Sports-Related Concussions in Youth Improving the Science, Changing the Culture (2014) / Chapter Skim
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6 Protection and Prevention Strategies
6 Protection and Prevention Strategies
Pages 239-284
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From page 239... ...
. The chapter then discusses the roles of sports rules, concussion education initiatives, and state concussion legislation in concussion awareness and prevention.
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From page 240... ...
A helmet with increased mass would have reduced linear head acceleration for a given force; however, it may actually increase the rotational acceleration generated from an impact because there would be an increased radius over which the forces are acting. Review of the Biomechanics of Concussion In order to determine if helmet design can indeed be protective against concussion, one must first understand what mechanical events lead to concussions and then determine whether the helmet can mitigate those mechanical forces.
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From page 241... ...
. Impacts to the body, which occur frequently in such contact sports as football and ice hockey, can induce a whiplash-like movement of the head which may be able to generate high enough accelerations to cause injury without subsequent head impact, but the impact velocity to the body must be high.
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. These laboratory animal studies with controlled loading conditions examined the influence of linear or rotational accelerations on brain injury risk independently.
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Injury risk curves describe the probability of injury given a specific mechanical input -- that is, the risk of concussion given a particular rotational acceleration. This relationship is not linear but rather sigmoid (s-shaped)
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Most importantly, all of the existing risk curves are based on data from collegiate or professional football and cannot be directly applied to children and adolescents. Evidence That Helmets Have the Potential to Mitigate Concussion Risk Biomechanical evidence Based on the preceding discussion of the mechanics of concussion, devices that reduce both linear acceleration and rotational acceleration or velocity of the head have the potential to reduce the risk of concussion (Benson et al., 2009, 2013)
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studied different hockey helmet designs through physical testing and a computational model. The helmets demonstrated variability in rotational acceleration which corresponded to variations in brain injury metrics such as maximum principal strain and Von Mises stress.1 Some helmet designs that passed all relevant standards currently based on linear acceleration produced relatively high brain injury metrics (strain)
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concluded that bicycle helmets reduce the risk of head injury (defined as any injury to the brain or skull) by 69 percent, the risk of brain injury by 69 percent, and the risk of more serious brain injury (a score of 3 or more as measured by the Abbreviated Injury Scale score, or AIS)
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found that male nonprofessional rugby players (n=3,207) who self-reported that they always wear headgear during games were less likely to sustain a mild traumatic brain injury (mTBI)
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Many of the standards include a drop test of the helmet with a humanoid headform at specified impact locations and velocities and require that the headform experience linear acceleration below a prescribed threshold known to cause fracture. None of these standards incorporate a measure of rotational acceleration, nor do they include a test protocol that would probe the ability of the helmet to mitigate rotational forces that, as described above, have been shown to cause concussion.
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From page 249... ...
One is the STAR rating system, developed by engineers at Virginia Tech. It is a quantitative metric for rating football helmets that combines concussion injury risk and a theoretical distribution of head impact exposure by impact direction and severity with a helmet's linear acceleration response from NOCSAE-like drop tests at various impact locations and drop heights (Rowson and Duma, 2011)
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In sum, helmet rating systems have the potential to provide useful information to guide consumer decision making. The STAR system is based upon sound principles but is limited by the data available to develop concussion risk curves and thresholds.
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compared to when a mouthguard was not in place. Nonetheless, the authors of this study acknowledged that further well-designed research is needed on the relationship between mouthguards and concussion risk.
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. A multicenter, cluster-randomized trial involving 614 male football players and male and female rugby players at universities in Ontario, Canada, found no significant difference in the number of concussions observed between athletes who wore the WIPPS Brain-Pad mouthguard and athletes in the control group who continued to use their mouthguard of choice.
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. It has been hypothesized that facial protection may also reduce the incidence and severity of head injury in ice hockey by decreasing head acceleration after an impact (Lemair and Pearsall, 2007)
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Until a universally accepted injury risk curve for concussions is established, as well as associated variants with age and perhaps direction, claims of reduced concussion risk with protective devices will not be based on fundamentally sound science. Risk Compensation One unintended consequence of wearing helmets and other protective devices is that the athlete may be emboldened by the increased protection to take additional risks, thus mitigating any benefits of the protective device.
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. In a convenience sample of recreational ice hockey players using facial protection (n=152)
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ASTM standard F1292 provides a "critical height" rating for playground surfaces that approximates the fall height below which a life-threatening head injury would not be expected to occur. The rating assigned to a given surface should be greater than or equal to the fall height of the highest piece of equipment on the playground.
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. In summary, the evidence is inconclusive as to whether concussion risks are higher on synthetic than on natural turf.
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. Body checking is a leading cause of injury in general and of concussion in particular in youth ice hockey (Cusimano et al., 2011; Emery and Meeuwisse, 2006; Emery et al., 2010a; MacPherson et al., 2006; McIntosh and McCrory, 2005)
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Illegal collisions resulted in slightly higher linear and rotational acceleration (23 g; 1530 rad/s2) than did legal collisions (21 g; 1417 rad/s2)
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While the concept of limiting the number of head impacts is fundamentally sound, there is no evidence available at this time to provide a scientific basis for implementing a specific limit on the number of impacts or the magnitude of impacts per week or per season. CONCUSSION EDUCATION Knowledge of concussion signs and symptoms has been found to be deficient in some surveys of youth athletes (Bloodgood et al., 2013; Kaut et al., 2003; Kroshus et al., 2013)
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One study found a significant reduction in body checking–related penalties (which in other studies have been linked to concussion risk) as well as improvements in concussion knowledge in 75 youth ice hockey players ages 11 to 12 who viewed a video on the mechanisms, consequences, and prevention of brain and spinal cord injury versus a group of controls (Cook et al., 2003)
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From page 262... ...
