So I'm David Deduck at the University of Virginia and I'm going to talk about the role of trochlear dysplasia and maybe better understanding of when to correct that and how to really how to recognize it first and foremost. And the lateral x-ray is really the key. You need to recognize this on the lateral x-ray. So the notch exits with that blue line which is going to be the base of the trochlear groove and as you follow that superiorly where it meets the red line that's at the same level so that's going to be flat. That's your crossing sign. If it continues further anteriorly that's the blue blue dots excuse me the green dots and that's a spur that sits anteriorly and that's convex and that's important to understand. It's not about the sunrise view. The sunrise view tells me very little. This is the same knee on the left at 45 degrees of flexion on the right in full extension and you can see you have that convex anatomy of the proximal trochlea and that's really what's important and you're not going to be able to fix that problem with just an isolated soft tissue procedure. So the sunrise view tells me very little. It's really about the lateral x-ray. When I see that super trochlear spur I know I need three-dimensional imaging so I'm gonna get a CT or an MRI MRI almost always and it's about convexity not flatness. So flat on flat can absolutely be balanced. You can balance that off with a soft tissue procedure alone. Maybe you need to do tubercle work but flat on flat can be balanced especially if you have good overlap of your cartilage for your patella and your trochlea and extension as you see there but it's more about a convex shape of that proximal groove. That's going to give you those jumping J signs especially in conjunction with a lateral pull on the patella from a vector and then it's like the egg on the table. You don't know which way the patella is going to go. So then I'm going to try to better understand how severe is this dysplasia and quantify it. So a line down the anterior femur should go to the base of the trochlear groove. Everything that sits anterior to that line is your super trochlear spur and I'm gonna measure bone plus cartilage and that's going to give me an idea of the size of it. Now radiographically technically dysplasia is is determined by a spur height greater than five millimeters or flatter than 145 degrees for your sulcus angle. That doesn't really guide treatment decisions. For me I use seven millimeters and a convex shape to consider a trochleoplasty and then we're going to be thinking about dropping that down and as you see in the cartoon dropping it down flush with the anterior femoral cortex. That's my goal. Depth is nice but getting rid of the convex shape is is really the goal, the primary goal. The du jour classification is really descriptive. It's the B's and the D's that we're targeting for treatment but this also doesn't guide treatment decisions. It just is more descriptive and we're really focusing on a super trochlear spur that sits anterior to the femoral cortex and that's what we're going to get rid of. The C's really don't have that spur that sits anteriorly so it's very difficult to actually drop it down because it's already sitting flush to the to the front of the cortex. So next on exam, how much does this dysplasia actually affect the patella and the tracking? The key exam presence is going to be this jumping J sign. That's going to signify a convex shape. That arthroscopic view on the left is a superior arthroscopic portal, superior lateral looking down and you can see that there's a huge spur sitting in front of the femur. You can see that patella really jumps as it goes from lateral to medial and this person is of course asleep. There's no quad tone. You see the chondrosis developing and it jumps over like that and these are the dramatic jumping J signs. So the J sign, when that's happening, the patella is completely leaving the restraint of any bony groove and that's typically present with a patella alta or dysplasia or often both and often valgus or rotational alignment issues too because there's always going to be an abnormal vector pulling on that patella laterally in addition to bony dysplasia of some sort. So I try to simplify these things, these concepts as much as I can and really think about shapes and vectors and a vector is, if you've got a bad vector pulling that patella, you're not going to solve that problem with an isolated soft tissue procedure with an MPFL. So you got to recognize that. So when do I consider trochleoplasty? Type B's or D's with that convex shape and a spur height that's greater than 7, that J sign on exam and especially if I've got alta or visions and I'm always doing an MPFL reconstruction with these patients. Always doing MPFL plus that and here you see that patient with a big jumping J sign while asleep and then the chondrosis and then the large spur sitting into the femoral shaft when opened up there and that we're going to drop down flush with the anterior femoral cortex. There are two ways to do this currently. The thick shell method and the thin flap technique. I'll follow the du jour lead on the left which is a thick shell method. We're going to basically osteotomize an osteochondral shell that's between three and five millimeters thick and then reshape it and fix it with vicral sutures to hold it in place while it heals. The thin flap techniques thins this out even further, lifts it up like the hood of a car and then removes bone beneath it, puts it back and fixes it again with vicral suture to hold it in place until it heals. My concern with that technique is maybe the flap can get so thin you could get thermal necrosis. I have no experience personally with it to know which is best. I've stuck with the one on the left. So I'll show you a video but the basics of this is I'm going to drop this down to the level of anterior femoral cortex. I'm going to start with an osteotome well proximal on the cortex, remove a wedge of bone and then I'm going to start to plan the new shape I'm going to have. So the native trochlear groove is typically abnormally medial on these patients. It develops with a medial inclination. You can lateralize the new groove to be a more normal vector up the shaft of the femur which is going to be the dotted lines there and then where we make the transition point is the inclination where it changes from going up to going down on the sides on either side, the inflection point. So the distal extent of the osteotomy is that blue line which is where the anterior femoral shaft would extend all the way down and intersect the cartilage distally. Here are the inflection points on either side for the medial and lateral extents. I'm going to draw it out and the new trochlear groove I'm going to make more lateral. So I'm going to begin by removing a cavity of bone. I'm going to start with the osteotome followed with a high-speed burr and then I come up with this commercially available guide to help resect the bone further. Then I'm going to cut it with