmitted down the spine. These forces are increased significantly if the player’s neck is flexed, which eliminates the normal lordosis of the cervical spine. An injury during a high tackle from behind often results from hyperextension secondary to the head being pulled back and down. If the tackle is from the side, hyperflexion injury often results. Rotational forces are also a factor in these injuries, especially if the tackle is performed with only one arm. Double tackles, often referred to as “sandwich” or high-low tackles, are more common near the goal with a concentration of defenders merging on the ball carrier. They can cause injury to both the offensive and defensive player. If the defensive players miss their target, they can collide into each other with considerable force at unexpected angles. If the tackle is successful, the offensive player’s body is forced in two directions. This inhibits the player from moving with either force completely, increasing rotational and shearing stresses to the spine.
Water Sports
The water sport with the most risk for spinal injury is by far recreational diving. Mishaps have been reported to account for up to 75% of all recreation-related spinal cord injuries.30–32 These injuries tend to occur in teenage males involved in unsupervised activities during the summer months. The most common cause of injury is the participant striking his head on the bottom of a pool, lake, or ocean after having miscalculated the depth of the water. Diving injuries occur almost exclusively to the cervical spine and often result in quadriplegia. Forward flexion, often with axial compression, is the usual mechanism of injury. The C5 level is most commonly involved, likely attributable to the wide range of motion and the relatively smaller size of the vertebral canal at this level.33
Wrestling
The sport of wrestling has been associated with spinal injury, most commonly in the cervical region.34 Although the intervertebral discs, joints, and ligaments are somewhat resistant to compression stresses, they are very susceptible to injury by rotational and shearing forces. Most injuries result from landing with the body twisted on the head and neck and occur during takedowns and sparring. Various combinations of thoracolumbar spine abnormalities, such as spondylolysis, are also prevalent in this population of athletes.
Section Two
Cervical Spine and Brachial Plexus
Cervical Sprains, Strains, and Contusions
One of the most common causes of neck pain in the athlete is the constellation of cervical strain, sprain, and contusion. A strain is defined as a stretch injury at the musculotendinous junction or within the muscle itself. If the ligamentous structures of the spine are more involved, it is termed a sprain. Contusions are blunt-force injuries to soft tissue. Injuries in this group most often occur when a force is applied to a contracting muscle. This creates an eccentric contraction resulting in some degree of tensile failure. The most vulnerable area for this injury is at the myotendinous junction as well as areas of greater type II (fast-twitch muscle fibers) concentration.35 Most injuries involve an overlap of all three components, with the severity of injury being a consequence of the magnitude and direction of the applied forces.
The natural course of these injuries is a gradual resolution of pain and muscle spasm with conservative treatment. Obviously, an athlete who presents with pain and limited cervical range of motion should undergo a complete clinical and radiographic examination. At a minimum, this imaging should include dynamic (flexion-extension) plain radiographs in at least two orthogonal planes of the entire cervical spine (occiput to C7-T1 junction). If the injury only appears to be a strain, sprain, or contusion, a cervical collar may be continued until any severe muscle spasm has resolved, which usually takes 7 to 10 days. Use of a cervical collar for longer than this length of time has been demonstrated to result in significant deconditioning and weakening of the cervical musculature.35 Repeat dynamic radiographs can then be taken to ensure that the athlete does not have any delayed instability that could present after the splinting effect of muscle spasm has resolved. If these tests are negative, the collar can be discontinued and physical therapy begun. This should include gentle range-of-motion and isometric strengthening exercises, followed by a more sport-specific regimen.
The athlete may return to play when he or she is asymptomatic, has full range of motion, and has baseline sport-specific neck function. After returning to competition, the athlete should continue stretching and strengthening exercises in an attempt to reduce the incidence and severity of any future injury. The use of a sport-specific protective orthosis (e.g., a “horse collar” in American football) to prevent further injury may be employed, although significant data on their actual benefit are limited. Such orthoses used in American football have been shown to limit hyperextension of the cervical spine while allowing enough extension to prevent axial loading injury.36
Brachial Plexus Neurapraxia
Brachial plexus neurapraxia (also known as stinger-burner or transient brachial plexopathy or nerve root neurapraxia) is a transient neurologic event characterized by pain and paresthesia in a single upper extremity following a blow to the head or shoulder. This condition is one of the most common occurrences in collision sport participation and is not the result of an SCI. It was first described in 1965 by Chrisman et al.37 Because the mechanism was thought to be direct force applied to the shoulder with the neck flexed laterally away from the point of contact, the condition has also been referred to as “cervical pinch syndrome.”38 The symptoms most commonly involve the C5 and C6 spinal roots. The affected athlete can experience burning, tingling, or numbness in a circumferential or dermatomal distribution.38 The symptoms may radiate to the hand or remain localized in the neck. These athletes often maintain a slightly flexed cervical spine posture to reduce pressure on the affected nerve root at the neural foramen or may hold or elevate the affected limb in an attempt to decrease tension on the upper cervical nerve roots.
