6


Protection and Prevention Strategies

This chapter addresses the portion of the committee’s statement of task concerning the effectiveness of protection devices and equipment and sports regulations for the prevention of concussions. The chapter begins with an overview of research on the effectiveness of protective equipment for the prevention and mitigation of sports-related concussions in youth. The committee’s information gathering for this section included the commissioning of a paper that reviews the published literature on the ability of helmets to reduce the risk of sports-related concussions in youth (Duma et al., 2013). The chapter then discusses the roles of sports rules, concussion education initiatives, and state concussion legislation in concussion awareness and prevention. The chapter concludes with the committee’s findings for this portion of its charge.

There is debate around the words “prevention” and “reduction” relative to concussions in youth sports (Duma et al., 2013). All activity involves some risk of injury. Although it may be impossible to prevent all sports-related concussions in youth, measures can be taken to reduce the risk of these injuries. Similarly, in modern medicine, although preventive measures such as screening examinations and prophylactic use of medications will not avert all disease in all individuals, such measures can decrease the risk for disease.

PROTECTIVE EQUIPMENT

Helmets and Other Headgear

Helmets are designed to mitigate the likelihood of head injuries from an impact to the head by dissipating and distributing the energy of impact



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6 Protection and Prevention Strategies This chapter addresses the portion of the committee’s statement of task concerning the effectiveness of protection devices and equipment and sports regulations for the prevention of concussions. The chapter begins with an overview of research on the effectiveness of protective equipment for the prevention and mitigation of sports-related concussions in youth. The com- mittee’s information gathering for this section included the commissioning of a paper that reviews the published literature on the ability of helmets to reduce the risk of sports-related concussions in youth (Duma et al., 2013). The chapter then discusses the roles of sports rules, concussion education initiatives, and state concussion legislation in concussion awareness and prevention. The chapter concludes with the committee’s findings for this portion of its charge. There is debate around the words “prevention” and “reduction” rela- tive to concussions in youth sports (Duma et al., 2013). All activity involves some risk of injury. Although it may be impossible to prevent all sports- related concussions in youth, measures can be taken to reduce the risk of these injuries. Similarly, in modern medicine, although preventive measures such as screening examinations and prophylactic use of medications will not avert all disease in all individuals, such measures can decrease the risk for disease. PROTECTIVE EQUIPMENT Helmets and Other Headgear Helmets are designed to mitigate the likelihood of head injuries from an impact to the head by dissipating and distributing the energy of impact 239

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240 SPORTS-RELATED CONCUSSIONS IN YOUTH and protecting the head from penetration. Early helmets were designed to prevent such injuries as skull fractures as well as moderate to severe brain injuries such as focal contusions and hemorrhages. The typical helmet has a comfort liner, an impact energy attenuating liner, a restraint system, and a shell. Some helmets, such as those used in motor sport, bicycling, and alpine skiing, are designed to attenuate a single impact. Once one of these single-impact helmets has sustained an impact, it must be replaced. Other helmets, such as those used in ice hockey, football, and lacrosse, are de- signed to withstand multiple impacts over a season of games and practices (Hoshizake and Brien, 2004). Part of the difference between single-impact helmets and multiple-impact helmets lies in the materials used. For example, multiple-impact helmets, such as those for hockey and football, use materi- als that do not permanently deform but rather compress and return to their original dimensions. Inner shells can be made of vinyl nitrile or expanded polypropylene, and outer shells use lightweight plastics and composites for durability and protection. Single-impact helmets contain materials that are frangible and deform or fracture permanently upon impact as part of their energy management strategy. Helmet design involves a series of trade-offs between optimal safety and parameters such as the thickness and other characteristics of the attenua- tion material, the size and mass of the helmet, comfort, and acceptability. A primary goal of the attenuation layer is to decrease the peak deceleration and to increase the time duration over which the deceleration occurs; this can be achieved by a thicker or more compliant layer of material which improves the energy management by reducing the peak linear deceleration upon impact. However, better energy management via an increased thick- ness results in a large helmet that may be unacceptable from a style, agility, or visibility standpoint. 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 me- chanical forces. The key biomechanical principles that define the mechanics of concussion were discussed in detail in Chapter 2 and are only briefly re- viewed here. Local brain tissue deformation (i.e., strain) has been shown to cause brain injury as defined by loss of consciousness, white matter injury, hemorrhage, cell death, or some combination of these (Cater et al., 2006; Elkin and Morrison, 2007; LaPlaca et al., 2005; Margulies and Coats,

