Hofmann v. Callaghan: Gentleman’s Varus Alignment Optimizes TKA Function
OTW Staff • Thu, April 13th, 2017
This week’s Orthopaedic Crossfire® debate was part of the 17th Annual Current Concepts in Joint Replacement® (CCJR), Spring meeting, which took place in Las Vegas this past May. This week’s topic is “Gentleman’s Varus Alignment Optimizes TKA Function.” For the proposition Aaron A. Hofmann, M.D., Hofmann Arthritis Institute, Salt Lake City, Utah. Opposing is John J. Callaghan, M.D., University of Iowa, Iowa City, Iowa. Moderating is Joshua J. Jacobs, M.D., Rush University Medical Center, Chicago, Illinois.
Dr. Hofmann: I wouldn’t call it varus alignment. I would call it normal alignment. That’s what these patients have that I’m tweaking a little bit into more anatomic position.
As for the varus knee, we’re really talking about mostly male patients and there is an interesting study, a Ranawat award paper that says constitutional varus happens at 3 degrees or more in 32% of men or 17% of women. That means that there are patients out there that have a significant amount of varus in their proximal tibia.
There are two philosophies of anatomic resection versus classic resection. Everybody knows you want to achieve rectangular resection in flexion and extension, and there are two ways to accomplish that. You can follow the anatomy on the femur a little bit closer and then make a cut parallel to the surface of the tibia, both in flexion and extension. It’s different from the classic which always takes a little bit more bone laterally than medially and you have to externally rotate the femur. So if you follow the patient’s anatomy life becomes a lot simpler. You cannot have this conversation unless you get longstanding films. What I’m trying to do is match the patient’s other normal side. Not trying to put the knee in varus, but placing the implant parallel to the ground and that’s what we’re trying to accomplish.
There are the two choices. If you want to tweak a little bit, that is instead of taking a 90 degree cut where you take a lot of bone laterally and a little tiny wafer medially, you can go parallel to the proximal tibia and solve the problem much better and have much easier soft tissue balance.
The femoral preparation is exactly the same. I like to follow the patient’s slope or go a little less. I use flat tibial trials as a block articulating spacer and I almost never have to do any balancing.
So when final implants are in place and the typical X-ray looks a little bit varus. The X-ray doesn’t look perfect, to your eyes perhaps, but it’s anatomic and it’s parallel to the joint. For the male patient or those 13% of women who have varus alignment of the proximal tibia, the mechanical axis, for me, then goes slightly to the medial compartment, which is anatomic, which is normal. The valgus leg I always cut perpendicular, or if they have an uncorrected valgus deformity, I might even leave them a little bit in valgus. This is the technique that we’ve followed for the last 25 years and the survivorship of the femoral and tibial components is extremely high—98%—in this particular study. So Mark Pagnano basically had it right, I think. You can look at your post-operative alignment and you have 0 degrees, plus or minus 3 degrees, it doesn’t necessarily mean you’re going to have better survival at 15 years.
So I say, make your life easier and consider a little gentlemen’s varus for the varus knee.
Dr. Callaghan: Aaron and I are truly partners in crime a lot of times, but on this one I’m going to take the opposite view. Aaron’s a cowboy and does a really good job of doing things that are offbeat, but I am more of a traditionalist.
I actually grew up doing a varus cut on the tibia. I was in the Army at the time at Walter Reed Army Medical Center. Many of you may remember the PCA [porous-coated anatomic] total knee. It was thought that was really the way that the prosthesis should be put in. Even though I’d trained up in New York because I was in PCA country near Baltimore, I was working on this and seeing how it did. But the problem that we were having when we tried to get the 3 degrees of varus, some of them ended up in about 5 degrees of varus, and I’m pretty sure that Aaron wouldn’t want that.
Instead we do what we call a traditional alignment, where we cut the tibia perpendicular to its shaft. If you look—including Chit Ranawat’s results from a total condylar design—the results are about 92% effective. But the most important thing that this study, and many others have shown is that tibial varus alignment is associated with the loosening of the tibial component in the long-term.
If you’ll look at varus articles in the literature, including our own, you’re talking somewhere around 98% success at 20 years, if not closer to 100%. We get a mechanical axis of neutral, a tibio-femoral alignment at 5-9 degrees of valgus, a joint line parallel to the floor, and a perpendicular cut to the tibia. You have to have proper alignment of all 3 planes. Soft tissue balance at extension first. Flexion gap next. Maintain the joint line. Correct sizing of the femoral component to restore offset, rotational alignment and lateralization, and proper cementing technique. That’s what Chit taught me years ago.
We think it’s really important to get good exposure. Sometimes you have to move your perpendicular alignment guide over the center of the talus, not the center of the two malleoli or you’ll still end up in some varus. We reference the tibial tubercle for rotation. We place the tibial component so that we cover the lateral plateau.
On the femoral side, we’ll actually use 7 degrees usually on the varus knee; less on a valgus knee—just the opposite of what Aaron’s talking to you about. And we also want to make sure in the sagittal plane that we don’t provide any flexion of the component. You have to do that by elevating your intramedullary guide for the femur, otherwise you’ll tend to put that component into flexion.
