Emerging Trends in Artificial Knee Replacement - Craig McAllister, MD

Dr. Sechrest: Hello, I'm Dr. Randale Sechrest, your host for eOrthopod.TV. Today I have with me as a guest Dr. Craig McAllister. Dr. McAllister practices orthopaedic surgery in Kirkland, Washington. He is a surgeon who specializes in complex reconstructive surgery of the hip and knee. Dr. McAllister did his medical school training at the University of Washington. He then completed an orthopaedic residency at Albert Einstein College of Medicine in New York. From there, he finished an orthopaedic fellowship at the Cleveland Clinic Foundation in reconstructive surgery of the hip and knee. Thanks for joining us today, Dr. McAllister.

Dr. Craig McAllister: Thank you for inviting me.

Dr. Sechrest: Dr. McAllister, today what I'd like to discuss are some of the recent advances in knee replacement. Knee replacements have been done in this country probably for 40 years now, but the last decade has really seen a significant advancement in terms of the technology and how we're really rethinking when and how we do artificial knee replacements. So, I guess, for the start, sort of summarize for us what the technology was like, say, 15 years ago, with artificial knees.

Dr. Craig McAllister: Well, one of the points that I've made before, and I always like to make to preface this conversation, is that the most significant phase-shift between now and the time the joint replacements started was that, originally, joint replacements were reasonably crude operations that were focused on trying to help that low-demand, elderly patient with very severe debilitating arthritis. That has changed to where, now, it's a much more technologically advanced surgery with much more sophisticated techniques that really now has the opportunity to focus its attentions on the higher demand patient who wants better range-of-motion, better longevity, and may not be at such end-stage agony, but needs to be able to get back to work, and might even want to get back to some level of recreation. So, a lot of what we're going to talk about here today represents that change in the focus of joint replacement.

Dr. Sechrest: So what we're talking about is, obviously, when I started practice, there was an old adage that you don't do an artificial knee replacement on anyone younger than 65, and a lot of patients were told that.

Dr. Craig McAllister: Right.

Dr. Sechrest: We all had the misfortune, I guess, of seeing all of these patients who had either posttraumatic arthritis or early osteoarthritis, we had no solutions for them.

Dr. Craig McAllister: That's right.

Dr. Sechrest: Because we couldn't trust our artificial knees to really put up with hiking, biking, golfing, and those sorts of things.

Dr. Craig McAllister: Right, and we were left with either doing an operation that we knew wasn't really ideal for that patient -

Dr. Sechrest: Right.

Dr. Craig McAllister: Or telling them we couldn't help them.

Dr. Sechrest: Yeah.

Dr. Craig McAllister: I think as the baby boomers have gotten into the age of arthritis, it's really pushed this effort to be more sophisticated and meet those needs. Those joint replacements that you and I remember, from when we were first in our training, or maybe even in medical school and before, they were much bulkier, more ligaments were harvested to do the operation, they required stems that went up into the bone to get adequate stability. They didn't, you know, allow much in the way of range-of-motion, but they didn't need to because they were focused on that low-demand patient. In fact, really, even as late as the 1980s, some of them were really just being placed eyeball, with no real instrumentation to help make sure that the alignment of the leg and that the ligament balancing was all done appropriately. Much of that has changed now with the advent of computer navigation, and low profile instruments, and implants that don't really take ligaments or bone to the do the operation. Range-of-motion has improved. Bearing surfaces have improved. So, yeah, it's a much different operation from that origin.

Dr. Sechrest: I guess you brought some implants to show, or at least some models. I'd be very curious at seeing the difference, and it looks like, from looking at what you've got there, clearly things are changing.

Dr. Craig McAllister: Yeah.

Dr. Sechrest: So demonstrate for the audience what's going on there.

