Thank you, Liza and everybody here. I'm always humbled to be on such a great panel with all the other faculty as well. So these are my disclosures, not relevant for this talk. Here are my objectives for this talk. So when performing opening wedge osteotomies, really the far cortex or hinge acts as a fulcrum and is an important biomechanical stabilizer when you're doing these techniques and with most of our plates designed. When hinge fractures do occur, they can lead to instability at the osteotomy, loss of correction, and then lead on to delayed or nonunion. So this is a pretty good systematic review that just came out this past year. I like this figure a lot. It's a little busy here, but what they're saying is they were able to identify the hinge fractures on only about 9 to 19% of intraoperative fluoro or immediate postoperative X-ray, whereas when they were getting postoperative CT scans, you can see they were identifying significantly more hinge fractures. So really these are occurring a lot more frequently than any of us realize, and a lot of these authors in these papers are by excellent, well-trained, and very busy osteotomy surgeons. So some technical pearls for recognizing a hinge fracture, have a high index of suspicion when you're doing larger corrections, or you feel a sudden loss or that sudden pop during the opening wedge, and obviously carefully evaluating your intraoperative fluoroscopy. Here on this one, you can see that one pretty clearly. So these are classified based off of this paper from 2012. So basically a type 1 hinge fracture is an extension of the osteotomy straight into the proximal tibiofibular joint, and it's important to know that because the joint capsule and the ligaments around this joint do provide a lot of stability when that occurs, whereas a type 2 fracture occurs below the proximal tibiofib joint, and really this can be unstable. A lot of stress can accumulate at that proximal fibula and actually externally rotate your proximal portion of the osteotomy as you're opening it, leading to malreduction. And then your type 3s are when it comes up into the joint, which can obviously be a problem if you have any intraarticular step-off. So a lot of key points when you're treating these hinge fractures is prevention. How do we prevent these, or how can we use our techniques to minimize this from happening or minimize the detrimental effects? This is a good paper. In 2017, they looked at 111 patients with a medial opening wedge osteotomy. They had 22 hinge fractures on postoperative CT, and looking at the location that was the safest or minimizing the number of hinge fractures, they identified this WLL zone or within the proximal tibiofib joint and lateral to the medial margin as the lowest rate of hinge fractures in their study. Another technique pearl is using a biplanar osteotomy. This was a biomechanical study where they allowed greater opening of the medial gap before hinge fracture occurred. And there's other advantages that have been previously published on biplanar osteotomies that it increases the torsional stability of your osteotomy construct, especially in the presence of a hinge fracture, and there's increased bone surface area for bone-to-bone healing. The opening gap distance is another important factor. This is back to our systematic review. So eight studies that have reported on the opening gap. The hinge fracture group of about 11 to 12 millimeters was the mean opening gap with the hinge fractures versus a 9.9 to 11. And then this other paper identified a gap greater than 11 millimeters as a significant factor with an odds ratio of 4.9. So what can we do, other techniques to help prevent this? So this is a patient-specific cutting guide. They published both their cadaveric study and their clinical study. So using a K-wire through the guide that they demonstrated they could get a much higher opening before gap, before fracture, 19.8 versus 7 millimeters in their cadaver study. And then in their matched case control study, they had a much lower rate of hinge fractures in their K-wire group versus their non-K-wire group. Other considerations. These are a couple of older studies, but using a locking compression plate design really provided significantly more stability and allowed for appropriate axial and torsional stability that you can enable early weight bearing. They also recommended additional fixation using these older four-hole non-locking plates. And plank length was also shown to provide much better stability in the presence of a lateral hinge fracture. Other considerations. So using a pilot hole. So several finite element analysis studies have showed that these do reduce strain at the osteotomy or hinge site. Although Dr. Getgood's study was a cadaveric study where really they showed no difference in the strain or reducing the risk of hinge fracture. So how do we treat these? So what now? And