We don’t do huge medial releases any more to get our extension gap right and then we balance the flexion gap to that extension gap. The flexion gap is most important. You need to use Whiteside’s line or the transepicondylar axis. And we put the femoral component in somewhere as Aaron says in 3-4 degrees of external rotation and parallel to the tibial cut when you have the laminar spreaders in place. When you do that, you want to have taken more resection off the lateral side of the anterior femur to get that aligned.
I can tell you in our studies, we have outliers, but no revisions at those long-term periods of follow-up. So Aaron, I’m also from Texas and at times a cowboy, but in regards to changing from traditional alignment to kinematic alignment and varus cut, why would you want to challenge the great success we’ve had all these years?
Moderator Jacobs: We’ll start with Aaron. I think the most common criticism I hear of this approach—shooting for 3 degrees of varus or anatomic varus—is that while you can shoot for 3, when you shoot for 3, it’s a lot easier to get to 5 or 7 than if you shoot for neutral. We’ve heard data from the last series of talks, that there is a 3.8% risk of failure for each degree of varus malalignment. How do you do that? How do you make sure you have such a tight window so that you don’t go into excessive varus?
Dr. Hofmann: I think the argument that 3 degrees is going to become 5 or 6 degrees is lame because our instruments are accurate enough to keep that window narrow. I spent 10 years doing computer navigation and when I was doing navigation, I really found out that it’s better to be a little closer to the patient’s anatomy so that you don’t have to do any soft tissue balancing. I’m going to cut in 2 degrees and that’s going to get me a little closer.
Moderator Jacobs: So John, any response. Is this a lame argument?
Dr. Callaghan: I don’t think it’s a lame argument at all. If you look at the data, and I showed you some of our outliers, we actually get them in a little bit of varus. We don’t do it intentionally, but we get them in that. And the practical reality is that if you’re going to go for those couple of degrees of varus, there’s a chance that you’re going to end up with more and you know that if you do that, if you look long-term, those tibias are not going to do that well.
Moderator Jacobs: Let me just add something. Everybody talks about the PCA days and there’s not very many people in the room old enough to remember—well, you are John, and I am.
Dr. Hofmann: And I am. The problem was those instruments—not many people know this—those instruments were casted. They were mass producing these instruments and they were the least accurate instruments ever to be used. The tibial block is wobbly. You put the medial pin in the medial tibial cutting block and the block kicks into varus. We have navigation, we have lots of ways to narrow the window as Josh was asking about.
Moderator Jacobs: I’d like to follow up on that with a question for John. It’s not only the issue with the instruments in the PCA days, but in those days I would say the results of the PCAs circa 1980s was suboptimal? The question is to what extent did that have to do with the polyethylene at the time? Did it have to do with the fixation interfaces? My question for you is, with modern fixation interfaces, modern cements, and modern polyethylenes that wear less, is varus malalignment as much of a problem long term?
Dr. Callaghan: I guess I’m even more concerned today, Josh, because the patients I operated on when I started in practice in 1984, probably on average weighed about 170 pounds. Today the average person I operate on is somewhere around 34-35 BMI. I would actually flip that discussion, that even if Aaron’s results from 20 years ago, using that 2 degrees of varus looked great, I would still be concerned that today he’s not dealing with the same type of patients. I think you always have to have slop in the system and room for some error. And I say today, with the type of people we’re operating on, you might need more ability to have some slop in the system and not give somebody an alignment that potentially, at least mechanically on the bone, may be deleterious.
Moderator Jacobs: Any response Aaron?
Dr. Hofmann: Yes, I have one last comment. And that is, ask yourself why the medial side of the tibia is bigger than the lateral side? Is that because that patient is walking around with center of hips, center of knees, center of ankles, the medial side is bigger because it carries more weight. And so your argument about a heavy patient having a little bit of varus…probably is a good thing.
Moderator Jacobs: I want to give each of you a chance for a closing statement, start with John.
Dr. Callaghan: First of all I would agree with Aaron that I bet patients like that alignment better short-term. They would rather not have their knee kicked out. They would rather have it where it was their whole life. But I’m concerned long-term that that is not the solution.
Dr. Hofmann: I just want to say I’m talking about the male patient that has varus alignment. I’m not talking about the the right thing to do for a valgus leg or someone that has that kind of anatomy. I’m talking about the anatomic outlier, if you would. Your life will be easier if you kind of tweak a little bit of varus.
Moderator Jacobs: Thanks very much.
Senior Editor: Jay D. Mabrey, M.D., whose 35 year career in orthopedics included residency at Duke University Medical Center, service in the United States Army Medical Corps, Fellowship at the Hospital for Special Surgery and a long, distinguished career at Baylor University Medical Center where, in addition to his overall leadership at that institution, developed the Joint Wellness Program that helped patients get up after surgery more quickly, developed the first virtual reality surgical simulator for knee arthroscopy and chaired the FDA Orthopaedic Device Panel, is Orthopedics This Week’s newest contributing writer and editor.
Please visit www.CCJR.com to register for the 2017 CCJR Spring Meeting, – May 21 - 24 in Las Vegas.