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What Would You Do? Challenges in Knee Surgery
What Would You Do? Challenges in Knee Surgery Kelly G. Vince, MD, FRCS(C), Keith R. Berend, MD, Richard E. Jones, MD, Mark W. Pagnano, MD, Aaron G. Rosenberg, MD, and Leo A. Whiteside, MD Painful knees are selected to stimulate discussion on the topic of “alignment.” The depiction of “mechanical” and “anatomic” axes as well as the indications and preferred alignment for osteotomy, unicompartmental arthroplasty, and total knee arthroplasty illustrate areas of consensus and disagreement. Semin Arthro 21:116-127 © 2010 Published by Elsevier Inc.
Preamble Dr. Vince: Our problem cases all revolve around the issue of alignment, where one might think there is general consensus. I’ve been impressed by the recent article by Pagnano and colleagues,1 “The Mechanical Axis May be the Wrong Target in Computer-Assisted TKA,” in which they evaluated 399 total knee arthroplasties (TKAs) performed by Jim Rand more than a decade ago. We now have computer navigation and greater accuracy, but it’s not clear we agree on the for which targets to aim.2 Just so we can agree on terminology, anatomic alignment is the angle formed by the 2 medullary canals, and mechanical alignment is represented by lines from the centers of the hip, knee and ankle. Mechanical axis can be expressed either as an angle, as you see here, or as a straight line that shows where the axis crosses the knee joint (Fig. 1).3,4 I put in front of our panelists John Insall’s query, when we do knee-replacement surgery, are we reproducing “normal anatomy,” or are we sometimes, reproducing “pathology?” With that pretext, I’d like to assume that most of us are aiming for the kind of result on your left after surgery, not the one on the right (Fig. 2). This is Marks’ work (Fig. 3) I referred to. Jim Rand’s excellent surgeries showed that with a mechanical alignment within ⫾3 degrees of a neutral axis, there was an 84.6% survivorship at 14 years. By comparison, TKAs with worse alignment (more than 3 degrees beyond a neutral axis) had superior survivorship of 87%. This finding turns the world on its head. Leo, can I start with your opinion on this information? Dr. Whiteside: That has not been my experience. I believe alignment matters. And throughout my career, I found that when I’m referred patients who are still crooked, they’re usually symptomatically crooked. Dr. Vince: Fair enough. Mark, I’d like to give you the last word, but meanwhile, Aaron, what do you make of this? Dr. Rosenberg: I think it makes some sense only in reference to what Insall said in your quotation. That is, someone who’s been in varus since birth and has a relative progression 116
1045-4527/10/$-see front matter © 2010 Published by Elsevier Inc. doi:10.1053/j.sart.2010.01.006
of that varus; if you correct them to a fully neutral mechanical axis, I don’t think they do better than if you correct them back to what they were like when they were 19 or 20. So my tendency has been, in general, not to overcorrect total knees. Dr. Vince: Dickey, what about valgus knees? Dr. Jones: I think it’s important to look at valgus knees differently when you’re doing your alignment, and I will look to 4 or 3 degrees of valgus alignment in patients who have significant valgus of more than 10 degrees preoperatively. Dr. Vince: But 3 to 4 degrees of anatomic valgus represents a considerable correction and perhaps even varus mechanical alignment. Keith? Dr. Berend: I think we saw a great debate earlier this afternoon on these data. If you really, truthfully look at the information in front of us, the explanation is multifactorial, which I think was the conclusion of the study. We don’t know what the target is, but we’re pretty sure that it’s somewhere around 3 degrees. And with the numbers that are in this study in such a relatively small difference in survivorship, it’s hard to tell what the true difference was. In almost every other study with enough knees for statistical power, the dominant factor has been alignment. Dr. Vince: Mark, you’ve been close to these data. What sense do you make of it at this stage? Dr. Pagnano: I believe factors other than alignment are more important than alignment in determining survivorship at 15 years. The reason why Leo sees malaligned knees failing in his practice are that those are the knees that happen to come to see you. The ones that are still aligned, it’s a wear through the polyethylene or something, then the surgeon who did the original surgery might be revising that one. So there’s some selection when you have a referral practice. What this tells me is that spending inordinate amounts of time chasing a 0-degree mechanical alignment is not going to pay off for me at 15 years. And I think we need to spend our efforts looking at other factors and the interplay of the factors if we’re really going to make a difference.
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Figure 2 Universal stick figures begging the question: do you really want undercorrection?
Case 1
Figure 1 (A) (Preamble) A long radiograph that shows how the overall alignment of the limb can be derived. “Mechanical axis”3 is based on the centers of the hip, knee, and ankle and may be expressed in two ways: as a line or an angle. Line 1 is drawn from the hip to the ankle, and the mechanical axis is described as a distance from the center of the knee joint. Alternately, it can be depicted as the intersection of the line from the center of the hip to the center of the knee with the line from the center of the knee to the ankle, as in Angle 2. Consistent rotation of the limb is important to the accuracy of these studies.4 Surgical navigation systems typically “image” the mechanical axis. (B) Close up of how these 2 methods give us information about the knee joint: as a mechanical axis of 13.4 degrees or a “line of force” that lies outside the knee joint.4 (C) The “anatomic axis” is the angle formed by the intersection of the medullary canals of the tibia and the femur. In general, it is a less-reliable depiction of limb alignment, but, on the basis of shorter radiographs, it is easier and cheaper to obtain. Intramedullary surgical alignment guides follow the anatomic axis.
Dr. Vince: Let’s take it to the patient’s bedside and see how and what we do in terms of alignment. This is a preoperative of a case that I presented at the December 2008 Current Concepts in Joint Replacement meeting in Orlando. I went back to New Zealand to operate on the patient with the panel’s advice. She is a 37-year-old woman. Formerly an elite field hockey player, she is currently a hockey coach. She has normal hip joints—there will be no secret hip disease today. This was her knee x-ray, before surgery. Leo, how you would manage this woman, now in need of surgical treatment? (Fig. 4A).
Figure 3 Pie chart comparing survivorship of 293 TKAs with better mechanical alignment (to within 3 degrees of a neutral axis) at 14 years after surgery, with that of 106 TKAs that were less well corrected (more than 3 degrees deviation from a neutral mechanical axis), raising the question of what other factors are important to survivorship.
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Figure 4 Case (1): Who is a candidate for HTO? Radiographs of a 37-year-old woman who was formerly an elite field hockey player and who is currently a coach. The knee extends fully and flexes to 128 degrees with an intact anterior cruciate ligament. (A) The anteroposterior pelvis radiograph shows neither hip pathology that could be responsible for referred pain to the knee nor deformity of the proximal femur. (B) The anteroposterior knee radiograph shows medial compartment arthritis and (C) lateral radiographs show normal patellar height. (D) Patellofemoral radiograph shows a “centrally tracking” patella with minimal, if any, arthritic deterioration. Pre- and post-operative long leg films with mechanical axis shown as one line from hip to ankle. (E) Preoperative mechanical axis passing through medial compartment. (F) Close up view of (E) showing precisely how far medial the mechanical axis lies in the medial compartment. (G) Comparable close-up view after opening wedge medial osteotomy showing mechanical axis through the tibial spines, at about the “50% point.” (H) The full-length post osteotomy radiograph from which (G) was derived. For the osteotomy, the location of the axis is probably more important than either the anatomic axis or the angle of the mechanical axis, showing as it does, where the load crosses the knee joint.
Challenges in Knee Surgery Dr. Whiteside: If this came down to surgery, I’d almost certainly offer her a uni-compartmental knee if she had a stable knee, and if she were psychologically up for that. And if she weren’t, then I would probably proceed to a total knee for her. Dr. Vince: Let’s have quick answers starting with Aaron. What operation would you suggest for this woman? Dr. Rosenberg: Uni-compartmental arthroplasty. Dr. Vince: And Dickey? Dr. Jones: I’m not going to operate on her until I’ve got her going through a whole process, then eventually I’m going to do a total knee with a rotating platform. Dr. Vince: Keith? Dr. Berend: I’d want a valgus stress view to ensure her deformity is correctable that her lateral side is normal and her anterior cruciate ligament is intact. Then, I’d do a mobile bearing medial compartment uni. Dr. Pagnano: This is a patient in the age group in which I’d talk to her about an upper tibial osteotomy versus uni-compartmental. Dr. Rosenberg: If it was a man, I would too, but you have to put so much valgus in osteotomies that the patients look “windswept.” Dr. Berend: We can argue about that. I would say that an upper tibial osteotomy that’s not overcorrected is certainly a consideration. Dr. Vince: Well, I have to do my recertification examination in 2 months, and you guys are starting to make me nervous now. This is a 37-year-old patient. If you did a high tibial osteotomy, what alignment would you shoot for? First of all, who on the panel has done an osteotomy in the last 12 months? OK. Who refers patients for osteotomies elsewhere? OK. Fair enough. (Two panelists perform osteotomies by show of hands.) Mark, where would you like to see the alignment after a high tibial osteotomy (HTO), remembering Mark Coventry’s early work, where the recommended alignment was something that’s difficult for patients to be happy with these days: 10 or more degrees of valgus.5 What’s your current recommendation on an osteotomy, alignment wise? Dr Pagnano: For an upper tibial osteotomy, my alignment goal is the 62% coordinate as measured from medial to lateral.6 That typically corresponds to the down slope of the lateral tibial eminence. So it is a trace of overcorrection, and I measure that intraoperatively. Dr. Vince: So if we consider these pre- and postoperative x-rays, and then zoom in on the knee joint to see the alignment clearly, is this where the axis should be, or does the successful osteotomy need more correction? (Fig. 4B). Dr. Rosenberg: I think the successful osteotomy in general needs to correct more than that. You have to unload the compartment consistently, I think, to get a good clinical result. Dr. Vince: OK, and presumably that is why you probably did not favor an osteotomy, because of the necessary valgus alignment. Dr. Whiteside: And you have to do that “unload” in midstance phase. You can watch the patient walk and know if
119 you did it or not, because if they laterally thrust in midstance, you didn’t make it. If they medially thrust in midstance, you probably did it.7 Dr. Vince: So I take it that you favor an arthroplasty, because to go much more than this x-ray is going to be cosmetically unappealing to the patient. Dr. Rosenberg: Which I would do in a 37-year-old male patient who’s still playing hockey actively. I wouldn’t hesitate to put him into some valgus and tell him he’s going to look a little bit funky, but his pain relief should be better with more correction. Dr. Vince: OK. Dr. Berend: I think if you aim for that 62% coordinate, very few patients complain about the appearance of their leg. Coventry picked 9 to 11 degrees tibiofemoral angle. You see a big cosmetic and mechanical difference with that much valgus. But the difference between this x-ray and halfway over to that other lateral line is not going to produce any difference in real cosmetic appearance, and it might be enough to produce a satisfactory result. Dr. Rosenberg: That’s the problem. It might be enough, but I know if I get over to that other line, it’s going to be enough in general to get better pain relief. Which is why, in a female patient, I’m starting to be hesitant. Some serious female athletes will say; “I don’t care what it looks like, I have to go out and play.” In those cases, I think an osteotomy is a good idea. I’m just concerned if I only reproduce the neutral mechanical axis, the patient is going to say in a year that it’s hurting again, and then you’re back to where you started. The other question in my mind is; “how much time do you need to give them with this operation to justify it?” If you can give them 5 good years, hey, I’m all for it. If you only give them 6 months, it’s not worth it. Dr. Berend: Is 5 good years from 37 to 42 enough? That’s not enough, is it? Dr. Vince: I would say that those are very active years that place considerable demand on an arthroplasty. So far, this patient feels better and I think that 5 good years would definitely be worth it.
