Effect of mouthguards on head responses and mandible forces in football helmet impacts

Mouthguards during orthodontic treatment: Perspectives of orthodontists and a survey of orthodontic patients playing school-sponsored basketball and football

INTRODUCTION

The objectives of this research were to identify the beliefs and practices of orthodontists about mouthguard use in orthodontic patients and to survey orthodontic patients currently playing school-sponsored basketball and/or football about mouthguards.

METHODS

Fifteen orthodontists were interviewed about mouthguard use in their patients. Patients (aged 11-18 years) playing organized school basketball (n = 53) or football (n = 22) from 13 of those 15 orthodontic practices participated in an online survey about mouthguards.

RESULTS

Approximately half of the orthodontists interviewed had initiated discussions about mouthguards with their patients. Although boil-and-bite mouthguards were recommended most often by orthodontists with only a single orthodontist recommending a stock type, stock was the most commonly used type (football [59%], basketball [50%]) followed by boil-and-bite (football [27%], basketball [35%]). Only 2 of the 75 patients surveyed (<3%) reported using a custom mouthguard. All football players reported using a mouthguard, as mandated by this sport. Basketball does not mandate mouthguard use, and only 38% of basketball players reported wearing one. Players who used mouthguards cited forgetting as the most frequent reason for not always using one. A greater percentage of football (91%) than basketball (32%) players reported that their coach recommended a mouthguard (P <0.001).

CONCLUSIONS

Orthodontists differ in how they approach mouthguard use by their patients, which likely reflects a lack of evidence-based guidelines. The beliefs, recommendations, and practices of orthodontists concerning mouthguard use and the use of mouthguards by orthodontic patients are discussed. Research directions to improve mouthguard use are suggested.

Describing headform pose and impact location for blunt impact testing

Reproduction of anthropomorphic test device (ATD) head impact test methods is a critical element needed to develop guidance and technologies that reduce the risk for brain injury in sport. However, there does not appear to be a consensus for reporting ATD pose and impact location for industry and researchers to follow. Thus, the purpose of this article is to explore the various methods used to report impact location and ATD head pose for sport-related head impact testing and provide recommendations for standardizing these descriptions. A database search and exclusion process identified 137 articles that met the review criteria. Only 4 of the 137 articles provided a description similar to the method we propose to describe ATD pose and impact location. We thus propose a method to unambiguously convey the impact location and pose of the ATD based on the sequence, quantifiable design, and articulation of ATD mount joints. This reporting method has been used to a limited extent in the literature, but we assert that adoption of this method will help to standardize the reporting of ATD headform pose and impact location as well as aid in the replication of impact test protocols across laboratories.

Mouthguard use in youth ice hockey and the risk of concussion: nested case–control study of 315 cases

Background

Concussion is the most common injury in youth ice hockey. Whether mouthguard use lowers the odds of concussion remains an unanswered question.

Objective

To determine the association between concussion and mouthguard use in youth ice hockey.

Methods

Nested case–control design. Cases and controls were identified from two prospective cohort studies using valid injury surveillance methods. Cases were players concussed during a game or practice; controls were players who sustained a non-concussion injury during a game or practice. The primary exposure was mouthguard use at time of injury; mouthguard type (dental custom fit or off the shelf) was a secondary exposure. Physician-diagnosed or therapist-suspected concussion was the primary outcome. Dental injury was a secondary outcome. Multilevel logistic regression with random effect at a team level was used to obtain ORs for the mouthguard effect, adjusted for level of play, age group, position, concussion history, mechanism of injury, cohort, session type and body checking policy.

Results

Among cases, 236/315 (75%) were wearing a mouthguard at time of injury, while 224/270 (83%) controls were wearing a mouthguard at time of injury. Any mouthguard use was associated with an adjusted OR for concussion of 0.36 (95% CI 0.17 to 0.73). Off-the-shelf mouthguards were associated with a 69% lower odds of concussion (adjusted OR: 0.31; 95% CI 0.14 to 0.65). Dental custom-fit mouthguards were associated with a non-significant 49% lower odds of concussion (adjusted OR: 0.51; 95% CI 0.22 to 1.10). No dental injuries were identified in either cohort.

