A Bone Drill On Human Skin

This drill bit spins [music] at 37,000 RPM. So, as you can imagine, it easily cuts [music] through bone, but no matter what I do, I can't get it to damage my skin. Now, if you watch my cast saw video, you might think you already know what's going on here, but actually, the explanation is completely different. The reason a cast saw doesn't cut through skin is because it's an oscillating tool. In other words, a tool that moves backwards and forwards. So, it just drags flexible things like skin back and forth instead of cutting it. But here's the thing. The Halo is a drill bit. So, it's not an oscillating tool. It's a rotating tool. And rotating tools can cut through flexible material like this. And yet, this special drill bit can cut a groove in the nail of my thumb, but it can't penetrate my skin. How the heck is that possible? >> To figure it out, I've come to Helsinki. Well, it's actually S4. Say Helsinki. Like, everyone knows what Helsinki is. >> But this is Oh, that's important. But if I stood in the water, >> but not with those shoes. >> This is Bejan from Surgify Medical where they make this drill bit. They're not sponsoring me or paying me in any way. It's just that Bejian emailed me and I thought it looked cool. I brought my high-speed camera with me and we got to see for the first time how this thing works. But first, what's it for? Well, surgeons use all sorts of different tools to get through bone. For example, if they're cutting through a skull, they'd use a drill. It's properly called a burr, which is basically a ball with grooves cut in it. So you end up with these serrations. And when it spins, those serrations slice away layers of bone, a bit like a wood plane. And that's how you drill into the bone. But as you can see from this slow motion footage, a traditional bur can easily cut into soft tissue as well. So with traditional tools, a surgeon has to be really careful when they approach soft tissue, especially something like nervous system tissue or major arteries or things like that. Whereas this bone drill called the Halo is designed to minimize contact with soft tissue. But how is that? How is this drill bit cutting into this gelatin stuffed sausage skin, but the Halo isn't? The only way to know for sure is to get super close and film super slow. Actually, I made this little tool to test whether my high-speed camera is up to the job. So, you put in the RPMs of the thing you're filming. In this case, we wanted to film at 10,000 RPM. If we were recording at 2,000 frames per second, it would look really choppy like this. But if we record just above standard definition, we get about 6,300 uh frames per second. That's actually quite nice. I think that Kronos is up for the job. You can see a hint of what's going on here. See how the skin is wobbling under the halo? Why is that? Well, as the ring comes around, it bumps into the skin on my finger and it's like the skin is knocked out the way. The soft tissue is very flexible, right? So, why doesn't it just come straight back and and get cut? You see what I mean? >> You can imagine if the ring hits the soft tissue, it kind of goes down. It takes time for it to come back. Couple of micros secondsonds. >> Let me let me exaggerate that. So, like, okay, I got like this and it's like bang like that. Mhm. Yeah, exactly. >> It's coming down like this, right? Not that far. And then look, by the time it gets back, the the cutting edge is gone. Okay, cool. That's cool. You can just about see that at super high speed. See, the blade completely misses the skin. So, we understand how the halo doesn't cut my skin, but how does it cut through wood? Like, when the ring comes around, it would collide with the hard surface of the wood. And wouldn't that cause the drill bit to bounce up and away from the wood? Well, yes, it would. But here's the clever part. that ring can actually move. So, when it comes up against a hard surface, the ring is pushed out the way, exposing the cutting blade to the wood or the bone or whatever. There's a spring inside that holds the ring in the center position. And they've tuned the spring so it's stiff enough to push soft things out of the way, but yield to bone. Isn't that cool? I actually printed a 3D version so you can see what's going on at a larger scale. See how this hard surface pushes the ring out the way and now that cutting blade is coming into contact with the surface. So, I made a video about the cast saw. It's an oscillating tool, so it doesn't cut skin. Are there tools out there that are like an oscillating tool? >> Yeah, usually in those oscillations, u it's not effective for removing bone >> with the halo that just clicks into an existing thing that a surgeon already uses. oscillating burrs. Do they fit in like that or is it >> No, they have to have their own their own system. >> So you can >> It's an easier cell anyway, isn't it? It's just like don't use that, use this. Look, you get to use the same handle and the same pedal. >> Yeah. From Serious's point of view, it's exactly the same way of operation. >> Yeah. Yeah. But what if you wanted to do something really important like take the shell off an egg without breaking the membrane? >> Okay. Because as you know, if you use a regular bone drill on an egg, the membrane breaks every time. I mean, a well-trained neurosurgeon could probably take the shell off an egg without breaking the membrane using a traditional drill bit. But with the Halo drill bit, even an untrained neurosurgeon like me can do it. So, what stage are you at now as a business? You've gone through several design iterations. Are you selling the thing? >> Yes. So, it's a new device on the market, but we have done around 2,000 procedures. Head, neck and spine surgery is a very critical field because you have the central nervous system structures, cranial nerves, spinal nerve roots which are very critical to protect during the surgery. This is a model of a skull. So this is the bone and under that is the jura which is a flexible membrane protecting the brain. So, with the