Selected Podcast
Optimizing Outcomes in Total Knee Arthroplasty
Matthew Beal MD discusses total knee replacement. He shares what conditions can complicate a primary knee replacement, when it should be considered and what is unique about what Northwestern Medicine is doing to optimize patient outcomes.
Featured Speaker:
Matthew Beal, MD
Matthew Beal, MDs Focus of Work is Hip and Knee Replacement Surgery, Revision Hip and Knee Replacement, Patient Specific Total Knee Replacement and Partial Knee Replacement. Transcription:
Optimizing Outcomes in Total Knee Arthroplasty
Melanie Cole (Host): Welcome. Today, we’re talking about total knee arthroplasty, and my guest is Dr. Matthew Beal. He’s an associate professor of orthopedic surgery at Northwestern Medicine. Dr. Beal, what a pleasure to have you with us today. Give us a little bit of a brief overview of total knee replacement and when it should be considered.
Matthew Beal, MD (Guest): When you talk about patients wanting to have their knee replaced—and that’s the first thing—I think a lot of times patients are considering, but they’re not yet ready, and I think a lot of the primary care doctors, I think, some of the things that they could do to help themselves would be, you know, the first thing that I always do is get weight-bearing X-rays. So, we get films with the patient actually standing up so that you can see what does their axis look like? What does the wear look like in their knee when they’re actually putting weight through their knee? I think one of the common things we see is that people get non-weight-bearing X-rays and the spaces between the femur and the tibia actually looks pretty good, but then you have them to stand up, and that space goes away pretty quickly just because they’re bearing weight, but I think when you see that on a plain X-ray before you order, you know, MRIs and CT scans, that’s probably the number one thing that when people show up, that’s what they—that they look like when they’re ready for a knee. I think the obvious reason why we do it—we do it for pain. If your knee hurts, and you failed a few non-operative measures, that’s usually when people start to think about surgery when they’re still, you know, reasonably uncomfortable despite some of these other things that folks will try.
Host: Well, thank you for that. So, what conditions can complicate the procedures that you’re considering, whether it’s obesity or if they have any comorbid conditions. Speak about some things that can complicate what you’re going to do.
Dr. Beal: So, I think all surgeons these days, including me, look for the general medical issues that can complicate surgery. This is elective surgery. That’s the most important thing to remember. We’re not talking about life-saving surgery. We’re talking about a quality of life surgery. So, you really want the patient in the best medical position when they go through this surgery. So, a lot of the things that we see—we do see obesity as being a big problem. There’s pretty good data from multiple different places that looks at BMI as a risk factor. Most centers across the country will set a BMI cutoff and our place looks at 40 to 42 as being the number that above which you usually have more problems after surgery. There are some centers that even go down as low as 35 for their high limit for their BMI. So, weight plays a part in it, but it’s also weight with other things. So, it’s diabetes. It’s blood pressure control. It’s smoking. All those things, when you start, you know, stacking them on top of each other, makes the risk for the patient a lot higher for not only surgical complications but medical complications after an elective surgery. So, it makes a surgeon think long and hard about performing that joint.
Host: Tell us some of the most innovative technologies that you use these days. What’s going on in the world of total knee replacement?
Dr. Beal: So, there’s a lot of things that are out there. There are robots. There are special guides. I think they’re all getting at the same thing, which is we know that we’d like to improve the alignment of the device to improve how long it will last for the patient as well as just the overall feel of the knee so that the patient actually reports that the outcome is good. So, there’s different ways you can do that. So, there are robots from multiple different companies that are available that use imaging beforehand, either a CT scan or an MRI of the patient’s knee to choose the axis of the extremity. So, if you can imagine you draw a line from the center of the hip to the ankle, and you’re trying to make that a neutral axis. So, in carpentry terms, that’s trying to make, you know, the line plumb. You use that imaging to essentially set that axis and then the robot will keep you in that frame when you’re operating. So, in other words, you can’t drift as the surgeon outside of what you have predetermined as the acceptable alignment for that device. So, that’s one way of doing it. That requires a little bit more intraoperative work because you have to have a robot. You have to show the robot where the patient is. You have to show the, you know, robot where the patient’s anatomy is. So, it takes a little bit longer. Some surgeons are switching to things like what I use, which is patient-specific guides. Those guides use the same sort of imaging technology, whether it’s a CT scan or an MRI to again look at the axis of the extremity, and then those guides are specific to the patients. In other words, they fit on the ends of the bone onto the femur and the tibia to predetermine the cuts of the knee replacement as well as the sizing. So, it makes it a little bit more accurate and a little more precise, and that seems to be pretty helpful for folks, when they’re, you know, especially in the United States, majority of knees are done by folks that do less than 50 a year, and it seems to improve the quality and the outcomes for the surgeons that don’t do as many of them.