Weakness in shoulder abduction, external rotation, and arm flexion is a reliable indicator of the injury.39 If weakness is a component, it usually involves the C5-6 neurotome. The radiating arm pain tends to resolve first (within minutes), followed by a return of motor function (within 24–48 hours). Although the condition is usually self-limiting and permanent sensorimotor deficits are rare, a variable degree of muscle weakness can last up to 6 weeks in a small percentage of cases.
As mentioned previously, this injury is most commonly the result of downward displacement of the shoulder with concomitant lateral flexion of the neck toward the contralateral shoulder. This is thought to result in a traction injury to the brachial plexus. The condition may also result from ipsilateral head rotation with axial loading resulting in neural foramen narrowing and compression-impaction of the exiting nerve root within the foramen.40,41 Direct blunt trauma at the Erb point, located superficially in the supraclavicular region, has also been reported to be a cause.42 This can occur when an opponent’s shoulder or helmet drives the affected athlete’s shoulder pad directly into this area.
Stingers with prolonged neurologic symptoms are the most common reason for high school and college athlete cervical spine evaluations in an emergency department.43–45 The athlete commonly demonstrates a full, pain-free arc of neck motion with no midline palpation tenderness on examination. If tenderness is present or unilateral neurologic symptoms persist, a paracentral disc herniation with associated nerve root compression should be considered. This is usually accompanied by the sudden onset of dorsal neck pain and spasm. Monoradiculopathy characterized by radiating pain, paresthesias, and/or weakness in the upper extremity also occurs secondary to compression and inflammation of the cervical root.
Although this injury is usually considered benign, an athlete that suffers an episode of brachial plexus neurapraxia should be immediately removed from competition until symptoms have fully resolved. On-field evaluation should include palpation of the cervical spine to determine any points of tenderness or deformity. Sensation and muscle strength should be evaluated using the unaffected limb as a point of reference. Weakness in the muscles innervated by the upper trunk of the brachial plexus is often observed. These include the deltoid (C5), biceps (C5-6), supraspinatus (C5-6), and infraspinatus (C5-6) muscles.46,47 The shoulder of the affected limb should also be evaluated, paying particular attention to the clavicle, acromioclavicular joint, and supraclavicular and glenohumeral regions. Percussion of the Erb point can be performed in an attempt to elicit radiating symptoms. Obviously, the athlete should be evaluated for other serious injuries such as cervical spine fractures and dislocations. It is unusual to find lower brachial trunk injury patterns involving the C7 or C8 nerve roots. It is also uncommon to see persistent sensory deficits involving either the lower or upper extremities. This condition is always unilateral and has never been reported to involve the lower extremities. If bilateral upper extremity deficits are present, SCI should be at the top of the differential diagnosis. Localized neck stiffness or tenderness with apprehension to active cervical movement should alert the examiner to a potentially serious injury and the subsequent initiation of full spinal precautions, including spine board immobilization and transport for imaging.
If the player does not complain of neck pain, decreased range of motion, or residual symptoms, he or she can usually return to competition. If symptoms do not resolve or there is persistent pain, prompt imaging of the brachial plexus via MRI is recommended. If the symptoms persist for over 2 weeks, electromyography can be performed to establish the distribution and degree of injury.48 Residual muscle weakness, cervical anomalies, or abnormal electromyographic studies are exclusion criteria from return to play.44
By definition, brachial plexus neurapraxia is a transient phenomenon. It usually does not require formal treatment. The athlete should be followed closely with repeat neurologic examinations since although the condition usually resolves in minutes, motor weakness may develop hours to days following the injury.39,45 Repeated injury may result in long-term muscle weakness with persistent paresthesias, resulting in permanent removal from competition.49 Options in participants to decrease the risk of future occurrences are to change their field positions or modify their playing techniques.
