Guido LaPorta, DPM, FACFAS, MS provides an in-depth look into total ankle replacements. Dr LaPorta gives a detailed overview of ankle biomechanics and how ankle injury occurs. He also reviews current ankle implants currently available on the market and advantages of each.
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Guido LaPorta, DPM, MS
Director Podiatric Medical Education
Community Medical Center
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Guido LaPorta has nothing to disclose.
Male Speaker: Our next speaker is known to all of us for many years. I've known Guido probably for 42, 43 years. He's the chief of foot and ankle surgery and director of podiatric medical education of the Community Medical Center in Scranton, Pennsylvania. He's the director of podiatric medical education of Our Lady of Lourdes Memorial Hospital in Binghamton, New York. Guido has been a dear friend, a colleague, an educator and shares experiences and the thought process that’s very unique in our profession. I've asked him to give two talks, one is going to be on the state of the art of ankle joint replacement and the other is on Lisfranc’s injuries. So please welcome Dr. Guido LaPorta.
Guido LaPorta: Thank you Harold. I appreciate those comments. I'm going to talk to you about total ankle arthroplasty. This is a topic near and dear to my heart. I began this in the early 1980s and I can tell you that with the first generation ankle replacements that came out, I did four in the ‘80s and I removed four before the year was up, and had to fuse those ankles. So in a way, it’d helped hone my fusion skills but the implants that we originally had were of a nature that were not conducive to success. When we’re talking about this, we’re actually talking about ankle arthritis, aren’t we? A lot of things that we have to know about why certain ankle implants work and why others didn’t have to do with anatomy and biomechanics. I’d like to go over some of that with you because I think it’s very important. I have a bias and I have to tell you that right from the beginning. My bias is that for all too long, our profession has been technique oriented and not biology oriented. I think you heard it in Dr. Kalish’s talk, you're certainly going to hear it in mine. I don’t care what you use, what implant you use, what plate you use, whose screws you use. It doesn’t matter. What matters is understanding why they work and when you should use them. It’s the biology that’s important and that’s what I think we’re going to stress as we talk about. What are the anatomic and biomechanical characteristics of the ankle joint? Well first of all, we should appreciate the fact that the ankle doesn’t work in a vacuum. In fact, the ankle and the subtalar joint are really modified Cardan joint which means that whatever happens in one joint, the other joint compensates for. In fact, the ankle-subtalar joint complex is a torque converter, if you will and its job is to convert rotational moments that come from the leg and convert that so that the foot becomes plantigrade and is allowed to participate in bipedal motion. So those joints working together dissipate compression, shear and rotational forces. One could say then what happens when you fuse the ankle? Well, obviously you're taking a major component away and the articles which have been done on long-term followup of ankle fusions certainly point that out. What about anatomic considerations of the ankle? Number one, it is the most congruent joint in the body, and consequently, it has very little tolerance for imperfection. So that when you get arthritis, even if it’s a focal arthritis in a small portion of the joint, and the remainder of the articular surface is healthy, you begin to get symptoms. Because of that, you get a degeneration of that joint in short order. The ankle is under its most stress in the middle of stance phase. If 50% of stance phase, the ankle has its most stress. Because of that, when it’s going from a plantarflexion to a dorsiflexion position, the contact area increases. So the greater the contact area, the less the stress per area within that joint and that's also important to realize.
