The epidemiologic, pathologic, biomechanical, and cinematographic analysis of football-induced cervical spine trauma

Catastrophic Sports Injuries: Causation and Prevention

➤ Catastrophic injuries in U.S. high school and college athletes are rare but devastating injuries.➤ Catastrophic sports injuries are classified as either traumatic, caused by direct contact during sports participation, or nontraumatic, associated with exertion while participating in a sport.➤ Football is associated with the greatest number of traumatic and nontraumatic catastrophic injuries for male athletes, whereas cheerleading has the highest number of traumatic catastrophic injuries and basketball has the highest number of nontraumatic catastrophic injuries for female athletes.➤ The incidence of traumatic catastrophic injuries for all sports has declined over the past 40 years, due to effective rule changes, especially in football, pole-vaulting, cheerleading, ice hockey, and rugby. Further research is necessary to reduce the incidence of structural brain injury in contact sports such as football.➤ The incidence of nontraumatic catastrophic injuries has increased over the last 40 years and requires additional research and preventive measures. Avoiding overexertion during training, confirming sickle cell trait status in high school athletes during the preparticipation physical examination, and developing cost-effective screening tools for cardiac abnormalities are critical next steps.

Management of Acute Subaxial Trauma and Spinal Cord Injury in Professional Collision Athletes

Sports-related acute cervical trauma and spinal cord injury (SCI) represent a rare but devastating potential complication of collision sport injuries. Currently, there is debate on appropriate management protocols and return-to-play guidelines in professional collision athletes following cervical trauma. While cervical muscle strains and sprains are among the most common injuries sustained by collision athletes, the life-changing effects of severe neurological sequelae (ie, quadriplegia and paraplegia) from fractures and SCIs require increased attention and care. Appropriate on-field management and subsequent transfer/workup at an experienced trauma/SCI center is necessary for optimal patient care, prevention of injury exacerbation, and improvement in outcomes. This review discusses the epidemiology, pathophysiology, clinical presentation, immediate/long-term management, and current return-to-play recommendations of athletes who suffer cervical trauma and SCI.

Operative Treatment of Cervical Spine Injuries Sustained in Youth Sports

BACKGROUND

Little data exists on surgical outcomes of sports-related cervical spine injuries (CSI) sustained in children and adolescent athletes. This study reviewed demographics, injury characteristics, management, and operative outcomes of severe CSI encountered in youth sports.

METHODS

Children below 18 years with operative sports-related CSI at a Level 1 pediatric trauma center were reviewed (2004 to 2019). All patients underwent morden cervical spine instrumentation and fusion. Clinical, radiographic, and surgical characteristics were analyzed.

RESULTS

A total of 3231 patients (mean, 11.3±4.6 y) with neck pain were evaluated for CSI. Sports/recreational activities were the most common etiology in 1358 cases (42.0%). Twenty-nine patients (2.1%) with sports-related CSI (mean age, 14.5 y; range, 6.4 to 17.8 y) required surgical intervention. Twenty-five were males (86%). Operative CSI occurred in football (n=8), wrestling (n=7), gymnastics (n=5), diving (n=4), trampoline (n=2), hockey (n=1), snowboarding (n=1), and biking (n=1). Mechanisms were 27 hyperflexion/axial loading (93%) and 2 hyperextension injuries (7%). Most were cervical fractures (79%) and subaxial injuries (79%). Seven patients (24%) sustained spinal cord injury (SCI) and 3 patients (10%) cord contusion or myelomalacia without neurological deficits. The risk of SCI increased with age (P=0.03). Postoperatively, 2 SCI patients (29%) improved 1 American Spinal Injury Association Impairment Scale Grade and 1 (14%) improved 2 American Spinal Injury Association Impairment Scale Grades. Increased complications developed in SCI than non-SCI cases (mean, 2.0 vs. 0.1 complications; P=0.02). Bony fusion occurred in 26/28 patients (93%) after a median of 7.2 months (interquartile range, 6 to 15 mo). Ten patients (34%) returned to their baseline sport and 9 (31%) to lower-level activities.

CONCLUSIONS

The incidence of sports-related CSI requiring surgery is low with differences in age/sex, sport, and injury patterns. Older males with hyperflexion/axial loading injuries in contact sports were at greatest risk of SCI, complications, and permanent disability. Prevention campaigns, education on proper tackling techniques, and neck strength training are required in sports at high risk of hyperflexion/axial loading injury.

LEVEL OF EVIDENCE

Level III-retrospective cohort study.

Mechanisms of mid-thoracic spine fracture/dislocation due to falls during horse racing: A report of two cases

We reported two cases of jockeys who sustained fracture/dislocation of the mid-thoracic spine due to traumatic falls during horse racing. We examined the injury mechanism based upon the patients' diagnostic images and video footage of races, in which the accidents occurred. Admission imaging of patient 1 (a 42 years old male) revealed T5 burst fracture with bony retropulsion of 7 mm causing complete paralysis below T5/6. There existed 22° focal kyphosis at T5/6, anterolisthesis of T5 relative to T6, T5/6 disc herniation, cord edema and epidural hemorrhage from T4 through T6, and cord injury from C3 through C6. Admission imaging of patient 2 (a 23 years old male) revealed T4/5 fracture/dislocation causing incomplete paralysis below spinal level. There existed compression fractures at T5, T6, and T7; 4 mm anterior subluxation of T4 on T5; diffuse cord swelling from T3 through T5; comminuted fracture of the C1 right lateral mass; right frontal traumatic subarachnoid hemorrhage; and extensive diffuse axonal injury. The injuries were caused by high energy flexion-compression of the mid-thoracic spine with a flexed posture upon impact. Our results suggest that substantially greater cord compression occurred transiently during trauma as compared to that documented from admission imaging. Video footage of the accidents indicated that the spine buckled and failed due to abrupt pocketing and deceleration of the head, neck and shoulders upon impact with the ground combined with continued forward and downward momentum of the torso and lower extremities. While a similar mechanism is well known to cause fracture/dislocation of the cervical spine, it is less common and less understood for mid-thoracic spine injuries. Our study provides insight into the etiology of fracture/dislocation patterns of the mid-thoracic spine due to falls during horse racing.

Cervical Spine Injuries in the Ice Hockey Player: Current Concepts in Epidemiology, Management and Prevention

STUDY DESIGN

This review article examines the biomechanics that underly hockey-related cervical spine injuries, the preventative measures to curtail them, optimal management strategies for the injured player and return to play criteria.

OBJECTIVE

Hockey is a sport with one of the highest rates of cervical spine injury, but by understanding the underlying pathophysiology and context in which these injuries can occur, it is possible to reduce their incidence and successfully manage the injured player.

METHODS

Multiple online databases including PubMed, Google Scholar, Columbia Libraries Catalog, Cochrane Library and Ovid MEDLINE were queried for original articles concerning spinal injuries in ice hockey. All relevant papers were screened and subsequently organized for discussion in our subtopics.