Case 2 Dr. Vince: Let’s consider the next case, a painful arthritic knee, with normal hip joints (Fig. 5).8,9 On your left, the anatomic alignment angle is 2.4 degrees of valgus and on your right, the mechanical axis is 7.3 degrees of varus. Is this a varus knee or a valgus knee? Dickey, what would you say? Dr. Jones: It’s a varus knee, but I would watch the patient walk. Dr. Vince: OK. And why would you say it’s a varus knee? Dr. Jones: Because I believe we will see a lateral thrust in mid-stance, with medial compartment loading. Dr. Vince: So it’s because of the pathology in the medial compartment. And Leo, what would you recommend for this patient? Dr. Whiteside: Well, I’d put that knee in 5 degrees valgus, just like any other knee, but this is a mechanically varus knee
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Figure 5 Case (2): Is this a varus or valgus knee? (A) Short radiographs show 2.4 degrees of anatomic valgus alignment. The panel has identified a significant valgus (more proximal distal lateral articular surface) orientation of the distal femoral condyle (black line) with corresponding varus orientation of the proximal tibia (medial tibial plateau lower than lateral). The lateral femoral condyle is “smaller” distally, and posteriorly. This means that the posterior articular condylar surface is more “internally rotated” relative to the epicondylar axis with implications for internal malrotation of the femoral component at arthroplasty8 (see Moreland9; Figure 8). (B) Full-length radiograph showing 7.4 degrees of varus mechanical alignment (yellow lines) and a mechanical axis through the medial compartment at the point of maximum joint space loss. (C) Full-length radiograph after medial unicompartmental arthroplasty with slightly lateral shift of mechanical axis. (D) and (E) Close up of the mechanical axis as a straight line before and after UKA-position effectively unchanged. (F) and (G) Anatomic axis before and after UKA. There is slight increase in valgus anatomic alignment corresponding to the “correctible” component of “pseudo-laxity.” (H) and (I) Conventional postoperative anteroposterior and lateral radiographs. The panel has agreed that this, virtually unchanged alignment, is appropriate for UKA.
with a valgus femur. So when you flex that knee, you have to realize that the lateral femoral condyle is going to be deficient, and if you don’t watch it, you’ll severely internally rotate the femoral component. One of the most common errors that I see is assuming that the femur of a varus knee is normal in flexion. Dr. Vince: That’s a very good point. Now, Mark, you and your group did a study, I believe, of proximal tibial articulation angles, and whether, as the proximal tibia had more varus that there were implications for rotation.8 Can you share that with us? Dr. Pagnano: Exactly what Leo just outlined. If you have a varus inclination to the tibial joint line more than 3.3 degrees, we saw statistically increased incidence of internal rotation of the femoral component. (Moderator note: The posterior femoral articulator surface was internally rotated relative to the trans-epicondylar axis more than the usual 3-5 degrees10). So you have to pay attention, because in this respect they act like a valgus knee. Avoid internally rotating the femoral component. Dr. Vince: That’s a confusing problem. Dr. Whiteside: The way to solve this problem is just to use the anteroposterior axis for cutting your femur in flexion, and that will solve the problem. Or, if you’re good at finding the epicondylar axis, pretty much the same sort of thing.
Dr. Vince: Would the audience know that anteroposterior axis by some other name, Leo? Dr. Whiteside: I don’t, but— Dr. Vince: No? OK. Dr. Whiteside: I’ve heard it. Dr. Vince: Aaron, would you know it by some other name? Dr. Rosenberg: Yeah, I know it by some other name. It’s “Rose”—no, it’s “Whiteside’s line!”11,12 The other effect (increased distal femoral valgus in a knee with varus alignment) was first brought to my attention about 15 years ago by the Japanese, who see this pretty commonly, and they call it the “valgus-varus” knee, where your femur is in valgus and your tibial is in varus. So being able to identify it is important primarily because of the rotational implications. Dr. Vince: Would anybody on the panel do something other than a total knee arthroplasty for this patient? Keith, what’s your recommendation? Dr. Berend: I’m going to do a valgus stress x-ray, because if you go back to the lateral, it looks like anteriorly based disease. If you do a valgus stress x-ray, this knee’s going to line up and look like it’s in a little valgus, and that’s fine. Dr. Vince: So are you saying this is a contender for an operation other than a total knee? Dr. Berend: I would get a valgus stress x-ray and if it corrected to normal, which means the lateral side stays open
Challenges in Knee Surgery and the medial joint space opens up, I wouldn’t care about overall alignment; I would do a partial knee replacement. Dr. Vince: And indeed that’s what I did. Dr. Berend: There you go. Good boy. Dr. Vince: Maybe they’ll recertify me this year after all. So here we have the change in alignment. Is that acceptable, considering that we’re not supposed to overcorrect unicompartmental arthroplasties? Leo, first of all, do you do any “unis?” Dr. Whiteside: I do, and I certainly would not disagree with considering that patient for a uni. Dr. Vince: OK. Fair enough. Dickey, do you do unicompartmental replacements? Dr. Jones: No, sir. Dr. Vince: OK Dickey, you can take a break. Aaron? Dr. Rosenberg: Yes, I do. Dr. Vince: And how about correction? I would argue that I tried only to correct this to neutral, but if we encounter some “normal” laxity on the medial side, would that be a good guideline for the alignment? Dr. Rosenberg: Yeah, I don’t even correct them to neutral. I think undercorrection is the way to go. Dr. Vince: Keith, what is it in the surgical technique that leads to overcorrection when doing a unicompartmental? Dr. Berend: Damage to the medial collateral ligament (MCL). Dr. Vince: Mark, anything else to add to that? How do people end up with unintended overcorrection in valgus after a medial unicompartmental arthroplasty? Dr. Pagnano: I think it’s fundamentally the thickness of the poly insert that determines the correction. Dr. Vince: I would agree, adding that effect to Keith’s observation. Dr. Pagnano: If you don’t have a way to link your femoral and tibial cuts with your instrumentation, and you make those cuts separately, and you’re fixated on putting in a certain thickness, like in this system putting in a 10-millimeter insert, you may overcorrect a subset of those patients. Dr. Berend: It’s nearly impossible to, quote, “overcorrect” a patient unless you’ve peeled up their MCL. Dr. Rosenberg: It’s hard to put the poly in if the MCL is tight. So it’s hard to put them into “overcorrection.” Dr. Vince: So I think we’ve got the complete answer between Keith and Mark. Keith saying that if something lengthens the MCL, and then as Mark is saying the surgeon tries to stabilize it by putting in thicker poly. But, we agree that unlike total knee arthroplasty, it has nothing to do with the angle of the bone cuts. Let’s move on. And what do you think about this kind of alignment (Fig. 5)? Is this acceptable, Keith? Dr. Berend: Perfect.
Case 3 Dr. Vince: Here’s a wobbly, painful arthritic knee (Fig. 6). Leo, what do you recommend for this patient? Dr. Whiteside: This looks like an unstable knee, with hyperextension and interesting varus.
121 Dr. Vince: Yep. Dr. Whiteside: I would be ready to use all the tricks I know to end up with a stable knee in this.13 Dr. Vince: Right. I shy away from cases of neurologic recurvatum, polio, for example. But I would argue this is structural recurvatum. What do you think, Keith? Dr. Berend: I agree completely. You have massive flexion over the distal femur. Dr. Vince: Yes, an exaggerated anterior femoral bow there. So what do you do differently? Dr. Berend: I would use some type of instrumentation to help me line this leg up a little more accurately than intramedullary alignment. I would use a preoperative magnetic resonance custom knee or standard navigation. Dr. Vince: Dickey, are you going to need something like that? Dr. Jones: I think that’s an interesting concept, but it’s not the practice in our University Medical Center. Dr. Vince: Why is this patient in recurvatum? Dr. Jones: I think the recurvatum is directly related to the large anterior bow at the diaphyseal metaphyseal junction. Dr. Vince: Yes, because functionally this woman doesn’t walk down the street with everyone commenting: “oh, my goodness, you’re in hyperextension!” Aaron, what’s your insight? Dr. Rosenberg: I think that the first thing to do for a patient with radiographic recurvatum or a substantial femoral bow is to identify the origin of problem. So you have to look higher up the femur. Does she have fibrous dysplasia? Is this something that happened because of growth? And she’s lived with it for many years. Is it a post-traumatic deformity? Did she have an injury in childhood? I would agree that this looks structural. But the key message is if somebody is in recurvatum, it’s either a mild degree that they have had since they were young, and commonly associated with valgus in females or if it is acquired in older age and it is progressive, you have to work them up neurologically because those can be disastrous after TKA. Dr. Jones: One of the reasons for recurvatum here is the long posterior capsule. When you reestablish the joint line with standard bone cuts, consider the effect of that posterior capsule. Dr. Vince: Mark—let me put a question to you. Polio is our prototype for recurvatum.14 They have weak quadriceps and have to lock their knee in hyperextension to walk. It strikes me that some people who have painful patellas walk like that. And then, if the body mass index is high, and the load across the patella is greater because of weight, some people will not like to bend their knee very much when they walk due to patellar pain. Do you see that phenomenon? Dr. Pagnano: That specific one, I haven’t noted myself. I think this just highlights another aspect of alignment. We know relatively little about axial alignment in the coronal plane, and we know even less about alignment in the sagittal plane. So what’s going on with this patient’s hip? Dr. Vince: The hip is satisfactory. Here are the radiographs after TKA. Leo, where would you like to see that red mechanical axis line?
