Orthopedic surgeon at the Hackensack University Medical Center, Dr. Yair Kissin, MD talks about a new way to perform knee replacement surgery.
Interview conducted by Ivanhoe Broadcast News in 2022.
Can you describe Persona smart Knee and how it works?
KISSIN: The Persona Knee is a model of a knee replacement that comes from a company called Zimmer or Zimmer Biomet. It’s based upon a legacy that is 30-40 years old. That started with a professor named John Insall, who basically designed and invented the original knee replacements back in the 1970s. He then had two disciples immediately after him and then many more to follow. Dr. Michael Kelley, who unfortunately we just lost to prostate cancer and Dr. Norm Scott. In that time they formed a group called the Insall Scott Kelly Institute for knee surgery and continue to develop an innovative knees of all kinds, not just knee replacement. Over the years, there are many different iterations of what this has undergone as far as innovation and technological advances. The latest version is called the persona or personal. They’ve got the sizing very personal to patient’s anatomy by examining the anatomy via CAT scan, not just through a couple of cadavers. They did quite extensive work to make sure that the fit of the implant is correct to patients different anatomies.
Why is fit so important when you’re talking about this joints?
KISSIN: When we talk about what’s important, it is to establish that this knee prosthesis is a good prosthesis and has some track record behind it. One of the main things to get a knee correct is to see that it fits the bone correctly. If it’s too large, because back in the day I was told I wasn’t around for this part yet already because they had innovated beyond it. There were two sizes and many times the bone would be dwarfed by the metal implant. Patients still somehow did okay, the human body has a way to adapt, but it certainly wasn’t perfect. Over time they got the fit to really be correct to the patient’s anatomy. If it’s too big, there can be metal that is overriding the bone and it can affect the soft tissues and irritate the soft tissues. If that fit, we’re already putting in a giant metal implant as far as the body thinks, and if we can make it less giant and more form fitting to the patient’s anatomy, it’s going to be a better outcome. We want the knee to be balanced and moving correctly, but fit does matter.
Can you describe for me how you go about finding that perfect fit that Persona the personally?
KISSIN: We are in the midst of trying to figure out how to make it even more perfect. Because remember that knee replacement is probably the most successful operation we have in our armamentarium of all of medicine. It’s an operation we can identify a problem, cut it out, put new parts in, and do that almost a million times a year successfully with over 90 percent success. Not many other parts in the body are done successfully in those numbers. But there’s still a bulls eye that were not quite hitting. We say there’s a 10-20 percent group of patients who are not satisfied with their knees. We still have not quite gotten the entire holy grail just yet. How do we do it? Over the last few years, we’ve added robotics, we’ve added technology. There is a movement of virtual reality or augmented reality that’s making its way into the operating rooms. Technology, mostly robotics today is perhaps helping us fit that knee not just to the bone itself but also to the knee itself, as far as not just a static image. We don’t just want an X-ray to look good, we want the patient to function well. We’re getting all assessment tools to figure out what that actually means because it’s certainly debatable and not two surgeons will agree on what the goal is necessarily. So there is still a lot of interesting debate going on on the right way of doing a knee, and we’re using some technology to help us.
Can you walk me through what you need to do to get to the point where the patient has this knee replacement? Is it a matter of scans, measures?
KISSIN: I see patients of all kinds, of all ages, of all different conditions and degrees of conditions. Just because someone has arthritis doesn’t mean they need a knee replacement. There are degrees. I’ve certainly seen arthritis that’s not awfully severe, hurt very severely. We put the two and two together. Patient comes to see me, we’ll always try, we’ll assess them, we’ll listen to them, we’ll take some x-rays, then we’ll have a conversation. Almost always the first conversation is not about an operation. Once the non-surgical things that we have in our toolbox, physical therapy, weight management, injection or an operation which would be the next steps, we have all things in-between that once a patient has decided that their knee is making their life not as happy as they would like it to be. There must be some form of dysfunction or some things on their list that they cannot do that they want to do. When a patient is not happy, as long as the X-rays agree. Patients need to understand this is major surgery, and there needs to be a major delta between the pre-op and post-op or we cannot do it. If someone has little dysfunction and not a lot of arthritis, we’re going to try other things first. But once the X-rays show bone on bone arthritis it means there’s no more space and that’s when we can have this conversation. This is because that’s when it helps patients is to actually do it that way.
