Hello. I'm Dr. David Dedock. I'm at the University of Virginia. We're in the professor and Division Head of Sports Medicine and Team Physician for the University of Virginia. I'm going to talk to you guys about trochleoplasty, which is a new and emerging technique, and really hope that you get a better understanding of when to do this and how to do this. These are my disclosures. First of all, it's important to understand how influential trochlear dysplasia can be, and patella instability. Here's a recent systematic review and meta-analysis which reviewed 17 studies, looked at the risk of recurrent dislocation, and looking at the odds ratio and various anatomic risk factors, trochlear dysplasia bubbles up to the top. It's more important than malalignment in the coronal plane with a TTTG, patella alta, open physis, anything else. As you can see, when anatomic risk factors start to become combined, the risk of recurrence really goes up. This is especially true of patella alta and trochlear dysplasia. My stepwise approach to trochlear dysplasia is first we got to identify it. We're going to go to the lateral X-ray to make this diagnosis. The key is to look for this spur, which is the blue arrow on the lateral X-ray, and also to look for a crossing sign. The blue dashed line is the base of the trochlear groove. Blumensat's line is in the notch. It exits the base of the trochlear groove. The blue dashed line continues anteriorly. If it meets the same level as the red dashed line, which are the medial lateral condyles, then at that level, it's flat. That's the definition of a crossing sign. If the base of the trochlear groove is at the same height as the lateral condyle. If this continues further anteriorly, which are the blue dots, then that's a supratrochlear spur. You know that you need three-dimensional imaging, such as an MRI or CT to better understand it. Now, it's not about flatness. This is a common misconception. This is the same knee on the left at 45 degrees of flexion and on the right in full extension with a CTR program. You can see this convex supratrochlear spur that's going to have tremendous influence on this patella. I really don't pay much attention to the sunrise view because that doesn't tell me much about the trochlear morphology when the patella is an extension and at risk to dislocate. When we see this convex supratrochlear spur, the patella could go either direction very easily. Next, I'm going to quantify this supratrochlear spur by going to the sagittal cut or the notch view with the three-dimensional imaging. On the left, you see on the plane X-ray, if I drop a line down the anterior femoral cortex, that all the bone that sits in front of that would be sitting proud or anterior to what should be the base of the trochlear groove. The base of the normal trochlear groove sits flush with the anterior femoral cortex. On the right, I'm quantifying that with an MRI. I'm going to measure the amount of bone plus cartilage that sits anterior to that line down the femoral shaft. That shouldn't be there. That again should be all flush. The trochlear groove should come up flush with the anterior femoral cortex there. This is the view with the notch, with the cruciates in the center. You know that should be the lowest part of the trochlea. Seven millimeters in terms of the size of the supratrochlear spur is when I'm going to start to think about doing a trochleoplasty. But I'm also going to look to see what's that morphology. If this is a convex shaped supratrochlear spur, as you see here, that's going to have much more influence on the patella, and I'm going to be more apt to do something surgically about that, as you can see on the sagittal cut here too. It's really very dysplastic. Now, DeJure has provided us with a classification system that really describes the shapes, but doesn't necessarily guide decision-making for surgery. Type A is basically flat. This is not a problem. You do not have to do a deepening trochleoplasty for type A. Type C, even though it's fairly dysplastic, doesn't lend itself to a deepening trochleoplasty, because it's really just a very hypoplastic medial side, and a rounded ridge on the lateral side. There is no supratrochlear spur sitting in front of the femoral cortex, so there's no ability to really drop it down. That doesn't work for a type C. It's the Bs and the Ds that we're thinking about deepening trochleoplasty. B is just a very large supratrochlear spur, and D on the medial side has that hypoplastic part of the trochlea, and that becomes a cliff sign with a large spur. The Ds especially, and some Bs, we consider deepening trochleoplasty. Now, I'm going to look to see, does this really influence patella tracking in terms of a patient's exam? This patient has a jumping J sign every time they extend their knee. You can see they failed some operations before, which is important. That patella jumps and completely escapes the groove when they come into full extension. On the left is a superior lateral arthroscopic view of a jumping J sign. You can see it starts lateral, and then it's going to jump into the knee as I flex the knee on the arthroscopic view. You can see all that chondrosis and cartilage damage, and appreciate that this is a large supratrochlear spur sitting anterior to the femoral cortex. What does a J sign mean? This is when the patella completely leaves the bony restraint of the trochlear groove in full extension. That represents either patella alta or trochlear dysplasia with a spur, a convex spur, which has really influenced patella tracking, or both. The combination of both is especially important because the higher that patella starts, the more the dysplastic trochlea influences the patella every time the knee bends, and you get that jumping