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Figure 6 Case (3): Alignment for TKA and sagittal plane stability. (A) Short radiographs showing 14 degrees of varus deformity with opening of the lateral compartment. (B) Hyperextension with “opening” of the posterior soft tissue structures. (C) Patellofemoral view showing a centrally tracking but arthritic patello-femoral joint. (D) Postoperative short radiograph showing 6.5 degrees of anatomic valgus alignment. Medial release has been performed, and medial structures now lengthened and equal to lateral side, but posterior structures still elongated. (E) Postoperative, single-leg weight-bearing, lateral radiograph showing hyperextension similar to preoperative status.
Dr. Whiteside: That looks good. I can’t argue with that. Dr. Vince: OK. Mark, Is that within the threshold? Dr. Pagnano: Looks good. Dr. Vince: OK, and there’s the close-up. If I were smart, I wouldn’t show you anything else. However, I have always done lateral x-rays with the patient standing on one leg. And I’ll just give everybody in the audience a piece of advice, if you want to feel good at the end of the day, don’t do those in your practice as they reveal recurvatum and flexion contractures you never thought were there. Really, just don’t do them. This is what a single leg weight-bearing lateral radiograph shows us. She is quite happy with her knee, but I find the recurvatum distressing, and I fear it may be bound for doom. Dr. Jones: Is that a cruciate retaining or—
Dr. Vince: That’s a posterior stabilizer. Do you think a cruciate retaining would help? Dr. Jones: Well, I worry about the impingement on the post in hyperextension. Dr. Vince: Absolutely. Dr. Jones: You’ve got 6 degrees of tibial slope and probably 15 degrees of hyperextension, and most posterior stabilized knee designs won’t tolerate that. Dr. Vince: Leo, I’ve always looked to you for insights into soft-tissue problems. When I reflect on this knee, it seems that the collaterals were about the same length to each other, but if I think 3-dimensionally, and include the posterior structures, to Dickey’s point about the long posterior capsule, it is longer than the collaterals. What should I have done to avoid this problem?
Challenges in Knee Surgery Dr. Whiteside: In general, if you have laxity of the entire knee in extension, then just distalize the joint by resecting less distal femur. That affects extension only. Laxity in flexion and extension will require a thicker tibial component. But in this case, you’ve got a deformed femur and an excessively long posterior capsule. So I would do what you did. Maybe a little bit more of distalization of the distal femur. You followed the curvature of the femur with the femoral component position. I would however use a cruciate retaining knee. A posterior stabilized knee is in danger of shearing off the tibial post. So I think you make a few compromises, and you end up with a knee that looks good. Dr. Vince: Dickey, you and I make a good pair because I hate hinges, and you really do a good job with them. Was that the answer here? Dr. Jones: I wouldn’t have used a hinge, no. I agree. The answer is to cut less distal femur, try to avoid hyperextension mode. But then, she comes back, and because she’s walked in hyperextension all her life, and she now doesn’t like walking without it. So that’s got to end up being a problem.15 Dr. Vince: One of my fears with a case like this is the narrow knife-edge either side of full extension. If you leave a person like this with a little flexion contracture, the knee buckles. And if you go past full extension and give them a little recurvatum that they like, they increase it over time. For all of you in the audience, please work on the answer to this problem for us by next year, if you don’t mind.
Case 4 Dr. Vince: Our colleagues overseas, who are well represented at this meeting, regularly deal with big deformities, of the sort that we haven’t dealt with in volume in the United States for 20 or 30 years. I was working in India 2 weeks ago, and this would be a “bread and butter” case there (Fig. 7). This patient walks with instability. The lateral x-ray has multiple deformities as well. Keith, what’s your approach to this severe varus deformity? First of all, are you going to do bilateral or staged? Dr. Berend: When we do Operation Walk in Nicaragua and Guatemala, this is a standard deformity. Bilateral surgery should be on the basis of the patient’s comorbidities. The most important one that we saw at the Knee Society Specialty Day this year is heart failure. So, no heart failure, I’d do simultaneous bilateral. And I’d approach these knees right from the start with a giant medial release, and get them . . . try to get them straight. Dr. Vince: Leo, if we do one knee like this in a patient with a flexion contracture on both sides, they’re going to have a much longer leg because of the arthroplasty. Unless we put a huge shoe lift under the unoperated leg, the flexion contracture will come back on the TKA. Dr. Whiteside: That may be true. I tend to not do bilateral knees, but I think that may be a reasonable case for doing bilateral knees, unless it’s a sick patient. If it’s a sick patient, that’s a fairly thin excuse to do bilateral knees. I think if I taught the patient to work on full extension all the time, and
123 then in 3 months when their health returned to a certain extent, I’d go back and do the other knee. I still am very careful about doing bilateral knees because the average age of my patients is about 74 years old and heavy. Dr. Vince: Right. Aaron, Keith described using a “giant medial release.” I’m glad to hear that classical technique isn’t dead and gone. He sounded pretty confident that he would be going home at the end of the day with a success. Can you assure me that a “giant medial release” is all you’re going to need here? Dr. Rosenberg: Well, the question is, to what extent are there other instabilities? If the lateral side is not grossly unstable, you can, in the vast majority of the cases, even with this much deformity, release the entire MCL down along the tibia. In some cases, after you’ve released it with a long elevator, 12 to 14 cm down that medial side, you will have to put a big spacer block in there. During this procedure, my residents are wondering, “what are you doing?” and it (the medial side) goes “pop,” and the whole medial sleeve just pulls off. The patients do well, but you have to work at the correction. In addition, you can cut off some of that medial tibia to loosen the medial soft tissues. You can get these knees out straight. We see about 2 or 3 cases like this a year from people in the neighborhood, we used to see them every day. Generally, you do a standard medial release. Jerry Engh has talked about doing a medial epicondylar osteotomy,16 but I don’t think it’s necessary. Dr. Vince: Mark, is this a patient in whom alignment really does matter? Dr. Pagnano: Oh, I think it does. What you don’t want to risk is an early failure from instability. I think the first thing is to get that knee well balanced, so ligament balancing is the cornerstone. Alignment is secondary, but still important. Dr. Vince: Have you ever had Aaron’s experience where not only do you do Keith’s release, but you put the osteotome down the medial side to strip it like Aaron does, and then discover it’s unstable? Dr. Pagnano: Yeah, I think that happens when you push the leg beyond where it should be corrected. So you feel the “pop” that Aaron described, then the resident goes one step beyond and stretches it out into 10 degrees of valgus for 2 seconds. Now you’ve pulled the MCL all the way up the medial side, and that’s when you need to do something else: either directly repair the MCL back to the tibia or switch to a constrained condylar device. Dr. Vince: I was brought up to believe that constrained implants were the “last resort of the incompetent.” And thanks Leo; you’ve done nothing in the last 20 years to help me escape that idea! But, as you see from the postoperative x-rays, I felt the need of an insurance policy for this lady. The lateral, not the medial, side was unstable after the medial releases and I couldn’t accept it. She has quite a wide thigh girth, and as much as I dislike constraint in a primary arthroplasty, I believe now that with good bone cuts and fully cemented short stems, they will be durable. I don’t like constrained implants with uncemented stems in primary arthroplasties, unlike revisions where I think diaphyseal
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Figure 7 Case (4): Severe varus deformity and the role of constraint. Preoperative radiographs. (A) Right lateral. (B) Right anteroposterior with 26 degrees of anatomic varus, attenuation of lateral structures and subluxation. (C) Anteroposterior view of left knee with 28 degrees of anatomic varus and similar ligamentous laxity. (D) Lateral radiograph of left knee with exaggerated posterior tibial slope-will you reproduce this slope at TKA? (E) Postoperative anteroposterior radiograph of right TKA with nonlinked constrained implants and fully cemented “stubby” stem extensions. (F) Postoperative radiograph of left TKA with constrained implant and auto graft reconstruction of medial femoral condyle using distal femur and a “Sculco” technique. (G) Bilateral full-length radiographs showing mechanical axes still passing through the medial compartments. Is this enough valgus alignment?
uncemented stems are highly advantageous. Is there any alternative to this? Dickey? Dr. Jones: I know my friends in India have shown me lots of femurs that require 9 degrees of valgus in the distal cut to compensate for a large femoral bow. Dr. Vince: There’s a big femoral bow in this case.
