Scott Webb (Host): Most of us have heard about total knee replacements, but my guest today is here to tell us about the many benefits of partial knee replacements and who's a good candidate. I'm joined today by Dr. Joseph Serino. He's an orthopedic surgeon specializing in hip and knee replacement.

 Welcome to A Bone to Fix from Orthopedic Associates of Central Maryland Division. I'm Scott Webb, and I've got a bone to fix with you. Dr. Serino, it's nice to have you back. Today, we're going to talk partial knee replacements. And you know, I've done a lot of podcasts on full knee replacements. Partial is still a bit of a gray area. I just want to get a sense like who's the ideal candidate for a partial knee replacement versus total. Are we talking about age, activity level, extent of arthritis, you know, contraindications, all that good stuff. Like, how do you know? You know, how do you inform patients? Like, "You could do partial or you could do full." You take it from there.

Dr. Joseph Serino: It's a great question. And honestly, I'm not that surprised that you haven't heard much about partial knee replacements. Based on some of the latest registry data, less than 4% of all knee replacements done in the U.S. are actually partial knee replacements. And your question is perfectly on point because I think the primary reason for that is it's a very controversial answer, who is an ideal candidate? I think, it can be hard for surgeons to really pinpoint who's going to benefit from a partial knee replacement and who doesn't need one. And if you asked 10 different surgeons, you'd probably get 10 different answers.

When partial knee replacements first came out, there was a famous paper back from 1989. And they said, really, it should only be used in patients who have full knee range of motion. They're older than 60 years old, they're less than 180 pounds, and so on. And ultimately, very, very few patients actually met that criteria. Now, many surgeons, myself included, are adopting a little bit wider or more open criteria. And for me, really the biggest factor is ensuring that the patient's pain is actually coming from the part of the joint that we're going to replace.

So, there are really three compartments of the knee. The inside or medial compartment, the outside or lateral compartment, and then underneath the kneecap, which is called the patellofemoral compartment. And usually, when we're talking about a partial knee replacement, we're talking about the medial side, occasionally the lateral. But I'm really looking for patients who say, I can feel exactly where my knee hurts. It's not all over my knee. It's not really in the back. It's right here. I can point to it." To me, that's a very reassuring sign that the patient is going to benefit from a partial knee replacement. Again, usually, we're talking about a medial partial knee replacement, which replaces the inside part of our knee. And for those patients, I want them to kind of point to that part and, you know, not necessarily feel pain in the front of their knee, especially when going up or down stairs. And x-rays are certainly a big part of this. We can see where their arthritis is. But really, a lot of it comes from my conversation with the patient and my exam of their knee, and what kind of activities cause them pain.

Host: Yeah, it is interesting. As you say, it's such a small percentage, right? And that's probably the best way to understand why I haven't done more of these partial knee podcasts, so I'm glad we're doing this. For me, I sort of feel like, "Well, if you're doing it, just do the whole thing," you know?

Dr. Joseph Serino: Yeah, that's a very fair perspective too. I think a lot of people and surgeons would agree with you.

Host: Yeah. And certainly, I'm just a lay person who has osteoarthritis and whose knees hurt kind of all over. So, I may not even be a good candidate for partial. But I want to have you go through some of the procedure basics and benefits. Like, how does it work, which part of the knee are you replacing? What are some of the main advantages, you know, as we sort of compare and contrast to the total knee replacement?

Dr. Joseph Serino: I think, you know, of course, with any surgery, there are benefits and risks. But personally, I find for the right candidate, the benefits far outweigh the downsides of a partial knee replacement. First, it's a smaller surgery, it's a smaller incision, a faster surgery. So, that means it's a much quicker and easier recovery. But more importantly, there's also a much lower risk of complications, which obviously benefits patients greatly.