Dr. Craig McAllister: Well, first of all, as we'll talk about later, the advances go far beyond just the implants, and all of these models really do is start to touch on some of the changes that have occurred in the implants. I don't really have an implant that represents the older technology that harvested all of the ligaments. But I think some of what we have here demonstrates one of the changes, and that's going towards partial knee replacements or lower profile knee replacements. The most common sequence of events that I see in my office is a patient has really reached the end of the arthritis. Their medical management has failed, whether it's the hip or the knee. They've been told they need to have a joint replacement, and they're not coming for a consultation on joint replacement. So for the overwhelming majority of patients and doctors that means they're talking about this type of an implant, where, for the knee at least, the top of the tibia, both sides of the tibia, maybe just to help with reference, it's helpful to go through some of the anatomy here. This is a knee, here's the tibia, here's the femur, and, as you know, this is the kneecap. So we like to think of the knee as being basically three compartments. There is what we call the medial side, the inside of the knee, and then there's the outside of the knee; and then there's also the compartment between the kneecap and the rest of the knee. So a traditional knee replacement, basically, took out the damaged, worn, absent cartilage; excised part of this tibial bone and put this plastic on top of the tibia. And then, the same sort of thing is done on what we call the femoral side where the femur is resected partially, in older femoral components, more bone was taken; and then this implant is put on the end of the femur. So it ends up being; today's knee replacement, quite honestly, I tell patients, is more of a resurfacing operation than it is a replacement. In older style knee replacements, they did truly take the knee out and put in a cemented, stemmed, hinged implant. Those are still used rarely as revision instruments. But today's first knee replacement is going to be more of this resurfacing type of operation where all but one of the ligaments is retained, and the patella, the backside of the kneecap and the end of the femur, and the tibia are resurfaced; still easily the most common operation that's done in terms of replacement surgery.

Dr. Sechrest: And still a good operation.

Dr. Craig McAllister: Still, it is the gold standard. It's the one that certainly American surgeons have had the most experience with. They were trained to do it in their residency. The technology, the instruments, they're all accustomed to, and, certainly, the front line answer, even for patients with limited arthritis, is still going to be the gold standard knee replacement. But, realistically, there are alternatives to that full knee replacement. There are still some parts about it that patients aren't going to like. It's range-of-motion is not as good as a partial knee replacement. It doesn't feel as natural. The anterior cruciate ligament, one of the ligaments, is still excised to do this. So, there are other alternatives, for a reasonably, I won't say small, but, let's say, pretty well circumscribed percentage of those patients who need a knee operation, a resurfacing operation, about 12-15% of them might be appropriate for a partial knee replacement.

Dr. Sechrest: Well, and is this partial knee replacement, is this something that is always done in younger patients? Or it this appropriate for an elderly patient as well?

Dr. Craig McAllister: Well, that's a good question. When we're out there on the lecture circuit, we talk about a bimodal population that it is appropriate for. What we mean by that is you look at a graph of the age and you see two blips. There's the younger but still low demand patient, in their 50s, they're not athletes, and that sort of thing, but they have limited arthritis, they're appropriate for this, and their main incentive for doing it, besides that early range-of-motion and better feel is going to be, "Well, if I can do this partial as a first operation, my second operation might be this other primary total knee." So they're inserting it in their sequences of events as part of their overall plan. The elderly patients, it's going to be attractive to some elderly patients because, quite honestly, it's easier to tolerate the surgery. So we have fewer problems anemia and postoperative pain. They get their range-of-motion back. The physical therapy is easier. So when we're doing an elderly patient we would like that to be their only operation and their incentive to do it because it's just easier to get over the operation.

Dr. Sechrest: So what you're really talking about is that two things occur; two benefits, even in an elderly population or an elderly patient. One is you're taking off less bone, you're taking off less tissue. So you're destroying less normal tissue, or relatively normal tissue, tissue that doesn't have to be removed. And the other thing is that you're able to do this through a more minimally invasive approach, so that you're making smaller incisions, again damaging less normal tissue, putting in what's necessary but not going overboard and putting in more than is necessary. So, if I hear you correctly, even the elderly patient gets over the operation faster with less complication possibly, and can tolerate that procedure better.

Dr. Craig McAllister: Yeah. Those distinctions have gotten somewhat blurred as we have figured out how to take some of those minimally invasive elements of partial knee replacement and now we do them with total knee. So the discrepancy between the two has lessened. But still, the partial knee replacement is the original minimally invasive knee replacement.

Dr. Sechrest: One of the benefits, I guess, is because you're not taking off, in a younger patient especially, because you're not taking off as much bone, you have more to work with if that person, if this thing lasts 12 years let's say.

