Lower your risk of an ACL injury by 50%- Tim Hewett PhD

In this episode of the Crackin' Backs Podcast, we welcome Dr. Timothy E. Hewett, a world-renowned orthopedic researcher and professor. With a doctorate from the University of Cincinnati in Physiology and Biophysics and a fellowship in Molecular Biology and Biomechanics, Dr. Hewett has become one of the leading authorities in the field of injury prevention and rehabilitation, especially regarding anterior cruciate ligament (ACL) injuries. His career spans decades of research and publication in peer-reviewed journals, contributing significantly to the understanding and management of sports-related injuries.

Dr. Hewett's recent work includes a fascinating study evaluating the impact of running post-anterior cruciate ligament reconstruction (ACLR) on the gastrocnemius muscle, more commonly known as the calf muscle. This study is part of his broader research into ACL injuries, focusing on innovative methods to reduce injury risks and improve rehabilitation outcomes. His expertise in biomechanics and sports medicine positions him uniquely to offer insights into the latest breakthroughs that could significantly impact sports and athletic performance.

During the podcast, Dr. Hewett will share his extensive knowledge on how athletes can lower their risk of ACL injuries by up to 50%. He will also discuss the management of the high-performance demands in today's sports landscape and how athletes can maintain their physical and mental well-being amidst these challenges. Additionally, Dr. Hewett will enlighten listeners about a "Ramp Lesion" concerning the knee, providing valuable information for athletes, trainers, and sports enthusiasts alike.

This episode promises to be an enlightening and informative session with one of the foremost experts in sports medicine and biomechanics, offering valuable insights for anyone interested in sports health and injury prevention.

We are two sports chiropractors, seeking knowledge from some of the best resources in the world of health. From our perspective, health is more than just “Crackin Backs” but a deep dive into physical, mental, and nutritional well-being philosophies.

Join us as we talk to some of the greatest minds and discover some of the most incredible gems you can use to maintain a higher level of health. Crackin Backs Podcast

Transcript

Dr. Spencer Baron: 0:00

Welcome to the cracking bags podcast where we delve into the ever changing world of sports medicine and biomechanics. Today we are supercharged to have Dr. Tim Hewett, a titan in the field of biomechanics, ACL, knee research and Sports Medicine. Dr. Hewett is the leading researcher on ACL injuries and today he discusses groundbreaking research that is turning heads with its potential to reduce ACL injury risks by a staggering 50%. He's here to spill the beans on the latest findings, including a study that sheds light on the effects of posterior chain involvement in post ACL reconstruction and the importance of your calf muscles. Get ready for an eye opening discussion on managing the high stakes of athletic performance while keeping your body and mind in top shape. Hold on, because Dr. Hewett is going to unravel the mystery of something referred to as the ramp lesion in the knee. And why if you have this condition, a repair of the meniscus is preferred over the removal of it. Buckle up listeners, this episode is going to be an absolute game changer if you work with anyone with knees. Hey, I welcome you doctor to view it. I was looking into your background both Dr. Terry and I and we were really excited and impressed by what we had found about you. I know you don't think so. But we do. mean I agree with you. Well, biomechanics in sports seems to be your forte and we would love to hear let's you know get started on maybe some research that or some findings or something that you think is significant that you're working on or have worked on that may impact sports and athletic performance. And then we got a host of other questions for you. So

Dr. Tim Hewett: 2:09

we we got into this, this little guy called the ACL or the anterior cruciate ligament over three decades ago, your ACL is this big as big as your pinky. It's actually proportional just for an FYI, your PCL, your posterior is proportionate to the size of your thumb. And they they cross. That's why they're called the cruciate ligaments and in the sagittal plane. And interestingly, in biomechanically, the center of rotation in the sagittal plane of your knee is where they cross. And that actually changes as you flex and extend the knee. We did a series of studies, we were the first to report that we thought we were the first to report in american journal sports medicine that women were about six times more likely to rupture their ACL than than men. And that, that took us through a an odyssey that's it's lasted for decades. 10s of millions of dollars in NIH funding, trying to figure out why that is in trying to try to reduce that gap. And so, basically, what it what it comes down to is women or individuals at high risk for an ACL injury, show for Neuro muscular imbalances that put them at greater risk. The good news about it is neuromotor control, neuro muscular imbalance can be altered can be modified. So what we showed in a series of studies is that you could actually reduce the risk of an ACL rupture in women or in general by 50%. For all, this is a study we actually published in 1999, for all athletes, all ACL injuries with with neuromuscular control training, you can reduce the risk of an ACL by half noncontact ACL injuries in female athletes, you can reduce by two thirds Wow. And pretty, pretty striking. And recently did, I'm getting ready to do a tour of Japan and Australia. I'm heading out on Tuesday. And starting out actually with the ACL study group which is a group of about the 100, top reputation and volume, ACL surgeons in the world. And we get together and talk about the latest advancements in reconstruction, rehabilitation and risk reduction. I don't like the word print vention Because prevention says I know something's going to happen. And I'm going to stop it from happening. Actually, what we do is reduce the relative risk of an ACL injury in a population using neuro motor control training. So what we showed in a series of studies was that you can reduce the risk of an ACL by looking at four patterns that high risk athletes display. So the first is what we call ligament dominance. So what what I mean by that is athletes who land and cut and let the ground reaction force, hit their knee joint and hit their ACL rather than using their musculature to absorb and dissipate that force. So that's rather than being muscular dominant, there ligament dominant, they rely on their ligaments and ligaments are not designed to absorb and dissipate force muscles are. So again, the good news is we can modify those patterns and drill an athlete to activate the musculature that's going to protect the the agonists of the ACL. So the second neuromuscular imbalance that athletes demonstrate is what we call quadriceps dominance. And, and women and athletes that tend to be at high risk, no matter the sex, basically, utilize their quadriceps a lot to stabilize their knee joint. And the quad is a big, big muscle, front of your thigh and it is a stabilize the knee joint. But it's actually an antagonist of the ACL, when you primarily activate your quadriceps and your knees at less than 45 degrees of flexion, as we're talking about with the ACL and PCL, if this is your tibia, and you're primarily activating your quadriceps in that mechanism, you're pulling the tibia forward, and that's straining the ACL. So what we need to for risk reduction, we need to teach the athlete to activate their posterior chain, their Hanny's, which was a primary agonist of the ACL, the glute complex, the hips to reduce that strain on the ACL.