Central Cord Syndrome
Burning hand syndrome is considered to be a variant of central cord syndrome. It is characterized by burning dysesthesia in both upper extremities and is likely the result of vascular insufficiency affecting the medial aspect of the somatotopically arranged spinothalamic tracts.50,51 The lower extremities may occasionally be involved and weakness may occasionally be evident. Cervical spine fracture or soft tissue injury is frequently associated with these syndromes, and any athlete exhibiting this condition should be initially treated as having an SCI (see section titled On-Site Evaluation and Management of Spinal Cord Injury).52
Cervical Cord Neurapraxia and Transient Quadriplegia
Neurapraxia of the cervical spinal cord (CCN) resulting in transient quadriplegia has been estimated to occur in 7 per 10,000 football players.53 This alarming injury is characterized by a temporary loss of motor or sensory function and is thought to be the result of a physiologic conduction block without true anatomic disruption of neuronal tissue. The affected athlete may complain of pain, tingling, or loss of sensation bilaterally in the upper and/or lower extremities. A spectrum of muscle weakness is possible, varying from mild quadriparesis to complete quadriplegia. The athlete has a full, pain-free range of cervical motion and does not complain of neck pain. Hemiparesis or hemisensory loss is also possible.
The condition is thought to result from a pincer-type mechanism of compression of the cord between the dorsocaudal portion of one vertebral body and the lamina of the vertebra below.54 Although this can also occur during hyperflexion, it is more commonly the sequela of extension movements with infolding of the ligamentum flavum, which can result in a 30% or more reduction of the anteroposterior diameter of the spinal canal.55 The spinal cord axons become unresponsive to stimulation for a variable period of time, essentially creating a “postconcussive” effect.56
CCN is described by the neurologic deficit, the duration of symptoms, and the anatomic distribution. A continuum of neurologic deficits that range from sensory only, sensory disturbance with motor weakness, or episodes of complete paralysis may occur. These may be described as paresthesia, paresis, or plegia. An injury is defined as grade 1 if the CCN symptoms do not persist for longer than 15 minutes. Grade 2 injuries are defined as lasting from 15 minutes to 24 hours. Grade 3 injuries persist for 24 to 48 hours. All four extremities may be involved; this is considered a “quad” pattern. Upper- and lower-extremity patterns may also be observed.57
By definition, CCN is transient, and complete resolution generally occurs within 15 minutes but may take up to 48 hours. Steroid administration in accordance with the Bracken protocol58 in this population is controversial. No controlled studies have reported that the administration of steroids has altered the natural history of athletes with CCN.44 In players who return to football, the rate of recurrence has been reported to be as high as 56%.57
A considerable amount of controversy exists regarding whether the presence of cervical stenosis makes an athlete more prone to sustaining CCN and even permanent neurologic injury.59,60 This controversy is compounded by the imprecise methods of objectifying whether an individual suffers from stenosis. The anteroposterior diameter of the spinal canal (measured from the dorsal aspect of the vertebral body to the most ventral point on the spinal laminar line) determined from lateral cervical spine radiographs is considered normal if there is more than 15 mm between C3 and C7. Cervical stenosis is considered to be present if the canal diameter is less than 13 mm. However, this measurement varies widely secondary to variations in landmarks used for measurement, changes in target distances for making the radiographs, patient positioning, differences in the triangular cross-sectional shape of the canal, and magnification of the canal because of a patient’s large body habitus. In an effort to eliminate this variability, Torg and Pavlov designed a ratio method for determining the presence of cervical stenosis, comparing the sagittal diameter of the spinal canal with the sagittal midbody diameter of the vertebral body at the same level.61 A ratio of 1:1 was considered normal, and less than 0.8 was indicative of significant cervical stenosis. This ratio was found to mislabel many athletes with adequately sized canals but large vertebral bodies as being stenotic. This observation, as well as an unprecedented ability to image the vertebral column, intervertebral discs, spinal canal, cerebrospinal fluid (CSF), and spinal cord directly, have made MRI, and not boney landmarks, the currently preferred method of choice for assessing “functional spinal stenosis.” MRI assessment of CSF signal around the spinal cord, termed the functional reserve, can be determined, and the visualization of the CSF signal, its attenuation in areas of stenosis, and changes on dynamic sagittal flexion-extension MRI studies are now the standard in diagnosing this condition. An absent CSF pattern on axial and, particularly, sagittal MRI is diagnostic of functional stenosis.
