http://informahealthcare.com/psm ISSN: 0091-3847 (print) Phys Sportsmed, 2015; Early Online: 1–11 DOI: 10.1080/00913847.2015.1039922

CLINICAL FOCUS: RHEUMATOLOGY, PAIN MANAGEMENT AND CONCUSSION GUIDELINES REVIEW

Helmets, head injury and concussion in sport Christopher M. Bonfield, Samuel S. Shin and Adam S. Kanter The Physician and Sportsmedicine Downloaded from informahealthcare.com by Nyu Medical Center on 06/24/15 For personal use only.

Department of Neurological Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA, USA

Abstract

Keywords

Research on the mechanism of concussion in recent years has been focused on the mechanism of injury as well as strategies to minimize or reverse injury. Sports-related head injury research has led to the development of head protective gear that has evolved over the years. Headgears have been designed to protect athletes from skull fractures, subdural hemorrhages and concussions. Over the years, through experience of athletes and continued scientific research, improvements in helmet design have been made. Although these advances have decreased the number of catastrophic injuries throughout sports, the effects on concussions are promising, but largely unproven. In this review, we will discuss development of helmets and studies analyzing their level of protection for both concussion and head injury. This will help us understand what future developments are still needed to minimize the risk of concussion among athletes in various forms of sports.

Concussion, traumatic brain injury, helmet, headgear, protective equipment, sports

Introduction Concussion is one of the most common injuries sustained in collision sports. Over the last decade, there has been increasing attention to sports-related concussions, especially in youth sports due to evidence of potentially dangerous long-lasting effects. As athletes of all ages are becoming bigger, stronger and faster, the risk of concussion also increases. Rule changes have been enforced at all levels of play. Protective gears, including helmets, are also evolving and improving. Helmets have been shown to prevent skull fractures and catastrophic head injuries, however, the ability to prevent concussion is less clear. This review investigates a wide range of sports that utilize protective helmets and headgears and reports studies focused on prevention of concussion.

Materials and methods PubMed search engine was used to find 82 articles that were used in this review. Specifically, the following terms were used in the query: “helmet”, “concussion”, “headgear”. Additional articles were found from references made in the initial set of articles. Thorough analysis of the contents of these articles and categorization by each sport category was made. Table 1 was formulated from this information. Figures were made from reorganization and modifying various pictures of helmets found from online search engine. Baseball and cricket Both baseball and cricket are sports played with a hard ball thrown at high speeds. In the USA alone, 9 million youths

History Received 4 December 2014 Accepted 8 April 2015 Published online 27 April 2015

participate in organized baseball every year [1] with many more in the world including adults. Although not considered a contact sport, baseball causes more injuries requiring emergency room visits than any other sport in the USA. Catastrophic injuries are rarely seen, but typically involve direct ball impact to a player’s head or chest. Batters at all levels are required to wear protective helmets. These helmets, constructed with a very thick, soft inner liner surrounded by a flexible shell, are designed to withstand direct impacts from a fast moving ball. Despite this, there are over 170,000 head injuries in baseball in the USA each year [2], constituting 86% of all injuries in Little League [3]. Like many reports on head injuries in sports, these are not further classified based on severity or mechanism, but instead are simply grouped into body area. Over 80% of head and face injuries occur in in-fielders, who wear no protective gear on the head or face. Also, batting helmets at all levels are mostly open-faced, allowing the ball to make direct contact with the player. Because of these findings, recommendations and research involving the improvement of baseball helmets is ongoing [4]. Specifically, the effect of helmets with facemasks, softer baseballs, reduction of metal bats linear velocity (swing speed) and the different helmet construction material is being evaluated with regard to head impacts. Similarly, catchers and umpires are at risk for concussion from foul balls even with modern helmet and mask technology. Catcher masks have been demonstrated to decrease head acceleration metrics by over 85%, yet concussions still occur [5]. Therefore, more detailed impact models are used to evaluate

Correspondence: Samuel S. Shin, MD PhD, Department of Neurological Surgery, University of Pittsburgh Medical Center, UPMC Presbyterian, Suite B-400, 200 Lothrop Street, Pittsburgh, PA 15213, USA. Tel: +1 412 427 9944. Fax: +1 412 647 0989. E-mail: [email protected]  2015 Informa UK Ltd.

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Table 1. Summary of outcomes from various protective headgear studies.

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Article

Sport

Protective Gear

Outcomes

Dorsch (1987) [66]

Bicycling

Helmet

Thompson (1989) [64]

Bicycling

Helmet

Wasserman (1990) [67] Bicycling

Helmet

Head injury, Mortality Head injury, brain injury Concussion

McDermott (1993) [59] Bicycling

Helmet

Head injury

Mock (1995) [57]

Bicycling

Helmet

Severe head injury

Finvers (1996) [69]

Bicycling

Helmet

Severe head injury

Linn (1998) [61]

Bicycling

Helmet

Concussions

Shafi (1998) [71]

Bicycling

Helmet

Head injury

Cook and Sheikh (2000) [58] Heng (2006) [62]

Bicycling

Helmet

Head injury

Bicycling

Helmet

Head injury

Berg and Westerling (2007) [70] Alles (1979) [89] Zemper (1994) [90]

Bicycling

Helmet

Head injury

Football Football

Helmet (13 designs) Helmet (10 designs)

Concussion Concussion

Torg (1999) [91] Collins (2006) [92]

Football Football

Concussion Concussion

Rowson (2014) [93]

Football

ProCap helmet cover Helmet (Riddell Revolution vs old) Helmet (Riddell VSR4 vs Riddell Revolution) Headgear

McIntosh and McCrory Rugby (2001) [107] Kahanov (2005) [104] Rugby

Headgear

Marshall (2005) [108]

Rugby

Headgear

Kemp (2008) [106]

Rugby

Headgear

McIntosh (2009) [109]

Rugby

Hollis (2009) [105]

Rugby

Standard headgear, modified headgear Headgear

Macnab (2002) [40]

Ski and Snowboard Helmet

Hagel (2005) [41]

Ski and Snowboard Helmet

Sulheim (2006) [42]

Ski and Snowboard Helmet

Fukuda (2007) [43]

Snowboard

Mueller (2008) [35]

Ski and Snowboard Helmet

Greve (2009) [44]

Ski and Snowboard Helmet

Rughani (2011) [45]

Ski and Snowboard Helmet

Delaney (2008) [84]

Soccer

Headgear

Kraus (1970) [24]

Hockey

Helmet

Bond (1995) [55]

Horseback riding

Helmet

Brandenburg and Archer (2002) [54]

Rodeo

Helmet

Helmet, knit cap

Concussion Concussion

Summary Helmet use significantly reduced risk of brain injury (p = 0.025) and mortality (10 times less) Helmet use significantly reduced risk of head injury (OR 0.15, 0.07–0.29) and brain injury (OR 0.12, 0.04–0.40) No significant reduction of concussion risk with helmet use (0.56, 0.29–1.07) Decrease in head injury by 45% in children wearing helmet (p = 0.001) Decrease in severe head injury rates over years of increasing helmet use Significantly increased risk of severe head injury without helmet (OR 3.12, 1.13–8.75) Of the 62 concussions, 57 occurred to non-helmet users (OR 4.04, 1.55–11.47) No difference in concussion rate with helmets, but less skull fractures (p < 0.02) and intracranial hemorrhages Decrease in head injury rates over years of increasing helmet use Helmet use significantly reduced risk of head injury (OR 0.09, 0.002–0.65) Decrease in head injury rates over years of increasing helmet use No difference in concussion rate among helmet designs Significantly lower concussion rate with Riddell M155 and a significantly higher rate with the Bike Air Power No change in repeat concussion rate with ProCap use Decreased risk of concussion with Riddell Revolution (OR 0.69, 0.50–0.96) Decreased risk of concussion with Riddell Revolution compared with Riddell VSR4 (RR 46.1, 28.1 and 75.8%)

