I'm going to be talking about tibial slope as it relates to ACL. And at first I get a little freaked out when you hear about slope, kind of like my youngest in that picture right there, but hopefully by the end we'll all have a better understanding of tibial slope and how it relates to ACL injury, and when we should correct tibial slope and how we achieve that goal. So it sounds easy enough. Tibial slope is basically how flat or steep the proximal tibia is. Normal proximal tibial slope is about 7 to 9 degrees. However, it gets a little bit more confusing because there's a lot of different ways to measure tibial slope. Can you do that on a standard knee radiograph, or do you really need a full-length tibia? In 2014, one of the studies showed that just using standard radiographs, it might overestimate the slope by roughly 3 degrees. However in 2021, they did another study showing that if you get at least 15 centimeters of tibia on your knee radiograph, it's equivalent to a full-length tibia. Either way, you definitely want to make sure you get a true lateral because your measurements will definitely be off if it's a bad x-ray. Again, multiple ways to measure. I think the more reproducible one is the one on the left, the midpoint method. But a circle method was also adopted in roughly 2009. Either way is acceptable. You just have to be consistent. But it gets even more confusing. Does it matter if you're measuring medial or lateral tibial slope in general? According to these two studies, medial tibial slope is a little bit larger, but the lateral tibial slope might be a higher risk for ACL injury because it increases internal rotation and stress on the ACL. So again, it gets a little bit confusing. Medial tibial slope might be more reproducible because it's easier to measure on x-ray. However, it might make your tibial slope value a little bit larger. Either way is acceptable, but just be consistent. So why does this matter? Well, in 1994, Dr. Dujour published a study. For every 10-degree increase in tibial slope, there's a 6-millimeter increase in just resting intertibial translation. So it definitely increases stress on the ACL. There's a review article in the Yellow Journal last year, which this diagram came from. And I think it's helpful just to conceptualize that the boulder is really the femur. The man behind the boulder is the ACL, and the hill is the tibial slope. And you can see on the left, in a normal state, not much stress on the ACL. However, that picture on the three in from the right, where it's a really increased slope, you know, the guy's squashed. So it really puts a lot more stress on the ACL. The veterinarians actually figured this out a lot earlier than we did. Right now, about half of the dogs that tear their ACL get an ACL reconstruction, but the other half get a tibial plateau leveling osteotomy. And you can see it from the pictogram on the right and then radiographically on the left. And that's all they need. They don't get an ACL. They just get this surgery. Coming back to humans, biomechanically, Dr. LaPrade published a study where he basically hooked it all up in his biomechanics lab and showed that there's a direct linear relationship between slope and ACL graft forces, as you can see from this scatter plot here. Well, translating it biomechanically to the real world, in 2006, this was one of the first studies to show that there's an actual increased risk of injury. They took 100 ACL patients on 100 controls, and the tibial slope in the ACL injured patients was 11 versus 8.5. And in the ones that did tear their ACL, the ones with a higher grade pivot shift had a higher tibial slope as well. Again, another study, 2019, 245 athletes, the tibial slope was, again, they looked at lateral tibial slope, 9.5 degrees versus only 5.6 in the healthy controls, and it didn't matter what the mechanism of injury was. Two more studies, one in 2010, kind of the same thing, 54 patients. Interestingly enough, the medial tibial plateau was the same, but the lateral tibial plateau was increased. And a 2017 meta-analysis showed the same findings. There's an increased risk of native ACL injury. Well, when we're talking about the ACL graft, the kind of same findings hold true. 2018, there was 200 primary hamstring auto-ACL reconstruction patients, and they found that a tibial slope of 12 degrees or more was the single strongest predictor of repeat ACL injury. That combined with young age was terrible. When it was an adolescent with a slope greater than 12 degrees, at final follow-up, only 22% of those grafts were still intact. Similar findings in 2015, you can see here in the ACL failure group, 8.4 degree slope versus only 6.5 in the control. Another one in 2013, 200 primary ACLs. Again, this is kind of where the 12 degrees number comes into play from all these studies, but 12.9 was the failure group, and they actually showed that it had a 59% increase or risk factor of 5 when the slope was over 12 for a repeat ACL injury. Dr. Musallan, just this year, published on 102 revision ACL reconstruction patients. 