Dr. Spencer Baron: 7:23

It took Oh, sorry, go ahead. No, I absolutely. I was just going to comment before he said that. I love how you describe the size and the perspective of the ACL and PCL. I did want you to back up just for a moment. We have both, you know, lay listeners and also doctors listening. When you said neuromuscular rehab. Early on, what are you referring to like what kind of neuroscience what I mean

Dr. Tim Hewett: 7:56

by that is training that is more than simple strength training in in one plane on a machine, for example. So what you're going to do is you're going to use exercises that add neural aspects, neural control and enhancement of strengthening in combination with enhancement of neuro neural control. So a lot of what we do is mid and high level plyometric training. And we can talk more about that but a lot of a lot of plyometric training, a lot of dynamic balance training. That's both strengthening and alternative altering neuro motor control

Dr. Spencer Baron: 8:42

profile. Love it. Alright, sorry, go ahead and continue with

Dr. Tim Hewett: 8:45

number three. Oh, the third imbalance that we see in female athletes and high risk athletes in general is, is leg dominance. So most athletes, almost all athletes are leg dominant to one extreme or the other. We have a you know, right leg dominant for which you know, is the majority of the population. However, athletes at risk have much greater asymmetries, one side versus the other, especially in things like hamstrings, hamstrings, the quadriceps peak torque ratios. So again, those athletes and very often you'll see an athlete who's really quad dominant on one side and not nearly as quad dominant on the other, that puts them at risk. That's, that's leg dominance. And then the fourth neuro motor imbalance that we see that puts athletes at risk for an anterior cruciate ligament rupture, is trumped dominance. And basically what I mean by that is when that athlete moves, cuts, lands, basically what they do is they allow a lot of translate Shouldn't have their trunk in their center of mass. And that's problematic because if you look at the by biomechanics, so trunk is here center of mass. And basically what happens if you, especially in the lateral plane, go go lateral so that your center of mass that so you have a ground reaction force from the foot on landing and the ground reaction force is directed at the center of mass which is around your umbilicus. And when you allow that ground reaction force to go lateral to the hip and knee joint, it creates what we call an external knee AB ducting moment. It's AB ducting your distal tibia, and, and pushes your knee and hip inward, which in clinical terms, it's kind of a garbage camp term, but the idea is valgus and especially dynamic valgus allowing your hip and your knee to cave in, during activities like single leg landing, which is that single leg landing and cutting which is that's how ACL injuries occur. So one of the reasons for example, after I hit Japan for the ACL study group, I'm jumping the rest of the way across the pond to Australia and visiting Melbourne and Sydney and Gold Coast Brisbane because they have a sport called AFL Ozzy Ozzy rules football, Ozzy Rules Football League. And basically what they're doing is they go up for these Becky's where they do these spectacular catches someone perturbs their trunk or their center of mass goes lateral and they land on one foot. And it's the per capita per per exposure. They have the highest rates of ACL injury in the world because of that, because not only can you have athletes with a Trump dominant pattern, the sport pushes them into this Trump dominant position. And what I mean by that another term for Trump dominance is, is lack of elite level core control. And that and that's really what we promote to reduce the risk is core control at all levels, starting simple levels on ball Swiss balls, and then moving up into dynamic Single Leg perturbation situations where they keep their core under control with their center of mass over the foot base with the knee and the hip and a stable neutral configuration. And that's how you reduce the risk of a 23. Should ligament rupture.

Dr. Spencer Baron: 12:50

That is fantastic. So let's talk ACL reconstruction of one of your studies, you shared that the gastroc becomes or the calf muscle for the late people, it becomes affected and there's a increase in muscular activity. How is it what's the dynamics there.

Dr. Tim Hewett: 13:19

So the gastroc, depending on the the flexion angle of the knee, can be an agonist or an antagonist of the ACL. So training the gastroc under control is is very important. So when you're when you're doing training, so you start out when you do plyometrics. The simple exercises are those exercises where you're keeping your hips and your knee in a neutral configuration both in the frontal and sagittal plane. So just slight, slight flexion of the hip and knee, and then you're just working your ankle. So wall bounces, you know, wall jumps. And what you're doing is teaching your neuro motor system to activate the gastroc in a way that it is going to be powered up but in an agonist role for the ACL, how that the gastroc is an important force absorber. So again, absorb and dissipate that force before it hits the knee joint and before it hits the ACL. That's that's absolutely crucial. How about I've been training my son, who's who's my training partner. He's been my training partner since he was three years old. I'm one of those really crazy dads and he is we just worked out last night and he has a date tonight. But I told him we'll get in a short one before the date it'll it'll prime me. Literally, I've been training him since three. You should see his gastroc Yeah. Things are beauty. I can tell you that Diamond diamonds, diamonds in the rough, rough,