Once a patient qualifies, can you again walk me through the steps?
KISSIN: Depending on how freaked out the patient is by the concept of needing surgery, I will certainly cater the conversation to them. Some patients want to know details. I tell patients either way, it is a big surgery, there can be complications of anything one can think of. Luckily, at a center like mine and with experience, we have fewer complications. We know that surgeon volume, hospital volume, we’re doing a good job. Once I can convince a patient that they can be confident moving to the next step, I tell them basically what we do is make sure medically you’re okay. You have to make sure your doctors who know you, evaluate you and that you’re safe for surgery. We’re very big on optimization of patients. We don’t take a patient to the operating room who are not taking care of themselves. We want to make sure they’re safe. Then we talk about the surgery. And the surgery itself, I explain to them there’s an incision down the front of the knee that’s usually from the top of their kneecap to just below their knee joint. Depending on the size of the patient and the patient’s knee, that’s where the incision is going to be a little variable. Somewhere in the four to five inch range for most patients. Cutting out the arthritis and putting parts in that are replicating the patient’s anatomy but made out of metal and plastic parts. Then we close everything up.
The procedure is fairly similar to what you’ve been doing all along, what’s the new hook that got there?
KISSIN: Depending on what kind of technologies, the principles remain the same. As long as we’re maintaining our principles in using new technology, that’s really the key on how we’re going to get to the next level. Whether we’re doing robotics, something has to cut the arthritis out. At the end of the day, the X-rays look the same if it’s done robotically or not. Then, now what we have available to us and only with this particular model of knee is something called a smart knee or the persona IQ. This is something we haven’t had at all in any of the other implants. It just so happens that this is the one I’ve been using all these years and I’m most familiar with. This is basically a small addition that gives you a Fitbit inside attached to your implant. They’ve tried using Fitbits or Apple Watches. Those kinds of things are inherently hard to track because 30-50 percent of patients didn’t use it right or the battery died, or they left it at home. This stays with you and it comes with you everywhere you go. Patients will now get a dashboard of their activity, six different gait parameters. They have full access to their dashboard to see how well they’re doing. Which is a twofold advantage that we’ve never had before. It tells us if the patient is doing well. This will take time because we just started amassing this information. We have some ideas of where we would want patients as far as their steps, distance walked, and and range of motion while they’re walking, but we’re going to understand this a lot better soon. Maybe there’s a different way where some surgeons do a knee a certain way. That’s the hope. But on the other hand, we’re also going to know if patients are not doing well. Perhaps at some point you see their parameters dropoff and you get an alert. You may know sooner than they know that something’s wrong.
Does it monitor more than the gait and the function, or the key things that you were looking at, how it’s working?
KISSIN: Early version and this is FDA-approved. This is not experimental, but the earliest version of this measure six different things as far as the gait goes. Distance traveled, number of steps, cadence, stride length, and speed. For example, we know that a normal speed of walking is 1.2 miles per hour and if we find out that doing a knee certain way gets the patient to that speed of walking sooner, that’s important. If in the first four weeks, 80 percent of patients done this way achieve a normal walking speed, that means they can go back to their lives. It has implications of returning back to normal. Then there is range of motion while walking. All of these things are going to be parameters. I think there’s more to come. I don’t think they’re done here.
Does this smart peace ever come out and how does it recharge because after a while?
KISSIN: This technology is based upon pacemaker technology that gets implanted in a person and stays there for 10-20 years. Basically it comes with its own battery and just like any technology can have malfunctions, it can too. But in general, the majority of these are working once you implant them. They don’t need to come out unless the knee needs to come out. If there’s a complication,fracture around the implant, a major trauma or a fall, or a revision surgery then, it might have to come out.
How is it a benefit to you, doctor? Can you see that a patient will need a revision way before they either would feel the pain or, are you able to measure from the dashboard what success looks like for this patient?
KISSIN: I don’t know that we’re quite there yet. I think I would imagine that once we have objective data that we’ve never had before. If a patient comes to see me and their PT note looks like everyone else’s PT note, it says they’re hitting these and these milestones, but PT notes are subjective. They’re not very objective. Here we can look at the dashboard and say you’re doing great. At the four-year mark, we can say at three years you are doing great. Then we may need to investigate and do some tests. Then maybe with that, we find out that something is wrong with it. Maybe it needs an operation earlier than we would have found out if we didn’t have these points of data.