J sign. I'm going to carefully look at patella alta. That's going to influence my decision-making. I'm going to do that in two ways. One is this CD index, the Caton-Deschamps index in which I'm going to divide the articular length of the patella by the distance from there to the top of the tibia. A normal ratio should be one, greater than 1.2 is considered abnormal in patella alta. We don't use the insoles to body ratio very much anymore because that includes the full length of the patella and the patella nose has nothing to do with congruity, articulation, or patella stability. It's really about the articular cartilage length of the patella. I'll also look at the patella trochlear index, which is the amount of cartilage overlap for the articular length of the patella and the trochlear cartilage with the knee in full extension on the MRI. That ratio should be greater than 25 percent. Less than that is also the same as patella alta. You could have a short trochlea that would behave the same as a high-riding patella. Both create problems with congruency and stability of the patella such that the knee has to flex to greater degrees of flexion for the patella to get engaged in any groove. A lot of the dysplastic trochlea, as you'll see, will have a very hypoplastic, short, medial part of the trochlea, and this can be important. The next thing I'll ask is, well, maybe there's dysplasia there, but do I have to change it? Maybe I can work around it, especially in light of patella alta. Here's a patient that had a patella trochlea index of basically zero with no chondral overlap. They sat very far lateral, making it hard to even measure this in full extension. But they did have dysplasia in a spur, not quite as large, but six millimeters. You can see here that in full extension, you see patella cartilage, but no trochlear cartilage because it sits so high. Then on the bottom right view, you see the patella tendon draped over the lateral trochlear ridge, really visually demonstrating the vector that's going to pull this patella laterally. Malaligned with a high TTTG, a jumping J sign, and patella alta. In this case, a pretty reasonable groove further distal. That much patella alta could really move it down distally. I moved it down 12 millimeters and medial 13 millimeters. When I go that far, I'll do a step cut and remove a block of bone and transfer approximately. I'll dock it. I've gone to using three screws routinely for stability and healing. That solved the problem for this person because I could move it down to a normal height and get past that dysplastic spur trochleoplasty not needed. Who else doesn't need it? A flat trochlea, so flat on flat. A good example here on the left with an acute dislocation, flat on flat can be balanced, often even with an MPFL alone. It's not the flatness that's the indication, it's really a convex spur that's the indication for a deepening trochleoplasty. My decision-making, I'm always doing an MPFL reconstruction with these patients, and I'm considering the trochleoplasty with a type B or D, and a convex shape, and a bigger spur that definitely influences the tracking on exam with a jumping J sign. Especially if I see patella alta, or if it's a revision scenario that's already failed a well-done procedure. There are two basic methods to do this. There's a thick shell. I'm going to show you that with a video, and then also a thin flap technique. Thick shell is popularized by David Dujour, which is where I learned this. And it's really an osteotomy of an osteochondral shell that's three to five millimeters thick. The thin flap method thins it out even further to a two to three millimeter thick shell, and it's really very pliable, and then you reshape the bone beneath it. This is popularized by Dr. Schottel. And this is the technique. You see here the crossing sign on the lateral, and the supratropular spur, and you see the convex shape to this, and it's also a metal line sitting lateral. This is the video you've seen with the patella tracking laterally here. I externally rotate the foot slightly, which makes the jumping j-sign even more pronounced. Look at that chondrosis. This patient was 19 years old and very petite, but look at the chondral damage that's happened. When you open the knee, you can really appreciate how big this spur is. So proximal is the top of the screen, and this is about a 12 millimeter spur actually once open, and I'm referencing the anterior femoral cortex. I've peeled back the supratropular fat and periosteum, peeled it back with a bovie, and here's what I'm gonna plan to do to make my cut. So I'm gonna explain all these as we move through this. I've marked with a dotted line the existing groove. Most of the time, that tends to be fairly medial, abnormally medial, making it even harder for the patella to get in the existing groove. I'll take the planned groove more straight up the shaft of the femur, which is the top dot on the right. That's where I want the new groove to go, and I can lateralize the new groove and actually reduce the TTTG. Now I'm deciding how far distal I'm gonna go. So I'm taking a line from the anterior femoral cortex down distally to where it intersects the cartilage, and that's the horizontal line at the bottom of that. So that's how far distal I'll go, and then I'm gonna go to the transition point on either side where the medial and lateral condyles transition in their curvature from going up to going down, and that's the transition point for the extent distal that I'm gonna go. So I'm gonna now start by removing a wedge of bone all the way around the margin of the articular cartilage. I'm gonna start slightly on the articular cartilage there. It's important to do that, not to start too far away, and I'm gonna save this bone