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ATHLETIC SPINAL CORD AND SPINE INJURIES
NEUROLOGIC ATHLETIC HEAD AND NECK INJURIES
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ATHLETIC SPINAL CORD AND SPINE INJURIES Guidelines for Initial Management Jack E. Wilberger, Jr, MD
Spine injuries, unfortunately, occur frequently in the context of athletic participation and competition. Fortunately, most are minor injuries requiring short-term medical treatment and vigilance. However, some injuries damage the spine in such a fashion that questions must be raised about potential risks to the athlete from continued involvement in sports, and on rare occasions, a spine injury is associated with transient or permanent neurologic impairments.l0. When permanent neurologic sequelae occur, immediate and longterm medical management and recommendations are clear and, for the most part, noncontroversial. However, with virtually every other spine injury, although initial management is generally agreed on, subsequent recommendations can be widely divergent. The relatively infrequent occurrence of these injuries has resulted in a general lack of scientific evidence on which to base recommendations giving latitude to various sports medicine specialists developing their own guidelines, which perhaps may be clinically valid but may not be applicable to every situation encountered. This article briefly covers the athlete who suffers a spinal cord injury in competition while focusing on initial management.
From the Division of Neurosurgery, and the Department of Neurotrauma, Hahnemann, MCP School of Medicine, Allegheny University of the Health Sciences, Allegheny Campus, Pittsburgh, Pennsylvania
CLINICS IN SPORTS MEDICINE VOLUME 17 NUMBER 1 * JANUARY 1998
111
112
WILBERGER
SPINAL CORD INJURY
Spinal cord injury is fortunately a rare occurrence in organized athletics and usually occurs because of a freak accident. There are, however, several sports in which certain techniques or activities have come to be considered serious risk factors for spinal cord injury. An "epidemic" of spinal cord injury in football in the 1970s led to the identification of the technique of spearing-tackling with the crown of the helmet-as being responsible in a number of cases.l, 6 , 15, l9 Spearing puts the neck in the most vulnerable position possible for a compression flexion injury of the cervical spine and a potential spine/spinal cord injury (Fig. 1). Identifying this resultant problem provided the primary impetus for the 1976 NCAA football rule changes, which were intended to abolish the use of the head as an offense weapon. In ice hockey, boarding-the defensive maneuver of driving a player in the boards head first-was similarly identified as being high risk for spinal cord injury and is now associated with heavy penalties.12,l3 The overall incidence of spinal cord injury is 4:100,000 population per year in the United States of which approximately 5% to 10% is due to sports or recreational activity. Organized football is associated with a rate of 1.87:100,000 players per year, whereas ice hockey has an occur-
Figure 1. Typical pathomechanics of athletic spinal injury-vertex (Courtesy of Scott Williams)
compression/flexion.
ATHLETIC SPINAL CORD AND SPINE INJURIES
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rence of 0.84: 100,000 players per year.3,15,17 However, any sport may be associated with a risk of spinal cord injury (Fig. 2). In the past 10 years, 465 equestrian-related spinal cord injuries, 325 gymnastics-associated spinal cord injuries, and 25 race car driving spinal cord injuries have been reported. The immediate management of the spinal cord-injured athlete is no different from the management of a spinal cord injury encountered in any other situation. The airway must be established and protected, breathing maintained or supported, and circulation ensured. Clinical recognition of the spinal cord injury is of paramount importance. The possibility of such a serious injury must be considered whenever the athlete complains of severe pain anywhere over the spine or of any numbness, tingling, or weakness, however transient, in either the arms or the legs. The entity of burning hands syndrome should be quite familiar to anyone involved in the care of injured athletes. First elucidated by Maroon in 19779 and refined by Wilberger in 1987,2l the syndrome is now recognized as a variant of a central spinal cord injury. The characteristic complaint is of burning paresthesias and dysesthesias in both arms or hands and occasionally in the legs; weakness does not necessarily occur. Burning hands syndrome has been associated with a bony or ligamentous spine injury in approximately 50% of affected individuals. Thus, any athlete with this syndrome should be treated as having a significant spinal cord injury until proven otherwise. Significant concerns may arise over the management of spinal cord injuries in that the venue of the athletic event may be far from available
Figure 2. CT of a severe burst/compression fracture of a golfer injured when his golf cart overturned.