No significant reduction of risk between wearing headgear and not wearing headgear (IRR 1.06, 0.22–5.10) Concussion Reduction in concussion rate with headgear use (32 vs 104) Concussion No significant difference in concussion rates with headgear use (RR 1.13, 0.40–3.16) Concussion Reduction in incidence of concussion with headgear use (IRR 0.43, 0.21–0.92) Concussion No significant difference in concussion rates with headgear use (p > 0.05) Mild TBI Headgear use significantly reduced risk of mild TBI (IRR 0.57, 0.40–0.82) Head injury Increased incidence of head injury without helmet use (RR 2.24, 1.23–4.12). No difference in cervical spine injury Head injury Helmet use significantly reduced risk of mild head injury by 29% (OR 0.71, 0.55–0.92) and severe head injury by 56% (0.44, 0.24–0.81) Head injury Helmet use significantly reduced risk of mild head injury by 60% (OR 0.40, 0.30–0.55) and severe head injury by 57% (0.43, 0.25–0.77) Serious head injury No significant association between helmet or knit cap wearing and incidence of serious head injury (p = 0.056) Head injury Helmet use significantly reduced risk of head injury (OR 0.85, 0.76–0.93) Head injury Helmet use significantly reduced risk of head injury (p < 0.05) Skull fractures Helmet use associated with lower incidence of skull (p = 0.009) and craniofacial (p = 0.03) fractures Concussion Increased concussion rate with not wearing headgear (RR 2.65, p = 0.001) Head injury Helmet use significantly reduced risk of head injury (p = 0.03) Head injury Significantly more severe head injuries without helmet use and higher rate of hospitalization Head injury Helmet use significantly reduced risk of head injury (IRR 0.43, 0.26–1.02)

Abbreviations: IRR = Incidence rate ratio; RR = Rate ratio; TBI = Traumatic brain injury.

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DOI: 10.1080/00913847.2015.1039922

current masks. For example, laboratory investigations have demonstrated that impacts to the eyebrow and chin areas appear to cause the most severe forces to a catcher mask [6]. More information regarding the exact mechanisms of impact and injury can be used to create masks that have improved coverage in these areas. Similarly, cricket players are at risk for head injuries from ball impact. Like baseball, most of the literature groups all types of head injury together. Stretch et al. reported that 9– 25% of injuries to batsmen occurred in the head and face area [7]. Another large study showed that 44.4% of all cricket-related presentations to the emergency room in children and 16.6% in adults were due to head injury [8]. Furthermore, a New Zealand study reported the most common injury in children less than 10 years was to the head. Overall, head injuries accounted for approximately one-quarter of all injuries, with 10% reported as concussions, and over 30% as fractures [9]. Helmet and facemasks use is mandatory for professional and elite level clubs. However, there are not universal standards for the remainder of players, although most in developed countries wear them when batting. Due to financial reasons, in some developing countries, helmets are only used sparingly [10]. Due to the presence of head injuries despite wearing helmets, groups have evaluated to try to identify where failures occur. One study illustrated that although cricket helmet performance is satisfactory for low speed impacts, it is not for higher, more realistic, game speeds [11]. This was thought to be due to the very thin liners inside the helmet, which does not offer much force absorption. Ranson et al. also determined that some helmets do not adequately protect batters from injury [12]. Balls can penetrate the gap between the helmet and the faceguard and directly contact the player. In some cases, the faceguard was voluntarily lowered to improve vision, while in others, the helmet was simply too flimsy to block the ball. The authors recommended methods should be devised to include projectile tests to the faceguard and helmet, and more attention to the lower rear of the helmet shell. They also concluded that cricket helmet design and associated National and International Safety Standards should be improved to provide increased protection against head injury related to ball impact to the faceguard and shell of the helmet. The British Standard Specification for head protectors for cricketers has agreed to update their rules and specifications for cricket helmets. As some countries still do not have helmet safety standards at all, it is envisioned that the productions of an international cricket standard will be sought and instituted [13]. Hockey Ice hockey is an aggressive sport which results in high risk of injury, particularly concussion. It is played at a fast pace and players come in contact with hard surfaces including boards, glass, ice, goal posts, sticks, pucks and each other. To reduce risk of injury, numerous changes have been made to the game over the last century. Protective equipment, including helmets and faceguards, has been improved. Recently, rule changes resulting in fines and suspension for hits to the head have been enacted. The National Hockey League (NHL)

Helmets and concussion

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and other professional leagues around the world have initiated concussion protocols in order to better prevent, recognize and treat concussions. With over 1,000,000 youth hockey participants in Canada and the USA combined, concussion is an issue that reaches beyond the professional level. Concussion rates are variable depending on level of play, players’ age and reporting methodology. In 2011–2012, the NHL reported approximately 90 players missed games due to concussion [14]. This is consistent with a mean of 80 concussions per year, 1.8 per 1000 player game-hours and 5.8% of players diagnosed from 1997 to 2004 [15]. Another report illustrates a slight decline in concussions from 1997 to 2008 with the most recent incidence of 1.26 concussions per 1000 athlete exposures (AE) [16]. Incidence in the Swedish Elite League is similar with 5% of players per year with a concussion [17]. In the USA National Collegiate Athletic Association (NCAA) programs, hockey has higher rates of concussion compared with other sports (0.41 per 1000 AE for men and 0.91 per 1000 AE for women) [18]. Another report lists the male concussion rate as 0.72 per 1000 AE for men and 0.82 per 1000 AE for women [19]. However, other published studies show a higher incidence in the same population at 3.1 per 1000 AE, with concussion being the most common injury (18.6%) [20]. University hockey in New Zealand has been reported to have an incidence of 1.7 per 1000 AE [21]. Echlin et al. found a much larger incidence in Canada varsity hockey at 7.5 per 1000 AE in men and 14.93 per 1000 AE in women [22]. In the USA, high school male hockey has been reported to have a much lower incidence at 0.54 per 1000 per AE [23]. Data related to the incidence of concussion in younger age groups are sparse. Helmet use in the NHL was instituted in 1979, more than 50 years after head protection was first introduced by a goaltender. Elsewhere, helmet use in Sweden began in the 1950s, and became mandatory in 1963. In Canada, helmet use was mandated for youth hockey in 1965, a requirement that began shortly thereafter in the USA. Around this time, Kraus et al. reported the first data in support of helmets decreasing head injury in ice hockey [24]. A significant decrease in head injuries was seen in college intramural hockey players who wore helmets compared with those who did not [24]. After the death of two amateur hockey players in Canada in the late 1960s, a call for new helmet technology led to the development of the Canadian Standards Association (CSA). The International Organization of Standardization (ISO) developed its first draft standards for helmets in 1987. Currently four official standards, including the Committee European Normalisation (CEN), ISO, CSA and the American Society for Testing and Materials (ATSM), regulate helmet design and construction [25]. New technologies are currently being evaluated in order to make better, more protective helmets. Hockey helmet development over the years are shown in Figure 1. The standards that manage the protective helmets use peak linear acceleration (g) as their pass/fail criteria. Historically, this level is between 250 and 275 g, which is based on traumatic brain injuries (TBIs) and skull fractures [26]. Therefore, devastating injuries have largely disappeared from the sport. However, rotational acceleration has been linked with