we know how to recognize, we know how to prevent, but they will occur as we know from that systematic review. So type 1 fractures that occur into the proximal tib-fib joint, these are generally stable. So I like using this locking compression plate technique. You place your locking screws proximally first and then you place that non-locking screw distal to the osteotomy. I really like this figure from this paper that shows that force vector compressing that hinge. And so that's typically how I do it. Normally they follow my normal post-operative rehab protocol. I typically keep them touchdown or non-weight bearing for two weeks and then I progress them pretty quickly, 50% between two to four weeks. And as long as they're not having pain or doing well, we'll get them off crutches around six weeks. What about for our type 2 fractures? Again, really there's a higher risk of a mal reduction. So you want to keep a close eye on your osteotomy and your intraoperative florals. I like having the biplanar technique because you can really see if there's any change in that retro tubercular cut, if it's rotating at all, or if you end up with a big gap there, you know that something's gone wrong. And so that's why I always use a biplanar technique for one of the many reasons. And then again, I use the locking compression plate here. And for these, I do delay their weight bearing. I want to get x-rays at a couple of weeks, make sure everything's looking good. We start 25% until about six weeks. We'll get more x-rays. As long as everything's looking good, we'll let them start kind of weaning off the crutches at that time. And then our type 3 fractures. So really the risk here is an intra-articular step off. So I like this technique that they showed in this paper by Lee and Lee, adding two additional lag screws across the tibial plateau with a small two-hole plate. And then again, so these, I'm definitely delaying their weight bearing, typically until about six, eight weeks. Then we'll let them start progressing off their crutches. What about the distal femur? So there's really not much published on the distal femur regarding opening wedge and medial hinge fractures. But this is a very good paper published last year where they evaluated 100 patients that had 46 medial hinge fractures and classified them very similar to the tibial osteotomy classification. And they identified the ideal hinge position at or distal to the adductor tubercle, which I think is a lot lower, a little bit lower than traditional opening wedge distal femur osteotomies. And this is where I try to go. So again, there's not really much out there. So I have a few cases to illustrate the treatment of these for the distal femur. So the first case is a 30-year-old female, lateral joint pain, valgus, previous meniscectomy, pretty big valgus knee. We templated for about a 13 millimeter correction. So I was concerned, you know, we might get a hinge fracture in this case. Indeed, we did. So I see a hinge fracture here. We liked our correction that we were checking intraoperatively. So remember our principles. We used a nice biplanar technique with a big anterior flange. We used our locking compression plate, put our screws in distally, put our compression screw in. Really, you can't even see that hinge fracture on that intraoperative fluoro. And so she followed our normal postoperative rehab protocol, touched down weight bearing for a couple weeks, progressed to 50%, and weight bearing is tolerated around six weeks. And she did very, very well. So what about this case? So this was a 38-year-old female, again, valgus knee, lateral joint pain. This was actually a custom plate that I was trialing. It does use locking screws and has a similar compression screw above the osteotomy. Shorter working length of this plate and not quite as robust as the plate I typically use. You can't really see the hinge fracture here, but trust me, it's there. Fortunately or unfortunately, they didn't save my fluoro when I was assessing the stability there and I could gap that medial side open about a centimeter. So I thought that this needed some additional fixation. Really, I was concerned about this plate. I'm not, again, it's a new plate that I'm not as familiar with. So we opened up, we did this 2-7 locking T-plate, put the distal locking screws in and two compression screws approximately. I was really happy with the stability at that point. So two weeks post-op, our x-rays look great, feeling pretty good about ourselves, high fiving. Six weeks later, she comes back. So we let her start doing some touchdown weight bearing, doing our normal 50%. Six weeks later, she comes back, the screws backing out. We see a lot of either callus formation there medially or maybe that's the hinge fracture. A lot of callus around our biplanar osteotomy, which I don't typically see that with our more stable fixation. So we got a