Latest advances in partial and full knee replacement surgery.
Dr. Mehul Shah & Dr. Ivan Fernandez Madrid of NYU Langone Health's Department of Orthopedic Surgery unravel the mysteries of knee replacements, from the different options for partial replacement, to full replacement. From novel robotic surgery techniques to conversion from partial to full replacements, hear the latest advances in surgery as well as recovery and rehab.
Narrator: SiriusXM presents an NYU Langone Orthopedics podcast. Orthopedics is just very important to the population in this country. Its ability to restore patient function. Problems related to cartilage, to someone who has more advanced forms of arthritis. Getting people back to their activities and the things that they like to do. Featuring NYU's experts in the field of orthopedics trying to figure out that problem before it even is a problem. Problems with solutions. Well beyond physical therapy, to conservative pain management, to surgery. The best medical minds now come together. Applying all of our minds to solve these problems. We're here to get people feeling better so they can get back to their lives. And that's really what we try and accomplish. These are the Bone Whisperers.
Dr. Mehul Shah: All right, welcome. You are listening to the Bone Whisperer podcast, brought to you by NYU Langone Orthopedics and NYU Langone Health on SiriusXM Radio. I'm Doctor Mangal Shah, and today's episode is titled, what is the difference between partial knee replacement and a full or total knee replacement? And we are talking with my friend and colleague, Doctor Ivan Fernandez Madrid. Doctor Madrid is an assistant professor in sports medicine, arthroplasty specialist here at NYU Langone Health, who has a particular interest in knee arthroplasty, both partial and total knee arthroplasty. And Ivan was a young attending when I was in training here at NYU. And, uh, now we're both sitting here a little bit gray in the beard and long in the tooth. And Ivan, it's a pleasure to have you here.
Dr. Ivan Madrid: Thanks, Mehul. Really appreciate it. I'm happy to be speaking about something that I'm really partial to… partial knee replacement.
Dr. Mehul Shah: Haha no pun intended. Right. So this is always a question I get in the office when I don't do knee replacements. I recommend people for knee replacements sometimes, and they're sort of in shock, you know. Oh, I need a knee replacement. Uh, it has to be a completely replacement, can be a partial knee replacement. So hopefully today we can illuminate our audience on this topic and educate them on partial knee replacements. So just taking a step back before we talk about actual joint replacements, what is exactly for our audience, knee arthritis? And when do we start considering these knee replacements?
Dr. Ivan Madrid: So that's a great question. It's a question that we talk about all the time in the office. So arthritis is one of those things that we use that word and we throw it out frequently, but it's sort of like saying headache - arthritis is really a symptom. But I think what most of us mean when we talk about arthritis is we talk about sort of the degenerative changes that occur in the knee joint. We have cartilage that covers our bones at the end of the joints. And I think the analogy that I use for patients is, I say if you buy a new pair of shoes, you wear those pair of shoes every day, the sole of the shoe wears out a little bit, and that's kind of what happens to the cartilage cap inside of our knee. And I think that's what we normally refer to as arthritis, uh, that sort of wear and tear arthritis that we have.
Dr. Mehul Shah: Right. So when we're born, you know, our joints are all covered in this nice, smooth cartilage, and then when it gets worn out, then there's a lot of friction and pain in the joint, and then we talk about replacing. So what are we actually doing when we do a joint replacement? What are we replacing? I think people think that we just chop out, you know, we cut in the femur, we cut in the tibia, we remove it and block and give them like a metal, you know, sort of like a Terminator-type knee. So what exactly are we doing to replace them?
Dr. Ivan Madrid: Right. So I think the word knee replacement is probably not a perfect word. We should use the word resurface. So what we end up doing is we resurface the ends of the bones that have worn out with metal and plastic. We don't really have the technology yet to totally resurface the joints with biologic tissue, so we have to replace it with metal and plastic. So it's really sort of resurfacing procedure.