Host: Sounds a bit like using a level so that it really holds it where you want it to go. Now, tell us a little bit about some technical considerations that you might like some of those providers that are not doing quite so many as you do—do you have any technical advice for them?
Dr. Beal: Well, I think you have to consider the axis of the patient to look at their overall alignment. There’s a growing trend in the United States right now whether or not you even should put them in that plumb or that level alignment. There’s some good data that about 12-15% of surgeons out there are leaving their patients that have probably been bowed their entire life a little bit bowed and doing what’s called kinematic alignment. So, that’s being played around with, but I think technically, I think you have to look at the alignment and look at the axis of the extremity, and you don’t want to overcorrect them. You certainly don’t want to take somebody who is in a more of a bowed posture and then make them knock-kneed. That’s about the worst thing you can do, and I think the other thing that you have to pay the most attention to when you’re doing this is to pay attention to the knee cap.
I think that the patella is the bellwether for a knee replacement. It’s essentially how you grade how well you did with the alignment, in particular the rotational alignment of the device because I think if you did well with both the femoral and the tibial rotation and got it where you want it, the kneecap should just glide right on the front of that implant with no problems. If it looks like it’s tiltering or it’s trying to jump out of the groove that it rides in, probably means something’s not quite right with the rotational alignment of that device. That’s one of the more common things I see.
The other probably big problem that I see that’s a technical error is probably what we would call mid-flexion instability. That just means that the size of the implant on the femoral side was maybe not quite right and when you come into about 30 to 60 degrees of flexion, the patient feels like their knee is a little unsteady, and that’s important because if you’re going up and down stairs, that’s about how much your knee is bent when you start doing that. That’s about the last place that you want a patient to feel unsteady is on a pair of stairs.
Host: That’s great advice. So, tell us a little bit about what you’re doing to optimize patient outcomes and what’s unique about what you do at Northwestern Medicine.
Dr. Beal: So, we do a few things. So, we do use some patient-specific guides. I think—with that’s been adopted, and I think some patients that are a little bit more tech-friendly like the idea of having that extra little bit of assurance from the surgeon that they’re putting the device where they want it, but I think some of it is device selection. I think that we use an implant that’s maybe a little bit different. It’s what’s called a medial pivot or a medially stabilized knee, and that device has a little bit more of a dish in the inner aspect of the tibia, and it’s pretty much flat laterally, which allows the knee to kind of pivot around a medial axis, which is what your knee and my knee does with an intact anterior cruciate ligament and intact posterior cruciate ligament. So, the idea is if I can get the knee to move a little bit more like it normally does with intact ligaments and then I take all that stuff out of the knee. So, I remove the ACL. I remove the PCL. I remove the menisci. I need the bearing, in this case, the plastic to kind of drive that normal rotation that the person’s used to. So, what we’re seeing is when we do that in concert with some of these guides and getting the alignment where we want it, patients like that knee a little bit better, and they like it a little bit better for very specific activities, which are what we would call flexion-based activities. So, if something you’d have to do where your knee is a little bit bent, but not fully bent, and the best example, like we already said, is stair climbing.
Host: Where do you see the field going? What’s exciting in research that might impact the future of total knee replacements? Anything else you’d like providers to know to take forward and help their patients?
Dr. Beal: Cartilage restoration surgery or preservation surgery that’s out there, both for the hip and the knee, and I think people are really trying to avoid knee replacement surgery with metal and plastic, and I think eventually what you’re going to see is—you’re going to see the research come around for what we would call scaffolding research, which just means, we can grow cartilage in the lab. So, the lab, you can take a cartilage biopsy from someone, take it into a petri dish into the lab and grow cartilage and get the cartilage to—you can have a ton of it. The problem is if you grow it in the lab, if you look at it under a microscope, it just looks like needles in a haystack. So, it’s just kind of going everywhere, and it doesn’t necessarily have the same properties of the cartilage that we want. So, if you could tell the tissue how to grow and scaffold it so that those cells were actually producing the cartilage in a specific fashion, it would give the cartilage more structural properties that would be essentially like normal cartilage. You could imagine the future where instead of putting and implanting metal and plastic into somebody’s knee, you would make the cuts that I normally make for a knee replacement, fix the alignment, and then open a freezer and pull out a fresh graft that was grown in the lab that’s sized for that patient and put what we would call an osteochondral graft into the knee and then essentially let it heal. So, you’d have not metal and plastic in your knee, but new cartilage, which is, I think, what everybody wants.
Host: Fascinating, what an exciting time to be in your field. Thank you so much, Dr. Beal, for joining us and sharing your expertise on total knee replacement today. That wraps up this episode of Better Edge, a Northwestern Medicine podcast for physicians. To refer your patient or for more information on the latest advances in medicine, please visit our website at nm.org to get connected with one of our providers. If you as a provider found this podcast informative, please share. Share with your patients. Share with other providers or on your social channels, and be sure not to miss all the other fascinating podcasts in the Northwestern Medicine library. I’m Melanie Cole, thanks so much for listening.