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1963

2010s

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Figure 1. Hockey helmet development over the years. Lightweight, adjustable helmet with an option for attachment of visor developed over the years. Adapted with permission from BMJ Publishing Group Ltd. [25].

concussion and may not be measured fully in helmet evaluations [27]. Therefore, new laboratory techniques, involving measuring brain deformation responses, are being utilized in evaluating the performance of helmets [28]. Similarly, Allison et al. have begun testing The Head Impact Telemetry system (Simbex LLC; Lebanon, NH) measures along with anthropometric test device (ATD) modeling, to get a more accurate measurement of the impact to the head (not just the helmet). They show that errors in peak acceleration between the system and ATD varied between 18 and 31% for linear and 35 and 65% for rotational acceleration and could only be reduced slightly by calibration factors [29]. Because of these findings, new helmet-based instrumentation systems, such as the gForce Tracker (Markham, ON), have been developed that use gyroscopes in combination with accelerometers to more accurately measure rotational kinematics. Preliminary studies show decreased errors when measured with ATD modeling [30]. In all levels of youth hockey and many senior levels, full faceshields are worn with the helmet. Much research regarding face protection is focused on the prevention of ocular, face and dental injury. However, some studies did evaluate the effect of faceshields on concussions as well. These studies indicate that full-face protection does not lessen the incidence of concussion compared with partial face protection or no face protection [31,32]. However, Benson et al. reported that face protection could reduce concussion severity and result in an earlier return to play [32]. A systematic review on faceshields and concussion suggests that the use of facial protection in ice hockey does not lead to an increased or decreased risk of concussion, and that the use of a FFS may actually decrease the severity of concussion and allow for fewer missed practices and games with a faster return to play [33]. Skiing and snowboarding Skiing and snowboarding are extremely popular sports across the world. It is estimated that over 200 million people participate in skiing alone, and there are over 10 million skiers and snowboarders in the USA [34]. Over 600,000 injuries are reported in the USA each year, with head injuries accounting for 20% of them [35]. Snowboarders have a 50% higher rate of head and neck injuries compared with skiers [36]. Overall,

TBI is the leading cause of death among those who ski and snowboard [37]. Most of the published literature does not delineate the types of head injury, however, and estimates of concussion greatly vary from 20 to 80% of all head injuries [38]. A surveillance study from 1996 to 2010 in the USA estimated that 77.2% of head injuries were TBI (intracranial injury, concussion or fracture). In that report, the annual average incidence rate of TBI was 2.24 per 10,000 resort visits for children compared with 3.13 per 10,000 visits for adolescents. The incidence of TBI increased from 1996 to 2010 among adolescents (p < 0.003) [39]. Numerous studies have investigated the use of helmets in relation to head injuries due to skiing and snowboarding, the first of which was published in 2002 [40]. In this study of children less than 13 years of age, an increased incidence of head injury was seen without helmet use (rate ratio [RR] 2.24, 1.23–4.12) with no difference in the rate of cervical spine injury. Two subsequent studies supported these findings in skiers and snowboarders of all ages. Hagel et al. showed that helmet use significantly reduced risk of mild head injury by 29% (odds ratio [OR] 0.71, 0.55–0.92) and severe head injury by 56% (OR 0.44, 0.24–0.81) in Canada [41]. Similarly, the risk of mild head injury (60% reduction, OR 0.40, 0.30–0.55) and severe head injury (57% reduction, OR 0.43, 0.25–0.77) was reduced by helmet use in a 2007 study from Norway [42]. A Japanese study was unable to show a significant association between helmet and knit cap wearing and serious head injury overall, but head protection did decrease serious head injury due to jumping [43]. Other studies support the protective properties of helmet utilization, revealing significantly reduced risk of head injury [35,44], as well as skull and craniofacial fracture [45]. A meta-analysis by Russell et al. concludes that helmets decrease the overall head injury risk by 35% (OR 0.65, 0.55–0.79) and that helmet use should be encouraged [46]. However, other studies dispute the claim of decreased concussions and head injury with helmet use [47]. Shealy et al. reported that although helmet use has increased, the mortality rate (0.75 deaths per 1,000,000 visits) in winter snow sports has remained unchanged. Furthermore, among the fatally injured skiers, helmet utilization is equal or greater than the general population [48]. They challenge that at speeds typically seen on the mountain, helmets are unable to protect the

Helmets and concussion

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skier from a serious head injury. Helmets may guard against minor head injury like head lacerations, mild concussions and skull fractures, but there is no effect on more severe injuries. Despite the lack of conclusive evidence of the utility of helmets, use continues to increase. The high profile deaths of Michael Kennedy, Sonny Bono and Natasha Richardson brought the issue of helmet use in snow sports to media forefront. Although there is no law in the USA requiring helmet use, the US Consumer Product Safety Commission projected that 44% of head injuries could be prevented by the use of helmets in skiing and snowboarding, and that the use of helmets for children aged 15 and under could reduce head injuries in this group by 53% [49]. European countries such as Italy, Croatia and Austria have mandated helmets for children aged 15 years and younger. In 1998, a social-marketing campaign and helmet loaner program to increase helmet use among skiers and snowboarders was enacted. For the 1998–1999 season, 13.8% of renters in participating stores accepted a helmet compared with 1.38% in the nonparticipating stores (p < 0.01); for 2000–2001, 33.5–3.93% (p < 0.01); and for 2001–2002, the numbers rose to 30.3–4.48%, respectively (p < 0.01) [21]. In Colorado resorts in 2002, while 2–38% of skiers and snowboarders rented equipment, less than 1–8.6% of renters rented helmets. Helmet rental was encouraged mostly for children [50]. Recent data from the US have shown that helmet use has increased drastically from 25% in skiers and snowboarders in 2003 to 57% in 2010 [34]. Policies and interventions to increase helmet use continue to be promoted to reduce mortality and head injury among skiers and snowboarders [34,51]. Overall, the helmet should be used as a part of a complete safety program on the slope. Skiers should perform responsibly, ski in control and utilize the same precautions they would if not wearing a helmet. Rodeo and equestrian Rodeo competitions are frequently held throughout North America. It is a sport with a high potential for injury, especially bull riding, which involves a large, aggressive animal with tremendous power and the natural instinct to attack its rider [52]. In bull riding alone, a 5-year analysis in Canadian rodeo showed an incidence of 32.2 injuries per 1000 competitor exposures with concussions accounting for approximately 9% of injuries [53]. However, there are few studies that investigate the use of head protection in these competitions. An Oklahoma survey analysis of mainly amateur bull riders reported the decreased incidence of head injuries from 1.54% per ride to 0.80% per ride when wearing a protective helmet [54]. Similarly, a study of pediatric equestrian injuries also showed significantly more severe head injuries without helmet use and a higher rate of hospitalization [55]. As a result, in 2004, the First International Rodeo Research and Clinical Care Conference issued a statement regarding concussions in the sport [56]. The conference recommended a physician should be present at all bull riding and rodeo events to assess and manage concussions. Furthermore, any rider sustaining a concussion must be restricted from riding for a minimum of 1 week and produce a letter of