The distal end of the tibia is not at a right angle to the shaft of the tibia. I always thought it was. But it’s angled in valgus so that if you look at an AP of the ankle and you bisect the tibia and measure the joint angle of the ankle as you see in the lower right hand side, you will note that there is as much as a three or four degree inclination of that joint into valgus. The older the patient gets, the more that valgus increases. Consequently, the more the valgus increases, the greater the stress on the subtalar joint. If you measure the lateral side of the ankle which we do because it’s the smaller angle, that can range anywhere from 86 to 89 degrees. If you look at the talus, the talus is a truncated cone. It is smaller on the medial side, larger on the lateral. That’s important to realize. In the human ankle, the lateral side undergoes all the rotation. The medial side is really the pivot point. It is exactly opposite the knee. In the knee, the medial side undergoes the rotation, the lateral side is the pivot point. The talar body is wedge shaped. It’s been described as the frustum of the cone and the reason it’s shaped like that is that no matter where the talus is in the range of motion, it is congruent throughout the entire range. So all that description about when the foot is plantarflexed, the talus has room to wobble inside the ankle is false. It is not true at all. The ankle joint is totally congruent throughout its range of motion. All you have to do to prove that to yourself is look at the ligaments. The ligaments on the lateral side of the ankle are three distinct structures. The ligaments on the medial side is one glob of ligament. That’s why the medial side is the pivot point, the lateral side is what goes through the range of motion. Now one of the reasons you get ankle sprains primarily in a plantarflexed position is that there's really only one ligament that counteracts that and it’s the weakest of the three lateral ligaments. It’s the anterior talofibular ligament. When the joint goes into plantarflexion, that ligament rotates to a point where it’s the only ligament that prevents a sprain. We say, why does the calcaneofibular ligament tear? It takes rotation to tear the CF ligament. That is not an inversion mechanism. So when you look at the lateral side, you see three distinct anatomic ligaments. You don’t even see the posterior one. So all those nice drawings that you see in the text that show the spokes of the wheel are inaccurate. The posterior talofibular ligament actually is behind the fibula. It goes straight from the fibula into the talus and that’s one of the reasons that it’s A, the strongest and B, the less frequent injured. Now, when you look at the medial collateral ligaments, even though you have a superficial and deep portion, these are one large anatomic mass of ligaments and you can see it here, it does send extensions to various tarsal bones. But this is the pivot point of the ankle. Consequently, it leads to a complication in total ankle replacement. One of the most frequent complications in total ankle replacement is fracture in the medial malleolus. The reason for that is that if you're trying to duplicate near normal motion in the human ankle, but in the process of putting in the ankle, you weaken the medial malleolus because of your bone cuts, the force generated by motion within the ankle is going to cause the deltoid to avulse the medial malleolus right off. So you need to know that you need to be careful about that.
What always fascinated me was the ankle joint range of motion. When I was a student, I thought it operated like a hinge, foot went down, foot went up. In effect that happens, but it happens with motion in all three body planes. So that if you look at the axis of motion of the ankle, you can see that it basically on the frontal plane passes at the tips of the malleoli. This is important because plantarflexion of the ankle is accompanied by adduction and dorsiflexion of the ankle is accompanied by abduction. When previous designs were very constrained and just allowed a sagittal plane motion, that didn’t duplicate the motion of the ankle. It caused stress risers and it caused loosening of that particular joint. Now what is this? This is an interesting looking drawing. Interestingly, this is the intersection of the many ankle and subtalar joint axes. It happens to occur in a place just above the posterior facet of the subtalar joint. The point of this is that when you are correcting deformity, this is the pivot point. You can correct deformity around the ankle and the subtalar joint by using this as your pivot point. You can do frontal plane, and you can do sagittal plane correction with this as your pivot point. The overall range of motion, you see all kinds of degrees in different texts. Remember that you need about 10 to 15 degrees of plantarflexion and 10 degrees of dorsiflexion for normal walking. Basically that’s all you're going to get from a total ankle replacement. Anybody who gets a total ankle replacement is automatically excluded from any activities that are high impact, involve uneven ground and if they're not aware of that, then you may have a dissatisfied patient. You should also tell that patient that it takes much more range of motion to walk downstairs than it does upstairs. It’s not infrequent that your patients forget total ankle replacement, but with any ankle surgery, the last thing they can do comfortably is walk downstairs. They can walk upstairs much more quickly than they can downstairs. They frequently tell you they have to go down one stair at a time and that’s because you need far more range of motion in order to accomplish that. When you compare the ankle and subtalar joint, you see that they work in unison with each other. The structure of the ligaments within the tarsal canal allow that sagittal and frontal plane motion by winding and unwinding in order to accomplish all of that motion. There's that pivot point I told you about and it’s very critical. What are the restraints to ankle joint motion? The reason I'm covering all this is so that you can appreciate the current designs of total ankle. Like what's so hard about making a total ankle, they can do the knee, they can do the hip. Well, interestingly, the motion of the ankle is far more complicated than either of those two joints. When you look at this, you have to take into consideration the ligaments, you have to also take into consideration the anatomy of the joint because of the constraint that’s allowed. If you look at this, all of this has been study and it's very interesting. This is a very interesting point. Lowery estimated that the elastic modulus of the distal tibia was 300 to 450 millipascals. He also estimated that when you remove the subchondral plate, which you do in every total ankle replacement, you decrease the ability to withstand that elastic modulus by 30%. If you are to take out one centimeter of bone proximal to the joint, you reduce it 70% to 90%. Consequently, you need to pick a device that removes the least amount of bone on the distal tibia.