Dr. Craig McAllister: Yes.

Dr. Sechrest: And then they wear out the other side, the part you didn't fix. You've got more tissue to work with so you probably get a better result from that revision.

Dr. Craig McAllister: It's been well documented now in our literature. Originally, I'd say, in the early 90s, it was somewhat controversial, but it's now well accepted that the results of changing this partial knee replacement to a primary total knee are far superior to trying to take one of these out and to trying to take one of these out and converting it to a revision style knee replacement.

Dr. Sechrest: Well, let's go back and try to help me with the decision making process for patients. Let's just say we've got a patient, who is not low demand, not high demand; just a patient with an x-ray that looks they have X-amount of arthritis on their knee. How do you advise that patient? How do you decide whether that knee and that patient is amenable to a partial knee replacement versus a total knee replacement.

Dr. Craig McAllister: That's a very important conversation from two sides. One is if they're appropriate for the operation, then why not offer it to them? Well, one of the answers to that is because it's not just a little knee replacement. The technique for doing it is considerably different and somewhat more demanding than doing actually a total knee. So, you know, it's a relatively limited patient population so, #1, the surgeon needs to be comfortable with the operation. #2, on the opposite side of that is there is this tendency at times, once the surgeon is doing them, that the patients do so well that we find ourselves seduced into to doing it in a lot of our patients and our literature is very clear on this now, that, if the patient was not appropriate for it, if their arthritis was not truly limited to that one compartment, one area of the knee, is their knee isn't well aligned, we can't do as much when we do this operation as we can when we do a total knee, in terms of correcting malalignment and such. So, if the patient wasn't appropriate for it, what tends to happen are early failures. Historically, there was this feeling well it's okay if a partial knee fails early because it was just a little resurfacing operation, but what I counsel my patients is very clear. The only thing worse than a big operation; is then a little one first, and then the big one shortly after that.

Dr. Sechrest: Right.

Dr. Craig McAllister: And patients who endured that short-term failure of a partial knee replacement who had to have a total knee would tell you that they just wished they'd gone with the total knee in the first place. So it's a reasonably complicated conversation, you know, there's some pretty well accepted criteria that have to do with the patients symptoms, their type of arthritis, how isolated the disease is to that one compartment, and alignment issues and other things, and range-of-motion, that help us to determine that correct 12-15% of patients who should have that smaller knee.

Dr. Sechrest: So the real risk here is not doing enough surgery in the patient. I mean, that seems like the risk is that you choose to do what you think is less of an operation, to the benefit of the patient, but you just didn't do enough of an operation.

Dr. Craig McAllister: You need to fix what's there.

Dr. Sechrest: Right.

Dr. Craig McAllister: You need to be able to fix the problem and not, as I said, get seduced into doing the smaller surgery just because it seems like it will be easier.

Dr. Sechrest: Well, let's really define for patients what the difference is. I mean, you mention that even the traditional artificial knee is becoming more and more done by minimally invasive technique, so that operation itself is getting smaller, let's say. At the same time you've got these other options that involve minimally invasive surgery and a partial knee replacement. What's the difference? I mean, from the patient's standpoint, hospital time, preparation, recovery time, distinguish the two.

Dr. Craig McAllister: Well, that's a difficult topic, realistically. I would counsel patients to be sure to talk their surgeon and get their answers from their surgeon because they will be highly variable; just like partial knee replacement is not necessarily done by all surgeons. Certainly, minimally invasive surgical techniques and total knee replacement is not going to be the favored option for all surgeons. But, the results are increasingly, and we published our experience recently in a major journal that actually looked at the difference for patients after surgery. Comparing traditional knee replacement with a traditional surgical exposure to knee replacement with minimally invasive surgical techniques, and we saw a few measurable differences.

Dr. Sechrest: And these were full knee replacements.