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PROTECTION AND PREVENTION STRATEGIES 241 2013; Monson et al., 2003; Raghupathi and Margulies, 2002; Raghupathi et al., 2004). If the magnitude or rate of tissue strain is high, local tissue damage occurs. The threshold for the amount of strain required to cause a concussion is unknown, as is whether that threshold varies by age, direc- tion, or individual biological and physiological characteristics. Researchers have developed computational models designed to calculate the distortion of brain tissue that results from global head kinematics such as the accelera- tion or velocity associated with head impacts in sports (e.g., Kleiven, 2007; Post et al., 2011, 2012; Takhounts et al., 2003), but the thresholds used in these studies are not directly applicable to youth concussions as they are often extrapolated from adult human or animal data. Furthermore, the computational models required to make this translation are hampered by a lack of the pediatric-specific brain and skull data needed to ensure that the model adequately mimics a real child. There are several key mechanical factors that influence brain strain that need to be considered when examining the potential concussion-reducing effect of helmets. These include (1) head-impact versus non-head-impact scenarios, (2) rotational versus linear acceleration, and (3) centroidal versus non-centroidal impacts. Because a concussion is a diffuse injury rather than a focal one, the primary difference between an impact directly to the head and an impact to the body that accelerates or decelerates the head is the overall magnitude of the acceleration. Impacts directly to the head raise the risk of focal injuries such as skull fractures and brain contusions, but they have also been shown to result in head accelerations of greater magnitude (Kimpara and Iwamoto, 2012). Work by Ommaya and colleagues in the 1960s and 1970s demonstrated that loading via direct head impact resulted in unconsciousness at lower input severities (Ommaya and Gennarelli, 1974; Ommaya et al., 1971), and studies of diffuse axonal injury, a severe form of diffuse brain injury, have reported that an impact is likely necessary to decelerate the head quickly enough to cause such injury (Yoganandan et al., 2009). 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. A more common concussion-causing scenario occurs when an impact to the body (i.e., person to person) causes the head to hit some other surface (i.e., boards in hockey or the playing surface in football). An impact to the head can result in both linear and rotational accelera- tions. These two types of acceleration can at times be very strongly cor- related (Newman et al., 1999; Pellman et al., 2003; Viano et al., 2012b), but this is often not the case. The centricity of the impact—that is, whether the impact is directed through the center of mass of the head (centroid) or not—is critical to un-