usual burr drill bit, to avoid damaging soft tissue, you have to be incredibly careful when you get close to the brain. That means slowing down. To do that, a surgeon would typically switch to an araiding tool like this. This is called a diamond bur. Basically, a ball wrapped in expensive sandpaper. The diamond bur reduces the speed of the cut, but at the cost of producing lots of heat, which can damage surrounding tissue. Not only that, but if you do overshoot, the soft tissue is really vulnerable to damage. When I tried with either of the traditional bears, the juror didn't stand a chance. But here's that attempt again with the Halo. You can see the ring repeatedly pushing that flexible membrane out the way. This is just a model, of course, and real tissue is more complicated. So, I'm going to show you some actual footage of these drill bits being used on real tissue acquired from a local butcher shop. There'll be a 5-second countdown timer on screen if you want to look away, but we've desaturated it, so it's not too gory. See, with real tissue, the very last layer of bone becomes flexible like soft tissue. And so, the final step is to lift that flap of bone out the way manually with a spatula, almost like a fish scale, which is the absolute safest way to do it. Whereas with the traditional bur, it can be harder to leave that last layer of bone intact without the moving ring. Okay, that's the last time I'll show surgery. Let's drill some wood instead. >> Oh, it's horrible, isn't it? >> Yeah. If you want Hey, by the way, do not do not uh penetrate into your hand. >> Good idea. That weird change in sound is because the traditional bur is experiencing something called chatter. And it's a weirdly horrible feeling in your hand. Chatter is what happens when the cutting blade bites too much into the material. And you can imagine that that would be undesirable in a clinical setting. This is what that looks like in slow motion. But when I was drilling with the halo, I didn't experience chatter. >> But we have designed it so that the ring has a kind of limited movement. It's just a very tiny kind of section of the the cutting edge exposed to the bone. It does the job very nicely, but not too much. And that that prevents the chatter. >> And just to come full circle back to the cast saw video, here are the two different drill bits on rubber. It's interesting like on the surface it's designed to minimize accidental contact with soft tissue but it also has an effect on the the way the surgery is carried out like it's going to be faster. It almost sounds mercenary like I'm trying to get more surgeries done or like you know or make it cheaper but actually I mean I know from people that uh you know in my family who've had surgery >> shortening the length of the surgery is really important isn't it? You don't want to be under anesthetic for too long. >> Exactly. >> I spoke um with one neurosurgeon actually who had drilled for 12 hours. >> The surgical drill is one of the most stressful uh tools for the surgeons. >> You know, surgeons try to reduce the length of operations, not just so they can help as many people as possible, but because long operations come with additional risks. If a safer drill bit could reduce cutting time and reduce operator stress, well, I'd want my surgeon to have that. By the way, this is an electric pencil sharpener in slow motion, which is somewhat reminiscent of a bone drill. And in fact, I think you can see a bit of chatter in there as well, which funnily enough led me to do a whole lot of engineering with my kids. That's because they made this electric pencil sharpener themselves. And when I showed them the slow motion footage of the chatter, they became obsessed with making a perfectly smooth pencil tip. And this is what I love about the sponsor of this video, Kiwiico. KiwiCo is a subscription box where every month your kids get an exciting STEM project in the post. Everything you need is in the box, so there's no running to the shops last minute or anything like that. Literally, batteries are included. The instructions are really clear and it's been play tested like crazy, which really shows, by the way, because one of my kids, who's got more ADHD than anyone I've ever met, is completely engrossed in it every month. I get crates that my kids can do on their own. I also get crates that are a little bit above their level, and I do those ones with them, like this pencil sharpener is 14 plus, for example. And it's just amazing to see how they've turned into little engineers over the years of us getting Kiwi Co. They've learned how to use loads of different tools. They now have an intuition for all these different mechanisms. And because they're so invested in it, it always becomes a launchpad into loads of other STEM related discussions and activities. If you're interested, the promo on this one is really good. If you go to kiwicco.com/stevemold, you'll get 50% off your first crate and then, you know, maybe film what you've made with a high-speed camera. Everyone's got a high-speed camera, right? Anyway, the link's also in the description, so check out Kiwi Co today. I hope you enjoyed this video. If you did, don't forget to hit subscribe, and the algorithm thinks you'll enjoy this video next. >> [music]

Click the link https://www.kiwico.com/stevemould and use the code STEVEMOULD to get 50% of your first month at KiwiCo. We got high speed slow mo footage of this surgical burr from Surgify Medical called The Halo is designed to minimise contact with soft tissue. It's a bit like a cast saw but works differently. My cast saw video: https://youtu.be/Bx1AiQdMQro Surgify Medical: https://www.surgifymedical.com You can buy my books here: https://stevemould.com/books You can support me on Patreon and get access to the exclusive Discord: https://www.patreon.com/stevemould Twitter: http://twitter.com/moulds Instagram: https://www.instagram.com/stevemouldscience/ Facebook: https://www.facebook.com/stevemouldscience/ TikTok: https://www.tiktok.com/stevemould Buy nerdy maths things: http://mathsgear.co.uk