Thanks for being here. Thank you. Appreciate it. So this is our research team on the right. Have several engineers. High level of interest at this point, using mostly 3D association with the School of Engineering at Yale. The majority of patellofemoral articular lesions are related to aberrant mechanics. A majority of these are related to lateral overload and progress towards arthritis. I think everyone here probably is familiar with that scenario. Impact lesions are different and require different treatment. Many of these are proximal from a fall in a flex knee or a medial patella lesion from dislocation. And of course, there are others, OCD and other causes. Those are the main ones that we see. If lateral entry point and focal overload, in other words, if you're coming in from the lateral side and you're sitting there, anterior medial tibial tubercle transfer osteotomy will offload by lifting and advancing the patella into the trochlea. So I start off with that and using a lot of 3D images here to make a point that I'd like to make. And that is that osteotomy and tibial tubercle transfer offloading articular lesions is really powerful and that often there's no need for any resurfacing if you can unload the lesion effectively in this manner. So if you look at these images below, and this is Armida Manofzadeh, who is a PhD engineer who works with us. You can see how on the lower side, if you take dislocators, how the patella is. This is at 20 degrees of knee flexion. These knees are not centered in these particular instances, not that they aren't in others, but this gives you an idea of what happens in some of these people who are sitting laterally and what that translates to is focal overload and eventual joint breakdown. So the premise here is 3D is better than 2D for understanding dysplasia complexity and articular lesion location and therefore for planning surgery. So 3D imaging from CT or thin-sliced MRI at 20 degrees knee flexion, again because we want to have the patella articulating when we image it, gives better understanding of articular loading. And so I point this out partially because many of the images we look at in MRI are with knee extended and you don't really know where the patella is going on that type of image. So moving the patella by tibial tubercle transfer can improve tracking and optimize load distribution. And this is where the engineering comes in. You can see how many of these patella sit and of course we're talking about articular lesions, but you can also see why articular lesions form with the focal overloads that occur with that sort of pattern. One important goal for treating an articular lesion and sometimes the only goal I would say is to offload it. So you see these different patterns we have, there's distal, there are medial lesions as you see, type B, and then lateral lesions as you see over there in C, and then diffuse lesions. And it's the medial lesions that we worry about because we don't want to move the tubercle medially onto that and the diffuse lesions. And those are the ones that we think that osteotomy may not play as much of a role and then we're looking more at ACI of some sort. Anteromedial tibial tubercle transfer reduces load of the patella femoral joint more than a medial tibial tubercle transfer osteotomy as shown by John Elias and Andy Kazgaria, which makes sense because there's anteriorization as well as medialization. Also the anteriorization component lifts up the distal pole to offload the distal patella lesions. So an anterior medial tibial tubercle transfer, and I admit my bias to that particular procedure, builds stable relief of articular lesion-related pain long-term. And we did our minimum 15-year study without articular cartilage implantation. So now we know that we get long-term good results and joint preservation. Seth Sherman affirmed this in 2019 as safe and effective. So you want to design your surgery to optimize articular loads. I think that's the main message I'd like to deliver here. 25 years after anterior medial tubercle transfer in the image on your right there, you can see complete joint preservation by redistributing loads and offloading the area that was overloaded. And the joint on the right then is preserved. The left one in this particular patient, life caught up with her. She didn't find the time to get the other one done. And you can see that joint is completely destroyed, not having been brought back into a balanced relationship with the trochlea. So further in favor of this approach to these articular lesions that you can offload is a review by Yalcin and Farrow, recently just came out, Orthopedic Journal of Sports Medicine. 345 tibial tubercle osteotomy procedures, 294 anterior medial tibial tubercle transfers at the Cleveland Clinic done by 14 fellowship-trained surgeons. Two percent major complications with no tibial shaft fracture. And the complications, the major complications including two pulmonary emboli, one deep infection, one DVT, one tubercle fracture, and two failed fixations out of 345 procedures. So patella entry mechanics and cartilage defect treatment and joint preservation. I think this has a lot to do with it because if we understand the mechanics and why these lesions occur, then we can better understand how to unload them and hopefully avoid progression and maintain a good joint long-term. Patella launch and tracking path are integrally related to stability and focal loads. So if you look at this image from Kristen Yu's publication in arthroscopy techniques, just recently came out, you can see what we call the entry point over here. This pertains a lot to instability because you can see where the patella enters in this very dysplastic knee and how far it has to go to get to what we call