Additionally, the posteromedial part of the tibia where the neurovascular structures are, are stiffer than the rest of the joint. They act as a pivot point which causes the anterolateral portion of the tibia to fail. When you look at failure of total ankle replacements, they occur in two places. They occur with talar subsidence and they occur in the anterolateral portion of the tibia. It was also pointed out and let’s look at that. When you're looking at that, that’s the amount of talus, that's the amount of tibia, notice that those cuts go dangerously close to the medial malleolus and you really don’t want to go any closer than that because you will put the medial malleolus at risk. You need to conserve bone at the distal tibia. Trouillier showed that 90% of the force transmission occurs within the cortex of the distal tibia, the cortex of the distal tibia. Therefore for long-term success, you need to conserve as much bone as possible. It also makes revision easier. Remember that the longitudinal studies show about anywhere from an 85% to 92% survival rate at eight to 12 years. That means that someone in their 50s who gets a total ankle replacement is probably looking at a revision surgery. You would hope that you would be able to revise it with another implant, but in fact that may not be necessary, especially with some designs that are available. This is the amount of bone you're looking at and anything more than that puts this area at risk. So you're looking for designs that remove the smallest amount of bone. How about contact areas of the ankle? Well, the contact are of the ankle is about seven square centimeters. As you go from plantarflexion to dorsiflexion, the contact area increases and therefore, the force per unit area decreases. Also, the lateral facet loads and the medial facet unloads as you go from plantarflexion to dorsiflexion. Here's a description of that showing on top the loading in plantarflexion and how that increases to the bottom picture as you go into dorsiflexion. The more area that you load in any joint surface, the less the load per unit area. The figures are these. During gait, the ankle supports about 5.2 times body weight, three times body weight in deceased and replaced ankles, AP and lateral shear is two to three times body weight and therefore, the amount of weight at the implant interface has to be about three times higher than in the normal joint. So not only did you have to replace the joint, you have to actually make it a little bit biomechanically more sound than the true ankle joint. Ground reaction, gravitational ligament and muscle forces produce a mixture of 3D compression, shear, torsional loads in the ankle so at the implant interface, the forces are angular, not direct perpendicular. Why do they loosen? Well, gee, all the forces coming down through the tibia, that shouldn’t be that big a deal. Well it’s not. It’s an angular force. It causes stress risers. It causes a shear at the interface between the implant and the bone and that's what leads to its failure. In the treatment hierarchy of ankle, we go through a lot of different modalities from nonsurgical NSAIDs, physical therapy and bracing, all the way to viscosupplementaton, arthroscopy, destruction. The question is what's the standard of care for the ankle.