Conclusion

Mouthguard use was associated with lower odds of concussion. Players should be required to wear mouthguards in youth ice hockey.

Sports Medicine Update: Concussion

A systematic approach is required for patients with a suspected concussion. Although standardized tools can aid in assessment, the diagnosis of concussion remains a clinical one. At the time of diagnosis, patients should be given both verbal and written review of the common symptoms of concussion, expected course of recovery, as well as strategies to manage symptoms. Most patients benefit from a brief period of rest, followed by a gradual reintroduction of activities, and a graduated return-to-sport protocol. Patients with prolonged recovery from a concussion may benefit from exercise, vestibular, and cognitive rehabilitation programs.

A review of impact testing methods for headgear in sports: Considerations for improved prevention of head injury through research and standards

Standards for sports headgear were introduced as far back as the 1960s and many have remained substantially unchanged to present day. Since this time, headgear has virtually eliminated catastrophic head injuries such as skull fractures and changed the landscape of head injuries in sports. Mild traumatic brain injury (mTBI) is now a prevalent concern and the effectiveness of headgear in mitigating mTBI is inconclusive for most sports. Given that most current headgear standards are confined to attenuating linear head mechanics and recent brain injury studies have underscored the importance of angular mechanics in the genesis of mTBI, new or expanded standards are needed to foster headgear development and assess headgear performance that addresses all types of sport-related head and brain injuries. The aim of this review is to provide a basis for developing new sports headgear impact tests for standards by summarizing and critiquing: 1) impact testing procedures currently codified in published headgear standards for sports and 2) new or proposed headgear impact test procedures in published literature and/or relevant conferences. Research areas identified as needing further knowledge to support standards test development include defining sports-specific head impact conditions, establishing injury and age appropriate headgear assessment criteria, and the development of headgear specific head and neck surrogates for at-risk populations.

Sport-Related Concussion in Children and Adolescents

Sport-related concussion is an important topic in nearly all sports and at all levels of sport for children and adolescents. Concussion knowledge and approaches to management have progressed since the American Academy of Pediatrics published its first clinical report on the subject in 2010. Concussion's definition, signs, and symptoms must be understood to diagnose it and rule out more severe intracranial injury. Pediatric health care providers should have a good understanding of diagnostic evaluation and initial management strategies. Effective management can aid recovery and potentially reduce the risk of long-term symptoms and complications. Because concussion symptoms often interfere with school, social life, family relationships, and athletics, a concussion may affect the emotional well-being of the injured athlete. Because every concussion has its own unique spectrum and severity of symptoms, individualized management is appropriate. The reduction, not necessarily elimination, of physical and cognitive activity is the mainstay of treatment. A full return to activity and/or sport is accomplished by using a stepwise program while evaluating for a return of symptoms. An understanding of prolonged symptoms and complications will help the pediatric health care provider know when to refer to a specialist. Additional research is needed in nearly all aspects of concussion in the young athlete. This report provides education on the current state of sport-related concussion knowledge, diagnosis, and management in children and adolescents.

National Athletic Trainers' Association Position Statement: Preventing and Managing Sport-Related Dental and Oral Injuries

OBJECTIVE

To provide athletic trainers, health care professionals, and all those responsible for the care of athletes with clinical recommendations for preventing and managing sport-related dental and oral injuries.

BACKGROUND

Participation in competitive sports continues to grow at both the interscholastic and intercollegiate levels. Therefore, exposure to, and the incidence of athletic-related injury, including orofacial injury, will also likely increase. At the time of this writing, the leading governing agencies for interscholastic (National Federation of State High School Associations) and intercollegiate (National Collegiate Athletic Association) sports require only protective orofacial equipment (eg, mouthguards) for 5 and 4, respectively, of their sanctioned sports. Although orofacial injuries represent a small percentage of all sport-related injuries, the financial burden associated with these injuries (eg, tooth avulsion) can exceed $15 000 over an adult life. Therefore, effective management of sport-related dental injuries is critical to the long-term financial, physical, and emotional health of people who have experienced dental trauma.

