Hello, my name is Daniel Green, and thank you for the invitation to speak today. My topic is on special considerations for MBFL with children with open growth plates. In the pediatric perspective, I'd like to try to talk about today is to review the role of implant-mediated guided growth, talk about MBFL, the zone of injury, and its relationship to the growth plate, and discuss MBFL reconstruction options. In terms of alignment, we all know that genuvalcum and extremes of femoral ataversion can contribute to patellar instability, and in our kids that are growing, I think it's very important to rule out pathologic genuvalcum. I try to get x-rays at all my kids that are pre-op for surgery, especially if there's any clinical evidence of genuvalcum, such as a space between the ankles when the knees are touching, and very aggressively recommend implant-mediated guided growth for any kids with genuvalcum that have more than two years remaining. Here's an extreme case of a child who had hyperphosphatidemic rickets, who was medically treated. You can see the cupping of the growth plates above the ankle, and the severe genuvalcum that we reconstructed the patellas in a staged fashion, first by using implant-mediated guided growth to correct the genuvalcum, and then proceeding with the soft tissue. What about the MPFL ligament in a standard sports injury situation after an acute patellar dislocation? Where does it get hurt? Where is it injured? Years ago, or not years ago, in 96 and 97, it was felt that the vast, vast, vast majority of these cases, the MPFL was injured off the femur, where subsequent MRI studies more recently have shown, especially in kids, that more of a majority is injured at the patella. Thus, I think this is one of the factors that contributes to the high failure rate of MPFL, or medial retinacular repair, in the setting. And here's just a couple kids from my practice, a 12-year-old with a first-time dislocator. And you can clearly see the complete avulsion, or disruption, of the MPFL off the patella. In the same week, I saw a 14-year-old, first-time dislocation. And you can clearly see that the MPFL is injured near its femoral insertion here. I think it's really hard to tell, in many cases, also where the zone of injury is. Maybe it's stretched without a complete tear. Or if someone has had multiple dislocations, scarred down and healed, scarred down and healed, the MRI radiologists have trouble locating the zone of injury. What about the growth plate? In a paper that we looked at kids, 43 scotally immature kids, we found that the average MPFL insertion site was just distal to the growth plate. And Lutel Ferro also demonstrated the same thing with anatomic specimens, 8 millimeters distal to the growth plate. And Dr. Shea has written three nice articles on this, with the anatomic specimens demonstrating that it was at or below the growth plate. The most recent study was in AJSM in 2018, really some elegant dissection studies, followed with CAT scans to look at where the dissectors felt the insertion point of the MPFL was. So in the majority of cases, it's very, very close and just distal to the growth plate. And here's a review of that literature. And then there was a recent literature review, also in AJSM in 2020, by Dr. Shea noticing the same. Proximal to distance, distal distance of the growth plate of the MPFL was distal to the physis with some noting variability. So that sets up our surgical reconstruction. My favorite way to do a MPFL reconstruction is a free hamstring graft. And I like to insert my femoral graft just distal to the growth plate. And if there's no chondropathology or no need for a lateral release, this could be done with some really nice cosmetic small incisions. The technique that I like to use, I did an arthroscopic technique article in 2013 that kind of goes through it step by step. My personal preference is to use hamstring autograft, which in the MPFL cases, I'll get one of the tendons from behind the knee. I just, it's cosmetically pleasing to me. When we do the trajectory for the MPFL socket, it has to account for the growth plate. So I like to get an AP image to first prove that I'm below the growth plate. And then the lateral image is going to check to make sure that I'm posterior enough or I'm in line of the radiographic landmark of shuttle. But the AP is important because if you just got the lateral, you might think you're in the growth plate. But due to the non-linear portion of the growth plate, you are not. But you have to confirm it on the AP. So this is the same patient, same guide wire. And I try to get as close to the growth plate as I can without disrupting it. Here's another example of using floral interop. And I just put this rebar over the guide wire just for helping an X-ray. And you can see on the lateral view, it looks like you're hitting the growth plate. But on the AP view, you're not. And then we have a double limb free graft that in the majority of cases, I'll go ahead and put two anchor sites into the patella and one in the distal fever just below the growth plate. What do we do with our acute patients who have large osteochondral fracture? Here's a 13-year-old fencer, first time dislocation. I think it's essential, if you're fixing the osteochondral fragment, to simultaneously fix or replace, that is, reconstruct the MPFL as well to prevent this from happening again. Here's that same patient with that large loose body. The loose body was coming from the femoral condyle here. And you can see that the growth plate's open. And here's two-year post-op. You