Elite athletes are often faced with difficult decisions when faced with a cervical spinal disorder. There are many aspects to consider such as the risk of further injury, short- and long-term effects on an athlete’s life both during and after his/her career, and the options for treatment. Although there have been some recent contributions to this topic, the evidence-based literature is generally devoid of high-level clinical studies to help guide the decision-making process. This article reviews the pertinent available data/criteria and offer an algorithm for return-to-play considerations.
Key points
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Cervical spine injuries in the elite athlete present a unique conundrum for treatment, which depends on multiple factors including symptoms and type of sport played.
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Cervical stenosis is compatible with return-to-play even for collision sports as long as there is a minimum threshold of canal space and there are no significant clinical symptoms.
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Treatment and management of these conditions should be individualized based on athlete’s career trajectory, symptoms, and potential future risks.
Introduction
Approximately 12,500 new cases of spinal cord injury (SCI) occur in the United States alone per year with athletic participation accounting for 9%. Although American football has lower rates of SCI than other sports, it remains the leading cause due to its relatively larger nationwide participation rates. Hutton and colleagues recently estimated the rate of SCI in professional male Rugby Union players at approximately 4.1 per 100,000 player-hours with most of the injuries occurring during the collapse of the scrum, followed by making a tackle. A cross-sectional study by Torg and colleagues demonstrated that out of 355 spinal injuries suffered at any level by Canadian hockey players, 20.8% experienced cervical spine injuries without associated SCI, whereas 12.9% had associated SCI.
Sports-related neurologic injuries can range in severity from stingers to catastrophic permanent neurologic injury. Stingers/burners are defined as a type of brachial plexopathy manifesting as transient sensory and/or motor deficits in the ipsilateral upper extremity resulting from compression- or traction-type trauma. These injuries are differentiated from more severe spinal cord injuries by the unilateral nature of their symptoms, combined with painless active and passive neck range of motion (ROM). Even for these types of injuries, initial evaluation must rule out a more significant structural or SCI with formal work-up including cervical spine radiographs and MRI evaluation.
The incidence, management, and outcomes after major cervical spine injuries are of critical interest for athletes participating in collision sports. In particular, the management of athletes found to have cervical canal stenosis is a topic of considerable debate, with few definitive guidelines in place for such athletes’ return to active play. The identification of cervical canal stenosis in athletes often occurs through imaging, following an injury with symptoms of neck pain, radiculopathy, or SCI. This condition can also be diagnosed during routine screening imaging in asymptomatic individuals. There is significant controversy in predicting the risk of future injury in athletes found to have cervical canal stenosis who are otherwise completely asymptomatic. Despite the prevalence of these conditions, there do not exist any standardized consensus guidelines for return-to-play (RTP). Many of the pertinent treatises for treatment in this population are based on expert opinion only. The diagnosis, management, and decision-making process surrounding cervical spinal injuries can be complex and must incorporate many different considerations—both short-term and long-term. The authors believe that large-scale retrospective cohort, case series, and even case report studies can be incorporated with expert opinion to set forth guidelines to practitioners and players who are afflicted by cervical spinal injuries.
Transient quadriplegia
Transient quadriplegia is defined as a temporary loss of motor or sensory function in the arms and legs that can last from seconds to days following excessive compression, flexion, or extension injury of the cervical spine. , , The presence of preexisting cervical stenosis greatly reduces functional reserve, which can increase the incidence of these symptoms with hyperextension or axial compression forces. The severity of the episode also deserves consideration in the individualized RTP algorithm. The more severe and longer the duration of symptoms, the greater the ramifications and risk of neurologic sequelae with a repeat injury.
These types of injuries in athletes are primarily attributed to axial loading and hyperflexion mechanisms. When the cervical spine is straightened with slight neck flexion (ie, checking, tackling, spearing), an applied axial load with sufficient energy can result in angular deformation and buckling, causing structural failures such as subluxations, fractures, and facet dislocations. In adults, the subaxial spinal cord canal diameter from C4 to C7 is smaller than other regions, increasing the likelihood of SCI. Furthermore, stenosis associated with “spear-tackling” has been shown to narrow the spinal canal as much as 30%. , Regardless of the mechanism, the potential for spinal cord irritation exists with each of these types of mechanisms and must be given particular attention. In many cases of transient quadriplegia, all 4 extremities are involved. The duration of symptoms typically lasts less than 15 minutes and can require up to 48 hours for the resolution of all symptoms.
