Cervical Strain/Sprains

Cervical spine injuries that are predominantly muscular or ligamentous are considered cervical strains or sprains, respectively. Cervical strains and sprains accounted for 21.7% and 15.5% of cervical spine injuries in NFL athletes and were responsible for a career mean of 6.0 and 9.6 days of activity lost per injury, respectively, from 2000 to 2010. Most of these injuries are self-limited, however, despite the lack of direct neurologic insult, spinal instability should still be ruled out to avoid delayed injury. In addition to a detailed history and physical examination, dynamic radiographs are critical to the diagnosis of cervical spine instability. Cantu and colleagues recommended that any subluxation noted after a sport-related injury necessitates a hard cervical collar to be worn at all times with follow-up imaging taken at 2 and 4 weeks after injury. Based on cadaveric studies, the definition of a subluxation is reported at greater than 3.5 mm of horizontal displacement of 1 vertebral body relative to the next or angular displacement of greater than 11° between adjacent vertebrae. These investigators also cautioned that adolescent athletes have increased ligamentous laxity of unclear significance, which may account for measurements outside this norm. If repeat imaging shows stability and pain and range of motion have resolved, most experts agree that return to play for these athletes is safe.

Stingers/Burners

A stinger or burner is a temporary episode of unilateral upper extremity dysesthesia, which is estimated to occur at least once during the career of more than 50% of athletes participating in contact/collision sports. Although improvements in shoulder pads have reduced the frequency of stinger injuries, nerve injuries without evidence of causal anatomic conditions were still the most common cause of cervical spine injury among NFL athletes between 2000 and 2010. Cervical nerve injuries comprised 45.9% of all cervical spine injuries and resulted in a career mean of 15.3 days of activity lost per injury. Motor weakness may not occur during a stinger but, if present, is most common in the C5 and C6 myotomes. Proposed mechanisms of injury include traction injury to the brachial plexus, nerve root compression at the neural foramina, and direct trauma to the brachial plexus, most often at Erb’s point (where the upper trunk can be compressed against a transverse process).

Typically, symptoms resolve within a few minutes. If symptoms have resolved and it is the athlete’s first episode of having a stinger, he or she can return to the sporting event as long as cervical range of motion is maintained and no neurologic deficits are present. After the resolution of an athlete’s second episode of stinger, Cantu recommends considering use of high shoulder pads, a soft cervical roll to limit neck flexion and extension, and review of the athlete’s blocking and tackling techniques to identify if modifications may decrease the likelihood of recurrent injury. Some experts suggest that the occurrence of 3 or more stingers, especially if in rapid succession, is a relative contraindication to continued sport participation. Certain athletes, those with foraminal stenosis, are predisposed to recurrent and chronic stinger injuries. Because the dorsal root ganglion occupies the largest proportion of space within the neural foramen, it often takes the brunt of the injury, which is why purely sensory findings may be the result of a stinger. Although the long-term natural history of athletes who have recurrent stingers is not well described in the scientific literature, some believe that recurrent episodes may lead to long-term proximal arm weakness and persistent pain.

If symptoms persist after a stinger injury, alternative etiologies for the athlete’s symptoms should be explored. In that situation, radiographs to rule out fractures or instability and an MRI to rule out disc herniation or other structural abnormalities should be performed. Cantu recommends that electromyography be performed if symptoms persist greater than 2 weeks to accurately assess the extent of injury. Weinstein recommends continued cessation from sport if the athlete has clinical weakness and moderate fibrillation potentials 2 weeks postinjury.

