Harold Schoenhaus, DPM, FACFAS discusses the use of intraosseous fixation technology and its benefit when performing talonavicular fusions. Dr Schoenhaus begins by discussing the advantages of the intraosseous fixator over traditional fixators. He provides a wonderful pictorial while describing the IO fixator technique.
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Harold Schoenhaus, DPM
Surgical Editor for PRESENT e-Learning
Penn-Presbyterian Medical Center
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The talk that I�m going to be sharing with you are some thoughts on isolated talonavicular fusion. And one recognizes that fusing the talonavicular joint becomes a very powerful procedure � not only what it does at the TN level, but its effect and influence on mid-tarsal and subtalar joints. And you almost eliminate close to 80%, could be as high as 90%, of subtalar motion, along with your talonavicular fusion. So here�s an isolated procedure that is very powerful. And I�ve been doing these for a good number of years, and I probably am going to go back to doing more because of the ease to do it and the maximum benefit in restricting motion within the rear foot.
Now, obviously, as a resident or as an attending, we appreciate various methods that are available for fixation. Performing a surgical procedure is obviously something you�re going to be trained to do � denude a joint, take a section out, whether you�re doing an in site two type perfusion, you use an impact osteotome to retain the shape of the talonavicular joint, which is a ball and socket joint. Or are you going to resect sections and try to put it together, and you end up shortening the medial column too much? So one is the technique of debridement of a joint. Two is the selection of what material or what methodology you�re going to use to create an arthrodesis. And obviously, compression is something that we consider very important at a joint site, just as Jason Miller was talking about, locking plates and compression and an interfrag screw that�s giving compression at a joint, because we recognize that is a critical component. The other critical component is stability at that joint level, so that you don�t get distraction, rotation, translation, where motion might take place, or change in position.
So historically, obviously we see various methods of fixation. And what I�m going to share with you today is one that I�ve been using for about 6 to 8 months which has made a dramatic difference in my approach on fusions. And I think if one thing you�ll learn as a surgeon is when you put plates on, there�s one thing we have a problem within the foot, and that is prominence of hardware. Even screws. And certainly the headless screws, different companies have headless screws, and you bear down into the bone to create a nice defect so that the head of a screw might fit into that area. The end result on many patients is that plate is offensive. Over a first met cuneiform articulation in the rear foot, heavens, I don�t care where I put a plate on � inevitably a patient irritates with that plate, and now we have to go through a second surgical procedure.
Another component that Jason mentioned is screws, when you use them to create an arthrodesis � how far away from the joint you have to come because you�ll have to create either a stress riser, as the head of the screw engages the bone, or you won�t get enough compression.
So let�s take a look at some things. This type of screw is considered intra-osseous advantage because of the superior biomechanics. And we look at a zero profile � zero profile. I want my metal to be flush to bone when I�m done, so there will not be that possibility of irritation. We want superior compression and uniform compression. So when you�re looking across a joint that has a ball and socket component, one recognizes that may be a little more difficult to get what�s called uniform compression. A first met cuneiform or even a first metatarsal phalangeal joint, we have the ability to get more uniform compression. Or if you�re doing a cut that�s going straight down on both sides and you now put them together, little easier chance to get better compression. You want something that
has superior pull-out strengths. Obviously this thing cannot just come out of the bone. Superior bending fatigue, and this reinforced cortical bridge. Very important.
So in addition to these factors, as a surgeon I do not want to use hardware that�s going to cause me an extension of the procedure that�s longer than what it did for me to resect the joint surfaces. I don�t want to spend an hour putting a plate on and trying to ideally place everything in position. So I want a short learning curve, and then I will be honest with you � with residents we need a short learning curve. And sometimes it�s a long learning curve that by the time you�ve finished your residency program, now it�s become a short learning curve. We want fast cases with reproducible results, and obviously clinical outcomes and versatile applications. So you can look at this comparison of where we�re accomplishing what with various types of instrumentation to create compression.