Is it fusion or is it total ankle replacement? I'm not sure that question has been answered yet. But it depends what facility you go to because in some facilities, total ankle replacement is the standard, in others arthrodesis is the standard. You simply have to look at the literature to figure out that we haven’t solved the ankle problem yet, have we? In fact, I just recently read an article by Giannini from the Rizzoli Institute in Bologna that showed an excellent long-term followup, sorry midterm followup of size, mass, allogeneic joint transplants, cadaveric joints. Maybe that’s going to go into the equation as part of the process of what we can do for the ankle. Here are the first generation TARs. They all use cement. Because they use cement, you had to resect more bone because you needed to make room for the cement mantle and then the implant. They were very constrained. Because they were very constrained, they led to loosening. The instrumentation was laughable. It was almost a freehand artistic approach to the ankle and in fact, when the STAR Ankle came to this country and was purchased by Small Bone Innovations, when they took it to the FDA, the FDA said “We can’t let you use those instruments. They're substandard.” So they had to redesign the whole instrument tray in order to be able to put the implant in. In Europe, things have changed somewhat but the STAR was put in much like Michelangelo would for many years without accurate instrumentation. There were a lack of revision strategies. When you look at the ankles that are available, you can scratch DePuy’s Agility. That’s been taken off the market. What is available for us to use right now is of the two piece, class 2 devices are the INBONE or the Wright family of implants, the Salto-Talaris and the new one is the Zimmer Trabecular Metal arthroplasty, which is a lateral approach arthroplasty. If you look at the three-piece implants, there are only one. There's only one implant in this country that mobile bearing, and that's the Scandinavian Total Ankle Replacement. The question is, is it really that much better? I like to look to Europe. The reason I like to look to Europe is that usually given their socialized branch of medicine, when they do something it’s usually because it works and not because they're getting excess remuneration for it. Today, with little exception, the majority of total ankle replacements done in Europe are mobile bearing. The Salto-Talaris, which is fixed bearing in this country is mobile bearing in Europe. So you have to take that into consideration because they’ve been doing total ankle replacements since the ‘70s, okay and they’ve all switched over to mobile bearing implant. What are the indications? They're obvious. Primary osteoarthritis, which by the way is rare in the ankle. Secondary or systemic osteoarthritis to inflammatory etiologies and posttraumatic arthritis. In my practice posttraumatic arthritis is in fact the most common etiology. That brings in some problems to the mix because these people usually show up with extensive soft tissue scarring. When they do, it makes the procedure more difficult to do and it makes the range of motion less. You can add a nice articular surface but if the soft tissues won’t allow motion, it’s not going to happen. But whatever the etiology, you must have a good bone stock, you must have near normal vascular status, you would prefer the patient not be immunosuppressed, you would prefer the lower extremity be aligned. And if it isn't, you need to align it either during the implant procedure or before you do the implant.
You actually have to have some range of motion. I can tell you from my own experience which mirrors that of the literature that a stiff ankle preop is a pretty much a stiff ankle post implant. Not painful, but stiff. If the patient’s main goal is range of motion, you better let them know that that’s going to be difficult to achieve based on the conditions of the soft tissue. They have to be willing to reserve their activities for low demand, low impact activities. They are not going to be able to run, they are not going to be able to do any athletics that require anything but a nice straight level ground activity. Patient’s age. Be aware of the fact that right now, the indication says 55 and older, does that mean it can’t be used in younger patients? Not really. What it means is it’s only been tested in 55 and older. I have patients in their 40s on whom I've done total ankle replacement. If you look at the papers out of Duke and from Mark Myerson, you'll see them stretching that indication younger and younger and younger. As the implants come out with less bone resection, that becomes a viable option because you then have a patient who is able to be rescued when that implant or if that implant fails. Weight, 250 pounds is the weight limit. Well, they don’t use weight in Europe. They use BMI. The size of the implant is directly proportional to the BMI of the patient. But in this country, weight means they’ve only tested it up to 250 pounds. Now I'm from Scranton, 250 pounds is cachectic in Scranton, okay. Most of my patients are that size or larger and consequently, we have the total ankle replacement in patients who are far heavier than that. I think my heaviest is 310 pounds and he is in fact one of the most successful cases. I don’t think it’s a contraindication. I think it determines which implant you use. The soft tissue, if you’ve got stiffness preop, you're probably going to have stiffness postop. You must have ligament balance and you test that at the time you place the implant in and if there is ligament imbalance, you need to fix it. You definitely need to fix it. You need both lateral and medial ligament balance. The lateral ligament balance is easy to repair. We’re used to doing it. The medial ligament balance is a little bit more problematic because we’re not used to doing that to any grade extent. Malalignment and malunion. It is generally accepted that if you have knee arthritis, you must fix it first. If you have a lower tibial deformity, lower tibial deformity in the supramalleolar area of greater than 10 degrees, you probably are better off fixing it first and then coming back and do the total ankle. Two observations. I'm a big deformity planning guy. I do a lot of deformity correction and I have found that almost half of the patients that we realign the tibia on don’t need the ankle. As soon as you realign the tibia and equalize the stress passing through the ankle joint, they miraculously improve. Even if you haven’t improved their range of motion, their symptoms decrease. That's another reason I do the realignment first. If I don’t have to subject them to a total ankle replacement, all the better. If you have mismatched columns secondary to trauma, it’s very common in a [indecipherable] [29:43] situation, then what you need to do is fix that because you need that lateral stability. There are some foot deformities that I will correct at the time of doing the total ankle replacement, but there are others I won’t.