Dr. Mehul Shah: When we insert these things and we fix them to the bone with either bone cement, or now, newer technology is we actually have the bone sort of cementless sort of techniques, right?
Dr. Ivan Madrid: Right, so we usually the traditional way of doing any kind of replacement, either partial or total, is to use bone cement that basically glues the implant to the bone. There are some newer technologies where the surface of the implant is roughened and the bone actually grows into that and grabs onto that, ostensibly or hopefully for that to have a longer lifespan of the implant.
Dr. Mehul Shah: And what do you say to people about, do they think this is going to be their cure all? Especially in the younger patients? Knee replacements don't last their lifetime, right? What do you typically tell them? What can they expect?
Dr. Ivan Madrid: So I think that the knee replacements are really good options for patients. It has to be done in the right setting. I think the life expectancy of a knee replacement is on the order of 10 to 15 years. So I usually tell people, if you have a knee replacement in your seventies, it's unlikely that you're going to have another one. In your sixties, you might have another one. In your fifties, you'll probably have another one. And if you're in your forties, when you have your first one, you'll definitely have another one. I think that's one of the places where partial knee replacements are a really good option, because I see it as an early intervention where you can then sort of postpone the time for your first knee replacement.
Dr. Mehul Shah: Okay, so now when we talk about the differences between, you know, uni-compartment or partial knee replacements and total knee replacements. What exactly is the difference? What are we doing differently in a partial knee replacement? What are we keeping? What are the differences?
Dr. Ivan Madrid: So when we do a total knee replacement, we basically resurface the entire surface of the joint. And actually, most of the implants that we have will actually cut out two of the normal ligaments that we have inside the knee. And so the stability of a total knee replacement is significantly different than our native knee. So that's one of the advantages of a partial knee replacement, is that when you do a partial knee replacement, you're only resurfacing the part of the knee that has gone bad, and you preserve particularly the two cruciate ligaments that are in the knee. And so the function and the way the knee moves and the way the knee feels is very different with a partial knee replacement.
Dr. Mehul Shah: So there are different types of partial knee replacement placements, right? So, in general, I think we talk about the knee has three compartments, right? There's one on the inside we call the medial compartment, the lateral side, the outside, the knee, the lateral side, and also the patellofemoral. Right? So what are the different types of knee partial knee replacements, and…. what are the different types of partial knee replacements?
Dr. Ivan Madrid: So there are, like you said, basically three different types of partial knee replacements. The most common is the medial or inside part of the knee. The least common is probably the kneecap part, the patellofemoral portion or compartment, and the lateral is also a little bit less common as well. So, basically, when you look at arthritis, a lot of times the alignment of your leg is going to dictate which part of the knee goes bad. And so most of us have a little bit of what's called a bow legged alignment. And so that's why the medial side is usually affected. But sometimes trauma and other things can affect different parts of the knee joint. And so you might have to do one of the different compartments. But the medial compartment is basically replacing the inside part of your knee. The lateral is the outside, and then the patellofemoral is the kneecap part.
Dr. Mehul Shah: So when you see patients in the office with knee replacement, I'm assuming the vast majority of patients that you see aren't really, you know… total knee replacements are much more commonly than unicompartmental knee replacements. But what percentage of patients either come in asking for partial knee replacements and who are actually good candidate? Like, what percentage of patients would you say would be good candidates for knee replacements?
Dr. Ivan Madrid: That's a very good question. I think one of the hardest things that I have as a surgeon is to figure out who the right person is for or a partial knee replacement. Because you want to be able to do a surgery that has a good pain relief for long period of time. So you don't want to do a surgery and then have to do another surgery to fix any problems that might occur. So I would say probably somewhere between 10 to 20% of the patients that come into my office are candidates for partial knee replacements. There's a fair number of people that actually come in requesting partial knee replacements, but for many factors aren't really candidates. I think that the idea of a partial is - a partial is to try to maintain function and to try to maintain activity. And so one of the problems is, a lot of times, people, when they have arthritis, they have a lot of limitation of motion, or they're very stiff, or they have an alignment, they have a bowed leg. And partial knee replacements really are not for that. I think partial knee replacements are for people who have really good range of motion, they have normal stability, and they just basically have pain on a very localized part of their knee.