Dr. Craig McAllister: Right. These were all full knee replacements. We subsequently also compared them to our unicondylar knee replacements and published that, and we can touch on that also. But what we know about knee replacements, full knee replacements done with minimally invasive surgical techniques, is that they can expect less postoperative pain. They still need narcotics, it's still a big operation, but it's less. They can certainly expect a small incision although we don't really emphasize trying to make a tiny buttonhole incision. They can expect a better overall range-of-motion earlier. By a year they will probably be very close regardless of the technique. But our patients who had minimally invasive surgical techniques regained their preoperative range-of-motion at 3 months, whereas with the traditional surgery took a year. In a larger percentage, 12% of our patients that were done with traditional measures required significant interventions after surgery to get their range-of-motion, namely what we call manipulations, where we have to bend their knee for them under anesthesia. That dropped to a mere 1-2% when we went to our minimally invasive surgical techniques. Since that publication, we've introduced computer navigation, which we'll talk about in more detail later, but that has also enabled us to get even smaller and more accurate with our minimally invasive surgical techniques and it's resulted in less blood loss, near 4% of our patients are transfused anymore compared to 32% with the traditional technique. So we've been able to measure less blood loss, better range-of-motion, less postoperative pain, and fewer patients who need significant interventions in terms of manipulations and physical therapy after surgery.

Dr. Sechrest: Now any difference in how long they stay in the hospital?

Dr. Craig McAllister: Well, that's a great question. We're doing about 10-15% of our knee replacements now as outpatients.

Dr. Sechrest: And this is the full knee replacement?

Dr. Craig McAllister: Yes. Those are our healthy motivated patients with very good resources at home who understand that there are some benefits to not being in the hospital for extended periods of time, and we've realized that we don't need necessarily to have all of our patients in the hospital. But our length of stay is considerably down. You know, when you and I first doing joint replacements, it wasn't unusual for them to be in the hospital for 14 days.

Dr. Sechrest: Yeah.

Dr. Craig McAllister: We saw that drop to 8 days about 12 years ago, then to 4 or 5 days about 6 or 7 years ago, and now it's pretty routine that even traditional protocols are 3 or 4 days in the hospital. It's unusual for our patients to spend more than 1 maybe 2 nights in the hospital anymore, and usually if they're spending that long, 2 nights in the hospital, it's because their resources at home may not be that good or we have some concerns about other issues. But the length of stay in the hospital is highly patient-dependent; it's no longer dictated by the fact that they're having a knee replacement.

Dr. Sechrest: Now what about the partial replacements. Is there a difference between how long those patients stay in the hospital? Are you doing more and more of the partial replacements as outpatients?

Dr. Craig McAllister: Yeah.

Dr. Sechrest: What percentage?

Dr. Craig McAllister: Almost exclusively now. Again, it goes more to the patient than it does the operation. If I'm doing an arthroscopy in a patient who's 82 with medical issues, I'm going to be pretty hesitant about sending them home.

Dr. Sechrest: Right.

Dr. Craig McAllister: But let's talk about that higher demand, more active, 50-some year-old patient who doesn't have any alarming medical issues and is otherwise in reasonably good shape, I wouldn't see any reason for them to be in the hospital, not in my practice. But certainly not a reason, some surgeons still like to have them in the hospital.

Dr. Sechrest: But this is definitely moving towards, knee replacement may at some point be, almost totally an outpatient procedure.

Dr. Craig McAllister: I see that as a reality for that healthy patient sector within the next 8 years.

Dr. Sechrest: Well, let's talk a little bit about the partial knee replacement. Tell me how that differs from the traditional knee replacement. What are the differences that you as a surgeon have to take into consideration when you're putting one in? You mentioned it's harder, you mentioned that it takes more skill. Why?

Dr. Craig McAllister: To paraphrase a comment that I made in a chapter that I wrote is that the surgeon who expects to be able to use his techniques that he learned to do total knee replacements to do a partial knee replacement will be as disappointed as his patient. Okay, because they are considerably different. The exposure techniques are different. We can't open up the knee as much. We retain the anterior cruciate ligament, which changes the nature of the operation. Some of what makes doing the partial knee replacement potentially more difficult is it is more limited in terms of the number of patients that we can do and some of that's for technical reasons. So, if the surgeon tries to do a knee with a significant stiffness or bad malalignment, he's going to struggle in getting that implant in. We have more freedom in terms of what we call tissue balancing with the knee replacement because we can put in different size implants and such and we can release more ligaments, but whereas with the partial knee replacement, we're very limited in what we can do with ligament releasing and so on. Smaller space to put our instruments in, different techniques to bring the tissues to us to the surgical dissection as opposed to being able to open up the knee more widely.