Dr. Spencer Baron: 15:05

right? Oh, that's great. So then how much of an influence does PES plane is or even, you know, a collapsing ARCH effect? I mean, you obviously look at the whole picture. Can you include

Dr. Tim Hewett: 15:23

theories pes planus, or collapsing arch contributes when we did the when we did the prospective biomechanical study. So, so these studies, again, large NIH funded studies, for example, one one NIH study we did in the 2000s. We looked at the entire county school system for Boone County, Kentucky. Wow. So that's where the CVG the sense and that's where I'm flying out on Tuesday. That's that's the Cincinnati airports just across the river in Northern Kentucky and Boone County, Kentucky Well, I, I lived there at the time in the 2000s. Well, my farm was out there. And so I knew the athletic trainer, Bob man Jean, who was in charge of through St. Elizabeth's system, he was in charge of all the athletic training for the entire county. And, you know, it's interesting, Title Nine is in the news these days, Title Nine is what was enacted in 1973. That said, we have to give equal opportunity time money to female sports that we give to male sports. And Boone County actually had a title nine lawsuit against them at time. And a mother who was her daughter was a cheerleader was was she was on the school board. And she was suing the county saying my daughter's not getting as a cheerleader, she's not getting equal and opposite, you know, equal opportunity and, and money that football players are getting. Yeah. And so we went out to the county and said we want to do a study looking at risk reduction of ACL injuries, especially in high risk athletes, which are most especially female athletes. And so they saw this as an opportunity for so for more than a decade. We started out and we we just did the prospective studies looking at for those picking out those athletes who are at relatively high risk. And then what we did over time is follow them on to see who so we looked at their biomechanics, we would bring entire teams again, every girl who played soccer, basketball or volleyball in the entire county by team would come into our lab at Cincinnati Children's Hospital, we test full body biomechanics, landing, cutting, running, jumping, test their muscle strength, test several balance several different biomechanical neuromuscular parameters, then we'd let them go out and play and we track them season over season over season. And that that led to the most cited paper in agsm. All time in 2005. So and, and so actually, these studies have resulted in the last so AJs American Journal of Sports Medicine, aos DSM has been in existence for 50 years. That's it, you know, it's interesting sports medicine has only been around for five decades. And in those five decades, this what I'm talking to you about now, reducing the risk of ACL injuries, especially in female athletes resulted in five of the top cited papers of the year and those fifth wives 10% of them is. So this has been not only important, it's been impact. Yeah, it's really impacted clinical practice. And so, what we showed in 2005 was we can pick out we can show which athletes in a population are relatively high risk. And then we did a series of studies where we showed if you target those athletes at high risk with neuro motor control training that directly addresses those four neuro muscular imbalances. You can reduce the risk and this is follow up studies. So I did these studies with Kate Webster, who's based out in Melbourne, Australia at ortho sport Victoria and Latrobe University again, highest risk of ACL injuries in the world. She works with a surgeon who's named Julian feller who's kind of oh, she she would be the equivalent of Neil Ella trage out in LA the you know, the he's, he's the team doc or the ACL doc to the to the AFL stars. And so they see something like I could ask him he's gonna Be with us in the Seco Japan next week in excess of 600 ACL reconstructions a year. And so basically, we did a series of follow up studies. So in 1999, which was the most cited paper and AC, in agsm of the year, we showed you could reduce the risk in a population, it was about 1300 athletes, we could reduce the risk by half in all of all ACLs. And by two thirds or 67%, in non contact ACL injuries in female athletes playing soccer, basketball, and, and volleyball. And so what Kate and I did, actually, 20 years later, we published this in 2018. We did a meta analysis of all the meta analyses in the literature. At the time, there were about a dozen of them. I call it our inception analysis. So we did a meta analysis of meta analyses 20 years later. And what did we find? When he looked at all the data together, which is 10s of 1000s of athletes, what you saw was, we could reduce the risk by 50% in all athletes, including male athletes, and we could reduce the risk of non contact ACL injuries by two thirds or 67% 20 years later, that's called consilience. That's when the data comes together and shows you the exact same result. And that's when you know you're right, that's when you know you've hit the nail on. So we can do this we can reduce the risk of ACL injuries in all athletes all comers by 50% in non contact, and non contact is important, right? Because 70 to 80% of anterior cruciate ligament injuries are via a non contact mechanism, meaning someone didn't take their knee out, you know, the tackle didn't fall on the lineman, you know, the guards knee, basically, it's just you cutting landing, for example, the most common mechanism in soccer, or properly termed football, is a defender reacting to an offensive player making a cut, making a move with the ball, them unanticipated because the defender doesn't know where their trunk or their body is going. So they're backing and then moving their trunk in one direction or the other in an unanticipated fashion. And they get that well, it's it's basically a neuro motor motor control glitch, because they're moving their trunk in a way relative to their foot where the ground reaction forces coming from, and their hip and the knee and they move their trunk in a way that takes their hip and knee out of a neutral configuration, move their trunk laterally, cause that dynamic valgus. And it happens very rapidly, and they rupture their ACL. So the