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medical release prior to returning to competition. In regards to helmet use, the conference acknowledged the lack of published studies and data. However, the authors agreed that risk of riding without helmets far outweigh the risk with head protection. Therefore, they concluded that all riders 18 years and older are encouraged to wear head and facial protection, while those less than 18 years old are required to wear helmets. Despite this, helmet wearing remains universally underutilized and not required by all rodeo organizations. Further studies are still needed to produce evidence that will support and make helmet use more commonplace in rodeo and equestrian sport. Bicycling The cycling population represents a wide variety of participants. Bicyclists include people of various ages involved in recreation, transportation and athletic competition. There have been numerous studies from large databases of populations analyzing the incidence of head injury and helmet use with bicycling over the years [57-61]. Several studies have specifically reported that facial injuries are reduced with helmet use in addition to head injuries [62,63]. An early case–control study in the 1980s showed that cyclists with helmets have an 85% reduction in risk of brain injury following a bicycling accident [64]. A larger follow-up study, comparing the effectiveness of helmet in each age group illustrated that helmet prevents head injury across all ages [64]. In addition, prospectively collected data on over a thousand patients with bicycling accidents reported that helmets reduce the risk of head injury by a factor of three [65]. Support for helmet use has also been made from questionnaire-based studies; although limited by possible recall bias, bicyclists have reported significantly reduced head injury among helmet users over nonusers [66-68]. Based upon these retrospectively analyzed reports, societal support for helmets and the popularity of its use has increased over the years, with decreased rates of head injury reported in several large epidemiological analyses [57-59]. Concordantly, a case–control study showed a significantly greater risk of head injury when helmets are not used [69]. Given that specifically children under 15 years of age had the highest incidence rates of a bicycling injury, mandatory use of helmets is an important prevention strategy in the pediatric population [70]. In support of this, studies on pediatric cyclists show the effectiveness of helmet use in preventing face injury, concussion [61] and skull fracture [71]. These observational studies were further supported by laboratory experiments that simulated bicycling injuries. In a simulated cycling injury model using a weight drop impact when comparing the helmeted and unhelmeted headforms, the risk of head injury is reduced from 99.9 to 9.3% [72]. Whereas unhelmeted impact resulted in a sharp increase in acceleration followed by a sharp decrease, helmeted impact resulted in reduced peak acceleration by a factor of 4.2. In general, helmeted impact had reduction in three tested parameters: head injury criterion (HIC), injury probability and peak acceleration. Thus, modern bicycle helmets were effective in reducing injury at realistic impact speeds. However, helmets

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may not be protective at higher velocities such as one which would involve collision with motor vehicles. Involvement of motor vehicles in bicycling accidents had a significantly higher association with head injury [65], indirectly showing that the protectiveness of helmets at larger energy collision is likely limited. Earlier experimental studies comparing the damage observed on a helmet after an accident with a simulated damage in a sample helmet identified several areas of improvement for helmet design [73]. Several important differences were identified by analysis of the helmets from accidental impacts compared with simulated impacts: helmets damaged in an accident often were found with environmental degradation, subjected to multiple impacts, and had impact on areas not evaluated during certification tests. As such, some studies have claimed the need for helmet design that protects lower parts of the head such as the temporal and zygomatic arch area [74]. Specific helmet designs that are more protective than others have also have been identified over the years, and the development of bicycling helmets are displayed in Figure 2. A comparison of differing types of bicycle helmets showed that hard shell helmets compared with foam helmets reduced the risk of head injury [75]. Thus, future improvements in helmet design would require specific consideration of the outer shell design, the ability to protect from head injury at high and low impact as well as more extensive coverage from impact at wider areas of contact. Although numerous studies have supported the use of helmets in order to reduce the risk of head injury, many of the studies on the effectiveness of bicycle helmets have been criticized for publication bias [76]. As explained by Elvik, large increases in helmet usage may not necessarily reduce the incidence of head injury among cyclists since the prior studies may have been biased by selective recruitment [77]. For example, subjects who were wearing helmets in the retrospective database would be more cautious riders than those who were not wearing helmets. Thus, a less risky style of riding may be the major reason for lower incidence of head injury among helmet wearers. Another major concern is the increased risk of injury to the head with improper helmet usage, and injury to the neck under specific impact conditions. Improper use of helmets with poor fit may lead to worse outcomes in impact. Individuals with poor fitting helmets have 1.96-fold increased risk of injury compared with individuals with well-fitting helmets [78]. In addition, helmets may actually increase risk of neck injury [77,79]. In a study using a cadaver model of head impact, padded surface increased the risk of cervical spine injury such as cervical fracture and ligamentous avulsion [80]. This injury was hypothesized due to the padded surface increasing the load on the neck by directing the momentum of the torso to the neck. In summary, there is a large body of epidemiological evidence that support the use of helmets in protection from head injury during cycling. However, there remains significant room for optimization of helmet design as identified by laboratory and retrospective clinical studies. Barriers against further popularization remain present, as a significant proportion

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Pre 1970

1990

1980

2000

Figure 2. Development of bicycling helmet. In earlier part of twentieth century, bicyclists used leather covered padding. Helmets in the 1980s utilized expanded polystyrene, and variations in helmet designs continued with more vents and polyethylene terephthalate covers in the 1990s. Although elongated helmets have been the fashion trend in the 1990s, more recent helmets have become rounder to offer protection from crash at any point on the helmet.

of cyclists do not wear helmets and consider helmet use to not protect against head injury even in modern times [62]. Soccer Soccer is the most popular worldwide sport, with over 265 million players, and 2.5 million in the USA alone [81]. Voluntary heading of the ball is frequent, but concussions mainly result from head to head, head to elbow or involuntary ball to head contact. Protective headgear has been developed to decrease the forces associated with heading, and thus the risk of concussion, yet it is not routinely worn during play. Various studies have investigated the potential protective effect of these protective headgears in soccer. Two laboratory studies concluded that headgear was not effective at reducing impact of the soccer ball when heading [82,83], however, it may be helpful in decreasing the impact of more forceful collisions, or other non-ball-related impacts to the head. Delaney et al. reported on a survey of youth soccer players relating to concussion and the use of headgear and found an increased concussion rate in females and those not wearing headgear [84]. Of note, the use of headgear was self-selected by the players, and the survey relied on retrospective information collected at the end of the season. Furthermore, some reports postulate that players wearing headgear may engage in more aggressive behavior on the field, thus increasing the risk of injury and concussion [85]. More studies are necessary in order to validate or refute these claims. Football In the USA, there are approximately two million professional or amateur American football players [86]. Due to this large number, football accounts for the greatest number of

Helmets and concussion

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Figure 3. Evolution of the football helmet. Initial helmets were simple designs of leather covering. Next generations utilized hard shell design, with further developments of face shield and multiple layer designs.