58 of them, it was their first revision. 44, they had multiple failures, and the multiple failure group, you can see here, 12 degree slope versus only 9 for the single failure group. Similar findings, Dr. LaPrade, this year, systematic review. You can see the slope values, 9.5 for the ones that failed versus the primary injury, and 7 versus 5.6 for an intact ACL. Another systematic review this year, there's over 20 studies, over 5,000 patients. Fifteen of those studies showed an increased tibial slope was directly related to ACL failure. However, they had a lot of disagreement, and again, it goes back to what I showed in the beginning. There's a lot of different ways to measure slopes, so the absolute value was all over the place, and it ranged from 7 to 17 degrees. However, the trend was true, that the increased slope increased the risk of ACL injury. Interestingly enough, too, we kind of touched on it before, but tibial slope seems to be a risk factor for ACL injury, but also other injuries in the knee, too. There's an increased risk of root and ramp tears when the tibial slope is elevated as well. So we kind of know why it's important, but how do we correct it, and when should we correct it? We don't really know. This, again, is that review article with that bolder picture. If anyone's interested, I think it's a good, concise summary of all these points, but they really outline it well, too. The indications are still evolving. We just don't have that much data on slope-correcting osteotomies. In general, I think it's something to consider in the revision setting, and the slope is greater than 12 degrees. What I wanted to highlight on here is some of the contraindications, though. PCL deficiency, if you correct the slope, you're going to make that worse. A flat slope is not good for PCL injuries, so you have to watch that, and if they have a lot of arthritis, too. Knee hyperextension is also a relative contraindication, because when you do the anterior closing wedge osteotomy, you're actually going to increase the recurve bottoms, so something to think about. So, again, we don't really know when we should do it, but how should we do it? We're still working on that, too. I think we're getting better at it, but it's through an anterior closing wedge osteotomy. Multiple different ways of doing it. It's generally divided up into where you make the osteotomy cut, above, through, or below the tubercle, and that influences how you fix it. There's multiple ways to do it, either staples, screws, plates if you're going below the tubercle. There's pluses and minuses to all three of them, and this is, again, kind of a radiograph of where you're going to make that cut. I just think it's important to consider, no matter how you do it, you're trying to achieve a couple goals of correcting to neutral. You don't want to overcorrect, because then, again, you might place a little bit of extra stress on the PCL. In general, for every millimeter of anterior tibial bone that you've removed, that correlates to about one degree of slope correction. I think other things to consider, again, not just how to do it, but when you're doing it, do you want to do this in one stage or two? Some people, I know it's harder on the patient when you have to break it up, but if you're trying to do it all in one setting and trying to do the definitive revision ACL, you have to think about, all right, how are you going to pass your graft? What you don't want to do is get through all the osteotomy stuff, and then you have to pass your graft, and one of these staples is sticking right in your tunnel, and you can't pass the graft. I think just something to plan out, and I think if you're doing one, definitely practice in a cadaver first. Don't do this for the first time on a real patient. Again, this is from that review article, just some pearls and pitfalls. Again, for about every millimeter of bone, it equates to about one degree of slope correction. I think some of the other important things, there's a lot on this slide, but some of the other stuff, go slow. You don't want to just do your osteotomy and then try to straighten them out, crack it, because then you'll crack out the back of the tibia, so you really want to allow for that stress relaxation and keep that posterior cortex intact. This is a quick video of Dr. LaPrade, his technique. I mean, again, I think you have to adopt one that works for you. Tibial tubercle preserving, anterior closing width. I'll just highlight some of this stuff, but he's doing this in the setting of bone graft in the old tunnels, so again, you have to think if you want to do this one stage or two stages. This isn't a small procedure. I think you really need to get good exposure of the whole tibia, so don't try to do this through a minimal incision. You really need to visualize