A Football Helmet Prototype that Reduces Linear and Functional Acceleration through the Addition of an Outer Shell, to be presented by Scott Zuckerman. Thank you very much. We're very grateful for the opportunity to speak. I'm a PGY-6 at Vanderbilt, and really excited to present the results of a study looking at a helmet prototype to reduce rotational acceleration. These are disclosures, none of which are directly relevant to this talk. So before, this is a year-long, year-and-a-half-long project. I just have to acknowledge our co-authors. We did all our helmet testing with a brilliant engineer, Dave Halstead, in Knoxville, Tennessee, his helmet testing center, so a major thank you to him. Our neuroscientist, PhD, Bryson Reynolds, our PGY-2 resident, Aaron Yengokon, and student Andrew Kuhn, and the Vanderbilt undergraduate engineering students that helped us with this project, who really deserve the most credit. We're very lucky to have them part of our team, and really did an outstanding job on this project. So we just heard from Dr. Joseph, sport-related concussion, it's a major problem, and the sport in the United States that bears the brunt of this problem is football. We hear about it every day. And even though the NFL gets the most attention, there are 2,000 pro players in the country, but there are about 1.3 million high school and peewee football players. So that's where the problem really rests, at the high school and youth level. And so when you're trying to prevent, again, sports concussion, you can look at neurocognitive testing symptoms, but helmet analysis and studying football helmets is a way that we decided to look at it. And as we just heard, the two ways you really assess how much a helmet protects against brain injury is two surrogates of acceleration, linear acceleration and rotational acceleration. Linear acceleration just being a head-on collision in one plane, which is much less like what happens in the game, which is rotational acceleration, where there's a hit off the side of the head or the ground, much higher forces. And it's thought that this rotational acceleration is really the culprit most responsible for severe brain injuries and the more severe concussions due to the initial impact and then the rotation that occurs in the brain. So we chose to ask the question, how can football helmets improve safety? And a lot of new helmets out there are using this idea of an outer shell technology. The helmet right here, this is an older helmet. There's one continuous shell with some foam, and you'll see on impact, the force is transmitted from the helmet to the head and the brain moves around a fair amount in the skull. This is the VCs newer helmet that uses the outer shell technology. You'll see the outer shell here absorbs the impact. The inner shell gets the brunt of it and the head is fairly protected. There's not much movement of the head, meaning less movement of the brain inside the skull. These are some of the newer helmets that all showcase this outer shell technology. And I'll tell you, I'll encourage you to go to these websites and they have a lot of very fancy and impressive marketing, but there's not a lot of data. There's not a lot of empiric data that says why these helmets are working or how we can improve them. So when you start a project, you look to the literature, what's already out there. This is one of the few studies published in the Hawaii Journal of Medicine and Public Health that applied an outer foam to football helmets, subjected them to about 90 impacts and found that adding foam to the outside of a helmet reduced linear acceleration a fair amount, less so rotational acceleration, furthering that notion that rotational acceleration is really hard to attenuate. A more recent study that came out was a study looking at the Guardian cap. This is a device that's just worn on the outside of preexisting helmets. And what this study found is a laboratory test that only looked at linear acceleration and they found that in the lab there was no difference between helmets wearing the Guardian cap and those without. So this is a little bit of literature that's out there and drove us to these two questions. Using this outer shell theory, we wanted to answer two questions. The first is what is the optimal material to use for an outer shell if designing a new football helmet? And the second, then once we found this material, how can we examine it and does it actually work to prevent against linear and rotational acceleration? So our methods, this is a laboratory-based engineering investigation. We used Vanderbilt XL Rydell Revolution helmets. And the first material we looked at was foam. That's in most helmets, most football helmets, most other protective helmets. And we used these three types of foam that are commonly used in other protective headgear. And the short story here is that when we tested them, there was really no significant difference between a control and using these foam pads, as you can see in this increasing weights dropped and the force attenuated. No difference between foam. So after we abandoned that hypothesis, we looked to non-Newtonian materials. And to summarize that, non-Newtonian materials are materials that don't behave like a solid or a liquid. They have properties of both. Their response to shear, response to stress is not constant. And the two materials we looked at were Dow Corning Dilatant Compound and Asorbathane Compound. These are used in other protective materials in the military, and they're relatively inexpensive to get. And that's why we used them for our study. They're also different in two very important ways. The Dow Corning Compound is what's called a shear thickening compound. The easiest way to explain this is a picture like honey. When you stir honey, when you apply force, it gets thicker. So when you apply force, it gets more viscous. Compare that to Asorbathane Compound, which is shear thinning. Think of that as paint. When you put paint on a wall, it gets less viscous. So when you apply force, it gets more fluid and less viscous. So those were two different types of non-Newtonian materials that we decided to test. And when we compared the two, basically we found Asorbathane was the superior compound. It had a 10% force reduction to different drop tests. The Dow Corning Compound, the shear thickening, was much more likely to undergo permanent deformation, but the sorbathane was able to return to its resting state. Then we asked the question, what's the ideal grade of the sorbathane? There are several different Duro grades. That's just a measure of hardness. And what we found using a hydraulic testing system and a force displacement curve, force on the y-axis, displacement on the x, the highest energy dissipation was with the highest grade sorbathane, 70-Duro sorbathane. So with that in mind, we were able to determine that the 70-Duro sorbathane compound, a non-Newtonian material, was going to be optimal for trying to design this helmet. The second question, we still didn't have the answer to. So now we had to create the helmet. So we created these energy dissipating pods, which is basically just sorbathane wrapped in these vinyl coverings. And we chose three locations on the helmet that are the highest rates of impacts on really high school football, but collegiate to some extent as well. And that's the front boss location, the side, and the back. And that's how we assembled these helmets, with five different impacts at three locations. And we subjected them to testing at that helmet center that I alluded to earlier. These are videos of such that. This is the front boss location, which is more of a glancing blow, thought to mimic rotational acceleration. This is a direct side, and this is a back, and you'll see each impact is right on that energy dissipating pod. And our results are summarized here, and we were pretty excited about them. So here we see the front boss, side, and back location. Here's linear and rotational acceleration. And what we see is at the front boss location, we had about a 50% reduction in rotational acceleration, 9,000 rads per second squared compared to 4,000. And there was a similar decrease in linear acceleration, but much more for rotation. And that's seen here graphically. The side, we only saw a reduction in linear acceleration, not rotation. And the back, the results were equal between both. So we can conclude that with this non-Newtonian material, the shear thickening sorbethane material, rotational acceleration was attenuated. And we hypothesize that it's this front boss location showed the biggest difference because that was the only location we chose that mimicked rotational acceleration. So looking at the future, this is exciting, but it's far from game ready. This is still a prototype. Right now, we're trying to implement this into a practice or a game setting, or at least maybe not a game setting, but a situation where a player can wear a helmet like this to see if it can be even suitable for play. I think it's also important to determine what's the clinical versus statistical significance. We saw some nice p-values, but does this result in anything meaningful for a concussion threshold or reducing symptoms? And the last point is probably the most important. I understand why a lot of these helmet companies don't share their data and don't make it public because it's proprietary. But if we can get this data out there in the scientific community, then we can learn more about football helmets and make the game safer for our youth. So thank you very much for your time. Thank you for the event. And I just have to close with I look forward to seeing everyone in June so we can repeat our softball championship. Then it'll be there. Thank you. All right.

football helmet

rotational acceleration

safety

concussions

sorbethane