Good afternoon. I'm John Grant. I'm an associate professor at the University of Michigan in the MedSport sport medicine program. I'm going to talk today about the posterior cruciate ligaments on pearls and pitfalls. So we'll start with a case, he's a 35 year old male who was injured during a snow sledding accident, caught some air and landed on his bent knee. He had initially been seen at outside facility and was recommended to undergo non operative management, and he presented to me for a second opinion. Over the time since his injury, he's tried three different braces and done eight weeks of physical therapy, which he found to have helped but still didn't really trust the knee. He found a dynamic PCL brace to be the most effective of the braces that he tried, but he works as a carpenter so he continues to have feelings of unpredictable instability and intermittent effusions, as health is otherwise not contributory. So we think about how the PCL is injured. The most common one certainly is a dashboard injury that's the classic kind of OED exam question, as the dashboard intrudes and drives the tibia posteriorly. A lot of cases as well there's some sports injuries as well, but primarily landing on some sort of a flex knee or a blow to the anterior proximate tibia, driving that tibia posteriorly. From an epidemiology point of view, you can see the dashboard injuries and a fall onto a flex knee are the most common mechanisms here, and certainly between car and motorcycle accidents, the most common sport wise soccer seems to be the one that's the most common there as well. On exam he's a relatively big guy six foot three to 182 pounds with a BMI of 36. He had a trace of fusion good quad tone no atrophy so he's been working well on his quads. His range of motion was symmetric and he stands in mild varus. The rest of his ligamentous exam was stable, other than a positive posterior drawer and posterior sag. His dial test was negative. So in the clinic trying to detect these PCL injuries. The first thing I always do is comparing like we usually do bilaterally, you want to get a feel for the tibial station or his tibial step off so holding him as if you're going to do a drawer test and putting him right on the tibial plateau, as they slide down off the femoral condyle and getting a feel for how much of that tibial plateau you can feel with your thumbs anterior to the condyle. We can then add some special tests the posterior drawer test being the most sensitive and specific, but other ones to try to correlate your findings can be the quadriceps active test where the knee is held at 90 degrees of flexion and the examiner pulls down the ankle, while you ask the patient to try to straighten their knee out, and they should the quads will then pull the tibia forward as you can compare. This is similar to the posterior sag test where you line up both knees at 90 degrees and looking across tangentially across the tibial tubercle, the affected side tubercle should be much less prominent. We also do the dial test look for combined injuries either posterior anterior medial rotatory instability or posterior lateral rotatory instability, and then the reverse pivot shift as well. So one of the things that's important in the physical exam is the effect of tibial rotation neutral rotation demonstrates the most dramatic AP translation both with anterior and posterior drawer. We know that if we internally or externally rotate the tibia. These poster medial and poster lateral structures really can tighten up the need to some extent and decrease the amount of translation in the absence of an injury to these corners. So very important to make sure that the tibia is a neutral rotation to get a true evaluation of the isolated PCL injury. So this patient had x rays here they're relatively normal, where we're in cases such as these especially more suspected chronic situations, we really want to add some additional x rays. So this is where the PCL stress x rays really come in and are very important. Many times in the literature you may read about kneeling PCL stress views which are identified here on the left. This is where you kneel with your full weight onto your shins, where you're pushing on your tibial tubercles. Challenge here, especially in the acute situation is this is very uncomfortable for the patients and so they guard and may not put as much pressure down to cause that posterior translation. And so an alternate way to do it on the right hand side here is these weighted gravity PCL stress views, where the patient gets to lay on their back their heel is supported with their hip and knee and 90 degrees, and usually a 20 pound weight is placed on their and this typically is much more comfortable for the patients. We look at these x rays, I like to line them up side by side for a equal amount of magnification and comparison. You really want to get a reference line here so I typically use the tibial plateau as the reference. If we start on the left side here, we're going to place a line that's orthogonal to the reference line in line with the posterior condyle of the tibia, and then a second one that's ideally in line with the posterior condyles of the femur. Unfortunately on this this view the femur isn't perfectly rotated so we sort of estimate a spot in between. Then we measure the difference between those two lines as the amount of posterior translation of the tibia relative to the femur. In this case, this was about seven millimeters. When we do the same evaluation on the injured side, we can look at the back of the tibial plateau, and the femoral condyle here and we can see that there's a substantial difference here for about seven millimeters difference. When we flip over and do the weighted gravity stress views, really the measurements exactly the same except the orientation is slightly different so similar things here. Studies have shown that the outcomes and the amount of translation really are very similar between kneeling stress views and these weighted gravity stress views. However, patients find the weighted gravity stress views much more comfortable. Stress