Dr. Sechrest: Yeah, it's always struck me that it's easy to do, well, relatively easy, to do a regular knee replacement because you don't have to match anything. You're in total control like you said. With the partial knee replacement, all of the sudden you have to match otherwise you get a like a table that rocks or a chair that rocks, you basically create a situation that, if you don't match what's there, and you get one chance to do it, if you don't match what's there, you've got a knee that rocks and it's not going to work very well.

Dr. Craig McAllister: Well, and a good example that illustrates that is the partial knee replacements, when we look at our literature, they're very intolerant to any malalignment. If the knee is left a little, a couple degrees one way or the other, they either wear out their plastic earlier or they wear out that other compartment earlier. Whereas total knees, historically, at least in that 10 or 15 year zone have been relatively bulletproof in terms of a few degrees off, as it were, because everything has been resurfaced. So, yeah, I honestly believe that our parameters are more exacting, our ability to expose the knee is more limited, and, since only 12 or 15% of patients are appropriate for it, the reality is, as you and I both know, is that a reasonable number of these surgeries are done by surgeons who are doing 10, 15, 20, 30 a year. Well, if only 12% are appropriate for a uni- that means that you may have the opportunity to only do 1 or 2 of these a year. So there's a volume issue in terms of the experience.

Dr. Sechrest: So they're just out of practice. They should not, probably surgeons that aren't focused on that, or focused on reconstructive surgery, probably aren't getting enough practice to actually -

Dr. Craig McAllister: Or opportunities. And as I pointed out, this is still the gold standard. So, if a surgeon is comfortable with this and it's a good operation for the patient, as you know, we train a lot of surgeons at our center in joint replacement and we train them on minimally invasive techniques including unicondylar knee replacements. I bet a reasonable number of those surgeons come, look at the technique and say, "You know, I've just decided that's not for me. I'm going to go home and I'm still going to do my total knees in my patients and if they want something else, I'll send them to somebody else." And to me, that's the gold standard of surgical decision making, just like this a gold standard of knee replacement. I'd rather see those surgeons do a traditional knee that they're comfortable with, then try to force a partial knee replacement.

Dr. Sechrest: Well, I think I understand the difference a little better now. One thing that I still don't understand, is the role of computer guided navigation, and how this has, I think I understand, how it's driven the acceptance of these more minimally invasive, more accurate knee replacements, whether it's the total or the partial. But describe that for us, what is this new concept of computer guided navigation? How does it work and how is it making this possible?

Dr. Craig McAllister: Those are some great points there and I want to touch on a few of them. But let's just first try to put computer navigation in simple terms. People have compared it to the navigation systems in your car when you're in a town that you don't that well, how comforting it is to know you're going; to airplane landing and having a computer that helps the pilot know where he is. Well, let's compare and contrast that to knee surgery. Historically, when you and I trained, it was taking a rod and putting that up a bone or taking an apparatus and laying it on the leg and trying to eyeball our implants and then we would look at the leg and try to decide if it was well aligned. Basically, when we use those techniques, the gold standard has been that if we could get 70% of our knees within 5-7 degrees of ideal alignment we thought we were doing a pretty good job. That was just the standard. Well, computer navigation, in one way or another, and there are multiple different technologies for this, but in one way or another what we're doing is, we're putting sensors on the thigh bone and the shin bone, the tibia and the femur, and we're letting those sensors communicate with a PC, a personal computer, in the room. Then we're taking a pointer and we're touching different parts of the leg and recreating a live, real-time feedback, digital image of every step that we do in the operating room. So, we get confirmation that everything that we do is precise. That does two things: 1) it makes our implant position and alignment more accurate; 2) because we're using a small probe hooked up to a sensor we simply don't need as much exposure as we used to need with those bigger instruments. We don't have to put rods up the femur and so we've improved in terms of blood loss and postoperative pain issues. What that has done practically has created a new gold standard. Instead of saying that we get 70% of our knees within 5-7 degrees, now the gold standard is 95%-98% within 3 degrees. Is that going to be something that a patient notices? No, not for the most part. But recent literature has shown that knees that are within 3 degrees of appropriate alignment have 11-fold lower chance of needing a revision by 15 years.

