Patellar Issues in Primary Total Knee Arthroplasty

Speaker 1Uh, thank you and uh we, we'll proceed to your talk uh regarding the Pellafam issues in, in Tohony.

Speaker 2Yes, thank, thank you so much. It's such a pleasure to be here. I, I, uh, I'm so thankful to, uh, the entire committee for organizing this event and inviting me and thank you certainly to our, our co-chairs for, for this section.

Speaker 2Um, I'm gonna talk a little bit about the patellofemoral joint in Primary total knee arthroplasty. Um, a big thanks to AO Recon for organizing this, really, uh international faculty, uh, uh, of, of which I am the smallest. Um, so thankful to be participating with these, um, these Other presenters, really brilliant, brilliant talks. These are my disclosures. I'm a consultant for Stryker. I have an equity stake in a Surgery center. I sit on the editorial board of several, uh,

Speaker 2English journals. So patellofemoral tracking is really the, the, the, the holy grail for success and it was really this article, one of the first articles that I think began to start to shape our minds on, on how to address the patellofemoral joint. This is obviously John Insa's work, knees put in uh in '93 and '94. Some were embarrassed, some were in Valgas. We're obviously better at those techniques now. Uh, no resurface Patella exceeded the native thickness. This was the conventional teaching. There was a.

Speaker 2A 3% lateral release rate, but still, some had anterior Knee Pain, 7% had Pain with stairs, and some had uh painless creptence. So, uh, how do we address it today? What are the modern techniques and how do we get there? It really is the holy grail. And so I wanted to, you know, kind of go through that. First, it takes a good Approach. It's really important that we can see what we need to see, appropriate size incision, wanna minimize soft tissue. Uh, I think more and more in my practice, I've understood external.

Speaker 2Rotation of the tibia to decrease tension on the patellar tendon, uh, ligament. We know the distal resection is important. You know, before we can talk about the Patella itself, we have to talk about what are the keys to success for patellofemoral mechanics. So alignment and particularly flexion and extension of the distal femoral cut. Now that can be very hard to control. We know from, uh, engineering studies that the quadricep vector is so important and it's around the spherical axis, but how do we hit our target? Well, this is what we know.

Speaker 2Or a more practical paper showing that the sagit position of the Knee correlates to anterior Knee Pain, and anterior Knee Pain actually is increased with extension of the femur, OK? Relative extension. So we're putting a hard metal rod with our, our manual techniques into the femur, relatively extending the distal femur, increasing anterior Knee Pain. It, uh, anterior Knee Pain increases if we have anterior offset, uh, if our ratio is higher, and I'll show you that in a bit, and even with the tibial cut.

Speaker 2So, so to understand why people have kneecap Pain after Knee Replacement, it's not always just the Patella. Here's really the explanation. It's an excellent study looking at posterior condylar offset and posterior tibial slope, and essentially what they did is they looked at these forces in this model.

Speaker 2Contact forces at the patellofemoral joint in a PS Knee, uh, just like we were discussing to see what changes the posterior collar offset and posterior tibial slope had on the, uh, the, the, the, the overall pressure on the Patella. This is what, uh, the, the, the modeling looked like and you, so you can see how the implants were growing in the anterior posterior and the slope was changing on the tibial side. They found contact stresses on the Patella.

Speaker 2Increased with increasing the posterior condylar offset and increasing the tibial slope. Now, you gotta be careful not to increase the posterior tibial slope too much cause then you run into flexion and stability, but you start to see the position of your components and overall alignment in the Knee, how critical that is to how much force is through the kneecap and anterior Knee Pain. This is a graphic representation of anterior femoral offset which must be minimized. You can see the example on the right which is.

Speaker 2Good position and the importance of measuring posterior condylar offset. I encourage you to start being very critical of your technique and looking at your X-rays when you see people with anterior Knee Pain. It's not always just the Patella. And now we gotta figure out how to rotate. Now, some guys do white side lines like you'll see on, on the right using bony landmarks. Other guys are using a tension device inflection to try to get that rectangular space. We heard a brilliant talk earlier about trying to, to, to, to get these gaps right in valgus knees, but really every Knee, right, we wanna make sure that we match it well.

Speaker 2So there are various techniques there, but how do you rotate your tibial component? Do you use fixed landmarks? Do you float it? Personally, I float it, take it through a range of motion, mark it, and then set it. Uh, but these techniques, uh, uh, can be different from manufacturer to manufacturer because there's symmetric versus asymmetric, uh, tibias which have to be taken into account. Often, asymmetric tibias, the tendency is to over externally rotate, so be careful of that. We know tibial component rotation can lead to postoperative.

Speaker 2Extension deficit cause it's not respecting the screw hole mechanism. Well, that keeps pressure on the Patella, that keeps pressure in the Patellofemoral articulation along the kneecap causing Knee Pain and stiffness. This is a real challenge. This is a case, uh, from uh Guo Chen Lee. I give him full credit for this. These are preoperative X-rays. Intraoperatively, you can see the internal rotation of the tibia. Um, this went on to revision. You can see how he's nicely externally rotated. Also changed the, uh, femoral position and that.