I’ll do a calcaneal osteotomy, I’ll even do subtalar joint fusion, I’ll do a first ray osteotomy and that’s about it. Anything more invasive than that, I correct first and then we come back and do the total ankle. Steve, I'm going to continue with this talk please. No, I'm going to continue with the one I was doing. Cool. Okay. Deltoid spring ligament insufficiency, ATF instability, varus heel, you can do a Dwyer with or without translation, valgus heel you can do medial translation osteotomies. You may even have to do a triple arthrodesis. What about ankle contracture, do you need to do a TAL or gastroc recession? Well, if you listen to Roger Mann, he never does a TAL. If you listen to Mark Myerson, he always does a TAL. They can’t both be right, correct? What we do is we put the implant in and test the range of motion. That doesn’t sound like that difficult a concept. We can either get it above 90 or we can’t. If we can’t, we do a gastroc recession along with the procedure. What you really want to do is avoid overlengthening because that severely affects propulsion and actually worsens the gait instead of improves it. Now there are absolute contraindications to doing a total ankle replacement. Obviously, neuropathic disease is one, active or recent infection, AVN of greater than 50% of the talar body, severe benign joint hypermobility. There are some feet you just can’t stabilize the soft tissue in. I don’t see too many of them but I have seen them. Feet that are nonreconstructable because of malalignment, severe soft tissue injury, sensory or motor dysfunction, you need fairly normal muscles to power the arthroplasty and high physical demand activity of patients. You don’t want those. There are relative contraindications, previous severe trauma, open talar body dislocations, segmental bone loss. A recent article in the literature stated that the stem of the STAR endangers the blood supply to the body of the talus on a routine basis. I would have tell you, I have not seen that but it’s quite interesting to read and to see in their cadaveric specimens. If you have AVN less than 50% of the talar body, you may be able to get away with a total ankle replacement. If you have severe osteopenia or osteoporosis, that's a relative contraindication. Patients who are on long-term steroids, insulin-dependent diabetics, not because they won’t tolerate the implant but the chances are that they're going to develop a neuropathy somewhere in the near future and those with demanding activity. Let’s look at the implants. There are two design philosophies, constraint which means that the actual device itself constrains the motion or conformity congruency which means that the shape of the implant hinders the motion. One of the first things that I ever did when I did a DuPuy Agility ankle. I did one at my hospital some years ago now and I ran over to show my total joint surgeon at the hospital what a great job I did. He looked at it and said, “Yeah, that looks pretty good.” He said, “But tell me, why doesn’t it look like an ankle?” That’s an interesting point, isn't it? If you put a total knee in, it looks like a knee. Put a total hip in, it looks like the hip. The DePuy Agility didn’t look like an ankle, and that I think led to many of its problems. You can classify total ankles many different ways. You can do it by how they are fixated, cement or no cement, the number of components, two or three, how they are constrained.