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WILBERGER
emergency medical care. Therefore, it is incumbent on the coach and trainer to have definite plans formulated and appropriate medical support for each contest in the event of a serious injury. In those sports using face protection, the helmet should not be removed unless protection of the airway takes priority. When the helmet is removed, the neck should be kept in as neutral a position as possible. Removal of the athlete from the site of injury should be done only after full spinal immobilization, which requires the use of a backboard. In placing the athlete on the backboard, the spine must be kept in as neutral a position as possible. The neck is immobilized by either a hard collar (unless not possible because of a helmet), and the side of the head secured to the backboard by sandbags or bolsters supported by taping. If a player is wearing a helmet, care must be taken to ensure that the cervical spine is still in a neutral position when the head is secured to the backboard because the helmet may inadvertently force the neck into some degree of flexion. Unfortunately, the degree of return of neurologic function lost after spinal cord injury is often not significant. Therefore, great care must be taken on site to maximize the opportunity for recovery. Prevention of further injury to the spine by proper immobilization is the first step. Ensuring adequate oxygenation and blood pressure is likewise important. Finally, if available, methylprednisolone at a dose of 30 mg/kg given shortly after injury may improve neurologic outcome. Despite the cause of the spinal cord injury, the ultimate stability of the spine with or without surgical intervention and the degree and extent of neurologic recovery, it is not recommended that the athlete be allowed to return to any collision or contact sport after a significant spinal cord injury.
NEURAPRAXIA AND CERVICAL STENOSIS
On occasion, as a result of contact or collision, an athlete may suffer transient neurologic deficits up to and including complete paralysis with immediate or rapid recovery to normal and no identified spine or spinal cord injury.8 Some of these individuals will, however, show developmental or degeneratively narrow spinal canals. It is a point of considerable controversy, however, if cervical stenosis predisposes to these transient events or whether there is an increased risk of permanent neurologic deficits and once the problem has been identified, whether restriction in athletic participation is appr~priate.~ To further the controversy, there is an ongoing debate over what constitutes a narrow spinal canal. General consensus has been that a bony spinal canal exceeding 15 mm is normal and abnormal if below 13 mm.4,22The advent of MR imaging, however, has brought forth the concept that the absolute width of the spinal canal is not as important as the space available to the spinal cord-functional spinal stenosis. Functional spinal stenosis exists when
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there is loss of a normal cerebrospinal fluid cushion around the cord or clear deformation of the cord (Fig. 3). Even with this definition, however, caution should be used because most MR images are done in the neutral position. With hyperextension, the spinal canal diameter may be compromised by as much as 30% by infolding of the interlaminar ligaments. In a recent study using MR imaging, functional cervical stenosis was found in 6 of 11 athletes rendered quadriplegic.2 Torg,14 among others, has attempted to establish a relationship between cervical stenosis and the incidence of neurapraxia, as well as its propensity to recur or lead to permanent neurologic sequelae. Torg recently reported a study involving over 400 high school, college, or professional football players, 324 of whom had no known history of neurapraxia; 45 had at least one episode; and 77 individuals were made quadriplegic from athletic incidents. Ninety-three percent of those suffering transient deficits had spinal stenosis by Torg’s criteria; however, none of those reporting episodes of neurapraxia became quadriplegic from subsequent incidents, and none of those who became quadriplegic had reported any prior episodes of neurapraxia. Torg’s conclusions were that spinal stenosis is ”neither a harbinger nor a predisposing factor for permanent neurologic injury.”16 Torg’s ratio method of defining spinal stenosis appears to accurately diagnose the condition only 12% of the time. Additionally, Torg has retrospectively reviewed 110 cases of cervical neurapraxia using MR imaging scan to measure spinal cord and spinal
Figure 3. MR image showing loss of functional reserve (arrow).
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WILBERGER
canal diameters. In this study, he found no clear relationship between the various clinical manifestations and the radiologic findings. Of his cohorts, 65% returned to contact/collision sports, and over half of these had at least one further episode of neurapraxia. The only consistent finding was that most patients who suffered recurrences have less space available for the cord within the spinal canal than those without recurrence^.'^,
l7
When faced with an athlete who has suffered a transient neurologic deficit or neurapraxia, a thorough workup must be accomplished to rule out bony and ligamentous injury to the spine. Plain cervical spine films with flexion and extension views are the starting point. If any bony abnormality is seen, CT is useful in evaluating for subtle bony injuries. If no bony or ligamentous abnormalities are identified, it is important to rule out ongoing extrinsic cord or nerve root compression or intrinsic cord abnormalities. This is most readily accomplished by MR imaging. Any intrinsic cord abnormalities seen on MR imaging are clear evidence of an overt, albeit mild, spinal cord injury and should preclude a return to sports. If the MR image shows evidence of loss of functional reserve or significant cord deformation, careful individual consideration must be given to recommendations for return to sports activity. Available information would suggest that such a situation leads to a significant risk for recurrent episodes of neurapraxia, and to permanent neurologic deficits should the athlete suffer another injury. A second episode of transient neurologic deficit should initiate another complete workup as previously described. If all the studies remain normal, a return to competition need not be precluded; however, concern should be raised about the recurrent nature of the problem and consideration given to limiting further athletic activity.