In a recent review, transient quadriplegia (n = 19 studies) occurred in 7.3 per 10,000 professional football players and was closely associated with the presence of congenital cervical stenosis, which puts the player at risk with extreme flexion and extension of the cervical spine. , , , , Historically, Torg and colleagues suggested RTP recommendations for NFL athletes based on 0.8 vertebral canal-to-body ratio on plain radiographs and presence of symptoms. However, in a computed tomography (CT)-based evaluation of 80 NFL athletes, Herzog and colleagues demonstrated that nearly 50% of asymptomatic players had abnormal canal-to-body ratios, despite having average spinal canal measurements on advanced imaging. These data challenge the specificity for the usage of this test in this patient population. More recent studies have identified the sagittal MRI as the most appropriate screening tool to diagnose cervical stenosis. , For example, the term “congenital cervical stenosis” has recently been specifically defined as a patient less than 50 years of age with midsagittal canal diameters of less than 10 mm at multiple subaxial cervical levels measured at the pedicle on MRI T2 imaging. Furthermore, Aebli and colleagues recently reported that a sagittal canal diameter of less than 8 mm may increase the risk of SCI with minor trauma to the neck. MRI evaluation can also lead to the qualitative diagnosis of stenosis, or “functional cervical spinal stenosis,” that grades severity by the loss of protective cerebrospinal fluid (CSF) around the spinal cord.
Cervical Cord Neuropraxia
Cervical cord neuropraxia (CCN), which is defined as the temporary cessation of spinal cord function after impact to the cervical region, is often the cause that leads to a transient quadriplegic episode. In counseling athletes presenting with prior reported incidents, it becomes important to discuss the risks of recurrence and permanent neurologic injury. One case series followed 110 patients who had a witnessed episode of CCN from a sports-related injury for an average follow-up of 40 ± 51 months. Most of these patients (86%) were found to have radiographic cervical cord stenosis (Torg-Pavlov <0.8) with an average ratio of 0.68. MRI demonstrated an average minimum disc-level canal diameter of 9.6 mm and spinal cord diameter of 8.1 mm. A total of 63 of 110 patients returned to play, and of those, 56% reported a recurrence of CCN. Predictors of recurrence included playing American football, a smaller Torg-Pavlov ratio, a smaller disc-level canal diameter, and less space available for cord, which implicates cervical stenosis as a risk factor. Age, level of sport, and symptoms/severity of CCN were not found to be predictive of recurrence.
Notably, no athlete followed in this study went on to suffer a permanent neurologic injury after returning to contact sports. Similarly, in other studies, athletes who had a football-related injury causing permanent quadriplegia denied any previous history of CCN. , This suggests that an episode of CCN, although a risk factor of recurrent episodes, is not associated with permanent neurologic injury. Thus, athletes without spinal instability who have had an episode of CCN are not at increased risk of permanent neurologic injury by returning to sport. This information can be valuable when discussing the risks of returning to play in athletes who have developmental cervical stenosis and a prior episode of CCN. It can also be inferred from the data that the more stenotic the individual’s anatomy is, the more likely they are to have a recurrent episode; moreover, prediction of future injury can be made with evaluation of a sagittal MRI.
Cervical fractures
Cervical fractures can occur when the area between the vertebral body and decelerating head undergoes rapid compression, requiring as little as 150 ft-lb of force to fracture the cervical vertebrae. Certain fracture patterns involving the spinous process or unilateral lamina do not typically cause significant instability and require only hard-collar immobilization for a period of 6 to 12 weeks as definitive treatment. Stability on flexion-extension radiographs after healing and maintenance of cervical lordosis are required for RTP. , Unstable fractures are best treated with surgical fixation, , , and in general, the literature supports RTP for players who are treated with a one-level subaxial anterior or posterior fusion if there is no pain, full ROM, normal muscle strength, complete fusion on imaging, and a normal neurologic examination.
