So, we all know about the pathomechanics of CAM impingement. I think this video kind of shows it well. You know, when you have a large CAM deformer, you get the shear stress, shear injury going on the chondrolateral interface. And I think that once we understand the biomechanics, I think that's why we want to understand why we want to correct this comprehensively. Next slide. So when I think about optimizing a CAM resection, I think about three main aspects of it. The first is planning, and so we want to have an adequate surgical plan. The second is access in terms of visualization. The last one is execution. Next slide. So as far as planning, in my office, I'll get a routine set of plane radiographs that will consist of an AP pelvis, a done lateral view, and a false profile view. And I would say that I probably get about 90% of my information in terms of the proximal femoral morphology, as well as the pincer deformity on my plane x-rays. If I have any questions or I have any concerns about the three-dimensional anatomy, I'll go ahead and get a CT scan. Seems like it's working. So the CT scan, I think, is really helpful in terms of trying to define the three-dimensional anatomy, trying to understand what the morphology is. And in this particular case, I got the CT scan because, you know, I saw a little os acetabuli, and I was concerned about the size of it and whether or not this was something that needed to be fixed versus resected. There are newer programs available that will help map some of these three-dimensional morphologies and really give you this kind of heat map so you can understand the precise nature of it. So here you can see that this CAM lesion looks like it's probably between 1 and 3 o'clock. You can actually rotate these images, as well, and they come in, like, a PDF file. And this will allow you to kind of synchronize what you're seeing arthroscopically with, like, the global anatomy that's being presented on the CT scan. In our research lab, we've been interested in trying to develop three-dimensional models with MRI, and in particular, 1.5 Tesla MRIs. There's certainly a lot of advantages to that. I think the first one is that you can get all of your diagnosing information with one study. So obviously, all of us get MRIs to understand the soft tissue diagnosis. But think if we could also get the bony anatomy, as well. And so if we can get both of those pieces of information, I think it would be very useful. Certainly it's widely available. I think all of us have pretty readily, easily accessible MRI. It could be cost-effective if you can get one study in place of three different studies. It's non-invasive, as well as radiation-free. And so our hope is that we want to try to validate an MRI-based Osseous model, and one that would be as good as CT scan. So here's an example of an MRI that you get in the office. You'll have to get, like, additional sequences. But eventually, the idea is that you could segment these models so that you can get a three-dimensional model just like a CT scan. So this was the basis of this paper that we published in the Journal of Orthopaedic Research comparing MRI to CT scan to laser scan. So we did point-to-surface distance registration. The white represents a CT scan, and the green represents an MRI model. And so these are surface-to-surface comparisons. Basically, we can do absolute differences. We can compare it to, like, a ground truth. In this particular study, we compared to laser scan to see what the relative differences were, as well. And we can get it with pretty significant specificity. So in terms of the geometric comparisons, again, our groups were MRI versus CT, MRI versus laser scan, and CT versus laser. And again, laser scan was considered to be our ground truth. The white basically represents where the models match one another. The blues represent areas in which the model is less than, let's say, the reference. And the red represents where the model is greater than the reference. And so when we did signed point-to-plane distances, basically, when we're comparing it to the ground truth of laser scan, we found that MR versus CT, MR versus laser, and CT versus laser were all actually statistically similar. There wasn't a significant difference. But when you look at the graphs, you can see that the MR versus laser actually had a smaller mean difference. It was like 7.07 millimeters compared to laser scan. So very significantly accurate. And when we look at point-to-point differences between, again, MR versus CT, MR versus laser, and CT versus laser, essentially, there were no differences between all these different modalities compared to one another. So we did find that there was absolute agreement between MR versus CT and MR versus laser based on these models. And so I think with this study, we're basically trying to start creating three-dimensional models that I think are accurate and similar to CT scan, which is basically the gold standard clinically, or laser scan, which is the gold standard in a research setting. So what does this mean for hip research? Obviously, both for clinical perspective, it can be very valuable to have a bone model and a soft tissue model kind of an all-in-one study. For surgical planning, you can do the same three-dimensional analysis that we've been doing with CT scans with MRI. Obviously, from a patient perspective, you can get these studies without having to incur any radiation exposure. 