Board Review Diabetic Foot

Charcot Reconstruction - Essentials

Guido LaPorta, DPM, MS

Guido LaPorta, DPM, MS, FACFAS discusses surgical interventions for Charcot reconstruction including the use of internal and external fixation.

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Goals and Objectives
  1. Discuss the goals and indication of surgical intervention for Charcot foot
  2. Describe the different classification systems for Charcot and how they can help determine which surgical intervention is most appropriate
  3. Describe the different types of external fixators currently available and the indications for each
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  • CPME (Credits: 0.75)

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  • Author
  • Guido LaPorta, DPM, MS

    Director Podiatric Medical Education
    Community Medical Center
    Scranton, PA

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  • Lecture Transcript
  • [Dr Frykberg] � now going to introduce one of podiatry�s best speakers, a good friend of mine for many, many, many years. I think Dr LaPorta has some of the greatest experience in managing Charcot deformities. He is a fabulous lecturer. He�s a real thinker. He always gives a nice academic approach to his subject matter, so let�s welcome him back to the podium to speak on surgical management. So welcome Dr LaPorta.

    [Dr LaPorta] Thank you Bob, and what I�d like to introduce to you today, maybe it�s not an introduction to some, but at least propose to you that in a great percentage of patients who come to surgical reconstruction, that the massive invasive procedures that we all look at from the audience may not be necessary � especially when dealing with mid-foot Charcot. We saw an excellent presentation yesterday from Dr Zellen. But I noted that in the majority of those presentations, the patient had an underlying bone infection. And consequently, when they present that way, you certainly have very little choice: you must completely resect all the infected and diseased bone before even attempting to get a solid fusion of that particular deformity. However, what about the patient who does not have an underlying bone infection? They have the deformity, they certainly probably have an ulcer, which is probably one of the main reasons you�re considering doing any kind of reconstruction. But the underlying bone is devoid of infection. Is it necessary to resect huge wedges of bone in order to realign that foot?

    Well, the short answer is No. But let me show you my thought process as we go through this. Bob covered this extremely well. What I tell patients is that I�m trying to make them a community ambulator. Can I golf again? Probably not. Can I play tennis? Hell, no. I would be satisfied if you, we preserve your limb and we allow you to be a community ambulator in protective shoe gear. So the objectives when we look at this particular deformity, you know, what are the deformities that are present? The obvious title of Charcot certainly brings up in our minds what we�re dealing with. But when I look at a deformed foot, I�m probably looking at a number of instances that I�m going to have to address. Now, these may not all be present, but in the majority of feet that I get to for surgical reconstruction, a lot of them are. We have ankle contracture. We have a varus calcaneus. Sometimes hard to believe that, when you see how laterally translated the heel is relative to the tibia. But just like in a calcaneal fracture, the heel is usually in varus. We have a rocker bottom foot, we have a supinated forefoot; the forefoot is usually in abduction, and the hind foot especially the talus and the superstructure is medially translated. Any one or a combination of those may be present, and a successful reconstruction depends on reversing and stabilizing those deformities.

    So when do I operate? Well, usually, I�m dealing with a patient who�s sent to me, who has a non-healing or recurring ulcer, and despite heroic efforts to get that to heal, it does not, and there is an obvious deformity of the foot, excessive pressure, and these patients are susceptible to underlying bone infection. There may be osteomyelitis. There�s definitely instability, and the foot is non-braceable, because if it were braceable, we wouldn�t be doing any kind of surgical intervention of a reconstructive nature. We would be considering planing and then converting that patient to an ambulatory brace. But if that�s not possible, then we have to think about reconstruction. So when you see a foot like this with a totally dislocated talus, you begin to think of stabilization, and your only question is, �How can I achieve this, and what is the best way to make this a stable appendage for this patient to function?�

    Well, as Bob mentioned, there are a number of classifications, starting with the Eichenholtz temporal classification that he covered very well. Brodsky, Schon and Lee Sanders and Bob�s classification, which we all use to teach the general concept of the natural progression

    of Charcot foot. But I have to tell you that when I teach residents the surgical intervention, I have to use the Schon classification. And the reason I do that is because I have to give them a roadmap. I can�t teach exceptions. I have to teach the rule, and then as certain patients come up who have maybe something out of the ordinary or different, then we can talk about the exceptions. But it does no good to do that unless somebody has a firm basis.