Dr. Jones: So, for these huge deformities, you sometimes are going to need revision implants ready, even though it’s a primary, because of the severity of the deformity. This is one such. Dr. Rosenberg: You have to remember that metabolic bone disease and nutritional deficiencies may be more prev-
Challenges in Knee Surgery alent in some countries and lead to significant deformities of the femur. Dr. Vince: Consider the mechanical axis. I’m not terribly happy to have that weight-bearing axis a little on the medial side, because I think this woman has dynamic features that exacerbate varus in her gait. And I think, Mark, this is what you’ve been saying; that for this particular patient, alignment is tremendously important. Dr. Rosenberg: I think it’s important, but I would say probably this woman isn’t going to go out and try to play basketball. She’s too short! This is the type of patient who had horrible knees and who is grateful to get up and walk to the kitchen or the grocery store. And I wouldn’t worry about the long-term survival based on the alignment in her. Dr. Whiteside: This is the size of thigh that if you put the knees in 5 degrees of valgus, the feet are going to be a footand-a-half apart. Slight varus is acceptable. Dr. Vince: Very important point. If I give this lady more valgus, her stance is going to be so wide that she immediately goes from a dynamic varus force to a dynamic valgus force, and instability in the obese patient has been a serious problem.17,18 Dr. Jones: Many really large patients walk by circumducting the limb. And so you nearly always see a valgus deformity because of the valgus moment at heel strike. Dr. Vince: Gait problems may be compounded by relative hip abductor weakness with respect to body weight that requires shifting the center of gravity over the knee during stance phase with a large valgus moment on the knee.17 Keith, I had a defect on the medial tibia and I used the technique that Tom Sculco19 described so nicely, cutting the defect into a flat slope, then putting the distal femoral condylar bone cut on there, opposing cancellous to cancellous bone. Is this one where you would use something else? Dr. Berend: It’s probably not big enough to consider doing anything else. This is a great technique except that the bone is not really loaded, so I don’t know if it will stay there long term. I would use the screws and cement technique that Merrill Ritter has written up, with outstanding survivorship, prepare the sclerotic bone, put in a couple screws to function as “rebar,” then cement the component. The other thing you’ll notice is where those screws are hanging over, if you remove that medial flange from the tibia and downsize the tibial component, you can use less of a release on the medial side.20 Dr. Vince: In a short stature patient like this, you can rapidly get into trouble with the need for small sized constrained components. The other technique I used in this case was to automatically resect an additional 5 mm of distal femoral bone, not to correct the flexion contracture but to harvest a bigger chunk of distal femur for the medial tibial defect, with the intention of putting a distal augment on the femur. That worked well.
Case 5 This case gave me some serious grief. This is a delightful gentleman patient from Tonga. Single-leg weight-bearing xrays show that the deformity is greater than anticipated. This
125 is a similar flavor to the last case but in a very large man. This is the early postoperative film (Fig. 8). He required the largest femoral size in the kit, and that size does not come in a constrained option. I was fairly happy with what we had immediately postoperatively, but not some of the later films that you see there, which are distressing. And about 6 weeks later, his 400-plus pounds really did something to my reconstruction. When we see him walking, there’s a dynamic, varus force or “lateral thrust” on his knee. At revision surgery, he had snapped his lateral collateral ligament. So Leo, what should I have done here? Dr. Whiteside: I think you pointed out that this is a knee that was unstable laterally to begin with. And the common issue is to fail to do enough medial release and then fail to achieve tight enough lateral structures. It is also a problem to leave the tibial bone cut in too much varus. All that together will give you a knee that’s unstable on the lateral side. So I don’t think there is any stabilized knee in the world that will withstand the kind of loads that one is going to see. So with this type of varus knee, I would be very careful to make a perpendicular tibial cut. Then, because of the length of his thigh, I would cut the femur at a 3-degree valgus angle rather than my usual 5. I would do enough release medially to be sure that I had tight lateral structures and full extension. Dr. Vince: I think your point is very, very important in terms of there being no constrained device that’s going to resist these loads. Dickey, would you agree? Dr. Jones: Absolutely. Yes. Dr. Vince: OK. We have to decrease the destructive load on this knee and I would say I failed to do that. I should have given this man more valgus alignment. Dr. Whiteside: Or just continue to release medially and achieve tension laterally. Dr. Rosenberg: Is this x-ray (Figure 8I) what the knee looked like when he was laying down, and then he got up to walk and he began to open up on the lateral side? Dr. Vince: Initially it looked like this lying and standing, but he started to open progressively. By the time I went back to revise it, the lateral collateral ligament had snapped. But I think I left this primary TKA with too much varus deforming force. Dr. Rosenberg: Yeah. Dr. Vince: And then, to compound things, I broke one of my own revision rules. I try to get everybody else to do complete revisions, and I didn’t revise this tibia because it was well fixed and it had a stem extension.21-23 I used this nonlinked constrained femoral component and supplemented it with an Achilles tendon allograft to reconstruct the lateral side. To date, he’s still stable, but I’m worried by his size and the forces involved. Dr. Vince: To our audience, I thank you for your patience. Gentlemen on the panel, I appreciate your input and I think everyone in the room thanks you for sharing your experience and thoughts.
Moderator’s Comments Alignment, an elemental precept in knee arthroplasty, is presumably something on which everyone agrees. New discus-
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Figure 8 Case (5): Very severe varus deformity, with “dynamic” instability and flexion contracture. (A) and (B) Preoperative varus deformities with 17.3 degrees of anatomic varus on the right in a patient with a significant lateral thrust on ambulation. Appears magnified because of fixed flexion contracture. (C) and (D) AP and lateral radiographs of right TKA, difficult to interpret because of rotated limb on radiograph, but appears to have inadequate correction of varus deformity. (E) and (F) Correctly rotated AP and lateral radiographs of left knee, showing the intended 6.8 degrees of valgus anatomic alignment. (G) Full-length postoperative radiographs showing unsatisfactory alignment and stability on right TKA with opening of lateral structures and mechanical axis medial to the medial compartment. Left TKA has satisfactory alignment and stability. (H) Postoperative anatomic axis of right TKA, not single leg weight bearing, showing asymmetry of extension gap and lateral instability. (I) Postoperative AP radiograph of left TKA with satisfactory alignment and stability. (J) By 4 months, the overload to the lateral structures resulted in rupture of the lateral collateral ligament and instability. (K) AP radiograph after revision of femoral component with constrained implant and Achilles allograft reconstruction of the lateral structures. Press fit diaphyseal stem was placed after preferential lateral endosteal reaming to increase valgus position. Offset stem used to centralize femoral component. Tibial component, installed in slight varus alignment could have been revised to advantage, to decrease varus loading, but was not.
sions have arisen on this old topic, some prompted by surgical navigation. Intramedullary instrumentation works from “anatomic alignment” (the axes of the tibia and femur) and navigation from the mechanical axis. The goal of arthroplasty technique may be: (1) undercorrection, believing that “natural” ligament balance is pre-eminent; (2) neutral mechanical axis (which doesn’t equate with equal load on medial and lateral compartments); and (3) overcorrection (that aims to reduce the destructive forces resulting from varus or valgus pathology).
Case 1 was intended as an “ideal” indication for HTO, with the exception of female gender. If an athletically active 37year-old patient with single compartment disease is not a candidate for osteotomy, then few other patients can be. Few data exist to support the idea of uni-compartmental arthroplasty (UKA) in this age group. The ideal alignment after osteotomy, balancing pain relief against cosmesis was a central discussion point. Case 2 is neither rare nor easy to define as simply varus or valgus. I would characterize it as “varus” because of the me-
Challenges in Knee Surgery dial compartment loading pattern and resultant disease. It highlights above average varus tibial slope and the implications for the relationship of the posterior femoral condylar angle and the trans-epicondylar axis. This case was selected as an ideal candidate for UKA and the topic for discussion included ideal alignment for UKA, which is different from that for HTO and TKA. Case 3 demonstrates challenges with recurvatum that is structural (and not neurologic in origin) plus extra-articular deformity in the plane of motion of the joint. These cases are at high risk for failure from progressive recurvatum and preventive action during the primary surgery was the question for the panel. Case 4 was a knee with severe varus deformity, exploring the ideal alignment and soft tissue balancing that are required, plus the role of constraint. Alignment, it may be argued moderates the load on medial and lateral compartments while the collateral ligaments provide stability. The better the alignment is “balanced” the less severe the loads that will be on the collateral ligaments. As surgeons we frequently like to depict the medial ligament in a varus deformity as “abnormal” and that our releases will make it “normal” and equal to the lateral side. In truth, the greater pathology in this knee is the convex, lateral side. If lateral integrity has fallen victim to the extreme deformity, constraint is necessary. Some surgeons believed that leaving residual varus deformity is somehow more “normal” for this patient, and sustains functional tension in the lateral collateral ligament. I am not one of those surgeons. Case 5 expounds on the points from Case 4 — here, the size of the patient made constraint a dubious option, and inadvertent residual varus deformity resulted in early instability of the primary arthroplasty when the overloaded lateral collateral ligament failed. I feel this case argues strongly against the concept of undercorrection. The concept of achieving success by maintaining tension in the collateral ligaments failed in this case.