Optimizing Outcomes in Total Knee Arthroplasty
Melanie Cole (Host): Welcome. Today, we’re talking about total knee arthroplasty, and my guest is Dr. Matthew Beal. He’s an associate professor of orthopedic surgery at Northwestern Medicine. Dr. Beal, what a pleasure to have you with us today. Give us a little bit of a brief overview of total knee replacement and when it should be considered.
Matthew Beal, MD (Guest): When you talk about patients wanting to have their knee replaced—and that’s the first thing—I think a lot of times patients are considering, but they’re not yet ready, and I think a lot of the primary care doctors, I think, some of the things that they could do to help themselves would be, you know, the first thing that I always do is get weight-bearing X-rays. So, we get films with the patient actually standing up so that you can see what does their axis look like? What does the wear look like in their knee when they’re actually putting weight through their knee? I think one of the common things we see is that people get non-weight-bearing X-rays and the spaces between the femur and the tibia actually looks pretty good, but then you have them to stand up, and that space goes away pretty quickly just because they’re bearing weight, but I think when you see that on a plain X-ray before you order, you know, MRIs and CT scans, that’s probably the number one thing that when people show up, that’s what they—that they look like when they’re ready for a knee. I think the obvious reason why we do it—we do it for pain. If your knee hurts, and you failed a few non-operative measures, that’s usually when people start to think about surgery when they’re still, you know, reasonably uncomfortable despite some of these other things that folks will try.
Host: Well, thank you for that. So, what conditions can complicate the procedures that you’re considering, whether it’s obesity or if they have any comorbid conditions. Speak about some things that can complicate what you’re going to do.
Dr. Beal: So, I think all surgeons these days, including me, look for the general medical issues that can complicate surgery. This is elective surgery. That’s the most important thing to remember. We’re not talking about life-saving surgery. We’re talking about a quality of life surgery. So, you really want the patient in the best medical position when they go through this surgery. So, a lot of the things that we see—we do see obesity as being a big problem. There’s pretty good data from multiple different places that looks at BMI as a risk factor. Most centers across the country will set a BMI cutoff and our place looks at 40 to 42 as being the number that above which you usually have more problems after surgery. There are some centers that even go down as low as 35 for their high limit for their BMI. So, weight plays a part in it, but it’s also weight with other things. So, it’s diabetes. It’s blood pressure control. It’s smoking. All those things, when you start, you know, stacking them on top of each other, makes the risk for the patient a lot higher for not only surgical complications but medical complications after an elective surgery. So, it makes a surgeon think long and hard about performing that joint.
Host: Tell us some of the most innovative technologies that you use these days. What’s going on in the world of total knee replacement?
Dr. Beal: So, there’s a lot of things that are out there. There are robots. There are special guides. I think they’re all getting at the same thing, which is we know that we’d like to improve the alignment of the device to improve how long it will last for the patient as well as just the overall feel of the knee so that the patient actually reports that the outcome is good. So, there’s different ways you can do that. So, there are robots from multiple different companies that are available that use imaging beforehand, either a CT scan or an MRI of the patient’s knee to choose the axis of the extremity. So, if you can imagine you draw a line from the center of the hip to the ankle, and you’re trying to make that a neutral axis. So, in carpentry terms, that’s trying to make, you know, the line plumb. You use that imaging to essentially set that axis and then the robot will keep you in that frame when you’re operating. So, in other words, you can’t drift as the surgeon outside of what you have predetermined as the acceptable alignment for that device. So, that’s one way of doing it. That requires a little bit more intraoperative work because you have to have a robot. You have to show the robot where the patient is. You have to show the, you know, robot where the patient’s anatomy is. So, it takes a little bit longer. Some surgeons are switching to things like what I use, which is patient-specific guides. Those guides use the same sort of imaging technology, whether it’s a CT scan or an MRI to again look at the axis of the extremity, and then those guides are specific to the patients. In other words, they fit on the ends of the bone onto the femur and the tibia to predetermine the cuts of the knee replacement as well as the sizing. So, it makes it a little bit more accurate and a little more precise, and that seems to be pretty helpful for folks, when they’re, you know, especially in the United States, majority of knees are done by folks that do less than 50 a year, and it seems to improve the quality and the outcomes for the surgeons that don’t do as many of them.
Host: Sounds a bit like using a level so that it really holds it where you want it to go. Now, tell us a little bit about some technical considerations that you might like some of those providers that are not doing quite so many as you do—do you have any technical advice for them?