good news and all that is, that's a non contact ACL injury, someone didn't take your knee down. But that also means that it's modifiable, because it's non contact. So it's due to neuro motor control patterns in your own body. Now, if we can train you to not be ligament dominant, not be quad dominant, not be leg dominant, and not be chunk dominant in chaotic environments. Again, basically what we showed in the lab, so the first series of studies we did, I'm, like I said, I'm an old powerlifter have done plyometrics most of my life, basically applied what we knew from people like Don Chu and burn Gambetta and a lot of other people I learned from including physios Cairo's ATCs, you name it, I just a sponge for training. And so, basically what we did, and this was a first series of studies in 1996, which we showed in the lab, we could alter those biomechanical profiles. So in high risk female athletes, we could we significantly reduced ligament dominance. So the way you see ligament dominance is we do at box drop vertical test, and basically look for that dynamic collapse. And basically, what we showed was after eight weeks of intensive training with resistance training, plyometrics a lot of dynamic balance training. We could reduce that dynamic inward collapse that loads the ligament and you see in the frontal plane, the big movers of the body, the quads, the hammies. The even the glutes are designed primarily to absorb and dissipate force through flexion extension that those are the primary movers. When you allow a lot of frontal plane movements, those big movers are not well designed to absorb and dissipate force in the frontal plane. So if we can show an athlete to utilize those big absorbers, the big muscle groups to absorb and dissipate force in flexion extension, and not allow a lot of dynamic valgus, we can reduce the risk of ligament dominance, allowing that ground reaction force to go to the ligament rather than being dissipated by the musculature. But we can also show them, we can turn up the posterior chain, and many athletes don't activate their when they're landing when they're cutting, when they're when they're perturbed on and land on a single leg. They're not activating their glutes and hammies in a way that's going to that's going to help that ACL that's gonna take strain off of that ACL. But you can with drilling, you can teach them and incorporate in their neuro motor pattern, those posterior chain dominant patterns in Sudan, we showed that you could significantly decrease that quad dominance, you can do the same side to side. So you start out with double leg Plyometrics, then you move to dynamic single leg. And then once they it's interesting, because single leg training actually enhances symmetry. It's counterintuitive, but it's exactly what it does. If you do a lot of dynamic Plyometrics, and Single Leg dynamic balancing on a single leg, and then you come back together into double leg tasks, you're going to be more symmetric side to side, especially in a relatively quad hamstring dominant pattern. So if you look, for example, in that 96 paper, which was again, the top cited paper of the year, and agsm, we showed we increase those relative by a lot, by about a third. In these young girls that were that were especially quad dominant, and leg dominant, we made them more symmetric and enhanced on both sides, their relative hamstring to quadriceps peak torque. And then finally, with this, especially plyometric training, but also dynamic balance training, we show that we can show them how to control their center of mass. So if people always say, you know, people always want to want one pill, what's the one pill? Now as a human, I don't want to train for now. Our training is kind of intensive, and we have been criticized for that. This is, you know, this guy is a power lifting plyometric meathead. If we don't want to train three days a week for 90 minutes, which is what we do for a minimum of two months, preferably three. And they say, we just want the one pill, what do you do? What's the one pill that's going to prevent, and I always tell them, we're not preventing anything we're reducing there as well, what's going to prevent my girl from having an ACL injury. And I tell him this, if you're so lazy, that you're not going to do the work that you need to do. Because if you do the work, not only are you going to reduce the risk of your athlete, your daughter or your your kids ACL injury, you're going to make them a better athlete, because they're going to have better control of their center of mass. And they're going to be more powerful. For example, in that 96 paper, we showed that their vertical jump went up 10% plus. So if you're too lazy to do that, you only want one thing I teach him to do single leg Plyometrics, dynamic, bounding, landing balance with their center of mass over their foot base with their hip and their knee in a stable neutral configuration, especially in the frontal plane, if you can, and the cool thing about this is when risk goes up is adolescents boys and girls prior to adolescence have similar relative risk and then boom. And I we can go in a whole series of an another series of studies that was funded out of the NIH about when this risk goes up, and why it goes up and again And that's that's a whole, a whole nother book that that we wrote. So the point is, if you can teach them to do this, and you drill it and drill it and drill it, you're going to be able to not only make them safer, you're going to be able to make them a better athlete. So that's the way you sell this to know the parents are very interested in safety. So very often we get our studies and our programs out at the schools funded by the boosters because the parents are interested in save athletes. Coaches should be interested in save athletes to the NFL, just look at the NFL, basically, the NFL lose who's in the playoffs, the one that the ones that have won the war of attrition, that's that's basically what it is. So safer, you keep your athletes, the more of your athletes are going to stay out on the field by mid and end season. But again, many people, especially the athletes themselves, they don't. Risk reduction is not primarily in their brains. What they're about is performance. And I can show you, and I can see this, I train older