Dr. Mehul Shah: So there are certain things that make people good candidates for it. And who would you say you would exclude? Like, people who, just because of their medical conditions or maybe age or what are things that you would say are contraindications for partial knee replacement?
Dr. Ivan Madrid: So there are absolute sort of contraindications, and I think if people have instability, I think it's a problem.
Dr. Mehul Shah: Meaning, like, if they, like, tore their ACL in the past or something like that?
Dr. Ivan Madrid: Yeah, I would think that if they have persistent instability, sometimes people who tore their ACL in their past have compensated, and they actually have some stability. And if they don't have, as, you know, like, a pivot, if there's no pivot when they are examined, I wouldn't be totally uncomfortable doing a partial but that's sort of a relative contraindication. Another one that I think is a bad idea to do is people who have inflammatory arthropathies, things like rheumatoid arthritis and lupus. Those are the kind of things that I really think you shouldn't be having a partial because the disease process that's affecting your joint is still there, and it's not being corrected by the partial knee replacement. Another one that's an interesting one, I think, is age. I don't really have an age cutoff. I really have a physiologic function cutoff. So there's people who are older and have very localized disease and would be really good candidates for partials, and then there's others that are younger and may have a lot of stiffness and pain that wouldn't make them good candidates. So I don't really have an age cutoff. I really have a function sort of cutoff and activity cutoff. And that's how I usually make my decisions.
Dr. Mehul Shah: So they have to have focal disease, right. They can't have - you can't do a uni-compartment or, uh, replacement if they have degenerative changes in all three compartments. Right. But commonly, we see people who have sort of predominantly - in my practice, I'll see people with predominantly pain on the inside of their knee. I get an x ray. There's significant joint space narrowing there. Otherwise their knee's feeling fine. But I get an x ray, and underneath their kneecap, there's a little bit of wear and tear. You know, that's pretty common to see. Now, is that person a candidate, in your opinion, for a knee replacement or, sorry, a partial knee replacement? Or is that someone who you would say, hey, listen, I know it's not bothering you right now, but we might as well do, uh, a total at this point.
Dr. Ivan Madrid: So I think that that is one of the problems that I think is difficult in deciding when to do a partial or not. I have a couple of physical exam things that I sort of make a decision about. I also have some questions that I ask the patients to determine whether it's important or not. So if people have localized pain and they point to the inside part of their knee, and they don't have really pain in the front of their knee, and they don't really have pain going up and down stairs or getting up from a chair. And then when I examine them, if I test the kneecap joint, and it doesn't have significant discomfort or pain elicited with, like, a patellofemoral compression test, then I'd be inclined to still do that, even though they have some changes on the x ray preoperatively. Sometimes MRI is are helpful in looking at it. But one of the things that I actually do for every patient that I've talked to about partial knee replacements is I consent them all for a possible total knee replacement. Just because if you're planning to have a partial knee replacement and you open up and the kneecap looks terrible, or there's a large arthritic lesion on the outside part of the knee that I don't think that a partial is going to give them long term pain relief, then I think it would be a mistake to do a partial. There are people who say, listen, I do not want a total despite what you find. And so if that's a dialogue that we have with the patient, then I'll just do the partial. But in general, I tell people, listen, if I find something intraoperatively that needs to be a total knee replacement, then we have to proceed with that. That's a very uncommon occurrence. I would say that I've done over 500 partial knee replacements, and I think that's happened five times.