1.5 Tesla MRIs, I think, are readily available. You know, we're working on three Tesla MRIs as well, but I think with a 1.5, we find them to be as good as CT. So the three doesn't seem to offer a significant advantage at this point. And clearly, once we start to quantify these models, I think we'll have a lot more data that we can start to do more granular research in terms of three-dimensional morphologic analyses. The second aspect of optimizing a CAM deformity is really access. Unfortunately, I don't think there's much in terms of technology that can help us here. But again, we can either use an interportal capsulotomy or a T-capsulotomy to expose our proximal femoral anatomy. I think either is sufficient, depending on what your surgeon or what you like to do. But just realize what you're able to visualize, depending on each of them and how you're able to see, or you might have to do a little bit more rotation or extension to be able to see your morphology a little bit better. In my practice, I like to do a T-capsulotomy, and this starts with an interportal capsulotomy that is usually about two centimeters or so. I'll place traction stitches on the S-tabular side of the iliofemoral ligament to help retract the proximal aspect of the iliofemoral ligament. And this will help with rim prep as well as labor repair. Once the central compartment portion of the procedure has been completed, we'll go ahead and remove some of the periarticular adipose tissue. We'll do our T-cut, which will be perpendicular down the femoral neck, and then we'll place traction stitches on both the medial and lateral leaflets. And this will really give us a comprehensive look at the entire proximal femoral anatomy. So once we can see everything, at that point, the osteoplasty, I think, becomes much more intuitive. And so when it comes to the intraoperative guidance, I think this is another area in which there's been some really neat technology. We basically based a lot of our measurements based on Chris's work that he did years ago in terms of trying to define how to best access the different aspects of the cam deformity. And so we'll place the hip in, like, six positions all the time in the same way. So 1145 is with the hip and leg in extension and inter-rotation, 1230 is extension and neutral, one o'clock is extension and extra rotation, then we'll go ahead and flex the hip to about 50 degrees to get the 145, 50 degrees and 40 degrees of external to get 215, and 50 degrees and 60 degrees of external rotation to get 245. We'll go ahead and, once we get the floor images, the computer software program will create these Mohs circles and then automatically create alpha angles. And so you can do that kind of in real time with all these different measurements. At this point, then, you'll go ahead and perform your cam osteocounterplasty. For me, I usually start with the leg flexed at about 30 degrees. I'll make my initial mark adjacent to the labrum, and I'll go from lateral to medial. And then, in order to access the lateral aspect, we'll go ahead and extend and internally rotate the foot. That will get us to about 1230 to 1145 if we really internally rotate. And that kind of helps to get that far lateral extent. And obviously, it depends on the patient's particular morphology, but sometimes you got to spend a little bit more time there. And in some cases, if you have, like, a really far lateral cam or, like, a pistol grip deformer, you may have to place the hip in traction, and that can allow you to get much more proximal, much more lateral. Usually, you'll have to kind of cheat your burr on the – just above the lateral synovial folds. And that way, you can really correct that lateral extent of the deformity. So here's our beginning x-ray. We'll go ahead and draw our alpha angle, and then when we're done, you can get a repeat one to make sure that you've kind of completed your lateral section. As far as the medial side is concerned, you'll go ahead and flex and x-ray rotate the leg, and that'll show you your medial extent, again, getting to that three o'clock position and even further medial than that if necessary. You can get your image. Again, it'll draw the alpha angle for you, and then you can do your follow-up alpha angle measurements to make sure that you've done a complete resection. So again, once we start with our 1145, 1230, and one o'clock positions, pre-resection, you can see the alpha angles are above. Afterwards, you can see that when we're in green, we know that we're less than 40, 45 degrees, and you can see that all those time points were down-degreed, so it tells me that I've kind of completed my resection. Again, 145, 215, 245, these are pre-op images on the top panel. And then, again, once you've done your resection, you can check these with the same degrees of flexion rotation and see that you've kind of completed your resection. So again, once you see green, you know that you've completed. And I like it because sometimes it's hard to know when you're done, but this kind of helps you realize that you've done a comprehensive resection. So here's the office-based x-rays, AP pelvis. You can see that we've corrected that lateral cam deformity. And then on the done lateral view, you can see a correction or restoration of the offset as well. I think in conclusion, optimally correcting a cam deformity really starts with preoperative planning, and I think some of the newer technologies in terms of getting better information, you know, heat mapping and three-dimensional analysis I think are going to be important. MRIs are going to get close to CT scan. Hopefully we'll be able to use one study to get all of our information. Access and visualization is critical. I don't think there's any technology at this point that can help us with that, so that's just standard surgical technique. You know, in terms of completing your resection, dynamic assessment I think is really important, as well as using some of the newer softwares to help guide you as far as what your alpha angle measurements are. And I think when you abide by these principles, I think you'll be able to leave the operating room confident with your camera section, so you won't have any surprises when you get to the office. Thank you very much.

CAM impingement correction

MRI-based osseous models

surgical planning

T-capsulotomy

surgical outcome