the entire tibia. You need to, here, kind of showing the bone grafting of the tunnels, you definitely want to put in some Z retractors or just retractors underneath the patellar tendon. Again, you have to figure out which way you want to do it, above or through the tubercle. This one's above the tubercle, and here he's putting the K wires in. This is really what's setting up your osteotomy cut. There's no real guide available, so these K wires are really what's guiding your, it's how you're going to cut. And it's also the distance between the two at the cortex is what correction you're going to do. How much bone you're taking out, see, that's the degree of slope correction that you're going to achieve. Again, you want to do this with fluoro too. I would not do this freehand. I think you really need to have intraoperative fluoroscopy to do these well. You want to start the cut with the saw, but then really that's about it. I think the rest you really do with osteotomes, and a lot of times just scoop it out of the bone with a curette here. You don't really want to be, you know, jamming a big saw in the back of the knee. There's nothing to protect you in the back besides those K wires. So again, that's kind of how you do it. How do they do after you've fixed it? Well, we really don't know. There's only two studies. The first one, only nine patients, and it was in the re-revision setting. They reported everyone did pretty well, but again, it was only nine patients. The slope went from 13 degrees to 4 degrees. No complications. They all had stable knees. And the authors, they recommended to consider it if the slope was greater than 12 degrees. The other study, again, only five patients. So all of this stuff that we're talking about, we only have really 14 patients to go on. We don't really have much data yet, but, you know, similarly, they did pretty well too. They all corrected the slope, didn't overcorrect, and their laxity definitely improved after the correction. So again, in summary, I think there's a lot of different ways to measure slope. I think just be consistent, adopt a measurement technique that you feel comfortable with doing in your clinic. I think the data is pretty clear that a slope greater than 12 degrees does have a risk for ACL injury, but we're just still not really sure what do we do with that information. I don't think it's a, you know, one size fits all. I think everyone's individual. When you're looking at, particularly in the revision setting, I think take some of the other points from this ICL into consideration, whether that's doing a closing wedge or is adding an LET. I think you have to take, you know, each patient individually and see what works best for them. And I definitely recommend practicing in a cadaver first because it's a little nerve-wracking without a guide like we're used to with, you know, definitely the ACL and the other osteotomies like HTL. I think it's different. With this one, you just have K-wires, so definitely practice in a cadaver first. Thanks. Are there any audience questions for Dr. Cain? Dr. Brown. We do a lot of these. We have unique... patient population in the Middle East, we call it the Arab knee, they have increased tibial slope, the average tibial slope in my Emirati patients is 12, so if I use the 12 to cut off, I can't obviously, and a couple things that we use to help on the x-ray, when you measure your slope, get the single leg monopodal stance, and that really helps you and have the patient fire their quadriceps, and you'll see the anterior tibial translation, that to me, increased anterior tibial translation, plus the slope is what I kind of use for indication. If you see 12 millimeters of anterior translation, and a slope of 14, 16 degrees, then you're pretty much locked into it. If you've got to do big corrections, it's much easier and safer to take off the tubercle. And I would say, if you've never done one, it might, you know, I agree with you, practice only could ever, but it's a lot easier if you take the tubercle off and you put it back on. If you have to do a revision, then you're locked into a quad tendon graft. Quad tendon, and that doesn't violate the tibial tuberosity. And it's amazing what the slope, just sometimes the slope correction will do on your anterior translation. You can take a post-op x-ray and you'll see that. So those are the, I think, the tips I would give to you guys on doing that. That single leg monopolar, take that x-ray. That's a really valuable x-ray. Teach your technicians to do it. And you'll start to see these knees. And if you get a patient from the Middle East, look at the slope, because you'll see it sometime. So those are the things that we do. Or send them back to the Middle East. No, no, no. We have enough. We have enough. We've got experience here. Now, Dr. Brown, are you doing that in the primary setting very often, or is it typically in your revision patients? It's typically