Will the data it yields really be that useful for identifying concussions or will it give the world of sports enough rope to hang itself?

Helmet Accelerometers

The recognition and treatment of sports-related concussions has dramatically improved over the last 15 years, thanks in part to the media attention garnered by the NFL (http://www.pbs.org/wgbh/pages/frontline/league-of-denial/ ) as well as "Second Impact Syndrome" and Chronic Traumatic Encephalopathy. Gradually state governments have adopted formal return-to-play guidelines for concussed high-school athletes reflecting international consensus recommendations of the various Zurich conventions.1

Adding to the worry of the parents of high school football players everywhere, McCrea, et al. reported in 2004 in the Clinical Journal of Sports Medicine that over 50% of high school football players with a concussion did not even report their injury to any authority figure. Complicating the situation further is the fact that concussion symptoms can be vague and may not fully evolve for days, leaving sideline personnel often unable to recognize a symptomatic athlete. Still, by far the limiting factor in high-school sports concussion recognition is the shortage of trained physicians available on the scene — not only at games but also at practices where many concussions also occur. When it comes to protecting our young athletes' brains, the world of sports has finally begun to demand a better way.

In the new millennium, researchers have put forth great efforts in the search for an easier way to objectively measure when an athlete is at increased risk or likelihood of having a concussion. Researchers also hope this data will help develop better helmets. This has led to the invention of devices with sensors placed in different positions inside helmets and even in the mouth guards. These sensors measure frequency, location and magnitude of impacts. These devices usually measure acceleration/deceleration as well as rotational forces. Some can also measure the location over the cranium at which impact occurred. In one system, the data is then transmitted wirelessly up to 150 meters away to a receiver on the sidelines. Computer software tracks this data for up to 100 players simultaneously.

Various studies over the last several years have collected data with these expensive systems and, as would be expected, limited access to this new equipment has limited the "n" value in these studies as well as the sheer number of studies and their duration. Nonetheless, there is now a sufficient body of evidence that is compelling some researchers to draw a few conclusions … but others may say that this body of evidence is opening up a can of worms. For example, can data collected on professional adult football players apply to adolescent high school athletes? Can we even compare college players to high school players? Is this computerized data really able to compensate for lack of trained physicians to evaluate the players on the sidelines or is it going to lead to "cut-off points" that fall short of truly identifying those players, thereby leaving them in the game when they should be pulled? Also, by relying on a device that captures only mechanical data, will we be taking our eye "off the ball" of all the unmeasured variables that influence concussion risk such as cerebral blood flow, CSF volume, hydration status, central fatigue, sleep deprivation or concurrent illness?

One of the earliest studies with accelerometers (2003) was penned by the now-infamous rheumatologist-turned-NFL-(former)-lead-concussion-physician Elliot Pellman, et al. (see NFL League of Denial website above).2 His team concluded that the acceleration threshold for concussion was 98g. Nine years later, a study on high school football players captured 13 concussions from a total of roughly 53,600 impacts. It demonstrated that the sheer number of hits that high school players take to the head in one season is astounding. These investigators found that rotation > 5,582 rad/s/s yielded a 1.9% chance of injury while acceleration > 96.1g carried a 6.9% risk of injury. They also concluded that blows to the top, front or side of helmet increased risk to 13.4%.3 [One might ask what part of the helmet is left out of that one?] If Pellman's cut-off was applied to the high school dataset, only 3.5% of the concussions would have been detected. [One may also ask how many concussions that cut-off value was really capturing in the NFL at that time.] One of the largest and longest term studies was done on 314 college football players over three seasons (games and practices).4 It promoted a scoring system using a constellation of variables in addition to acceleration and rotation for a total score. It is generally felt that these types of combination methods are more reliable for capturing risk but if the cut-off value of 63 in this college study was applied to the high school data set, it would have only caught 6% of the high-school concussions.5

It now seems objectively evident that one cannot compare accelerometer data for high school vs. college vs. professional athletes for threshold of concussion risk, but these studies have yielded some data that may apply across this spectrum. For example, intensity of impacts depends on position played, with defensive linemen receiving the hardest hits by far. Impacts in games tend to be slightly more intense than those in practice. While the frequency of impacts is comparable between high school and college athletes, the college player sustains more high-intensity blows and they seem to be able to tolerate them without a comparable increase in injury. However, when one considers a study that suggested college football players fail to report their concussion symptoms up to 80% of the time, one may question this last claim.

The advent of this new equipment comes with a relative "awakening" in the recognition and treatment of mild traumatic brain injury/concussion and the gravity of its sequelae. Will this fancy equipment be promoted as a must-have in the future for colleges and high school sports programs? Will the data it yields really be that useful for identifying concussions or will it give the world of sports enough rope to hang itself? How will the cost of sports programs be impacted by this and what part of a school budget/tuition may suffer in order to pay for this? With all the attention of retired NFL players now struggling with early dementia and chronic traumatic encephalopathy, what schools would dare deny investment in these systems if they are later touted to "protect" our kids? Can they really protect our kids? As the mother of a middle school boy who must soon choose a competitive sport in his school until he graduates, I can't help but ask him, "Have you ever thought about swimming?”

Wendy E. Goodwin, MDW. E. Goodwin is a physician who is board certified in both (adult) Physical Medicine & Rehabilitation and Pediatric Rehabilitation Medicine. She consults and testifies in cases regarding children who are injured, severely ill, or are mentally challenged.

1. McCrory P, Meeuwisse WH, Aubry M, et al. Consensus statement on concussion in sport: the 4th International Conference on Concussion in Sport, Zurich, November 2012. Clin J Sport Med. 2013;23(2):89–117. doi:10.4085/1062-6050-48.4.05.
2. Pellman E. Concussion in Professional Football: Reconstruction of Game Impacts and Injuries. Neurosurgery. 2003;53(4):799 – 814. doi:10.1227/01.NEU.0000083559.68424.3F.
3. Broglio SP, Eckner JT, Kutcher JS. Field-based measures of head impacts in high school football athletes. Curr Opin Pediatr. 2012;24(6):702–8. doi:10.1097/MOP.0b013e3283595616.
4. Crisco JJ, Wilcox BJ, Beckwith JG, et al. Head impact exposure in collegiate football players. J Biomech. 2011;44(15):2673–8. doi:10.1016/j.jbiomech.2011.08.003.
5. Schnebel B, Gwin JT, Anderson S, Gatlin R. In vivo study of head impacts in football: a comparison of National Collegiate Athletic Association Division I versus high school impacts. Neurosurgery. 2007;60(3):490–5; discussion 495–6. doi:10.1227/01.NEU.0000249286.92255.7F.