concussion injuries in the USA. Given the collision and vigorous tackling nature of the sport, helmets have been utilized in football for many decades. Helmet use was first documented during an Army-Navy game in 1893 [87], subsequently becoming mandatory for the NCAA in 1939, and the National Football League in 1940. In 1969, the National Operating Committee on Standards for Athletic Equipment (NOCSAE) began initial research efforts into helmets, leading to the establishment of safety standards for football helmets in 1973 [88]. Large-scale studies on helmet design and incidence of concussion have been reported. In early studies from 1979, more than 16,000 athletes in college football showed 905 concussions over 3 years [89]. In this study, no specific helmet type or brand was associated with significantly greater risk. A subsequent study in the 1990s showed significant differences in injury protection among helmet types [90]. Among the 10 football helmets models, 245 total concussions were reported, with a significantly lower rate of concussion with the use of Riddell M155, and a higher rate with Bike Air Power. This indicated that helmet design among different manufacturers may have varying degree of protection from concussion, although the mechanical aspect of this difference was not explored. An array of research has been performed in helmet design, including adding a superficial layer of cover to the helmet with the intention of reducing impact energy. Evolution of football helmet is depicted in Figure 3. Polyurethane covers placed over the exterior shell of a helmet were used in the 1990s, but there was no significant reduction in concussion rates observed [91]. Other studies have directly compared concussion rates among helmets with varying designs [92,93]. A prospective cohort study detailing the rates of concussion among high school football players grouped into those using Revolution helmet by Riddell compared with those using a traditional helmet revealed concussion rates significantly lower in the Revolution helmet group, with a 31% decreased relative risk and 2.3 absolute risk reduction [92]. Another retrospective analysis of head impact data from football players using helmet equipped with accelerometers showed the Riddell Revolution helmet to reduce concussion rates when compared with VSR4 helmets [93]. Concussion risk reduction was proposed due to the differences in helmet design: Revolution helmet has an exterior shell protruding more anteriorly with respect to the mandible compared with

traditional helmets. In addition, it has a 40% thicker foam and greater distance between the shell surface and the head. This design was made for the purpose of absorbing impact at the lateral parts of the head and face. Focused studies comparing multiple helmets from the 1990s to 2010 (including Revolution) using measurements of rotational acceleration, translational acceleration and HIC showed significant improvements in impact performance in more modern helmet designs [94]. An initial comparison of leather helmets to varsity helmets, evaluating several parameters including angular acceleration, linear acceleration, neck force and neck moment, showed that the risk of head injury may be comparable even with the use of leather helmets [95]. A more thorough study comparing varsity helmets with leather helmets showed consistent superiority of varsity helmets in head protection [96] and prior finding by Bartsch et al. was attributed to lower impact energy (impact velocity of 5.0 m/s) and impactor set up that added compliance to the system and masking their differences. Importantly, varsity helmets are optimized to reduce the impact of high magnitude linear acceleration. The upper limit of impact velocity for modern helmets has been further investigated. A systematic laboratory testing of impact velocity at three different settings 7.2, 9.3 and 11.7 m/s at multiple angles showed that at highest velocity, even modern helmets are not sufficiently protective [97]. Given that this velocity is within range of the severity of impact experienced in professional football, newer helmets that can protect athletes from this level of impact will be helpful. However, majority of football players do not reach this impact velocity and are within the range of protection offered by current helmet design. As further developments in helmet design are made, future studies are needed for testing protection from both high and low severity impact. The differences in energy absorbing characteristics among various materials have been previously reviewed [98]. Vinyl nitrile and expanded polypropylene perform well in absorbing low energy multiple impacts but materials such as expanded polystyrene (EPS) can absorb high energy impacts at high capacity. However, EPS can deform after the impact and may not be effective in reducing low-level accelerations. Utilizing these material properties, there is ongoing research in development of modern helmets to reduce the energy of impact in various types of collisions. To optimize the evaluation system for helmets, the Summation of Tests for the Analysis of Risk (STAR) equation has

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been developed which assesses data from 24 drop tests at four impact points and six energy levels combined into one number [99]. The data from all the drop tests were combined into a single number that predicts the injury risk for a football player during one season from 1000 exposures. For example, a STAR value of 1.501 represent 1.5 concussions if a player wore a specific helmet for one season of 1000 head impacts. Such system would be able to help helmet users evaluate the level of protection from each helmet by simplifying the assessment of helmet performance into a single metric. In addition to optimization of helmets, neurocognitive testing is needed at both short and long term detailing the injury of the athlete in order to fully understand the level of protection. Unfortunately, these studies are limited by underreporting of concussion which is common in the culture of sports, with studies proposing the true incidence at 2–10 times greater than that reported [100]. Rugby Rugby is a high contact international sport popular in many nations such as Australia, Great Britain, New Zealand and South Africa. Unlike American football, protective headgear is not required and players have shown poor compliance [101]. The higher incidence of head injury in rugby compared with football has been attributed to this difference [102]. The only protective headgear in rugby consists of soft polyethylene foam with no hard shell. Rugby players generally believe that headgear protects them against concussion [103], and players using headgear have reported lower incidence and severity of concussions compared with those not wearing headgear [104]. Large-scale data also support the use of headgear in protection from concussion. A large cohort of 3207 rugby players observed over one or more playing seasons found 9.8% of players experienced one or more concussions. Among the players who always wore protective headgear, there was a significantly reduced risk of concussion at an incident RR of 0.57 [105]. Another large cohort study with 757 rugby players showed that concussion injuries were significantly higher in players when not using headgear compared with players using headgear [106]. The effectiveness of headgear usage in rugby has been challenged. A prospective study of 294 junior rugby players compared a group of headgear users with a control group and showed no significant difference in concussion rates between them [107]. Headgear did reduce damage to the scalp and ears in a similar report, but no reduction of concussion was reported [108]. In a randomized controlled trial comparing teams assigned to one of the three groups: standard headgear, modified headgear and no headgear, rates of injury were compared [109]. The modified headgear group used a thicker polyethylene foam (16 mm thickness, 60 kg/m3 compared with the standard: 10 mm thickness, 45 kg/m3) that was shown to have superior attenuation of impact energy [110]. No significant differences were found in concussion rates, and the authors attributed this lack of difference due to the low compliance of headgear use in the groups. Also, in a laboratory test using a

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weight drop impact, currently commercially available headgear was not able to attenuate impact energy at higher levels of impact [111]. These studies demonstrate that currently used standard rugby headgear provides limited protection from concussion and may benefit from further development and optimization of design. Moreover, the use of headgear in rugby is relatively uncommon (27%), and support for its use is limited among rugby coaches due to its cost and discomfort during usage [103]. Unlike helmet/headgear use in other sports, its use in rugby has much room for development and popularization, which will assuredly lead to reduction in head injury as shown in numerous other contact sports.

Summary As seen in several football helmet studies, the level of protection from head injury depends on the several parameters of the helmet design: thickness, dimension, type of materials used, etc. Since the absorption of energy to rotational force and translational force as well as velocities of impact are different depending on the helmet design, there is no single design that offers protection at all different types of impact. The thickness of the foam and the dimensions of the helmet were shown to be important for determining the energy absorbed by the helmet and the rates of concussion. Improvements in helmet design continue as seen in the evolution of football helmets. As summarized in this review, there have been many studies showing the different levels of protection provided by the helmets and headgears assessed by biomechanical models. Many studies have reported promising results regarding helmets and concussion and head injury rates in skiing/snowboarding, baseball, hockey and bicycling. Although not as extensively studied as football helmets, the designs have improved over the years and the level of protection has also enhanced. Catastrophic head injuries have decreased in sports, but despite this, concussions still do occur and can result in long-lasting sequelae. There have not been extensive developments or investigations in several other sports, such as rodeo, soccer and rugby mainly due to the lack of popularity of head protective gears in these fields. With further developments in helmet design and increased awareness of the prevalence of head injury in sports, we believe that athletes will have more protection from head injury in the decades to come.

