Dr. Clay Nuelle:                 Welcome to the Arthroscopy Association's Arthroscopy Journal Podcast. The views expressed in this podcast do not necessarily represent the views of the Arthroscopy Association or the Arthroscopy Journal.

Dr. Clay Nuelle:                 Welcome, everyone. I'm Dr. Clay Nuelle with TSAOG Orthopedics, from San Antonio, Texas. Today, I have the privilege of speaking with Dr. Jorge Chahla, from Rush University in Chicago. Dr. Chahla was the author on a paper titled "Single-Bundle and Double-Bundle Posterior Cruciate Ligament Reconstructions: A Systematic Review and Meta-analysis of 441 Patients at a Minimum 2 Years' Follow-up." This article was published in the November 2017 edition of the "Arthroscopy Journal". Dr. Chahla's co-authors include Dr. Gilbert Moatshe, Dr. Mark Cinque, Grant Dornan, Justin Mitchell, Taylor Ridley, and Robert LaPrade.

Dr. Clay Nuelle:                 Dr. Chahla, thank you for joining me today.

Dr. Chahla:                          Thank you so much, Clay. It's a great privilege for me to be part of this podcast.

Dr. Clay Nuelle:                 So let's start right in with what do you think are the primary, for those that have not read the article, the primary conclusions and the primary takeaways for the readers and listeners from the article?

Dr. Chahla:                          So the main takeaway from this article was basically that when you do a double-bundle reconstruction, you can expect to have better objective data, meaning that if you do a stress x-ray in the Telos machine, or over a kneeling stress x-ray, or if you have IKDC in the format of an objective measure, you can expect better outcomes if you do a double-bundle reconstruction. But the clinical findings and functional scores are probably the same if you do a single-bundle. That's the main conclusion of this study.

Dr. Clay Nuelle:                 And so, did those results surprise you and your co-authors in any way, or is that kind of pretty much what you guys expected when you started out to do the meta-analysis and the review?

Dr. Chahla:                          So to this point, I have to acknowledge my mentor and good friend, Rob LaPrade. He has a comprehensive approach to the PCL, starting with a pyramid of the anatomy, the biomechanics, and then the clinical outcomes. So basically, what we were expecting is that double-bundle reconstructions were going to perform better. And to this point, if you just analyze the level 2 studies included in this systematic review you can see that the data, even from the functional and clinical aspects of the data, are better for the double-bundle reconstructions.

Dr. Chahla:                          The problem is, Clay, that when you try to reconstruct this ligament, it is not like the ACL because it's truly two different bundles. If you look at the anatomy, the anterolateral bundle is not a crucial ligament on its own because you have a ligament that goes from the back to the front to the roof of the knee. Whereas you have the PM bundle, that goes from the back, or from the posterior aspect of the knee to the side. So one control is for a posterior tibial translation, which is the anterolateral bundle, and then one control is for rotation, which is the posteromedial bundle. And if you look at the femoral insertion, they have 18 millimeters of insertion. So it is basically impossible to reconstruct the femoral attachment if you don't do two bundles.

Dr. Chahla:                          Even in the biomechanics, when you see this, and you just kept one of the bundles, you don't get all of the laxity that you get when you get both bundles, which means that they're both co-dominant and synergistic in some sort of fashion.

Dr. Clay Nuelle:                 Yes.

Dr. Chahla:                          The same thing happens when you reconstruct them. If you reconstruct just one bundle, you cannot get the same biomechanics as the native knee. So that's why we thought that a double-bundle reconstruction would have better outcomes, not only on the objective side of it, but also on the functional side of it.

Dr. Clay Nuelle:                 Yeah, makes sense. You brought up a term that gets used fairly frequently in the literature in PCL reconstruction literature that we don't see necessarily as often in the ACL literature, which is co-dominance, which you mentioned in the co-dominance in the synergistic effect of both bundles.

Dr. Clay Nuelle:                 Like I said, you see that a lot more in the PCL literature, and it's always interesting, too, because I think most of us, and most surgeons that do a fair amount of cruciate ligament surgery, when you do a double-bundle PCL, you usually tighten the grafts in different positions, in different knee flexion angle positions. And I think Dr. LaPrade does it that way as well. And so maybe you could talk a little bit about just kind of the difference in the biomechanics, and how people oftentimes, and maybe even some of the results from some of the studies that were done in this paper, people tightening the graft in different positions based on the different bundles, and that sort of thing.