RECOMMENDATIONS

Based upon the current evidence regarding sport-related orofacial injury, we provide recommendations related to planning considerations, education, and mouthguard efficacy, material, fabrication, and care considerations. Additionally, suggested best practices for managing sport-related dental injury are also given for athletic trainers and other health care professionals.

Biomechanical Perspectives on Concussion in Sport

Concussions can occur in any sport. Often, clinical and biomechanical research efforts are disconnected. This review paper analyzes current concussion issues in sports from a biomechanical perspective and is geared toward Sports Med professionals. Overarching themes of this review include the biomechanics of the brain during head impact, role of protective equipment, potential population-based differences in concussion tolerance, potential intervention strategies to reduce the incidence of injury, and common biomechanical misconceptions.

Effect of the mandible on mouthguard measurements of head kinematics

Wearable sensors are becoming increasingly popular for measuring head motions and detecting head impacts. Many sensors are worn on the skin or in headgear and can suffer from motion artifacts introduced by the compliance of soft tissue or decoupling of headgear from the skull. The instrumented mouthguard is designed to couple directly to the upper dentition, which is made of hard enamel and anchored in a bony socket by stiff ligaments. This gives the mouthguard superior coupling to the skull compared with other systems. However, multiple validation studies have yielded conflicting results with respect to the mouthguard׳s head kinematics measurement accuracy. Here, we demonstrate that imposing different constraints on the mandible (lower jaw) can alter mouthguard kinematic accuracy in dummy headform testing. In addition, post mortem human surrogate tests utilizing the worst-case unconstrained mandible condition yield 40% and 80% normalized root mean square error in angular velocity and angular acceleration respectively. These errors can be modeled using a simple spring-mass system in which the soft mouthguard material near the sensors acts as a spring and the mandible as a mass. However, the mouthguard can be designed to mitigate these disturbances by isolating sensors from mandible loads, improving accuracy to below 15% normalized root mean square error in all kinematic measures. Thus, while current mouthguards would suffer from measurement errors in the worst-case unconstrained mandible condition, future mouthguards should be designed to account for these disturbances and future validation testing should include unconstrained mandibles to ensure proper accuracy.

Division I College Football Concussion Rates Are Higher at Higher Altitudes

STUDY DESIGN

Retrospective cohort.

BACKGROUND

Participating in sports at high altitude may have a protective effect on the brain, according to research studies. Research using validated data-collection methods in a previously unexplored cohort may better estimate the association between concussion injury risk and altitude.

OBJECTIVES

To determine the association between concussion rates and altitude during college football games.

METHODS

Athletic trainers from 21 Division I football programs provided exposure and injury data to the National Collegiate Athletic Association (NCAA) Injury Surveillance Program (ISP) from the 2009-2010 to 2013-2014 academic years. The elevation of each stadium was determined. Concussion rates per 1000 athlete-exposures (AEs) were compared in 2 ways, based on the sample of stadium elevations: (1) median split (elevation higher than 178 m or lower than 178 m), and (2) quartile split. Rate ratios (RRs), rate differences, and 95% confidence intervals (CIs) were computed.

RESULTS

One hundred sixty-nine concussions were reported over 49 040 AEs (3.45/1000 AEs). Using the median split, the concussion rate above 178 m (RR = 4.18/1000 AEs) was 1.47 times the concussion rate below 178 m (RR = 2.84/1000 AEs; 95% CI: 1.09, 2.00; P = .01). The concussion rate at the highest altitude quartile (higher than 284 m; RR = 5.01/1000 AEs) was 1.67 times greater than the concussion rate at the lowest altitude quartile (lower than 43 m; RR = 3.00/1000 AEs; 95% CI: 1.13, 2.48; P = .01).

