On tooth technology signals head injuries in contact sport

Could cutting-edge technology be about to dramatically reduce the devastating impact of concussion in sport? Repeated head knocks in collision sports like rugby can cause traumatic brain injuries, and enough of those TBIs might add up to dementia later in life. This is what the former Wales rugby international, Alix Popham, who was diagnosed with dementia at the age of 40, had to tell us about his own experience recently...

Alix - I didn't know a lot about concussion or traumatic brain injury. I thought that I had two big KO's that were my concussion, so I didn't think I was that unlucky. I started talking to players that I played with, players I played against, my mum and dad, people I knew, and they were saying, 'What about this one? What about that one?' I had no recollection. The big one in all of this is the silent killer, and that's the sub-concussive hits, and that is literally every contact that you're involved in which is causing a small amount of damage. And the amount of contact we did as players during my career was insane.

That was Alix Popham speaking to us earlier this year.

Now, many contact sports are attempting to manage the risk of serious brain damage by  trialling the use of new technology, including impact-sensing smart mouth guards, and AI. I’ve been speaking to World Rugby’s chief medical officer, Dr Eanna Falvey. I began by asking him to explain how rugby is using science to help tackle concussion:

Eanna - We started this journey three years ago. We went to New Zealand in the middle of Covid because New Zealand were the only country playing rugby at that point in time. We looked at under thirteens, under fifteens, under eighteens and adult players in the community and we put an instrumented mouth guard in over 600 athletes' mouths and we measured what it looked like to be a rugby player. Following on from that journey, we went and looked at this in the adult elite game and what we've been able to deduce from this information is that we can accurately measure head acceleration events. That is how your head reacts to a head impact. The first thing we're going to be able to do is use this to identify those big impact events that we need to be having a look at. Right now, we have a process for diagnosing concussion in rugby where the person, if they have a suspected concussion, comes off in the match, they have an assessment performed, they either go back or they stay off after the game, they're assessed again, and at 36 hours they're assessed again. At the moment, about one in six of our concussions actually present either after the game or at 36 hours. So there are events that have occurred in the match, but the player didn't show an obvious sign or symptom and then came up after the game and said, 'I don't feel well' or, at 36 hours had symptoms. We want to know about this earlier. Just the weekend gone by, we have used this in the WXV, which is a women's international tournament. One of our Italian players, who had an event, nothing was noticed by the doctor or the independent match day doctor, but the mouth guard alerted, the player was removed, and has actually subsequently been confirmed as having had a concussion event. So that's exactly what we're after. There's a second role for this and that role is looking at what we call chronic load, which is how often you hit your head over the course of a week, a month, a season, or a career. We now know that we can accurately measure it. So to reduce something you first have to measure, you have to understand why it's happening, what the causes are, what are the types of activities in the game that cause the big events? Most often we know this is the tackle followed by the ruck. So what can we do with the tackle in the ruck to make them safer and to reduce the head impact events that occur?

Chris - How does the technology actually work?

Eanna - There are two distinct technologies. There are basically gyroscopes and accelerometers which measure the movement, and there's a second technology in there which measures whether the mouth guard is on your tooth or not. It's called on tooth technology. When it's on tooth, it measures the impact events and then it has a Bluetooth capacity. So it can send a message to our independent doctor on the sideline and that doctor will get the alert and remove the player. When this started out, what would happen is an impact or a head acceleration event was measured, it sent the message to the cloud, was then filtered on the company's portal and sent back out to the iPad or the computer of the person looking at the information. This technology is filtered on tooth, so it's ready to go within a second or two of the event. And then, via Bluetooth, the message is sent to the match day doctor. So the match day doctor then can be aware that they need to have a look at the player and remove them.

Chris - And how do you know that that data recorded from that player is an accurate representation of the experience of that player's brain when they're succumbing to those knocks?

Eanna - We looked at, for example, putting sensors in helmets, but that's notoriously inaccurate because the helmet moves independently of the head so you get a lot of artificial movement and noise from the technology. The reason we use an instrumented mouth guard is that the player has a 3D intraoral scan performed, the mouth guard is made to that scan and it fits snugly onto their teeth. The teeth are attached to the skull, the skull surrounds the brain, that's as close as we can get to measuring brain movement and brain response. The technology then centres to the centre of the head so players' age and size have a bearing on how that's filtered, but that information is a proxy. The next step on this is some really clever engineering. We've been in discussion with Stanford University and with the NFL who have what are called finite element models, so they'll take the information about the head acceleration events, about the direction of force, about the clinical outcome, and they can then understand what's called 'brain strain.' But again, even that is hypothesis driven because there's no way of measuring what's actually happening in the brain.

Chris - Does it take into account the fact that different people are different shapes and different sizes? Because a person whose brain anatomy, as in the structure of their head and neck and so on, they might be subjecting their nervous system to a different set of shocks from the same movement than someone who's a totally different shape and size.

Eanna - So if you're a female rugby player, by virtue of the type of game you play, you will have less and lower magnitude impact events, yet the concussion rate is very similar. So we think there's a susceptibility difference between men and women, which may be related to head size, neck strength tolerance, neuromuscular control, which is basically how well your nervous system responds to movement and your ability to cope with that. So, for example, when you fall on the ground, if you have very good neuromuscular control in your neck, you hold your head steady and you don't bang your head to the ground. Whereas a mechanism that we sometimes see in the women's game that we don't see in men is that when the player falls, they subsequently bang their head on the ground. And the hypothesis there is that neck strength and neuromuscular control of the neck is a factor in that.

Chris - So is this a reflection on match fitness as well? In the sense that if you know someone is very fit, they're very strong, they've got really good muscular control, that they're going to be less susceptible. And so that's one of the metrics that perhaps you'll be arguing makes some knocks safer for some people, but once you've got this data, it reinforces your ability to make those sorts of judgements.

Eanna - I would turn it around ever so slightly, and I would say that we understand that playing age is a significant factor in injury risk. So your level of experience and your level of physical training and preparation are in some ways protective. But the other edge of that sword is the fact that as you get better and bigger and stronger, you move faster, you generate higher forces. So there's probably a tipping point, there. Lots to learn in that space, and we're just tipping the iceberg on it at the moment.