References 1. Pagnano MW, Trousdale RT, Berry DJ, et al: The mechanical axis May be the wrong target in computer-assisted TKA, in Annual Meeting of the American Academy of Orthopedic Surgeons, San Francisco, CA, 2008 2. Pearle A, Kendoff D: Perspectives on computer-assisted orthopedic surgery: Movement toward quantitative orthopedic surgery. J Bone Joint Surg 91:7-12, 2009 3. Moreland JR, Bassett LW, Hanker GJ: Radiographic analysis of the axial alignment of the lower extremity. J Bone Joint Surg Am 69:745-749, 1987
127 4. NehratJiang CC, Insall JN: Effect of rotation on the axial alignment of the femur. Pitfalls in the use of femoral intramedullary guides in total knee arthroplasty. Orthopade 248:50-56, 1989 5. Coventry MB: Proximal tibial varus osteotomy for osteoarthritis of the lateral compartment of the knee. J Bone Joint Surg Am 69:32-38, 1987 6. Kennedy WR, White RP: Unicompartmental arthroplasty of the knee. Postoperative alignment and its influence on overall results. Clin Orthop 221:278-285, 1987 7. Hurwitz DE, Ryals AB, Case JP, et al: The knee adduction moment during gait in subjects with knee osteoarthritis is more closely correlated with static alignment than radiographic disease severity, toe out angle and pain. J Orthop Res 20:101-107, 2002 9. Moreland JR: Mechanisms of failure in total knee arthroplasty. Clin Orthop 226:49-64, 1988 8. Pagnano MW, Hanssen AD: Varus tibial joint line obliquity: a potential cause of femoral component malrotation. Clin Orthop Relat Res 392: 68-74, 2001 10. Berger RA, et al: Determining the rotational alignment of the femoral component in total knee arthroplasty using the epicondylar axis. Clin Orthop 286:40-47, 1993 11. Whiteside LA, Arima J: The anteroposterior axis for femoral rotational alignment in valgus total knee arthroplasty. Clin Orthop 321:168-172, 1995 12. Arima J, Whiteside LA, McCarthy DS, et al: Femoral rotational alignment, based on the anteroposterior axis, in total knee arthroplasty in a valgus knee. A technical note. J Bone Joint Surg Am 77:1331-1334, 1995 13. Whiteside LA, Mihalko WM: Surgical procedure for flexion contracture and recurvatum in total knee arthroplasty. Clin Orthop 404:189-195, 2002 14. Insall J: Total Knee Arthroplasty, in Windsor RE, Scott WN (eds): Surgery of the Knee, New York, Churchill Livingston, 1984 15. Meding JB, Keating EM, Ritter MA, et al: Genu recurvatum in total knee replacement. Clin Orthop Relat Res 416:64-67, 2003 16. Engh GA: Medial epicondylar osteotomy: a technique used with primary and revision total knee arthroplasty to improve surgical exposure and correct varus deformity. Instr Course Lect 48:153-156, 1999 17. Vince KG, Abdeen A, Sugimori T: The unstable total knee arthroplasty: causes and cures. J Arthroplasty 21:44-49, 2006 (suppl) 18. Winiarsky R, Barth P, Lotke P: Total knee arthroplasty in morbidly obese patients. J Bone Joint Surg Am 80:1770-1774, 1998 19. Windsor RE, Insall JN, Sculco TP: Bone grafting of tibial defects in primary and revision total knee arthroplasty. Clin Orthop 205:132137, 1986 20. Lotke PA, Wong RY, Ecker ML: The use of methylmethacrylate in primary total knee replacements with large tibial defects. Clin Orthop 270:288-294, 1991 21. Vince K, Bedard M: Implanting the revision total knee arthroplasty, in Lotke, PA and Lonner J (eds): Master Techniques in Orthopedic Surgery. Baltimore, Lippincott, Williams and Wilkins, 2008, pp 203-228 22. Fehring TK, Odum S, Griffin WL, et al: Outcome comparison of partial and full component revision TKA. Clin Orthop Relat Res 440:131-134, 2005 23. Mackay DC, Siddique MS: The results of revision knee arthroplasty with and without retention of secure cemented femoral components. J Bone Joint Surg Br 85:517-520, 2003
Preamble Dr. Vince: Our problem cases all revolve around the issue of alignment, where one might think there is general consensus. I’ve been impressed by the recent article by Pagnano and colleagues,1 “The Mechanical Axis May be the Wrong Target in Computer-Assisted TKA,” in which they evaluated 399 total knee arthroplasties (TKAs) performed by Jim Rand more than a decade ago. We now have computer navigation and greater accuracy, but it’s not clear we agree on the for which targets to aim.2 Just so we can agree on terminology, anatomic alignment is the angle formed by the 2 medullary canals, and mechanical alignment is represented by lines from the centers of the hip, knee and ankle. Mechanical axis can be expressed either as an angle, as you see here, or as a straight line that shows where the axis crosses the knee joint (Fig. 1).3,4 I put in front of our panelists John Insall’s query, when we do knee-replacement surgery, are we reproducing “normal anatomy,” or are we sometimes, reproducing “pathology?” With that pretext, I’d like to assume that most of us are aiming for the kind of result on your left after surgery, not the one on the right (Fig. 2). This is Marks’ work (Fig. 3) I referred to. Jim Rand’s excellent surgeries showed that with a mechanical alignment within ⫾3 degrees of a neutral axis, there was an 84.6% survivorship at 14 years. By comparison, TKAs with worse alignment (more than 3 degrees beyond a neutral axis) had superior survivorship of 87%. This finding turns the world on its head. Leo, can I start with your opinion on this information? Dr. Whiteside: That has not been my experience. I believe alignment matters. And throughout my career, I found that when I’m referred patients who are still crooked, they’re usually symptomatically crooked. Dr. Vince: Fair enough. Mark, I’d like to give you the last word, but meanwhile, Aaron, what do you make of this? Dr. Rosenberg: I think it makes some sense only in reference to what Insall said in your quotation. That is, someone who’s been in varus since birth and has a relative progression 116
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of that varus; if you correct them to a fully neutral mechanical axis, I don’t think they do better than if you correct them back to what they were like when they were 19 or 20. So my tendency has been, in general, not to overcorrect total knees. Dr. Vince: Dickey, what about valgus knees? Dr. Jones: I think it’s important to look at valgus knees differently when you’re doing your alignment, and I will look to 4 or 3 degrees of valgus alignment in patients who have significant valgus of more than 10 degrees preoperatively. Dr. Vince: But 3 to 4 degrees of anatomic valgus represents a considerable correction and perhaps even varus mechanical alignment. Keith? Dr. Berend: I think we saw a great debate earlier this afternoon on these data. If you really, truthfully look at the information in front of us, the explanation is multifactorial, which I think was the conclusion of the study. We don’t know what the target is, but we’re pretty sure that it’s somewhere around 3 degrees. And with the numbers that are in this study in such a relatively small difference in survivorship, it’s hard to tell what the true difference was. In almost every other study with enough knees for statistical power, the dominant factor has been alignment. Dr. Vince: Mark, you’ve been close to these data. What sense do you make of it at this stage? Dr. Pagnano: I believe factors other than alignment are more important than alignment in determining survivorship at 15 years. The reason why Leo sees malaligned knees failing in his practice are that those are the knees that happen to come to see you. The ones that are still aligned, it’s a wear through the polyethylene or something, then the surgeon who did the original surgery might be revising that one. So there’s some selection when you have a referral practice. What this tells me is that spending inordinate amounts of time chasing a 0-degree mechanical alignment is not going to pay off for me at 15 years. And I think we need to spend our efforts looking at other factors and the interplay of the factors if we’re really going to make a difference.
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Figure 2 Universal stick figures begging the question: do you really want undercorrection?
Case 1
Figure 1 (A) (Preamble) A long radiograph that shows how the overall alignment of the limb can be derived. “Mechanical axis”3 is based on the centers of the hip, knee, and ankle and may be expressed in two ways: as a line or an angle. Line 1 is drawn from the hip to the ankle, and the mechanical axis is described as a distance from the center of the knee joint. Alternately, it can be depicted as the intersection of the line from the center of the hip to the center of the knee with the line from the center of the knee to the ankle, as in Angle 2. Consistent rotation of the limb is important to the accuracy of these studies.4 Surgical navigation systems typically “image” the mechanical axis. (B) Close up of how these 2 methods give us information about the knee joint: as a mechanical axis of 13.4 degrees or a “line of force” that lies outside the knee joint.4 (C) The “anatomic axis” is the angle formed by the intersection of the medullary canals of the tibia and the femur. In general, it is a less-reliable depiction of limb alignment, but, on the basis of shorter radiographs, it is easier and cheaper to obtain. Intramedullary surgical alignment guides follow the anatomic axis.
Dr. Vince: Let’s take it to the patient’s bedside and see how and what we do in terms of alignment. This is a preoperative of a case that I presented at the December 2008 Current Concepts in Joint Replacement meeting in Orlando. I went back to New Zealand to operate on the patient with the panel’s advice. She is a 37-year-old woman. Formerly an elite field hockey player, she is currently a hockey coach. She has normal hip joints—there will be no secret hip disease today. This was her knee x-ray, before surgery. Leo, how you would manage this woman, now in need of surgical treatment? (Fig. 4A).
Figure 3 Pie chart comparing survivorship of 293 TKAs with better mechanical alignment (to within 3 degrees of a neutral axis) at 14 years after surgery, with that of 106 TKAs that were less well corrected (more than 3 degrees deviation from a neutral mechanical axis), raising the question of what other factors are important to survivorship.
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Figure 4 Case (1): Who is a candidate for HTO? Radiographs of a 37-year-old woman who was formerly an elite field hockey player and who is currently a coach. The knee extends fully and flexes to 128 degrees with an intact anterior cruciate ligament. (A) The anteroposterior pelvis radiograph shows neither hip pathology that could be responsible for referred pain to the knee nor deformity of the proximal femur. (B) The anteroposterior knee radiograph shows medial compartment arthritis and (C) lateral radiographs show normal patellar height. (D) Patellofemoral radiograph shows a “centrally tracking” patella with minimal, if any, arthritic deterioration. Pre- and post-operative long leg films with mechanical axis shown as one line from hip to ankle. (E) Preoperative mechanical axis passing through medial compartment. (F) Close up view of (E) showing precisely how far medial the mechanical axis lies in the medial compartment. (G) Comparable close-up view after opening wedge medial osteotomy showing mechanical axis through the tibial spines, at about the “50% point.” (H) The full-length post osteotomy radiograph from which (G) was derived. For the osteotomy, the location of the axis is probably more important than either the anatomic axis or the angle of the mechanical axis, showing as it does, where the load crosses the knee joint.