Are they constrained, semi-constrained or nonconstrained? Are they incongruent or congruent? The DePuy Agility was incongruent. The majority of the others are congruent. Are they nonanatomic or anatomic? Most of them are anatomic now. Are they fixed or mobile bearing? If you look at the devices that are available, cross out the first column, we won’t even cover that, you have the Zimmer TMA, Salto-Talaris, INBONE or Wright family of implants and the STAR. Now interestingly, the Zimmer is put in with bone cement. The Salto-Talaris is uncemented. The INBONE is uncemented and the STAR is uncemented. The only problem with that scenario is that the STAR is the only one that has FDA indication to be used without cement. If you put in any of the others without cement, it’s off label. That’s not necessarily a problem as long as you're aware of it. Okay. But all you have to do is to listen to some of the ads that I heard when I was at a meeting in Florida on TV about, did you just get a total ankle replacement, I knew exactly what they were looking for and bore out, they were looking for the fact that if you had a bad result with a total ankle replacement, they got you if you're using it off label because even though you used it without cement, they were only approved for use with cement. Big problem. Not that you can’t beat that, but it’s a problem. Component shape, very important. All of them are basically anatomic except the Agility. The bearings are fixed in all of them with the exception of the STAR which is mobile and most of them have a plasma spray that allows for attachment to bone. The Zimmer by the way is the newest one in the market and it’s a transfibular approach. I've only done one of the Zimmer implant and waiting to see how that in fact works. Interestingly, the reason I'm interested in it is that I don’t like the anterior approach to the ankle. There are complications that can occur with that anterior approach so the lateral approach made sense to me. Unfortunately, you have to osteotomize the fibula and then repair it with a plate on your way out so it remains to be seen how well that's going to work. There are advantages to having a ingrowth spray on the implant, referred to as cementless implantation. First of all, you have to resect less bone because you don’t need to make room for the cement, so to speak. If you don’t, you avoid the cement extruding into the joint damaging the soft tissue and you can use a smaller prosthesis which I think is important. It’s been my bias that everybody looks at the AP view to size the implant. I think that's the wrong view. The view is the lateral view. You have to make sure that the tibial component is covering the anterior and posterior cortex. That's where it gets its strength. Anything shorter than that is a problem. These second generations TARs do have problems, malposition, improper sizing, improper use of distraction. I rarely use distraction but I won’t hesitate if I have to. If I have a sever posttraumatic case which makes resection of the bone elements difficult, I’ll distract that joint in order to make it easier, malleolar fractures and tendon injuries. Keith Wapner from Philadelphia said in 2009 and I don’t think this question has been answered is whether a two component or a three component ankle is going to be the best design. I'm not sure we know that yet. Preoperative planning is important. I won’t belabor it but you need to make sure your heel is no more than one centimeter lateral to the tibia and in fact, that it is in parallel to a bisection of the tibia.
If you have significant valgus, it’s going to be a problem. Significant abduction of the foot is going to be a problem. This is the kind of alignment you need. I always look at the extremity from hip to ankle. I want to know where the mechanical axis of the lower extremity is because sometimes I have to place that joint a little bit more medial than usual, a little bit more lateral than usual. It all depends on where I put it is where the mechanical axis of the lower extremity will pass through the center of the knee and I have to vary its position frequently because of that. Surgical approach is direct the anterior in all but the Zimmer. Most people will make a midline skin approach and then in the deep incision, their axis to the ankle will be between the tibialis anterior and the extensor hallucis longus. Why? Because you destroy the least amount of structures by approaching it that way. There is a branch of the intermediate dorsal cutaneous that is at risk when you do this and the patient should be warned about that preoperatively. They may in fact have some numbness on the medial aspect of the hallux. But you can see how tight fitting these joints, why distraction may in fact be necessary in some cases and why it’s difficult to resect bone in some cases. Let’s look at the Salto-Talaris. The Salto-Talaris is probably the easiest one to put in, in my estimation. It has some features you should know about. Number one, built in to the talar component is a ridge that allows approximately four degrees of rotation. That's nice. Most of the studies show you need 13 in normal walking. Well my answer to that is we’re not putting them in normal patients. We’re putting them in patients who have shorter strides and affecting their gait pattern and consequently very few of them need 13 degrees of rotation. But you can see that as you go through a range of motion, the talar component builds in the rotation that occurs. This is their answer to the mobile bearing. I'm not sure if it’s better or worse. All I can say is I don’t use Salto-Talaris regularly and one of the reasons I don’t is because their device in Europe is mobile bearing. I think it’s difficult to get the fixed bearing implant in Europe and quite frankly, would I hesitate to use the Salto-Talaris if every other one went away? No. but given a choice, what I usually say to the rep is well, if the fixed bearing implant is so good, why don’t you sell it in Europe. Why are you using mobile bearing over there? Okay. Consequently, if I had little old lady very few demands low impact, I wouldn’t hesitate to use the Salto-Talaris. I think it’s easier to put in bone resection and provided you follow all the activity constraints, it works pretty good. This is the INBONE which I have used. In fact, I use this routinely for a while and I still think it’s a very good implant. It comes with a positioning tray. All of the work is done through the bottom of the foot so you have to drill through the subtalar joint. Everybody got nervous about that. It has never caused a problem in any of the cases I've done. All of your rimming is done from the bottom after you cite your devices and you can see the bone resection and also the tibial cut guide is based off of that initial drilling. The only thing I say about the INBONE is look at the amount of bone I had to resect from the tibia, alright? It’s huge. I'm thinking down the road, if I have to revise this, even if I say look I can’t implant you anymore, I'm going to have to fuse you, I'm talking about massive graft.