a 20 blade and a bone tamp to kind of cut through the center of that for the new groove and then also in the far lateral side I'm going to cut that edge as well. The medial side is always malleable. You don't have to cut the medial side and you don't want these two cuts to intersect or then you have a free piece of bone but just that far lateral edge is necessary about 50% of the time and then you can reshape it. Then you're left with a cavity and an abrupt transition where the cavity stops and the intact bone begins. That could settle so you want to pack some of these little chips of bone you save from that wedge of bone you removed at the beginning of the case, mince it up, pack it underneath there. You can also fill any voids or irregularities and then fix it with number two vicral sutures with a knotless suture anchor in the center. Distal to your cut and then over each shingle two additional knotless suture anchors. So here's a video of the technique. You see they're abnormally medially again and now my desired groove is going to be up the femoral shaft. That's the solid line. There's the inflection point on either side so that's where I'm going to plan the extent of the osteotomy on the sides. The blue line is how far distal I take it which is extended from the anterior femoral cortex all the way down. Starting with an osteotome to remove this wedge of bone and then slightly encroachable the articular surface for your vertical part of the cut there. Take the bone out, mince it up so there's a starting point for the osteotomy. I come in there with a high-speed burr. This is a three millimeter egg-shaped burr to begin to create the cavity. I don't go very far because this is a straight tool with a curved surface. This is the commercially available offset guide. You want to use it side to side, our hands do, but because it's on a drill it doesn't go fast enough to remove bone. You have to use it like a windshield wiper as you see here and this does I think add a measure of safety for this procedure which is important because it's easy to perforate the cartilage using a straight tool on that curved surface, but if you use it like a windshield wiper you have that reference you know exactly where the tip is underneath that depth measurement tool and then you create a cavity and now I'm going to crease it. I put the osteotome behind it to avoid bending it too much and cracking it inadvertently. I crack the far lateral side and then you can reshape it just like this and again this is about a five millimeter composite osteochondral shell and then I'll pack some of these little pieces of bone especially right at that transition and then fix it with the with the vicral sutures. In comes a tap-in knotless suture anchor, absorbable and vicral sutures. I'm going to go to additional knotless suture anchors at the top. So you get some depth but the primary goal is to remove that convex shape and get it down flush to the surface. So that's the before and after. You get the concept of dropping it down and the before and after with the sunrise views. The cartilage tolerates the vicral sutures very well. These dissolve six to eight weeks and I've had a few opportunities for second looks. I've not seen any consequence to that whatsoever and rehabs you want to move these patients quickly. If they don't want to move right away because it's sore, it's swollen, I'll try tomorrow, they can get stuck in a hurry and it can be the stiffest knee you've ever seen. You've got to go in, they'll form a sheet of scar at that exposed cancellous bone. So immediate motion. I do this as outpatients especially with the femoral nerve catheter that works really well so they can start early motion and partial weight-bearing for the first six weeks. So these are our results that were published in the arthroscopy journal a couple of years ago but I think I want to frame this a little bit in terms of what it can't fix. So the think about the trochleoplasty as targeting a convex surface and one that really the shape of your of your groove is going to create a problem if you fix everything else. So that convexity is going to remain. If you can remove that convexity then you can still you can do a lot to improve your stability but if you don't improve a bad vector you're going to still have problems with instability. So what a trochleoplasty can provide congruity but it can't contain the patella. If you still have a bad patella you're going to have a bad vector you have trouble. So this type of a patient here where that patella sits laterally there's there's going to be issues with a vector pulling it sideways and you may need to do something with the tubercle or rotation or alignment. And here's a patient that I learned a lot from. So this is a patient three years out from a trochleoplasty. You see the pre and post sunrise views. I thought that the contour was fantastic. There's the MRI in the bottom. I thought that contour the trochlea looked absolutely beautiful but you can see where the tendon sits over to the side and this is what she came back with after three years. So this J sign returned. So what's the take-home message here? It's all about vectors. So if you look at the MRI on the right pre and post I've certainly done a great job at making that shape much more user friendly for the patella but her entire patella tendons is lateral. So the PT LTR number there which I encourage you guys to use is really way over the top. That should be no more than five and a half millimeters. So that vector is pulling it sideways. She also has significant valgus. I should have listened to Liza's talk first. So she has seven degrees of valgus plus she's got a huge PT LTR terrible vector pulling on this and so that's why this had problems later. And so for this patient we did a combined osteotomy and this is the order. First move the tubercle and then that's going to change your MPFL tension. So needed to revise the MPFL. I picked the point on the femur, placed a graft in the patella so I could confirm that point and then drilled across for the tunnel in the femur and placed the nitinol guide wire as well as a high-strength suture so I'd know where that tunnel is when I go then to create the osteotomy in the femur and put the plate on there. Then I could avoid that tunnel with my femoral osteotomy for an opening wedge DFO. Used a femoral head allograft and a wedge cut to fit in there to hold a correction and then as I'm placing the screws I can know when I'm going to bump into the potential graft for the MPFL because it'll tickle that nitinol wire or the pull-through suture and do something more than just an isolated MPFL. The big jumping J sign definitely need something more than isolated MPFL and a flat prominent spur may benefit from a trochleoplasty but it's really that convex shape which is a very small subset of these patients that needs a trochleoplasty and don't forget to correct the abnormal muscle vector. Thank you.

trochlear dysplasia

knee injuries

lateral x-ray

trochleoplasty

MPFL reconstruction