SPEAR TACKLER’S SPINE The entity of spear tackler’s spine was originally described in 1993 after careful evaluation of data from the National Football Head and Neck Injury Registry.l8 Permanent neurologic injury occurred in four athletes who were identified as having the following characteristic combination of abnormalities on plain cervical spine films: (1)developmental narrowing of the cervical spinal canal; (2) straightening or reversal of the normal cervical lordotic curve; and (3) preexisting minor post-traumatic radiographic evidence of bony or ligamentous injury (Fig. 4). In addition to these radiographic criteria, all of these players were documented as having used spear-tackling techniques. The existence of a spear tackler’s spine in some authors’ opinions absolutely prohibits the return to contact/collision sports, even if the abnormality is an incidental finding because of minor complaints or symptoms. Other experts believe that although concerns should be
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Figure 4. Characteristic radiographic findings of the spear tackler’s spine.
raised, if the normal cervical lordosis is restored by treatment and the athlete refrains from any further spear-tackling techniques, then there is not a high degree of risk for injury from allowing return to athletic activity. SPRAIN/STRAIN-LIGAMENTOUSINJURY
Most cervical injuries will involve a ligament sprain, muscle strain, or contusion. With such injuries, there is no neurologic or osseous injury and return to competition can occur when the athlete is free of neck pain with and without axial compression, when range of motion is full, and when the strength of the neck is normal. Cervical radiographs should show no subluxation or abnormal curvatures. It is preferable that the athlete not return to competition until they are asymptomatic and can perform at the level of their pre-injury abilities. It is well known that ligament damage may accompany a cervical spine injury and can occur in the absence of bony injury. Generally, this is minor and self-limited, but on occasion, it may result in progressive instability, cervical spine deformity, and spinal cord injury. There are guidelines to assist in determining ligament stability. Under normal circumstances, conditions permit very little motion between the cervical
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vertebrae. In cadaver studies with all ligaments intact, horizontal movement of one vertebral body on the next does not exceed 3.5 mm and the angular displacement of one vertebral body on the next is always 11 degrees or less. Only when most of the restraining ligaments are injured or destroyed do motions in excess of this occur. In the clinical setting, measurements of the horizontal or angular displacement can be made on neutral or flexion/extension radiographs. It is important, however, to remember that the younger the athlete, the more likely there is to be ligamentous laxity and the preceding criteria may not always be applicable.20 Incipient, severe ligamentous injury in the acutely injured athlete may not be recognized because a normal degree of spinal ligamentous laxity in younger patients is generally accepted, and cervical muscle spasms, which may compensate for ligamentous instability, may be present. For these reasons, when any subluxation is seen after a sportsrelated injury, the patient should wear a hard cervical collar and flexion/ extension films of the cervical spine should be repeated 2 to 4 weeks after injury. If the films show no evidence of progression or if there is a return to normal, it is unlikely that any significant injury has occurred and the athlete can most likely return safely to his or her competitive sport. SERIOUS SPINE INJURY
For athletes who have suffered an unstable fracture or fracture dislocation of the cervical spine without spinal cord injury and who have undergone spinal fusion, a return to any sport involving risk of further spine injury raises strong concerns. Even in the presence of an apparently stable spine, as seen on flexion/extension radiographs, and a normal-sized spinal canal, continued participation may not be advisable. Currently, there are no experimental or clinical data to help physicians predict the stability of healed spinal fractures or fusions when they are placed under extreme degrees of mechanical stress. There is increased mechanical stress above and below fused spinal segments and repetitive microtrauma to a stiff spine exacerbates the stress. Torg and coworker^'^ estimated that the forces involved in a football tackle may approach 18 g. Some attempt has been made to assess spinal strength following spinal injury with a Cybex dynamometer. The Cybex has been particularly useful in assessing muscle strength, power, and endurance, but its applicability to the spine is yet to be determined. In fact, there is no evidence that the injured cervical spine is made stronger than normal by fusion. Thus, in the absence of any objective ability to measure the degree of dynamic stress stability of the spine, any healed fracture (with the exception of chip, minor wedge/compression, isolated laminar, or spinous process fractures), and any injury that has required internal stabilization is highly suspect in its ability to withstand further challenges from contact/collision sports.
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MINOR SPINE INJURY
As noted in the discussion on serious spine injury, there are no definite data that fully assess spinal stress tolerance after injury. The fact that many athletes have evidence of old osseous injury on radiographs does, however, indeed indicate that they may be able to withstand repeated stress without evidence of long-term symptoms or in~tability.~ Thus, isolated wedge fractures and chip fractures of the vertebral body in the absence of subluxation, laminar fracture, and spinous process fracture would seem to pose no long-term problem once adequate healing has occurred. However, there may be an exception to this general rule if the entity of spear tackler’s spine exists or if there is greater than 11 degrees of angular deformity of the end plate of the vertebral body fracture compared with the adjoining normal vertebrae. White and coworkersz0suggested that such a degree of deformity may predispose one to chronic instability. When such an injury occurs, the athlete should discontinue all contact and competitive sports for at least 3 to 6 months. If the athlete is asymptomatic and if dynamic films show fracture healing without evidence of instability, the return to competition is unlikely to be associated with a significant risk of further injury.