Conclusion Further outcomes research in the varying sports remains necessary to support individual mandates for headgear and helmet use. Evolving technological advances and design improvement must continue to be evaluated and pursued. Onfield monitoring, lab tests that better simulate game impact and novel materials will continue to be investigated. It is implausible that personal protective equipment, including helmets, will fully eliminate the risk of concussions, so nonequipment-based methods of concussion prevention must also be identified and promoted. Organizations such as the

DOI: 10.1080/00913847.2015.1039922

National Football League (NFL) and NHL have already enacted rule changes penalizing illegal hits and enforcing fines and suspensions. Rules must continue to be adjusted as necessary and strictly enforced. Education regarding the signs and symptoms of concussions must be spread to coaches, players and parents and the return to play protocol followed by treatment for players overseen by properly trained medical personnel. It is through these protective measures, including proper helmet usage, that a safe environment for athletes of all ages and skill levels will be secured.

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Declaration of interest The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending or royalties.

References [1] Lawson BR, Comstock RD, Smith GA. Baseball-related injuries to children treated in hospital emergency departments in the United States, 1994-2006. Pediatrics 2009;123:e1028–34. [2] Zagelbaum BM, Hersh PS, Donnenfeld ED, Perry HD, Hochman MA. Ocular trauma in major-league baseball players. N Engl J Med 1994;330:1021–3. [3] Mueller FO, Marshall SW, Kirby DP. Injuries in little league baseball from 1987 through 1996: implications for prevention. Phys Sportsmed 2001;29:41–8. [4] Nicholls RL, Elliott BC, Miller K. Impact injuries in baseball : prevalence, aetiology and the role of equipment performance. Sports Med 2004;34:17–25. [5] Beyer JA, Rowson S, Duma SM. Concussions experienced by Major League Baseball catchers and umpires: field data and experimental baseball impacts. Ann Biomed Eng 2012;40:150–9. [6] Shain KS, Madigan ML, Rowson S, Bisplinghoff J, Duma SM. Analysis of the ability of catcher’s masks to attenuate head accelerations on impact with a baseball. Clin J Sport Med 2010;20:422–7. [7] Stretch RA, Bartlett R, Davids K. A review of batting in men’s cricket. J Sports Sci 2000;18:931–49. [8] Finch C, Valuri G, Ozanne-Smith J. Sport and active recreation injuries in Australia: evidence from emergency department presentations. Br J Sports Med 1998;32:220–5. [9] Walker HL, Carr DJ, Chalmers DJ, Wilson CA. Injury to recreational and professional cricket players: circumstances, type and potential for intervention. Accid Anal Prev 2010;42:2094–8. [10] Wani AA, Ramzan AU, Tariq R, Kirmani AR, Bhat AR. Head injury in children due to cricket ball scenario in developing countries. Pediatr Neurosurg 2008;44:204–7. [11] McIntosh AS, Janda D. Evaluation of cricket helmet performance and comparison with baseball and ice hockey helmets. Br J Sports Med 2003;37:325–30. [12] Ranson C, Peirce N, Young M. Batting head injury in professional cricket: a systematic video analysis of helmet safety characteristics. Br J Sports Med 2013;47:644–8. [13] Ranson C, Young M. Putting a lid on it: prevention of batting helmet related injuries in cricket. Br J Sports Med 2013;47:609–10. [14] Tim W. Final concussions and suspensions list. Available from: www.cbc.ca/sports.com. 2012. Accessed February 12, 2015. [15] Benson BW, Meeuwisse WH, Rizos J, Kang J, Burke CJ. A prospective study of concussions among National Hockey League players during regular season games: the NHL-NHLPA Concussion Program. CMAJ 2011;183:905–11.

Helmets and concussion

9

[16] Wennberg RA, Tator CH. Concussion incidence and time lost from play in the NHL during the past ten years. Can J Neurol Sci 2008;35:647–51. [17] Tegner Y, Lorentzon R. Concussion among Swedish elite ice hockey players. Br J Sports Med 1996;30:251–5. [18] Hootman JM, Dick R, Agel J. Epidemiology of collegiate injuries for 15 sports: summary and recommendations for injury prevention initiatives. J Athl Train 2007;42:311–19. [19] Agel J, Harvey EJ. A 7-year review of men’s and women’s ice hockey injuries in the NCAA. Can J Surg 2010;53:319–23. [20] Flik K, Lyman S, Marx RG. American collegiate men’s ice hockey: an analysis of injuries. Am J Sports Med 2005;33:183– 7. [21] Rishiraj N, Lloyd-Smith R, Lorenz T, Niven B, Michel M. University men’s ice hockey: rates and risk of injuries over 6-years. J Sports Med Phys Fitness 2009;49:159–66. [22] Echlin PS, Skopelja EN, Worsley R, Dadachanji SB, Lloyd-Smith DR, Taunton JA, et al. A prospective study of physician-observed concussion during a varsity university ice hockey season: incidence and neuropsychological changes. Part 2 of 4. Neurosurg Focus 2012;33:E2: 1–11. [23] Marar M, McIlvain NM, Fields SK, Comstock RD. Epidemiology of concussions among United States high school athletes in 20 sports. Am J Sports Med 2012;40:747–55. [24] Kraus JF, Anderson BD, Mueller CE. The effectiveness of a special ice hockey helmet to reduce head injuries in college intramural hockey. Med Sci Sports 1970;2:162–4. [25] Biasca N, Wirth S, Tegner Y. The avoidability of head and neck injuries in ice hockey: an historical review. Br J Sports Med 2002;36:410–27. [26] Yoganandan N, Pintar FA. Biomechanics of temporo-parietal skull fracture. Clin Biomech (Bristol, Avon) 2004;19:225–39. [27] Hoshizaki TB, Brien SE. The science and design of head protection in sport. Neurosurgery 2004;55:956–66; discussion 966-957. [28] Post A, Oeur A, Hoshizaki B, Gilchrist MD. Examination of the relationship between peak linear and angular accelerations to brain deformation metrics in hockey helmet impacts. Comput Methods Biomech Biomed Engin 2013;16:511–19. [29] Allison MA, Kang YS, Bolte JH 4th, Maltese MR, Arbogast KB. Validation of a helmet-based system to measure head impact biomechanics in ice hockey. Med Sci Sports Exerc 2014;46:115–23. [30] Allison MA, Kang YS, Maltese MR, Bolte JH 4th, Arbogast KB. Measurement of Hybrid III Head Impact Kinematics Using an Accelerometer and Gyroscope System in Ice Hockey Helmets. Ann Biomed Eng 2014;Epub ahead of print. [31] Stevens ST, Lassonde M, de Beaumont L, Keenan JP. The effect of visors on head and facial injury in National Hockey League players. J Sci Med Sport 2006;9:238–42. [32] Benson BW, Rose MS, Meeuwisse WH. The impact of face shield use on concussions in ice hockey: a multivariate analysis. Br J Sports Med 2002;36:27–32. [33] Asplund C, Bettcher S, Borchers J. Facial protection and head injuries in ice hockey: a systematic review. Br J Sports Med 2009;43:993–9. [34] Haider AH, Saleem T, Bilaniuk JW, Barraco RD; Eastern Association for the Surgery of Trauma Injury Control Violence Prevention Committee. An evidence-based review: efficacy of safety helmets in the reduction of head injuries in recreational skiers and snowboarders. J Trauma Acute Care Surg 2012;73:1340–7. [35] Mueller BA, Cummings P, Rivara FP, Brooks MA, Terasaki RD. Injuries of the head, face, and neck in relation to ski helmet use. Epidemiology 2008;19:270–6. [36] Hagel BE, Goulet C, Platt RW, Pless IB. Injuries among skiers and snowboarders in Quebec. Epidemiology 2004;15:279–86. [37] Ackery A, Hagel BE, Provvidenza C, Tator CH. An international review of head and spinal cord injuries in alpine skiing and snowboarding. Inj Prev 2007;13:368–75. [38] Sibbald B. Yes to ski helmets, but buyer beware. CMAJ 2012;184:627.

