Thank you, David. Dear ladies and gentlemen, it's a wonderful meeting, it's a fantastic place, and it's my pleasure now to talk about cartilage treatment, the European perspective, but of course it will be biased a little bit by the German perspective. I've no disclosures regarding this talk, and you all know there's a variety of different surgical techniques for cartilage treatment. The different methods of the bone marrow stimulation, which can be augmented by matrixes, the autologous cartilage implantation, a new emerging technique, the one-step cartilage transplantation, the mince cartilage, or the osteochondral autograft transfer, either autografts, which are pretty famous here in North America. So as you all know, the most common thing is the microfracturing, because it's simple, it's cheap, it's widely available, it can be easily performed, and the principles to opening of the subchondral bone and the recruitment of the precursor cells. And as you all know, it's of uttermost importance to stick to meticulous surgical technique, to do a good defect preparation, create sharp margins of the cartilage, which is sometimes difficult, so you need special instruments that are very sharp, that you really can cut the cartilage. Then you have to remove the calcified cartilage, and really make a good defect preparation, especially in these delaminating defects, which are quite big. And then there are the different techniques to do the actual perforation of the subchondral bone. And it's the microfracturing, the predetailing, drilling, the nanofracturing, using smaller one, the abrasion arthroplasty, there's few clinical literature out there really showing which of these methods is the best. And on the right, you see a very nice picture of a big cartilage defect that was treated by pre-D drilling with almost perfect regeneration. But you have to think about the differences. While the microfracturing all breaks up the subchondral bone a little bit, the K-wire leads to compaction of the bone, and the drill actually leads to removement of the bone. But again, in clinical studies, we have no clue what's better, a little bit different in animal studies. And you all know that the outcome is good, basically for small defects. Kai Meithofer did a great meta-analysis, and showed us all the factors for good microfracturing. Young age, acute lesions, small lesions, smaller than four square centimeters, and in Germany we are much lower than four square centimeters. But you can burn some bridges. If you do microfracturing into big defects, like shown here, a huge trochlear defect with intralesional osteophytes, then the outcome of subsequent revision with ACI will be worse. So don't burn bridges, stick to the indications. But how can we improve the microfracturing? We can use either biomaterials, the hyaluronidase, or the collagen membrane from Geistlich, it's pretty famous. We can also use cells from bone marrow, which are pretty easy to access using special instruments. You can make really small holes, put them in, then you can withdraw the blood. And you need to take special trochars to avoid delusion with peripheral blood. So you see, you go even deeper now to get different sites where you can draw your cells. And then you can use growth factors. The most commonly used is probably PAP, and from the ESCA, we just published an ESCA consensus on the use of injectable autobiologics in knee osteoarthritis, which you can all see on the ESCA website and download there. So what does the matrix do? The matrix holds the cells in place, and the matrix can try to optimize the differentiation of the cells to get perfect cartilage regeneration tissue. And there's lots of basic science literature out there. The biggest review is that from POT that showed that the matrix actually achieved better cartilage regeneration. And it's quite easy. We published that in VGSM, the technique. It's a defect preparation. Then you can perforate the subchondral bone here using small K-wires. Then you can cut the membrane. You dry up the joint, remove the fluid, and then you can mold in the membrane. It usually sticks very well. And then you can move the joint and see if it holds. If it's not holding, which almost never happens, but then you can use some fibrin glue. So it's quite easy to do that. This is an example of a cartilage effect of the patella, which are sometimes not so easy to reach. And it's always difficult to get some matrix in there, especially if you suture it. And the membrane can be molded in very easily, very nice. And then if you look at MRI after six months and two and a half years, after two and a half years, you see really good cartilage tissue regeneration, whereas after six months, it's quite immature tissue. It takes some time for the tissue to mature. Alberto Gobi from Italy did a good study comparing this kind of membrane with BMEC versus microfracturing, 25 versus 25 patients in big cartilage lesions, 4.5 versus 6.5. And basically, what you see after two years, the IKDC taken on Lysol is quite similar. And then after five years, it spreads a little bit. The microfracturing gets worse, and the HeLaFast