Dr. Sechrest: So the bottom line is they last longer.

Dr. Craig McAllister: It's one of the things that will promote a longer lasting knee. There are other things as well, but we now have the opportunity to consistently dial in our knees with better implant positioning, better overall alignment, and requiring less exposure.

Dr. Sechrest: So rather than using what we used to use, basically looking at the knee and different type of jigs, the same way you would build a piece of furniture or something like that, you'd sort of attach something to the knee that you use to hold the saw while you cut it. Now we're using the computer to get better, more accurate alignment, cuts and that sort of thing.

Dr. Craig McAllister: Yeah.

Dr. Sechrest: You're expecting that to 1) make the surgery more accurate, but also 2) you don't have to see any more so you don't have to open that knee to see.

Dr. Craig McAllister: You don't require that much exposure.

Dr. Sechrest: You're using the computer to see for you.

Dr. Craig McAllister: Uh-huh.

Dr. Sechrest: And using your analogy it's sort of like if you're only 70% accurate that means that your airplane only landing in the clouds with about 70% of the wheels on the runway 70% of the time. Now we're landing on the runway all wheels all of the time, or at least 98% of the time.

Dr. Craig McAllister: Right.

Dr. Sechrest: And the big advantage is lower blood loss, less tissue damage, more accurate knee that lasts longer.

Dr. Craig McAllister: Yes.

Dr. Sechrest: And I think you also mentioned a couple other things. One is that you feel like that accuracy gives us a knee that functions better, not just longer, but functions better. Better range-of-motion, more stable and that accuracy is so important for the partial knee especially.

Dr. Craig McAllister: Well, it certainly having impact on our partial knee replacements as well. But as you're kind of touching on, realistically I simplified what computer navigation does. It also let's us look at our ligament balancing, and component rotation that has, and those things have an impact on immediate postoperative range-of-motion, how solid that knee feels in spite of the fact that it has a good range-of-motion. So there has been a litany of other, significant and important advantages to computer navigation.

Dr. Sechrest: Well, how widespread is this computer navigation? Is this that surgeons are just sort of adopting willy-nilly, or is it everybody wants one? Or where are we today?

Dr. Craig McAllister: Well, that's a really good question. The realistic truth there is that computer navigation really came on to the scene around 2004. Computer navigation represents a significant change in surgical technique. Imagine a pilot who has been used to flying visual and using his senses and his feel of the airplane who now all of the sudden is told, "No, we want you to use the computer and, in fact, now that you're using the computer you don't need a window", and we want you to do it through less exposure. Or another analogy I've made - imagine somebody wanted you to do your golf swing just using the computer instead of the feel. It can be a significant learning curve for the surgeon and the staff. Because it involves a computer it's much more oriented towards an entire room that knows what's going on. The assistant has to have a more active involvement so that the day when an orthopaedic surgeon who wants to computer minimally invasive knee replacement could just call up Dr. Joe, and say, "Can you help with a knee tomorrow?" is gone. So it really does sort of challenge the learning curve of the surgeon, the hospital staff, and everyone else involved. The other barrier is quite honestly, it's very pricey. A standard computer unit runs somewhere between $150,000 and $300,000. Particularly in this era when payers and the government want to pay less and less for these surgeries, it's a significant barrier for the hospital to acquire these units. So realistically, I've really spent the last 4 or 5 years lecture on this and going to meetings and just to illustrate the change, 5 years ago when I asked the audience how many surgeons here, audience of 500 surgeons, how many of you are navigating, you'd see one or two willing to raise his hand. 4 years ago, it was 10; 3 years ago it was a third of the audience that had at least tried computer navigation; 2 years ago people were afraid to admit they weren't doing it. But that's total joint surgery, that's 500 joint replacement surgeons. So it would be even a smaller percentage today who are actively navigating most of their total knees.

Dr. Sechrest: It sounds like this is destined to sort of be the standard of care at some point.