Do patients feel any difference? Is surgery done differently?
KISSIN: Surgery is done essentially exactly the same. We do have to put this additional piece in there, which is called the stem. But we put stems in our knee replacements at times when needed for poor bone quality or for obese patients. That’s not really a new onset all. The patients who’ve signed up for this are patients who are motivated and they want to do well. I think that having that information is a very important piece. I don’t love my Apple watch, but I do like to know that I’ve done over 10,000 steps. There is something about those little achievements that mentally lets you know that you’ve hit certain marks. We’re all trying to be healthier. We had a run of a few years of being pretty unhealthy, very sedentary. Everyone gained some weight and everyone got less healthy. Now, I think people are back to their lives and trying to get back to that. Tto have a dashboard of information that we never had before related to a major operation you decided to do. I think that’s a big deal. It’s like having a speedometer, but a lot more than that.
You mentioned FDA-approved. So this is out of a clinical trial?
KISSIN: This is out of a clinical trial, absolutely.
Is there anything I didn’t ask you that you want to make sure that people have?
KISSIN: I think two things. One is, this is going to give us a plane of data. An entirely new era of data that we’re going to be able to glean some studies from. We have a new medical school in our inner Medical Center. We have a new residency coming in our medical center for orthopedic surgeons. We need research. It is very easy for us to say the way I do a knee replacement is the best way. We all think that. We’re going to find out, I think, and be able to prove that maybe someone is right. I think this is going to give us information that we never had before. To be able to show that, and not only show that by showing it in short-term. It takes five years to get midterm data on something and 10 years to do long-term data. I don’t want to do robots for 10 years and not know that it doesn’t have a benefit for patients. The second thing I think that this can allow us to do with the advent of telemedicine with COVID being quite popular. What if a patient’s doing just fine and there’s nothing? I feel bad when a patient comes to see me after their four-year follow-up and they have a long trip home. Whereas here we can have a true telehealth visit with the patient where their knee is going to talk to us too. We’re going to be able to tell people they can skip a year and see the patients that truly need me in office.
Have you seen patient benefits and patient improvements?
KISSIN: It’s too soon to say and I think the improvements are going to be largely mental right now because they’re going to see how they’re doing. If they’re doing well, they’re going to feel well. Tthen incrementally as we get more information, we will be able to tell peoples percentiles for their recovery time.
Can you tell me just a little bit about Raymond? I understand he has another replacement coming up.
KISSIN: Raymond is a 61-year-old, very active, very healthy male who came to me. He needed both knees done. He decided to do them one at a time. He is coming up for his second side just next week. His first side went extraordinarily well and he’s doing very well. We know that by him and his knee telling us. He came in with bone-on-bone arthritis of both knees and aked me what his options were. He had already heard about knee replacement. He had not heard about the smart implant yet. We had that discussion and he struck me as someone who’s interested in knowing how well he’s doing. It was a very easy conversation. I think the most important message patients need to know, this is not a tracker, it is a sensor. This lets us know how your knee is doing. No one knows where you are except you.
Can you walk me through some of the parts?
KISSIN: Here what I have is a traditional knee replacement. In general, it’s three parts. One is a shape of the end of the femur or the end of the thigh bone. This is one before it’s cut and then we cut the arthritis out and shape a new femoral component on that’s the top of the bone. Then on the bottom side is called the tibia or the shin bone where we cut out the arthritis, put a metallic plate with a plastic piece and those two coupled become your new knee replacement. That’s a general knee replacement. The smart knee is an implant that gets attached like a stem or a little rod that goes down into the bone. Deep into the bone and gives it a little potting a little. In patients who have poor bone quality, we might do something like this anyway. Certainly when we’re doing revision knee replacement where we’re redoing a situation where a knee failed. We’ll also use stems in general, this is not an unfamiliar part of the surgery. That is the smart knee. It gets implanted so your patient doesn’t feel it and doesn’t know that it’s there. There’s a plastic piece inside a metal piece.
And there are dashboards that show you what?
KISSIN: We can log in online. We can see a patients log this out as soon as we wanted it. What happens is it says when he had his surgery and it lets us know his steps overall. Basically what you do is you find out what’s going on, how are you doing, and stride length.
END OF INTERVIEW
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