Dr. Mehul Shah: Right, okay, so 1%. So again, though, so you talked about basically, like, we're preserving their cruciates, and one, does that mean the patient feels that their knee is more like their own knee? And I guess the other question I have is, are there any activities that you allow your partial knee replacements to do that a total knee replacement you won't allow them to do? Like, a common question we have is, like, running. Can I run after a knee replacement? What do you tell these kinds?
Dr. Ivan Madrid: So I actually don't really restrict patients after replacements.
Dr. Mehul Shah: Ether one?
Dr. Ivan Madrid: Either one. Because I think that total knees self restrict themselves because I think they have some functional limitations and it's very person-specific. There's people who are capable of skiing, there's people who are capable of running. Most, uh, people with knee replacements don't feel the same stability, so they sort of self limit, and they can jog and they can play pickleball and things like that, but they have less ability to play cutting sports. Having said that, I just this past week saw a patient who is in his early fifties and still plays basketball with a total knee replacement. So I think that's very patient specific. But a partial, the advantage is that because you preserve all the ligaments of the knee, particularly the cruciates, because it's a smaller operation and a little bit easier to recover from and faster to recover from. They usually end up having far better range of motion than people with total knee replacements. I'd say on average, a full knee replacement, people can get maybe 115 to 120 degrees of motion. That's a very good result with that. And partials usually are able to maintain, you know, if their body habitus allows, you know, 100 and 135 degrees of motion. But most people with partials will say it feels like a normal knee. It doesn't feel they have the instability, it doesn't feel different to them. Whereas total knee replacements, people, it doesn't feel functionally the same like they do with a partial.
Dr. Mehul Shah: So we talked about the advantages of partial joint replacements. What are the potential disadvantages? What do you tell your patients that could be some hiccups or, you know, bumps around the road?
Dr. Ivan Madrid: So that is, I think, the fundamental question with deciding who to do a partial knee replacement on and who not to. So one of the problems is I don't have an ability to tell you how long your partial knee replacement is going to last. So when we do a partial knee replacement, the implant that I put in is definitely going to last just as long as a total knee replacement, you know, 10-15 years or more. The problem is, the rest of the knee may not last that long. And so the process that occurred on the portion of your knee that went bad is continuing in the other parts of your knee. I look at a partial knee replacement as sort of an early intervention to allow good function, and the idea that a partial is going to allow you to do all the activities that you want to do, hopefully for an extended period of time. I usually tell people that if they're in their forties and fifties, they get a partial knee replacement. You're delaying the time until you get your total knee replacement. However, it's sort of unpredictable to say if it's going to be in five years, in seven years, or in ten years, and that's going back to the age thing. That's one of the discussions that I have with the older population who might be candidates for a partial. It's a discussion that I have to have to say, listen, right now you're a perfect candidate for a partial, but I'm not sure if in five years or in seven years or in ten years, you might need to have it converted to a total.
Dr. Mehul Shah: Interesting way of looking at it -it's not that the unique compartment lasts less long, but the rest of your knee may continue to degenerate. How are the revisions of…. so say we know, knee replacement and I think you're using a very conservative number, 10 to 15 years. I think more recent data that I've actually sort of read or perused would be that 90% of the knee replacements we're putting in now last almost up to 20 years. So maybe these knee replacements, the total knee replacement, maybe even lasting even longer. When you revise these unis to totals, is that a harder revision? Is that an easier revision? One of the things we worry about when we do revisions, or you guys, because I don't do joint replacements anymore, is bone loss, right? You only have so much bone stock to support these knee replacements before you have to do other things to support it. When you revise it, you're obviously taking away more bone. Is it converting a uni replacement or a partial knee replacement easier than converting a total or revising a total?