Dr. Craig McAllister: That's my opinion. Yeah.

Dr. Sechrest: Yeah. Any other benefits to the computer navigation that we haven't discussed, anything in terms of operative time or any of the other things that we typically look for to try to decide whether this is a net gain or a net loss?

Dr. Craig McAllister: Well, certainly early in experience if anything from an operative time point of view, most surgeons would tell you it's a disadvantage, because they've got their learning curve going on.

Dr. Sechrest: So it takes longer for them to do a patient until they get used to it.

Dr. Craig McAllister: For me now it's about a 5-minute add-on. So one of the reasons why it takes a little bit more time is because you actually catch mistakes and fix them. Some of those are good minutes that you're adding. The other big advantage with computer navigation though with computer navigation is the teaching tool for medical students. We're setting up a computer navigation learning lab at the University of Washington in conjunction with our artificial teaching knee, and our emphasis is going to be: what are the best teaching modalities so that a resident or a surgeon who is learning techniques can reproducibly get the results that we think they're getting and the computer navigation is going to be our evaluation tool. So we believe that, from a teaching point of view, it's going to help us again set a new gold standard.

Dr. Sechrest: Well, it sounds like that clearly the minimally invasive approach and especially using the computer guided navigation has made a huge difference in how we, as surgeons, look at total knee replacement now. I guess the question always come up something surgeons don't like to talk about a lot, but that is complications. Are there any downsides to the artificial knee? I think you mentioned one, if you don't do the right operation, it may fail, but any specific complications that patients should know about with partial knee replacements versus the traditional one.

Dr. Craig McAllister: And that list of complications is changing as time goes on, some new ones and some old ones that are going away. We mentioned one that's a real common one that is a stiff knee after surgery. I'd say, particularly with the knee replacements, where patients really need a certain range-of-motion in order to be comfortable and happy. If they don't get it, that's a complication and if they require other surgical interventions such as a manipulation we consider that a complication of surgery. So with the traditional technique we were seeing that in 10-12% of our patients, but with minimally invasive surgical techniques, we've seen that particular complication come down and range-of-motion improve. There are other less common complications that I think any surgeon is going to offer a knee replacement or a hip replacement will cover with patients, and that list can get long and dreary to go through but as a group or as groups, there are medical complications. Certainly this can be an elderly patient population who are predisposed to heart disease, vascular disease, and strokes. They might have kidney problems and lung problems and have issues with pneumonias and other, what we consider, medical complications. Another group of common complications would be related to the fact that they're having anesthesia. Postoperative pain, confusion, maybe reactions to the actual anesthetic itself, and it's very common really, I'd 8-12% of our patients have some type of minor medical complication like a reaction to a medicine or rash, or they get nausea or vomiting after the surgery and those are all important things to discuss with the patient even though patients may not see those as complications, we do. When we published our series of 200 knee replacements, 100 done with the traditional method, 100 done with the minimally invasive surgical technique, and in terms of complications, the difference was the manipulation rate. Only one of our patients with the minimally invasive surgical technique needed a manipulation whereas 13 of the traditional needed it. But otherwise the complication rate was 2% in the whole group. Of the 200 patients we only saw 4 patients with complications and they were: a heart attack in one patient, two patients had clots that didn't result in any significant problems, but we considered those complications, and one patient had a pneumonia after surgery. So that's a reasonably small complication rate but it's still very realistic if it's you that has the complication and patients need to know that.

Dr. Sechrest: Well, a couple, you mentioned the blood clots, and I think what you're talking about is deep venous thrombosis or thrombophlebitis sometimes; which it almost used to be a universal complication in total knee replacement. What about infection? Do you think we're going to see even a lower infection rate? Obviously the infection rate is very low in artificial joints, but my assumption would be that, as we do minimally invasive procedures with less tissue damage, less bleeding, that our infection should in fact go down.