RESULTS

Cervical fractures in ice hockey most often occur due to an increased axial load, with a check from behind the most common precipitating event.

CONCLUSIONS

Despite the recognized risk for cervical spine trauma in ice hockey, further research is still needed to optimize protocols for both mitigating injury risk and managing injured players.

On-Field Management of Suspected Spinal Cord Injury

Acute spinal cord injuries in athletes are rare. However, on-field management of such injuries requires a well-planned approach from a team of well-trained medical staff. Athletes wearing protective gear should be handled with care; a primary survey should be conducted to rule out life-threatening injury while concomitantly immobilizing the spine. Treatment with steroids or hypothermia have not been shown to be beneficial, ultimately time to surgery provides the athlete with the best chance of a good outcome.

Transient Quadriparesis and Cervical Neuropraxia in Elite Athletes

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.

Return to Play Guidelines After Cervical Spine Injuries in American Football Athletes: A Literature-Based Review

STUDY DESIGN

Literature-based review.

OBJECTIVE

We sought to evaluate clinical and case studies related to return to play (RTP) after cervical spine injuries in elite American football athletes and to formulate guidelines to help health care practitioners manage these conditions.

SUMMARY OF BACKGROUND DATA

American football athletes are at unique risk of cervical spine injury and appropriate case-by-case management of cervical spine injuries is necessary for these athletes. Despite this need, no standardized guidelines exist for RTP after cervical spine injury.

METHODS

Observational or case-based articles relating to RTP after cervical spine injury in American football athletes were curated from PubMed/EMBASE databases. Primary literature published before December 1, 2019 involving National Football League (NFL) or National Collegiate Athletic Association (NCAA) athletes met inclusion criteria.

RESULTS

The data acquisition process yielded 28 studies addressing cervical spine injuries and RTP in American football athletes. Stingers/burners were the most common injury and placed athletes at higher risk of a more severe re-injury. Transient quadriplegia, cervical stenosis, cervical disc herniation (CDH), and cervical fractures have a more significant impact on the long-term health and career longevity of the American football athlete. As such, the literature offers some guidance for management of these athletes, including average time for RTP in patients treated nonoperatively, thresholds involving cervical stenosis, and postoperative recommendations after spinal decompression and/or fusion surgery.

CONCLUSION

Elite American football athletes are at high risk for cervical spine injury due to the nature of their sport. The decision to allow these athletes to return to play should involve an understanding of the average RTP time, the potential risks of recurrence or re-injury, and individual characteristics such as position played and pathology on imaging.Level of Evidence: 3.

Sports-Related Cervical Spine Injuries - Background, Triage, and Prevention

ABSTRACT

Cervical spinal injuries are a rare, but potentially devastating occurrence in sports. Although many of these injuries occur in unsupervised sports, they are also seen in organized sports - most commonly in football, wrestling, and ice hockey. Additionally, although each sport is associated with its own unique injury patterns, axial loading remains a common theme seen in cervical injuries associated with significant neurologic impairment. Regardless of the mechanism, a cautious and conservative approach should be taken with regards to evaluation, management, and return to play.

The Prevalence and Management of Stingers in College and Professional Collision Athletes

PURPOSE OF REVIEW

Particularly common in collision sports such as American football or rugby, stingers are a traumatic transient neuropraxia of a cervical nerve root(s) or brachial plexus that may last anywhere from minutes to hours. This review summarizes the knowledge on the diagnosis and management of stingers in college and professional collision athletes by providing an overview of their epidemiology and pathophysiology, followed by a discussion on current treatment guidelines and return-to-play recommendations.

RECENT FINDINGS

Despite modifications to tackling technique, increasing awareness, and various equipment options, American football continues to have a high rate of cervical spine injuries, the majority of which occur in preseason and regular season competition settings. The incidence of stingers has slowly increased among collision athletes, and nearly half of all players report sustaining at least one stinger in their career. Recent studies have shown certain anatomical changes in the cervical spine are related to acute and reoccurring stingers. Most players who experience stingers do not miss practices or games. Despite their prevalence, literature highlighting the impact of stingers on college and professional collision athletes is limited. Advances in imaging modalities and novel radiographic parameters have provided tools for screening athletes and can guide return-to-play decisions. Future research regarding appropriate screening practices for athletes with reoccurring stingers, use of protective equipment, and rehabilitation strategies are needed to identify predisposing factors, mitigate the risk of injury, and restore full functional strength and ability.

Neck Injuries

Neck injuries are relatively uncommon but have the potential to cause serious and permanent disability. In athletes, injuries are most common in contact sports, and occur with direct axial loading with a forward-flexed neck. Soft tissue and peripheral nerve injuries are typically minor and self-limiting, with excellent recovery potential and return to activities based on symptoms. Concern for devastating spinal cord injuries has led to routine immobilization using spine boards and hard cervical collars. This approach may provide more harm than benefit when applied universally, and a more commonsense protocol can be used to better address potential neck injuries.

Preventing Catastrophic Injury and Death in Collegiate Athletes: Interassociation Recommendations Endorsed by 13 Medical and Sports Medicine Organisations

The Second Safety in College Football Summit resulted in interassociation consensus recommendations for three paramount safety issues in collegiate athletics: (1) independent medical care for collegiate athletes; (2) diagnosis and management of sport-related concussion; and (3) year-round football practice contact for collegiate athletes. This document, the fourth arising from the 2016 event, addresses the prevention of catastrophic injury, including traumatic and non-traumatic death, in collegiate athletes. The final recommendations in this document are the result of presentations and discussions on key items that occurred at the summit. After those presentations and discussions, endorsing organisation representatives agreed on 18 foundational statements that became the basis for this consensus paper that has been subsequently reviewed by relevant stakeholders and endorsing organisations. This is the final endorsed document for preventing catastrophic injury and death in collegiate athletes. This document is divided into the following components. (1) Background-this section provides an overview of catastrophic injury and death in collegiate athletes. (2) Interassociation recommendations: preventing catastrophic injury and death in collegiate athletes-this section provides the final recommendations of the medical organisations for preventing catastrophic injuries in collegiate athletes. (3) Interassociation recommendations: checklist-this section provides a checklist for each member school. The checklist statements stem from foundational statements voted on by representatives of medical organisations during the summit, and they serve as the primary vehicle for each member school to implement the prevention recommendations. (4) References-this section provides the relevant references for this document. (5) Appendices-this section lists the foundational statements, agenda, summit attendees and medical organisations that endorsed this document.