Dr. Ivan Madrid: So that's a very good question. There's a couple of points that I'd like to make about that, but number one, the conversion of a partial to a total is easier than doing a total to another total. So, in my mind, I would prefer to revise a partial to a total. Now, it's nothing exactly the same as doing a total, but it's pretty close. And the second thing that I wanted to say about that is, most of the time, not most of the time, actually, all of the time, we use this robotic technology to put these implants in. What the robotic technology allows us to do is to customize the implant, and it actually minimizes the bone resection, so the amount of bone loss is a lot less. And so converting it from a partial to a total, when you've used the robotic system, allows you to sort of minimize the bone loss. So you don't really have to use a lot of reconstruction to techniques like stems and wedges. So you can usually convert it to a primary total knee replacement, which, functionally, is usually much better for the patient. And actually, recently, I've been doing the revisions using the robotic technology as well, which makes it a lot easier and a lot more precise.
Dr. Mehul Shah: So, let's go into this robot. So what exactly is a robot? You know, there's not, like, Robocop isn't standing next to you and doing the joint replacement with you. When we use the term robot, what exactly are we talking about?
Dr. Ivan Madrid: So, orthopedics actually has a fair number of robots made by multiple players in the industry. In general surgery I think the most common robot is the da Vinci robot, which is actually not really robotic. It's more like remote controlled surgery. That's not what we use in orthopedics. In orthopedics, we have a robot which probably the most common is Stryker Mako robot. And what that is is a robotic arm that has a saw attachment to it. And basically, we get a preoperative study, a CAT scan, that then gets the three dimensional view of the patient's knee. And then we plan the surgery based on that three dimensional image. And then intraoperatively, this robotic arm, guided by us, held by us, will precisely make the cuts for either a total knee replacement or a partial knee replacement. Actually, with a partial, we use a saw and a little burr that minimizes the bone resection. But basically, it's a robotic arm that we use intraoperatively to make extremely precise cuts. And what the technology allows us to do is it allows us to customize the implants to fit the bone perfectly and to fit the ligaments perfectly as well.
Dr. Mehul Shah: Now, is there ever time you need to, like, override the robot or say, ah, it, ah, doesn't look so good.
Dr. Ivan Madrid: So the robot is not an independent entity and doesn't have any, it doesn't work on its own. So it only works if the surgeon - it's this thing called haptic guidance, which means that it can only cut where the surgeon cuts. So there's no independent action of the robot.
Dr. Mehul Shah: But when they're directing you to cut these things, have you ever had to, say, deviate from the plan? Is that a common thing or is it an uncommon thing.
Dr. Ivan Madrid: So it doesn't direct you in any way. So the plan is made by the surgeon, and then the cuts are only allowed by the. By the….
Dr. Mehul Shah: I get it. But, you know, you have that, you plan these cuts on a computer, right? And then sometimes that may not or may always translate to reality. So I'm saying is sometimes those plan cuts on the computer, do they ever not show up in reality?
Dr. Ivan Madrid: That has not occurred. It's very, very accurate.
Dr. Mehul Shah: That's good. That is very, very, very interesting. Um, and I guess there are other alternatives to uni-compartment or partial knee replacements. What are the other alternatives, especially in maybe a very active person or a very young person? Is there anyone too young to even consider a partial knee replacement? And what would you do in those sort of situations, if necessary?
Dr. Ivan Madrid: So I think that there are some other surgical alternatives. I think, for instance, there's a type of operation called an osteotomy, which basically is a realignment procedure that is used to unload a particular compartment, like the inside part or the outside part. I've had this discussion, and a lot of times in meetings there's discussions as to which one you should do a partial knee replacement or an osteotomy. And I think that they're not really the same population that are good candidates for that. I think that the younger you are, the more active you are - people in their thirties and maybe early forties - I'd be more inclined to potentially use something like an osteotomy a little bit. If you're in, you know, forties and fifties, then I'd probably be less inclined to talk about osteotomies. It's a hard sell to do an osteotomy because people, the recovery is very different. An osteotomy is you're going to be on crutches. You know, people hear you say, we're going to cut your bone and realign it, and they freak out a little bit.
Dr. Mehul Shah: That's a scary thing.