revision. Occasional primary. And if you get a guy on a slope of 20, an anterior translation of 15, I don't think any ACL grad is going to survive that. So you have to have that conversation when you're going to stage it or whatever. But that's, and they don't like it. They come in, they think they're getting an ACL, and they look at you. You're going to break my leg? But you have to explain and show them. And it helps if you have some x-rays. Say, well, look, this was the guy before. Now look at him. Did the slope change? And then they kind of come around to it. But primarily revision. And also on the recurve arm, for us, that's not a contraindication. You will get the hyperextension. But what you can do is you do your inside-out meniscus repair incision. You take the POL off, and you do a POL advancement. And just like when you're doing your medial side, you always say tension it in full extension and not in flexion. So you tension it in a little bit of flexion, and you can test it on the table, and you can block the hyperextension. And you put him in a brace for six weeks, no hyperextension. And so you can minimize the hyperextension. But you need to have a little post-treatment. Meaning, let's say, you can advance the POL, the suture anchor, and have a little treatment. Have you ever done that, Josh? What I do is I keep them, I lock the brace at 10 degrees of flexion. I kind of like lock it in the middle of the back. Because it's scary sometimes when you see the hyperextension they have after the endodontomy. They may have 4 or 5 degrees. They go to 10 easily, 10, 15 degrees of hyperextension. I'm an old guy, sorry. I remember Houston's operation. The old movie, Jack Houston's operation, where he did the POL advancement and advanced the sedative and ranotes. That's what you do in these hyperextension cases. And it worked. It worked for him, and it worked in this particular case. So it's not, it's a relative, but not an absolute injury. It's a contraindication. You advance that on the tibia side? On the femoral side. On the femoral side. The femoral side. A little suture anchor, and then you just test it on the table and you just kind of tension it so that they get zero, but not the hyperextension. So what Dr. Brown's talking about is this idea, and Dr. Getgood's talked about it from the podium, is you really need to be careful about your patient with hyperextension doing that osteotomy because you can worsen it. So I hadn't seen that technique before using the POL advancement. That makes good sense from a biomechanical standpoint. I saw a hand go up the table there. He has a flight. So the fibular had a bulging fracture with the biceps on. Okay. Go ahead. Yeah. That's a really important distinction. So there are cases where you really have to be in there acutely. One is an arcuate fracture because if you have an arcuate fracture, it means if you look at your MRI and look at the size of it, if your biceps is off, your peroneal nerve is going to be pulled up with the biceps, and that's miserable to, one, try to do the neurolysis in that setting, but, two, try to get it reduced. So if I see an arcuate fracture, I'm trying to be in there within a week. I'm not as concerned about range of motion. But the bone isn't always great there, so it might be tough to get a screw in, and sometimes you have to use sutures through bone tunnels, and if you're doing a concomitant reconstruction and you're doing a fibular tunnel, you need to think about where your fibular tunnel is going to be, and that can make it certainly more difficult, but that's one that you don't want to miss. If the imaging shows that, you need to be on it right away. I think along with that, too, what Andy said, if you're doing an FCL reconstruction at the same time, definitely pass the graft first because you don't want to put the screw or anchors in, and then you can't pass the graft through the fibular tunnel, so just do that first. Going back to your talk, that study from Australia, looking at the 20-year data and only 22% survival, I think that's pretty powerful, and that was looking at hamstring with elevated tibial slope in adolescence. Has that changed your thoughts on graft selection, or has it more so changed your thoughts on addition of a concomitant antithelial complex procedure or on osteotomy? Osteotomy, I think, is just a hard sell, like Dr. Brown was saying. I don't think it changed my graft selection because, you know, I'm kind of biased from where we trained at BTV, but definitely LET. I think it's something to consider. I think, again, like what I was saying at the end of my talk is we know that slope is important, but do we need to correct it, or can we get away with just doing LET instead of doing a slope correction? I don't know. I think we'll see. What's your—oh, go ahead. Oh, it was regarding intracranial osteotomy, something I don't think is real widespread in non-academic centers. And my concern is, if people