The concept is simple: you�re placing a single post down along the side of the joint from let�s say dorsal or planar in this case. That�s going to be one post that�s placed in. And then we�re going to create an angular position across the joint surface, coming with another screw. And now we find as the screw engages the hole within this post, we get compression across the entire site from dorsal to plantar, just by the very position of this one particular screw, which you can see has pretty good sized teeth on it.
So uniform compression becomes important when you think in terms of, what types of osteotomies do we create or fusion sites do we want, and how do we go about getting compression that�s even from dorsal to planar? �Cause often you�ll take a post-operative X-ray and it�ll look like the joint is closed on the top but it�s opened on the bottom. And then oftentimes, in foot and ankle surgery, we�ll look at the fact that plates probably should be placed on the plantar aspect of the foot, and yet we don�t do it just because it�s far more difficult to get access. But what we�re looking to accomplish is uniform compression, and when you put a screw across a site from dorsal to plantar, here�s the point of compression that you're going to get, and the whole portion on the bottom is closed, oh, is open, or doesn�t have the compression we want. And yet you as the surgeon may be looking primarily at the dorsal aspect, giving a high five, saying, we�ve got the compression. So we do not get uniform compression with a single screw, and then obviously, now you�re going into a situation where multiple screws at different angles have to be placed. Doesn�t necessarily mean that we�re getting the compression down at the bottom. If we put a screw from plantar to dorsal and dorsal to plantar, then we may be getting compression across the joint more uniformly.
So this is obviously what we�re attempting to do with this new design of a screw. The other beautiful part is the head of this screw engages the metal, not bone. And this enables me to put that screw pretty close to the joint. Now Jason had said, you can�t put it too close to the joint. Here�s a type of fixation that enables you to get a lot closer. And now you�re getting uniform compression with this modality. And there�s that cortical bridge I was just talking about. We can come pretty close to that joint margin, because the metal is what that screw is engaging, and you won�t create a stress riser or break through the cortex. I�m sure you�ve experienced in the OR, putting a screw across a site, and the residency director attending says, �Be careful � don�t screw too tight� � and you hear that little crack, and you look and you see that little line, and you go, �Oh, cripes.� Can �t go back on that. What do
you do? You put your chewing gum in there?! You do something else to reinforce it, recognizing as soon as that has happened, you lost the compressive capability.
All right? So the indications for this are kind of variable in the foot. Triple arthrodesis, TN fusion, CC � you can look down the list. I�ve had good experience using it on isolated talonavicular fusions, tarsal metatarsal, which is the lapidus procedure, and first metatarsal phalangeal fusions.
This is typically what one looks on an X-ray, seeing here�s the post coming into the navicular, and then up into the talus, to give me compression across the joint.
Now obviously, I have used various forms of fixation in 41 years, whether it be staples, screws, external fix, plates, claw plates, and this little guy here, which I think is now my favorite one to utilize. And you can all see, you�ve all seen different modalities that have been effective. I�m not here to throw everything out that�s been done in the past because it�s effective and has its place. All right? Crossing screws do work, and here�s that isolated talonavicular fusion, which is very powerful in retaining the shape of an arch and limiting the motion at the subtalar and mid-tarsal complex. So in patients who have difficult circulatory problems, or they may be a little bit higher risk, this type of procedure requires far less dissection than going in for example and doing a triple arthrodesis. And certainly there�s screws of different types used. There�s external fixation. It�s amazing we come up with techniques to do when we have various modalities provided for us. When external fix came into the environment, probably 25-30 years ago, we were looking for things to fix externally. And believe me, we found everything. We have enough things in the foot, and enough joints that we can fix, including phalangeal fractures � I mean, it�s just mind-boggling what the heck we try to do. Not necessarily the best for the patient, however.
All right, here�s a claw plate. Very effective, it works. It�s like a compression staple. Obviously the effectiveness of this device requires screws to go deep into the bone to get compression that is as uniform as possible. But recognizing you�re still getting most of your compression right at that level. And then of course the prominence of hardware itself.
