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Guido LaPorta, DPM, MS
Director Podiatric Medical Education
Community Medical Center
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Harold Schoenhaus: Our next speaker really does not need an introduction, but I felt obligated to do so. Dr. LaPorta has been a dear friend of mine for many years. Extremely knowledgeable. Great speaker. Looks at problems in depth and is able to share and explain these things to you. He is a director chief of foot ankle surgery in two hospitals, one in Scranton and one in Binghamton, New York. He is going to talk to us a little bit today about total ankle joint replacement in considerations of angular deformities if they exist at the same time. Please welcome, Dr. Guido LaPorta.
Guido LaPorta: Thanks Harold. Good morning everyone. I will make some comments about total ankle replacement this morning. About five years ago, this was an esoteric presentation. As of this time, ankle join replacement in some form is here to stay. I think it's a good idea whether you perform it or not, to know exactly what in fact is available that can help your patients. Let's look at total ankle replacement. There's a treatment hierarchy for ankle pathology and we heard a lot of it from the last presentation. But if you go down the list, you can go anything from so-called conservative care to viscosupplementation, arthroscopy, distraction techniques, things of that nature. The question in endstage arthrosis is always, which is the primary procedure that we should be doing? Well, for years, it was arthrodesis of the ankle. Then more recently, total ankle replacement comes in. Right now, the argument, if there is one should TAR or replacement actually supplant arthrodesis as the primary approach to these joints? We obviously don't have the answer and if you look at the literature, you see a number of approaches to replacing the endstage arthritic ankle. Some years ago, the size match allogeneic joint transplants were touted as possibly the answer and I should point out to you that there is a resurgence in this area. It is being referred to as biologic ankle replacement where allogeneic material size matched via CT scan is being used to replace the damaged ankles. We don't know where this is going yet. It is in fact an attractive option that can be used. Because if and when you can get this to incorporate, you obviously have less of a danger of the skeleton wearing out. Additionally, there is the use of ceramic and now cobalt chrome and titanium talar body prosthesis in patients who have aseptic necrosis. This is who and whom it was used immediately. All of these companies now and there's a number them which can 3D print a talus for you. That's an attractive way to look at this because they can also machine the surfaces so that some are smooth like articular cartilage and other's are dimpled so that you can actually get soft tissue and ligamentous in growth into the metal stabilizing this particular paresthesias. There are a number of different centers using this now and we'll have to see where this goes. Let's look at the first generation TARs because there were a number of problems with this. Dr. Schoenhaus and I were done in by these designs many years ago and if it stopped there, we never would have looked at total ankle replacement ever again. But to all these designs used cement and a lot of the poorer outcomes were due to the fact that cement was used.
This cement mantle meant that more bone had to be removed that there were higher moments of inertia from the joint center causing loosening and they led to a lot of failure. The design was also constraint which meant it worked like a hinge. Now, you and I know the ankle does not work like a hinge, even though there is predominantly sagittal point of motion. There is also a frontal plane motion and there is a degree of rotation. The argument is how much? The Salto-Talaris people tell you, you only need four degrees of rotation for the ankle implant to be successful. The Stryker people will tell you, well maybe that's not enough because the normal ankle from plantarflexion to dorsiflexion has as much as 13 degrees of rotation. The Salto people will counter and say, you never use your ankle from full plantarflexion to full dorsiflexion. The Stryker people say, well, if you have steps you do because you need 50 degrees of plantarflexion to walk down steps and you need almost 30 degrees of dorsiflexion to walk up steps. It's an interesting argument and the truth is, nobody has the answer. The instrumentation for the first generation implants was terrible. It was almost an art form like it was in Europe for many years and all of that has been changed. Of course, there were no revision strategies. My personal experience with the initial ones that came on, I remember the St. Elmo Newton ankle out of Seattle, I put four of those in and took four of those out in very short order because they were just doomed to failure. If you look at these first generations cemented types, that gave way to the two-piece class II devices of which there are a number, the grand daddy of those was the agility which no