people, you name it, I train the entire gamut because I it's not what I do. I'm a research scientist, but But I I love to hit the gym. And I tell you people all the time. That simple balance exercises, the worst you are especially like a young girl after the pubertal growth spurt, the adolescent growth spurt is out of control. So basically, what she is, is she's raised her center mass off the ground, she's up on stilts now. And she's got more of that mass to control and it's redistributed in ways that she's not used to. And that's a big reason. So that that when when girls hit the peak height velocity, so for most girls that's age, 1112 years old, after they've had that big growth spurt. They're out of control. For example, a lot of soccer coaches, you'll talk to say, Man, this girl went from the best player I had to very low level after that adolescent growth spurt, because again, so So let's talk about it. I like I like fast cars. I don't like anything else fast. But I do like my fast cars. Now I you know, I stay away from other fast stuff. But the fast cars if you look at boys and girls, so they start out at the similar level. So let's say let's talk about machines and motors. So both boys and girls start out with let's say a Prius with a Prius engine, and the end of motor is matched to the machine the motor or the engine is matched to the chassis. Then what happens is in girls is happens 18 months to two years before boys you know girls are always way ahead of us on everything. You name it, maturity wise. So girls hit this Grossberg and they get they go from a Prius to let's say Chevy Malibu with somewhere between a Prius and Chevy Malibu engine. Okay. Now what happens with boys so a year and a half later, US immature abuse it this Grossberg. And boom, we go from a Prius to a Cadillac slice chassis right now, we don't get a Cadillac motor, we get somewhere between a Porsche and a Tesla motor. So we're like this. So how do I know this? Well, it's relatively simple. Anything vertical jump, we love her. I love jumping as you as you might have gotten. So vertical jumps are the best single measure of single holes, body power, right. And it's extremely it's one of the most reliable reproducible measures you can get an athletics you jump the same height again and again and again. So we've done these studies in the Boone County cohort and multiple other cohorts. So we've done this all down at Texas Tech University with a with a friend of mine, an orthopedic surgeon, we believe it or not, we were doing this in gyms in in Texas Tech, which is in Lubbock, Texas, in June. Woon during their physicals. It was 115 degrees in the gym with no air conditioning. Believe it or not, we tested over 600 kids in this gym. And basically, what you show is this is the data is very reproducible as sweaty as you get it the data, you still show it the same way. So we did that study was a cross sectional study, we looked at boys versus girls. But we also have done that study longitudinally, where we took the Boone County cohort and kept measuring the kids year after year after year, however you do it. As girls mature, they get bigger they their body mass goes up their levers, their tibia and femur the longest levers in the body, which experience some of the highest torques at the knee. They, as they get bigger, their vertical jump, their body power stays the same. So they're bigger, they're more massive, they have the same amount of relative to body mass and body height. So basically, they're the same. So how do I know that because their vertical jump doesn't go up, their body power doesn't go up. Now in boys, what you see is, even though they have getting greater relative body mass, they're getting that Cadillac, they can displace that center of mass, a greater distance off the ground. So they're getting significantly more power relative to their body size after the adolescent growth spurt, which we assume is mainly due to testosterone Berg. Yeah, so so. So basically, girls stay the same. So they're going from a Chevy Prius to a Malibu and their motor is somewhere in between the two, the best they do is a Malibu. Now, that's the tough part. However, as we all know, you can enhance the motor, you can enhance the power in any athlete, I can enhance their give me six, give me six to eight weeks, and especially those high risk girls post Island. Here's the great part about that. So I trained boys for years and years, mainly, mainly Olympic lifters, power lifters and wrestlers mainly worked with. So if you get a boy, and he's in the middle of that adolescent growth spurt, say, and we're all aware of it from, say, freshman year to senior year, in high school, he's got this massive burst already, and you take them for the summer. So you get usually between, you know, spring and winter sports or spring and fall sports, you have about two months, you should have three but you don't because, you know, there's so many other issues and, and things that they have to do if you basically get a bad eight weeks, in eight weeks. If you're comparing to a control population, boys, you can get oh, you're lucky if you get like a three to 6% boost with training, any kind of training, resistance training, plyometric training, jump training? Well, whatever you do, you're lucky in the background of their getting this big motor spurt, you're lucky if you get just a portion of that. However, in girls, because they're starting at a relatively low baseline, you can get huge increases in power output in neuro motor control. I mean, we're not talking 5% or talking 10 to 50%. So it's really rewarding. So when I started working with these young adolescent girls, what you realize, man, this is really rewarding, because you can really alter their neuro motor profile, you can really enhance power output. So you can increase that, that motor output so that you no longer have this machine motor mismatch, or this chassis engine mismatch, and again, completely rewarding. And along with that, when you do that, you alter that whole profile, so you're decreasing that ligament dominance, you're decreasing quad dominance, you're decreasing leg dominance, you're decreasing chunk dominance, all while you're getting a better athlete. really rewarding. Really fun worked. That's why I've been waiting for so that's