and BMEC gets better significantly. For the bigger lesions with the ACI, there are lots of systematic reviews out there to hear that show that we have good midterm to long-term results using cartilage transplantation methods. This one, 600 defects in 10 studies, showed a failure rate of only 10%. We in Germany use lots of this kind of ACI. It's the spheroids. Each of these spheroids is made out of 100,000 cells. The advantage is it's implant-free, it's no foreign material, and they already have the extracellular matrix synthesized. You can inject them into the defect, and then after some time, they grow up and fill the defect. There's also a systematic review evaluating this method, 10 studies, only short to medium term follow-up, but showing significant increases in subjective quality of life, satisfaction, pain reduction, and improvement in joint function. And when available, MRI and second look arthroscopy shows good defect filling and integration. So this is a promising method, but long-term studies are lacking. The last method is the MINS cartilage method. The principle is a one-stage cartilage transplantation, and you have to make very small pieces to allow the cells to grow out. Because if you put in a big cartilage piece, the cells do not grow out. So you have to really make small pieces. And then if you have a defect like this, with lots of cartilage volume already there, you can prepare the defect, put in all the MINS cartilage, and then you can either seal it with fibrin glue, or you can put a membrane on top of it, and then you already have really good regeneration. But this is a method evolving. The available clinical evidence is limited. To give you a glimpse on what we do in Germany, we have a cartilage registry. So there are almost 6,000 cartilage defects in there of patients. And we have the young patients at the end of the 20s, and we have the patients at the end of the 40s. So the traumatic and the more degenerative defects. And what you see, the bone marrow stimulation is under 2 square centimeters, the osteotransplantation about 1 square centimeter, the ACI around 4 square centimeters, and the matrix-assisted bone marrow stimulation right in between BMS and ACI. Internationally, at similar microfractures, the most commonly used methods, you can use lots of osteochondral allografts. We can use that in Europe, only rarely. And what's interesting, that almost half use biologic augmentation already, using scaffolds, PAP, BMAG, hyaluronic acid to improve the regeneration. But how can we get our people back to sports? The last slide, and Aaron Critch did a nice systematic review and showed that microfracturing had the least return to sports, but was quick with 9 months. ACI took much longer, almost 1 year, but had return to sports rate 82%. And oats, of course, had the best return to sports and the quickest, but was only available for small lesions. But you can also see that from 2 to 5 years, the TECNA score decreases a little bit again. So the take-home message. Bone marrow stimulation is for small defects. Its indication can be extended by using matrices. For the bigger defects, it's still the cartilage transplantation, gold standard in Germany. And the mince cartilage is some method that can evolve. And this is how I do it, a little bit extend the metrics associated bone marrow stimulation and the ACI for the bigger defects. So as a take-home, microfracturing is established, but it has size limitations. You can burn bridges if you overextend the indications. The metrics associated bone marrow stimulation fills the gap between microfracturing and ACI. ACI is the gold standard for bigger lesions. We still have to see what mince cartilage will lead us to, as well as the role of stem cells from bone marrow or fat. And of course, don't only look at the cartilage, but look at the joint in general. Look at the malalignment, the ligaments, look at the meniscus. And that's a perfect topic for the next talk. Our president, Roland Becker, will talk about the role of osteotomy with cartilage lesions. Roland. So Thomas, thank you very much. I think you got a really nice overview about all the different cartilage procedures. It's just summarizing here what you can see, basically. But you know, you shouldn't forget, osteotomy is the most powerful tool, and I think that's very important to keep in mind. Because what is the reason? I mean, if you consider the loading of the knee, and this goes basically up to four times body weight. And this is shown on computer models, but also in vivo studies, actually in Berlin. And you know, these are the measurements and the numbers you see in activities in daily life. So it's going quite up. And sometimes, if you have an overweight patient, and you see what the loading of the knee is like, you can really impress sometimes your patient, and maybe encourage them to lose their weight. The interesting part is, you know, considering this loading of the joint is, how is the survival of autogenic chondrocyte implantation as osteo-chondro-allograft transplantation in considering joint alignment or lower limb alignment? And there was a very interesting