Dr. Craig McAllister: Well, that's a very reasonable hope. Infection rates are a moving target. They are different in any point in time. We know from data that infection rates can be higher in one institution than another depending how they handle traffic and how old their rooms are and so on and so forth. Different parts of the country have different infection rates. There is a certain mass effect of hospital doing at least 100 a year, if it's below that then the infection rate is a little bit higher. Nationwide, the infection rate runs between 1 and 2 % of primary, first time hip and knee replacements, but it can get up to 3 or 4% at various institutions. But I think it's also a moving target in time. One example would be this resurgence now of resistant organisms. Particularly people hear a lot about MRSA, a methicillin resistant staphaureus and other resistant organisms with the wide spread use of antibiotics. So, as we reflect back on our discussion of outpatient knee replacements, the sooner we can get patients out of the hospital and out of that environment where patients who have those infections just exist, then I think that has a real positive impact on the potential for infections. It would be a good example where minimally invasive surgical techniques offer an opportunity to avoid a complication.

Dr. Sechrest: So hospitals have always been thought of as the place you go to catch, in the old days, you go to catch diseases, and we're beginning to see that at this point. Your point is that if we can do these operations as an outpatient, we may actually reduce our infection rate, not because of minimally invasive techniques, but because people aren't going into the hospital.

Dr. Craig McAllister: I would never want to scare patients of being in the hospital nor would I want to encourage outpatient knee replacement in a setting where it's not appropriate. But what I do tell patients is, I like to get them to think of a graph where the one line demonstrates or illustrates the risk of leaving the hospital too soon. That line goes down very quickly. With minimally invasive surgical techniques, certainly by 8 hours, or 12 hours, or 24 hours, the risk of sending a patient home too soon is dropping precipitously. But as the hospitalization progresses, especially if it progresses beyond what the patient really needs for his hospitalization, pretty soon the risk of being in the hospital starts increasing. An example would be an IV, an intravenous line that stays in longer than it needs to be, increasing exposure to other patients that have infections, communication errors between one nurse and the next and medication errors that are characteristically more probable the longer the patient is in the hospital. So what we counsel our patients is that there is a time when the risk of going home is going down and the risk of being in the hospital is going up and that's when we want them to go home, right at that moment.

Dr. Sechrest: Okay. Good advice.

Dr. Craig McAllister: And minimally invasive surgical techniques are helping us in that regard.

Dr. Sechrest: Well, as you look back on our discussion this morning, tell me a little bit about whether there is anything that we have not covered that you think patients need to know about new technologies with artificial knees and, especially, should they be seeking out surgeons that are using computer navigation, should they be seeking out surgeons that are doing these minimally invasive techniques, and the partial knee replacements. What's your advice?

Dr. Craig McAllister: Well, that's a double-edged sword, I believe. I think that these technologies, particularly minimally invasive surgical technique and computer navigation offer some potential benefits. Is it worth leaving your hometown to go to another surgeon just for technologies? Maybe not. If it's a solid, experienced, orthopaedic surgeon who's counseling to do this traditional knee with traditional measures, one of the things I pointed in our study, was that at one year some of the benefits, a good number of the benefits that we saw were gone and they were equal with the traditional measures. And, you know, a trusted orthopaedic surgeon in your community who's going to be there for you at postoperative week 6, and 12, and so on and so forth, is not an asset I would walk away from lightly. On the opposite side of that coin, I just pointed out that these are significant learning curves. I don't think that most patients really want to be part of that surgeon's learning curve. And if you're pushing the surgeon to do techniques that he's not necessarily comfortable with, you might find yourself part of his learning curve, and don't think that's really what most patients want nor should they seek it. On the other hand, if you're a high demand who needs range-of-motion and needs to get back to work and you have the means to seek out that physician. Certainly, that's what's happening today. Patients are going to the Internet, they're doing their research. The only thing that I would counsel patients is use the Internet to help you phrase your questions, but go to a trusted counselor and physician for the answers.

Dr. Sechrest: Well, thanks. I think that's good advice for anybody. I appreciate the good information. I think patients should get a lot out of this, and thanks for sharing.

Dr. Craig McAllister: Thank you for having me.

Dr. Sechrest: Thanks for watching today. If you have questions about the topic that we discussed today, or any orthopaedic topic, be sure to visit eOrthopod.com. If you're an orthopaedic surgeon or healthcare provider interested in participating as a guest on eOrthopod TV, you'll also find instructions on how to apply to become a guest on eOrthopod TV. Thanks for watching.