It had been previously accepted that young athletes who suffered an episode of CCN were not predisposed to permanent neurologic injury.60,62 This assumption has recently been called into question now that a player who experienced a CCN subsequently sustained a quadriplegic injury.63
Traumatic Intervertebral Disc Herniation
Acute herniation of an intervertebral disc can occur during participation in sports and in the athletic population. Those involving the cervical spine are less common than lumbar disc injuries and usually involve the older athlete. Compared with the overall incidence of disc herniation in the general public, the incidence is likely increased in the high-performance athlete competing in contact sports such as football and wrestling.64,65 Conversely, participation in noncontact sports might actually be protective against the development of cervical or lumbar disc herniation. This is likely the result of improved muscular conditioning protecting the disc from stresses transmitted to the spine.66
Athletes with symptomatic cervical disc herniations most often present with varying degrees of neck or arm pain. Although the types of symptoms are similar in athletes and nonathletes, they may seem to be more severe in the competing athlete due to the demands of the specific sport. A traumatic central disc herniation typically presents with the sudden onset of dorsal neck pain and paraspinous muscle spasm as well as true radicular arm pain or referred pain to the periscapular area.67 Extrusion of disc material into the central spinal canal can result in acute cord compression and injury. Clinically, the athlete may present with acute paralysis of all four extremities and a loss of pain and temperature sensation.
In almost all cases except for those involving acute neurologic deficit, the initial 6 to 8 weeks of treatment should be nonoperative. This is especially important for an athlete who wishes to return to competition since this will be easier to accomplish without an operative intervention in most circumstances. As in the nonathlete, treatment options include rest, activity modification, anti-inflammatory medication, immobilization, cervical traction, and occasionally therapeutic injections.35 In most cases, the symptoms slowly resolve with these modalities, and a gradually increasing intensity of exercises can be initiated. These should at first emphasize isometric strengthening and cervical range of motion, followed by more sport-specific exercises. The athlete can return to competition when asymptomatic and after he or she has regained full strength and painless range of motion.
Minor Cervical Fractures
Compression Fractures
Individuals found to have suffered an isolated cervical compression fracture are usually treated with a semirigid cervical collar for 8 to 10 weeks. At the conclusion of immobilization, dynamic (flexion-extension) radiographs should be obtained to rule out a more severe ligamentous disruption.35
Spinous Process Fractures
Fractures of the spinous processes most commonly involve the lower cervical and upper thoracic area, occur as isolated injuries, and are stable. They occur via three mechanisms. The most common involves a strenuous contraction of the trapezius and rhomboid muscles, which avulses the spinous process. The C7 level is the most commonly involved, and this injury was previously termed clay-shoveler’s fracture. A second mechanism of injury is a hyperflexion or hyperextension injury to the neck, resulting in avulsion of the spinous process by the supraspinous and interspinous ligaments. This mechanism of injury is most commonly associated with a high-energy trauma, such as from a motor vehicle accident, but can also occur during contact sports such as football, gymnastics, and hockey.68 A less common mechanism described in the literature entails a direct blow to the spinous process.
Catastrophic Cervical Spine Injury
A structural distortion of the cervical spinal column associated with actual or potential damage to the spinal cord is classified as a catastrophic cervical spine injury.67 Sports-related cervical spine injuries are divided into three groups that provide useful information when deciding when an athlete is ready to return to play.1,6,69 Type 1 injuries are those in which the athlete sustains permanent SCI. This category includes both immediate, complete paralysis and incomplete SCI syndromes. The incomplete injuries are of basically four types: Brown-Séquard syndrome, anterior spinal syndrome, central cord syndrome, and mixed types. Mixed types include the finding of crossed motor and sensory deficits with more prominent involvement of the upper extremities, which is considered to be a central cord/Brown-Séquard variant. There are, in addition, a few individuals in whom the neurologic deficit is relatively minor but who demonstrate an associated spinal cord pathology on imaging studies. For example, a high-intensity lesion within the spinal cord seen on MRI documents a spinal cord contusion. Type 2 injuries occur in individuals with normal radiographic studies. These deficits completely resolve within minutes to hours, and eventually the athlete has a normal neurologic examination. An example of the type 2 injury is the burning hands syndrome discussed earlier, which is a variant of central cord syndrome characterized by burning dysesthesias of the hands and associated weakness in the upper extremities.50 Most of these patients have normal radiographic studies, and their symptoms completely resolve within about 24 hours. Although certainly dramatic, these injuries are usually not considered catastrophic. Type 3 injuries comprise those with radiographic abnormality without neurologic deficit. This category includes fractures, fracture-dislocations, ligamentous and soft tissue injuries, and herniated intervertebral discs.