But I think the real primary advantage of a partial knee replacement is that we're really only replacing the diseased part of the knee and leaving everything else intact. And that especially means the cruciate ligaments, the ACL and PCL. With a total knee replacement, almost a hundred percent of the time, we're removing the ACL. And I usually try to keep the PCL, but many surgeons end up removing the PCL as well. And that's totally fine in a total knee replacement. But in a partial knee replacement, we get to keep those ligaments. And we keep the native cartilage under the kneecap and the remaining healthy parts of the knee. And what that means is that the knee will move and feel much more like a normal knee than after a total knee replacement. And that's been something that has been demonstrated over and over again in research studies. So, patients are far more likely to be satisfied with their outcome after a partial knee replacement than a total knee replacement

Host: Yeah. As a kid who grew up in the '70s and watched The Six Million Dollar Man, I sort of picture, you know, if I get a new knee that it's going to be like that, like a bionic knee. I can definitely appreciate what you're saying, the benefits of it still sort of feeling and moving like your knee did before with the partial approach, which again, not everybody's a good candidate for, and not every surgeon can do, but we're talking to one who can and who does.

So, let's talk about the surgery, techniques, technology, robots, computer-guided, alignment, all of that. Take us through as best you can without pictures. Take us through the surgery.

Dr. Joseph Serino: Overall, the incision is, like I mentioned, smaller than a total knee replacement. It typically does not disrupt the quadriceps muscle as it attaches to the kneecap, which can help preserve the normal way a knee should move and help accelerate the recovery after a knee replacement. And really, we're just kind of peeking inside the knee and trying to disturb as little as possible while we replace the affected compartment. And you asked about robots. I do often use a robot to assist with this surgery. It's really the one area in knee replacement that's been found to actually really benefit from a robot.

I also use robots for my total knee replacements. And I find them incredibly helpful. But just from a research perspective, the robot has been found to actually improve outcomes significantly with partials. And really, what that helps us do is make very precise cuts and align the implants very precisely so that they move appropriately with each other and they're aligned appropriately with the rest of the knee, because the alignment of both the implants and the size of the implants can really affect outcomes and complications after surgery. So, having that additional precision with the robot I've found is incredibly helpful, although I also sometimes do these surgeries without a robot, depending on the patient's specific situation.

Host: Sure. Right. Sometimes new school, sometimes old school, maybe sometimes a combination.

Dr. Joseph Serino: Exactly.

Host: Yeah. But just undeniably cool how far things have come, and certainly knowing some people in my life who've had new hips, new knees, all of that. It's really amazing. I want to finish up today and just talk about recovery and rehab expectations, right? So, take us through the typical postoperative timeline, a hospital stay versus outpatient, pain management, all that stuff.

Dr. Joseph Serino: The overwhelming majority of these surgeries are done on an outpatient basis, so patients are going home the same day. In terms of pain medications, we use a multimodal regimen of medications, which includes anti-inflammatories, nerve pain medications, and some stronger pain medications, which patients may or may not even require at all. If they do require stronger pain medications, it's often just for a few days after surgery. Patients are up walking, going up and down stairs, the day of surgery usually. And usually, by around six weeks, they've regained almost all of their knee range of motion, are starting to get back into more strenuous activities in terms of just walking longer distances or light exercise, but nothing high impact still until about three months. And at that point, they should be at least 90% recovered.

Host: Yeah. Get back to pickleball or whatever it is people do.

Dr. Joseph Serino: Exactly.

Host: Yeah. Well, it's been so great having you on again. As I said when we started, I don't know a lot about partial knee replacement. I mean, I know what the words mean, but understanding better what you do, how you do it, who's a good candidate, all of that. Good stuff. We have one more we're going to do in the near future. We're going to talk about nutrition and how it helps before and after surgery. So, I'll talk to you then.

Dr. Joseph Serino: Excellent. Thank you. Looking forward to it.

Host: We now have online scheduling. Please visit mdbonedocs.com and click the new online scheduling button to instantly make an appointment. Find out more about us online at mdbonedocs.com. And please remember to share and subscribe to this podcast. And that's all for today. I'm Scott Webb, and that was a bone that's fixed.