CONCLUSION

College football game concussion rates appear to increase at higher altitudes. The clinical significance of this relatively small increase is unknown. Future research should explore potential physiologic underpinnings associated with concussion risk at relatively higher and lower altitudes.

LEVEL OF EVIDENCE

Prognosis, level 2b.

Laboratory Validation of Two Wearable Sensor Systems for Measuring Head Impact Severity in Football Players

Wearable sensors can measure head impact frequency and magnitude in football players. Our goal was to quantify the impact detection rate and validity of the direction and peak kinematics of two wearable sensors: a helmet system (HITS) and a mouthguard system (X2). Using a linear impactor, modified Hybrid-III headform and one helmet model, we conducted 16 impacts for each system at 12 helmet sites and 5 speeds (3.6-11.2 m/s) (N = 896 tests). Peak linear and angular accelerations (PLA, PAA), head injury criteria (HIC) and impact directions from each device were compared to reference sensors in the headform. Both sensors detected ~96% of impacts. Median angular errors for impact directions were 34° for HITS and 16° for X2. PLA, PAA and HIC were simultaneously valid at 2 sites for HITS (side, oblique) and one site for X2 (side). At least one kinematic parameter was valid at 2 and 7 other sites for HITS and X2 respectively. Median relative errors for PLA were 7% for HITS and -7% for X2. Although sensor validity may differ for other helmets and headforms, our analyses show that data generated by these two sensors need careful interpretation.

Head impact exposure in youth football: middle school ages 12-14 years

The head impact exposure experienced by football players at the college and high school levels has been well documented; however, there are limited data regarding youth football despite its dramatically larger population. The objective of this study was to investigate head impact exposure in middle school football. Impacts were monitored using a commercially available accelerometer array installed inside the helmets of 17 players aged 12-14 years. A total of 4678 impacts were measured, with an average (±standard deviation) of 275 ± 190 impacts per player. The average of impact distributions for each player had a median impact of 22 ± 2 g and 954 ± 122 rad/s², and a 95th percentile impact of 54 ± 9 g and 2525 ± 450 rad/s². Similar to the head impact exposure experienced by high school and collegiate players, these data show that middle school football players experience a greater number of head impacts during games than practices. There were no significant differences between median and 95th percentile head acceleration magnitudes experienced during games and practices; however, a larger number of impacts greater than 80 g occurred during games than during practices. Impacts to the front and back of the helmet were most common. Overall, these data are similar to high school and college data that have been collected using similar methods. These data have applications toward youth football helmet design, the development of strategies designed to limit head impact exposure, and child-specific brain injury criteria.

Head impact exposure in youth football: elementary school ages 7-8 years and the effect of returning players

OBJECTIVE

To provide data describing the head impact exposure of 7- to 8-year-old football players.

DESIGN

Head impact data were collected from 19 players over the course of 2 seasons using helmet-mounted accelerometer arrays.

SETTING

Data were collected from 2 youth football teams in Blacksburg, VA, spanning 2 seasons.

PARTICIPANTS

A total of 19 youth football players aged 7-8 years.

INDEPENDENT VARIABLES

Type of session (practice or game) and the player's experience.

MAIN OUTCOME MEASURES

Head impact frequency, acceleration magnitude, and impact location for games, practices, and the season as a whole were measured.

RESULTS

The average instrumented player sustained 9 ± 6 impacts per practice, 11 ± 11 impacts per game, and 161 ± 111 impacts per season. The average instrumented player had a median impact of 16 ± 2 g and 686 ± 169 rad/s and a 95th percentile impact of 38 ± 13 g and 2052 ± 664 rad/s throughout a season. Impacts of 40 g or greater tended to occur more frequently in practices than in games, and practices had a significantly higher 95th percentile impact magnitude than games (P = 0.023). Returning players had significantly more impacts than first time players (P = 0.007).