The role of fixation is simple � maintain position, stabilization, compression, local and global is what I want. And allows if bone-grafting is necessary, there are times when you may have to alter your fixation and use different modalities.
This device can be used very effectively in cancellous bone, cortical bone, reduced need for additional exposure, and lack of prominence to hardware. So here�s an example of an isolated TN fusion. I don�t care what direction you use to do your dissection. To me I like a KISS principle � keep it simple, stupid. I go into the joint, open it up with a laminar spreader; I use an impact osteotome, follow the contour of the joint, get the cartilage off, get the subchondral plate off. I want to be down to nice cancellous bone. You gotta get past the subchondral plate. If you don�t you run a higher risk of non-union. So what do we do if you leave subchondral plate? You take a two-oh drill bit and fenestrate the heck out of those adjacent parts of the joint to allow for vascular channels to go through the bone and allow for the fusion to take place. If I can get down to cancellous bone, that�s my ideal.
All right, here we are. If I want to use an interpositional graft, I use various materials to fill voids, and then I�m ready for the actual technique of locking this joint in place. Now in the
exhibit hall they have a beautiful model that you can see how this is done, placing pins through. Everything is well-calibrated for you. It�s a cannulated approach. It�s again, that KISS principle. The screws come in variable lengths. The navicular is a small, wafer-shaped type of bone, so you�d better be careful as to what you�re going to resect and how much space you have in placing your transverse screw or vertical screw in the navicular to get my compression.
And you can see here how we are now going flush into the metal portion to get the screw that�s going to go in so there will be absolutely no prominence when this is done. And here�s a good example � here it is. There�s the post in the navicular; here�s the screw coming back into the talus. And we�ve got great compression across the joint which is uniform. There are times I will use orthobiologics to fill any void, whether I use sponge material or injectables to help fill voids. And ideally this is what you�re trying to obtain: the uniform compression across that joint, and go on to a complete fusion.
Now, it�s interesting � I looked at some of my fusions that I have done through the years of the TN joint, and position is critically important. Once you recognize that by locking the talonavicular joint you�ve locked the rear foot, do not oversupinate, do not overcorrect. Here�s a position that you want to allow a little bit of pronation and watch the position of the navicular relative to the talus. And this one is pretty well-aligned. Take a look at that one. I mean, the fusion took place, but look what happens also in the foot. I just want to go back to this a minute. Here we�re looking at � this is the same patient, right and left foot. And very interesting, look at the adaptation that has taken place. The ball and socket joint has been eliminated. Over time you get functional adaptation, and I always thought that functional adaptation readily occurs in a pediatric population, not so much in the adult. But it�s very interesting to see in this patient, they actually started to develop a ball and socket appearance past the navicular. So the cuneo-navicular articulation apparently is giving them the additional motion lost by the TN fusion, and this patient ambulates beautifully on both sides.
There�s a good shot of this method of fixation � vertical post, and another one coming down this. This is for a lapidus procedure, okay? So there�s various orientations you can use this for fusions of the joint. And I�ve gone to this pretty exclusively now on my lapidus. I do have a tendency of using a transverse screw by the way, from the first to the second cuneiform, to prevent increase in the IEM angle.
So what we�re trying to accomplish is advanced technology which provides enhanced clinical results. And I think if nothing else, I welcome and thank the companies that we work with on a regular basis, that come in to bother us as surgeons and say they have something new, innovative. The surgeon has to be able to look at that and say, �Does it truly have application on my patient population, and is it of benefit?� Everything costs a lot of money. In today�s environment hospitals, surgeon centers, are very careful about what they are going to spend money on. And they are looking for outcomes research, outcomes data, to be able to show one methodology is better than the other.
So as residents, as surgeons, as attendees, we always keep an open mind and look for what might be out there to give me better results for my patients � more predictable.
And I thank you for your time.