longer is in fact available as is the TNK that no longer is available. The SK is not approved in this country, but the in-bone is and the Salto-Talaris is, and the Zimmer trabecular metal is, and these are very good devices. They have a track record with people who used them. Used them in very narrow indications and they were quite well for them. The three-piece class III are mobile-bearing devices. These were introduced interestingly enough at the same time that mobile-bearing needs were. If you look at all of the devices in Europe where total ankle replacement is a common reconstructive procedure, they are all mobile-bearing devices. The problem with getting a mobile-bearing device in this country is that in around the late 70s, the FDA changed its requirements for ankle replacements. All the ones that existed were grandfathered in and from that time, if you could show the fact that you had properties similar to those that were grandfathered in, then you could get a 5, 10k for your implant. At that time, there were no mobile-bearing implants. Consequently anyone who wanted to get a mobile-bearing implant approved had to go through a very rigorous clinical trial. How rigorous? The STAR implant which is now marketed by Stryker had to go through a ten-year $50 million study in order to get approved by the FDA. That pretty much takes care of anybody else who wants to get a mobile-bearing device approved in this country because the market for these is not as great as it is for knees. If you're going to invest $50 million to $60 million to $70 million in a multiyear study, you're not going to make that money back in any way based on the numbers of these devices that they're doing.
When the Beuchel-Pappas, which was also mobile-bearing device lost its FDA approval. Then, we haven’t seen any others even inch towards approval in this particular country. What are the indications for TAR? They’re kind of obvious. Primary or secondary osteoarthritis but in this country, posttraumatic osteoarthritis is the most common indication, and it can be after ankle fracture pilon, talus fracture provided you don’t have AVN with collapse and AVN has to be 25% or less of the talar body for TAR to be indicated. Of course, there must be commonsensical good bones stat, good circulation, good alignment, muscle strength to power the arthroplasty and I think most importantly, the patient must understand that they have to place low physical demands postoperatively on the implant. You’re not going to replace an ankle in a runner and expect them to go running. You might do it in a golfer. You certainly might do it in a swimmer but you’re not going to do it in a somebody who’s going to put demands on that ankle over and above low physical demands. There were a number of patients who had failed ankle replacement and had to be converted to arthrodesis and treatment algorithms began to be developed for those particular patients. For current indications say that the patient needs to be 55 years old or greater. Then, you noticed that most clinicians are doing these in younger patients. Fifty five is the magic number because that was the number was used in this study for the STAR implant. It’s not that you can’t use in a younger patient. It’s this that is has not been tested in a younger patient for longevity and consequently when you are doing that you are doing it off label and you should recognize that. I personally have total ankle replacements in 30-year-olds and 40-year-olds and they all undergo this with the provider that they know that the survivor ship of this implant probably at best is going to be 10 years and that we have to look at it every year, replace it as soon as it becomes necessary so that we don’t have to convert it to a fusion at a young age. Same thing is true of weight. Two hundred and fifty pounds seems to be the limit. Why? That was the limit in the study. But I could tell you that I have certain implants in patient who weighs 300 pounds which tends to be an average weight in my part of the country. I don’t get very many patients who are in perfect shape, even my [indecipherable] [13:27] are overweight. Therefore, 255 is an off label use but you have to alert the patient to that effect. You have to carefully examine the soft tissues and what I mean by this is that when you’re doing this in a posttraumatic patient you have to look at the stiffness and the lack of motion that that patient has. Because you may not be able to regain motion in patients who’s soft tissue is adhered to the neighboring osteo structures. You certainly can relieve pain but if range of motion is one of your patient’s main concerns, be wary of that. Malalignment, malunion, extremely important. The replaced ankle is no different than the native ankle. And by that, I mean, that in the sagittal plane you can have 10, 15, 20 degrees of deformity that you make up with an ankle implant. But in the frontal plane when you’re looking at that patient from the front or back the maximum amount of allowable frontal plane deformity is about five degrees, and the reason for that is that there is very little in the way of compensation for that five-degree deformity.