CONCLUSION
Careful study of the pathomechanics and epidemiology of sportsrelated spine injuries has led to a general understanding of the risk factors for their occurrence or recurrence. With the exception of spinal cord injury, however, and perhaps, the existence of a spear tackler’s spine, no absolute guidelines can be devised with respect to return to full athletic competition. Although considerable pressure may be exerted by coaches, families, or even the player himself or herself, the physician’s primary obligation is to the athlete considering his or her spine and spinal cord integrity and what is known based on the guidelines provided in this article. Ultimately, however, the decision to return to competitive sports must be individualized taking into account all factors impacting the athlete in question.
References 1. Burstein AW, Otis JC, Torg J S Mechanisms and pathogenesis of athletic injuries to the cervical spine. In Torg JS (ed): Athletic Injuries to the Head, Neck, and Face. Malvem, PA, Lea & Febiger, 1982, pp 119-149 2. Cantu RC: Functional cervical spinal stenosis: A contraindication to participation in contact sports. Med Sci Sports Exerc 25:46-52, 1993 3. Cantu RC: Head and spine injuries in the young athlete. In Micheli LJ (ed): Injuries in the Young Athlete. Philadelphia, WB Saunders, 1988, pp 459472
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4. Eismont FJ, Clifford S, Goldberg M, et al: Cervical sagittal spinal canal size in spine injuries. Spine 9:663-666, 1984 5. Firoozina H, Ahn J, Rafii M, et al: Sudden quadriplegia after a minor trauma: The role of preexisting spinal stenosis. Surg Neurol 23:165-168, 1985 6. Funk FJ, Wells RE: Injuries of the cervical spine in football. Clin Orthop 109:50-58, 1975 7. Herzog RJ, Weins JJ, Dillingham MF, et al: Normal cervical spine morphometry and cervical spinal stenosis in asymptomatic professional football players. Spine 16:178186, 1991 8. Ladd AL, Scranton PE: Congenital cervical stenosis presenting as transient quadriplegia in athletes. J Bone Joint Surg 68:1371-1374, 1986 9. Maroon JC: Burning hands and football spinal cord injury. JAMA 238:2049-2051, 1977 10. Micheli LJ: Sports following spinal surgery in the young athlete. Clin Orthop 198:152157, 1985 11. Schneider RS, Reifel E, Grisler H, et al: Serious and fatal football injuries involving the head and spinal cord. JAMA 177362-367, 1961 12. Tator CH, Edmonds VE, Duncan EG: Catastrophic sports and recreational injuries in Ontario: Causes and prevention. Washington, DC, American Association Neurologic Surgeons Annual Meeting, 1989 13. Tator CH, Edmonds VE: National survey of spinal injuries in hockey players. Can Med Assoc J 1302375-880, 1984 14. Torg JS, Naranja J, Pavlov H, et al: The relationship of developmental narrowing of the cervical spinal canal to reversible and irreversible injury to the cervical spinal cord in football players. J Bone Joint Surg 78A:1308-1314, 1996 15. Torg JS: Epidemiology, pathomechanics, and prevention of athletic injuries to the cervical spine. Med Sci Sports Exerc 17295-303, 1985 16. Torg JS, Pavolv H, Genuario SE, et al: Neurapraxia of the cervical spinal cord with transient quadriplegia. J Bone Joint Surg 68:1354-1370, 1988 17. Torg JS, Ramsey-Emrhein JA: Management guidelines for participation in collision activities with congenital, developmental, or post-injury lesions involving the cervical spine. Med Sci Sports Exerc (in press) 18. Torg JS, Sennett B, Pavlov H, et al: Spear tackler’s spine: An entity precluding participation in tackle football and collision activities that expose the cervical spine to axial injury inputs. Am J Sports Med 21:640-649, 1993 19. Torg JS, Vegso JJ, Sennett B, et al: The National Football Injury Registry: 14-year report of cervical quadriplegia, 1971-1984. JAMA 2543439-3443, 1985 20. White AA, Johnson RM, Pangabi MM, et al: Biomechanical analysis of clinical stability in the cervical spine. Clin Orthop 109:85-89, 1975 21. Wilberger JE: Burning hands syndrome revisited. Neurosurgery 20:599-605, 1987 22. Yu YL, Stevens JM, Kendal 8,et al: Cord shape and measurements in cervical spondylitic myelopathy and radiculopathy. Am J Neuroradiol 423394342, 1983
Address reprint requests to Jack E. Wilberger, Jr, MD Division of Neurosurgery Allegheny General Hospital 420 East North Avenue Suite 302 Pittsburgh, PA 152124746
0278-5919/98 $8.00
+ .oo
ATHLETIC SPINAL CORD AND SPINE INJURIES Guidelines for Initial Management Jack E. Wilberger, Jr, MD
Spine injuries, unfortunately, occur frequently in the context of athletic participation and competition. Fortunately, most are minor injuries requiring short-term medical treatment and vigilance. However, some injuries damage the spine in such a fashion that questions must be raised about potential risks to the athlete from continued involvement in sports, and on rare occasions, a spine injury is associated with transient or permanent neurologic impairments.l0. When permanent neurologic sequelae occur, immediate and longterm medical management and recommendations are clear and, for the most part, noncontroversial. However, with virtually every other spine injury, although initial management is generally agreed on, subsequent recommendations can be widely divergent. The relatively infrequent occurrence of these injuries has resulted in a general lack of scientific evidence on which to base recommendations giving latitude to various sports medicine specialists developing their own guidelines, which perhaps may be clinically valid but may not be applicable to every situation encountered. This article briefly covers the athlete who suffers a spinal cord injury in competition while focusing on initial management.
