time for questions. I'd encourage anybody with questions to come up to the microphone and we'll start with Dr. Stewart with your first question. Yeah, great job, Scott. I think that the military cohort is always interesting because they're young and athletic people. My question to you, it seems obvious that under-correction, which means the operation wasn't successful, or re-operation would be associated with inferior skills, but why would younger age be a predictive factor of failure or medical separation? So one component of military duty, younger ages tend to have more kind of rigorous occupational demands, whereas some of the older military members may be more desk and headquarters related duties. So we think that may have some component related to it. The other aspect is getting later in a career. Some of these patients may persist and get towards retirement and not separate early as a younger patient may move on. Dr. Kasp? Jordan, great study. Difficult to do with any cadaveric study. Did you look at what the alignment of the cadavers was pre-surgery, or did you correct them to zero first? Yeah, that was part of our control. We looked at all the alignment. We excluded any that had any significant varus or valgus deformity. We didn't have a percentage of what we expected as a neutral state or a native state, but each specimen underwent both the femoral and the tibial studies, so we felt that that would control itself since you're comparing both osteotomy locations for each specimen. Question? Can we get his microphone on, please? Maybe I'm just not talking loud enough. Sorry. For Dr. Lyles as well, with your valgus correction osteotomy study, so in practice you'll see that there's often a combined deformity, right? So a little bit of valgus from the femur, a little bit from the tibia, and thou shalt not varus, right? So you try not to overcorrect that. So typically you wind up picking one. Do you think that your data would suggest that maybe we ought to chase both, right, so you can correct their deformity and provide increased unloading, or is that overkill? What would your take-home be from that? I think the study would suggest that if it is a normal or a native medial compartment and there's no significant degenerative changes there, I think it's safe to assume that an HDL would do a better job for minor deformity. If there's significant obliquity, which usually is femorally based, then I think it's very reasonable to consider multiple osteotomy locations. Thank you. Thank you. Bob Magnusson from Columbus, Ohio. In the study looking at the CT versus the MRI measurements of tibial slope, really interesting study. I wonder, did you consider at a lot of institutions the way sagittal MRI cuts are done are not true sagittals, but rather in the plane of the ACL, and I was wondering if that might introduce some bias into the comparison of CT versus MRI, given the slices may not be true sagittals. Yeah. I mean, the imaging that we used was whatever we had in our imaging database, which may not have been a true sagittal. Cool. Good to know. Always good to consider when you're looking at those types of studies. I have a question for Dr. Thatcher, too. So I think one challenge of measuring slope with MRI, as you saw, MRI to CT, but with that technique, is that the posterolateral impaction injury in and of itself can affect your measurement, right? If you get a pretty big impaction, that's your last point for your angle. And the bigger the impaction during the posterolateral plateau, the more energy is absorbed in that posterolateral side. Vis-a-vis, you may have more meniscal pathology. Did you guys look at the severity of posterolateral impaction injury as it correlates to that? Because I think the question is, what's the chicken and what's the egg? Is it the energy is so high, the meniscus tears, and they impact that lateral side? Do you think about it in that way? I think you bring up a good point. We didn't make any distinctions specifically for the posterolateral impaction, degree of posterolateral impaction that we saw on the MRIs. We excluded some MRIs for patients based on their quality, but we didn't do any assessment of the bony injury associated with the injuries themselves. Thank you. Dr. Stewart? Jordan, if it's a distal femoral osteotomy, why isn't it a proximal tibial osteotomy? Why is it a high tibial osteotomy? That's a good question. That semantic has always bothered me. I think it may have come from Mayo Clinic. Why don't we just talk about anatomy? So anyway, Ryan, if increased lateral posterior tibial slope increases the risk of a lateral meniscus tear, what's the clinical significance? Is it going to affect our repair rate success? Should we do something differently? Should we do a slope correcting osteotomy before we repair the meniscus? What's the clinical relevance? It's a great question. I think when you look at our study specifically and you look at acute ACLs, the clinical significance can be a little bit more challenging to identify. I think as we continue to expand our knowledge specifically of the interplay between posterior tibial slope and both ACL, meniscal and other ligamentous injury, having that knowledge can only empower us as we move forward. I think in terms of thinking about making corrective osteotomies for patients, I think that becomes a more challenging conversation because obviously you're inducing a lot of morbidity into your procedures for these patients. I have thought about doing something, a different study looking at specifically patients who have had revision ACL reconstructions and looking at the rates of meniscal injury in that population as a way of determining whether they would have benefited from a primary osteotomy. But as you can imagine, that's a very small cohort of patients and it would be challenging to control for what potential meniscal injury might have occurred at index injury. Thank you. We'll do time for one more question. What is your, the panel's take, it was very interesting talks, all of them. Since the body, the entire lower extremity has adapted to this slope of tibia from the moment of birth until the patient reached sexual maturity, what do you think would, may happen as a result of altering that to ankle, to hip, to lumbar spine? Is there any evidence that may suggest that altering the mechanics of knee may solve a problem somewhere but could potentially cause problems elsewhere? And that's the question I don't know the answer to. So I read the literature all over and I couldn't find the answer to it. So I'm just putting it out there for debate. I think it's a good question. I think, you know, the impacts of these realignments on the hip, the back, the ankle are unknown, as you said. My suspicion is none of your papers really address that specifically. So I'll tackle it. But I think it's a great question and probably something that's worthy of further study, unless you guys have other thoughts. Well, thank you guys. Excellent papers. It's great to, really great to see a lot of interest in osteotomy.

osteotomy

predictive factors

cadaver alignment

tibial slope measurement

meniscus pathology