Dr. Beal: Well, I think you have to consider the axis of the patient to look at their overall alignment. There’s a growing trend in the United States right now whether or not you even should put them in that plumb or that level alignment. There’s some good data that about 12-15% of surgeons out there are leaving their patients that have probably been bowed their entire life a little bit bowed and doing what’s called kinematic alignment. So, that’s being played around with, but I think technically, I think you have to look at the alignment and look at the axis of the extremity, and you don’t want to overcorrect them. You certainly don’t want to take somebody who is in a more of a bowed posture and then make them knock-kneed. That’s about the worst thing you can do, and I think the other thing that you have to pay the most attention to when you’re doing this is to pay attention to the knee cap.
I think that the patella is the bellwether for a knee replacement. It’s essentially how you grade how well you did with the alignment, in particular the rotational alignment of the device because I think if you did well with both the femoral and the tibial rotation and got it where you want it, the kneecap should just glide right on the front of that implant with no problems. If it looks like it’s tiltering or it’s trying to jump out of the groove that it rides in, probably means something’s not quite right with the rotational alignment of that device. That’s one of the more common things I see.
The other probably big problem that I see that’s a technical error is probably what we would call mid-flexion instability. That just means that the size of the implant on the femoral side was maybe not quite right and when you come into about 30 to 60 degrees of flexion, the patient feels like their knee is a little unsteady, and that’s important because if you’re going up and down stairs, that’s about how much your knee is bent when you start doing that. That’s about the last place that you want a patient to feel unsteady is on a pair of stairs.
Host: That’s great advice. So, tell us a little bit about what you’re doing to optimize patient outcomes and what’s unique about what you do at Northwestern Medicine.
Dr. Beal: So, we do a few things. So, we do use some patient-specific guides. I think—with that’s been adopted, and I think some patients that are a little bit more tech-friendly like the idea of having that extra little bit of assurance from the surgeon that they’re putting the device where they want it, but I think some of it is device selection. I think that we use an implant that’s maybe a little bit different. It’s what’s called a medial pivot or a medially stabilized knee, and that device has a little bit more of a dish in the inner aspect of the tibia, and it’s pretty much flat laterally, which allows the knee to kind of pivot around a medial axis, which is what your knee and my knee does with an intact anterior cruciate ligament and intact posterior cruciate ligament. So, the idea is if I can get the knee to move a little bit more like it normally does with intact ligaments and then I take all that stuff out of the knee. So, I remove the ACL. I remove the PCL. I remove the menisci. I need the bearing, in this case, the plastic to kind of drive that normal rotation that the person’s used to. So, what we’re seeing is when we do that in concert with some of these guides and getting the alignment where we want it, patients like that knee a little bit better, and they like it a little bit better for very specific activities, which are what we would call flexion-based activities. So, if something you’d have to do where your knee is a little bit bent, but not fully bent, and the best example, like we already said, is stair climbing.
Host: Where do you see the field going? What’s exciting in research that might impact the future of total knee replacements? Anything else you’d like providers to know to take forward and help their patients?
Dr. Beal: Cartilage restoration surgery or preservation surgery that’s out there, both for the hip and the knee, and I think people are really trying to avoid knee replacement surgery with metal and plastic, and I think eventually what you’re going to see is—you’re going to see the research come around for what we would call scaffolding research, which just means, we can grow cartilage in the lab. So, the lab, you can take a cartilage biopsy from someone, take it into a petri dish into the lab and grow cartilage and get the cartilage to—you can have a ton of it. The problem is if you grow it in the lab, if you look at it under a microscope, it just looks like needles in a haystack. So, it’s just kind of going everywhere, and it doesn’t necessarily have the same properties of the cartilage that we want. So, if you could tell the tissue how to grow and scaffold it so that those cells were actually producing the cartilage in a specific fashion, it would give the cartilage more structural properties that would be essentially like normal cartilage. You could imagine the future where instead of putting and implanting metal and plastic into somebody’s knee, you would make the cuts that I normally make for a knee replacement, fix the alignment, and then open a freezer and pull out a fresh graft that was grown in the lab that’s sized for that patient and put what we would call an osteochondral graft into the knee and then essentially let it heal. So, you’d have not metal and plastic in your knee, but new cartilage, which is, I think, what everybody wants.
Host: Fascinating, what an exciting time to be in your field. Thank you so much, Dr. Beal, for joining us and sharing your expertise on total knee replacement today. That wraps up this episode of Better Edge, a Northwestern Medicine podcast for physicians. To refer your patient or for more information on the latest advances in medicine, please visit our website at nm.org to get connected with one of our providers. If you as a provider found this podcast informative, please share. Share with your patients. Share with other providers or on your social channels, and be sure not to miss all the other fascinating podcasts in the Northwestern Medicine library. I’m Melanie Cole, thanks so much for listening.