Remember, we’re not even looking at the talus yet. Something is going to happen to the talus so I'm talking about a limb shortening that’s huge and consequently as stable as these are, I’d rather reserve this implant, and I do, for revisions. And the reason I do it for revisions, you will see on some of the postops. A very accurate guide, I love the instrumentation for this. you can see the rimming. It has a modular stem so you can make the stem as short or long as you wish. This is the reason I think it’s a good revision implant. You bypass the bone that’s been damaged with the original implant and you're relying on intramedullary fixation. It does have utility and I will use it for that purpose. You can also put in these struts to help support the talar component. Here you see it in place. It’s a very nice implant. It preserves the medial malleolus. The talar component probably could cover more of the lateral facet of the talus. The only problem I've ever had with an INBONE is some ectopic bone formation around the lateral malleolus. But as far as patient satisfaction, there's been excellent patient satisfaction. You can see how well this incorporates into the medullary bone. The FDA in its wisdom somehow classified the stem for the talus as a custom product or experimental and you don’t see it here but one of the designs for the talar stem was a long one that would go down through the subtalar joint which made so much sense to me especially if you had a deceased talus and you could access the calcaneus for support. But for some reason, they didn’t allow that to happen. Here you see it in place. It’s very anatomic. Here's a short stem. The only problem every time you add a link to the stem, it’s an additional $1400, so when you're capping out these things and the hospital is asking what's the approximate price, they give you the price for a four-component stem. If you go up to six component, it’s about $3000 more. The hospital gets a little angry. But it doesn’t matter. By then you’ve already done it. You got the procedure done. Here's a patient who had a triple arthrodesis and eventually wore down the ankle and here's the INBONE implant in place. Gave very good range of motion and was very happy about it. The STAR implant started as a fixed bearing implant. It was introduced in 1981. Kofoed who designed this was not happy with the results of the fixed device so he began then to use it without cement and just have a plasma sprayed components that improve the results and longevity. But what really made the results in longevity good was when he went to a mobile bearing. It has a flat tibial component with two anchorage bars, ultra high molecular weight polyethylene and a convex cylindrical talus. What I like about the talus component is that it resurfaces the entire talus including the medial and lateral gutters. So I've had the least problem with ectopic bone with the STAR. Now, I don’t know if that’s because of the mobile bearing or if that’s because it resurfaces the entire talus but I’ll take it regardless of what's doing that. It is fully congruent. The meniscus articulates superiorly with a flat surface. It’s interesting, when you put this implant in and the incision is open and you put the joint through a range of motion, you see the mobile bearing moving all over the place. The mobile bearing is self-centering regardless of where the joint moves, the bearing wants to move to the center of the joint.