You would need a normally functioning subtalar joint for that deformity to be compensated. One of the complications of ankle implant is that a lot of the stress that’s been applied to the ankle now will go to the subtalar joint and you can wear a subtalar joint out prematurely requiring fusion if you don’t realign the extremity. It has been said that you can make up for about 15 degrees of frontal plane varus or valgus in the actual cuts. I think that’s pushing it and usually I will say five to eight degrees or I’ll put up with and compensate with my cut and if there is any more than that I will do some form of corrective osteotomy. When do I do that osteotomy? I do it prior to doing the implant. I stage the procedure. I do not osteotomize the tibia, put an implant and fuse the subtalar joint, do a first ray osteotomy altogether. I think that’s total absurdity. One of the things we found out is that when we realign the tibia we sometimes don’t need the implant because realignment of the stress in the extremity actually improves ankle symptoms. We do any realignment osteotomy first. Wait six to eight months, and then see how that patient is doing with their symptoms. If you have knee arthritis that must be fixed first before you do the ankle. Lower tibia, supramalleolar greater than 10 degrees should be fixed first. If you have mismatched columns, if you have a short fibula you need to re-lengthen the fibula. That actually can be done the same time as the implant, and in the foot I will do a calcaneal osteotomy or first ray osteotomy at the same time as a total ankle replacement because those seem to work well and do not add a lot to the recovering patient. Hindfoot ankle or instability, you have to look at the soft tissue. I’m basically a STAR fan, I should tell you that I like the mobile-bearing implant. All you have to at least in my mind is once the implant is in place, put the ankle joint to a range of motion and you watch the mobile-bearing bounce all over the place. But when you have a fixed bearing implant you can’t do that. Something has to absorb all of that road or force that goes on within the ankle, and if my opinion it’s the mobile-bearing. Now, what that means to you is that a mobile-bearing implant depends more on the surrounding ligament structures for stability than a fixed bearing implant. You can’t have ligamentous laxity either medial or lateral, and if you do you need to in fact sure those ligaments up so that they provide stability. One of the tricks that I like to use is that after the implants in place and the trial spacer is in, I forcibly invert and evert the ankle and shoot any space open up between the mobile-bearing and the tibial component, then I know I have some ligamentous loosening. I will go up a size in the poly, and if that doesn’t in fact reduce the instability, then I know I have to do ligament stability procedures. I try not to use a poly thicker than 8 millimeters, and the reason for the is that once you get up around 9 and 10 millimeter polys you actually displace the center of rotation of the ankle distal which causes everything to work a little bit different, and I would rather not do that. Seven or 8 millimeter polys seem to be the sizes that were most duplicate normal motion. Ankle contracture also very important. What are the contraindications? Well, these are also obvious. Neuropathic disease seems to be a contraindication but I must tell you that people at Duke are now placing these implants in diabetic patients, we’ll see how that works out.
I have not done that. That’s not eye on my list to do. I would rather fuse those patients whether they have an active or a recent infection is a contraindication. Avascular necrosis greater than 50% of the talar body, severe benign joint hypermobility which means these patients are hyperlax and all of their joints, you have to be careful about that. Nonreconstructible malalignment and high physical demand people are contraindications. Relative contraindications, previous severe trauma, AVN 25 to 55% of the talar body, severe osteopenia or osteoporosis. Remember, most of these implants with the exception of the in-bone and its long modular stem depend on the cortical rim of the tibia and talus for support. The in-bone by allowing you to increase the length of their modular stem can bypass that cortical rim and go up into the medullary canal much like an IM nail would and that can be much more stable than an osteopenic patient. The design goals we’ve touched on, there are two different design philosophies that are important, constraint and conformity. One of the things, the way to describe this is that in the first generation of ankles that came out and I’ll use the agility as an example. I’m not picking on it. I’m just using it. The first one of those I ever did, I ran across the other of the hospital because I knew one of the total joint surgeons was working, and I showed him the postop C-arm picture and I said, “What do you think?” And he said, “That’s very interesting.” And I said, “What’s that?” He said, “How come this total ankle doesn’t look like an ankle?” Good point, it didn’t look like an ankle. It depended on other items for stability. The shape of it was not the same shape as in human ankle. Why is that important? Well, the