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242 SPORTS-RELATED CONCUSSIONS IN YOUTH derstanding the role of rotational versus linear acceleration in concussion mechanics. Post and colleagues (2011, 2012) conducted an experimental and computational study of centroidal and non-centroidal impacts to a helmeted head. In those impacts directed through the center of mass of the head (centroidal impacts), linear acceleration had a strong correlation with rotational acceleration. For non-centroidal impacts (those not directed through the center of mass) the relationship between linear and rotational acceleration was weak. Furthermore, in those non-centroidal impacts rota- tional acceleration correlated strongly with brain tissue injury metrics such as strain (correlation=0.638) and stress (correlation=0.677), while linear acceleration did not (correlation=–0.238). These findings were replicated in a study of impacts on equestrian helmets (Forero Rueda et al., 2011) and in simulations of National Football League (NFL) concussion cases (Kleiven, 2007). Walsh and colleagues (2011) also reported that linear and rotational acceleration were only moderately correlated especially in non- centroidal impacts. Chapter 2 highlighted several animal studies that examined the inde- pendent role of linear and rotational acceleration in producing concussions. This research suggested that those scenarios in which the head was allowed to rotate resulted in a greater likelihood of concussion and that a pure linear motion of the head was unlikely to produce such injuries (Hardy et al., 2001; King et al., 2003; Ommaya and Gennarelli, 1974; Ommaya et al., 1971). These laboratory animal studies with controlled loading conditions examined the influence of linear or rotational accelerations on brain in- jury risk independently. In sports, however, the vast majority of impacts to the head result in a combination of both linear and rotational motions; it is unlikely to have either purely linear or purely rotational acceleration. Recent head impact data collected in athletes on the playing field using helmet-based sensors, such as the Head Impact Telemetry (HIT) system (see Beckwith et al., 2012; Rowson et al., 2009), initially focused on the ­ role of linear acceleration in concussion risk. From these studies it has been proposed that reducing linear acceleration would lead to reductions in concussion risk (Funk et al., 2012; Rowson and Duma, 2011). How- ever, such conclusions are influenced by important design limitations in how these systems collect and process data. For example, the HIT system does not directly measure rotational acceleration or velocity but rather estimates it from linear acceleration using geometrical assumptions. As a result, the rotational kinematic measures provided by the HIT system have less accuracy than its linear measures do (Allison et al., 2013; Jadischke et al., 2013). In the case of head motions that may have both rotational and linear components, researchers would ideally use independent measures of linear and rotational acceleration (e.g., Camarillo et al., 2013) in order

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PROTECTION AND PREVENTION STRATEGIES 243 to evaluate which of these types of movements are associated with greater concussion risk. When interpreting data on the safety benefits of helmets or other pro- tective devices, it is important to realize that a particular reduction in either linear or rotational acceleration does not necessarily correspond to a similar reduction in concussion risk. 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), often in the form of a Weibull distribution or some other cumulative distribution function (see Figure 6-1). As a result, a 25 percent reduction in acceleration, for example, could actually cor- respond to a very small decrease in the probability of injury if the values of acceleration lie in the early lower left region of the curve. On the other hand, if the 25 percent acceleration reduction is along the steep portion of Mechanical Parameter (i.e., Head Acceleration) FIGURE 6-1 Injury risk curve relating a mechanical parameter such as head accel- eration to the probability of injury. Note that a given reduction in the mechanical parameter does not correspond to an equivalent reduction in injury risk due to the sigmoidal shape of the curve. If the reduction in the mechanical parameter is on the left side of the curve, the corresponding reduction in injury risk is rather small (10 percent to 5 percent in the example above). In contrast, if the reduction in the mechanical parameter is in the steep portion of the curve, the actual injury risk reduction could be rather large (75 percent to 50 percent in the example above).

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244 SPORTS-RELATED CONCUSSIONS IN YOUTH the risk curve, the corresponding reduction in concussion risk may actually be much greater than 25 percent. Other research attempted to quantify the relationship between head kinematics and concussion risk using injury risk curves. The initial attempts proposed quantitative relationships between concussion risk and linear ac- celeration; for example, Pellman and colleagues (2003) used reconstructions of impacts in the NFL, and Rowson and Duma (2011) used collegiate data collected with the HIT system. These efforts focused on linear kinematic measures and thus did not include an evaluation of the influence of rota- tional kinematics on injury risk. Other researchers have developed injury risk curves that incorporate rotational acceleration or velocity; however, ­ these studies are limited by small sample sizes, particularly of the uninjured ­ (Zhang et al., 2004), include estimates of rotational kinematics that have substantial measurement error and incorporate a generic approximation of concussion underreporting (Rowson et al., 2012). More recently, Rowson ­ and Duma (2013) developed a promising concussion risk curve that in- cludes a combination of linear and rotational acceleration; however, this study non-randomly reclassified players who reported no injury to the in- jured group thus biasing the relationship between acceleration and injury outcome in a way that makes interpretation difficult. None of the risk curves in the literature comprehensively account for parameters such as impact direction, previous concussion history, or other biological or physi- ological parameters, all of which likely influence the quantitative relation- ship. 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). Reductions in linear acceleration with particular helmet designs may help mitigate skull fractures and other focal brain injuries and likely contribute to some reduction in concussion risk. However, due to the decoupling of linear and rotational acceleration under certain impact conditions as described above, reductions of linear acceleration alone do not necessarily translate into a reduced concussion risk in most impact conditions. There is some evidence, however, that helmets can indeed reduce rota- tional acceleration. By comparing the impacts of a bare anthropomorphic test device (ATD) head to one fitted with a football helmet, it has been shown that helmets reduce rotational acceleration by approximately 30