The Physician and Sportsmedicine Downloaded from informahealthcare.com by Nyu Medical Center on 06/24/15 For personal use only.

10

C. M. Bonfield et al.

[39] Graves JM, Whitehill JM, Stream JO, Vavilala MS, Rivara FP. Emergency department reported head injuries from skiing and snowboarding among children and adolescents, 1996-2010. Inj Prev 2013;19:399–404. [40] Macnab AJ, Smith T, Gagnon FA, Macnab M. Effect of helmet wear on the incidence of head/face and cervical spine injuries in young skiers and snowboarders. Inj Prev 2002;8:324–7. [41] Hagel BE, Pless IB, Goulet C, Platt RW, Robitaille Y. Effectiveness of helmets in skiers and snowboarders: case-control and case crossover study. BMJ 2005;330:281. [42] Sulheim S, Holme I, Ekeland A, Bahr R. Helmet use and risk of head injuries in alpine skiers and snowboarders. JAMA 2006;295:919–24. [43] Fukuda O, Hirashima Y, Origasa H, Endo S. Characteristics of helmet or knit cap use in head injury of snowboarders. Neurol Med Chir (Tokyo) 2007;47:491–4; discussion 494. [44] Greve MW, Young DJ, Goss AL, Degutis LC. Skiing and snowboarding head injuries in 2 areas of the United States. Wilderness Environ Med 2009;20:234–8. [45] Rughani AI, Lin CT, Ares WJ, Cushing DA, Horgan MA, Tranmer BI, et al. Helmet use and reduction in skull fractures in skiers and snowboarders admitted to the hospital. J Neurosurg Pediatr 2011;7:268–71. [46] Russell K, Christie J, Hagel BE. The effect of helmets on the risk of head and neck injuries among skiers and snowboarders: a meta-analysis. CMAJ 2010;182:333–40. [47] Shealy JE, Johnson RJ, Ettlinger CF. Head trauma and helmet usage in alpine skiing [abstract]. 16th International Society of Skiing Safety Conference, Nigata, Japan. Knee Surg Sports Traumatol Arthrosc 14:97. [48] Shealy JE, Johnson RJ, Ettlinger CF. Do helmets reduce fatalities or merely alter the patterns of death? J ASTM Int 2008;5:1–4. [49] Commission UCPS. Skiing helmets: an evaluation of the potential to reduce head injury. U.S. Consumer product safety commision, Washington, D.C., 1999. [50] Hennessey T, Morgan SJ, Elliot JP, Offner PJ, Ferrari JD. Helmet availability at skiing and snowboarding rental shops. a survey of Colorado ski resort rental practices. Am J Prev Med 2002;22:110–12. [51] Cusimano MD, Kwok J. The effectiveness of helmet wear in skiers and snowboarders: a systematic review. Br J Sports Med 2010;44:781–6. [52] Downey DJ. Rodeo injuries and prevention. Curr Sports Med Rep 2007;6:328–32. [53] Butterwick DJ, Hagel B, Nelson DS, LeFave MR, Meeuwisse WH. Epidemiologic analysis of injury in five years of Canadian professional rodeo. Am J Sports Med 2002;30:193–8. [54] Brandenburg MA, Archer P. Survey analysis to assess the effectiveness of the bull tough helmet in preventing head injuries in bull riders: a pilot study. Clin J Sport Med 2002;12:360–6. [55] Bond GR, Christoph RA, Rodgers BM. Pediatric equestrian injuries: assessing the impact of helmet use. Pediatrics 1995;95:487–9. [56] Butterwick DJ, Brandenburg MA, Andrews DM, Brett K, Bugg BH, Carlyle KJ, et al. Agreement statement from the 1st international rodeo research and clinical care conference: Calgary, Alberta, Canada (July 7-9, 2004). Clin J Sport Med 2005;15:192–5. [57] Mock CN, Maier RV, Boyle E, Pilcher S, Rivara FP. Injury prevention strategies to promote helmet use decrease severe head injuries at a level I trauma center. J Trauma 1995;39:29–33; discussion 34-25. [58] Cook A, Sheikh A. Trends in serious head injuries among cyclists in England: analysis of routinely collected data. BMJ 2000;321:1055. [59] McDermott FT, Lane JC, Brazenor GA, Debney EA. The effectiveness of bicyclist helmets: a study of 1710 casualties. J Trauma 1993;34:834–44; discussion 844-835. [60] Abu-Zidan FM, Nagelkerke N, Rao S. Factors affecting severity of bicycle-related injuries: the role of helmets in preventing head injuries. Emerg Med Australas 2007;19:366–71. [61] Linn S, Smith D, Sheps S. Epidemiology of bicycle injury, head injury, and helmet use among children in British Columbia:

Phys Sportsmed, 2015; Early Online:1–11

[62] [63]

[64] [65]

[66] [67] [68] [69] [70] [71]

[72]

[73] [74]

[75] [76] [77] [78] [79] [80] [81] [82] [83] [84]

[85]