Dr. Chahla:                          That's a great question, Clay. I think tightening or fixing these bundles at different fixation angles is one of the keys for success. We know that the anterolateral bundle, which is the main component of the PCL, needs to be fixated or fixed at 90 degrees of flexion and reducing it to keep it forward. This is the main stem when we're trying to reconstruct the PCL. And then we have to bring the knee all the way down to extension because that's the angle where the PMB is at the most isometric point and fix it in extension. For this you can't use an interferential screw because if you use that in a single tunnel in the tibia, then you're basically fixing both at the same fixation angle.

Dr. Chahla:                          So that's why Dr. LaPrade basically uses biocortical screws with washers to be able to fix both at different fixation angles. In this review what we saw, was that most of the people that used a single-bundle fixed the knee at 70 degrees, and the ones that used the double-bundle usually fixed the anterolateral bundle at 70 to 90 degrees and the PMB at 20 to 30 degrees, which is not ideal based on our biomechanical data.

Dr. Clay Nuelle:                 Yeah, it makes sense, but I think that definitely mirrors what a lot of people would think in clinical practice, when they do a single bundle, they kinda split the difference a little bit, but put the knee in a little bit more flexion to try and take away that posterior drawer, but it's definitely interesting because I think a lot of people that have done and a lot of the reported outcomes in the literature would say that there is always kind of a 1+ posterior tibial translation present with a lot of different types of PCL reconstruction techniques, and so maybe the double bundle takes that away and this study seemed to kind of show that based on the results of the objective data testing.

Dr. Chahla:                          Yeah, I think that's one of the key things that we need to do moving forward is that when we do this reconstructions and anatomic reconstructions, we need to really measure in an objective way if we're doing a good job. So, we just published our outcomes on 100 patients on double-bundle PCL reconstruction, and I can tell you that I measured 100 x-rays posterior knee kneeling stress x-rays and they don't have more than 2 millimeters of side-to-side difference when you look at the kneeling stress x-rays.

Dr. Chahla:                          So, they don't stretch out if you do a good job with the reconstruction.

Dr. Clay Nuelle:                 Yeah, that's interesting. Yeah, especially because the previous anatomic studies and even reviews, sometimes people would kinda really hone in on the tibia and the tibial side and talk a lot about the killer turn and different reconstruction techniques around the killer turn on the posterior aspect of the tibia. But this one, you know, incorporates that, but certainly is more kind of directly related to the double-bundle versus single-bundle, which is more kind of oriented to the femoral side and so it kind of shifts, maybe it shifts a little bit of the focus of the type and technique of the reconstruction.

Dr. Chahla:                          That's correct, and the other important thing when you're thinking about the graft stretching out is that there's methodology in the bracing side of it, too. But now Dynamic braces that basically push the tibia forward with increased degrees of knee flexion, and therefore, it keeps the knee reduced where the PCL feels the most load, right?

Dr. Chahla:                          So, we know that at 90 degrees, the PCL is seeing probably most of the load, so that's where the PCL brace or Dynamic brace can be of significant help, right? Because it can keep the knee reduced when the knee is suffering from most load. So in a sense where the graft is healing, probably a PCL brace can help you keep the knee reduced while it heals in the right position and not in an elongated position.

Dr. Clay Nuelle:                 Yeah, that's a good point, too. I think you all made mention in the manuscript about a few of the studies you utilized Dynamic PCL type of brace like that, but not all of them. Do you think that could've played a factor at all in their final results, or do you think it's just one small sub-variable analysis?

Dr. Chahla:                          I think it's a really important thing to consider because even for the nonoperative treatment of PCL's, if you use Dynamic bracing, there's some good data now suggesting that those patients might heal in a better position than if you don't.

Dr. Chahla:                          So, I think even more for the reconstructions, you need to have that sort of anterior-directed force to be able to counteract the gravity.