Unstable fractures and/or dislocations are the most common cause of catastrophic cervical spine trauma. The most common primary injury vector is axial loading with flexion occurring in football and hockey.70,71 Eighty percent of injuries to the cervical spine result from the accelerating head and body striking a stationary object or another player.72,73 The cervical spine is compressed between the instantly decelerated head and the mass of the continuing body when an axial force is applied to the vertex of the helmet. In neutral alignment, the cervical spinal column is slightly extended as a result of its normal lordotic posture, and it is believed that compressive forces can be effectively dissipated by the paravertebral musculature and vertebral ligaments. This buffering cervical lordosis is eliminated when the cervical spinal column is straightened and large amounts of energy are transferred directly along the spine’s longitudinal axis.71 Under high enough loads, the cervical spine can respond to this compressive force by buckling.
Two major patterns of spinal column injury result from the compression injury vector. Compression-flexion injury is the most common variant that results from the combination of axial loading and flexion. It results in shortening of the anterior column because of compressive failure of the vertebral body and lengthening of the posterior column because of tensile failure of the spinal ligaments.74 If the cervical vertebra is subjected to a relatively pure compression force, both the anterior column and posterior column shorten, resulting in a vertical compression (burst) fracture. The vertebral body essentially explodes, during which disc material extrudes through the fractured end plate, and osseous material retropulses into the spinal canal, resulting in possible cord damage.75 Alternatively, a significant SCI may occur without major disruption of the spinal column’s integrity. This type of injury is the result of transient spinal column distortion with energy transfer to the spinal cord.
Catastrophic cervical trauma caused by the primary disruptive vector flexion generally results from either a direct blow to the occipital region or rapid deceleration of the torso. The flexion-distraction injury most likely to result in spinal cord dysfunction is a bilateral facet dislocation.76,77 Unilateral facet dislocation, associated with cord injury in up to 25% of cases, can occur with the addition of axial rotation to the distractive force.78 It should be recognized that unstable cervical fracture-dislocations do not always result in upper motor neuron dysfunction. A unilateral facet dislocation can cause a monoradiculopathy due to foraminal compression of a nerve root on the side of the dislocated articular process. In other cases, major osseous or ligamentous damage produces no neurologic impairment. SCI potential in these scenarios is based on the amount of lost structural integrity of the vertebral column.67
Upper Cervical Spine Injury
For the purposes of sports-related injuries, the upper cervical spine is considered to include the occiput, atlas (C1), and axis (C2). The major function of the atlanto-occipital joint is motion in the sagittal plane, which accounts for 40% of normal flexion and extension of the spine and 5 to 10 degrees of lateral bending. The midline atlantodens articulation is stabilized by the transverse atlantal ligament, which prevents forward translation of the atlas. This specialized osseoligamentous anatomy allows the atlas to rotate in a highly unconstrained manner. The atlantoaxial complex is responsible for 40% to 60% of all cervical rotation.79 This rotation is limited by the alar ligaments extending from the odontoid process to the inner borders of the occipital condyles. The apical ligaments attach the odontoid centrally to the ventral foramen magnum. Atlantoaxial joint strength is provided by the transverse ligament and the lateral joint capsules.48
Spinal cord damage due to fractures or dislocations involving the upper cervical spine is rare because proportionately greater space exists within the spinal canal than with the lower cervical segments. Injuries that destabilize the atlantoaxial complex (fracture of the odontoid or rupture of the transverse atlantal ligament) are most likely to result in spinal cord dysfunction. Flexion is the most common cause of injury at the atlantoaxial joint. Odontoid fractures can also result from extension injuries. Unilateral rotary dislocations are usually the result of rotational forces. Cord compression is unusual with a burst fracture of the atlas or traumatic spondylolisthesis of the axis because these osseous injuries further expand the dimensions of the spinal canal. If anteroposterior radiographs demonstrate spreading of the lateral masses of greater than 7 mm, the transverse ligament is likely torn. Bilateral pedicle fractures of the axis may occur from extension of the occiput on the cervical spine. Importantly, although these injuries can result in instability, they usually do not cause neurologic deficits due to the anatomically wide spinal canal that is also present at this level.48 If an upper cervical cord injury does occur, diaphragmatic paralysis with acute respiratory insufficiency can occur along with quadriplegia since the phrenic nerve arises from three cervical nerve roots (C3-5).