Despite some disagreements, there seems to be strong consensus regarding certain absolute contraindications, including any patient with a fracture with residual neurologic deficits, underlying congenital stenosis, cervical laminectomy, and any procedures that require occipital, C1-C2, C2-C3, or 3+ level fusions. , , Consideration for NFL athlete RTP should involve imaging demonstrating solid fusion in the area of injury, lack of instability on flexion and extension radiographs, maintenance of normal cervical lordosis, full ROM with no associated pain, and preinjury muscle strength. , , In addition, sagittal misalignment greater than 11° when compared with other levels for isolated burst fractures and fractures that disrupt the posterior bony or ligamentous tension band may preclude RTP. ,
Currently, expert opinions advocate that athletes can be cleared for a return to contact sports following cervical spine trauma after fulfilling the following conditions of full functional, pain-free ROM of the cervical spine, baseline muscle strength, and absence of neurologic deficits. A 2-level cervical fusion is considered a relative contraindication to return to athletic activity, whereas a three- or more level fusion is considered an absolute contraindication. Athletes who suffer a subaxial cervical spine fracture may be allowed to return to contact play depending on the morphology of the injury, its resultant stability at the time of healing, and neurologic status.
Absolute contraindications for return to athletic play in athletes with subaxial cervical spine injury include an association with a residual neurologic deficit and/or congenital stenosis. Relative contraindications for return to athletic play include healed compression and stable burst fractures of the subaxial cervical spine. Athletes with cervical spine stenosis or in the setting of a moderate-to-large disc herniation with a history of transient neuropraxia or quadriparesis should be counseled to avoid returning to contact play unless the focal stenosis can be surgically remedied. Finally, other absolute disqualification criteria include a history of 2 episodes of cervical spinal cord neuropraxia even in the absence of spinal stenosis and the “spear tackler’s spine.”
Cervical Stenosis
There is a significant amount of controversy as it pertains to the diagnosis of cervical stenosis, which is defined as narrowing of the spinal canal. Based on the available literature to date, the authors believe that practitioners should rely on 4 categories of information for the management of these conditions as it pertains to RTP: clinical symptoms, physical examination, sport and position played, and imaging characteristics. In the setting of a player without any residual symptoms and normal strength and neurologic examination, individualized recommendations should rely on the type of demands of the player’s respective sport as well as what the advanced imaging (eg, MRI) studies demonstrate. The categorization of collision (ie, American football, rugby, hockey, etc.) versus contact sports (basketball, soccer, lacrosse, etc.) is important because of the relative risk of repetitive and traumatic hyperextension and axial compression forces to the cervical spine. Collision sports such as American football, rugby, hockey, etc. represent a significantly higher risk of reinjury in players with stenosis than contact and noncontact sports.
Among plain radiographic measurements, the Torg-Pavlov ratio has historically been most commonly used to diagnose cervical stenosis, which compares the width of the spinal canal with the vertebral body on a lateral radiograph. The width of the spinal canal is measured by the sagittal diameter of the canal from the middle of the posterior vertebral body to the nearest point on the spinolaminar line. This measure has also been found to correlate with both the vertebral body-to-canal ratio seen on CT imaging and the vertebral body-to-CSF column ratio seen on MRI. The threshold value that should be used to predict SCI is still under debate. Although the initial studies suggested that a ratio of 0.8 or lower was a significant predictor, Aebli and colleagues concluded that a threshold of 0.7 or less had the highest positive likelihood ratio to predict the occurrence of cervical spinal injury after minor trauma in the general population. However, a threshold of 0.7 had a high specificity of 99% but also a low sensitivity of 51%. Notably, the Torg-Pavlov ratio was not predictive of severity of injury according to the ASIA criteria for those who did suffer SCIs in this study.
Other measures have been used such as axial MRI images. In particular, 3 measurements have been implicated: the transverse spinal canal and cord area, the transverse and sagittal cord diameter, and the sagittal canal diameter of the cervical spine. Ruegg and colleagues demonstrated that all of these values were less in those who suffered an SCI with the exception of cord area. Both a cord-canal-area ratio greater than 0.8 and space available for the cord less than 1.2 mm were found to reliably identify patients at risk for cervical SCI after minor cervical spine trauma.