radiographs do play a big role I think in especially chronic PCL injuries because MRIs can show that the PCL appears to be relatively intact, but clinically it's stretched out. Stress radiographs are more accurate than a KT-1000, so an instrumented posterior jaw test, and have demonstrated that greater than eight millimeters of posterior translation is indicative of a complete PCL rupture. If you get more than 10 to 12 millimeter translation, that's really more than the PCL itself would prevent and this demonstrates a suggestion of additional injuries such as the posterior medial or posterior lateral coronary deficiency as well. So getting back to our case, certainly seems to have this continued PCL instability. PCLs in general are tolerated much more than ACL deficiency, especially when we're able to gain excellent strength. Studies have shown that regardless of surgery or non-surgical management, the patients are able to gain equal or greater quad strength compared to the normal side. They usually do pretty well. However, as with ACL injuries, there's still a progressive amount of OA in the knee due to the even micro instability, which tends to be in a pattern of medial and or patella femoral joint degenerative changes. So in this patient, we had discussion with respect to continued non-operative management versus surgical reconstruction. And given the fact that he'd gone through therapy and tried different braces and continued to have feelings of instability, especially at work, he elected to go for with surgical management. In this case, typically my graft of choice is either an Achilles allograft with bone plug or a quad tendon autograft with bone plug, but there are various options that you can use depending on your preference. During the surgery, his examination under anesthesia demonstrated a grade 3a posterior jaw, so fairly substantial posterior translation and was otherwise stable to his other ligament exams. So we look at reconstructing the PCL, just like the ACL, we need to have a good understanding of the anatomy. The PCL is about four centimeters long intra-articularly with a diameter of about 13 millimeters, and this gives a cross sectional area of about 120 to 150% of the ACL. So this is actually the strongest cruciate ligament. And like the ACL, it has two specific bundles. However, they're the opposite of ACL, so it has an anterolateral bundle, which is the largest and strongest, and is tight inflection, while the posterior medial bundle is tighter in extension. We'll also find in variable cases these meniscal femoral ligaments, which arise from the posterior horn lateral meniscus. There's one that comes anterior to the PCL, which is the ligament of Humphrey, and one which runs posterior to the PCL, which is the ligament of Risberg. Now these are variable, some patients don't have either one, some patients have both, and some patients have one or the other. We'll look now at the insertion points when we're trying to plan where our tunnels is, so we can outline here on the femur and the tibia the insertion points. So here we've got a picture of these nicely outlined meniscal femoral ligaments here. From a tunnel position, the anterolateral bundle, the primary strongest bundle, is really high in the notch, starting right up at the 12 o'clock position at the roof of the notch, and is centered about seven millimeters off the articular cartilage, and so this is important for placing our tunnel. The posterior medial tunnel or insertion site is a little bit more posterior or lower in the notch, and a little bit further off the cartilage, about 10 millimeters off the cartilage. In reality, though, when you look in the interconvular notch, the PCL insertion extends beyond the 12 o'clock position and sweeps all the way down to the four or five o'clock position or seven to eight o'clock position depending which knee you're talking about. These pictures here will really demonstrate the broad insertion of the PCL, so lower down you can see the posterior medial border and extending up to the anterior medial bundle more anteriorly. At the time of surgery, normally we're looking at the PCL with the knee inflection, and so the ACL also tends to look lax, certainly because the tibia tends to sit in a posterior sag position and then you can do your active anterior drawer and you can see that ACL tension up when the ACL is normal. There are different ways to do these tunnels, either inside out or outside in. I've transitioned to do these inside out with an accessory anterolateral portal, and I actually use this low profile reamer as my guide. So here I'm positioning for a single bundle PCL reconstruction, and I tend to cheat toward the anterolateral bundle since it's the biggest and strongest. This is a 10 or 11 millimeter reamer, so as I rotate it, I can just make sure that I have about two to two millimeters or so of free space between the cartilage and my reamer, keeping me about seven millimeters off the cartilage surface. Here's an example of one of these outside in guides you can use, and you can really set the target where you want it on the inside of the intercomnal notch. Following the single bundle reaming, I've got my passing guide wire up through the tunnel here so we can see where that tunnel sits. There's some debate, you know, as we do with the ACL as well, should we be doing single or double bundle reconstructions? I think it's great to be able to consider double bundle on the femoral side, and I've transitioned to doing this with a single tibial tunnel. Lots of research has been done to this effect, maybe not as much as the ACL, but certainly biomechanical studies in the lab have demonstrated double bundles to be more stable. However, across multiple studies and clinical outcomes, the literature has been a little bit mixed, with some papers showing really minimal clinical difference, and some papers showing some improved clinical difference. Typically, there may be some improvement in the translation or ligament testing, but patient outcomes really don't vary very much. So, despite this, adding the posteromial bundle really