I'm Patrick Canham in private practice in Delaware, and I'll be looking a little bit more in depth at knee bracing, here are my disclosures. So the main goals of this talk, again, to review the current literature for prophylactic knee bracing for injury prevention. I'd also like to get into a little bit biomechanics for ACL and PCL, and the implications that it has for developing a cruciate-specific brace. I'd also briefly review, post-operatively, how to use these braces for a treatment algorithm. So when looking at bracing, there's a lot of different types of braces. There's bracing for LA, unloader braces, patella-femoral braces. Today, I'm really restricting this talk to traditional ligament braces, or ligament injury braces. As you can see, it's a very big market. It's projected to be almost $2 billion in a few years. But, however, there's really limited data to support its routine use. Briefly, knee bracing history, you can see the first brace really developed 1967, but the one that was most popularized was the one that Joe Namath wore in Super Bowl No. 3. It was developed at the Lenox Hill Hospital and Brace Shop with the team physician, and it's actually enshrined in the Hall of Fame. And really, a lot of the literature came from football from that point on. That's where it was used the most. This study actually won, it was in AGSM, won the award in 1989, showed a small reduction in the incidence of MCL injuries. But for every study that came out showing a lot of benefits in injury reduction, there's just as many that came out and actually refuted that, and there's an increased risk of injury wearing braces. More recently, and Dr. Betty could probably attest to this, Michigan required all their linemen to wear braces on both knees. A lot of other colleges jumped on that bandwagon, but then an article in the New York Times just a year later showed, even though it was a popular practice, most of the players actually really didn't like it. It was cumbersome, it took a long time to put on, they thought they were slower. After about two weeks of summer camp, it started to really smell bad, so most of them, by the time they graduated college and made it to the NFL, they actually stopped wearing them. But it didn't stop a lot of the colleges from mandating their players to wear it. Again, most of the literature came from football. A few random studies, alpine skiing, this one from motocross was done, but really, the bulk of the literature comes from football. This is a busy slide, but it's busy on purpose, and again, for every study that came out that showed a reported benefit, there's just an equal number, or if not more, studies that showed no difference or an increased risk of injury. Really, the first systematic review that took a good look at this was in 2008, but still, only limited to seven studies. Three showed a relative risk reduction, but four showed a relative risk increase. Two years later, only on three studies, but same, it was inconclusive. Some showed it worked, some showed it didn't, and then just as recently as a month ago in the JLS Journal, they had the same results. They really couldn't recommend for or against prophylactic knee bracing because the studies are too inconclusive. Half the time it works, half the time they had an increased injury risk, not only to the knee that the brace was worn on, but even the other knee as well. So really, again, the jury's still out, I think, on bracing for injury prevention specifically. It's unclear if it prevents injury or actually causes an increased risk of injury. The proponents of knee bracing, they think it does give somewhat of a mental confidence factor, maybe some proprioception, but again, all the downsides, such as making the athlete slower, being mechanical, time-consuming, and they're very, very expensive as well when you think about outfitting a whole team. So that's bracing for injury prevention, but what happens when you actually have an injury? How do you take your athlete who has an injury as pretty gruesome as this and get them back to all the activities they were accustomed to doing before their injury, whether that's surgically done or non-surgically done, can a brace help with that? So again, either way, if you're gonna treat it with surgery or not, the main goals are the same, increase the knee joint range of motion and also provide stability. Can the brace help with that, particularly in looking at the PCL? Can it help assist in non-operative treated cases or can it prevent the PCL grafts from stretching out, which has been a notorious complication for PCL surgery historically? One of the reasons why PCL surgeries traditionally have failed is the constant posterior sag of the tibia. Gravity is constantly working to pull that tibia posteriorly and the pull of the hamstrings comes into effect as well. So again, traditionally, the PCL, either treated non-operatively or operatively, they have a tendency to stretch out and maybe lead to residual posterior instability. Well again, can a brace help with that? In non-operative setting, can it help provide stability to the ligament as it heals? And in the surgical setting, can it help protect your PCL reconstruction? The other avenue or complication that we know from persistent PCL instability is the development of patella-formal osteoarthritis in particular. Again, can a brace help maybe mitigate that risk? So the available evidence back in 2013, a good historical look at PCL bracing, there's really limited evidence at the time. There's only eight studies. And the main take-home points for all those studies, any brace that provided an anteriorly directed force on the tibia showed reduced PCL laxity at the final time point. However, another key component, a lot of them showed biomechanical testing, showed that the PCL is not a static ligament, it's a dynamic ligament. It experiences increased force as knee flexion increases, but all the braces at that time were static. The main brace used at the time was the PCL jack brace. This was first studied in PCL cases treated nonoperatively. The patients wore them for four months, and it did show a reduction from seven millimeters of posterior tibial translation to only three at two years. But again, this was a static brace. However, in the Journal of Arthroscopy, they really demonstrated, well, the PCL is not static, it's dynamic. As flexion increases almost up to 90 degrees, it's a prettier linear increase in the amount of force that the PCL sees. So again, can a brace reproduce these biomechanics? So when the bioengineers set out to make this brace, they wanted to try to make it a dynamic brace with an anteriorly directed force on the tibia. That would, again, be used to help the PCL ligament heal in nonoperative cases or offload the PCL graft that you put in from a reconstruction. And this is the design of the dynamic PCL brace. You can see that it's a little bit bulkier than the traditional brace you might be accustomed to seeing. It has brackets on the sides, and we'll go into it in a little bit more detail, but it really helps to provide an anterior pull or push, actually, on the tibia with increasing knee flexion angles. So