Welcome to UAB MedCast, a continuing education podcast for medical professionals. Providing knowledge that is moving medicine forward. Here's Melanie Cole.

Melanie Cole (Host): Welcome to UAB MedCast. I'm Melanie Cole. And joining me, we have a panel today with Dr. Kevin Schrum, he's a research scientist 1 in mechanical and materials engineering; and Dr. Sara Gould, she's a sports medicine physician in the Department of Orthopedic Surgery and she's an associate professor, and they're both with UAB Medicine. They're here today to highlight equestrian helmet, facts, fiction, and future research.

Doctors, thank you so much. I'm fascinated with this topic today. Dr. Gould, as we set the stage, I'd like you to start by telling us a little bit about the injury risk to equestrian athletes. Where in this spectrum of risk does helmet use come into thought? Are they underutilized as with motorcycles? People don't tend to think of this as a high injury sport, but indeed they are. So, tell us a little bit about the scope of what we're discussing here today.

Dr Sara Gould: Sure. Thank you so much for having me. I think that as we learn more and more about head injury throughout all sports, we understand that helmets are so important for preventing all different types of injuries, ranging from concussion to traumatic subarachnoid hemorrhage. So, there is a very large spectrum of head injury that we can see associated with sports and equestrian sports in particular.

The US National Trauma Registry tracks injuries associated with sport. And of sports, they found something around 40-45% of sports-related head injuries were related to equestrian events. And so, it does carry a significant risk. And there's things that we can do to mitigate that. And so, we're trying to make helmets safer. We clearly know that you should definitely be wearing a helmet if you're going to engage in this sport. All of the science points towards concussion, skull fracture, different types of risks that can be diminished through consistent helmet usage. And because you're dealing with an animal, even the most well-trained, experienced animal can be unpredictable and reactive. And so, it's really important that regardless of experience, people are using helmets consistently.

Melanie Cole (Host): Well, thank you so much for that. Now, Dr. Schrum, you and I were speaking off the air about how this topic even came about and how you and Dr. Gould really met. Can you tell us a little bit about this research and how you two met to start this kind of study?

Dr Kevin Schrum: Yes. Again, thanks for having us on. You don't see necessarily medical school researchers collaborating with mechanical engineers very often, so it is a little bit unique. But I was part of a team several years ago that was investigating concussions in football helmets. And there was this front and center controversial issue with football and traumatic brain injuries and long-term effects that that might have on young players as they grow up and continue playing the sport. And so, we were investigating ways to evaluate football helmets in a more fidelitous manner an actual helmet to helmet body to body collision. And so, we did some work on that. There was some exposure that we gained through that work, published in interviews like on 2020, I think was one outlet. And it's my understanding and Dr. Gould, she can correct me if I'm wrong, but I think she found that in an effort to try to find a way to evaluate equestrian helmets in a more realistic manner without actually knowing that I and my research team were here at UAB, the same institution that she was working for. So, it was kind of a big concept, small world.

Melanie Cole (Host): Meant to be, as they say. Now, Dr. Schrum, sticking with you. Now, you're the mechanical engineer, so I'd like you to speak to other providers here about the importance of studies like this. I want you to tell us what rotational velocity is and why it's a significant variable in relation to head injury. I told you off the air, I'm not great with physics and that sort of thing, but I'd like you to explain it and what it would actually look like as a rider came off a horse and hit the ground. I remember in kinesiology, we did things similar to this in grad school, but I'd like you to speak a little bit about that.

Dr Kevin Schrum: Sure. So, traditional methods to evaluate helmets try to isolate the head form within the helmet. They drop it straight down on an anvil or down a ramp so it can roll, things of that nature. But it's just the helmet and the head form. There isn't the weight of the body behind the head, and that's a significant factor. It creates a whip-like motion. So, you think of your spine as like the body of a whip. And then as you're falling off of a horse and you're landing on the ground with your knees or your lower back, there is a sudden increase in rotational velocity, so that's the measure of a velocity at a point measured at a distance from a center of rotation. So, the further you are away with the same rotational velocity, you're going to have a larger linear velocity.