study by the Freiburg Group, and they found, you know, out of the chondrocyte implantation in HTO, the valgus alignment showed basically a negative effect on survival in patients, either with or without high-TB osteotomy. But the neutral alignment showed the longer survivorship than virus or valgus alignment. I think that's very important. In osteo-chondro-allograft transplantation in HTO, leg alignment remained insignificant, so there wasn't really a significant difference. But female and smoker, which we probably know, were negatively correlated, especially we know that there's a lower outcome in females and smoker when they get actually an HTO. What is very important in valgus alignment, and this is maybe one of the reasons that the outcome is lower, they have a lower abduction moment at the knee joint, they have no lower knee abduction angle, and a greater angle inversion moment at peak vertebral ground reaction force, and this basically might increase the femoral T-ball loading. We performed a study where we used a kind of twitch interpolation technique to find out actually what is the maximal voluntary contraction and voluntary activation of the quadriceps muscle. We did it in ACL patient, but we also did it in patient prior and after HTO. Interestingly, we found after HTO, basically, the voluntary activation of these patients is lower, and this might have something to do with the correction, how much of correction actually performed. And the contralateral side, and this is actually in contrast to other findings with the meniscus and with the ACL actually we found, there's no significant difference. So there was a very important project, and we have released basically now five contents of the project with ESCA, started in 2013 with the meniscus. You heard about the osteobiologics, and now about the osteotomy, and about the ACL revision as well. And this study was actually chaired by Mac Dawson and Matthew Olivier. And this is the kind of principle we use when we perform the consensus, which is supervised and consulted by Philippe Bofis. And we always have this kind of steering group, and then we have a rating group, and finally we have a peer review group. It's a quite long process. In general, it takes about one to two years actually to run in these kind of consensus projects. And it's a little bit more in-depth than just doing a Delphi consensus. For instance, in this project, there were all these different societies were involved. So 46 different national societies were involved in this kind of consensus created in the peer group, actually, the peer review group. And this is basically acknowledging all people who were involved. So almost 100 people. It's a huge work, as I say. There's a big advantage of performing this kind of consensus, because we are merging scientific evidence of the literature. And especially when we started doing this consensus, sometimes we were really surprised how much lack of knowledge actually we have in our field. And this is a combination with scientific evidence, because we found it's not only scientific evidence, which gives us really some kind of guidelines and recommendation in daily practice. And it's a combination to our clinical experience, basically. I think that is what is very important. So regarding the indication, any patient with predominantly extra-articular virus deformity using intra-articular pain and preserved lateral compartments will benefit from knee osteotomy. It's a very important message. So considering the planning, it's assessment of bone deformity and, of course, articular wear performed of multi-planar x-rays, very important. In addition, you might do some CT and MRI investigations as well. So you need the frontal, the jaded plane, but you need always full weight bearing long leg x-rays. I think that's very important to identify, basically, the alignment of the lower limb. And then actually define where's the potential surgical site to perform the optimal correction. Just to give you an idea. You see on the left-hand side, it's a physiological morphotype of the knee. So then you have this kind of virus morphotypes. That means you have an extra-articular deformity. So if you perform the correction, you see what happens. If you have this physiological morphotype, actually, you overcorrect, basically, the knee. And the joint and obliquity go from the middle to the lateral side. And studies have shown if you change dramatically this kind of joint and obliquity, these patients do not as well. And you perform these osteotomies. So but if you have a virus morphotype, then you actually do a proper correction. Maybe you have a particular joint line to the mechanical alignment of the tibia, but you should never overcorrect. In these cases, on the left-hand side, you should consider maybe do a biplanar osteotomy. So you're all aware about Paley's book about osteotomies, and you know the angulations. And that's what you have to calculate. If you have a bigger deviation of the normal angulations, normally in about 87 degrees, then you have to do it. That's the side where you have to do the correction. That's very important. And you