From the Division of Neurosurgery, and the Department of Neurotrauma, Hahnemann, MCP School of Medicine, Allegheny University of the Health Sciences, Allegheny Campus, Pittsburgh, Pennsylvania
CLINICS IN SPORTS MEDICINE VOLUME 17 NUMBER 1 * JANUARY 1998
111
112
WILBERGER
SPINAL CORD INJURY
Spinal cord injury is fortunately a rare occurrence in organized athletics and usually occurs because of a freak accident. There are, however, several sports in which certain techniques or activities have come to be considered serious risk factors for spinal cord injury. An "epidemic" of spinal cord injury in football in the 1970s led to the identification of the technique of spearing-tackling with the crown of the helmet-as being responsible in a number of cases.l, 6 , 15, l9 Spearing puts the neck in the most vulnerable position possible for a compression flexion injury of the cervical spine and a potential spine/spinal cord injury (Fig. 1). Identifying this resultant problem provided the primary impetus for the 1976 NCAA football rule changes, which were intended to abolish the use of the head as an offense weapon. In ice hockey, boarding-the defensive maneuver of driving a player in the boards head first-was similarly identified as being high risk for spinal cord injury and is now associated with heavy penalties.12,l3 The overall incidence of spinal cord injury is 4:100,000 population per year in the United States of which approximately 5% to 10% is due to sports or recreational activity. Organized football is associated with a rate of 1.87:100,000 players per year, whereas ice hockey has an occur-
Figure 1. Typical pathomechanics of athletic spinal injury-vertex (Courtesy of Scott Williams)
compression/flexion.
ATHLETIC SPINAL CORD AND SPINE INJURIES
113
rence of 0.84: 100,000 players per year.3,15,17 However, any sport may be associated with a risk of spinal cord injury (Fig. 2). In the past 10 years, 465 equestrian-related spinal cord injuries, 325 gymnastics-associated spinal cord injuries, and 25 race car driving spinal cord injuries have been reported. The immediate management of the spinal cord-injured athlete is no different from the management of a spinal cord injury encountered in any other situation. The airway must be established and protected, breathing maintained or supported, and circulation ensured. Clinical recognition of the spinal cord injury is of paramount importance. The possibility of such a serious injury must be considered whenever the athlete complains of severe pain anywhere over the spine or of any numbness, tingling, or weakness, however transient, in either the arms or the legs. The entity of burning hands syndrome should be quite familiar to anyone involved in the care of injured athletes. First elucidated by Maroon in 19779 and refined by Wilberger in 1987,2l the syndrome is now recognized as a variant of a central spinal cord injury. The characteristic complaint is of burning paresthesias and dysesthesias in both arms or hands and occasionally in the legs; weakness does not necessarily occur. Burning hands syndrome has been associated with a bony or ligamentous spine injury in approximately 50% of affected individuals. Thus, any athlete with this syndrome should be treated as having a significant spinal cord injury until proven otherwise. Significant concerns may arise over the management of spinal cord injuries in that the venue of the athletic event may be far from available
Figure 2. CT of a severe burst/compression fracture of a golfer injured when his golf cart overturned.