Preventing catastrophic injury and death in collegiate athletes: interassociation recommendations endorsed by 13 medical and sports medicine organisations

The following organisations endorsed this document: American Association of Neurological Surgeons, American Medical Society for Sports Medicine, American Orthopaedic Society for Sports Medicine, American Osteopathic Academy of Sports Medicine, College Athletic Trainers' Society, Collegiate Strength and Conditioning Coaches Association, Congress of Neurological Surgeons, Korey Stringer Institute, National Athletic Trainers' Association, National Strength and Conditioning Association, National Operating Committee for Standards on Athletic Equipment, Sports Neuropsychology Society. The following organisation has affirmed the value of this document: American Academy of Neurology. The Second Safety in College Football Summit resulted in interassociation consensus recommendations for three paramount safety issues in collegiate athletics: (1) independent medical care for collegiate athletes; (2) diagnosis and management of sport-related concussion; and (3) year-round football practice contact for collegiate athletes. This document, the fourth arising from the 2016 event, addresses the prevention of catastrophic injury, including traumatic and non-traumatic death, in collegiate athletes. The final recommendations in this document are the result of presentations and discussions on key items that occurred at the summit. After those presentations and discussions, endorsing organisation representatives agreed on 18 foundational statements that became the basis for this consensus paper that has been subsequently reviewed by relevant stakeholders and endorsing organisations. This is the final endorsed document for preventing catastrophic injury and death in collegiate athletes. This document is divided into the following components. (1) Background-this section provides an overview of catastrophic injury and death in collegiate athletes. (2) Interassociation recommendations: preventing catastrophic injury and death in collegiate athletes-this section provides the final recommendations of the medical organisations for preventing catastrophic injuries in collegiate athletes. (3) Interassociation recommendations: checklist-this section provides a checklist for each member school. The checklist statements stem from foundational statements voted on by representatives of medical organisations during the summit, and they serve as the primary vehicle for each member school to implement the prevention recommendations. (4) References-this section provides the relevant references for this document. (5) Appendices-this section lists the foundational statements, agenda, summit attendees and medical organisations that endorsed this document.

On the relative importance of bending and compression in cervical spine bilateral facet dislocation

BACKGROUND

Cervical bilateral facet dislocations are among the most devastating spine injuries in terms of likelihood of severe neurological sequelae. More than half of patients with tetraparesis had sustained some form of bilateral facet fracture dislocation. They can occur at any level of the sub-axial cervical spine, but predominate between C5 and C7. The mechanism of these injuries has long been thought to be forceful flexion of the chin towards the chest. This "hyperflexion" hypothesis comports well with intuition and it has become dogma in the clinical literature. However, biomechanical studies of the human cervical spine have had little success in producing this clinically common and devastating injury in a flexion mode of loading.

METHODS

The purpose of this manuscript is to review the clinical and engineering literature on the biomechanics of bilateral facet dislocations and to describe the mechanical reasons for the causal role of compression, and the limited role of head flexion, in producing bilateral facet dislocations.

FINDINGS

Bilateral facet dislocations have only been produced in experiments where compression is the primary loading mode. To date, no biomechanical study has produced bilateral facet dislocations in a whole spine by bending. Yet the notion that it is primarily a hyper-flexion injury persists in the clinical literature.

INTERPRETATION

Compression and compressive buckling are the primary causes of bilateral facet dislocations. It is important to stop using the hyper-flexion nomenclature to describe this class of cervical spines injuries because it may have a detrimental effect on designs for injury prevention.

A novel helmet-mounted device for reducing the potential of catastrophic cervical spine fractures and spinal cord injuries in head-first impacts

BACKGROUND

Head-first impacts with an aligned cervical spine cause some of the most severe types of injuries due to the risk of fractures and associated spinal cord injury. Sports, such as football, mountain biking and horseback riding, contribute to the incidence of spinal cord injury but there is potential to reduce the risk of these injuries through a helmet-mounted device.

METHODS

A novel device, the Pro-Neck-Tor mechanism, was incorporated into a commercial football helmet and tested in head-first impact experiments. The Pro-Neck-Tor connects an inner and outer helmet shell, which upon head-first impact of a certain load, induces motion of the head away from the path of the following torso. Impacts were performed onto three impact surface angles with a flexion-inducing Pro-Neck-Tor mechanism.

FINDINGS

Based on averaged data, the Pro-Neck-Tor provided a significant and consistent reduction in peak compressive neck forces compared to the unmodified football helmet in the conditions tested. In some impact conditions, the Pro-Neck-Tor increased the peak sagittal plane neck bending moments and impulse over that observed for the unmodified helmet.

INTERPRETATION

The Pro-Neck-Tor with flexion escape is capable of lowering axial neck forces in head-first impacts compared to a conventional helmet by guiding the cervical column away from an aligned posture and into an eccentric loading scenario which published studies suggests frequently leads to no injury or to a less severe injury. Continued development and testing of the device are needed to optimize the altered neck loading and to drive the design toward a commercial configuration.

Effect of the PreBind Engagement Process on Scrum Timing and Stability in the 2013-16 Six Nations

This study examined whether changes in scrum engagement laws from the "crouch-touch-set" in 2013 to the "PreBind" engagement from 2014 onward have led to changes in scrum characteristics, specifically timing, in international rugby union. Duration and outcomes were identified for all scrums occurring in the 2013-16 Six Nations (N = 60 games) using video analysis. Scrum duration increased after the introduction of the PreBind engagement from 59 s in 2013 to 69 s in 2016 (P = .024, effect size = 0.93). A significant increase in mean contact duration per scrum occurred when prebinding was adopted (P < .05), moving from 7.5 s under the crouch-touch-set process to 8.5, 10.0, and 10.8 s with PreBind in 2014, 2015, and 2016 (effect size = 0.71, 2.05, and 3.0, respectively). The number of scrum resets and collapsed scrums, along with early engagement and pulling down infringements, was lower under the PreBind process. Overall, the PreBind engagement resulted in longer scrums with significant increases observed in overall and contact durations, with improved stability-related characteristics. The longer contact time is a consequence of increased stability with a shift from high-energy impact to a sustained push phase with a lower force that is a benefit to player welfare.

A novel Cervical Spine Protection device for reducing neck injuries in contact sports: design concepts and preliminary in vivo testing

Head and neck injuries are common in contact sports such as American football. Different mechanisms can produce such injuries, including compressive impact forces on the crown of the helmet with the neck in a flexed chin-down position. The aim of this paper was developing and testing a novel Cervical Spine Protection Device (CSPD) designed to keep the neck within its safe physiological range. The cervical spine range of motion (ROM) of ten participants was measured under four conditions: free; wearing a football gear; wearing the CSPD; and wearing the CSPD underneath the gear. The CSPD was tested in terms of passive and active restraint of head motion, and for its capability to improve endurance time of the neck extensor muscles. Wearing the CSPD resulted in a significant 40-60% reduction in ROM across the three anatomical planes, and in increased endurance of the neck extensor muscles (FREE: 114 ± 57 s; CSPD: 214 ± 95 s; p = 0.004). In quasi-static loading conditions the CSPD was capable of keeping the neck within its physiological range, thus it may be used to decrease the risk of severe injuries due to dangerous chin-down positions.