see the grading is B. So that means, you know, when we designed this kind of consensus projects, we had this grading of A, B, C, and D. A was a high scientific level of evidence. B was scientific presumption. C, low scientific evidence. And basically, D was kind of level five, just expert opinion, basically. And you see the agreement of all these people who were involved were quite high. But now, Michael Hirschman, actually, he introduced a very interesting structuring of alignment because he took in consideration the femoral mechanical alignment, tibia mechanical alignment, and the joint line obliquity. And he classified different kinds of types, actually, which you find. Of course, in the middle one, probably, that is the most frequent one. But still, there's a huge variation. And for that reason, it's so important to have the full weight-bearing X-ray and to really see how the joint line looks like and try to preserve this kind of joint line orientation. And then try to identify either they have to do it on the femoral or tibial side, or sometimes it is necessary to do the osteotomy on the femur and on the tibia as well. So where should the weight-bearing line be positioned to treat a knee with medial osteoarthritis in varus-mar alignment? And this is what, actually, is the recommendation. And it's still with a low level of evidence, I have to admit. There's no specific target point can be recommended. But based on historic results, target ranges of between 50% to 60% or 68% have been proposed and may be implemented, deepening on patient-specific and degree of osteoarthritis. In the light of the more recent evidence, rating to joint obliquity, the consensus group would aim to add the lower range of correction. So that means the Fuchi-Zawa point, which we took always as a kind of, you know, our target when we perform the osteotomy, maybe it's a little bit too much of overcorrection. And if I tell you, you know, if you remember the information which I gave you about the varus alignment, probably it's too much. And what is now, actually, and this is according to a study by Horloch, where you see the outcome of COOS after the correction in term, you know, of the amount of correction, probably the cartilage defect. If you have kind of osteoarthritis of grade 1 or 2, you shouldn't correct more than 50% to 55%. If it's grade 3 of osteoarthritis, you should be probably up to between 55% and 60%. But probably you should not exceed 60% considering the middle side to 0% and the latter side 100%. Considering performing an open wedge high tibial osteotomy, there are different ways. You just do a single plane osteotomy, as you see on the left-hand side. I mean, we most frequently do biplanar osteotomies, so either your osteotomy is going above the tibial tubercle or below. But when you see the contact and the strength, actually, of your osteotomy, if you go below the tibial tubercle, you have the highest contact, you have basically the highest biomechanical strength. That means, in this case, we can allow our patients to start quite early with full weight bearing, which they, of course, appreciate. Surgery should be performed, and again, the European consensus, at the level of deformity we just discussed. Stop creating anatomic abnormalities or joint and obliquity. Protect the hinge and the soft tissue. Promote bone healing. That means gap follows optimal plating, and biplanar cuts are recommended. Patients will return to the preoperative work at around three months, return to sport at six months if they follow full rehabilitation program. So let's conclude. Natural loading of the knee is important for successful cartilage procedures. If you consider cartilage procedures, maybe you have to start with an osteotomy and do it in conjunction with the cartilage procedure, or even just do an osteotomy and see how the patient will perform, and then maybe secondary, you still can repair the cartilage. Identify the site of deformities. I think that's very important, and inspect the joint and obliquity. I really have to highlight this. Individualize the target point for correction. So maybe the Fujisawa point is not more appropriate anymore for this time. Design of small alignment improves muscle function, and they are superior clinical outcome. Very important to know when you have properly aligned your lower limb. And just give me one second. I want to announce our speciality days, which is really focused on the knee, shoulder, ankle sports medicine. And this will be next year at the end of November in Warsaw. And then, of course, our Congress, the 21st Congress, ESCA Congress in Milan, specifically the ladies will like it, I'm sure, from the 8th to the 10th of May. And we all really welcome you to come to Europe, and especially to Milan. And finally, you know, these are the little booklets which you find on the ESCA booth. And these are actually the last three consensus which we have performed. And you can also find all the material of the consensus and the results at our website. Thank you very much.

surgical techniques

cartilage treatment

microfracturing

biomaterials

osteotomy

patient selection