By Gordon R. Bell, MD
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Spinal — and particularly neck — injuries are among the most feared and dangerous injuries in sports. Decisions about whether and when a player may safely return to competition can be difficult. Because the necessary scientific data to inform such decisions are generally incomplete, return-to-play decisions are too often ambiguous and subjective.
Football helmets: Good for heads, bad for necks?
Football is the sport most commonly associated with cervical spine injuries. A review of football head and neck injuries from 1959 to 1963 found that rates of intracranial hemorrhage and intracranial death were two to three times greater than rates of cervical spine fracture/dislocation or cervical quadriplegia.
In contrast, a study of football injuries from 1971 to 1975 revealed a dramatic reversal in injury rates, with the incidence of cervical spine fracture/dislocation exceeding the rate of intracranial hemorrhage and death by twofold to fourfold. This study found that, compared with 1959-63, there was a 66 percent reduction in intracranial bleeds and a 42 percent reduction in craniocerebral deaths but a 204 percent increase in cervical spine fractures and dislocations.
This shift from head to spine injuries was attributed to the modern football helmet, whose superior protection of the head paradoxically promoted playing techniques that put the neck at risk for potentially catastrophic injury.
Enemy No. 1: Spearing
Specifically, a headfirst tackling technique known as spearing, in which the player hits with the crown of his helmet, results in straightening of the cervical spine and axial loading of the spine on impact. The resulting axial forces are not dissipated as well as when the spine is lordotic, which can result in failure of the spine with the potential for spinal cord injury (Figure 1).
Spearing accounted for an estimated 52 percent of the quadriplegia injuries in football from 1971 to 1975.
Philadelphia orthopaedic surgeon Joseph Torg, MD, was instrumental in describing the significance of spearing as a cause of spinal cord injury. His landmark work resulted in the National Collegiate Athletic Association’s adoption of rules in 1976 to eliminate spearing in collegiate football, which led to an immediate 50 percent reduction of quadriplegia in collegiate football. The incidence of quadriplegia has continued to fall since, to a current rate of less than 0.5 per 100,000 athletes.
Another threat: Concussion to the spinal cord
In 1986 Torg coined the term cervical cord neurapraxia (CCN) to describe a concussion to the spinal cord asa result of an on-field collision.
CCN is a transientmotor and/or sensory disturbance, lasting less than 24hours, that Torg found to occur in approximately 7.3per 10,000 athletes in a 1984 survey of nearly 40,000college football players. In Torg’s view, CCN is a distinctand separate entity from spinal cord injury resulting inquadriplegia.
Notably, approximately 50 percent of players experiencing a transient episode of CCN who decide to return to play experience a second such episode. The risk of experiencing a second episode is inversely proportional to the size of the cervical bony canal, as athletes with narrow canals are more likely to experience another episode than are those with larger canals.
Why spinal canal size matters most
When faced with an athlete who has experienced a transient episode of CCN, the physician’s role is to determine if there is a structural abnormality that could put the athlete at risk for another transient episode of CCN or a potentially catastrophic permanent spinal cord injury.
Unfortunately, the data to guide such decisions are incomplete. At minimum, however, the physician can tell the patient that if his canal diameter is less than normal, he has a risk of experiencing another transient episode. Exactly what that risk is depends on how narrow the canal is. A normal canal diameter (14 mm on MRI) is associated with an approximately 5 percent risk of a subsequent CCN episode, whereas a narrow canal (9 mm or less) is associated with a more than 50 percent risk of recurrence.
Whether another transient episode could lead to permanent spinal cord injury is unknown, although Torg thinks not. Others hold a contrary view, but it would seem the risk is low.
The long-term effect of one or more episodes of CCN on spinal cord function is also unknown. Only recently have we begun to appreciate the long-term effect of multiple concussions on brain function. It seems intuitive that the potential exists for long-term sequelae following multiple CCN episodes.
Return-to-play consensus points
There is general agreement that return to play is permitted in the following circumstances:
- A healed fracture with normal alignment
- A small, asymptomatic cervical disk herniation
- A single episode of CCN with normal studies and no functional stenosis
Similarly, there is general agreement that return to play is contraindicated under the following circumstances:
Points of contention — and the author’s perspective
More controversial is whether an athlete should return to a collision sport following even a single episode of CCN when there is evidence of significant narrowing of the spinal canal with spinal cord compression.
Some authors refer to this as functional stenosis with a reduced functional reserve — a significant reduction or elimination of the “cushion” of cerebrospinal fluid surrounding the spinal cord. Based on my review of this subject, I am very reluctant to return a player to a collision sport following an episode of CCN in the presence of significant functional stenosis.
Return-to-play decisions after spinal cord injury are difficult, and the price of a wrong decision can be high. As long as objective data to guide these decisions remain limited, it seems prudent that an athlete with an episode of CCN in the presence of functional stenosis be advised to avoid collision sports.
Dr. Bell is Director of the Center for Spine Health in Cleveland Clinic’s Neurological Institute.
Figure 1. Cervical X-rays and MRIs from the illustrative case of a 25-year-old pro football player who sustained several episodes of leg weakness and gait unsteadiness following head-on collisions. Top left: Lateral cervical X-ray showing reversal of normal cervical lordosis with frank kyphosis. Lordosis is protective and helps dissipate forces from an axial collision. Straightening of the spine and kyphosis can result in axial forces being transmitted to the vertebral bones and result in fracture or other catastrophic spine injury. Top right: Lateral cervical MRI showing a C4-5 disk herniation with narrowing of the cervical spinal canal. Bottom left: Axial MRI at C4-5 showing the midline disk protrusion indenting the cervical spinal cord. Bottom right: Postoperative lateral cervical X-ray showing a two-level fusion at C3-4 and C4-5. The initial surgery was a single-level anterior cervical discectomy and fusion (ACDF) at C4-5 that eliminated the herniation and cord compression but did not completely address the kyphosis. Because the patient continued with symptoms of cord compression with residual kyphosis at C3-4, he underwent a second ACDF at C3-4. He did not return to football and has not experienced further gait abnormality.