    Here�s the Eichenholtz � and I won�t cover this, Bob did this very nicely � but the Schon classification is very interesting. Much like the Sanders and Frykberg classification, it anatomically divides the location, recognizes the location within the mid-foot that Charcot occurs � the Lisfranc joint, navicular cuneiform, peritalar and mid-tarsal joint. What it does in addition to that is identify types A, B and C � A being the medial column, B the central column and C the lateral column. And on top of that it talks about an alpha, which is a focal deformity within the foot, versus beta. Beta is a totally unstable foot that encompasses the entire forefoot. And you can define beta by saying that (a) there is at least dislocation, and various angles that we can measure using the talar first metatarsal angle on both the AP and the lateral view, are above 30 and 35 degrees, and the lateral column, which I consider the most important angle, the lateral column is less than zero. It�s a negative angle. And that�s an indication to me that we have a very difficult chore on our hands, and that is to stabilize a foot in which the lateral column is unstable.

    So here we have a navicular cuneiform beta. This is a breakdown through the navicular cuneiform joint and out lateral Lisfranc joint. It involves the entire midtarsus starting medially and exiting laterally. Here is an alpha, and as soon as I say alpha, the deformity is predominantly medial column, and what that means to me � and I�ll show you in just a minute � is that when I say alpha, I�m thinking primarily of a limited intervention with internal fixation. I may supplement that with external fixation, but the heart of the procedure is a limited intervention with internal fixation. Whenever I have a beta foot, regardless of its location, that to me is primarily an external fixation foot that may be supplemented by internal fixation. So looking at the Schon classification of midfoot Charcot, I either have alpha or beta. Alpha means ORIF to me, beta means Xfix. And there are many good options for stabilization of columns in a focal manner and my preference is a polyaxial plate of whoever�s design. But I think this is an excellent application for a locking plate technology, polyaxial plates are a particular advantage, because within about a 15 degree cone, you can angle bone screws into what appear to be healthier bone and not rely on a fixed angle construct. What you�re trying to avoid is an inadequate assessment and fixation. And as good-intentioned as this surgeon was, I believe the reason this failed is twofold: he or she did not recognize that this is a beta deformity � consequently one needs to do something to the lateral column � and certainly the fixation applied medially is totally inadequate. So if we can avoid this, then we at least have a good start.

    So what are our strategies? Well, when we look at correction, correction can either be done acutely on the table or gradually during the post-operative period. Or you can use combinations of that. And if you apply an external fixation frame, you can do it in any one of a number of modes. You can do it as a neutralization frame, just like a neutralization plate. You fix something with internal fixation; you want to protect it with a frame until

    healing starts. Or you can do deformity correction, and deformity correction usually involves using an external fixator, and through various hinges and motors slowly correcting the deformity during the post-operative period in an attempt to save bone. Or you can use fixator-assisted augmented by internal fixation. What the heck does that mean? That means that you can use the external fixator to realign the foot either on the table or during

    the post-operative period, and as soon as the foot�s realigned, you go back to the OR, remove the fixator, and do minimally invasive arthrodesis techniques of the foot.

    So the strategy, when you look at Charcot, is that you�re doing either a static correction or a gradual correction. And if you�re doing a static correction with external fixation, you have your choice of using a circular frame or a monolateral frame. My recommendation would be not to even look at the monolateral frames, because I think they�re inappropriate for this deformity.

    For a gradual correction, you usually need some computer-driven external fixation device, or you have to be so good at Ilizarov that you have the ability to evaluate deformities and place hinges in the appropriate position. The common types of applications are either the Taylor spatial frame, Ilizarov, and in Europe, the hexapod. So using the Ilizarov method, you not only have to be facile in applying an external fixator, but in evaluating the deformity you need to put your hinges exactly where the apex of the deformity is so that as you move the fixator, you are correcting the deformity at its apex. This is not as difficult as it sounds, but learning how to do it is much harder than doing it. And consequently one has to do a number of them with this method in order to become proficient in it.