CONCLUSIONS

These data are a further step toward developing effective strategies to reduce the incidence of concussion in youth football and have applications toward youth-specific football helmet designs.

A headform for testing helmet and mouthguard sensors that measure head impact severity in football players

A headform is needed to validate and compare helmet- and mouthguard-based sensors that measure the severity and direction of football head impacts. Our goal was to quantify the dynamic response of a mandibular load-sensing headform (MLSH) and to compare its performance and repeatability to an unmodified Hybrid III headform. Linear impactors in two independent laboratories were used to strike each headform at six locations at 5.5 m/s and at two locations at 3.6 and 7.4 m/s. Impact severity was quantified using peak linear acceleration (PLA) and peak angular acceleration (PAA), and direction was quantified using the azimuth and elevation of the PLA. Repeatability was quantified using coefficients of variation (COV) and standard deviations (SD). Across all impacts, PLA was 1.6±1.8 g higher in the MLSH than in the Hybrid III (p=0.002), but there were no differences in PAA (p=0.25), azimuth (p=0.43) and elevation (p=0.11). Both headforms exhibited excellent or acceptable repeatability for PLA (HIII:COV=2.1±0.8%, MLSH:COV=2.0±1.2%, p=0.98), but site-specific repeatability ranging from excellent to poor for PAA (HIII:COV=7.2±4.0%, MLSH:COV=8.3±5.8%, p=0.58). Direction SD were generally <1° and did not vary between headforms. Overall, both headforms are similarly suitable for validating PLA in sensors that measure head impact severity in football players, however their utility for validating sensor PAA values varies with impact location.

Head impact exposure in youth football: elementary school ages 9-12 years and the effect of practice structure

Head impact exposure in youth football has not been well-documented, despite children under the age of 14 accounting for 70% of all football players in the United States. The objective of this study was to quantify the head impact exposure of youth football players, age 9–12, for all practices and games over the course of single season. A total of 50 players (age = 11.0 ± 1.1 years) on three teams were equipped with helmet mounted accelerometer arrays, which monitored each impact players sustained during practices and games. During the season, 11,978 impacts were recorded for this age group. Players averaged 240 ± 147 impacts for the season with linear and rotational 95th percentile magnitudes of 43 ± 7 g and 2034 ± 361 rad/s². Overall, practice and game sessions involved similar impact frequencies and magnitudes. One of the three teams however, had substantially fewer impacts per practice and lower 95th percentile magnitudes in practices due to a concerted effort to limit contact in practices. The same team also participated in fewer practices, further reducing the number of impacts each player experienced in practice. Head impact exposures in games showed no statistical difference. While the acceleration magnitudes among 9–12 year old players tended to be lower than those reported for older players, some recorded high magnitude impacts were similar to those seen at the high school and college level. Head impact exposure in youth football may be appreciably reduced by limiting contact in practices. Further research is required to assess whether such a reduction in head impact exposure will result in a reduction in concussion incidence.

Epidemiology, trends, assessment and management of sport-related concussion in United States high schools

PURPOSE OF REVIEW

Sport-related concussion affects athletes at every level of participation. The short and long-term effects of concussions that occur during childhood and adolescence are not fully understood. The purpose of this review is to describe the current burden of disease, current practice patterns and current recommendations for the assessment and management of sport-related concussions sustained by United States high school athletes.

RECENT FINDINGS

Millions of high school students participate in organized sports in the United States. Current estimates suggest that, across all sports, approximately 2.5 concussions occur for every 10 000 athletic exposures, in which an athletic exposure is defined as one athlete participating in one game or practice. At schools that employ at least one athletic trainer, most high school athletes who sustain sport-related concussions will be cared for by athletic trainers and primary care physicians. Approximately 40% will undergo computerized neurocognitive assessment.

SUMMARY

The number of high school athletes being diagnosed with sport-related concussions is rising. American football has the highest number of concussions in high school with girls' soccer having the second highest total number. Fortunately, coaches are becoming increasingly aware of these injuries and return-to-play guidelines are being implemented.