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PROTECTION AND PREVENTION STRATEGIES 245 percent (Viano and Halstead, 2012). In a follow-up study, Viano described generic changes in football helmet design that led to decreases in rotational acceleration, suggesting that there are aspects of helmet design that can be modified to reduce the angular motion of the head (Viano et al., 2012b). Post and colleagues (2011) 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) as a result of the angular motion (Post et al., 2011). A similar ef- fect has been observed in speed skating and bicycle helmets (Karton et al., 2012). Rousseau and colleagues (2009) evaluated two different liner materi- als (vinyl nitrile and expanded polypropylene foam) in hockey helmets and found that while the resulting linear accelerations of the head were similar for the two materials, they differed in the rotational accelerations produced. In an effort to reduce rotational energy in helmet impacts, several companies have developed a novel helmet design in which a lubricated flexible membrane is placed either on the outside of the helmet or on the inside between the head and the padding. The fundamental idea underlying this new helmet design is the addition of a low-friction layer between the head and the padding that will reduce the rotational acceleration transmit- ted to the head. Its benefits vary by impact direction. This design concept has been applied, for example, under the MIPS (Multi-directional Impact Protection System) name for equestrian, alpine skiing, snowboarding, and cycling helmets2 and under the Suspend-Tech name by Bauer for hockey helmets. Recently, Hansen and colleagues described the development of such a system in bicycle helmets that was shown to reduce rotational ac- celeration in oblique impacts by 34 percent (Hansen et al., 2013). While this design approach is promising and suggests that the characteristics of a helmet can be manipulated to reduce rotational acceleration, until an ap- propriate injury threshold for concussion can be developed that is age- and direction-specific, it will not be clear what levels of rotational acceleration are acceptable and therefore it will remain impossible to quantify the influ- ence of these design changes on actual concussion risk. In addition to helmets, several other protective devices have emerged that claim to reduce concussion risk. Soccer head gear is a primary example. 1  Maximum principal strain refers to the maximum value of elongation or stretch along one of the principal axes of strain. Von Mises stress refers to an equivalent stress (force/area) and is used to determine if the stress state would result in failure of the material. These two metrics are used separately or together in brain injury mechanics to assess whether a brain will sustain injury under a certain set of loading conditions. 2  See http://mipshelmet.com/find-a-helmet (accessed October 7, 2013).

