Great, thank you and good afternoon. We all know that one of the trends that we've always seen recently and in the past decade is to try to save the meniscus. And with improved techniques and improved biological understanding, that has certainly happened. Unfortunately, there's always going to be those cases where we can't fix the meniscus. And what do we do with those patients who have pain after they've had a partial meniscectomy? Today, we're going to concentrate on meniscal replacement options. And I'd like to categorize these into three categories, segmental replacements or scaffolds, biological replacements and allograft transplantation, and the synthetic replacement. So if we look at segmental replacements and scaffolds, we've heard some talks about that this morning. What are the design considerations? Well, we want to have a large amount of biocompatibility with a low immunogenic response. It has to be something that gradually will be biodegradable, which will coordinate with the host tissue regeneration. We want it to have good biomechanical properties, suitable porosity for cell ingrowth, and have good bioactivity. The advantages and disadvantages of a meniscal scaffold are that you, advantage-wise, you're preserving the meniscal tissue, you're restoring a biomechanical condition, and hopefully preventing or slowing the progression of articular cartilage degeneration. The disadvantages are there's going to be limited indications. You need to have the peripheral meniscus preserved. Implantation, the procedure itself can be challenging. And certainly, while we saw some good results today, the long-term outcomes are certainly still in question, especially in regard to the bioprotection that is provided of the articular cartilage. And certainly, in our country, reimbursement becomes a very big issue. Presently, on the market, there are two options for scaffolds. The collagen meniscal implant, which we saw a great paper about earlier, which is a product distributed by Stryker in our country. And the ActiFit, which is a polyurethane-based material, which is only allowed in Europe, it has not been allowed yet in the United States. Some of this will be a repetition of what we've heard already, but as you know, the collagen meniscal implant is a purely collagen-based material. It's arthroscopically implantable. You can adjust it to affect the defect size. It's available off the shelf, and it's very compliant with the articular surfaces. In our country, mostly it's used for the medial meniscus. We saw examples of using it for the lateral meniscus, and probably you could use a segment for it in that instance as well. It's a type one collagen. It meets the recommendation of having high porosity, and it's across the matrix, and it's completely absorbable with time as there's tissue ingrowth from the host. There's certainly been some great results, and it's nice to have one of the authors of that paper right here in our audience today. And we've been using it for a long time, and have really very excellent results demonstrating tissue regeneration. Radiological evaluation has demonstrated good ingrowth of tissue and normalization over time, and certainly some of the results have demonstrated strong chondroprotective effects. These are just some random pictures from various authors in Europe who have used this for a longer period of time. You could see it one year, it five years, and again, probably doesn't look perfect. What we'd like to see is a normal meniscus at eight years, but you need to figure that probably having something there is better than having nothing. And then again, could you advance that please? And go at even 11 years, you can see the segment of the meniscus at a relook surgery as well. This is just an example of this meniscal tear, fairly complex in nature. We resected that. This is the instrument that you can measure the device length by, the actual implant itself in place. You can see how it very nicely contours and fits within the joint. And you can see how it absorbs the blood from the periphery into the implant. The second meniscal scaffold that's utilized is the ActiFit meniscal segment replacement tissue. And this is more of a polyurethane scaffold and comes specifically designed both medially and laterally. Again, it's also a porous structure with 81% porosity. And basically what you're seeing here is how the cells will ingrow from the periphery in the vascularized zone into this porous material. Again, similar indications that we wanna see this mostly in a chronic symptomatic irreparable medial lateral meniscus or a significant meniscal loss. Again, you need to have an intact peripheral rim as well as tissue anterior and posterior to it. Ideally a stable knee which has proper alignment. As we heard earlier, good articular cartilage. So there've been multiple systematic reviews. Most of them have a concern for longer term outcomes, although we've seen good data from fairly longer outcomes. There's certainly a lack of randomized trials. There's also in many of these procedures a large number of concurrent procedures being performed. Certainly we need to worry about whether or not it's gonna really work as well as a normal meniscus. But again, having something is probably better than having nothing. Again, we have limited indications. And with these reviews, both the ActiFIT and CMI implant have had very similar results. I think the future considerations as far as scaffolds is certainly gonna be the use of various growth hormones and biological augmentation factors, improved biopolymers and bioengineering, the use of 3D bioprinting, and of course the possibility of using segmental meniscus allograft transplantation. So that brings us to our second category, that of meniscus allograft transplantation, which has certainly been an evolution of a concept. First, we need to truly understand the function of the meniscus and how it was important. There was a time, if you review literature from the 1970s and 60s, where people would randomly talk about taking the meniscus out and not worrying about it. We also needed to understand the basic science of meniscus allograft transplantation. And one of the biggest things that's developed is the tissue preservation. We have much better ways of preserving this tissue that will not alter the collagen biostructure, which leads to less problems with the meniscal tissue itself. We certainly had improvement in surgical technique. When I first started doing meniscal transplants in the early 1990s, there were no tissue guides, everything was kind of done free-handed. So certainly the techniques has evolved. And as we've had better techniques and better understanding, so has the rehabilitation. What are the relative indications, and I emphasize relative indications, for meniscus allograft transplantation? A subtotal or total meniscectomy, and we could spend time debating what that really means, certainly if you're resecting the entire peripheral portion of the meniscus, functionally you're probably creating a dysfunctional meniscus that would be a good candidate for an allograft transplantation. Pain is secondary to meniscal deficiency from meniscus overloading. Grade III or less congenital malatia or something that's correctable by cartilage restoration. Correctable ligament dyslaxia, and correctable or acceptable alignment. Some of the relative