    Well, what�s my mid-foot Charcot strategy? Well, I think the beginning step is correcting equinus. And once you can do that, then you apply the frame and then after the deformity is corrected, you come back, remove the frame and use internal fixation if necessary. I must tell you that the method I�m going to show you, I learned from Drew Paley and John Herzenberg, and Drew Paley initially said, �You know what? If you put on a Taylor spatial frame, correct the deformity, and then keep it in that position for three months, they�ll all fuse.� They don�t. And consequently, what happens is that when the frame is removed � and this is the way we did our initial procedures � we supplemented it with internal fixation. Well the obvious question is, �Well, why didn�t you do that in the first place?� And the not-so-obvious answer is, that in order to use internal fixation initially, we would have had to resect significant amounts of bone. If we wait until the foot is aligned, the fusion is achieved simply by curettement of joints and application of internal fixation.

    In the beginning I did it this way. What I have switched to now is the same steps but I take the frame off much earlier. As soon as the foot is aligned, which in most cases is 14 to 17 days, back we go to the OR, frame comes off, and I use a formal minimally-invasive arthrodesis technique. So it is beneficial to reduce the time in the frame.

    I have two types of frame that I use, and all of them, or both of them, depend on whether or not I was able to correct equinus. One is called a miter frame, which I�ll show you along with a butt joint. When I have a miter frame applied, it means to me that I have to correct deformity not only in the forefoot but also the rear foot. Whereas the butt joint is used to correct predominantly forefoot deformity.

    This is Taylor spatial speak. It means probably nothing to you, and I�m not going to spend any time on it, but that�s what a butt joint looks like, within the circle. There�s a ring around the forefoot, a ring around the heel, and one ring on the tibia. And basically, what I�m saying here, when I use this, is that the hind foot is acceptable, not normal, and all I�m going to do is correct the forefoot relationship.

    And when in place, it looks a little daunting, but I can tell you there�s five wires in the foot. I mean, I don�t consider that, if you fused five hammer toes you�d have five wires in the foot. So I don�t think, everybody gets nervous about all this hardware, but realistically, it�s on the outside of the foot. And here�s what a butt joint looks like. So there�s one ring on the tibia, connected by two half-pins, a rear foot ring and a forefoot ring. And the struts connecting the rear foot to the forefoot are going to be moved according to a computer program which will allow me to reduce whatever deformity is in the forefoot.

    This doesn�t project very well, but here�s the exception, and after doing my posterior muscle group lengthening, and I would recommend lengthening over tenotomy, I then visualize that on c-arm, �cause all those feet move better after you do your lengthening. The question is, where�s the dorsiflexion coming from? Is it coming from the ankle, or is it coming from the mid-foot? If I am not getting my dorsiflexion in the ankle, then I have to correct the equinus that is residual. I can do that a number of ways. I can go in and start incising tissue on the posterior aspect of the heel, or I can stretch them. And my preference is to stretch them, �cause it will heal without scar. And consequently, when I have inadequate equinus correction, the foot pretty much looks something like this, and this is a classic miter frame application. A miter frame differs somewhat in that there is an intervening ring around the hind foot. So if you look at this, there�s a ring on the tibia, there�s a two-thirds ring around the heel in a miter cut application, and the two-thirds ring on the forefoot.

    So there are six struts connecting tibia to heel, six struts connecting rear foot to forefoot. And what I do here is that I first correct the rear foot chronically during the post-operative period, and then once I get the rear foot where I want it, then I�ll correct the forefoot. When everything�s lined up, back we go to the OR and I�ll put in whatever appropriate internal fixation is necessary.

    Sorry these movies don�t work, but they�re fairly demonstrative. It�s a shame. I�ll work on that for next year.

    Here�s what a miter frame looks like. So this patient gets two prescriptions. One for the rear foot and one for the forefoot, although they�re only doing one at a time. And you can correct six planes of deformity. Remember, every orthopedic deformity can be described by three translations and three angles. And as soon as you measure them, you know exactly what you have, what you're dealing with, and can feed it into the software. And here�s with the miter frame application. Again, two skinny wires in the forefoot, two skinny wires in the heel, two half pins in the tibia. No incisions.

    Now, the key to correction with a Taylor spatial frame is the mounting parameter. And I�m just going to go through a very short description of how and why you do this. In an Ilizarov frame you have hinges. You need to know where to put them. In a Taylor spatial frame there are no hinges. There�s a virtual hinge. You need to tell the computer where that virtual hinge is, and you do that through your mounting parameters. This is the toughest

    part � it�s a critical maneuver, with the software, and it�s the part most people probably have a problem with, and stop using the Taylor spatial frame because of it.