Lower Cervical Spine Injury
Each motion segment can be separated into an anterior and a posterior column. Stability of a cervical segment is derived mainly from the ventral spinal elements. Compression of the spinal column is primarily resisted by the vertebral bodies and intervertebral disc, whereas shearing forces are opposed primarily by paraspinal musculature and ligamentous support. Instability of the lower cervical spine has been defined radiographically as translational displacement of two adjacent vertebrae greater than 3.5 mm or angulation of greater than 11 degrees between adjacent vertebrae.80
The majority of fractures and dislocations occur in the lower cervical region. Lower cervical spine injuries are defined by the forces acting on the area (i.e., flexion, extension, lateral rotation, axial loading). Dislocated joints are usually the result of a flexion mechanism with either distraction or rotation. The ligamentous structures are the primary restraints to distraction of the spine.79 Compression of the dorsal structures as well as damage to the ventral structures is usually the result of extension or whiplash injuries. This mechanism of injury commonly results in tearing or the anterior longitudinal ligament and fractures of the dorsal elements.48
Compressive forces usually result in vertebral body fractures. These are commonly seen in spear tackling, a tackle in football in which a player’s entire body is launched head first—spear-like—against an opponent, resulting in significant axial loading on the cervical spine because the top of the head is the “spear point” of contact.81 This population commonly has a flexed posture to the head and a loss of the protective cervical lordosis.48 Large axial loads can result in protrusion of disc material or fractured bone into the spinal canal. This is the most common mechanism for sports-related quadriplegia.82,83 The C3-4 level is most commonly involved in cases of quadriplegia secondary to cervical dislocations.84,85
On-Site Evaluation and Management of Spinal Cord Injury
Primum non Nocere
The most important rule in dealing with potentially injured athletes is that an unstable spine injury can be easily converted into an injury with permanent neurologic deficit if mishandled. Because severe athletic-related injuries are relatively rare, the experience of the on-site medical staff is usually limited. Thus, everyone who shares responsibility for treating spine-injured athletes should be adequately trained and receive frequent refresher courses in the care of possible injury situations. The Inter-Association Task Force for Appropriate Care of the Spine-Injured Athlete was formed in 1998 and developed guidelines for the treatment of the catastrophically injured athlete.86 The five categories of on-field management are (1) preparation for any neurologic injury, (2) suspicion and recognition, (3) stabilization and safety, (4) immediate treatment and possible secondary treatment, and (5) evaluation for return to play.
Prior preparation should ensure that all of the proper equipment (e.g., spine boards, cervical collars or immobilization devices, cardiopulmonary resuscitation equipment, and stretchers) is available on site and easily accessible during a sporting event. Additionally, specific equipment for protective gear removal (e.g., football face mask) should also be readily available. There should be a clear hierarchy among the medical staff, indicating one member as the “captain” who directs the efforts of the team. In addition, arrangements should be made in advance to have ambulance services on site or close at hand. Preparation allays discomfort among providers and fosters efficiency and good decision making in the event of injury.72 It should also be mentioned that those who would treat injured athletes are legally responsibile for their actions, and precedent exists for legal action against team physicians and trainers who fail to properly care for those players.80
On-Site Management
The immediate treatment of the player who has suffered an SCI should follow standard trauma protocols that address airway, breathing, and circulation. During this assessment, a rapid evaluation of the athlete’s level of consciousness may also be performed. Unless the player is unconscious or airway or breathing considerations exist, he or she should be left in the position in which he or she lies, until safe transfer onto a spine board can occur. If an athlete is wearing protective gear with a face mask, the face mask should be removed. If the player is wearing a helmet, it can usually be left in place until the head and neck can be adequately immobilized.87 The following situations require removal of the helmet: (1) a loose-fitting helmet that does not hold the head securely, thereby allowing the head to remain mobile; (2) an uncontrolled airway or inadequate ventilation provided even after removal of the face mask; (3) a face mask that cannot be removed after a reasonable period of time; and (4) a helmet that prevents immobilization for transport in an appropriate position.86 If necessary, the helmet should be removed with concomitant occipital support or simultaneous removal of shoulder pads (in American football). If left in place following helmet removal, the shoulder pads may cause cervical hyperextension. Obviously, if the helmet is removed, cervical immobilization must be maintained during the procedure.