CT scan, really not much healing at all at the osteotomy. You can see this hinge fracture. She maybe is collapsing into varus a bit. So we went back to crutches. We talked about revising everything. We didn't want to do that. So we went back to crutches, touchdown weight bearing, got her a bone stimulator. You know, there's not really good evidence to support that, but we thought anything we could do to help her heal, vitamin D, high dose of vitamin D supplementation. And so she was very good about her using the crutches and staying off of it. And she came back, this was just a couple of weeks ago at her four-month post-op, x-rays look pretty good and she's pretty happy with how she's feeling now and now off of crutches. So key points here, I think prevention is the key, or at least minimizing the detrimental effects with our techniques, having an appropriate hinge position, completing the anterior and posterior cortical cuts using a thin flexible osteotome is what I like to use, a biplanar technique for both the distal femur and the proximal tibia. And if you're doing a case with a larger gap, that Winkler paper, their actually group, a DFO of greater than seven millimeters was their hinge fracture group. So really it's not a lot out there, but that's what we got to go on. So a greater than seven millimeter gap, consider prophylactic K-wire during opening, or make sure you have that larger locking compression plate as an option if you're using some of the other implants. So again, the treatment for the locking compression plate for our type ones, and then delaying weight bearing for our type two and our type three, I'll consider additional fixation. I do have a little time, I have one more case. Perfect. So this is a one more case here. So this is a gentleman, again, a big correction I planned for here, templated about 18 millimeters. So for this kind of case, I will prophylactically put a staple there, you know, just knowing that we're probably going to get a hinge fracture instead of a K-wire, I like doing this. And so, and I did a distal biplanar cut, I cringe looking at that last fluoro there, I do more of a flat straight all the way down osteotomy now, I don't want to try to avoid this dreaded black line. But he did very well, and this is a six month post-op x-rays, and he's doing very good. So if you know you have these big corrections, think about doing some lateral prophylactic fixation, and again, using our larger plates. That's all I got, thank you. Just wanted to remind the audience that we are, sorry, you can clap. Just wanted to remind the audience that we are using the app, and some of the more general questions we'll save for the end. So Robbie, when do you use a fill-in, and do you think that the stiffness of the fill-in has any contribution to the overall construct, and even the failure issues? So at 10 millimeters or more, I use a wedge of allograft bone that I'll hand cut in the OR. So that's typically what I use, I know that's expensive, but I think it provides a lot of stability, you can really compress that distal non-locking screw, so that's what I like to do. Other question is, do you think that the speed in which you open the osteotomy has any contribution to the hinge? Certainly, and we know from our stress-strain curves and our modulus of elasticity, if you lower the rate at which you're opening that bone, you can certainly reduce the risk of fracture there. I try to go really slow, a lot of times I'll do a stacked osteotome technique, and let that kind of sit and relax for a little while before I'll go ahead and open it all the way. Another sort of more general question, there does seem to be a somewhat female predominance of the failure rate on distal femoral osteotomies when they're opening wedges, yes, distal femoral osteotomies. However, there's also more females with valgus knees, so it may be more a contribution of the denominator, but it's possible that osteopenia plays a role. Do you do any thought process if you're doing a 30 to 40 year old female, or anybody for that matter, but thinking about the bone health before you do an opening wedge osteotomy, particularly on the femur? I don't do anything specific, but that's a very good point. In Ohio, we have a lot of vitamin D deficiency, I do put pretty much all of my osteotomy patients on vitamin D after surgery, I don't check it, we just do that if they're not taking it already. I guess that's one additional pearl. Great. Thanks, Robbie. Thank you. I think while we switch over, I think the other thing to consider, Liza, with that is also smoking, and I think a lot of these patients you can also address distal femoral osteotomies with a medial closing wedge, which will then, may be able to get over some of those issues. So it's my great pleasure to introduce Seth Sherman.

hinge fractures

opening wedge osteotomies

instability

systematic review

prevention