And that's the true issue that we're looking at, is linear velocity of the head. So, there's how fast you were going before you fell off, and you add to that what you're getting from this snap whip-like action from rotational velocity. And if you think of building on that analogy a little bit, when you crack a whip, that loud noise that you hear, that incredibly loud snap, that's the result of the loop at the end of the whip changing direction suddenly and creating kind of like a sonic boom. And so, that's kind of what's happening with our neck on a smaller scale. Our head is like that loop. And our body or upper torso is the whip itself, right? So then, as you're going towards the ground, if your head snaps into the sand or into the sod or whatever surface there is, and that creates this massive increase in velocity. And that increase in velocity in the skull is going to dramatically increase the rotational velocity of the brain within the skull. So, that creates a bunch of shearing action. The brain itself is trying to move and rotate relative to the skull, causing sheer stresses on the brain tissue, which as Dr. Gould can speak to, is a very high indicator of concussion.

Melanie Cole (Host): Wow. You should have been my biomechanics instructor in college because you make it much easier to understand. Dr. Gould, why don't you expand on that and describe your test procedure, why you believe it's an appropriate evaluation of helmets. Tell us a little bit about the study and expand on what Dr. Schrum was just saying.

Dr Sara Gould: Well, I think Dr. Schrum did an excellent job of kind of breaking it down so as non-engineers can understand. But two concepts that he touched on that I want to kind of really speak to in terms of the physiologic impact is the concept of linear acceleration. And so, that results in kind of a compressive force. And that brain tissue is not a highly compressible material. And so because of that, it can much better withstand a direct hit, like an anvil-type hit, that you might see with typical prior helmet studies. However, it's really the shearing forces, which is where one force pushes the brain or body in one direction and another part of the body in the opposite direction, that the brain really cannot absorb very well. And so, that's rotational acceleration, which is a leading cause of brain injury, because the brain just cannot handle those shearing forces very well.

And so, when I was kind of looking through what's currently available in terms of equestrian helmet testing, I wanted to try to find something that was going to have more high fidelity to real life impacts. And so, I looked at videos of what Dr. Schrum's department had done with these linear and rotational impacts helmet to helmet for football. And I thought we could modify this, and make it so that it really replicates what's happening when an equestrian falls off a horse.

And so, we got together and we had access to some incredibly expensive equipment that we would not otherwise have had access to. Our laboratory is actually located at Barber Motorsports Racetrack. And so, a lot of our equipment that, when it's not being used for equestrian testing, is being used in car impacts and different crash test scenarios. So, we have access to just some really incredible cutting edge equipment that we are modifying to make it more realistic in terms of equestrian helmet testing.

Melanie Cole (Host): This is so cool. What a cool topic we are discussing here today. And Dr. Schrum, tell us a little bit about multi-directional impact protection systems. Were they superior to standard expanded polystyrene foam helmets on your testing? Give us an overview of what that really means and what we're looking at with this helmet testing.

Dr Kevin Schrum: So, the Multi-directional Impact Protection System, you know, commonly referred to as MIPS, was something that we looked into. We didn't necessarily conclude that it was ineffective, but rather that the less expensive options like expanded polystyrene were potentially as effective. But prior research, specifically with our football helmet work that we had done here at UAB, was largely governed by this rotational acceleration problem. And so, we created a model and ultimately a prototype where the energy absorbing liner could absorb the linear impacts pretty well, but it also allowed for the outer shell to rotate first before the head was able to rotate at all. And so, that created this separation between exterior loading and what the brain itself would feel.

And some other prior research has shown that concussive events are somewhere in the order of eight milliseconds or less, or some type of duration on a very small scale. The MIPS system generally allows for about 10 to 15 millimeters of movement in that shell before the head starts to move. So, it has the same concept as what we saw with football helmets, and it has the potential for being a really good application. But one thing that we'd like to investigate further is the time of the duration to the peak of the loading. And so if the peak occurs before the helmet is moved 10 to 15 millimeters, then you're going to get some pretty good results with the MIPS system. But if the peak occurs beyond 10 to 15 millimeters of movement, then that's when you start to get some shearing of the brain still, and it'd be interesting to kind of look into that a little bit further. But the basic concept of MIPS theoretically is consistent with what we have found in previous research for football. But we would obviously like to do a lot more research.