The initial objective in this primary survey is to assess the athlete for immediately life-threatening conditions and to prevent further injury. During this primary survey, appropriate resuscitation procedures are instituted and the emergency medical system is activated immediately on recognizing a life-threatening problem or serious spinal injury.88
If breathing is of insufficient depth or rate, assisted ventilation is required. On the field, this usually is performed by using a bag-valve device and face mask. Hypoxia should be rapidly corrected by providing adequate ventilation with protection of the vertebral column at all times. In a patent airway, respiratory collapse could be the result of an upper cervical SCI due to paralysis of the diaphragm and accessory breathing muscles. Indications for definitive airway control by endotracheal intubation include apnea, inability to maintain oxygenation with face mask supplementation, and protection from aspiration. Circulation must also be addressed during the primary survey. Neurogenic shock due to SCI could result in diminished amplitude of the peripheral pulses in combination with bradycardia. If the femoral or carotid pulses are not palpable, cardiopulmonary resuscitation is required. If this is the case, the front of the shoulder pads can be opened to allow for chest compressions and/or defibrillation.86
Off-the-Field Management
The treatment of the various forms of cervical spine injury has been summarized by numerous authors and follows established guidelines.1 The initial caregivers of the spine-injured athlete must be aware of the potential for respiratory failure and hemodynamic instability, as well as associated lesions, such as head injuries, which may affect the timing and order of needed treatments. Because of these concerns, patients with acute neurologic deficit from SCIs usually are initially cared for in an intensive care environment. The neurologic deficits from SCI may be improved by the early administration of steroids, but this method is controversial.78 The early induction of hypothermia has also been anecdotally reported to be beneficial.
Spear tackling puts a group of athletes at high risk for cervical quadriplegic injury and has been considered a relative contraindication for participation in contact sports.81 Affected athletes have (1) developmental cervical canal stenosis, (2) persistent straightening or reversal of the normal cervical spine lordotic curve, (3) evidence of preexisting, posttraumatic radiographic abnormalities of the cervical spine, and (4) documentation of having previously used spear tackling techniques showing predisposal to injury from cervical spine axial energy forces. When a spine with a congenitally narrowed canal is straightened, impact at the top or crown of the helmet causes buckling of the neck because the movement of the head is momentarily stopped while the trunk continues to accelerate forward. This axial loading impact to the persistently straightened cervical spine, which occurs when athletes deliberately engage in frequent head impact, can result in permanent SCI. Occasionally, if no significant bone or ligamentous instability is present, cervical lordosis may be restored through physiotherapy. If the player can be coached against using head vertex impact, a return to competition may be allowed. Otherwise, these individuals should be withheld from participation in contact sports.
Section Four
Lumbosacral Spine
Most population-based surveys of back pain report a point prevalence of 15% to 30%, a 1-year prevalence of 50%, and a lifetime prevalence of 60% to 80%.89 Given these numbers, it is not surprising that issues with the lumbosacral portion of the spine are fairly frequent in sports. An incidence of 7% has been reported in college athletes, and approximately 30% of college football players miss games due to lumbar spine problems.90 These injuries become more common as the level of play increases; the majority are simple lumbar strains. Most of these injuries are the result of direct contact causing a significant axial load or repeated hyperextension activities. Fortunately, most are minor and resolve spontaneously or with minimal intervention. This section deals with lumbosacral pathology in athletes, including diagnosis and surgical management. Simple strain, sprain, and contusion management were detailed in the cervical spine discussion.
Disc Herniation
Although lumbar discogenic disease is relatively uncommon in the younger population, its incidence increases with involvement in sporting activity.22 Pain can be axial mechanical, radicular, or both, and injuries range from anular tears to herniation with nerve root compression. Disc herniation in athletes is a consequence of numerous microtraumas to the intervertebral disc, which are further compounded by chronic overstraining. Although symptoms of other common injuries can resemble disc disease or damage, some mimickers are unusual. For example, a fracture of the lumbar lamina with epidural hematoma simulating herniation of a disc has been reported.91
Facet Syndrome
Damage or inflammation of the facet joints can often result in recurrent axial mechanical pain that worsens during participation. Pain from this source is greatest with hyperextension or twisting of the spine and may be unilateral. It is commonly observed in basketball players and is often associated with disc disease or injury.92 Management is similar to that discussed in the section on cervical facet injury.