Acute Thoracolumbar Spinal Cord Injury: Relationship of Cord Compression to Neurological Outcome

BACKGROUND

Spinal cord injury in the cervical spine is commonly accompanied by cord compression and urgent surgical decompression may improve neurological recovery. However, the extent of spinal cord compression and its relationship to neurological recovery following traumatic thoracolumbar spinal cord injury is unclear. The purpose of this study was to quantify maximum cord compression following thoracolumbar spinal cord injury and to assess the relationship among cord compression, cord swelling, and eventual clinical outcome.

METHODS

The medical records of patients who were 15 to 70 years of age, were admitted with a traumatic thoracolumbar spinal cord injury (T1 to L1), and underwent a spinal surgical procedure were examined. Patients with penetrating injuries and multitrauma were excluded. Maximal osseous canal compromise and maximal spinal cord compression were measured on preoperative mid-sagittal computed tomography (CT) scans and T2-weighted magnetic resonance imaging (MRI) by observers blinded to patient outcome. The American Spinal Injury Association (ASIA) Impairment Scale (AIS) grades from acute hospital admission (≤24 hours of injury) and rehabilitation discharge were used to measure clinical outcome. Relationships among spinal cord compression, canal compromise, and initial and final AIS grades were assessed via univariate and multivariate analyses.

RESULTS

Fifty-three patients with thoracolumbar spinal cord injury were included in this study. The overall mean maximal spinal cord compression (and standard deviation) was 40% ± 21%. There was a significant relationship between median spinal cord compression and final AIS grade, with grade-A patients (complete injury) exhibiting greater compression than grade-C and D patients (incomplete injury) (p < 0.05). Multivariate logistic regression identified mean spinal cord compression as independently influencing the likelihood of complete spinal cord injury (p < 0.01).

CONCLUSIONS

Traumatic thoracolumbar spinal cord injury is commonly accompanied by substantial cord compression. Greater cord compression is associated with an increased likelihood of severe neurological deficits (complete injury) following thoracolumbar spinal cord injury.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Cervical spine trauma: prevention strategies

Participation in any sport activity carries risk of cervical spine trauma, but certain activities have a higher risk than others, and hence, demand concerted efforts in developing prevention strategies. Prevention often includes efforts surrounding education of stakeholders, creating or modifying rules, and specific policies adopted for decreasing such risk. Stakeholders include sport clinicians, participants, coaches, parents, league administrators, officials, and the public. Thus, both athlete-specific and setting-specific factors must be considered and controlled to the extent possible for a multipronged approach for decreasing cervical spine injury risk. The effectiveness of certain strategies put into place in collision sports, such as American football, rugby, and ice hockey, is reviewed to illustrate this approach. Some research evidence exists that either has informed a strategy, or validated its effectiveness after the fact. More research of a higher level needs to be conducted in all sports to continue to contain the risk of cervical spine trauma to the fullest extent possible.

Management of Isolated Atlas Fractures: A Retrospective Study of 65 Patients

BACKGROUND

Jefferson fractures, or burst fractures of the C1 vertebra, can be managed surgically or conservatively, depending on their stability.

METHODS

We identified all patients who were treated for a C1 fracture at our institution between 1999 and 2016 for retrospective analysis. Patients with any other concurrent cervical fractures or nontraumatic etiology of fracture were excluded. Stability was defined as either lateral mass displacement ≥7 mm on computed tomography or presence of transverse atlantal ligament disruption on magnetic resonance imaging. We collected data on patients' demographic, clinical, and radiographic presentation and identified variables independently associated with instability at presentation and failure to achieve fusion at follow-up.

RESULTS

We identified 65 patients. On multivariable regression, instability at presentation was independently associated with atlantodens interval (odds ratio [OR] 2.357, 95% confidence interval [CI] [0.0629-1.271], P = 0.099) and type 3 fracture (OR 6.081, 95% CI [1.068-34.612], P = 0.042). Failure to achieve fusion was independently associated with age (OR 1.226, 95% CI [1.007-1.495], P = 0.043), motor vehicle collision as mechanism of injury (OR 22834.3, 95% CI [3.135-1.66e8], P = 0.027), and type 2 fracture (OR 168.537, 95% CI [1.743-16292.92], P = 0.028). Type 3 fracture was positively associated with halo vest for management (OR 17.171, 95% CI [2.882-102.289], P = 0.002) and negatively associated with a rigid cervical collar for management (OR 0.0616, 95% CI [0.0104-0.3653], P = 0.002). All 4 patients who underwent surgery presented with unstable fracture (P = 0.0187).

CONCLUSIONS

Atlantodens interval, mechanism of injury, and fracture type affect Jefferson fracture management decisions and outcomes, including instability at presentation and fusion at follow-up. Most fractures were managed nonsurgically regardless of stability.

Radiological Changes in the Cervical Spine in Freshman Collegiate Sumo Wrestlers

BACKGROUND

Sumo has long been a traditional sport in Japan and is rapidly attracting enthusiasts abroad. Sumo wrestling entails a risk of impact to the cervical spine during an initial charge. Few reports are available in the English-language literature regarding radiological changes in the cervical spine in sumo wrestlers.

PURPOSE

To examine radiological changes in the cervical spine in freshmen collegiate sumo wrestlers.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A total of 53 freshmen sumo wrestlers (age, 18-19 years) who belonged to the Japan Sumo Federation underwent routine radiographic examination of the cervical spine and completed questionnaires on cervical symptoms.

RESULTS

Of the 53 wrestlers, 81% showed loss of lordosis, 45% showed osteophyte formation (mainly at C3-C4), 11% showed disc space narrowing (mainly at C5-C6), and 51% showed narrowing of the cervical nerve root foramina (mainly at C3-C4). Fifty-one percent had some cervical symptoms. A correlation was found between deformity of the cervical bodies (such as intervertebral disc ballooning) and cervical symptoms, but no correlation was found between cervical degenerative changes and cervical symptoms.

CONCLUSION

Our data suggest that loss of lordosis, osteophyte formation, and narrowing of the cervical nerve root foramina at C3-C4 were frequently present in freshmen wrestlers and may be due to the axial load incurred prior to their collegiate careers.

Traumatic Sports-Related Cervical Spine Injuries

Cervical spine trauma in the athlete is not an insignificant occurrence with possibly catastrophic results. Football remains one of the most common and most well studied sporting activities associated with spine injuries. Transient spinal cord and peripheral nerve injuries may manifest as quadriparesis or burners/stingers with symptoms that resolve completely. More severe spinal cord injuries, typically from axial loading on the cervical spine, will cause bilateral symptoms with residual neurological deficit. Acute Trauma Life Support principles must always be applied to the player with a potential spine injury. Recent positional statements by National Athletic Trainers' Association advocate equipment removal on the field by 3 individuals with appropriate training, a shift from previous recommendations. This recommendation is still under debate, but equipment removal in the field is an option depending on staff training. The use of steroids in acute spinal cord injury remains controversial. Moderate systemic hypothermia has theoretical benefits for reducing spinal cord damage in the setting of an acute injury. Although it has been studied in the laboratory, only a few clinical trials have been performed and further research is necessary before routine implementation of hypothermia protocols.