intentions to report sports-related concussions showed that intention to report was associated with perceptions about concussion reporting, perception of important social referents' beliefs about concussion reporting, and perceived control over concussion reporting. Although reporting intention may not always be an indicator of what an individual's actual concussion reporting behaviors will be, these findings suggest that future concussion education initiatives should focus on improving attitudes and beliefs about concussions among athletes, coaches, and parents (Register-Mihalik et al., 2013b)
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Over the past several years, the CDC has developed concussion education materials for a variety of stakeholders. In collaboration with 26 health, sports, and national organizations, the CDC created the "Heads Up: Concussion in Youth Sports" initiative in 2007.
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. "Heads Up: Brain Injury in Your Practice" is a CDC initiative that provides materials on mTBI and concussion for physicians, including a booklet with information on concussion diagnosis and management, a patient assessment tool, a care plan, concussion prevention fact sheets, a palm card for on-field management, and a CD-ROM with downloadable kit materials and other resources (CDC, 2011)
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.9 Although state concussion laws do not focus on the primary prevention of concussion, they do aim to increase awareness about concussion signs, symptoms, and outcomes and to reduce the risk and consequences of multiple concussions (e.g., second impact syndrome) and potentially to promote quicker recovery (Harvey, 2013)
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States also vary on their education and release requirements for parents and youth athletes. Although laws in the majority of states require that parents be provided with concussion education materials, several states do not require parents to read and sign an information sheet describing the nature and risks of concussion as a prerequisite to their children's participation in sports.
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Health departments are generally given supportive responsibility, although in Massachusetts, Missouri, New York, and Pennsylvania, the legislative language gives health departments primary responsibility for the development of concussion training. The only example of an academic entity that has been given the lead responsibility for the development of concussion safety training programs is the Sport-Related Traumatic Brain Injury Research Center at the University of North Carolina at Chapel Hill, which leads a coalition that is developing such programs for the state of North Carolina.
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. This finding suggests that there is a need for broader concussion education so that more providers can deliver these services and FIGURE 6-2 Bar graph showing the types of health care providers permitted to make return-to-play decisions, according to state laws as of December 2012.
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Implementation and Efficacy of State Concussion Laws Of the 47 fully enacted and adopted state laws, 39 of them (83 percent) were passed between 2011 and 2013 and are in the early stages of implementation; many of them have already been or are in the process of being amended and revised.
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Almost all respondents (>90 percent) had good general knowledge about concussions (e.g., knew that a concussion is a type of traumatic brain injury, that concussions may occur without loss of consciousness, and that identifying and treating a first concussion may prevent further injury)
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. The evaluation identified the following factors as important for successful implementation of state concussion laws: • the involvement of a wide range of stakeholders in the imple mentation planning process in order to identify various barriers and facilitators to implementation and to improve outreach and education; • the development of a comprehensive and specific implementation plan early on to support the consistent and complete implementa tion of the law by the various stakeholders; • the consideration of a broad approach to injury prevention, such as combining the return-to-play protocols for concussion with those for other sports-related injuries; • communication with and provision of resources to recreational leagues to whom the state law does not apply by, for example, providing public access to resources developed for entities that are covered under the law; • continuing education for individuals involved in the diagnosis and management of sports-related concussions to ensure that they stay up to date on the latest science; and • consideration of the importance of educating teachers about con cussions and "return to academics" in order to increase their un derstanding of the symptoms and management of concussions.
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From page 272... ...
However, there is evidence that helmets reduce the risk of other injuries, such as skull fractures, and thus the use of properly fitted helmets should be promoted. • There is currently no evidence that mouthguards or facial protec tion, such as face masks worn in ice hockey, reduce concussion risk.
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• While the concept of limiting the number of head impacts is funda mentally sound, implementing a specific threshold for the number of impacts or for the magnitude of impacts per week or per season is without scientific basis based on the evidence available at this time. • While additional research across a variety of sports is needed, some studies involving youth ice hockey and soccer players have shown that the enforcement of rules and fair play policies contributes to reductions in the incidence of sports-related injuries, including concussions.
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2013. Exploration of awareness, knowledge, and perceptions of traumatic brain injury among American youth athletes and their parents.
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2006. Examining concussion rates and return to play in high school football players wearing newer helmet technology: A three-year prospective cohort study.
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2012. Validation of concussion risk curves for collegiate football players derived from HITS data.
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2013. Angular Impact Mitigation system for bicycle helmets to reduce head acceleration and risk of traumatic brain injury.
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2009. Incidence, risk, and protective factors of mild traumatic brain injury in a cohort of Australian nonprofessional male rugby players.
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2005. High rate shear strain of three-dimensional neural cell cultures: A new in vitro traumatic brain injury model.
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1999. A new biome chanical assessment of mild traumatic brain injury: Part 1: Methodology.
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2009. The effects of impact management materials in ice hockey helmets on head injury criteria.
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2009. Customized mandibular orthotics in the prevention of concussion/mild traumatic brain injury in football players: A preliminary study.
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In Proceedings of the 15th Stapp Car Crash Conference. New York: Society of Automotive Engineers.
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2004. A proposed injury threshold for mild traumatic brain injury.
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