The Epidemiology of Spine Injuries in Athletes

Barrett Boody, MD

Brett D. Rosenthal, MD

Shah-Nawaz M. Dodwad, MD

Alpesh A. Patel, MD

Dr. Patel or an immediate family member has received royalties from Amedica, Biomet, and Ulrich Medical USA; serves as a paid consultant to Amedica, DePuy, a Johnson & Johnson Company, Pacira, Relievant, and Zimmer; has stock or stock options held in Amedica, Cytonics, Nocimed, and Vital5; has received nonincome support (such as equipment or services), commercially derived honoraria, or other non-research–related funding (such as paid travel) from Springer; and serves as a board member, owner, officer, or committee member of AAOS, the American Orthopaedic Association, the AO Spine North America, Cervical Spine Research Society, Journal of the American Academy of Orthopaedic Surgeons, North American Spine Society, Surgical Neurology International, and Wolters Kluwer Health. None of the following authors or any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this article: Dr. Boody, Dr. Dodwad, and Dr. Rosenthal.

Introduction

As the number of competitive athletes continues to rise, training in the diagnosis and management of sport specific spine injuries is essential. During 2013 and 2014, more than 7.7 million high school and 460,000 college students participated in athletics, of whom 1.1 million high school and 70,000 college students participated in football.¹^,² Athletes have a significant number of potential injury exposures during practice and games. For example, in the National Football League (NFL), the estimated yearly average for potential injury exposure events to occur is 177,000 during practice and 35,000 during actual games.³ Previously, the lack of centralized systems to report and track spine injuries in athletes hindered our ability to document the frequency and circumstances surrounding these events. Over the past 40 years, widespread reporting of spine injuries in athletes has enabled sport organizations to protect athletes by penalizing high-risk player contact, such as spear tackling in football and checking from behind in hockey. As a result, we have seen a decrease in the rate of catastrophic spine injuries.⁴^,⁵^,⁶ Despite improvement in sport regulation and protective equipment, physicians continue to encounter a wide variety of spine pathologies, ranging from back pain to catastrophic neurologic injury.

Spinal Cord Injury

The National Spinal Cord Injury Statistics Center (NSCISC) compiles the largest spinal cord injury (SCI) database in the United States, producing yearly reports that review the epidemiology of new cases, as well as trends extending over several decades. In the 2013 report, sporting injuries are listed as the fourth most common etiology of SCI, responsible for 3054 or 9.2% of all reported cases of SCI with only motor vehicle collision (36.5%), falls (28.5%), and violence (14.3%) occurring more frequently. Within the sports-related SCI subgroup, participants between the ages of 16 and 30 years account for the majority of cases (68.5%), with boys and men involved in 89% of SCIs. The sporting activity identified with the highest SCI incidence was snow skiing, ranking 11th in overall etiology and 1st within the sports subgroup with a total of 154 cases. Football ranked 12th overall and 2nd within the sports-related SCI subgroup with a total 145 cases.⁷ Schmitt et al investigated causes of SCI in Germany from 1985 to 1997, identifying 1016 cases. They attribute 6.8% of SCIs to being sports related, with the majority of sporting accidents involving downhill skiing (n = 16) and horseback riding (n = 9). They reported an incidence of serious spine injuries among skiers as 0.01 injuries per 1000 skier-days.

Tator et al reviewed hockey injuries in Canada between 1966 and 1996, identifying 243 spine injuries with 90% occurring from C1 to T1. The most common reported injury morphologies were burst fractures and fracture-dislocations. Approximately 40% of injuries involved checking from behind, and 77% involved checking into the boards.⁸ Although football is associated with a higher occurrence of SCI, the rate of SCI in ice hockey is nearly three times higher. Of the 207 players with neurologic injuries, 108 (52%) were permanent injuries, and 52 (25%) were complete injuries, with 8 deaths related to SCI. Only 31 of the 243 SCIs were reported before 1982; however, this is likely attributable to the lack of a centralized reporting system. The Canadian Ice Hockey Spinal Injuries Registry was established in 1981 and shortly thereafter in 1984 began reporting the significant hazard of checking from behind into the boards that prompted the subsequent rule changes in 1985 banning this action.⁶ Tator et al demonstrated a continued decline in the annual incidence of spine injuries in his Think First Canadian Ice Hockey Spinal Injuries registry with 40 spine injuries and 5 severe SCIs with permanent neurologic deficits occurring between 2000 and 2005. In 2005, Tator et al reported a 69% decrease in the incidence of SCIs in participants ages 18 years and older compared with before 2001.⁶

Football-Specific Cervical Spine Injuries

Spine-related complaints are common among football players, with nearly 11,500 football related neck injuries presenting yearly to emergency departments in the United States.⁹ Mall et al reviewed 2208 NFL spine and axial skeleton injuries over 11 seasons, 44.7% of which involved the cervical spine (Table 1-1).³ They found the injury with the greatest average time missed from play was thoracic disk herniation (189 days) followed by cervical fracture (120 days) and cervical disk herniation (85 days). They estimated NFL players totaled 386,688 potential game injury exposures and 1,947,750 potential practice injury exposures over the 11-season time period. Muscular injuries were the most common reported injury (41.2%) followed by nerve injury (21.4%), disk injury (11.4%), and fractures (3.7%).³