The Influence of Friction Between Football Helmet and Jersey Materials on Force: A Consideration for Sport Safety

CONTEXT

The pocketing effect of helmet padding helps to dissipate forces experienced by the head, but if the player's helmet remains stationary in an opponent's shoulder pads, the compressive force on the cervical spine may increase.

OBJECTIVE

To (1) measure the coefficient of static friction between different football helmet finishes and football jersey fabrics and (2) calculate the potential amount of force on a player's helmet due to the amount of friction present.

DESIGN

Cross-sectional study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

Helmets with different finishes and different football jersey fabrics.

MAIN OUTCOME MEASURE(S)

The coefficient of friction was determined for 2 helmet samples (glossy and matte), 3 football jerseys (collegiate, high school, and youth), and 3 types of jersey numbers (silkscreened, sublimated, and stitched on) using the TAPPI T 815 standard method. These measurements determined which helmet-to-helmet, helmet-to-jersey number, and helmet-to-jersey material combination resulted in the least amount of static friction.

RESULTS

The glossy helmet versus glossy helmet combination produced a greater amount of static friction than the other 2 helmet combinations (P = .013). The glossy helmet versus collegiate jersey combination produced a greater amount of static friction than the other helmet-to-jersey material combinations (P < .01). The glossy helmet versus silkscreened numbers combination produced a greater amount of static friction than the other helmet-to-jersey number combinations (P < .01).

CONCLUSIONS

The force of static friction experienced during collisions can be clinically relevant. Conditions with higher coefficients of static friction result in greater forces. In this study, the highest coefficient of friction (glossy helmet versus silkscreened number) could increase the forces on the player's helmet by 3553.88 N when compared with other helmet-to-jersey combinations. Our results indicate that the makeup of helmet and uniform materials may affect sport safety.

Return-to-Play Recommendations After Cervical, Thoracic, and Lumbar Spine Injuries: A Comprehensive Review

CONTEXT

Currently, there is a national focus on establishing and disseminating standardized guidelines for return to play for athletes at all levels of competition. As more data become available, protocols and guidelines are being refined and implemented to assist physicians, coaches, trainers, players, and parents in making decisions about return to play. To date, no standardized criteria for returning to play exist for injuries to the spine.

EVIDENCE ACQUISITION

Electronic databases including PubMed and MEDLINE and professional orthopaedic, neurosurgical, and spine organizational websites were reviewed between 1980 and 2015.

STUDY DESIGN

Clinical review.

LEVEL OF EVIDENCE

Level 4.

RESULTS

Although clinical guidelines have been published for return to play after spine injury, they are almost exclusively derived from expert opinion and clinical experience rather than from well-designed studies. Furthermore, recommendations differ and vary depending on anatomic location, type of sport, and surgery performed.

CONCLUSION

Despite a lack of consensus and specific recommendations, there is universal agreement that athletes should be pain free, completely neurologically intact, and have full strength and range of motion before returning to play after spinal injury.

The envelope of motion of the cervical spine and its influence on the maximum torque generating capability of the neck muscles

The posture of the head and neck is critical for predicting and assessing the risk of injury during high accelerations, such as those arising during motor accidents or in collision sports. Current knowledge suggests that the head's range-of-motion (ROM) and the torque-generating capability of neck muscles are both dependent and affected by head posture. A deeper understanding of the relationship between head posture, ROM and maximum torque-generating capability of neck muscles may help assess the risk of injury and develop means to reduce such risks. The aim of this study was to use a previously-validated device, known as Neck Flexibility Tester, to quantify the effects of head's posture on the available ROM and torque-generating capability of neck muscles. Ten young asymptomatic volunteers were enrolled in the study. The tri-axial orientation of the subjects' head was controlled via the Neck Flexibility Tester device. The head ROM was measured for each flexed, extended, axially rotated, and laterally bent head's orientation and compared to that in unconstrained neutral posture. Similarly, the torque applied about the three anatomical axes during Isometric Maximum Voluntary Contraction (IMVC) of the neck muscles was measured in six head's postures and compared to that in fully-constrained neutral posture. The further from neutral the neck posture was the larger the decrease in ROM and IMVC. Head extension and combined two-plane rotations postures, such as extension with lateral bending, produced the largest decreases in ROM and IMVC, thus suggesting that these postures pose the highest potential risk for injury.

Significance of T2 Hyperintensity on Magnetic Resonance Imaging After Cervical Cord Injury and Return to Play in Professional Athletes

BACKGROUND:

Cervical cord magnetic resonance imaging (MRI) T2 hyperintensity is used as evidence of cord trauma in the evaluation and management of athletes in contact sports. The long-term pathophysiologic and prognostic value of this finding is poorly understood, especially in return to play (RTP).

OBJECTIVE:

To examine the significance of T2 hyperintensity in the cervical spinal cord of professional athletes.

METHODS:

Retrospective review of MRI T2 hyperintensity findings between 2007 and 2014 in 5 professional athletes. Pertinent examination and demographics, including mechanism of injury, surgical intervention, radiographs, MRI studies, long-term outcomes, and RTP recommendations were collected.

RESULTS:

Four National Football League players and 1 professional wrestler had prior traumatic neurapraxia that at the time of initial consultation had resolved. MRIs showed congenitally small cervical canal (1) and multilevel spondylosis/stenosis/disc herniation (4) along with focal cord T2 hyperintensity (5). The signal abnormalities were at C3/C4 (3), C4 mid-vertebral body (1), and C5/C6 (1). Four athletes had single-level anterior cervical discectomy and fusion, and 1 was nonoperative. Serial MRI imaging at 3 months after surgery showed hyperintensity partially resolved (4) and unchanged (1), and at 9-months 3 of the 5 completely resolved. Based on the author's RTP criteria, 4 of 5 were released to return to their sport. Clearance for RTP preceded complete resolution of MRI T2 hyperintensity in 3 of 4 athletes. The 2 athletes that have returned to profession sport have not had any additional episodes of neurapraxia or any cervical spine-related complications.

CONCLUSION:

MRI T2 hyperintensity in contact sport athletes who are symptom-free with normal examination and no evidence of spinal instability may not be a contraindication to RTP. Additional observations are needed to confirm this observation.