Dr. Ivan Madrid: And a partial knee replacement is a lot easier. People come in at two weeks and, you know, they're usually not using any assist device. They have, you know, good function. They walk home the same day. I have a surgeon who I did a partial knee replacement on, and he worked the next week after his partial knee replacement. So it's a very different sort of recovery. I think that there are activity levels that I would say if you're very young and have a very high impact type of either job or sport or something like that, I would probably say you should opt for an osteotomy before doing a partial. And then doing partials after osteotomies are certainly an option.
Dr. Mehul Shah: It's complicated
Dr. Ivan Madrid: But they're a little bit more difficult.
Dr. Mehul Shah: For sure. These osteotomies are more in the sports medicine world where I live, where we're sort of more on the joint preservation side of things. And we do things like cartilage procedures, or even we do things like we take cadaver bone and cartilage and put it into place. But when we talk about this joint preservation osteotomies to unload, really, it's telling them it's going to be a bridge. At some point in the future, you're going to need one of the replacements, whether it's a partial or a total. Typically, you're talking to someone in their twenties and thirties where you don't really want to start taking away bone. And I guess my last question I say would be there's three compartments in the knee per se. Do you ever do, like more than one of these? Like do you not do three and you just do two?
Dr. Ivan Madrid: So that's an interesting question. When this robotic technology called the Mako came out many, many years ago, I think it was twelve, it started with a partial knee replacement as the only option before their total knee replacement came out. There was an option to do a inside part of the knee or medial compartment arthroplasty, and you could do a lateral if you needed, or a patellofemoral, so you could do them all independently, and we call that a bicompartmental arthroplasty. There was also another company that had made a partial knee replacement that just included the inside part and the patellofemoral, which was this implant called the Deuce, um, which really didn't do so well.
Dr. Mehul Shah: Great name.
Dr. Ivan Madrid: Not sure who thought of that, but.
Dr. Mehul Shah: It wasn't that smart.
Dr. Ivan Madrid: So there is an option to do that. I've actually had a few patients that I did a partial medial on them, and then six years later they had some kneecap arthritis and I did a patellofemoral. I have a couple other patients that developed lateral compartment disease where I've gone back and done a lateral and they've been happy so far.
Dr. Mehul Shah: And that was just a shared decision?
Dr. Ivan Madrid: Yeah, those were people that were really adamant about not having a total. I would say that if it was my surgical judgment and my decision making, I would advise if they have bicompartmental disease, I would tell people to have a total. I think that it's a more reliable pain-relieving thing rather than doing the bicompartmental. It's possible in the future, maybe with implant design and things, that, ah, doing multiple partials might be better, but at this time, at least in my mind, I don't think it's a great idea. When you go to meetings, there are people who do that all the time, and it's not - there are people who do a lot of that. But I personally think that if you have multiple compartments involved, I just think it's better to do a total.
Dr. Mehul Shah: Well, Ivan, I think the you know, this podcast come to a close and I had a really great time. I think this was really informative, and I hope you had fun too.
Dr. Ivan Madrid: I had a lot of fun. Thank you. I appreciate it.
Dr. Mehul Shah: To our listeners, I hope we educated you a little bit on the difference between total and partial knee replacements. Have a great day.
Narrator: The Bone Whisperers is a co production of NYU Langone Health and SiriusXM. The podcast is produced by Scott Uhing. Sound design by Sam Doyle. SiriusXM's executive producer is Beth Ameen, and senior operations manager is Emily Anton. Narration and additional sound design by Michael Luce. Don't miss a single episode of the Bone Whisperers and subscribe for free wherever you listen to podcasts. To hear more from the world-renowned doctors at NYU Langone Health, tune in to Doctor Radio on SiriusXM on channel 110 or listen anytime on the SiriusXM app. For the Bone Whisperers podcast, I'm Michael Luce. Join us next time for the latest advances in orthopedics on the Bone Whisperers.