human ankle is the most congruous stabled joint in the entire body. The new designs mimic that design, and therefore, the very design of the components provide stability to the ankle joint. There are many difficulties when working in an ankle. It’s a smaller joint, therefore, it has higher result in moment of force, higher compressive forces, malalignment and instability is far more important in this replacement. You have to deal with soft tissue contractors. There’s a number of different ways to look at that, what soft tissue contracture is the most common? A tight heel cord is, and consequently, you have half the surgeons doing this say they never need a heel cord lengthening, the other half saying they always need a heel cord lengthening. What’s the right answer? Well, I don’t really know. I tend to do more heel cord lengthening than not, and when I do it, it depends on couple of things, you can talk – for instance in my hands I’d rather do the heel cord lengthening at the end of the procedure. But if you to Dr. Schoenhaus he’ll say that maybe if you do it upfront you have an easier time putting the implant down, and I certainly seen that happen. There is really no right answer to that, right, as of yet except for me to say that I tend to do more heel cord lengthening than not. Classify tendo Achilles lengthening in a number of different ways and you can do it by fixation, how many component it has, how constraint it is, what the shapes are, what kind of bearing it has, fixed or mobile-bearing. It’s in fact, you look at this chart you can see all the things. The agility is no longer available. Forget about that one. The eclipse is no longer available. You can replace that with Zimmer trabecular metal device.
But what are the differences? Well, the differences are that the STAR implant is the only total ankle replacement that is one mobile-bearing and two FDA approved to be used without cement. That’s important. That means when you use a Zimmer, a Salto-Talaris or an in-bone without cement you were using it off label. I bring that up because of two things, one, I don’t think many of the surgeon should do that, alert the patient to the fact that they are using if off label. And I remember seeing a commercial once in the great state of Florida when I was down for a meeting that said, “Have you had a total ankle replacement recently. We’d love to review your records.” Because the attorneys caught onto the fact that these were being done without cement, that it was off label, and that patients weren’t exactly being informed of that. Should something go wrong they wanted to be ready to pounds on that particular problem. I think you have to be careful. Those of that little white label that’s inside every component box, you should take the time to read it if you’re doing these, at least once since they’re throwing it in the waste basket because a lot of the material in there is extremely important. Most of the newer ones have bone growth properties and that’s important because you can resect less bone, you can use a smaller prosthesis. You can avoid the inadvertent cement displacement into the joint and it will eliminate damage to the delicate soft tissue. Preoperative planning is very important. We’ve talked about most of this. We do a lot of x-ray alignment studies in order to make sure that we have an optimum situation. We look at hindfoot alignment studies and we want to make sure that our calcaneus is appropriately positioned underneath the tibia. I do studies from the hip to the ankle, orthogonal weightbearing hip to ankle. I used to be able to do these in my office, I no longer do that. I send them to the hospital for this and I want to look at the mechanical axis of the lower extremity. I want to make sure that when I drop a line from the center of the femoral head to the center of the ankle that it goes within a centimeter of the center of the knee. If I’m way off from that I’m going to have mechanical issues with this implant no matter how well I implant it. Surgical approach can be somewhat problematic. The anterior approach which all but the Zimmer utilizes has its own problems. There are a lot of structures there you need to be careful with. Typically, your skin incision is midline and once you get below the superficial fascia the safe corridor into the ankle is between the tibialis anterior and the extensor of hallucis longus. Fortunately, with all of these you don’t need exposure of the fibula like you did with the agility and the anterior approach seems to be adequate. What I’d like to do with the interior approach is make it longer than most people suggests. I don’t use self-retaining retractors on the anterior skin. I don’t have my residence retracting skin when we’re not doing anything so that we get the pressure off the skin edges and preserve that. Probably, one of the leading complications with total ankle replacement short-term are skin complications, so you need to treat your approach extremely gently. Here’s the Salto-Talaris. I liken it to the submarine on hunt for Red October with that little [indecipherable] [29:54] up top there. One of the interesting things about Salto-Talaris is that you have to violate the anterior cortex of the tibia in order to put the tibial component in.