Compressive follower load influences cervical spine kinematics and kinetics during simulated head-first impact in an in vitro model

Current understanding of the biomechanics of cervical spine injuries in head-first impact is based on decades of epidemiology, mathematical models, and in vitro experimental studies. Recent mathematical modeling suggests that muscle activation and muscle forces influence injury risk and mechanics in head-first impact. It is also known that muscle forces are central to the overall physiologic stability of the cervical spine. Despite this knowledge, the vast majority of in vitro head-first impact models do not incorporate musculature. We hypothesize that the simulation of the stabilizing mechanisms of musculature during head-first osteoligamentous cervical spine experiments will influence the resulting kinematics and injury mechanisms. Therefore, the objective of this study was to document differences in the kinematics, kinetics, and injuries of ex vivo osteoligamentous human cervical spine and surrogate head complexes that were instrumented with simulated musculature relative to specimens that were not instrumented with musculature. We simulated a head-first impact (3 m/s impact speed) using cervical spines and surrogate head specimens (n = 12). Six spines were instrumented with a follower load to simulate in vivo compressive muscle forces, while six were not. The principal finding was that the axial coupling of the cervical column between the head and the base of the cervical spine (T1) was increased in specimens with follower load. Increased axial coupling was indicated by a significantly reduced time between head impact and peak neck reaction force (p = 0.004) (and time to injury (p = 0.009)) in complexes with follower load relative to complexes without follower load. Kinematic reconstruction of vertebral motions indicated that all specimens experienced hyperextension and the spectrum of injuries in all specimens were consistent with a primary hyperextension injury mechanism. These preliminary results suggest that simulating follower load that may be similar to in vivo muscle forces results in significantly different impact kinetics than in similar biomechanical tests where musculature is not simulated.

Cervical spine instability following axial compression injury: a biomechanical study

BACKGROUND

Axial compression injuries of the cervical spine occur during contact sports, automobile collisions, and falls. The objective of this study was to use flexibility tests to determine biomechanical instability of the cervical spine due to simulated axial compression injuries.

HYPOTHESIS

We hypothesized that the axial compression injuries cause severe biomechanical instability throughout the cervical spine.

MATERIALS AND METHODS

The injuries were simulated using 2.4m/s head-first impacts of a cadaveric cervical spine model (n=10) mounted horizontally to a torso-equivalent mass on a sled and carrying a surrogate head in protruded posture. Intact and post-impact flexibility tests were performed up to 1.5, 3, and 1.5 Nm in flexion-extension, axial torque, and lateral bending, respectively. Instability parameters of range of motion (RoM) and neutral zone (NZ) were determined for injured spinal levels and statistically compared (P<0.05) between intact and post-impact.

RESULTS

The sagittal instability parameters indicated extension-compression injuries at the upper and middle cervical spine and flexion-compression injuries at the lower cervical spine. Increases in extension RoM were 14.9° at the upper cervical spine and 24.9° (P<0.05) at the middle cervical spine and in flexion RoM at C7/T1 were 25.6°. RoM and NZ increases in axial rotation and lateral bending were nearly symmetric among left and right.

DISCUSSION

Multidirectional instability of the upper cervical spine caused by atlas and dens fractures was evidenced by increases between 36% and 53% in RoM and NZ due to the impacts. The sagittal RoM of injured spinal levels of the middle and lower cervical spine exceeded a proposed threshold for clinical instability by between 67% and 114%. The instability documented throughout the cervical spine was consistent with clinical observations of cord injuries and paralysis in patients.

LEVEL OF EVIDENCE

Level IV, controlled laboratory investigation.

Injury and biomechanical perspectives on the rugby scrum: a review of the literature

As a collision sport, rugby union has a relatively high overall injury incidence, with most injuries being associated with contact events. Historically, the set scrum has been a focus of the sports medicine community due to the perceived risk of catastrophic spinal injury during scrummaging. The contemporary rugby union scrum is a highly dynamic activity but to this point has not been well characterised mechanically. In this review, we synthesise the available research literature relating to the medical and biomechanical aspects of the rugby union scrum, in order to (1) review the injury epidemiology of rugby scrummaging; (2) consider the evidence for specific injury mechanisms existing to cause serious scrum injuries and (3) synthesise the information available on the biomechanics of scrummaging, primarily with respect to force production. The review highlights that the incidence of acute injury associated with scrummaging is moderate but the risk per event is high. The review also suggests an emerging acknowledgement of the potential for scrummaging to lead to premature chronic degeneration injuries of the cervical spine and summarises the mechanisms by which these chronic injuries are thought to occur. More recent biomechanical studies of rugby scrummaging confirm that scrum engagement forces are high and multiplanar, but can be altered through modifications to the scrum engagement process which control the engagement velocity. As the set scrum is a relatively 'controlled' contact situation within rugby union, it remains an important area for intervention with a long-term goal of injury reduction.

The Hybrid III upper and lower neck response in compressive loading scenarios with known human injury outcomes

OBJECTIVE

Physical biomechanical surrogates are critical for testing the efficacy of injury-mitigating safety strategies. The interpretation of measured Hybrid III neck loads in test scenarios resulting in compressive loading modes would be aided by a further understanding of the correlation between the mechanical responses in the Hybrid III neck and the probability of injury in the human cervical spine. The anthropomorphic test device (ATD) peak upper and lower neck responses were measured during dynamic compressive loading conditions comparable to those of postmortem human subject (PMHS) experiments. The peak ATD response could then be compared to the PMHS injury outcomes.

METHODS

A Hybrid III 50th percentile ATD head and neck assembly was tested under conditions matching those of male PMHS tests conducted on an inverted drop track. This includes variation in impact plate orientation (4 sagittal plane and 2 frontal plane orientations), impact plate surface friction, and ATD initial head/neck orientation. This unique matched data with known injury outcomes were used to evaluate existing ATD neck injury criteria.

RESULTS

The Hybrid III ATD head and neck assembly was found to be robust and repeatable under severe loading conditions. The initial axial force response of the ATD head and neck is very comparable to PMHS experiments up to the point of PMHS cervical column buckle or material failure. An ATD lower neck peak compressive force as low as 6,290 N was associated with an unstable orthopedic cervical injury in a PMHS under equivalent impact conditions. ATD upper neck peak compressive force associated with a 5% probability of unstable cervical orthopedic injury ranged from as low as 3,708 to 3,877 N depending on the initial ATD neck angle.

CONCLUSIONS

The correlation between peak ATD compressive neck response and PMHS test outcome in the current study resulted in a relationship between axial load and injury probability consistent with the current Hybrid III injury assessment reference values. The results add to the current understanding of cervical injury probability based on ATD neck compressive loading in that it is the only known study, in addition to Mertz et al. (1978), formulated directly from ATD compressive loading scenarios with known human injury outcomes.

Catastrophic head and neck injuries in judo players in Japan from 2003 to 2010

BACKGROUND

Few studies have documented catastrophic head and neck injuries in judo, but these injuries deserve greater attention.

PURPOSE

To determine the features of catastrophic head and neck injuries in judo.

STUDY DESIGN

Descriptive epidemiological study.

METHODS

This study was based on the accident reports submitted to the All Japan Judo Federation's System for Compensation for Loss or Damage. A total of 72 judo injuries (30 head, 19 neck, and 23 other injuries) were reported between 2003 and 2010. The investigated parameters were mechanism of injury, age at time of injury, length of judo experience, diagnosis, and outcome.