before, again, it's kind of building on that pyramid, you have to make sure it works biomechanically before you can test it clinically. So they went out, the engineers got together, and they tested it with six healthy adult males, and they had them do three different exercises, seated flexion, squatting, and stair descent, and they pressure mapped them with surface marker motion capture, and they tried to see if the brace did what it was supposed to do. Did it provide increasing anterior translation of the tibia with increasing knee flexion? As you can see here, it successfully worked in the lab. How did it work clinically? This study published in the AJSM just a few years ago, it was Dr. Leprade's study, 100 PCL reconstruction patients followed for a minimum of three years. The pre-op posterior tibial translation was almost 11 millimeters, reduced to less than two. And there was no difference, really, in the functional outcome scores for the PCL patients, even compared to the ACL reconstruction patients. And again, if you look at the literature, that's not always typical. Again, there's a lot more posterior tibial translation seen with PCL reconstructions traditionally. Now, there's a lot of variables that go into this study. It could have been the double bundle nature of the PCL reconstruction, but one constant is all the patients postoperatively did wear that dynamic PCL brace. Again, changing gears, one of the complications of persistent PCL insufficiency is potential development of largely patella-femoral osteoarthritis. Well, again, can a brace potentially help mitigate that risk? Going back to the biomechanics lab, they took eight cadavers and put pressure sensors in the patella-femoral joint. They sectioned the PCL, and then they compared the sectioned knee to the one that they put the dynamic PCL rebound brace on. And as you can see here, as knee flexion angle increased, the stress on the knee was significantly reduced when the dynamic PCL brace was worn. So that's the PCL, but what about the ACL? So ACL injuries, way more common than PCL injuries. There's really little to no data to support brace use after ACLs, but over 70% of surgeons still prescribe them, but it's very expensive. Again, it makes up almost $65 million in the U.S. and Scandinavia alone per year. Well, the ACL's opposite of the PCL. Again, the PCL sees increasing forces with increased knee flexion. The ACL's the opposite. It sees more force at almost full extension. So if we made a brace for the PCL, can we make a dynamic brace for the ACL? And same thing, going back to the biomechanics lab, the bioengineers worked with the physician scientists and did those three same activities and measured the force that the brace applied, and as you can see on the bottom right-hand side, the brace did what it was supposed to do. It created more of a posterior applied force at almost full extension to protect the ACL. Looking at it, kind of the same as the patelformal osteoarthritis development for the PCL, one of the known risk factors of continued ACL instability is degeneration of the posterior horn of the meniscus, which is the secondary stabilizer of anterior translation. Same thing, they went back to the biomechanics lab, did a sectioning study with seven cadavers, and did those three simulated activities again and measured the strain in the posterior horn of the medial meniscus as well as the ACL, and as you can see, it reduced it pretty significantly when you look at the meniscal strain involved. The potential applications, unfortunately, I think it's still early. We don't have a lot of clinical data, still more biomechanical data for the ACL dynamic brace in particular, but some potential applications to consider are the at-risk patient for ACL reconstruction, potentially an allograft reconstruction or revision, or soft tissue grafts in patients with hyperligamentous laxity or an increased posterior tibial slope, and the patients that maybe you're on a bubble and you don't wanna do an anterior closing wedge osteotomy to correct their slope, can this serve that role? And then similarly, as the PCL dynamic brace, can this help with a patient that's not a candidate for surgery and prevent secondary injury to the medial meniscus? So again, I think a lot of research still needs to be done with the dynamic brace, particularly the dynamic ACL brace in the clinical setting, both non-operative treatment as well as operative treatment, and also how long do the patients have to wear it for, particularly in the non-operative treated PCL patients, how long do they have to wear it? Because it is a little bit cumbersome and it's a little big, so patients don't always love to wear it and they're itching to get out of it as soon as possible. And then again, I think it's interesting the other applications, can it help prevent osteoarthritis in the patient with persistent instability or the secondary medial meniscus tears? So after surgery, I think it's important to develop your own post-operative bracing algorithm. This is level 10 evidence, but I think anyone in the audience that does a lot of PCL surgeries or multiligament knee injuries, I think it's important to think about these and develop your own bracing algorithm. I think consistency with patients, but then also a lot of times you're treating physical therapists is really important to stay uniform across the board. So again, when the PCL's involved, that takes priority. The gravity always wants to exert that posterior tibial sag, so that really has to take priority in terms of bracing. Currently, a knee mobilizer for the first few days after surgery until swelling allows to get into the dynamic PCL brace as soon as possible, and I have them wear it 24-7. Gravity doesn't sleep, so unfortunately they do have to wear it while they're sleeping as well, only take it off for bathing. I routinely get stress x-rays at six months post-operatively, and if there's no increased posterior tibial translation, I allow the patients to start to take the brace off for ADLs, but I do recommend wearing the brace for the first full year of return to sports. When the PCL's not involved, it's a little bit less intense. A hinged knee brace for the first six weeks, but they can really take it off for sleep and ambulation and have much more frequent brace breaks, because again, you don't have to worry about gravity with the posterior sag of the tibia. And after that, a functional brace after six weeks, and then again, I think the date is still lacking, hopefully it'll come, but consider the ACL dynamic brace for, again, the ACL that you think is at risk. So in summary, there's really limited evidence to support the prophylactic brace used for injury prevention, although it's a very big and expensive industry. I think if anything to take away from this talk, the PCL grafts traditionally stretch out, combat that posterior tibial sag with the dynamic PCL brace, which hopefully recreates the biomechanics of the native PCL better. Consider the ACL dynamic brace for the ACL at risk, and I think it's important to develop your own brace algorithm. Thank you.

knee bracing

injury prevention

biomechanics

ACL

PCL