Challenges in Knee Surgery Dr. Whiteside: If this came down to surgery, I’d almost certainly offer her a uni-compartmental knee if she had a stable knee, and if she were psychologically up for that. And if she weren’t, then I would probably proceed to a total knee for her. Dr. Vince: Let’s have quick answers starting with Aaron. What operation would you suggest for this woman? Dr. Rosenberg: Uni-compartmental arthroplasty. Dr. Vince: And Dickey? Dr. Jones: I’m not going to operate on her until I’ve got her going through a whole process, then eventually I’m going to do a total knee with a rotating platform. Dr. Vince: Keith? Dr. Berend: I’d want a valgus stress view to ensure her deformity is correctable that her lateral side is normal and her anterior cruciate ligament is intact. Then, I’d do a mobile bearing medial compartment uni. Dr. Pagnano: This is a patient in the age group in which I’d talk to her about an upper tibial osteotomy versus uni-compartmental. Dr. Rosenberg: If it was a man, I would too, but you have to put so much valgus in osteotomies that the patients look “windswept.” Dr. Berend: We can argue about that. I would say that an upper tibial osteotomy that’s not overcorrected is certainly a consideration. Dr. Vince: Well, I have to do my recertification examination in 2 months, and you guys are starting to make me nervous now. This is a 37-year-old patient. If you did a high tibial osteotomy, what alignment would you shoot for? First of all, who on the panel has done an osteotomy in the last 12 months? OK. Who refers patients for osteotomies elsewhere? OK. Fair enough. (Two panelists perform osteotomies by show of hands.) Mark, where would you like to see the alignment after a high tibial osteotomy (HTO), remembering Mark Coventry’s early work, where the recommended alignment was something that’s difficult for patients to be happy with these days: 10 or more degrees of valgus.5 What’s your current recommendation on an osteotomy, alignment wise? Dr Pagnano: For an upper tibial osteotomy, my alignment goal is the 62% coordinate as measured from medial to lateral.6 That typically corresponds to the down slope of the lateral tibial eminence. So it is a trace of overcorrection, and I measure that intraoperatively. Dr. Vince: So if we consider these pre- and postoperative x-rays, and then zoom in on the knee joint to see the alignment clearly, is this where the axis should be, or does the successful osteotomy need more correction? (Fig. 4B). Dr. Rosenberg: I think the successful osteotomy in general needs to correct more than that. You have to unload the compartment consistently, I think, to get a good clinical result. Dr. Vince: OK, and presumably that is why you probably did not favor an osteotomy, because of the necessary valgus alignment. Dr. Whiteside: And you have to do that “unload” in midstance phase. You can watch the patient walk and know if
119 you did it or not, because if they laterally thrust in midstance, you didn’t make it. If they medially thrust in midstance, you probably did it.7 Dr. Vince: So I take it that you favor an arthroplasty, because to go much more than this x-ray is going to be cosmetically unappealing to the patient. Dr. Rosenberg: Which I would do in a 37-year-old male patient who’s still playing hockey actively. I wouldn’t hesitate to put him into some valgus and tell him he’s going to look a little bit funky, but his pain relief should be better with more correction. Dr. Vince: OK. Dr. Berend: I think if you aim for that 62% coordinate, very few patients complain about the appearance of their leg. Coventry picked 9 to 11 degrees tibiofemoral angle. You see a big cosmetic and mechanical difference with that much valgus. But the difference between this x-ray and halfway over to that other lateral line is not going to produce any difference in real cosmetic appearance, and it might be enough to produce a satisfactory result. Dr. Rosenberg: That’s the problem. It might be enough, but I know if I get over to that other line, it’s going to be enough in general to get better pain relief. Which is why, in a female patient, I’m starting to be hesitant. Some serious female athletes will say; “I don’t care what it looks like, I have to go out and play.” In those cases, I think an osteotomy is a good idea. I’m just concerned if I only reproduce the neutral mechanical axis, the patient is going to say in a year that it’s hurting again, and then you’re back to where you started. The other question in my mind is; “how much time do you need to give them with this operation to justify it?” If you can give them 5 good years, hey, I’m all for it. If you only give them 6 months, it’s not worth it. Dr. Berend: Is 5 good years from 37 to 42 enough? That’s not enough, is it? Dr. Vince: I would say that those are very active years that place considerable demand on an arthroplasty. So far, this patient feels better and I think that 5 good years would definitely be worth it.
Case 2 Dr. Vince: Let’s consider the next case, a painful arthritic knee, with normal hip joints (Fig. 5).8,9 On your left, the anatomic alignment angle is 2.4 degrees of valgus and on your right, the mechanical axis is 7.3 degrees of varus. Is this a varus knee or a valgus knee? Dickey, what would you say? Dr. Jones: It’s a varus knee, but I would watch the patient walk. Dr. Vince: OK. And why would you say it’s a varus knee? Dr. Jones: Because I believe we will see a lateral thrust in mid-stance, with medial compartment loading. Dr. Vince: So it’s because of the pathology in the medial compartment. And Leo, what would you recommend for this patient? Dr. Whiteside: Well, I’d put that knee in 5 degrees valgus, just like any other knee, but this is a mechanically varus knee
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Figure 5 Case (2): Is this a varus or valgus knee? (A) Short radiographs show 2.4 degrees of anatomic valgus alignment. The panel has identified a significant valgus (more proximal distal lateral articular surface) orientation of the distal femoral condyle (black line) with corresponding varus orientation of the proximal tibia (medial tibial plateau lower than lateral). The lateral femoral condyle is “smaller” distally, and posteriorly. This means that the posterior articular condylar surface is more “internally rotated” relative to the epicondylar axis with implications for internal malrotation of the femoral component at arthroplasty8 (see Moreland9; Figure 8). (B) Full-length radiograph showing 7.4 degrees of varus mechanical alignment (yellow lines) and a mechanical axis through the medial compartment at the point of maximum joint space loss. (C) Full-length radiograph after medial unicompartmental arthroplasty with slightly lateral shift of mechanical axis. (D) and (E) Close up of the mechanical axis as a straight line before and after UKA-position effectively unchanged. (F) and (G) Anatomic axis before and after UKA. There is slight increase in valgus anatomic alignment corresponding to the “correctible” component of “pseudo-laxity.” (H) and (I) Conventional postoperative anteroposterior and lateral radiographs. The panel has agreed that this, virtually unchanged alignment, is appropriate for UKA.
with a valgus femur. So when you flex that knee, you have to realize that the lateral femoral condyle is going to be deficient, and if you don’t watch it, you’ll severely internally rotate the femoral component. One of the most common errors that I see is assuming that the femur of a varus knee is normal in flexion. Dr. Vince: That’s a very good point. Now, Mark, you and your group did a study, I believe, of proximal tibial articulation angles, and whether, as the proximal tibia had more varus that there were implications for rotation.8 Can you share that with us? Dr. Pagnano: Exactly what Leo just outlined. If you have a varus inclination to the tibial joint line more than 3.3 degrees, we saw statistically increased incidence of internal rotation of the femoral component. (Moderator note: The posterior femoral articulator surface was internally rotated relative to the trans-epicondylar axis more than the usual 3-5 degrees10). So you have to pay attention, because in this respect they act like a valgus knee. Avoid internally rotating the femoral component. Dr. Vince: That’s a confusing problem. Dr. Whiteside: The way to solve this problem is just to use the anteroposterior axis for cutting your femur in flexion, and that will solve the problem. Or, if you’re good at finding the epicondylar axis, pretty much the same sort of thing.
Dr. Vince: Would the audience know that anteroposterior axis by some other name, Leo? Dr. Whiteside: I don’t, but— Dr. Vince: No? OK. Dr. Whiteside: I’ve heard it. Dr. Vince: Aaron, would you know it by some other name? Dr. Rosenberg: Yeah, I know it by some other name. It’s “Rose”—no, it’s “Whiteside’s line!”11,12 The other effect (increased distal femoral valgus in a knee with varus alignment) was first brought to my attention about 15 years ago by the Japanese, who see this pretty commonly, and they call it the “valgus-varus” knee, where your femur is in valgus and your tibial is in varus. So being able to identify it is important primarily because of the rotational implications. Dr. Vince: Would anybody on the panel do something other than a total knee arthroplasty for this patient? Keith, what’s your recommendation? Dr. Berend: I’m going to do a valgus stress x-ray, because if you go back to the lateral, it looks like anteriorly based disease. If you do a valgus stress x-ray, this knee’s going to line up and look like it’s in a little valgus, and that’s fine. Dr. Vince: So are you saying this is a contender for an operation other than a total knee? Dr. Berend: I would get a valgus stress x-ray and if it corrected to normal, which means the lateral side stays open
Challenges in Knee Surgery and the medial joint space opens up, I wouldn’t care about overall alignment; I would do a partial knee replacement. Dr. Vince: And indeed that’s what I did. Dr. Berend: There you go. Good boy. Dr. Vince: Maybe they’ll recertify me this year after all. So here we have the change in alignment. Is that acceptable, considering that we’re not supposed to overcorrect unicompartmental arthroplasties? Leo, first of all, do you do any “unis?” Dr. Whiteside: I do, and I certainly would not disagree with considering that patient for a uni. Dr. Vince: OK. Fair enough. Dickey, do you do unicompartmental replacements? Dr. Jones: No, sir. Dr. Vince: OK Dickey, you can take a break. Aaron? Dr. Rosenberg: Yes, I do. Dr. Vince: And how about correction? I would argue that I tried only to correct this to neutral, but if we encounter some “normal” laxity on the medial side, would that be a good guideline for the alignment? Dr. Rosenberg: Yeah, I don’t even correct them to neutral. I think undercorrection is the way to go. Dr. Vince: Keith, what is it in the surgical technique that leads to overcorrection when doing a unicompartmental? Dr. Berend: Damage to the medial collateral ligament (MCL). Dr. Vince: Mark, anything else to add to that? How do people end up with unintended overcorrection in valgus after a medial unicompartmental arthroplasty? Dr. Pagnano: I think it’s fundamentally the thickness of the poly insert that determines the correction. Dr. Vince: I would agree, adding that effect to Keith’s observation. Dr. Pagnano: If you don’t have a way to link your femoral and tibial cuts with your instrumentation, and you make those cuts separately, and you’re fixated on putting in a certain thickness, like in this system putting in a 10-millimeter insert, you may overcorrect a subset of those patients. Dr. Berend: It’s nearly impossible to, quote, “overcorrect” a patient unless you’ve peeled up their MCL. Dr. Rosenberg: It’s hard to put the poly in if the MCL is tight. So it’s hard to put them into “overcorrection.” Dr. Vince: So I think we’ve got the complete answer between Keith and Mark. Keith saying that if something lengthens the MCL, and then as Mark is saying the surgeon tries to stabilize it by putting in thicker poly. But, we agree that unlike total knee arthroplasty, it has nothing to do with the angle of the bone cuts. Let’s move on. And what do you think about this kind of alignment (Fig. 5)? Is this acceptable, Keith? Dr. Berend: Perfect.