Pars Interarticularis Injury
The majority of sporting activities involve rapid changes in direction and explosive movements. A spectrum of injuries, ranging from stress fractures to complete spondylolysis and pars interarticularis defect, may result from such movements. The younger athlete is more prone to these injuries since this small bony connection is not yet fully developed in early adolescence. Because athletes in this population is also beginning a rapid growth phase, they are also more vulnerable to some of the more significant complications of spondylolysis, such as vertebral slippage and spondylolisthesis.93,94 Even without the development of deformities or instability, pars defects can result in chronic back pain.95
Early detection in the adolescent is critical to arresting and possibly reversing damage. If not corrected, spinal stenosis and narrowing of the foramen can result in chronic lower back pain, radiculopathy, and symptoms of neurogenic claudication. Patients with spondylolysis or spondylolisthesis with less than 50% slippage can be treated with rest, but more severe injuries often require bracing of the lumbosacral spine or surgical fusion.96–98
Impending Spondylolysis or Impending Pars Defect
Ideally, stress fractures of the pars interarticularis can be discovered and treated before a frank bony separation occurs. This stage of injury is referred to as an impending spondylolysis, spondylolysis in the developmental stage, pars stress fracture, or impending pars defect. The first sign of such an injury is constant axial mechanical lower lumbar pain in an adolescent athlete that worsens with activity. Point tenderness is often evident at the lumbosacral junction, particularly over the L5 vertebra.99
Traditional bone-imaging modalities such as plain radiographs or CT scans are of limited value since no bone displacement has yet occurred, yet several other tests may give objective evidence of this condition.100,101
Nuclear scanning tests such as a bone scan can reveal bone inflammation indicative of an impending pars defect. Single-photon emission computed tomography (SPECT) can also aid in the diagnosis of an impending pars defect. It is similar to conventional nuclear medicine planar imaging but can provide true three-dimensional information typically presented as cross-sectional slices. The disadvantages to these modalities are the radiation exposure required and their fairly nonspecific results. For example, SPECT cannot distinguish between a pars stress fracture and other causes of increased activity in the pars such as arthritis, osteoid osteoma, or infection. Since these conditions are uncommon in the population that would be evaluated for an impending pars defect, this becomes less of a factor.102,103
In most cases, athletes, especially in their adolescence, with greater than 3 weeks of axial mechanical back pain and no structural abnormalities evident on normal plain radiographs of the lumbar spine (including oblique views) should be evaluated by MRI. If this testing is negative and a high degree of suspicion remains, nuclear imaging modalities may be employed. Once an impending pars interarticularis defect has been discovered, the treatment goals are the relief of pain, prevention of spondylolysis and spondylolisthesis, and eventual return to unrestricted activity. These goals are met by withholding the athlete from participation and practice involving any strenuous activity and possibly bracing. To our knowledge, there is no evidence that bracing has any benefit in healing versus simply restricting activity. Bracing may play a more important role in the noncompliant athlete who will not adhere to activity restrictions. Bone healing generally occurs after 6 to 12 weeks, and the athlete can gradually be reintroduced to activity when pain free. Numerous studies have demonstrated that the early recognition and treatment of an impending pars interarticularis defect is up to 80% successful in preventing progression.103–105
Spondylolysis and Spondylolisthesis
Spondylolysis is a defect of the pars interarticularis, typically resulting from repetitive extension activities. It accounts for a much larger percentage of lumbar spine injuries in adolescent athletes than in adults. Pars defects are more common in athletes involved in activities that involve repetitive hyperextension and axial loading. It is present in more than 10% of college football players and gymnasts, in contrast to an incidence of less than 3% in the general population. In American football, participants playing on the line are the most at risk, again because of the repetitive axial loading and extension involved in the position.106,107 Because an actual bony defect is present, these injuries are easily identified using plain lumbar radiographs including obliques or CT imaging.
Surgical management for pars defects with no associated spondylolisthesis is considered when the patient continues to have disabling pain refractory to conservative therapy. Numerous methods of fixation have been described, including dorsal wiring of the transverse process and spinous processes (Scott wiring), translaminar interfragmentary screws (Buck technique), and various pedicle screw to hook constructs within the same vertebra. The prognosis for return to competition is excellent after surgery. In a retrospective case series of four competitive athletes who underwent direct pars repair for symptomatic spondylolysis, all returned to presymptomatic levels of activity.108 A separate study of 22 similarly treated athletes (13 professional footballers, 4 professional cricketers, 3 hockey players, 1 tennis player, and 1 golfer) also demonstrated the strong likelihood of return to play.109
Cantu R.C. Cervical spine injuries in the athlete. Semin Neurol. 2000;20:173-178.
Torg J.S., Corcoran T.A., Thibault L.E., et al. Cervical cord neurapraxia: classification, pathomechanics, morbidity, and management guidelines. J Neurosurg. 1997;87:843-850.
Vaccaro A.R., Klein G.R., Ciccoti M., et al. Return to play criteria for the athlete with cervical spine injuries resulting in stinger and transient quadriplegia/paresis. Spine J. 2002;2:351-356.
Zmurko M.G., Tannoury T.Y., Tannoury C.A., Anderson D.G. Cervical sprains, disc herniations, minor fractures, and other cervical injuries in the athlete. Clin Sports Med. 2003;22:513-521.
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