the transition point, which is where it becomes engaged in the deeper trochlea. So you're all aware of this deeper trochlea. What happens here is in normal people, most people, it kind of comes in more linearly. And this, of course, is a structural J sign as you see it here. But you can also imagine in your mind's eye the loads on this patella has to go from here to here in early flexion unloading this joint and the impact that can have on articular cartilage. So the anterior medial tibial tubercle transfer elevates that tip, unloads, and advances the patella closer to the deepening trochlea here. So it basically gives a mechanical advantage and redistributes the load more equitably, which we now know leads to long-term joint preservation. When the entry point for the patella is lateral, then we move the patella, as you see here's the lateral entry point in this 3D reproduction starting out here, and it has to get to this transition point. So we call this the entry point transition point angle. And we think that this is where a lot of the problems occur in people that have aberrant trochlear morphology and why some people go on to break down their cartilage. Not everybody, and in less severe situations, they seem to get by okay without cartilage breakdown. And you can also print articular cartilage, which is really interesting. So if you want to look at an articular lesion, the problem is it's expensive because you have to do twice as many cuts on the MRI. You'd have to have a radiologist who's willing to work with you. Basically thin slice MRI, you have to talk to radiology. So this is not for everybody. But you can actually print the cartilage and you can look at exactly where those lesions are and exactly where they are. We can figure it out pretty well in 2D, but if you really want to know, I mean there's nothing that beats this, particularly if you're considering an osteotomy. Printing and examining the 3D print gives a very different perspective. When possible, understand in 3D and move the tubercle as needed to unload articular lesions, gain stability, design articular resurfacing, and preserve cartilage long-term. And I've got to say, we're just joking about it in a way, this is almost like facial recognition because all these trochleas look so different. You could actually take one of these printed trochleas and hold it up in the airport and everybody in this room would have a different looking trochlea from what we're seeing. They would have elements of problems that would lead to certain problems, but that's how sensitive this is. So the anterior medial tubercle transfer is best to advance the patella closer to that deeper trochlea to unload and maintain congruity. So this is fairly dramatic here. You can see here's a normal knee on the left and here's a dysplastic knee on the right. And you can see how where the X is is where the patella actually enters. You can see on the left it gets in and it gets to that deeper trochlea pretty normally. From here, it's got to go all the way around this. This would be a de jure C-type trochlea here. And this is a long path with a lot of load hitting the distal pole of the patella right here in early flexion. And that's probably going to lead to some articular problems. So that's why we think that moving it closer and tipping up the tip and helping it to circumvent this and get into that trochlea may optimize congruity and preserve cartilage. So there's power to tibial tubercle transfer, synergy of anterior medial tubercle transfer and distal tubercle transfer, and selective proximal spur recession to enable the patella, if there's a little prominence here, may want to recess this. I do that with a high-speed burr arthroscopically to unload and align, preserve congruity, preserve joint integrity of cartilage. Preserve cartilage long-term, tubercle is medialized or distalized to optimize focal load. Beth Subernstein said that tubercle transfer is appropriate for maltracking, unloading articular lesions and some instability surgery. It turns out to be less than a third of instability patients actually need to have an osteotomy. Most can do medial reconstruction. So medialize the entry point selectively, anterior medialize to align. Articular patellofemoral lesions that can't be offloaded, autogenous osteochondral transplants have worked very well for me and many patients. Gives you the full cartilage, autogenous full cartilage and bone. The pearls for this, in my opinion, are patella bone is very hard. Must use a drill for the recipient site in the patella because it's so hard. Place the guide pin for the drill precisely perpendicular using the oat harvesting tool. Make sure you remove enough bone from the oat to set in the appropriate depths. So there are little technical pearls to think about. But this actually generally works well. ACI, many options are available but most cost is substantial. Two surgeries are required. Limited larger lesions that can't be managed adequately with a tubercle transfer, offloading or an oat transfer. It's my approach. You can see all these names down here of people who are leaders in this field. I'm sure you're aware of those. And they know more about the actual resurfacing process than I do. And one of the reasons for that is because I've had good luck unloading lesions. So I haven't done that much actual ACI. So here are the lesions when they're medial and diffuse where we need to think about ACI. Thank you. If you want to learn more, come to our patellofemoral master's course at patellofemoral.org. There are about 10 hours of instruction on all aspects of patellofemoral joint error.

patellofemoral articular lesions

aberrant mechanics

lateral overload

anterior medial tibial tubercle transfer osteotomy

3D imaging