Case 3 Dr. Vince: Here’s a wobbly, painful arthritic knee (Fig. 6). Leo, what do you recommend for this patient? Dr. Whiteside: This looks like an unstable knee, with hyperextension and interesting varus.
121 Dr. Vince: Yep. Dr. Whiteside: I would be ready to use all the tricks I know to end up with a stable knee in this.13 Dr. Vince: Right. I shy away from cases of neurologic recurvatum, polio, for example. But I would argue this is structural recurvatum. What do you think, Keith? Dr. Berend: I agree completely. You have massive flexion over the distal femur. Dr. Vince: Yes, an exaggerated anterior femoral bow there. So what do you do differently? Dr. Berend: I would use some type of instrumentation to help me line this leg up a little more accurately than intramedullary alignment. I would use a preoperative magnetic resonance custom knee or standard navigation. Dr. Vince: Dickey, are you going to need something like that? Dr. Jones: I think that’s an interesting concept, but it’s not the practice in our University Medical Center. Dr. Vince: Why is this patient in recurvatum? Dr. Jones: I think the recurvatum is directly related to the large anterior bow at the diaphyseal metaphyseal junction. Dr. Vince: Yes, because functionally this woman doesn’t walk down the street with everyone commenting: “oh, my goodness, you’re in hyperextension!” Aaron, what’s your insight? Dr. Rosenberg: I think that the first thing to do for a patient with radiographic recurvatum or a substantial femoral bow is to identify the origin of problem. So you have to look higher up the femur. Does she have fibrous dysplasia? Is this something that happened because of growth? And she’s lived with it for many years. Is it a post-traumatic deformity? Did she have an injury in childhood? I would agree that this looks structural. But the key message is if somebody is in recurvatum, it’s either a mild degree that they have had since they were young, and commonly associated with valgus in females or if it is acquired in older age and it is progressive, you have to work them up neurologically because those can be disastrous after TKA. Dr. Jones: One of the reasons for recurvatum here is the long posterior capsule. When you reestablish the joint line with standard bone cuts, consider the effect of that posterior capsule. Dr. Vince: Mark—let me put a question to you. Polio is our prototype for recurvatum.14 They have weak quadriceps and have to lock their knee in hyperextension to walk. It strikes me that some people who have painful patellas walk like that. And then, if the body mass index is high, and the load across the patella is greater because of weight, some people will not like to bend their knee very much when they walk due to patellar pain. Do you see that phenomenon? Dr. Pagnano: That specific one, I haven’t noted myself. I think this just highlights another aspect of alignment. We know relatively little about axial alignment in the coronal plane, and we know even less about alignment in the sagittal plane. So what’s going on with this patient’s hip? Dr. Vince: The hip is satisfactory. Here are the radiographs after TKA. Leo, where would you like to see that red mechanical axis line?
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Figure 6 Case (3): Alignment for TKA and sagittal plane stability. (A) Short radiographs showing 14 degrees of varus deformity with opening of the lateral compartment. (B) Hyperextension with “opening” of the posterior soft tissue structures. (C) Patellofemoral view showing a centrally tracking but arthritic patello-femoral joint. (D) Postoperative short radiograph showing 6.5 degrees of anatomic valgus alignment. Medial release has been performed, and medial structures now lengthened and equal to lateral side, but posterior structures still elongated. (E) Postoperative, single-leg weight-bearing, lateral radiograph showing hyperextension similar to preoperative status.
Dr. Whiteside: That looks good. I can’t argue with that. Dr. Vince: OK. Mark, Is that within the threshold? Dr. Pagnano: Looks good. Dr. Vince: OK, and there’s the close-up. If I were smart, I wouldn’t show you anything else. However, I have always done lateral x-rays with the patient standing on one leg. And I’ll just give everybody in the audience a piece of advice, if you want to feel good at the end of the day, don’t do those in your practice as they reveal recurvatum and flexion contractures you never thought were there. Really, just don’t do them. This is what a single leg weight-bearing lateral radiograph shows us. She is quite happy with her knee, but I find the recurvatum distressing, and I fear it may be bound for doom. Dr. Jones: Is that a cruciate retaining or—
Dr. Vince: That’s a posterior stabilizer. Do you think a cruciate retaining would help? Dr. Jones: Well, I worry about the impingement on the post in hyperextension. Dr. Vince: Absolutely. Dr. Jones: You’ve got 6 degrees of tibial slope and probably 15 degrees of hyperextension, and most posterior stabilized knee designs won’t tolerate that. Dr. Vince: Leo, I’ve always looked to you for insights into soft-tissue problems. When I reflect on this knee, it seems that the collaterals were about the same length to each other, but if I think 3-dimensionally, and include the posterior structures, to Dickey’s point about the long posterior capsule, it is longer than the collaterals. What should I have done to avoid this problem?
Challenges in Knee Surgery Dr. Whiteside: In general, if you have laxity of the entire knee in extension, then just distalize the joint by resecting less distal femur. That affects extension only. Laxity in flexion and extension will require a thicker tibial component. But in this case, you’ve got a deformed femur and an excessively long posterior capsule. So I would do what you did. Maybe a little bit more of distalization of the distal femur. You followed the curvature of the femur with the femoral component position. I would however use a cruciate retaining knee. A posterior stabilized knee is in danger of shearing off the tibial post. So I think you make a few compromises, and you end up with a knee that looks good. Dr. Vince: Dickey, you and I make a good pair because I hate hinges, and you really do a good job with them. Was that the answer here? Dr. Jones: I wouldn’t have used a hinge, no. I agree. The answer is to cut less distal femur, try to avoid hyperextension mode. But then, she comes back, and because she’s walked in hyperextension all her life, and she now doesn’t like walking without it. So that’s got to end up being a problem.15 Dr. Vince: One of my fears with a case like this is the narrow knife-edge either side of full extension. If you leave a person like this with a little flexion contracture, the knee buckles. And if you go past full extension and give them a little recurvatum that they like, they increase it over time. For all of you in the audience, please work on the answer to this problem for us by next year, if you don’t mind.
Case 4 Dr. Vince: Our colleagues overseas, who are well represented at this meeting, regularly deal with big deformities, of the sort that we haven’t dealt with in volume in the United States for 20 or 30 years. I was working in India 2 weeks ago, and this would be a “bread and butter” case there (Fig. 7). This patient walks with instability. The lateral x-ray has multiple deformities as well. Keith, what’s your approach to this severe varus deformity? First of all, are you going to do bilateral or staged? Dr. Berend: When we do Operation Walk in Nicaragua and Guatemala, this is a standard deformity. Bilateral surgery should be on the basis of the patient’s comorbidities. The most important one that we saw at the Knee Society Specialty Day this year is heart failure. So, no heart failure, I’d do simultaneous bilateral. And I’d approach these knees right from the start with a giant medial release, and get them . . . try to get them straight. Dr. Vince: Leo, if we do one knee like this in a patient with a flexion contracture on both sides, they’re going to have a much longer leg because of the arthroplasty. Unless we put a huge shoe lift under the unoperated leg, the flexion contracture will come back on the TKA. Dr. Whiteside: That may be true. I tend to not do bilateral knees, but I think that may be a reasonable case for doing bilateral knees, unless it’s a sick patient. If it’s a sick patient, that’s a fairly thin excuse to do bilateral knees. I think if I taught the patient to work on full extension all the time, and
123 then in 3 months when their health returned to a certain extent, I’d go back and do the other knee. I still am very careful about doing bilateral knees because the average age of my patients is about 74 years old and heavy. Dr. Vince: Right. Aaron, Keith described using a “giant medial release.” I’m glad to hear that classical technique isn’t dead and gone. He sounded pretty confident that he would be going home at the end of the day with a success. Can you assure me that a “giant medial release” is all you’re going to need here? Dr. Rosenberg: Well, the question is, to what extent are there other instabilities? If the lateral side is not grossly unstable, you can, in the vast majority of the cases, even with this much deformity, release the entire MCL down along the tibia. In some cases, after you’ve released it with a long elevator, 12 to 14 cm down that medial side, you will have to put a big spacer block in there. During this procedure, my residents are wondering, “what are you doing?” and it (the medial side) goes “pop,” and the whole medial sleeve just pulls off. The patients do well, but you have to work at the correction. In addition, you can cut off some of that medial tibia to loosen the medial soft tissues. You can get these knees out straight. We see about 2 or 3 cases like this a year from people in the neighborhood, we used to see them every day. Generally, you do a standard medial release. Jerry Engh has talked about doing a medial epicondylar osteotomy,16 but I don’t think it’s necessary. Dr. Vince: Mark, is this a patient in whom alignment really does matter? Dr. Pagnano: Oh, I think it does. What you don’t want to risk is an early failure from instability. I think the first thing is to get that knee well balanced, so ligament balancing is the cornerstone. Alignment is secondary, but still important. Dr. Vince: Have you ever had Aaron’s experience where not only do you do Keith’s release, but you put the osteotome down the medial side to strip it like Aaron does, and then discover it’s unstable? Dr. Pagnano: Yeah, I think that happens when you push the leg beyond where it should be corrected. So you feel the “pop” that Aaron described, then the resident goes one step beyond and stretches it out into 10 degrees of valgus for 2 seconds. Now you’ve pulled the MCL all the way up the medial side, and that’s when you need to do something else: either directly repair the MCL back to the tibia or switch to a constrained condylar device. Dr. Vince: I was brought up to believe that constrained implants were the “last resort of the incompetent.” And thanks Leo; you’ve done nothing in the last 20 years to help me escape that idea! But, as you see from the postoperative x-rays, I felt the need of an insurance policy for this lady. The lateral, not the medial, side was unstable after the medial releases and I couldn’t accept it. She has quite a wide thigh girth, and as much as I dislike constraint in a primary arthroplasty, I believe now that with good bone cuts and fully cemented short stems, they will be durable. I don’t like constrained implants with uncemented stems in primary arthroplasties, unlike revisions where I think diaphyseal
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Figure 7 Case (4): Severe varus deformity and the role of constraint. Preoperative radiographs. (A) Right lateral. (B) Right anteroposterior with 26 degrees of anatomic varus, attenuation of lateral structures and subluxation. (C) Anteroposterior view of left knee with 28 degrees of anatomic varus and similar ligamentous laxity. (D) Lateral radiograph of left knee with exaggerated posterior tibial slope-will you reproduce this slope at TKA? (E) Postoperative anteroposterior radiograph of right TKA with nonlinked constrained implants and fully cemented “stubby” stem extensions. (F) Postoperative radiograph of left TKA with constrained implant and auto graft reconstruction of medial femoral condyle using distal femur and a “Sculco” technique. (G) Bilateral full-length radiographs showing mechanical axes still passing through the medial compartments. Is this enough valgus alignment?
uncemented stems are highly advantageous. Is there any alternative to this? Dickey? Dr. Jones: I know my friends in India have shown me lots of femurs that require 9 degrees of valgus in the distal cut to compensate for a large femoral bow. Dr. Vince: There’s a big femoral bow in this case.