RESULTS

Among head injuries, 27 of 30 (90%) occurred in players younger than 20 years of age. The relationship between age, mechanism, and location of injury was more relevant when players younger than 20 years incurred head injury while being thrown (P = .0026). Among neck injuries, 13 of 19 (68%) occurred in players with more than 36 months of experience. The relationship between experience, mechanism, and location of injury was more relevant when experienced players incurred neck injury while executing an offensive maneuver (P = .0294). Acute subdural hematoma was diagnosed in 94% of head injuries. The outcomes of head injury were as follows: 15 players died; 5 were in a persistent vegetative state; 6 required assistance because of higher brain dysfunction, hemiplegia, or aphasia; and 4 had full recovery. Among neck injuries, 18 players were diagnosed with cervical spine injury, 11 of whom had fracture-dislocation of the cervical vertebra; there was also 1 case of atlantoaxial subluxation. The outcomes of neck injury were as follows: 7 players had complete paralysis, 7 had incomplete paralysis, and 5 had full recovery.

CONCLUSION

Neck injuries were associated with having more experience and executing offensive maneuvers, whereas head injuries were associated with age younger than 20 years and with being thrown.

Toward a more robust lower neck compressive injury tolerance-an approach combining multiple test methodologies

OBJECTIVE

The compressive tolerance of the cervical spine has traditionally been reported in terms of axial force at failure. Previous studies suggest that axial compressive force at failure is particularly sensitive to the alignment of the cervical vertebra and the end conditions of the test methodology used. The present study was designed to develop a methodology to combine the data of previous experiments into a diverse data set utilizing multiple test methods to allow for the evaluation of the robustness of current and proposed eccentricity based injury criteria.

METHODS

Data were combined from 2 studies composed of dynamic experiments including whole cervical spine and head kinematics that utilized different test methodologies with known end conditions, spinal posture, injury outcomes, and measured kinetics at the base of the neck. Loads were transformed to the center of the C7-T1 intervertebral disc and the eccentricity of the sagittal plane resultant force relative to the center of the disc was calculated. The correlation between sagittal plane resultant force and eccentricity at failure was evaluated and compared to the correlation between axial force and sagittal plane moment and axial force alone.

RESULTS

Accounting for the eccentricity of the failure loads decreased the scatter in the failure data when compared to the linear combination of axial force and sagittal plane moment and axial force alone. A correlation between axial load and sagittal plane flexion moment at failure (R² = 0.44) was identified. The sagittal plane extension moment at failure did not have an identified correlation with the compressive failure load for the tests evaluated in this data set (R² = 0.001). The coefficients of determination for the linear combinations of sagittal plane resultant force with anterior and posterior eccentricity are 0.56 and 0.29, respectively. These correlations are an improvement compared to the combination of axial force and sagittal plane moment.

CONCLUSIONS

Results using the outlined approach indicate that the combination of lower neck sagittal plane resultant force and the anterior-posterior eccentricity at which the load is applied generally correlate with the type of cervical damage identified. These results show promise at better defining the tolerance for compressive cervical fractures in male postmortem human subjects (PMHS) than axial force alone. The current analysis requires expansion to include more tolerance data so the robustness of the approach across various applied loading vectors and cervical postures can be evaluated.

Performance analysis of the protective effects of bicycle helmets during impact and crush tests in pediatric skull models

OBJECT

Bicycle accidents are a very important cause of clinically important traumatic brain injury (TBI) in children. One factor that has been shown to mitigate the severity of lesions associated with TBI in such scenarios is the proper use of a helmet. The object of this study was to test and evaluate the protection afforded by a children's bicycle helmet to human cadaver skulls with a child's anthropometry in both "impact" and "crushing" situations.

METHODS

The authors tested human skulls with and without bicycle helmets in drop tests in a monorail-guided free-fall impact apparatus from heights of 6 to 48 in onto a flat steel anvil. Unhelmeted skulls were dropped at 6 in, with progressive height increases until failure (fracture). The maximum resultant acceleration rates experienced by helmeted and unhelmeted skulls on impact were recorded by an accelerometer attached to the skulls. In addition, compressive forces were applied to both helmeted and unhelmeted skulls in progressive amounts. The tolerance in each circumstance was recorded and compared between the two groups.

RESULTS

Helmets conferred up to an 87% reduction in so-called mean maximum resultant acceleration over unhelmeted skulls. In compression testing, helmeted skulls were unable to be crushed in the compression fixture up to 470 pound-force (approximately 230 kgf), whereas both skull and helmet alone failed in testing.

CONCLUSIONS

Children's bicycle helmets provide measurable protection in terms of attenuating the acceleration experienced by a skull on the introduction of an impact force. Moreover, such helmets have the durability to mitigate the effects of a more rare but catastrophic direct compressive force. Therefore, the use of bicycle helmets is an important preventive tool to reduce the incidence of severe associated TBI in children as well as to minimize the morbidity of its neurological consequences.

Cervical spine immobilization in sports related injuries: review of current guidelines and a case study of an injured athlete

Cervical spine immobilization is an essential component of the ATLS^® system. Inadequate training in the management of trauma calls and failure of early recognition can have disastrous consequences. Pre-hospital personnel are routinely involved more in the assessment and stabilization of patients in comparison to other health care professionals.

This case study and review highlights the importance of early recognition, assessment and correct stabilization of cervical spine injuries both in the field and during the initial assessment in hospital.

Inadequate assessment, immobilization and lack of standard guidelines on the management of suspected cervical spine trauma can result in secondary injury. Regular assessment and training of pre-hospital and medical personnel is essential to the proper management of these potentially devastating injuries.

Cervical spine injuries and the return to football

Background:

The literature dealing with the diagnosis and treatment of cervical spine injuries is considerable. Absent, however, are comprehensive criteria or guidelines for permitting or prohibiting return to collusion activities such as tackle football.

Objective:

The purpose of this report is to describe developmental and posttraumatic conditions of the cervical spine as presenting (1) no contraindication, (2) relative contraindication, or (3) an absolute contraindication to continued participation in tackle football and other contact activities.

Study Design:

Systematic review.

Methods:

Analysis of data compiled from more than 1200 cervical spine injuries documented by the National Football Head and Neck Registry, in addition to a review of the limited published literature, plus an understanding of the recognized axial load injury mechanism and extensive anecdotal experience.

Conclusion:

The one overriding principle regarding the return to football or, for that matter, any collusion activity is that the individual be asymptomatic, pain-free, and neurologically intact and have full strength and full range of cervical motion.

Biomechanics of sports-induced axial-compression injuries of the neck

CONTEXT

Head-first sports-induced impacts cause cervical fractures and dislocations and spinal cord lesions. In previous biomechanical studies, researchers have vertically dropped human cadavers, head-neck specimens, or surrogate models in inverted postures.

OBJECTIVE

To develop a cadaveric neck model to simulate horizontally aligned, head-first impacts with a straightened neck and to use the model to investigate biomechanical responses and failure mechanisms.

DESIGN

Descriptive laboratory study.

SETTING

Biomechanics research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Five human cadaveric cervical spine specimens.