Dr. Clay Nuelle:                 Absolutely. So how you think, this is a very well-done meta-analysis and review, how do you think this will kind of help us guide future research into either single-bundle, double-bundle or just reconstruction techniques in general?

Dr. Chahla:                          I think one of the main things that we need to think moving forward is that every time that we do a study looking at ligaments, we need to have some sort of objective data. And this is what we are basically asking in the discussion where we say, "if you do this type of reconstructions, you need to be looking at kneeling stress x-rays or Telos or some sort of objective data that can tell you how well your reconstruction is doing.

Dr. Chahla:                          Because we know that there can be degenerative changes moving forward if the biomechanics of the native knee have not been restored. So that's one of the main points, and the second point is that we showed that not even only the objective data of double-bundle reconstruction is probably better, but also if you use a single-bundle reconstruction, you can have lower functional outcomes if you look just only at Level II data, which is probably the best data that we have available.

Dr. Chahla:                          We additionally did a Detsky (sp?) score to look at the quality of the papers and only four out of 11 papers had good methods. So, this is something that we need to probably get better at, at reporting our outcomes because when we're doing these random clinical trials, it's of imperative need that we do a good job at this time if these studies you know will very well...

Dr. Clay Nuelle:                 And necessarily that's hard being able to compare studies that don't have as good of outcomes in any type of meta-analysis.

Dr. Clay Nuelle:                 Do you think, so for you and your co-authors, is it a double-bundle reconstruction in all cases, in most cases, is there any indication for a single-bundle reconstruction in your guys hands?

Dr. Chahla:                          I think the most reproducible way to do it, is to do the same thing over and over, not only for your ability to do the surgery, but also because of your staff might get more used to do the same technique over and over again, and it makes it easier for everybody on a surgery that is not easy to begin with.

Dr. Chahla:                          So, it is a procedure that is technically demanding with a high risk of neurovascular injury if you're not sure on the back of where you are if visualization is not very good, and therefore, I think replicating the technique over and over is the easiest way to do it and it has been shown also to be the most reproducible way to restore native biomechanics.

Dr. Clay Nuelle:                 Absolutely. One last question, I think the majority the ones utilized in this study and all the studies and in the review were allograft and the higher number was Achilles allograft, but then there were a few other allografts. Is that true, pretty much mostly all allograft, and then majority Achilles allografts, is that correct?

Dr. Chahla:                          That's correct. You know for single-bundle and double-bundle, most of the authors used Achilles allograft. The second mostly used allograft was hamstring or tibialis anterior. I think having a bone plug on a graft that is sufficiently long to be able to fix it on the tibia is probably what we should be using, and that's what we use in our technique as well.

Dr. Clay Nuelle:                 Absolutely.

Dr. Chahla:                          Additionally, you don't wanna use a quadriceps tendon because it has a pretty active role in reducing the tibia forward, and therefore, trying to avoid harvesting the quad tendon and also for the sake of time might be another reasonable option to keep using allografts.

Dr. Clay Nuelle:                 Yeah, certainly, particularly if you're talking about reconstructing the PCL in the setting of a multi-lig reconstruction, multi-lig knee reconstruction, which is often the case in many cases.

Dr. Chahla:                          Correct. PCL injuries, isolated PCL injuries are only present in 17% of the cases. So as you said, in most of the cases these are gonna be combined injuries and you wanna be as efficient with time as you can and harvesting grafts at that time point might add morbidity and time to the surgery.

Dr. Clay Nuelle:                 Absolutely. Well, thank you so much for sharing your thoughts with us today, Dr. Chahla. Dr. Chahla's article, "Single-Bundle and Double-Bundle Posterior Cruciate Ligament Reconstructions: a Systematic Review and Meta-analysis of 441 Patients at a Minimum 2 Year's Follow-Up" can be found in the November 2017 edition of the "Arthroscopy Journal" or online at www.arthroscopyjournal.org.

Dr. Clay Nuelle:                 Thank you for joining us today, Dr. Chahla.

Dr. Chahla:                          Thank you very much. It's a great honor for me.

Dr. Clay Nuelle:                 This concludes this edition of the Arthroscopy Journal podcast. Please join us next time.