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WILBERGER
emergency medical care. Therefore, it is incumbent on the coach and trainer to have definite plans formulated and appropriate medical support for each contest in the event of a serious injury. In those sports using face protection, the helmet should not be removed unless protection of the airway takes priority. When the helmet is removed, the neck should be kept in as neutral a position as possible. Removal of the athlete from the site of injury should be done only after full spinal immobilization, which requires the use of a backboard. In placing the athlete on the backboard, the spine must be kept in as neutral a position as possible. The neck is immobilized by either a hard collar (unless not possible because of a helmet), and the side of the head secured to the backboard by sandbags or bolsters supported by taping. If a player is wearing a helmet, care must be taken to ensure that the cervical spine is still in a neutral position when the head is secured to the backboard because the helmet may inadvertently force the neck into some degree of flexion. Unfortunately, the degree of return of neurologic function lost after spinal cord injury is often not significant. Therefore, great care must be taken on site to maximize the opportunity for recovery. Prevention of further injury to the spine by proper immobilization is the first step. Ensuring adequate oxygenation and blood pressure is likewise important. Finally, if available, methylprednisolone at a dose of 30 mg/kg given shortly after injury may improve neurologic outcome. Despite the cause of the spinal cord injury, the ultimate stability of the spine with or without surgical intervention and the degree and extent of neurologic recovery, it is not recommended that the athlete be allowed to return to any collision or contact sport after a significant spinal cord injury.
NEURAPRAXIA AND CERVICAL STENOSIS
On occasion, as a result of contact or collision, an athlete may suffer transient neurologic deficits up to and including complete paralysis with immediate or rapid recovery to normal and no identified spine or spinal cord injury.8 Some of these individuals will, however, show developmental or degeneratively narrow spinal canals. It is a point of considerable controversy, however, if cervical stenosis predisposes to these transient events or whether there is an increased risk of permanent neurologic deficits and once the problem has been identified, whether restriction in athletic participation is appr~priate.~ To further the controversy, there is an ongoing debate over what constitutes a narrow spinal canal. General consensus has been that a bony spinal canal exceeding 15 mm is normal and abnormal if below 13 mm.4,22The advent of MR imaging, however, has brought forth the concept that the absolute width of the spinal canal is not as important as the space available to the spinal cord-functional spinal stenosis. Functional spinal stenosis exists when
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there is loss of a normal cerebrospinal fluid cushion around the cord or clear deformation of the cord (Fig. 3). Even with this definition, however, caution should be used because most MR images are done in the neutral position. With hyperextension, the spinal canal diameter may be compromised by as much as 30% by infolding of the interlaminar ligaments. In a recent study using MR imaging, functional cervical stenosis was found in 6 of 11 athletes rendered quadriplegic.2 Torg,14 among others, has attempted to establish a relationship between cervical stenosis and the incidence of neurapraxia, as well as its propensity to recur or lead to permanent neurologic sequelae. Torg recently reported a study involving over 400 high school, college, or professional football players, 324 of whom had no known history of neurapraxia; 45 had at least one episode; and 77 individuals were made quadriplegic from athletic incidents. Ninety-three percent of those suffering transient deficits had spinal stenosis by Torg’s criteria; however, none of those reporting episodes of neurapraxia became quadriplegic from subsequent incidents, and none of those who became quadriplegic had reported any prior episodes of neurapraxia. Torg’s conclusions were that spinal stenosis is ”neither a harbinger nor a predisposing factor for permanent neurologic injury.”16 Torg’s ratio method of defining spinal stenosis appears to accurately diagnose the condition only 12% of the time. Additionally, Torg has retrospectively reviewed 110 cases of cervical neurapraxia using MR imaging scan to measure spinal cord and spinal
Figure 3. MR image showing loss of functional reserve (arrow).
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WILBERGER
canal diameters. In this study, he found no clear relationship between the various clinical manifestations and the radiologic findings. Of his cohorts, 65% returned to contact/collision sports, and over half of these had at least one further episode of neurapraxia. The only consistent finding was that most patients who suffered recurrences have less space available for the cord within the spinal canal than those without recurrence^.'^,
l7
When faced with an athlete who has suffered a transient neurologic deficit or neurapraxia, a thorough workup must be accomplished to rule out bony and ligamentous injury to the spine. Plain cervical spine films with flexion and extension views are the starting point. If any bony abnormality is seen, CT is useful in evaluating for subtle bony injuries. If no bony or ligamentous abnormalities are identified, it is important to rule out ongoing extrinsic cord or nerve root compression or intrinsic cord abnormalities. This is most readily accomplished by MR imaging. Any intrinsic cord abnormalities seen on MR imaging are clear evidence of an overt, albeit mild, spinal cord injury and should preclude a return to sports. If the MR image shows evidence of loss of functional reserve or significant cord deformation, careful individual consideration must be given to recommendations for return to sports activity. Available information would suggest that such a situation leads to a significant risk for recurrent episodes of neurapraxia, and to permanent neurologic deficits should the athlete suffer another injury. A second episode of transient neurologic deficit should initiate another complete workup as previously described. If all the studies remain normal, a return to competition need not be precluded; however, concern should be raised about the recurrent nature of the problem and consideration given to limiting further athletic activity.