for later and mince it up. Start well proximal on the shaft, so you remove the entire spur, and now I'm gonna create a cavity, and I'm gonna start with a three millimeter egg burr in the TPS machine because it's more aggressive, but I'm only gonna go partway down because it can be more dangerous for cartilage perforation. Save that slurry, and now I'm coming in with a commercially available guide that has a five millimeter offset. So that cannot get my shell too thin. You want to use this thing side to side, but it's because it's on a drill, it's not aggressive enough. You have to rotate around a pivot point like a windshield wiper there to remove the remaining bone, and then you're gonna be left with a three, excuse me, with a five millimeter Osteochondral shell. So the thin flat method would then go to a second guide that's only a three millimeter offset. You would continue to thin the shell, and it would become very pliable, and you can lift it up just like the hood of a car. I stop at the five millimeter thickness. I'm a little concerned about thermal necrosis. Now I'm gonna crease and osteotomize my shell. I place an osteotome behind it to prevent it from deflecting too much. You see it bounces like a diving board, and that's a 20 blade and a bone tamp down the center of that where I want it to bend, and then I do the same on the edge on the lateral side. The medial is always malleable enough, but the corner of the lateral side, you need to bend down like this. Be careful not to let that lateral cut intersect with your central cut, or you've got a free shingle of bone. So just at that lateral ridge, you need to cut it. Now I'm gonna take the slurry and the little tiny pieces of bone chips. I'm gonna fill any voids that are underneath there that I can pop it with my free or elevator, and I'm also gonna place that bone along the edges of the transition where I stopped creating that cavity so that the osteochondral shell doesn't drop down or to get depressed there. So I need to support that transition. Now I'm gonna come in with a absorbable tap-in suture anchor of choice. This is a 2.9 millimeter absorbable biocomposite, and I've placed two number two vicral sutures through this central one, and I have two limbs coming up to over across or at the top of each shingle. Pull them tight, tap them down proximately, and you can plan where you wanna place this based on how you want to reshape this at the top. As you can see there, hold it with your fingers, you take the suture anchors down, and now the antefemoral cortex is flush with the base of the trochlear groove. That 12 millimeter spur is completely gone. You see the femoral shaft extends down the base of the trochlea, and it's completely corrected. My main goal is to drop the spur down to flush. I try to get some lift and depth, but it's not so much about depth in a groove as it is about dropping the spur down. Remember this started as a convex shape, and we want it to be no longer convex, at least flat in the center, but by packing little bone chips around the edges here, you will provide some lift. And here you can see my sunrise view before and after, and the spur, you get a sense for how far approximately I start with that osteotome to get the entire spur removed, and then the base of the trochlear groove coming approximately is now flush with the anterofemoral cortex. It no longer went well anterior relative to the cortex before. That's the goal. Drop it down flush. You do get some lift, and you can see a very nice congruency. People ask about, well, what about the patella? Does it articulate differently now? Did you change the shape? But really all I'm doing is carrying the native shape of the groove that's down here approximately so the patella still articulates in a very natural way in full extension. The articular cartilage tolerates these vicral sutures very nicely. These are three different patients. This groove here on the left is where I creased it, but you really can't see where the vicral was. It was absorbed in about six weeks. This is fresh cancellous bone. It heals readily to the bed. You just don't see problems with loss of fixation with number two vicrals. I use two just in case one breaks, and it's very cartilage friendly, as you can see. That was where one of the anchors went. Our results have been published in the Arthroscopy Journal 2020. You can see here, and this was a group of patients, half of whom were revisions of prior surgeries that were sent in, and we had no recurrent dislocations or progression of arthritis radiographically, and we had nobody with fixation failure, high patient satisfaction, and return to sports. Now, postoperative stiffness can be an issue. Here's my rehab protocol. I do all of these as outpatients with regional blocks, often with a nerve catheter, if insurance will approve it, and start immediate physical therapy. It's important to do that within the first few days and really explain to the patient how important it is to start bending the knee day one. If they move it within the first few days, they're home free. If they're afraid to move it and leave it locked in extension, they can get pretty significant scar tissue and have trouble getting flexion, but if they move it, they're fine. A brace setting, just in case they stumble, I use a brace the first six weeks and 50% weight bearing, zero to 90 or zero to 70, whatever you're comfortable with, but I will definitely let the therapist move that knee to 90 degrees day one. And out of the brace, off the crutches at six weeks, progress is tolerated with resistance exercises by three months and return to sport by five to six months. Thank you very much.

trochleoplasty

trochlear dysplasia

patella instability

lateral X-rays

surgical intervention