Hello, this is Jeffrey Kneppel from Washington University in St. Louis presenting distal realignment options and pediatric patellar instability with a focus on the medial patellar tendon transfer. Here are my disclosures. Recurrent developmental patellar instability presenting in young children can be very challenging to treat because it is often associated with significant underlying deformity. This can be fixed, obligate, habitual, recurrent, extension, or patellar-based. You can see all the different varieties of young and older patients here with fairly severe issues, extension-based on the left, flexion-based instability on the right. We know the younger the patient, the more severe the underlying deformity, and the limited realignment options distally really make this a challenging to treat without a distal option. Here is a typical patient, an 8-year-old female, you can see as she extends, a jumping J sign there as her patella dislocates. You can see the MRI demonstrating that, while a merchant view will look pretty good here because it is reduced in the 30 to 45-degree range. Distal realignment options can be a variety of options out there. Many of these severe deformities are not going to be treated with MPFL alone adequately. It is just going to stretch out. Non-anatomic options, the Ruh-Golth weight, transferring half of the patellar tendon medially or modifications of that is sort of marginal in the literature. Not a lot of success. Similarly, the Galiazzi procedure, taking the hamstrings, rerouting those up to the patella, are similarly anatomic and have not had great success in the literature. More anatomic options in skeletally mature individuals, we do a tibial-tubercle osteotomy. You can certainly do this as they are approaching skeletal maturity, but not an option in our young patients. The medial patellar tendon transfer gives us a powerful tool to do this realignment safely, and I will show you that. Other options include variations like the Grimont procedure where it is a periosteal sleeve that is moved, but maybe not as powerful to move it as far. We have done patellar tendon transfers here in St. Louis for over 40 years, Perry Schoenecker really the pioneer on this. This has been published in several iterations with more coming out. Most of these patients are under 10, maybe bumping it up to 11 in a male. We do a complete transfer of the patellar tendon with associated large VMO advancement and extensive lateral release. This is a typical patient, 8-year-old, with lateral extension-based instability. You can see the kneecaps on the edge of dislocating there on those merchant view. Under anesthesia, very easily dislocatable patella with just a little bit of pressure. We are going to do this procedure through a standard midline incision from the superior pole of the patella down to the tibial tubercle. We expose the skin flaps to see the VMO there. This is sort of going to be our exposure for the medially for VMO advancement, laterally for the release. Here is the lateral release. We really want to do an extensive release here up to the superior pole of the patella, but then also looking for aberrant bands proximally to detether the quad from the IT band and underlying quadriceps. The medial side, we are going to release for an extensive VMO advancement. Then we start to get ready to go distally. We are going to tunnel behind the patellar tendon to isolate the insertion. There are dots on our insertion. We are going to sharply take off about a two centimeter footprint of the patellar tendon. We do this with a 15 blade. We are taking care not to injure the underlying apophysis, sort of teasing this up over time. Then we are going to move this over typically 75, sometimes 100% of the width of the tendon and sew it back into the bone with strong ethabond or fiber wire type sutures. This goes into the bone in our new location. I prefer to use like a crack out type unlocked configuration to have a few throws up the tendon and then come back down. We use one of these sutures on the medial portion of the tendon, one on the lateral portion of the tendon. They are going back through the bone. Now we are moving that second strand similarly through bone medially. You have the PEZ insertion for a little more soft tissue support. There is our realignment ready to sew this down. We will check the tension of this to ensure this seems to be adequate. If you are off, you can always take the sutures out, pass them through bone more medially. We are not attempting to distillize the tendon here. You might get a little bit of that inadvertently, but not trying to put too much tension on the system to risk the healing. We sew those in. We will often put some reinforcing stitches on the side as well to further reinforce the new footprint of this. Now we can take this up to ensure we can get to 90 degrees of flexion. Flexion-based instability, quad tightness gets in the way and you may have to perform additional things like VY lengthening approximately. Once we are happy with that, we are going to do a big VMO advancement, putting the VMO back in appropriate position for the new position of the patella there. Sometimes in a very young patient, this will come most of the way across the patella. This is maybe a more typical eight-year-old. With that on, that seems to be tracking very well. And then laterally, we have released any tight bands, so we will close there and let that patient heal. We keep these patients in a cast for usually four to five weeks postoperatively, then starting range of motion in a hinged knee brace. At this age, they recover remarkably. Here is postoperative x-rays after this procedure. The patella looks much better centered. We have not changed the patellar height. Here is what we see clinically. In a more severe case, the quadriceps lengthening may be required in inflection-based instability like you see here. I will not go into that in detail, but a VY lengthening works very well in that setting as well. Outcomes, we have looked at more recently our outcomes here. About 50 of these, no ruptures, 3% complication rate, subsequent surgery and only about 6%, and then surgery at maturity and about 10%. In many patients, this is not a temporary option if you get this right. Only 11% reported any kind of subluxation, none had dislocations, and this is a highly functioning group, most of them doing sports. Here we are back to that original patient, so again, pre-op, a major sort of jumping J sign as she goes into extension and she is hesitant to fully extend her knee. After this has been realigned, no hesitation here, full extension, no movement of the patella. Three months post-op, this is a typical sort of cautious patient, she is walking well but maybe a little cautious. Here is a male who is less cautious. He is already running at three months, which is testament to how quickly these younger patients recover. Pre- and post-op MRI shown here showing how important this can be to get this patella back in the groove. This is something that is going to get worse over time without treatment rather than getting better, so we can really avoid major problems down the road by getting the patella in, especially if you do this at a young age. Here we can see remodeling of the trochlea and a more appropriate patellar height at final healed stage in this individual's knee. Medial patellar tendon transfer for me is my primary mode of distal realignment in the scaly immature patient. Again, we are using this up to the 10 to maybe 11-year-old age in males in the setting of severe deformity where an MPFL alone is unlikely to solve the underlying issues. This has been a very reliable approach for us with healing without issues if you follow the post-operative protocol and rehabilitation outlined here. Thanks for your time.

Jeffrey Kneppel

Washington University in St. Louis

distal realignment

pediatric patellar instability

medial patellar tendon transfer