SPEAR TACKLER’S SPINE The entity of spear tackler’s spine was originally described in 1993 after careful evaluation of data from the National Football Head and Neck Injury Registry.l8 Permanent neurologic injury occurred in four athletes who were identified as having the following characteristic combination of abnormalities on plain cervical spine films: (1)developmental narrowing of the cervical spinal canal; (2) straightening or reversal of the normal cervical lordotic curve; and (3) preexisting minor post-traumatic radiographic evidence of bony or ligamentous injury (Fig. 4). In addition to these radiographic criteria, all of these players were documented as having used spear-tackling techniques. The existence of a spear tackler’s spine in some authors’ opinions absolutely prohibits the return to contact/collision sports, even if the abnormality is an incidental finding because of minor complaints or symptoms. Other experts believe that although concerns should be
ATHLETIC SPINAL CORD AND SPINE INJURIES
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Figure 4. Characteristic radiographic findings of the spear tackler’s spine.
raised, if the normal cervical lordosis is restored by treatment and the athlete refrains from any further spear-tackling techniques, then there is not a high degree of risk for injury from allowing return to athletic activity. SPRAIN/STRAIN-LIGAMENTOUSINJURY
Most cervical injuries will involve a ligament sprain, muscle strain, or contusion. With such injuries, there is no neurologic or osseous injury and return to competition can occur when the athlete is free of neck pain with and without axial compression, when range of motion is full, and when the strength of the neck is normal. Cervical radiographs should show no subluxation or abnormal curvatures. It is preferable that the athlete not return to competition until they are asymptomatic and can perform at the level of their pre-injury abilities. It is well known that ligament damage may accompany a cervical spine injury and can occur in the absence of bony injury. Generally, this is minor and self-limited, but on occasion, it may result in progressive instability, cervical spine deformity, and spinal cord injury. There are guidelines to assist in determining ligament stability. Under normal circumstances, conditions permit very little motion between the cervical
118
WILBERGER
vertebrae. In cadaver studies with all ligaments intact, horizontal movement of one vertebral body on the next does not exceed 3.5 mm and the angular displacement of one vertebral body on the next is always 11 degrees or less. Only when most of the restraining ligaments are injured or destroyed do motions in excess of this occur. In the clinical setting, measurements of the horizontal or angular displacement can be made on neutral or flexion/extension radiographs. It is important, however, to remember that the younger the athlete, the more likely there is to be ligamentous laxity and the preceding criteria may not always be applicable.20 Incipient, severe ligamentous injury in the acutely injured athlete may not be recognized because a normal degree of spinal ligamentous laxity in younger patients is generally accepted, and cervical muscle spasms, which may compensate for ligamentous instability, may be present. For these reasons, when any subluxation is seen after a sportsrelated injury, the patient should wear a hard cervical collar and flexion/ extension films of the cervical spine should be repeated 2 to 4 weeks after injury. If the films show no evidence of progression or if there is a return to normal, it is unlikely that any significant injury has occurred and the athlete can most likely return safely to his or her competitive sport. SERIOUS SPINE INJURY
For athletes who have suffered an unstable fracture or fracture dislocation of the cervical spine without spinal cord injury and who have undergone spinal fusion, a return to any sport involving risk of further spine injury raises strong concerns. Even in the presence of an apparently stable spine, as seen on flexion/extension radiographs, and a normal-sized spinal canal, continued participation may not be advisable. Currently, there are no experimental or clinical data to help physicians predict the stability of healed spinal fractures or fusions when they are placed under extreme degrees of mechanical stress. There is increased mechanical stress above and below fused spinal segments and repetitive microtrauma to a stiff spine exacerbates the stress. Torg and coworker^'^ estimated that the forces involved in a football tackle may approach 18 g. Some attempt has been made to assess spinal strength following spinal injury with a Cybex dynamometer. The Cybex has been particularly useful in assessing muscle strength, power, and endurance, but its applicability to the spine is yet to be determined. In fact, there is no evidence that the injured cervical spine is made stronger than normal by fusion. Thus, in the absence of any objective ability to measure the degree of dynamic stress stability of the spine, any healed fracture (with the exception of chip, minor wedge/compression, isolated laminar, or spinous process fractures), and any injury that has required internal stabilization is highly suspect in its ability to withstand further challenges from contact/collision sports.
ATHLETIC SPINAL CORD AND SPINE INJURIES
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MINOR SPINE INJURY
As noted in the discussion on serious spine injury, there are no definite data that fully assess spinal stress tolerance after injury. The fact that many athletes have evidence of old osseous injury on radiographs does, however, indeed indicate that they may be able to withstand repeated stress without evidence of long-term symptoms or in~tability.~ Thus, isolated wedge fractures and chip fractures of the vertebral body in the absence of subluxation, laminar fracture, and spinous process fracture would seem to pose no long-term problem once adequate healing has occurred. However, there may be an exception to this general rule if the entity of spear tackler’s spine exists or if there is greater than 11 degrees of angular deformity of the end plate of the vertebral body fracture compared with the adjoining normal vertebrae. White and coworkersz0suggested that such a degree of deformity may predispose one to chronic instability. When such an injury occurs, the athlete should discontinue all contact and competitive sports for at least 3 to 6 months. If the athlete is asymptomatic and if dynamic films show fracture healing without evidence of instability, the return to competition is unlikely to be associated with a significant risk of further injury.