are actually doing these, are you seeing a problem with telephedral mechanics, ALTA, extensor lag? You know, if you get an ALTA, you get unstable telephedrals. Is that something that we understand yet? You know, I don't think that's well enough understood. I don't have the clinical experience long enough to say, you know, whether you're seeing telephedral contact mechanics issues. You know, ideally you're not changing the tendon length or doing an advancement, but indirectly you are by doing the closing osteotomy. A lot of these will have more Baja, and you can see Baja with a reconstruction—or with an osteotomy. But I think Dr. Larson may have an opinion on this. I saw him raise his eyebrows. I was just—what I was thinking is, you know, Charlie has a different patient population. This is super rare for the rest of us. You know, and even, you know, the people getting up on the podium are like—some of them are saying, you know, for me this is a second-fail ACL, the posterior tibial slope greater than 12. So just—it's pretty uncommon. It's pretty rare. And I think if you have the volume to do this with any kind of regular basis, the key is if you see one of these a year, you extract this, send it to the person that's doing it. I think that's probably the key point. One thing, if you do the tibial-tubal osteotomy, you can measure your telopite before you do the osteotomy, and then you can adjust the osteotomy when you reattach it. You can balance things. So that's one advantage. If you do a big erection, you can get the right telopite before you adjust it. So that's one advantage, which people don't talk about. Is there some kind of non-union ring that you're aware of? Have you seen it? I have seen it. You know, you just need to take a deep enough wedge and get some tensile form, and three screws, use three screws to anchor it, and, you know, straighten that brace and put it first on the knees and stuff like that. Just like you would a DVR for a femoral. I think Dr. Larson made a good point that this is not something I want to understand so I can start doing them. I want to know, if I have a patient who needs it, you know, should I send them or not? I want to understand the procedures so I know what the patient's going to get. These are not complicated. I did the first one. I said, you know, I just toot too much in my corn ears. I actually called Al LeBancourt and said, Al, can you come over and help me? He comes over every three months. We line him up, and then he comes. And every time you make that, especially if you're not taking the tubal block, it's really fun. So send it to someone. For you guys, it's probably not that common. You know, it's just bad news. I think that's an excellent point because, you know, this talk is, the whole ICL is on advanced techniques for the ACL surgeon. It doesn't mean that every ACL needs all these other procedures. It means you've got to evaluate all of them. And I think the slope is the most important one to recognize that in. You know, we didn't talk a lot about coronoplane, more sagittal plane, but the point is, you're not doing these anterior closing wedge primary. I'm not doing it secondary. It's the third time that I'd consider it, and that's not that common. So we don't want to try to find zebras and make everyone needs a slope-reducing osteotomy. But I would argue that it's in the toolbox of everyone in the room who's doing ACL reconstruction to fix root tears, to fix ramp lesions. We should know inside-out approaches. You don't need an inside-out approach for a ramp. But, you know, you should be familiar with that inside-out approach. It's in our toolbox to do medial and lateral reconstruction. And I think it's in our toolbox to do anterolateral complex reconstruction. And there's a lot of good techniques for all of these. You can look on different industry sites. You can look on AJSM or the Video Journal of Sports Medicine. Arthroscopy Techniques has a lot of great ones. So I think the osteotomy is one that you want to be pretty conservative on and talk to some of your colleagues at a center that maybe do a lot of them. But we really need to be looking for the other concomitant injuries and thinking about that in your treatment approach. Any other questions? Dr. Brown, I actually had one for you. With that arab knee, I know, Andy, we talked about it. We didn't really talk about coronal alignment, but are you doing a biplanar osteotomy then for those? It depends on how much correction you have. Some we will two-stage. If you've got a big coronal plane and a big slope, these patient-specific implants, we don't have much experience with them. So we'll tackle the slope first, and then bone graft and tunnels is usually a failed case, third-time failure. And then we'll come back, do the revision, and then do the coronal plane correction with that. Gotcha.

tibial slope

ACL injuries

measurement methods

graft failure

osteotomy

patient-specific anatomy