a five year descriptive study. Canadian Hospitals Injury, Reporting and Prevention Program (CHIRPP). Inj Prev 1998;4:122–5. Heng KW, Lee AH, Zhu S, Tham KY, Seow E. Helmet use and bicycle-related trauma in patients presenting to an acute hospital in Singapore. Singapore Med J 2006;47:367–72. Amoros E, Chiron M, Martin JL, Thelot B, Laumon B. Bicycle helmet wearing and the risk of head, face, and neck injury: a French case–control study based on a road trauma registry. Inj Prev 2012;18:27–32. Thompson RS, Rivara FP, Thompson DC. A case-control study of the effectiveness of bicycle safety helmets. N Engl J Med 1989;320:1361–7. Maimaris C, Summers CL, Browning C, Palmer CR. Injury patterns in cyclists attending an accident and emergency department: a comparison of helmet wearers and non-wearers. BMJ 1994;308:1537–40. Dorsch MM, Woodward AJ, Somers RL. Do bicycle safety helmets reduce severity of head injury in real crashes? Accid Anal Prev 1987;19:183–90. Wasserman RC, Buccini RV. Helmet protection from head injuries among recreational bicyclists. Am J Sports Med 1990;18:96–7. Rivara FP, Thompson DC, Thompson RS. Epidemiology of bicycle injuries and risk factors for serious injury. Inj Prev 1997;3:110–14. Finvers KA, Strother RT, Mohtadi N. The effect of bicycling helmets in preventing significant bicycle-related injuries in children. Clin J Sport Med 1996;6:102–7. Berg P, Westerling R. A decrease in both mild and severe bicycle-related head injuries in helmet wearing ages–trend analyses in Sweden. Health Promot Int 2007;22:191–7. Shafi S, Gilbert JC, Loghmanee F, Allen JE, Caty MG, Glick PL, et al. Impact of bicycle helmet safety legislation on children admitted to a regional pediatric trauma center. J Pediatr Surg 1998;33:317–21. Cripton PA, Dressler DM, Stuart CA, Dennison CR, Richards D. Bicycle helmets are highly effective at preventing head injury during head impact: Head-form accelerations and injury criteria for helmeted and unhelmeted impacts. Accid Anal Prev 2014;70:1–7. Williams M. The protective performance of bicyclists’ helmets in accidents. Accid Anal Prev 1991;23:119–31. Depreitere B, Van Lierde C, Vander Sloten J, Van der Perre G, Van Audekercke R, Plets C, Goffin J. Lateral head impacts and protection of the temporal area by bicycle safety helmets. J Trauma 2007;62:1440–5. Hansen KS, Engesaeter LB, Viste A. Protective effect of different types of bicycle helmets. Traffic Inj Prev 2003;4:285–90. Curnow WJ. Bicycle helmets: lack of efficacy against brain injury. Accid Anal Prev 2006;38:833–4. Elvik R. Publication bias and time-trend bias in meta-analysis of bicycle helmet efficacy: a re-analysis of Attewell, Glase and McFadden, 2001. Accid Anal Prev 2011;43:1245–51. Rivara FP, Astley SJ, Clarren SK, Thompson DC, Thompson RS. Fit of bicycle safety helmets and risk of head injuries in children. Inj Prev 1999;5:194–7. Attewell RG, Glase K, McFadden M. Bicycle helmet efficacy: a meta-analysis. Accid Anal Prev 2001;33:345–52. Nightingale RW, Richardson WJ, Myers BS. The effects of padded surfaces on the risk for cervical spine injury. Spine 1997;22:2380–7. Niedfeldt MW. Head injuries, heading, and the use of headgear in soccer. Curr Sports Med Rep 2011;10:324–9. Naunheim RS, Ryden A, Standeven J, Genin G, Lewis L, Thompson P, Bayly P. Does soccer headgear attenuate the impact when heading a soccer ball? Acad Emerg Med 2003;10:85–90. Withnall C, Shewchenko N, Gittens R, Dvorak J. Biomechanical investigation of head impacts in football. Br J Sports Med 2005;39:i49–57. Delaney JS, Al-Kashmiri A, Drummond R, Correa JA. The effect of protective headgear on head injuries and concussions in adolescent football (soccer) players. Br J Sports Med 2008;42:110–15; discussion 115. Broglio SP, Ju YY, Broglio MD, Sell TC. The efficacy of soccer headgear. J Athl Train 2003;38:220–4.

The Physician and Sportsmedicine Downloaded from informahealthcare.com by Nyu Medical Center on 06/24/15 For personal use only.

DOI: 10.1080/00913847.2015.1039922

[86] Olson DE, Sikka RS, Hamilton A, Krohn A. Football injuries: current concepts. Curr Sports Med Rep 2011;10:290–8. [87] Daneshvar DH, Baugh CM, Nowinski CJ, McKee AC, Stern RA, Cantu RC. Helmets and mouth guards: the role of personal equipment in preventing sport-related concussions. Clin Sports Med 2011;30:145–63; x. [88] Levy ML, Ozgur BM, Berry C, Aryan HE, Apuzzo ML. Birth and evolution of the football helmet. Neurosurgery 2004;55:656–61; discussion 661-652. [89] Alles WF, Powell JW, Buckley W, Hunt EE. The national athletic injury/illness reporting system 3-year findings of high school and college football injuries*. J Orthop Sports Phys Ther 1979;1:103–8. [90] Zemper ED. Analysis of cerebral concussion frequency with the most commonly used models of football helmets. J Athl Train 1994;29:44–50. [91] Torg JS, Harris SM, Rogers K, Stilwell GJ. Retrospective report on the effectiveness of a polyurethane football helmet cover on the repeated occurrence of cerebral concussions. Am J Orthop (Belle Mead NJ) 1999;28:128–32. [92] Collins M, Lovell MR, Iverson GL, Ide T, Maroon J. Examining concussion rates and return to play in high school football players wearing newer helmet technology: a three-year prospective cohort study. Neurosurgery 2006;58:275–86; discussion 275-286. [93] Rowson S, Duma SM, Greenwald RM, Beckwith JG, Chu JJ, Guskiewicz KM, et al. Can helmet design reduce the risk of concussion in football? J Neurosurg 2014;120:919–22. [94] Viano DC, Withnall C, Halstead D. Impact performance of modern football helmets. Ann Biomed Eng 2012;40:160–74. [95] Bartsch A, Benzel E, Miele V, Prakash V. Impact test comparisons of 20th and 21st century American football helmets. J Neurosurg 2012;116:222–33. [96] Rowson S, Daniel RW, Duma SM. Biomechanical performance of leather and modern football helmets. J Neurosurg 2013;119:805–9. [97] Pellman EJ, Viano DC, Withnall C, Shewchenko N, Bir CA, Halstead PD. Concussion in professional football: helmet testing to assess impact performance–part 11. Neurosurgery 2006;58:78–96; discussion 78-96. [98] Hoshizaki TB, Post A, Oeur RA, Brien SE. Current and future concepts in helmet and sports injury prevention. Neurosurgery 2014;75:S136–48.

Helmets and concussion

11

[99] Rowson S, Duma SM. Development of the STAR evaluation system for football helmets: integrating player head impact exposure and risk of concussion. Ann Biomed Eng 2011;39:2130–40. [100] McCrea M, Hammeke T, Olsen G, Leo P, Guskiewicz K. Unreported concussion in high school football players: implications for prevention. Clin J Sport Med 2004;14:13–17. [101] Hrysomallis C. Injury incidence, risk factors and prevention in Australian rules football. Sports Med 2013;43:339–54. [102] Marshall SW, Waller AE, Dick RW, Pugh CB, Loomis DP, Chalmers DJ. An ecologic study of protective equipment and injury in two contact sports. Int J Epidemiol 2002;31:587–92. [103] Pettersen JA. Does rugby headgear prevent concussion? Attitudes of Canadian players and coaches. Br J Sports Med 2002;36:19–22. [104] Kahanov L, Dusa MJ, Wilkinson S, Roberts J. Self-reported headgear use and concussions among collegiate men’s rugby union players. Res Sports Med 2005;13:77–89. [105] Hollis SJ, Stevenson MR, McIntosh AS, Shores EA, Collins MW, Taylor CB. Incidence, risk, and protective factors of mild traumatic brain injury in a cohort of Australian nonprofessional male rugby players. Am J Sports Med 2009;37:2328–33. [106] Kemp SP, Hudson Z, Brooks JH, Fuller CW. The epidemiology of head injuries in English professional rugby union. Clin J Sport Med 2008;18:227–34. [107] McIntosh AS, McCrory P. Effectiveness of headgear in a pilot study of under 15 rugby union football. Br J Sports Med 2001;35:167–9. [108] Marshall SW, Loomis DP, Waller AE, Chalmers DJ, Bird YN, Quarrie KL, Feehan M. Evaluation of protective equipment for prevention of injuries in rugby union. Int J Epidemiol 2005;34:113–18. [109] McIntosh AS, McCrory P, Finch CF, Best JP, Chalmers DJ, Wolfe R. Does padded headgear prevent head injury in rugby union football? Med Sci Sports Exerc 2009;41:306–13. [110] McIntosh A, McCrory P, Finch CF. Performance enhanced headgear: a scientific approach to the development of protective headgear. Br J Sports Med 2004;38:46–9. [111] McIntosh AS, McCrory P. Impact energy attenuation performance of football headgear. Br J Sports Med 2000;34:337–41.

Helmets, head injury and concussion in sport.

Research on the mechanism of concussion in recent years has been focused on the mechanism of injury as well as strategies to minimize or reverse injur...
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