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246 SPORTS-RELATED CONCUSSIONS IN YOUTH Understanding the role that soccer headgear plays in impacts to the head involves understanding the nature of differences between impacts with hard surfaces, such as other players, goal posts, or the ground, and impacts with the compliant surface of the ball (Niedfeldt, 2011; Spiotta et al., 2012). In an impact between the more compliant ball and a noncompliant head, the ball will deform and absorb the energy of the impact, thus reducing the peak acceleration and increasing the duration of the impact. Headgear has the potential to change the duration of the impact and lower the peak linear acceleration during heading only if it is at least as compliant as the ball and it does not compress fully. Once it compresses fully, it loses its ability to attenuate or reduce the energy transferred to the head. Current headgear compresses fully and rather easily upon impact. The efficacy of soccer headgear in reducing head acceleration has been tested in the laboratory. Withnall and colleagues (2005) conducted volun- teer testing of heading and observed that, because of the amount of ball deformation that occurs during the impact, the linear acceleration of the head did not vary with the use of head gear. When these researchers mim- icked head-to-head contact using two ATD headforms, because the head form is not deformable the headgear provided an overall 33 percent reduc- tion in both linear acceleration and a metric that included both linear and rotational acceleration. Their findings likely apply to impacts with other solid objects as well, such as an opponent’s elbow, the ground, or the goal post. The findings were confirmed by Naunheim and colleagues (2003), who observed no effect of headgear on impacts from heading but noted attenuation of the impact via the headgear in higher-speed impacts with a noncompliant surface. Epidemiologic evidence Epidemiological evidence that helmets mitigate concussion primarily comes from the bicycle helmet literature. In a review of five case-control studies from the literature, Thompson and colleagues (2000) concluded that bicycle helmets reduce the risk of head injury (de- fined 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) (see AAAM, 1998) by 74 percent as compared with control groups consisting of individuals who visited emergency departments after bicycle accidents in which they were not wearing helmets. Furthermore, when they used a con- trol population of all cyclists who crashed, they documented even stronger benefits (85 percent reduction of head injury, 88 percent reduction in brain injury). Although these studies do not specifically separate out concussion injuries, approximately 70 percent of the brain injury subgroup in the study sustained injuries of an AIS 2 level, most of which were likely concussions. The studies they reviewed did not focus exclusively on children, but about

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PROTECTION AND PREVENTION STRATEGIES 247 two-thirds of the population studied were children and adolescents. One of the studies (Thompson et al., 1996) found no effect of age on the effective- ness of the helmet in preventing head injury but suggested that there was a trend that the helmet’s effectiveness in preventing brain injury decreased with increasing age. In the sports environment, by contrast, the epidemiological evidence of helmet effectiveness in preventing concussions is not as strong. Collins and colleagues (2006) demonstrated that newer football helmet technology in high school athletes resulted in a 31 percent decrease in the relative risk of concussion compared to older helmet designs, suggesting that some as- pects of helmet design can help mitigate concussion. However, the absolute decrease in risk in this study was only 2 percent (7.6 percent versus 5.3 percent), suggesting that these findings were not very robust. In equestrian sports, the use of protective riding helmets has been associated with a five- fold reduction in head injury (Havlik, 2010), and similar benefits have been documented in some studies of skiing and snowboarding helmets (Hagel et al., 2005; Mueller et al., 2008; Sulheim et al., 2006); however, these studies have not specifically looked at concussions. The most substantial line of research has been in the evaluation of pro- tective headgear in the sport of rugby, where results have been conflicting. In an early study of 16 “under 15” rugby teams, McIntosh and McCrory­ (2001) found no difference in concussion rates with headgear usage; how- ever, this study suffered from selection bias because the use of headgear was not randomized (McIntosh and McCrory, 2001). Players could chose to wear or not wear headgear, and it is possible that players’ perceived risks influenced their decision. A later study involving male rugby players of ages 12 to 19 corrected this flaw by randomizing participants to stan- dard headgear, modified headgear (made from a thicker and denser foam than standard headgear), or no headgear. There was a nonsignificant trend toward wearers of the modified headgear, who have a lower likelihood of missing a game due to concussion, than toward wearers of the standard headgear; however, the subjects in this study showed poor compliance with the headgear use, and there was limited control for such confounding variables as player position and previous concussion history (McIntosh et al., 2009; Navarro, 2011). Kemp and colleagues (2008) prospectively enrolled a cohort of adult rugby players and documented a 57 percent reduction in concussion risk with the use of headgear. Those researchers used a symptom-based definition of concussion which was broader than the definition used by McIntosh and colleagues (2009). In prospective studies, Hollis and colleagues (2009) 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) over one playing season (incidence rate ratio = 0.57; 95% confidence interval [CI],