Cervical spine pathology has been shown to have a significant negative impact on NFL players’ careers. Schroeder and colleagues reported on 143 NFL athletes from 2003 to 2011 with prior cervical spine pathology, the most common diagnoses being spondylosis (87 players), stenosis (30 players), and cervical sprain or strain (24 players). They noted that these athletes were less likely to be drafted and had less total games played, with no difference in total games started or performance scores compared with other football players without prior cervical spine diagnoses.¹⁰ Of athletes who had sagittal cervical spine canals smaller than 10 mm, no differences were shown in the number of games or years played or in performance scores. Also, these players with cervical stenosis had no reported neurologic injuries. Furthermore, 7 athletes with prior cervical spine surgery displayed no difference in career longevity compared with the average NFL player.¹⁰ Meredith and colleagues reviewed outcomes in 16 NFL players with cervical disk herniations undergoing operative versus nonoperative treatment. They noted that 1 of 3 (33%) surgically managed and 8 of 13 (61%) conservatively treated players eventually returned to play.¹¹ They concluded that nonoperative management of NFL players can be successful in the management of cervical disk herniations, with return to play (RTP) predicated on complete relief of symptoms and no cord compression on follow up MRI.¹¹

Catastrophic Cervical Spine Injuries

The safety of American football has been substantially improved by efforts to identify and report player injuries. From 1971 to 1975, Torg and colleagues reported on 259 cervical fracture-dislocations with an incidence of 4.14 per 100,000 exposures, 99 cases of quadriplegia with an incidence of 1.58 per 100,000 exposures, and 77 deaths related to severe neck injuries.¹² As a result of the reported significant morbidity and mortality of cervical spine injuries, headfirst contact or spear tackling was banned by the National Collegiate Athletic Association’s football rules committee and high school football governing bodies. After these rule changes, reported cervical spine fractures decreased 70%, and traumatic quadriplegia decreased 82% from 1976 to 1987.⁴^,¹³

Boden et al reviewed 196 catastrophic cervical spine injuries occurring in high school and college football players between 1989 and 2002 and found that 76 athletes during their study had an injury that resulted in quadriplegia. Quadriplegic injuries had an incidence of 0.50 per 100,000 high school and 0.82 per 100,000 college participants with a 1.65 times higher risk in the collegiate football players. The position played at the time of injury was identified in 70 players with the defensive back position having the highest quadriplegic injury occurrence of 44.3% followed by special teams players at 18.3% and then linebackers with 17.1%. They identified spear tackling as the cause in 88% of

these catastrophic events.⁵ Boden et al further reviewed fatalities related to high school and college football between 1990 and 2010, noting 164 noncontact and 79 traumatic causes of fatalities, estimating approximately 4 deaths annually. Cervical fractures were the cause in 4 mortality cases, and the most common causes of death were related to cardiac (100 players), brain injury (62 players), and heat illness (38 players).¹⁴ They found that the fatality rates related to cervical spine fracture were greatly reduced from previously reported rates, an improvement they believed reflected the rule changes regarding spear tackling.¹⁴

TABLE 1-1 Cervical spine injuries in athletes

Author	Sport	Type of Study	Demographics	Pathology	Outcomes of Interest
Tator⁷	Hockey	Retrospective	Amateur and professional, 1966–1996	243 spine injuries (fracture and/or dislocation and neurologic deficits) identified in Canadian Ice Hockey Spinal Injuries Registry	Push or check from behind in 40%, impact with boards in 77%; ∼50% of injuries occurred in 16- to 20-year old athletes
Tator et al⁶	Hockey	Retrospective	Amateur and professional, 2000–2005	40 spine injuries (fracture and/or dislocation and neurologic deficits) identified in Canadian Ice Hockey Spinal Injuries Registry	82.8% spine injuries within cervical spine; push or check from behind in 35%, impact with boards in 64.8%; five (12.5%) severe injuries identified (complete and incomplete SCIs)
Mall et al³	Football	Retrospective	NFL players (professional), 2000–2010	2208 spine or axial skeleton injuries identified (7% of overall injuries) from NFL registry	Most common spine injury was muscular (41.2%); nerve injury and fractures accounted for 21.4% and 3.7%, respectively; on average, 25.7 days missed because of spine injuries; 987 (44.7%) of injuries occurred in cervical spine with 14 SCIs reported
Schroeder et al⁹	Football	Retrospective cohort	American football athletes attending NFL combine, 2003–2011	143 players with cervical spine diagnoses (2965 evaluated athletes)	Athletes with cervical spine diagnoses less likely to be drafted and lower total NFL games played than athletes without cervical spine diagnoses; players with history of cervical spine surgery or congenital stenosis with no difference in career longevity or performance
Torg et al¹¹	Football	Retrospective	Amateur and professional, 1971–1975	1,275,000 estimated player exposures; retrospective data collection	259 cervical fracture-dislocations, 99 cervical fracture-dislocations resulting in permanent quadriplegia; 77 deaths from severe neck injuries
Boden et al⁵	Football	Retrospective	High school and collegiate (amateur), 1989–2002	196 catastrophic cervical spine injuries; incidences, 1.10 and 4.72 per 100,000 high school and collegiate players, respectively, using National Center for Catastrophic Sports Injury Research registry	76 cases of quadriplegia; 43 cases of cervical CN, with 16 players returning to sport (no additional CCN reported)
Torg et al¹⁵	Football	Retrospective cohort	Amateur and professional	45 athletes with CCN	Ratio of spinal canal to vertebral body diameter on lateral radiographs <0.8 with 93% sensitivity, 59% specificity for CCN; because of the low incidence of CCN (7.3 per 10,000), PPV reported as 0.2%
Charbonneau et al¹⁷	Football	Retrospective	Collegiate athletes (amateur), 2010 season	244 players; 64 (26%) episodes of brachial neurapraxia (stingers)	59% of stingers reported to medical staff; 14% of players reported >1 stinger during 2010 season; 62% lifetime prevalence of stingers; no statistically significant effect of protective equipment
CCN = cord neurapraxia, NFL = National Football League, PPV = positive predictive value, SCI = spinal cord injury.