The most interesting thing I think from our relatively small study was that those relatively inexpensive one-time used polystyrene helmets, still had a pretty good performance. I think MIPS would just build upon that with maybe more testing if we could find a way to isolate that performance.

Melanie Cole (Host): And Dr. Gould, you mentioned Virginia Tech weighted their helmet testing toward low-impact performance. I'd like you to tell us some of the serious injuries that can result from high-impact falls. How would you diagnose those? Speak a little bit about really what is the crux of the reason that we're discussing this here today.

Dr Sara Gould: Sure. So, Virginia Tech just came out with an equestrian star rating, and there's been a lot of discussion around that. And I think that any helmet testing that we're doing, Virginia Tech's; Folksam, which is a Swedish company; even our testing at UAB, I think it's important to highlight that there's still significant gaps in the research and in terms of we know that we can measure these impacts, we can measure how much they're reducing or not reducing the forces. But we still are not at the point where we can say consistently what the clinical impact of that is going to be. And some of the current testing, which was put forth by both Virginia Tech and Folksam, kind of weighs these lower impact injuries because those are the injuries that they feel were more likely to result in concussion, which has been reported to be more prevalent in equestrian sports.

The thing that we need to remember is that there are some really serious spectrum of head injury that can occur, and some of those could include traumatic subarachnoid hemorrhage, which is bleeding in the brain that commonly occurs near the site of a skull fracture and an intercerebral contusion. This is something that has a very high mortality. Risk factors for it can include high blood pressure, family history, family history of connective tissue disorders, and those all put an equestrian at increased risk for sustaining a traumatic subarachnoid hemorrhage if they do sustain a fall. And it's so critically important to try to diagnose these within the first hour of injury. they're usually diagnosed via head CT, which can pick up 99% of the cases if it's performed within a six-hour window. So, it is really important to be aware that there is a very large spectrum of injury that can occur and we have somewhat of a gap between what we're seeing in the lab and what that results in clinically.

Going back to the football analogy, there have been a couple of studies, where they looked at thousands of football players and looked at almost 3000 concussions that occurred in high school football players. And they didn't find a difference in terms of rate of concussion, return to play, injury severity, no difference between different helmet types. And so, I think we have a lot more research that we need to do to try to figure out what the numbers that we're seeing in the lab translate to clinically.

The work is still critically important. We should definitely be doing everything we can to reduce head impacts. What I would hate to see happen is people who don't have access to the four-figure helmets, being kind of boxed out of the sport. And I think that's what I would like people to take away from our research, is that it looks like some of the lower technology, standard foam helmets that were very inexpensive, most of them were around $50, performed equally well in our studies to the much more expensive high technology helmets.

Melanie Cole (Host): This is just absolutely fascinating. And Dr. Schrum, last word to you. I'd like you to speak to other providers about the conditions under which you believe patients really benefit most from the research that you and Dr. Gould are doing. And if they are counseling equestrians on helmet selection, what would you like the key message to be?

Dr Kevin Schrum: Well, I think one thing, kind of building on what Dr. Gould has just said, there's a floor of performance where it seems like even the simple technology and less expensive helmets are still doing some service when you fall off a horse and you hit your head on the ground. So, that's the main takeaway, is that don't skip the helmet. Even if it's slightly uncomfortable, wear the helmet, protect your head, take precautions. But then, we do have the opportunity going forward to evaluate improving technologies and emerging technologies and quantifying the effect that they might have on the physics of a crash, collision with the ground, collision with the stanchions or the poles in jumping events. And we can look at all of that and move forward. So, there's no limit to how far we can go with it. But at a minimum, even the inexpensive helmets can do a lot to mitigate some of these really severe, scary sounding problems that Dr. Gould was describing.

Melanie Cole (Host): Well, thank you for sharing this research. So interesting. And thank you both for sharing your incredible expertise in this area. And for more information, you can visit our website at uabmedicine.org/physician. That concludes this episode of UAB MedCast. I'm Melanie Cole.