Dr. Jones: So, for these huge deformities, you sometimes are going to need revision implants ready, even though it’s a primary, because of the severity of the deformity. This is one such. Dr. Rosenberg: You have to remember that metabolic bone disease and nutritional deficiencies may be more prev-
Challenges in Knee Surgery alent in some countries and lead to significant deformities of the femur. Dr. Vince: Consider the mechanical axis. I’m not terribly happy to have that weight-bearing axis a little on the medial side, because I think this woman has dynamic features that exacerbate varus in her gait. And I think, Mark, this is what you’ve been saying; that for this particular patient, alignment is tremendously important. Dr. Rosenberg: I think it’s important, but I would say probably this woman isn’t going to go out and try to play basketball. She’s too short! This is the type of patient who had horrible knees and who is grateful to get up and walk to the kitchen or the grocery store. And I wouldn’t worry about the long-term survival based on the alignment in her. Dr. Whiteside: This is the size of thigh that if you put the knees in 5 degrees of valgus, the feet are going to be a footand-a-half apart. Slight varus is acceptable. Dr. Vince: Very important point. If I give this lady more valgus, her stance is going to be so wide that she immediately goes from a dynamic varus force to a dynamic valgus force, and instability in the obese patient has been a serious problem.17,18 Dr. Jones: Many really large patients walk by circumducting the limb. And so you nearly always see a valgus deformity because of the valgus moment at heel strike. Dr. Vince: Gait problems may be compounded by relative hip abductor weakness with respect to body weight that requires shifting the center of gravity over the knee during stance phase with a large valgus moment on the knee.17 Keith, I had a defect on the medial tibia and I used the technique that Tom Sculco19 described so nicely, cutting the defect into a flat slope, then putting the distal femoral condylar bone cut on there, opposing cancellous to cancellous bone. Is this one where you would use something else? Dr. Berend: It’s probably not big enough to consider doing anything else. This is a great technique except that the bone is not really loaded, so I don’t know if it will stay there long term. I would use the screws and cement technique that Merrill Ritter has written up, with outstanding survivorship, prepare the sclerotic bone, put in a couple screws to function as “rebar,” then cement the component. The other thing you’ll notice is where those screws are hanging over, if you remove that medial flange from the tibia and downsize the tibial component, you can use less of a release on the medial side.20 Dr. Vince: In a short stature patient like this, you can rapidly get into trouble with the need for small sized constrained components. The other technique I used in this case was to automatically resect an additional 5 mm of distal femoral bone, not to correct the flexion contracture but to harvest a bigger chunk of distal femur for the medial tibial defect, with the intention of putting a distal augment on the femur. That worked well.
Case 5 This case gave me some serious grief. This is a delightful gentleman patient from Tonga. Single-leg weight-bearing xrays show that the deformity is greater than anticipated. This
125 is a similar flavor to the last case but in a very large man. This is the early postoperative film (Fig. 8). He required the largest femoral size in the kit, and that size does not come in a constrained option. I was fairly happy with what we had immediately postoperatively, but not some of the later films that you see there, which are distressing. And about 6 weeks later, his 400-plus pounds really did something to my reconstruction. When we see him walking, there’s a dynamic, varus force or “lateral thrust” on his knee. At revision surgery, he had snapped his lateral collateral ligament. So Leo, what should I have done here? Dr. Whiteside: I think you pointed out that this is a knee that was unstable laterally to begin with. And the common issue is to fail to do enough medial release and then fail to achieve tight enough lateral structures. It is also a problem to leave the tibial bone cut in too much varus. All that together will give you a knee that’s unstable on the lateral side. So I don’t think there is any stabilized knee in the world that will withstand the kind of loads that one is going to see. So with this type of varus knee, I would be very careful to make a perpendicular tibial cut. Then, because of the length of his thigh, I would cut the femur at a 3-degree valgus angle rather than my usual 5. I would do enough release medially to be sure that I had tight lateral structures and full extension. Dr. Vince: I think your point is very, very important in terms of there being no constrained device that’s going to resist these loads. Dickey, would you agree? Dr. Jones: Absolutely. Yes. Dr. Vince: OK. We have to decrease the destructive load on this knee and I would say I failed to do that. I should have given this man more valgus alignment. Dr. Whiteside: Or just continue to release medially and achieve tension laterally. Dr. Rosenberg: Is this x-ray (Figure 8I) what the knee looked like when he was laying down, and then he got up to walk and he began to open up on the lateral side? Dr. Vince: Initially it looked like this lying and standing, but he started to open progressively. By the time I went back to revise it, the lateral collateral ligament had snapped. But I think I left this primary TKA with too much varus deforming force. Dr. Rosenberg: Yeah. Dr. Vince: And then, to compound things, I broke one of my own revision rules. I try to get everybody else to do complete revisions, and I didn’t revise this tibia because it was well fixed and it had a stem extension.21-23 I used this nonlinked constrained femoral component and supplemented it with an Achilles tendon allograft to reconstruct the lateral side. To date, he’s still stable, but I’m worried by his size and the forces involved. Dr. Vince: To our audience, I thank you for your patience. Gentlemen on the panel, I appreciate your input and I think everyone in the room thanks you for sharing your experience and thoughts.
Moderator’s Comments Alignment, an elemental precept in knee arthroplasty, is presumably something on which everyone agrees. New discus-
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Figure 8 Case (5): Very severe varus deformity, with “dynamic” instability and flexion contracture. (A) and (B) Preoperative varus deformities with 17.3 degrees of anatomic varus on the right in a patient with a significant lateral thrust on ambulation. Appears magnified because of fixed flexion contracture. (C) and (D) AP and lateral radiographs of right TKA, difficult to interpret because of rotated limb on radiograph, but appears to have inadequate correction of varus deformity. (E) and (F) Correctly rotated AP and lateral radiographs of left knee, showing the intended 6.8 degrees of valgus anatomic alignment. (G) Full-length postoperative radiographs showing unsatisfactory alignment and stability on right TKA with opening of lateral structures and mechanical axis medial to the medial compartment. Left TKA has satisfactory alignment and stability. (H) Postoperative anatomic axis of right TKA, not single leg weight bearing, showing asymmetry of extension gap and lateral instability. (I) Postoperative AP radiograph of left TKA with satisfactory alignment and stability. (J) By 4 months, the overload to the lateral structures resulted in rupture of the lateral collateral ligament and instability. (K) AP radiograph after revision of femoral component with constrained implant and Achilles allograft reconstruction of the lateral structures. Press fit diaphyseal stem was placed after preferential lateral endosteal reaming to increase valgus position. Offset stem used to centralize femoral component. Tibial component, installed in slight varus alignment could have been revised to advantage, to decrease varus loading, but was not.
sions have arisen on this old topic, some prompted by surgical navigation. Intramedullary instrumentation works from “anatomic alignment” (the axes of the tibia and femur) and navigation from the mechanical axis. The goal of arthroplasty technique may be: (1) undercorrection, believing that “natural” ligament balance is pre-eminent; (2) neutral mechanical axis (which doesn’t equate with equal load on medial and lateral compartments); and (3) overcorrection (that aims to reduce the destructive forces resulting from varus or valgus pathology).
Case 1 was intended as an “ideal” indication for HTO, with the exception of female gender. If an athletically active 37year-old patient with single compartment disease is not a candidate for osteotomy, then few other patients can be. Few data exist to support the idea of uni-compartmental arthroplasty (UKA) in this age group. The ideal alignment after osteotomy, balancing pain relief against cosmesis was a central discussion point. Case 2 is neither rare nor easy to define as simply varus or valgus. I would characterize it as “varus” because of the me-
Challenges in Knee Surgery dial compartment loading pattern and resultant disease. It highlights above average varus tibial slope and the implications for the relationship of the posterior femoral condylar angle and the trans-epicondylar axis. This case was selected as an ideal candidate for UKA and the topic for discussion included ideal alignment for UKA, which is different from that for HTO and TKA. Case 3 demonstrates challenges with recurvatum that is structural (and not neurologic in origin) plus extra-articular deformity in the plane of motion of the joint. These cases are at high risk for failure from progressive recurvatum and preventive action during the primary surgery was the question for the panel. Case 4 was a knee with severe varus deformity, exploring the ideal alignment and soft tissue balancing that are required, plus the role of constraint. Alignment, it may be argued moderates the load on medial and lateral compartments while the collateral ligaments provide stability. The better the alignment is “balanced” the less severe the loads that will be on the collateral ligaments. As surgeons we frequently like to depict the medial ligament in a varus deformity as “abnormal” and that our releases will make it “normal” and equal to the lateral side. In truth, the greater pathology in this knee is the convex, lateral side. If lateral integrity has fallen victim to the extreme deformity, constraint is necessary. Some surgeons believed that leaving residual varus deformity is somehow more “normal” for this patient, and sustains functional tension in the lateral collateral ligament. I am not one of those surgeons. Case 5 expounds on the points from Case 4 — here, the size of the patient made constraint a dubious option, and inadvertent residual varus deformity resulted in early instability of the primary arthroplasty when the overloaded lateral collateral ligament failed. I feel this case argues strongly against the concept of undercorrection. The concept of achieving success by maintaining tension in the collateral ligaments failed in this case.
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