Cervical Stenosis, Cervical Cord Neurapraxia, and Transient Quadriplegia

Cervical stenosis may be present congenitally or caused by degenerative spondylotic changes. One phenomenon, initially described by Torg and colleagues, is that of cervical cord neurapraxia (CCN), wherein an athlete sustains transient bilateral motor or sensory neurologic symptoms that begin after a blow to the head or a whiplash neck injury. One manifestation of this condition is referred to as transient quadriplegia . These clinical entities seem to most often occur in athletes who have cervical stenosis. Narrowing of the cervical spinal canal places individuals at increased risk of cord injury during cervical trauma. Most of these injuries occur with a hyperextension and axial load mechanism, because this position further narrows the anteroposterior space available for the cord.

CCN tends to occur in high-velocity, high-impact sports such as football, rugby, and hockey. CCN is estimated to occur in 7.3 per 10,000 football players. In one series, 57% returned to contact activities after their first episode, and 56% of the athletes who returned to play suffered a second episode of CCN. Recurrence of symptoms was associated with radiographic and MRI evidence of progressive cervical stenosis. The diagnostic workup for CCN after determination of a stable cervical spine often includes dynamic plain films to assess for fractures and subtle instability and an MRI to identify sources of ongoing neural impingement.

Screening for cervical stenosis and the risk of CCN is far more controversial. Athletes may be exposed to repetitive loads or collisions that the general population are typically spared. Evidence suggests that long-term athletic participation increases the risk of radiographic signs of cervical spondylosis. Additionally, some individuals with morphologic abnormalities of the posterior elements (eg, shorter lamina length) may have congenital cervical stenosis. Although an athlete may be asymptomatic outside of sporting activity, his or her functional reserve may be compromised to a critical point, increasing the risk of sustaining spinal cord injury during participation in contact/collision sports. Radiographic assessment of the Pavlov/Torg ratio may be used as an adjunct to an athlete’s assessment. The Pavlov/Torg ratio is the distance from the midpoint of the posterior aspect of a vertebral body to its corresponding spinolaminar line divided by the anteroposterior diameter of the same vertebral body, as measured on a lateral radiograph. A normal ratio is 1, and a ratio less than 0.8 indicates spinal stenosis. Torg and colleagues identified that a ratio of less than 0.8 was highly sensitive for athletes who had sustained an episode of transient neurapraxias, but the ratio had a low specificity (about 58%) and low positive predictive value (0.2%), which diminish its utility as a screening tool for determining an athlete’s ability to participate in contact/collision sports. Additionally, Herzog and colleagues identified that athletes tended to have larger vertebral bodies, which resulted in 41% of the asymptomatic professional football players having a Pavlov/Torg ratio less than 0.8 in their series.

Alternatively, Cantu posits that a loss of cerebrospinal fluid surrounding the spinal cord or the presence of cord deformation, as measured on axial MRI slices, indicates the presence of a functional stenosis, suggesting a loss of the patient’s functional reserve (eg, protective CSF cushion). Cantu and his associates considered this a contraindication to participate in contact/collision sports even if the player is asymptomatic because of a theorized increased risk of CCN. However, obtaining an MRI on every athlete who wishes to engage in contact/collision sports is not cost effective and can lead to many incidental diagnoses. A recent systematic review by Dailey and colleagues summarizes the available evidence and puts forth a weak recommendation that patients with transient neurapraxias and evidence of stenosis on MRI should not return to full participation in high-energy contact sports. Additionally, a strong recommendation was made that if no evidence of stenosis is identified on MRI and the CCN symptoms are transient, consideration should be made for full return to sport activities. Torg and Ramsey-Emrhein considered a history of CCN with the presence of a cord lesion on MRI as a relative contraindication to return to play. The persistence of symptoms for greater than 36 hours, recurrence of CCN, or evidence of ligamentous instability are also considered absolute contraindications to return to play.