can see the nice articular surface here where the old osteochondral fracture was. And on the coronal view, you can see the screw placement for our MPFL just below the scar of the physis, which is now closed. So is growth arrest possible after your MPFL surgery in children? It fortunately is very rare, but there have been case reports. This is a report out of Austria. Gerd Setlinger reported on this patient. And as you can see, there was a significant growth arrest requiring osteotomy, MPFL reconstruction, and TTO. So we do have to be careful and make sure you're using x-ray if you're making a distal femoral socket. A couple of studies, Nielitz out of Germany and out of our hospital, we've shown that this technique can be done safely. We reported post-operative x-rays and MRIs, or post-operative MRIs in 38 patients demonstrating no evidence of arrest. And here's some of the cases in that article. You can see where our insertion point is in relation to our growth plate. So we've talked about my preference for technique. I think one of the things about MPFL surgery, you're restoring cartilage. If you stick with the principles of restoring the cartilage or restoring the ligament using your anatomic landmarks of the femur and patella or distal quad, you're going to follow those principles. It doesn't matter so much the sequence or the fixation type. Other options, especially maybe perhaps for smaller kids or hypoplastic patella, you could insertion directly into the quad. And many surgeons now are doing one insertion point in the patella and one in the quad. As it's been shown anatomically, that the MPFL ligament does anatomically send fibers into the distal quad tendon as well. And Miho Tadaka has done some nice, and Dr. Fogerson, some nice anatomic studies on that. In a weak bone or for some surgeons desire to avoid bony fixation in the immature patient, you can loop the MPFL around the adductor tendon. And this has been described by Salipa and Art and by Gomez. And then Dr. Salipa also has described using part of the adductor tendon itself as the MPFL graft. So he's open exposure of two-thirds, three-quarters of the adductor tendon, which he splits and then brings over to the patella, forming a fissile-sparing MPFL reconstruction. Dr. Henricus and others have described taking a small sliver of the quad tendon itself and making an MPFL. So there's a lot of ways to restore collagen and make a reconstruction MPFL. I'd like to talk for a second about the unique type of pediatric patella dislocation that you may see, more likely to see in the pediatric clinics than you are in the adult clinic. And that's the obligatory dislocation or the fixed lateral dislocation type. Obligatory dislocation flexion, like you can see here, is the kneecap dislocates laterally. Every time the child flexes the knee, it's obliged to dislocate and flexion. If you tried to hold the kneecap anteriorly in the trochlea, you wouldn't be able to. And note how it reduces in extension. When you see this case, in addition to doing an MPFL surgery, you'll need to do a massive or large lateral release, and you need to be prepared to do a quad tendon lengthening. After doing a lateral release, it's not the typical lateral release. It's down to the joint line, and it's up to the vastus lateralis tendon. And typically, the vastus lateralis tendon needs to be released as well. And this could be done by releasing the tendon from the patella, releasing it from the quad, and releasing it from any lateral attachments. Then later in the case, you can reattach the tendon higher up in the quad in a lengthened position. Once you've done the extensive lateral release and the vastus lateralis tendon lengthening, about half the cases will no longer dislocate inflection. If that's the case, then you proceed to your MPFL reconstruction. If that's not the case and it still dislocates inflection, then a formal lengthening of the quad tendon itself, the rectus and intermedius, need to be done. I like to do that with a Z lengthening, although others have reported good success with a V-Y lengthening, like shown here. And here's a little video of me performing a Z lengthening in a patient with obligatory dislocation inflection. I've already completely detached the vastus lateralis tendon from the quad. You can see that. That's what the clamp is held on to. We'll reattach that later. And now we're doing a formal Z. Notice how I'm releasing the lateral part of the quad tendon from the superior lateral patella, thus improving the pull of the remaining quad tendon will be more medially. It'll have more of a medial pull and less of a lateral vector. So I've done the first limb here. And now we'll do the second limb. And we usually reattach this under some tension in about 60 degrees of knee flexion. So whenever we see these obligatory patella dislocation inflection, we're prepared to do our quad lengthening, and we tend to always release the vastus lateralis, the large lateral release, and be prepared to lengthen the quad tendon itself. In about 50% of the cases, they did an MBFL, and we have a low threshold to do a distal re-alignment. So what we've talked about today is the role of implant media guided growth, MBFL zone of injury, MBFL anatomy, reconstruction options, and highlighted the importance of being aware of obligatory and fixed patella dislocations and their need to do a quad lengthening in many cases. Thank you very much for your attention.

MBFL issues

implant-mediated guided growth

MPFL reconstruction options

pathologic genu valgum

obligatory patella dislocation