contraindications, people have rheumatoid arthritis or other metabolic degenerative diseases. Obesity certainly is a problem. Post-infectious disease, and if they've already started developing, remodeling of the femoral condyle. The International Meniscal Reconstruction Experts Forum had a consensus paper published in the American Journal of Sports Medicine, and had the recommendation for younger patients that is post-meniscectomy with pain. ACL-deficient patients with previous medial meniscectomy, and younger athletic patients after meniscectomy, but prior to the development of symptoms. Various techniques for meniscus transplantation evolved. There's a double bone plectate. There's a bone bridge technique that either uses a slot or trough, and soft tissue only as well. This is just an example of a bone bridge meniscus transplant in preparation. When I do these, I use two sutures to pull the meniscus into position, and for simplicity's sake, I always use purple on the posterior, P for P. For fixating the bone bridge, one of the things that I like to do is use a rotator cuff anchor as an interference screw. You can hold the bone in there, and it doesn't overbear it as a large interference screw would, and then you can certainly use these sutures to re-approximate the anterior aspect of the joint. This is an example of a patient nine months after the meniscus allograft transplantation with the probe holding the meniscus up, and you can see all that area of vascular ingrowth into the peripheral aspect of the meniscus. The complications of meniscus allograft transplantation certainly involve arthrofibrosis. It's not a little surgery. Meniscal detachment, which should be addressed very quickly so you can salvage the meniscus. Meniscal shrinkage is certainly decreased with the use of better preservation techniques, as has actual failure of the meniscus itself. Certainly, as we just saw in Dr. Critch's paper, there's some question about the role of extrusion of the meniscus and what role that plays in protecting the articular cartilage. Multiple studies have shown, though, from a clearly symptomatic standpoint, meniscal extrusion does not affect clinical findings. Some of the pitfalls and pearls, I think you always have to have appropriate surgical planning. You never want to compromise your exposure. I think too many times people try to think and they have to do everything through a very small incision and arthroscopically, but you don't want to compromise your result for this. This isn't a cosmetic operation. You have to have adequate fixation techniques. Ideally, there's some presence of a meniscal remnant. I think when you get into problems with extrusion is when the meniscus has been totally resected out to the synovial barrier and there's nothing left there to hold it into that hoop so the meniscus naturally will push out. You have to have an accurate positioning of the bone plugs or bone slot. The anterior horn must be fixated properly. One of the things to remember is that the anterior horn, the medial meniscus, does not attach on the top of the tibia. It attaches to the anterior aspect of the tibia. So you need to keep that in mind when you're doing this procedure. And technically, the placement of the pull-through suture becomes very important. Certainly, the question of whether or not meniscus allograft transplantation is experimental has been answered with numbers of studies, and in the interest of time, I won't go through all these in depth, but all of these studies have shown a relatively high success rate with some studies, for example, here with a 95% allograft survival rate at five years. Other studies have shown that the donor cells decrease after meniscus transplant. There's less graft shrinkage. We also can see that there's a lot of pain relief that's reported, and this was in 41 articles that reviewed. And overall, you can expect 83% at 10 years of graft survivorship and 56% at 20 years, and that was in a recent paper published by Tom Cotter. There's certainly a correlation with patient-reported outcomes with graft survivorship. Probably not as durable and mechanically efficient as a native meniscus, but again, probably better than having nothing there at all. And there's improvement in pain and function while providing some chondral protection. The real important idea is that this does act probably as a bridging procedure. In a study of comparing meniscus allograft transplantation versus physical therapy, patient-reported outcomes at two years were in favor of meniscal transplant. The question of returning to sport certainly happens at 83% of the time at one year in Christian Latterman's group studies. Other studies approximate that anywhere from 70 to 77%, usually after about nine to 12 months. The question of does it prevent osteoarthritis and what its durability, we know that the results of complete meniscectomy are well-recognized, certainly a challenge to study the chondroprotective ability of this. Again, this role is a bridging procedure to buy these patients the time, and again, Tom Carr does study. This is just a patient who's 22 years out from his medial meniscus allograft. This can be done with concomitant procedures to fix the ligaments, malalignment, or articular cartilage. Always questions about the asymptomatic post-meniscectomy knee and you can debate this forever, but remember that articular cartilage tends to break down rapidly, especially in the latter compartment, especially in a younger patient. And you can see this here in this picture. When we look at meniscus replacement, a lot of this is exactly what Dr. Jones talked about before. This is the new surface meniscus allograft replacement, which is designed to unload the medial compartment of the knee joint, actively being done in Europe. It's going to be hopefully FDA-approved here in the United States, and it kind of sits in and fills that treatment gap between the scaffolds and joint replacement through here. So you can see this paradigm of treatment gap where you kind of have nothing in between this surface through here. So it's interpositional, and I'm going to run through this really quickly, and you can see this is, it sits on the medial side. You can see the MRI study, sagittal view at 12 months and 24 months. Again, good protection of the cartilage. The procedure itself is very easily done, has to be done through a mini-arthrotomy to get the implant in there. You can see this live under fluoroscopy. Could you advance that, please? And again, a lot of these slides will be exactly what Dr. Jones talked about, so I'm not going to duplicate his reporting of that. This just talks about the study that was done in the United States. And this, his study was at two years, this was at 36 years, but all the improvements were still significant, and Kuh's study overall improvement at three years versus the non-surgical group, and pain improvement as well. And again, you can see in sport and recreation activities, daily living and quality of life. The knee cartilage was maintained as well in a better condition, and that was confirmed by MRI as well as intra-articular findings. Basically, hopefully this will be approved in the next several months, and we'll be able to utilize that to fill this treatment gap. Thank you.

meniscus replacement

partial meniscectomy

segmental replacements

biological replacements

allograft transplantation