Dr. Terry Weyman: 39:51

awesome. Yeah, going back a little bit. You talked about dealing with, you know, the parents and dealing with the coaches. You said, Coach, I wish coaches really got to know this How do you face the pressures of this return to play when, when you got these kids who are in high school trying to get back? And and we all know is nine months to a year. But yeah, these coaches they're pressuring how do you how do you? How do you handle that high demand for performance versus injury prevention and trying to get them to prevent it? But if that happens, get back in how do you? How do you handle that? So this,

Dr. Tim Hewett: 40:24

this is a huge challenge. So what we did with the Boone County cohort and multiple other cohorts is we kept following the kids, as I told you over time, and what we what kind of blew our minds and we were the first to report this as well. Basically, what happens is, if a kid is going back to the same level of sport after rupturing their ACL, and either having it reconstructed or not, their risk of a second ACL injury goes from well, in boys, the risk of an ACL injury in high school sports is about one to 3%. In girls, it's significantly higher, it's it's in the range of say, three to 6%. There there, their risk of a second ACL tear, either on the reconstructed side, or the uninjured side, is 20 to 40%. When we first reported that back in 2010, that blew people's minds that and that that study actually won the most cited paper the year in 2010. So we showed their risk, if they were going back at one year, was about 24%. And their risk at two years of a second ACL tear was about 30%. It was 29.5%, about 30%. Now people said you're crazy because surgeons were reporting risk of second Tears was like, Oh, 2% to 5%. That? Absolutely not. It's because they weren't following their their patients with high fidelity like we do. Basically, when, when Kate Webster and Julian feller down in Melbourne, when they looked at their data, they came up with the exact same number that we did, again, consilience of data points, it was 29 30% is what they reported and the group in, in Sydney, again, tons of ACLs. I mean, so we were doing in relatively small cohorts, they're doing a huge 1000s of athletes, they showed the exact same number again, about 30%. And like male athletes who are doing lots of spare keys and going way up high in the air and getting perturbed their risk, if when they're going back to Ozzy rules, football is 40%. So we're talking 20 to 40%. So that's an enormous, that's an unacceptably high risk. Now, we have to think about prior injury is always the best predictor of another injury. That's always when when you look at anything prior injuries, the best predictor. So what you have somebody who's had an ACL injury, and reconstruction is your highest risk athlete. So we're in this is our passion. Now, this is what we're trying to figure out. And we're looking at this in many ways, through rehab techniques, through surgical techniques, we're following up to see how in our with our risk reduction techniques that we just talked about. So on an average athlete, we know we can reduce the risk by by between half and two thirds. Our working hypothesis is this, because these are the highest risk athletes and they've already had an injury, we can reduce that risk with neuro motor targeted, very highly targeted neuro motor training, we can reduce that risk by half of that, which means half of two thirds is a third and a half of 50% is a quarter. So we're our hypothesis is we can reduce that risk between, say 50 and 25%. Which is, which is great, because that means we can reduce that risk that's now 20 to 40%, somewhere to 10 to 20%. We because again, these athletes are at super high risk. And there's basically two populations you look at. And this makes it very problematic to be able to do the sort of doing those risk prediction studies and trying to target our training to that risk profile. Here's the difficulty with it. You have two populations. So if you look at the psychological aspects of this, so the same group in Melbourne, Australia, Kate Webster and Julian feller came up with a psychological profile called the ACL RSI I highly recommend it, it's free, you can get it. It used to be 12 Question And so it's a pro, it's a patient reported outcome. And they've actually got a validated short form. That's only six questions when we ask it of every athlete longitudinally, and I suggest you use it the best way to use it as overtime to see whether they're getting better, whether they're getting worse, whether they're staying the same. And what you see is we track these kids from the time they get out of their surgery, till they return to sport and beyond. And basically, what you see in that is the same thing. You see what interestingly, the psych data is very similar to the biomechanic data, you see two populations, and you're on an inverted U shaped curve. So you have your sweet spot, which is the top of the inverted U up here. And then you've got two populations that are at risk. The one over here, which is the one very often it's a she and she says, Man, I'm really scared to go back to my sport on the on the psychological I'm really anxious about getting back to sport. Girls girls report more than than boys, you know how you know what a teenage boys get, you're lucky if you get them to say, but But anyway, what you what you see is that the girls report more, they're more anxious, they have more fear of returning. But also if you look at their biomechanics, they show that they tend to be more leg dominant, quad dominant, ligament dominant and trunk dominant, you can pick them out, and they're at a high risk. So they're the ones they're at, like, and we showed this at Mayo Clinic, with a team of people led by Melissa Allen, we showed these young girls that they're going back to the same level of soccer, their risk of a second terrorist 35%. I mean, it was actually 34% But a