Based on the most recent literature, the authors believe that the measurement of the cervical spinal canal diameter on sagittal T2 MRI provides the most specific information in the diagnosis of this condition. Although historically cervical spinal stenosis had been defined as a space available for the cord less than 14 mm on plain radiographs, more recent and pertinent data suggest that this threshold may be too conservative when it comes to the risk of an SCI in the elite athlete population. Despite a small sample size, recent data suggest that 10-mm sagittal canal diameter measured on MRI is compatible with successful American football careers without increased risk of neurologic sequelae. Furthermore, Aebli and colleagues demonstrated that sagittal canal diameter of less than 8 mm on MRI increases the risk of acute SCI after minor trauma to the cervical spine. Although there are certainly other data that use other measures of spinal canal space, most of the evidence-based literature points toward this range as a potential threshold for RTP criteria when treating these athletes. In a systematic review of clinical studies involving high-energy contact athletes, Dailey and colleagues strongly recommended that those without stenosis can return to play and weakly recommended those with stenosis not to return to play after one episode of transient cervical cord neurapraxia.
Recommendations
The decision to return to play to both contact and collision sports with cervical stenosis is a complicated one for the athlete, family, and physician alike. Certain radiographic and MRI criteria may be helpful in identifying cervical stenosis. In particular, using plain radiographs, a Torg-Pavlov ratio less than 0.7 yields the highest positive predictive value for cervical SCI. Further MRI criteria such as the minimal disc-level canal diameter less than 8 mm, a cord-canal-area ratio greater than 0.8, or space available for the cord less than 1.2 mm can also be valuable for diagnosis. These 3 criteria may identify the “at-risk” athlete for more severe consequences and allow other athletes with measurements greater than these levels to return back to sport. For asymptomatic athletes without any previous neurologic deficits with space available for the cord greater than these thresholds, it is likely safe for them to return to both contact and collision sports.
For patients with cervical stenosis who have had an episode of cervical cord neuropraxia, counseling can be a critical asset. After a CCN without cervical stenosis or instability, the player may safely return to play once neurologically normal and demonstrate full painless range of motion. When CCN is associated with space available for the cord lower than published thresholds, there is some disagreement among practitioners in the management of these athletes. Although most would recommend not to return to collision sports after a second episode of a CCN with cervical stenosis, there have not been any cases documenting permanent neurologic or SCI after RTP. Especially for patients in high-risk sports, such as American football and rugby, counseling patients about the possibility of recurrence is very important.
Absolute contraindications of RTP include persistent neurologic symptoms, cervical pain, loss of ROM, os odontoideum, basilar invagination, atlanto-occipital instability, Chiari malformation, functional spinal stenosis, cervical instability due to fracture or ligamentous disruption, symptoms lasting greater than 36 hours, or repeat episodes of transient quadriplegia. , , RTP recommendations in American football athletes who demonstrate persistent cord hyperintensity (myelomalacia) despite surgical treatment is controversial. Spinal cord signal changes in T1- or T2-weighted MRI sequences (hypo-/hyperintense areas with focal atrophy) can be an indicator of persistent swelling and parenchymal disruption of the spinal cord. Although the presence of residual edema in the spinal cord may represent smaller reserve to withstand future forces on the cervical spine, Maroon and colleagues recommends that cord hyperintensity after surgery may not preclude RTP in NFL athletes. , Tempel and colleagues also reported persistent T2 hyperintensity in 3 professional athletes, all of whom returned to play without reinjury. Nonetheless, the presence of residual cord signal changes even in the absence of cervical stenosis or a herniated disc remains a relative contraindication for RTP.
Summary
In summary, RTP indications for patients with a history of congenital cervical stenosis or transient quadriplegia are controversial. Imaging studies should be considered in context with the athlete’s history, mechanism of injury, physical examination, and discussion of specific RTP risks with the athletes. , , Most athletes with cervical stenosis and 2 episodes of CCN usually do not return to contact sports. Athletes with an episode of a CCN with a defined lesion such as a disc herniation can often have surgical treatment that allows successful RTP.
Disclosure
The author has nothing to disclose.
References
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