That could be a potential problem although in all fairness I should tell you that the surgeon who do Salto-Talaris love this device and that does not seem to be a problem for them. Here, see it in place. The four degrees of rotation is built into the talar component. If you put this through a range of motion you will see the rotation occur within the talar component as it rotates around the fixed poly attached to the tibia. Seventy percent of the stress born by the implant is on the anterior cortex of the tibia. It’s hard for me to believe that’s not a potential problem but apparently that has not been the case. The in-bone device has a positioning device. This was one of the ones I started on. After the agility, I like the exactness of this. It has a sited guide which by the way is intraosseous. One of the advantages I think of the in-bone is that it is an intraosseous sighting device like most knees and hips are. You have to drill thought the subtalar join. That did not appear in fact to be a problem but once you have the sighting device properly located then the rest of the procedure goes very smoothly. The cutting devices in jigs are all based of that original sighting device but if you look at the slide on your right you see what I considered to be the major problem with the in-bone, and that is the amount of bone that needs to be resected in order to fit this device in place. At this particular point in time, I do not use the in-bone as primary ankle replacement. I will use it as a revision device but I think once you use it as a primary replacement, when it goes bad then you have a huge segmental defect that you need to deal with. Here, you see the rimming and then the eventual fitting of the device. There are also these bones in-growth pylons that you can place under the talar component for support which work nice in osteoporotic bone. There it is in placed, very nice device. You can see the stem. That stem is modular. You can make it as long as you want. Every time you add one of those little figurines to it you’re adding $1700 to the cost of the implant which starts at around 14,400. Your $20,000 implant is not out of the question. The STAR implant as I’ve mentioned was the only mobile-bearing implant. It has the longest and most fulfilling literature review of any of the implants. You can go back 20, 25 years and find literature on the STAR implant in Europe. When it first started it was not a mobile-bearing implant. But as it’s gone through six iterations of the original design based on survivorship. Kofoed every time he looked at survivorship added something to make it an improved device and the current design is that. There is no need to go through all of the components of it but I will show it to you in place. It is a congruous device. It resects the least amount of bone in order to place it, which in my mind will make revision or salvage that much easier. The additional surgeries that you can do with ankle implants involve as we mentioned, lateral ligament reconstruction which may include peroneal tendon repair or transfer for first met osteotomy, calcaneal osteotomy, medial ligament reconstruction, hindfoot fusions and heel cord lengthening.
It’s a complete picture and you have to evaluate everything in there. There are many designs. I will not go into them today, but I do want to go into if I can find it. Sorry for this. Yes. Whenever you do a total ankle replacement, you must realize as the surgeon and your patient much realize that amputation is a possibility when these fail. Consequently, that is part of the informed consent. Your first job when they fail is to determine whether or not you have an aseptic or a septic loosening. If in fact it is aseptic and you have good bones stock you can probably do an exchange implant. If you have an infection or bad bone stock you may have to consider fusion. If the fusion doesn’t take you get one good shot at it maybe two, after that, that patient is an amputation candidate. Consequently, I warn you of that because it’s a very real possibility. As you go through with your arthritis patients what their options are, for endstage arthrosis, there are really only two, one is replacement, one is fusion. Fusion has long-term consequences, those consequences being that in the most recent studies it was shown that 20 years post ankle fusion 100% of those patients had hindfoot arthritis, half of whom needed operated on, okay? If your patient is 70, fusion may actually be a good option especially if they’re high demand patients. If they are 30 fusion may not be a good option because you know by age 50 they are going to have hindfoot arthritis. Then what do you at age 50, do you take down your fusion of the ankle and put an ankle implant in and then fuse your hindfoot? That’s an incredibly involved procedure. It’s not an easy problem and I don’t mean to suggest that anyone has all the answers but this is an ever-evolving science and as in fact we go on the implants improve, the instrumentation improves and hopefully the results will improve. Thank you for your attention.