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248 SPORTS-RELATED CONCUSSIONS IN YOUTH 0.40-0.82). Conversely, in a cohort study of both adult and adolescent male and female rugby players (n=304), Marshall and colleagues (2005) found that rugby headgear had no protective effect on concussions. In soccer the only formal epidemiological evaluation of headgear in the literature was conducted by Delaney and colleagues (2008), who reported that among Canadian male and female soccer players ages 12 to 17 (n=278) those who did not use headgear were 2.6 times more likely to sustain a con- cussion than those who did. However, there are important methodological limitations to this study that bias its conclusions. The most important of these is the fact that the use of protective headgear was not randomized so that the headgear may have been used by those who felt they were at risk due to their style of play or occurrence of previous concussions. Further- more, the outcomes were all obtained via self-report using unvalidated tools (Delaney et al., 2008; Navarro, 2011). In sum, epidemiological evidence that helmets and other protective devices actually reduce the risk of concussions is lacking. Carefully con- trolled epidemiological studies are needed to further evaluate these devices’ potential for protection. Helmet Standards Organizations such as the National Operating Committee on Standards for Athletic Equipment (NOCSAE) and ASTM International (formerly the American Society for Testing and Materials) have developed helmet stan- dards that specify test protocols and quantitative impact criteria such as the Head Injury Criterion or the Severity Index (see Gadd, 1966; Versace, 1971). These standards are performance standards and do not specify materials or design. They are often sport-specific, and some have differ- ent tolerance thresholds for youth helmets than for adult helmets. Such standards were developed initially to prevent skull fracture, and at their core they remain true to that mission today. 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. There is considerable controversy among experts on the relevance of these test standards for concussion prevention. There are advocates of this testing methodology who claim that reductions in linear acceleration lead to reductions in angular acceleration and therefore holding helmets to a linear acceleration–based standard decreases the risk of concussions (Rowson and

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PROTECTION AND PREVENTION STRATEGIES 249 Duma, 2011). There are others who point out that, as highlighted above, linear and rotational acceleration are not always correlated—particularly in the oblique and non-centroidal impacts that occur often on the playing field—and that any helmet standard or rating system that relies solely on reducing linear acceleration will be limited (Forero Rueda et al., 2011; Halldin et al., 2001; McIntosh et al., 2011). In addition to testing standards for helmets, helmet rating systems have also begun to emerge. One is the STAR rating system, developed by engi- neers 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 loca- tions and drop heights (Rowson and Duma, 2011). The STAR system is theoretically grounded and represents an intrigu- ing approach to how the injury mitigation properties of a helmet could be assessed. However, the rating system contains several assumptions that limit its generalizability. These include (1) estimates of an average number of head impacts per player per season and a distribution of impact direc- tion based on collegiate data; (2) use of a NOCSAE-like drop test which limits the injury risk curve to linear acceleration alone; (3) a concussion risk curve that does not incorporate injury sensitivity to impact direction which has been shown to be an important parameter in head injury thresholds (Gennarelli et al., 1987; Hodgson et al., 1983; Kleiven, 2003; Margulies et al., 1990); and (4) the use of concussion incidence rates derived from college data to weight the injury and non-injury data including a factor of 50 percent applied universally to the data to account for underreporting. Because the assumptions outlined above are based on collegiate data, the STAR rating system as currently defined cannot be directly utilized to rate helmets for pre-college-age youth. In order to extend the rating systems like the STAR system to younger populations, the following pediatric- specific data would need to be collected: (1) the number of head impacts and the distribution of impact location per season, (2) the distribution of impact severity by impact location, and (3) an injury risk curve for concus- sion. These data should be acquired using measurement systems that reli- ably assess impact direction and impact severity and include both linear and rotational motions. It is important that the rating system incorporate the measurement error of these systems perhaps as a confidence range for injury risk. For example, the measurement error associated with the HIT system, which has been used to generate the data for the current STAR system and is being used to collect pediatric-specific data, has recently been reported to be higher than previously published (Allison et al., 2013; Jadischke et al., 2013). Furthermore, it is likely that several of these data sets will need to be created across the pediatric age range—a rating system for high school

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