third their risk. Now, on the other end of the spectrum, the other bottom of the you, you have a young usually male 1819 years old, super confident. No fear, no anxiety. Boom, I'm ready to go back. Let me go doc, let me go. I'm three months out. Let me go I'm ready to go. I need to Yeah, I tore it in football and I need to start basketball camp. Well, no anxiety, no fear, Koto confidence, and you look at their biomechanics, and boom, they they pass through every return to sport test we got, they look great. Both of them are at high risk, because and they're both going to have a risk of tearing their ACL between 20 and 40%. Now less, she's probably about a third risk, and he's probably about a quarter risk, but higher high, high risk. So how do you pick out that patient? That you say, whoa, whoa, whoa, whoa, whoa, whoa, you need to wait. And that's what we're trying to figure out. That's what so what we do now is we're using every technology we can get a hold of. So we're using full 3d Virtual Reality motion analysis, mainly working with a with a company out of Cleveland called tracer, which is a great tool. And then we're using onboard IMU. So inertial measurement unit, so wearables, we're using those on the athletes both in the lab in the clinic out on the field. And then we're also doing force plate analysis. So the the, the company with wearables we're working with is Dorsa V. They're based also out of Melbourne, Australia, and another company based out of Menlo Park, California, Sparta science, whereas we're using force plate and force played analysis. And we're just trying to, we're just looking at every biomechanical psychological parameter that we can to see if we can figure out who those two populations on both ends of that inverted U are, who are at high risk, not to say don't play or don't go back, but to target their training, both neuromotor and psychological learning and training to reduce their relative risk. Again, do we think we're going to wipe out that risk by 50 to 67%? No, probably close to between a third and a quarter. But that's in that high risk population. If we can cut out half of those re injuries. That second injury. The first injury is devastating, right? I mean, you're out, you're out of your sport, you're probably not going to be back somewhere six months to a year these days. It's closer to a year and most Doc's are actually pushing, you know, minimum nine to 12 months, time is not a good predictor time doesn't really predict neuromotor control or psychological readiness, it just doesn't. So what we need to do is figure out who those kids are looking at their profile, and then target their neuromotor imbalances or their psychological their fears, their their anxieties, their confidence level, so that we can normalize that and decrease their relative risk, hopefully, by around half, we're not going to save them all. Because I can tell you, when that second injury occurs, you think that first injury was devastating? Well, if it's the graph itself, not only is the athlete and the parent and the coach devastated the surgeons devastated, you know, whereas on the contralateral side, the surgeon might not be as devastated because it's not his beautiful graph that he put all this work into. But it is really devastating to the athlete to the coach to the parent. And that, for example, at Children's Hospital, I had six people in my lab working on all these studies that I was talking about, who had two ACL reconstructions, most of them, some of them were, were unilateral a second tear of you know, a graft three rupture, but the majority were bilateral ACL reconstructions, and that gets into your head, that that's not only just a physical problem, that's not only just devastating, but mentally, you think, oh, man, can I go back out onto the field, and I go back onto the court, but also, I don't want this to happen to myself, but I want to work and I want to help try to figure out how we can reduce the risk of this happening in anybody else, because it's so devastating. So che Ralph, who played was the star point guard at UConn, she had at the time, at the time I was aware of she had five ACL injuries and reconstructions. And I was at an aos, American Academy of Orthopedic Surgeons meeting. I think it was out in Vail. It was a ski meeting in the wintertime. And I was showing our data and I showed a video of Shay Ralph and I said she's had five ACL injuries and reconstructions. And a surgeon in the back stood up and said Hewett, you're wrong. And I, I told him that's impossible. I'm never wrong. Well, you're wrong on this point, because I just reconstructed che Ralph six, six, ACL reconstruction, Utah, I mean, and you're talking about a very physically very psychologically tough, resilient individual. Imagine now we don't want that happening to anybody else. I mean, that's, it's just absolutely crazy. So that's the passion now as you can see that that is what I'm really passionate about. Trying to and and we're doing the studies, we've got multiple randomized control trials going on. We're we're, we're collaborating with people all over the world. My colleague who's a German surgeon who is actually working out of the Netherlands, Tom pot, he's with ESCO, which is the European equivalent of aos, ASM, so aos is m is American orthopedic society for sports medicine. The ask is, well, it's in Swiss, but it's the European Society for knee surgery and arthroscopy. So Tom pot is doing a lot of great work. We're working with a group of surgeons in Germany now, where we're reproducing those early studies we did in Boone County and all the all the Bundesliga under leagues that are going to going in looking at the timing, and then looking at what we can try to do to reduce the risk of primary, but also secondary, tertiary and beyond ACL injuries, and, and this is I'm absolutely passionate about it, because I can tell you, this is just devastating when these kids go on to a second and third rupture. I