That's the advantage of a mobile bearing. It is a class 3 implant. As I mentioned, it has the vacuum plasma spread components. Here's a STAR implant in place. One of the things I notice immediately is that it has involve minimal bone resection. I think if this fails, I think this is very easy. Easy, I think this is a doable situation where you can revise this without excessive shortening and without massive bone grafts. Here's another one in place. You have that implanted metal in the polyethylene meniscus so that if you put this joint through a range of motion under fluoroscopy, you can see what that meniscus is doing. This was an interesting patient. This patient about seven months after having a STAR implant put in, fell down a flight of stairs. She then waited the next six months waiting for it to get better and it didn’t. When she walked in the office, I thought she was coming in for like her basic checkup. I noticed when she walked in, that she was walking on her medial malleolus and I said, oh my god. The whole thing came apart. Actually what happened is that she had that accident where she fell down the stairs. Now what I find from all of these implants is that the only thing that wears is the polyethylene insert. That's the only thing that wore here. Falling down a flight of stairs, she didn’t loosen the tibial component, she didn’t loosen the talar component. All she did was damage the poly and interestingly enough, I hear a lot of people say the implant failed, the implant failed. What fails is the surrounding bone, not the implant. The implant when you open the metal components are usually pristine. This is what you expect to see after you implant a STAR and it looks very nicely. Again, notice the medial malleolus is preserved and the lateral gutter is covered. You have to do additional surgeries with total ankle replacement. Lateral ligament reconstruction, peroneal tendon transfer, osteotomies of the first metatarsal or calcaneus. You may need to lengthen the heel cord. You may need to do displacement osteotomies or repair the ligaments. Now there are complications. The biggest complication regardless of the implant you use is wound healing because of the anterior approach. For that reason, we make our incisions longer and avoid retraction. One of the things I notice with residents is that when a resident is retracting for this case, they retract whether or not you're doing anything, right? I frequently have to hit them on the back of the hand and say, relax that retractor. So our incisions for putting in total ankles are 18, 20 centimeters long and they’ll go down just short of a Lisfranc joint and as high as the junction of the lower and middle third of the tibia. Retraction is much easier on the skin when the incision is longer. Edema happens. I don’t find it to be much of a problem especially when they start to use. DVTs can be a problem. We do prophylaxis for that, although I can tell you I have not had a DVT with total ankle replacement yet. Probably pure luck. We do prophylaxis for it because they are two weeks nonweightbearing and they are six weeks in a cast. So I think that’s disturbing the biology enough to worry about prophylaxis. The syndesmotic nonunion we don’t have to worry about because that’s an agility problem and they're always at risk for fracturing the malleoli. Late complications, loss of motion. It does not seem to be involved with patient satisfaction. It’s more doctor satisfaction about the motion. Patients may mention it but they don’t have pain between because of it. Aseptic loosening, even those of us who put in first MTP joint implants, that loosen.
It’s called aseptic loosening. The recent literature would say that many of the cases of aseptic loosening are actually in fact none or culture negative infections. The way that was found was by doing DNA polymerase chain reaction evaluations of the exudate. Many of these joints that loosen may not be aseptic loosen. They may actually be low grade infections and therefore whenever we have any implant loosen or whenever we take an antibiotic spacer or beads, we send it down for polymerase chain reaction. Something called vortexing and sonication. This is great cocktail party stuff. I hope you remember these stuff. Vortexing and sonication, meaning we put it under a high pressure wash and then in a sonicator, bombards it with ultrasound and literally shakes loose all the bacteria from the glycocalyx that’s covering the implant, the screw, the plate, the antibiotoic spacer. And then we let that determine what are antibiotic treatment program is going to be. What about salvage? Well here's our protocol. If we have to remove an implant, first thing we ask ourselves is, is it infected? If we’re not sure, then we treat it as if it was antibiotic spacer and we wait until we find out from the polymerase chain reaction evaluation. If it’s not infection, the second question is, is there a good bone stock? If in fact there is, then we do a revision TAR. If it is infected, we use antibiotic beads or spacers, IV antibiotics and frequent debridements and washouts of the wound. Then we either cure it or we don’t. If we cure it and there's good bone stock, we do a revision TAR. If we can’t cure it, we try and do a septic fusion. If we are successful, great. If we’re not successful, all patients having a TAR will have to realize that should it go horribly wrong, they may be a candidate for an amputation. I think it’s better that they make their decision knowing that upfront than finding out somewhere during the postoperative period that that may in fact be a reality. So I have this written out. I go over it with the patient who's getting a total ankle replacement and want him to make sure they know that number one, we do have strategies to manage failed total ankle replacements. But I want you to know that it’s no cake walk. It’s involved and sometimes it won’t work. Alright? So that’s my coverage of total ankle replacement. I'm sorry I didn’t have time to do Lisfranc joint. But I think as practitioners of the foot and ankle, whether you do it or not, you need to be conversant in the advantages, disadvantages and options that your patients have with respect to total ankle replacement. Thanks for your attention.