    For the sake of argument, let�s just say that we want the forefoot to rotate around the rear foot at that point. Okay? So that could be cora, that could be anything, all right? Wherever you decide you want that point to be. And we�re going to measure its position relative to the distal ring around the forefoot. So the first thing the computer asks us is how far away

    from the distal ring is that point. That�s called your axial frame offset, all right? Very simple concept � lateral orthogonal view of the foot, measure the distance of that point from the distal ring. The next thing it�s going to ask you on your lateral view is, what�s your lateral view offset? Meaning, from top to bottom of this ring. Where is that point? Is it right in the center? Is it above center? Is it below center? And as soon as you put that in, the computer now recognizes that you have two intersecting planes which in mathematical jargon give you a line.

    The third thing it asks you is, on the AP view, where�s that point relative to the middle of the frame? Is it right in the middle? Is it lateral? Is it medial? And this is called the AP view frame offset. So mathematically, once you define these three planes, three intersection planes form a point. The computer and subsequently the external fixator now uses that point as a hinge around which those bones will move. So obviously you can see that that�s a critical part. And once you do all that, you can take a foot that looks like this and using the Taylor spatial frame, align it, put in intermedullary screws, or rebar popularized by Bill Grant, and change that deformity significantly. You can take a collapsed foot like this and realign it, put in the rebar and get it to look like this. So you know, the obvious response is, well, what�s the big deal? I can do that. Yeah, but I can do it without incisions! That�s a big point, I think, in these diabetic patients, when you can eliminate the need for soft tissue healing. Some of them don�t look so great, but if I get a plantar grade foot, then put in my rebar, it�s a successful procedure; no incisional approach. One of the best devices that I�ve used for that is this mid-foot fusion bolt. It�s non-cannulated, very strong.

    So if I look at mid-foot Charcot, we have four kinds. We have Lisfranc, navicular cuneiform, perinavicular and mid tarsal joint. By definition, perinavicular and mid tarsal joint Charcot are all beta deformities. So in our institution at least, those all get traditional external circular fixation or Taylor spatial frame, followed by open reduction internal fixation.

    In the Lisfranc joint and the navicular cuneiform joint, we have to decide whether or not it�s an alpha or a beta deformity. The alpha deformity gets open reduction internal fixation, usually with a locking plate; the beta deformity gets Xfix or Taylor spatial frame, followed by open reduction internal fixation.

    So what�s been our result? Well, we�ve done 126 feet in 119 patients this way. Interestingly, no sex predilection, but we have a slight lean towards females in our study. All of these patients have had posterior muscle group lengthening, and � I�m sorry � and instead of boring you with all of these, this will be published soon � what this reflects is the fact that in the beginning we were doing and leaving the frame on for three months; now it�s unusual for us to leave the frame on longer than three weeks. And as soon as the foot�s aligned, we do minimally invasive arthrodesis procedures. The majority of our patients were in Eichenholtz stage 2, and the remainder were in Eichenholtz 3. I am not a proponent of

    surgery in Eichenholtz stage 1 unless it�s an unstable dislocation only, and I believe Bob mentioned this. No fractures, no fragmentation of bone, but a pure dislocation which can be stabilized. I think most Eichenholtz stage 1 can be handled with non-weight-bearing and some form of immobilization casting and/or compressive dressing. So I really have not been able to duplicate the results of Shirley Simon, even though it�s what originally got me interested in external fixation.

    So in summarizing this, I would say that you don�t have to be in the internal fixation camp or the external fixation camp. They�re complementary techniques. One makes the other

    more reliable. If in fact you are dealing with a focal alpha type deformity, you can use just internal fixation very successfully. But if you�re dealing with a beta, in which the lateral column is unstable, you must have some knowledge of external fixation in order to manage that deformity. So most approaches work. Do what you do best. I publicly like to thank both Lee Sanders and Bob Frykberg for piquing my interest in Charcot foot. There was a time when I didn�t care if I would ever see one of these deformities, and now I can�t wait for them to come into the office.

    It was a pleasure being here this weekend. I hope my presentations have been in some way helpful and informative, and good luck in your future practices. Thank you.