Dr. Spencer Baron: 54:35

have two questions for you. One is there was a study last year that I was fascinated by that. Athletic Trainers and physical therapists did on doing MRI of the brain identifying the the way remapping had occurred within ACL injury and post surgical you know, repair. And they found that they had to address the remapping, which is obviously, what you do with the neuromuscular stuff. Are you aware of how that you were obviously aware of

Dr. Tim Hewett: 55:17

that? So it's fMRI data. And so the the problem we have with those studies, even if they're done prospectively, is you don't know what that neuroplasticity changes from you don't know, what is it from the injury? Is it from the injury plus the reconstruction? Is it the injury plus the RE construction plus the rehab? Is it injury plus reconstruction plus rehab plus time? Now my bias is neuro motor control, that's going to reduce the risk of an ACL has to be very fast, right? Because an ACL rupture occurs somewhere between the first 30 to 50 milliseconds of ground contact. Now neuromotor loops at the spinal level, your reaction is somewhere in the 100 250 millisecond timing range. Whereas even the lower brains, spring brainstem systems, their reaction time is in the 200 to 300 millisecond range. So the the brain reactivity can't be primary, it has to be secondary. And I think the plasticity that occurs is not in response to the injury itself. It's in response to the changes that occur with that injury. So So again, this little guy is not just a very hyper elastic, tough piece of tissue. So to pull an ACL apart, takes in the range. So we we've done these studies, many times, this goes back to the 80s. Pull an ACL apart like that. What does that take? Well, it takes between 18 120 200 newtons of force. So we did the studies in Cincinnati, and we came up with 1800 Newtons, which is in the neighborhood of 400 pounds. So the the ACLS really strong. And it's, it's, it's very elastic tissue. So they paid tore Zilean, the group at Hospital for Special Surgery in New York, redid the studies, and they came up with 2200 Newtons. So in New York City, even cadavers are tougher than everywhere else in the world, right? So but it takes four to 500 pounds of force. Now, so. So the ACL is is tough, and it's hyperelastic. But it's also a neural control center. Now, what do I mean by that? Well, it's full of McCanna receptors, it has all five types of neural receptors in it. And when it's ruptured, boom, it blows apart like mob ends, and you've lost that neural connection. Now, what does that why is the ACL full of every kind of, it's somewhere been estimated in the range of one to 3% neural tissue. So that nervous tissue in the ACL and the ligament itself? Well, as we went back to, it's the center of rotation of the knee joint. So it's narrowly innovated to sense in three dimensional space, where the center of rotation of the knee joint is so that the body knows how much their knee is flexed, extended, a B, ad ducted, how much it's rotated in all three planes. But it also has spinal level neuro feedback loops, a fair and efferent feedback loops. So for example, if I were to D Sarah braid, my worst graduate student, let's this this is actually been done in cats. I have never done that, although you'd like to but if you were to stare bright them, so no, no brain connectivity at all, basically, and you you tug on the ACL, you pull it forward, or you pull the tibia forward, and you strain the ACL. What happens is, your hamstrings can tracks a why is that? It's because you have an afferent efferent feedback loop from the ACL, that at the spinal level, you have a A response a positive excitatory response through the afferent. That afferent activates the spinal level neuron that then activates the efferent to activate the hamstring. Now what happens when you got mob ends? And you've blown that ACL apart? Oh, here's my working theory. It's basically you will go back to a car analogy again, because again, talking about fast cars, you've blown a fuse, as we all have one time or another blown a fuse. So what do I mean by that? Well, you've got this a Ferrant. And once that's once that's blown, and those, those neurons are no longer connected to the upper level of spinal cord. Basically, what it says is, it sends a signal it's on. So it has sends a positive excitatory signal to the to the inner, not neurons of the spinal cord, and they turn on an inhibitory neuron. And the inhibitory neuron, then sends a signal to the afferent turn off, because we've got an on signal. Now you see the quad shrink up, you know why? Because that just sent in. So you, you've got an open circuit loop. Now what you guys didn't work conditions are doing. This is theoretical, but it's my theory is you're developing parallel neural loops through the skin through That's why That's why a brace is helpful, through the musculature through the fascia, and developing new parallel neural connections because graft doesn't do that this hot dog of tissue they replace it with that comes from worst case scenario, hamstrings, don't use those because you really need those are your primary agonist, but alternatively, from your patellar tendon or from your quadriceps tendon, they're not narrowly innovated it. innervated and so that's, that's a problem. So do they ever come back? There's a little bit of data and dog literature that you might get some neuro in growth into that graph. There was a study of end of one study out of Norway, where you know, at this time a year Norwegian guy had his ACL reconstructed, he was about 18 months out, he couldn't take a long Norwegian winter, and offer himself the Act actually sent his knee over to Vermont, where they're experts and NERT, neural innervation of the ACL, and there was no neuro innervation at 18 months. So you're you're developing parallel circuits to to be able to regain that neuro motor control what I think is that high level neuroplasticity is the reaction to that those lower level afferent efferent restructurings, that's what that's what I think that is. So I don't think the brain is not fast enough for for Neuro motor control. So I think that neuroplasticity they're seeing is a reaction to the afferent efferent restructuring that that neuroplasticity that's going on it spinal level. That's my working theory,

Dr. Spencer Baron: 1:03:38

I like that you shed some new light on a perspective that it's been long been a curiosity, we got to close. But I, gosh, I am dying to add. Okay, I challenge you to answer the quickest way possible. I'm trying to find out what do you refer to as a ramp lesion? In one of the studies I saw you come, I don't know what is a ramp lesion?

Dr. Tim Hewett: 1:04:04

Well, that's a little complex, but basically it's a it's a, it's a posterior meniscal tear lesion that, that basically the meniscus gets inverted. Okay. So and that is you do have neural components of that too, because there is nerve structure running through that posterior meniscus. So, the most important part about that is it should be repaired. Don't just section out the meniscus. That's a bad idea. Good because the neuro components of that meniscus are and not only a neural, but just like the ACL, it has neuro innervation but it also has mechanical, it you know, it is the primary shock absorber of the knee between the between the tibia and femur that no everything

Dr. Spencer Baron: 1:04:58

you have shared with this has been Have a bit of advice and some enlightenment for some age old questions and

Dr. Tim Hewett: 1:05:09

well, I love what I do, I can tell you I've never worked. I've never worked a day in my life. I absolutely love what I do. And anyway, I can try to help people and, and get on with guys like you couldn't get the word out on a morning.

Dr. Spencer Baron: 1:05:24

That's great. I really appreciate it. And we just, all I keep thinking is we're gonna have this guy lecture MagForce it's been fantastic. You make everything so simple to understand to and that's really, really appreciate.

Dr. Tim Hewett: 1:05:38

Thank you so much. I appreciate that.

Dr. Terry Weyman: 1:05:41

We got to thank you for your time. You know what I'm gonna, I'm gonna ask you have to answer this in one sentence, but I'm gonna have a fun little thing. What I'm gonna do or would you rather question because I'm doing this as a promise to a previous guest? Would you rather never sweat during a workout? Or never feel sore after a workout?

Dr. Tim Hewett: 1:06:05

Never. Which one would I rather would you

Dr. Terry Weyman: 1:06:08

rather never sweat during the workout or never feel sore after workout?

Dr. Tim Hewett: 1:06:15

I love to sweat. I absolutely love to sweat so it would have to be I actually love this sort of feeling but I'd rather that's actually my goal. If I don't sweat in a workout I feel like

Dr. Terry Weyman: 1:06:33

as the way we're gonna finish this thank you for your time doc and we wish you the best in Japan and Australia and yeah, like keep wearing that hat cuz you you look so fly man. I'm just telling you

Dr. Tim Hewett: 1:06:48

hey, I can't I can't sing like Frank, but I guarantee you I'll be out there trying my best and you

Dr. Terry Weyman: 1:06:55

got to Blue wise and karaoke. You got to blue eyes and go with it, man. You have a fantastic day, man. Thanks so much. Take care guys.

Dr. Spencer Baron: 1:07:13

Thank you for listening to today's episode of The cracking backs podcast. We hope you enjoyed it. Make sure you follow us on Instagram at cracking backs podcast. catch new episodes every Monday. See you next time.