present in this great session, present our research. Here's our disclosures. So this, everybody in this room knows about the trochlea dysplasia, patella alta, genia valgum, TTTG, and femoral antiversion really associated with patella instability. And there's been some great work by Rene Attal and Phil Schottel, also with the femoral antiversion, that torsional internal rotation of the femur being at a risk or leading to patella instability. There's little written on actual rotation within the joint, the rotation within the joint between the femur and the tibia. One of the first articles I saw on this was presented here at AUSSM and also our Pediatric Research Society by Jeff Nepple and his group at Wash U. And they showed, looking at MRIs, that in pediatric patients with patella instability, there was an increased interarticular external rotation of the tibia in relation to the femur of over seven degrees. So we wanted to look at a very similar study. We wanted to look at normals versus our regular patella instability group. But we also had a severe patella instability group that we defined as either patients with fixed lateral dislocations or obligatory dislocation inflections. So looking at the three different groups, we also found a difference in the rotation within the joint between the femur and the tibia. Statistically significant versus control was our standard patella instability group. And more impressively was our severe group that was either fixed or obligatory dislocation had much more rotation through the joint. And here you can see what's happening kind of clinically or functionally. An extreme case of this child with nail patella syndrome, you just look at the AP of the knee and it's rotatory subluxation combined with the patella dislocation. It's not just the patella, it's there's a 3D deformity through the joint. Here's a similar, a different case, an eight-year-old with Down syndrome, fixed lateral dislocation. You can imagine the powerful quadriceps going into the patella, inserting on the laterally deviated tibial tubercle, causing rotation of the proximal tibia. And this child had a rotational deformity of 24 degrees. So we wanted to ask, does interarticular tibiofemoral rotation change after we reconstruct the patella stability? So we found postoperative patient, we had to find patients with preop MRIs and postop MRIs. And we found 14 with the fixed or obligatory dislocation group and 16 with the standard patella instability group. The posterior chondral line was measured at the widest AP axial image, and the posterior tibial line was measured at the level of the PCL insertion. There were three blinded measures for these measurements. They had excellent ICC, and we measured TTTG and the rotation. Demographics, these children were 13 to 14 years of age, and the postop MRI was about two years after the index surgery. And we found a significant improvement in the external tibiofemoral rotation in the obligatory and dislocated group of over five degrees. And that led to an apparent decrease in TTTG for the patients who didn't have a tibial tubercle osteotomy. We didn't see any significant change in rotation in our standard patella instability group. So you can see the statistically significant improvement of the rotation on postop MRIs in our fixed obligatory dislocation group. Obviously, limitations are that this measurement is only statically done in an MRI. We don't really have a dynamic measure. But we can conclude, you know, this study's really the first to show that MPFL reconstruction or patella realignment can change interarticular tibiofemoral rotation in severe cases of pediatric patella instability. We also remind people that this rotation through the joint can affect the TTTG measurements. And this has been shown previously by some nice work in Cleveland by Bradley Smith and others that showed that for each one degree of tibial external rotation through the joint, the TTTG increases about 0.5 millimeters. This is their data. So here's just a case in the OR. You can see just a patella instability patient, a teenager, with a little internal movement with the knee flexed at 90. There's marked apparent improvement of the Q angle just by manipulating rotation. And here's that case I showed you earlier with the tibiofemoral subluxation. You can see on this coronal view here the beautiful articular surface of the lateral femoral condyle, but there's not even a tibia articular surface below it. It's subluxed. And we were able to treat this with a staged approach, correcting some of the structural valgus with implant-mediated guided growth, and then a lateral release quad lengthened in tibiotubercle and MPFL. And by getting the powerful quad back into the front of the knee, we were able to improve the rotation. Thank you very much. Thank you.

interarticular tibiofemoral rotation

patella instability

severe group

MPFL reconstruction

pediatric patella instability