Speaker 2Patient ended up doing quite well. So, so if it's a talk about the patellofemoral joint, we have to at some point talk about the Patella. So here you go. Do we resurface or do we not, right? That is the question. And believe it or not, the debate continues. This is a, um, analysis of, of, of the randomized controlled trials. This is in 2019, so very up to-date Research. There were 20 articles that were included and, and, and this is really the, the, the, the summary. If we don't resurface the Patella, and I wish I.

Speaker 2I knew all the countries we're talking to today. I wish I knew what the tendency was in each country, but here in the US, uh, we tend to be resurfacers. But what this, this study, study show was there's an increased revision rate if the Patella is not resurfaced. Nonetheless, the debate continues. This is Australian registry, which again says higher revision rates if the Patella is unresurfaced, uh, slightly lower if it's an inlay, or the lowest revision rate with an onlay Patella.

Speaker 2Despite all of this, uh, patellar surfacing does come with a cost, and this is why some of us, uh, no doubt move away. There are complications and we'll go through several of them here. First of all, it's technically demanding. This is a, uh, picture from the literature showing isolated resurfacing in the middle of the set that is unintentional and could potentially cause a, cause a real problem. This is periprosthetic patellar Fracture. We'll talk here in a little bit about the.

Speaker 2Risk factors including patellar thickness, osteoporosis, and trauma. Uh, the treatment's really based on the, the, the, the function of the patient. You may look at that X-ray and say, oh my goodness, that, that X-ray is horrible, but the, if the extensor mechanism is intact, you may not operate on this patient, instead immobilize. If the extensor mechanism is disrupted, obviously that often leads uh to Surgery, and we have to consider the implant stability.

Speaker 2And, and what about surgeon, uh, uh, factors, right? So we talk a lot about the patient and how thick or thin their bone is, but what about, what can the surgeon affect? This is a great fairly recent study, uh, out of my fellowship institution that looked at

Speaker 2Factors leading to complications following uh Knee uh Patellar resurfacing. So 10 millimeters uh increase in thickness only led to 3 degrees loss of motion. So this concept of overstuffing the Patella is perhaps not the big concern that we once thought it was. There was no difference in the Fracture wrist with the residual Patella less than 12 or more than 12, but there was significant.

Speaker 2increased Fracture, Fracture risk if the pre-resection patellar thickness was 18. So in these patients in particular, we need to be careful when we're resurfacing. So it's what the patient brings to us, we have to be thoughtful of. Now, patellar dislocation and subluxation is obviously an issue. It's tempting. I have some sports colleagues that always want to consider an MPFL reconstruction. This is rarely a soft tissue solution.

Speaker 2Uh, a really careful evaluation with CT of the component position is important. If you find this, there are salvage techniques. I include this, uh, just for completion. I've never done the gold wing reconstruction of the Patella, but if there's insufficient patellar bone, this is, uh, described, and I'd encourage you to, uh, look this up in the literature and have it in your armamentarium. There is patellar clunk, which is essentiallyar scar tissue around the Patella, particularly in PS designs that can happen. The treatment here is arthur.

Speaker 2Microscopic debridement has a fairly low recurrence rate. So, uh, uh, are, are you tempted to elect not to resurface based on the complications? Well, a couple of slides about that. If you're going to not resurface, you should really consider denervating the Patella. This is well described, uh, in, in many papers. This is one prospective randomized study. Uh, you need to be fairly aggressive in your denervation procedure. Again, this is well-documented in the literature. I put in the chat by.

Speaker 2The way, a link to my OneDrive account that has uh these articles to describe the specific technique, but denervation of the Patella, very important, uh, if you're gonna, uh, save the Patella. Also, if you elect not to resurface, you should uh consider, um, facetectomy, lateral facetectomy for improved position. The technique is well described uh by Nunley at Awashu. Essentially, you leave the lateral facet and you go on to resect the bone laterally.

Speaker 2You cut with a saw, you mark it here, he's showing you, cut with a saw and then remove the lateral facet. This is what the X-ray looks like. This improves tracking and there's good uh follow-up data on this. My personal Patellar resurfacing technique in my last 20 seconds, I resurface them all. I trim the osteophytes, I debride the synovium. I measure the native patellar thickness. Use two towel clips, this is a freehand cut for me down to 12 millimeter thickness, medium, uh, uh, minimum.

Speaker 2Uh, I use a symmetric button. I medialize the component. You can see here I'm marking the lateral border. I perform a limited lateral facetectomy and I submit in most cases. Interestingly, cementless failed for reasons that can be addressed by design and so I have started to use some cementless patellar components. Nonetheless, make sure you're tracking well. What is the summary hand?

Speaker 2Filling the Patella at the time of Primary Knee is critical for outcome. You need to optimize femoral and tibial positions. If you're not gonna resurface, so without patellar resurfing, resurfacing, it requires careful technique. If you do resurface, it still requires careful technique. Good luck, my friends. It's a pleasure to be with you. Again, the uh articles are in the uh chat box.

Speaker 2Thank you.