doesn't take a lot more time, so I think it's something reasonable to consider. Looking at our PCL tibial tunnel, again, we want to look at where this sits and the bundle sits. Anterolateral bundle is posterior to the root of the posterior horn meomeniscus. These are the shiny white fibers, so it's very important when you're cleaning off the PCL facet that you don't accidentally take down the posterior horn meomeniscus root because they're very close together. But you need to be aware very much with PCL reconstructions of the vascular anatomy posteriorly. The tibial artery can sit right there. Tibial artery typically sits more superficial to the popliteus muscle on the back of the tibia. However, there's an aberrant tibial artery situation where the artery actually runs deep to the popliteus and is literally right on the back of the tibia. So, for either posterior horn lateral meniscus repairs, or specifically when PCL reconstructions, it's very important to take that into consideration and be prepared for that. This picture down below comes from Dr. Bruce Levy. This was a patient of his who had a vascular repair. And you can see here in the back of the knee, the cameras in the posterior portal, you can see his retrograde reamer to the right and his protection guide in the center. But below that, you can see the stitches from his vascular repair literally sitting right where this tunnel is going. So, this is something to be very careful of. Looking at the tibial side, we're going to prep the tibial tunnel location. I start anteriorly through the notch to clear off the remnant of the PCL from the PCL facet. Most of the time, because of the slope, I can't quite reach it all the way from the anterior aspect. And I want to make sure I stay clear of the shiny white fibers. If the back of the PCL facet is not visible with a 30-degree scope, we'll typically switch to a 70-degree scope. And then under spinal needle guidance, we'll place a posterior portal. This will allow my ablator or debrider to really get down the back of the PCL facet and peel off the back of the capsule to be able to see some of the popliteus muscle. That then lets you know that you really cleared off the whole facet. We'll then place the PCL tibial guide and drill our guide wire. You always want to have a guide that protects it from going out the back of the knee. And you may consider using fluoro, especially when you're starting. Reaming first by power. However, I always will go through the interarticular part of the cortex by hand. Again, making sure that you don't plunge out the back of the knee. I'll use a rasp to chamfer the anterior edge of the tunnel. One of the downsides of doing this type of reconstruction is the abrasion of the graft against the anterior aspect of the tibial tunnel, which has been called a killer curve. Then you can start shuttling your sutures for your graft passage. So here I've got the ablator and the posterior portal. We can see a little bit of the popliteus muscles that peeled off the capsule posteriorly. Now place our tibial guide. And under fluoro, we can see where the placement of the guide and the PCL facet and the advancement of our guide wire. Once the guide wire is in, I switch to a protectionary to keep that guide wire from advancing as we're reaming. We'll ream up almost to the cortex and then switch to hand reaming to come into the joint. You can then use a certain curved rasp up to the tibial tunnel to rasp that anterior aspect of the tunnel. And you can look down your tunnel to make sure it's clear of debris by placing your camera in the posterior portal. Then you can start shuttling your sutures for your graft passage. So with respect to graft passage, there's a couple of ways to do it. You can deliver your graft like we do in ACL, straight up through the tibial tunnel. But it then needs to make that sort of curve anteriorly and then again into the femoral tunnel, which can be a bit challenging to get the graft to turn those ways inter-articularly. So I've switched. I make a slightly bigger intermedial portal and actually deliver my graft directly through that portal, tibial end first, pulling it down into the tibial tunnel. And then we can bring the femoral side into the notch and advance that up into the femoral socket. Traditionally, there's also open approaches with the open posterior inlay, posterior medial approach back there, which I think is done less commonly now, sometimes for a PCL avulsion fractures. Fixation wise, if you're doing a single bundle reconstruction, you want to fix that graft at 80 degrees, again, optimizing the anterolateral bundle function. If you're going to do a double bundle, you'll start with the anterolateral bundle, fixing it again at 80 degrees, and then bring the knee to near full extension to tension the posterior medial bundle. One of the challenges here is how to know when you've got this correctly tensioned. If it's an isolated PCL injury with an intact ACL, certainly you can tension that with an anterior drawer, tensioning it against the intact ACL. In many cases, however, we're doing this in a multiligamentous knee injury where the ACL is also deficient. So you have no real restrictions of anterior and posterior translation. So a couple of ways to tension. I always tension the PCL before the ACL. You can either hold that tibial step off in the normal position with palpation, or I tend to use fluoroscopy to make sure that the posterior condyles of the tibia and femur are well aligned as I'm fixing the PCL. On the right here, we can see examples of a single bundle PCL on the top and a double bundle ACL down below with the anterior lateral bundle more prominent and the posterior medial bundle underneath it. I fix my AL bundles with a bone block with a screw, and you can see the position of that just different from your ACL reconstruction. So hopefully that was helpful as an overview. Thank you.

posterior cruciate ligament

PCL injuries

physical examination techniques

surgical reconstruction

tibial rotation

posterior cruciate ligament injuries

evaluations

PCL instability

graft placement