CONCLUSION
Careful study of the pathomechanics and epidemiology of sportsrelated spine injuries has led to a general understanding of the risk factors for their occurrence or recurrence. With the exception of spinal cord injury, however, and perhaps, the existence of a spear tackler’s spine, no absolute guidelines can be devised with respect to return to full athletic competition. Although considerable pressure may be exerted by coaches, families, or even the player himself or herself, the physician’s primary obligation is to the athlete considering his or her spine and spinal cord integrity and what is known based on the guidelines provided in this article. Ultimately, however, the decision to return to competitive sports must be individualized taking into account all factors impacting the athlete in question.
References 1. Burstein AW, Otis JC, Torg J S Mechanisms and pathogenesis of athletic injuries to the cervical spine. In Torg JS (ed): Athletic Injuries to the Head, Neck, and Face. Malvem, PA, Lea & Febiger, 1982, pp 119-149 2. Cantu RC: Functional cervical spinal stenosis: A contraindication to participation in contact sports. Med Sci Sports Exerc 25:46-52, 1993 3. Cantu RC: Head and spine injuries in the young athlete. In Micheli LJ (ed): Injuries in the Young Athlete. Philadelphia, WB Saunders, 1988, pp 459472
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4. Eismont FJ, Clifford S, Goldberg M, et al: Cervical sagittal spinal canal size in spine injuries. Spine 9:663-666, 1984 5. Firoozina H, Ahn J, Rafii M, et al: Sudden quadriplegia after a minor trauma: The role of preexisting spinal stenosis. Surg Neurol 23:165-168, 1985 6. Funk FJ, Wells RE: Injuries of the cervical spine in football. Clin Orthop 109:50-58, 1975 7. Herzog RJ, Weins JJ, Dillingham MF, et al: Normal cervical spine morphometry and cervical spinal stenosis in asymptomatic professional football players. Spine 16:178186, 1991 8. Ladd AL, Scranton PE: Congenital cervical stenosis presenting as transient quadriplegia in athletes. J Bone Joint Surg 68:1371-1374, 1986 9. Maroon JC: Burning hands and football spinal cord injury. JAMA 238:2049-2051, 1977 10. Micheli LJ: Sports following spinal surgery in the young athlete. Clin Orthop 198:152157, 1985 11. Schneider RS, Reifel E, Grisler H, et al: Serious and fatal football injuries involving the head and spinal cord. JAMA 177362-367, 1961 12. Tator CH, Edmonds VE, Duncan EG: Catastrophic sports and recreational injuries in Ontario: Causes and prevention. Washington, DC, American Association Neurologic Surgeons Annual Meeting, 1989 13. Tator CH, Edmonds VE: National survey of spinal injuries in hockey players. Can Med Assoc J 1302375-880, 1984 14. Torg JS, Naranja J, Pavlov H, et al: The relationship of developmental narrowing of the cervical spinal canal to reversible and irreversible injury to the cervical spinal cord in football players. J Bone Joint Surg 78A:1308-1314, 1996 15. Torg JS: Epidemiology, pathomechanics, and prevention of athletic injuries to the cervical spine. Med Sci Sports Exerc 17295-303, 1985 16. Torg JS, Pavolv H, Genuario SE, et al: Neurapraxia of the cervical spinal cord with transient quadriplegia. J Bone Joint Surg 68:1354-1370, 1988 17. Torg JS, Ramsey-Emrhein JA: Management guidelines for participation in collision activities with congenital, developmental, or post-injury lesions involving the cervical spine. Med Sci Sports Exerc (in press) 18. Torg JS, Sennett B, Pavlov H, et al: Spear tackler’s spine: An entity precluding participation in tackle football and collision activities that expose the cervical spine to axial injury inputs. Am J Sports Med 21:640-649, 1993 19. Torg JS, Vegso JJ, Sennett B, et al: The National Football Injury Registry: 14-year report of cervical quadriplegia, 1971-1984. JAMA 2543439-3443, 1985 20. White AA, Johnson RM, Pangabi MM, et al: Biomechanical analysis of clinical stability in the cervical spine. Clin Orthop 109:85-89, 1975 21. Wilberger JE: Burning hands syndrome revisited. Neurosurgery 20:599-605, 1987 22. Yu YL, Stevens JM, Kendal 8,et al: Cord shape and measurements in cervical spondylitic myelopathy and radiculopathy. Am J Neuroradiol 423394342, 1983
Address reprint requests to Jack E. Wilberger, Jr, MD Division of Neurosurgery Allegheny General Hospital 420 East North Avenue Suite 302 Pittsburgh, PA 152124746