INTERVENTION(S)

The model consisted of the neck specimen mounted horizontally to a torso-equivalent mass on a sled and carrying a surrogate head. Head-first impacts were simulated at 4.1 m/s into a padded, deformable barrier.

MAIN OUTCOME MEASURE(S)

Time-history responses were determined for head and neck loads, accelerations, and motions. Average occurrence times of the compression force peaks at the impact barrier, occipital condyles, and neck were compared.

RESULTS

The first local compression force peaks at the impact barrier (3070.0 ± 168.0 N at 18.8 milliseconds), occipital condyles (2868.1 ± 732.4 N at 19.6 milliseconds), and neck (2884.6 ± 910.7 N at 25.0 milliseconds) occurred earlier than all global compression peaks, which reached 7531.6 N in the neck at 46.6 milliseconds (P < .001). Average peak head motions relative to the torso were 6.0 cm in compression, 2.4 cm in posterior shear, and 6.4° in flexion. Neck compression fractures included occipital condyle, atlas, odontoid, and subaxial comminuted burst and facet fractures.

CONCLUSIONS

Neck injuries due to excessive axial compression occurred within 20 milliseconds of impact and were caused by abrupt deceleration of the head and continued forward torso momentum before simultaneous rebound of the head and torso. Improved understanding of neck injury mechanisms during sports-induced impacts will increase clinical awareness and immediate care and ultimately lead to improved protective equipment, reducing the frequency and severity of neck injuries and their associated societal costs.

Head-first impact with head protrusion causes noncontiguous injuries of the cadaveric cervical spine

OBJECTIVE

To simulate horizontally aligned head-first impacts with initial head protrusion using a human cadaveric neck model and to determine biomechanical responses, injuries, and injury severity.

DESIGN

Head-first impacts with initial head protrusion were simulated at 2.4 m/s using a human cadaver neck model (n = 10) mounted horizontally to a torso-equivalent mass on a sled and carrying a surrogate head. Macroscopic neck injuries were determined, and ligamentous injuries were quantified using fluoroscopy and visual inspection after the impacts. Representative time-history responses for injured specimens were determined during impact using load cell data and analyses of high-speed video.

SETTING

Biomechanics research laboratory.

PARTICIPANTS

Cervical spines of 10 human cadavers.

MAIN OUTCOME MEASURES

Injury severity at the middle and lower cervical spine was statistically compared using a 2-sample t test (P < 0.05).

RESULTS

Neck buckling consisted of hyperflexion at C6/7 and C7/T1 and hyperextension at superior spinal levels. Noncontiguous neck injuries included forward dislocation at C7/T1, spinous process fracture and compression-extension injuries at the middle cervical spine, and atlas and odontoid fractures. Ligamentous injury severity at C7/T1 was significantly greater than at the middle cervical spine.

CONCLUSIONS

Distinct injury mechanisms were observed throughout the neck, consisting of extension-compression and posterior shear at the upper and middle cervical spine and flexion-compression and anterior shear at C6/7 and C7/T1. Our experimental results highlight the importance of clinical awareness of potential noncontiguous cervical spine injuries due to head-first sports impacts.

Atlas injury mechanisms during head-first impact

STUDY DESIGN

An in vitro biomechanical study.

OBJECTIVE

To investigate atlas injury mechanisms due to horizontally aligned head-first impacts of a cadaveric neck model and to document atlas fracture patterns and associated injuries.

SUMMARY OF BACKGROUND DATA

Experimental atlas injuries have been created by applying compression or radial forces to isolated C1 vertebrae, dropping weight or applying sagittal moments to the upper cervical spine segments, or vertical drop testing of head-neck specimens or whole cadavers. Atlas injuries that commonly occur due to horizontally aligned head-first impacts have not been previously investigated.

METHODS

Horizontally aligned head-first impacts into a padded barrier were simulated at 4.1 m/s, using a human cadaver neck model mounted horizontally to a torso-equivalent mass on a sled and carrying a surrogate head. Atlantal radial force was computed using head and neck load cell data. Postimpact dissection documented atlas and associated injuries. Average atlantal radial force peaks and their occurrence times were statistically compared (P < 0.05) among the first local and global peaks using paired t tests.

RESULTS

The first average local peak in radial atlantal force was significantly smaller (1240 vs. 2747 N) and occurred significantly earlier (24 ms vs. 46 ms) than the global force peak. Atlas injuries consisted of either 3- or 4-part burst fractures or incomplete lateral mass fracture unilaterally. Associated injuries included bony avulsion of the transverse ligament unilaterally and fractures of the occipital condyles, superior facets of the axis, or odontoid.

CONCLUSION

The results indicated that the varied atlas fracture patterns were due primarily to radial forces causing outward lateral expansion of its lateral masses. Anterior and posterior arch fracture locations are dependent, in part, upon the cross-sectional arch dimensions. Transverse ligament rupture or bony avulsion is likely associated with real-life atlantal burst fractures.

National athletic trainers' association position statement: preventing sudden death in sports

OBJECTIVE

To present recommendations for the prevention and screening, recognition, and treatment of the most common conditions resulting in sudden death in organized sports.

BACKGROUND

Cardiac conditions, head injuries, neck injuries, exertional heat stroke, exertional sickling, asthma, and other factors (eg, lightning, diabetes) are the most common causes of death in athletes.

RECOMMENDATIONS

These guidelines are intended to provide relevant information on preventing sudden death in sports and to give specific recommendations for certified athletic trainers and others participating in athletic health care.

Helmet fit and cervical spine motion in collegiate men's lacrosse athletes secured to a spine board

CONTEXT

Proper management of cervical spine injuries in men's lacrosse players depends in part upon the ability of the helmet to immobilize the head.

OBJECTIVE

To determine if properly and improperly fitted lacrosse helmets provide adequate stabilization of the head in the spine-boarded athlete.

DESIGN

Crossover study.

SETTING

Sports medicine research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Eighteen healthy collegiate men's lacrosse players.

INTERVENTION(S)

Participants were asked to move their heads through 3 planes of motion after being secured to a spine board under 3 helmet conditions.

MAIN OUTCOME MEASURE(S)

Change in range of motion in the cervical spine was calculated for the sagittal, frontal, and transverse planes for both head-to-thorax and helmet-to-thorax range of motion in all 3 helmet conditions (properly fitted, improperly fitted, and no helmet).

RESULTS

Head-to-thorax range of motion with the properly fitted and improperly fitted helmets was greater than in the no-helmet condition (P < .0001). In the sagittal plane, range of motion was greater with the improperly fitted helmet than with the properly fitted helmet. No difference was observed in helmet-to-thorax range of motion between properly and improperly fitted helmet conditions. Head-to-thorax range of motion was greater than helmet-to-thorax range of motion in all 3 planes (P < .0001).

CONCLUSIONS

Cervical spine motion was minimized the most in the no-helmet condition, indicating that in lacrosse players, unlike football players, the helmet may need to be removed before stabilization.