Cervical Disc Herniation

Contact sport athletes have higher rates of cervical disc herniations (CDH) than the general population ; whereas, noncontact athletics may provide a slight protective effect because of dynamic muscular support of the cervical spine. An asymptomatic cervical disc condition that is incidentally identified necessitates a thorough history and physical of the athlete. In the absence of pain, limited range of neck motion, neurologic deficits, or signs of myelopathy, it is appropriate to allow the player to continue his participation in sport. Of patients younger than 40 years, 10% of asymptomatic individuals have a herniated nucleus pulposus of the cervical spine identifiable on MRI. The presence of symptoms, myelopathic signs, deficits of strength, or diminished range of motion are contraindications to the participation in athletics because the concern remains that sport-related activities could exacerbate current signs and symptoms of neurologic compression. CDHs accounted for 5.8% of cervical spine injuries to NFL athletes between 2000 and 2010 and were responsible for a career mean of 84.8 days of activity lost per injury. In a retrospective review, Hsu identified CDH as a potentially career-ending injury, with 28% of operatively treated and 54% of nonoperatively treated NFL athletes never returning to professional play. Despite the potential severity of the condition, many athletes return to professional sport and perform well after CDH. Athletes show no significant differences in sport performance whether operative or nonoperative treatment was selected; however, operatively treated CDH athletes had higher rates of return to play, played more games after their return, and had longer careers posttreatment.

After failure of conservative measures, surgical treatment options that may be considered include posterior foraminotomy/decompression and anterior cervical discectomy and fusion (ACDF). Current guidelines are based on expert opinions and are experiential in nature. The general consensus is that posterior foraminotomy poses minimal change to the cervical spine’s structural integrity; therefore, return to play with full contact is possible. Burnett and Sonntag cautioned that if a 2-level or more cervical laminectomy was required for adequate decompression, return to full-contact play would not be admissible regardless of whether posterolateral fusion was performed.

Single-level ACDFs less than C3 are generally deemed safe for return to play if range of motion is preserved, neurologic deficits resolve, and a solid fusion occurs. Although some caution that a 2-level ACDF is a relative contraindication to return to play, other surgeons suggest that this procedure should not preclude a collision athlete from returning to play. Most experts agree that a 3-level ACDF is a contraindication to return to contact sports.

Fractures

A broad range of cervical fractures may be sustained during athletic performance. The fracture morphology, location, and extent of neurovascular involvement all contribute to determining a player’s prognosis. Return-to-play criteria are based on multiple factors because of the breadth of potential injuries. Cervical fractures are the least frequently sustained cervical injury among NFL athletes (1.8%), but they result in the greatest career mean number of days of activity lost per injury (119.7 days).

Spinous process fractures typically occur in the lower cervical spine and may occur secondary to avulsion, direct blow, or hyperflexion. Historically, these injuries were identified in manual laborers, which is why they are also referred to as clay-shoveler’s fractures . More recently, spinous process avulsion fractures have been reported in dance, golf, weight lifting, and volleyball. Their clinical course is generally benign, and return to play can occur as soon as osseous healing has completed, pain has resolved, and range of motion is restored. Rarely have nonunions been reported that required excision of the nonunited fragment.

Axial loads have been implicated in many football-induced cervical spine traumas, which is a common mechanism to sustain burst or compression fractures of the cervical spine. Unstable Jefferson fractures require C1 to C2 fusion or occipitocervical fusion. Among the fragility of C1, the importance of the transverse and alar odontoid ligaments, and the functional limitations incurred from upper cervical arthrodesis, fusion of the upper cervical spine is an absolute contraindication for return to play. Subaxial cervical spine fractures also may require fusion procedures. As discussed previously, ACDF is not an absolute contraindication to return to play. Range of motion, neurologic deficits, pain, and strength must all be improved before returning to full athletic activities. In the setting of prior fracture, it is of utmost importance to assess for residual instability on follow-up radiographs before allowing an athlete to return to sport activities. Additionally, in athletes who use a head-first tackle technique, also known as spearing , the cervical spine may progressively kyphose because of cumulative trauma and residual deformity from prior vertebral injuries. This clinical entity, known as spear tackler’s spine , is regarded an absolute contraindication to return to contact/collision sports.