• LecturehallThe Fundamentals of External Fixation
  • Lecture Transcript
  • TAPE STARTS – [00:00]

    Speaker: Our first speaker of the afternoon is very popular speaker for our program. He comes to us live from Philadelphia, Pennsylvania, Dr. Michael Troiano. A wealth of experience with foot and ankle surgery wound care and that. Today he is going to be speaking to us about external fixation. So let's welcome Dr. Michael Troiano.


    Dr. Michael Troiano: Alright, good afternoon. Everybody is postprandial. External fixation, external fixation is something that unfortunately has to do to understand and it has bailed me out more times than I would like to admit. It is an integral portion of my practice. External fixation traditionally means Ilizarov frames and things like that but can be a simple as little pin-to-bar systems for metatarsal fracture. Each company has a little subtle nuances but the principle remain the same. So this lecture is meant to be more of a board review when you graduate and you take some of your boards and we hit a lot of fundamental, so try to keep it technical but at the same time try to make some interesting ideas out of this. Questions that we are going to discuss are what are the tenets of external fixation. What bone biology and fixation principles are involved, the indications and advantages, safe zones are important. Differences between skinny wires and half pins, constructs that you would use in everyday practice, the components to each construct and of course complications in how to handle them. And then I can tell you my postoperative course, which will probably be different than your residency director or your attendants or maybe your own as time goes on.


    So tenets, external fixation by and large is used in the lower extremity more advanced than any other body part. The idea is to provide enough stability to maintain intended reduction. Soft tissue maintenance is huge. The most external fixation we can do is just small incisions made and not too much soft tissue damage. We want to find at least two points of fixation through each main fragment. Ideally, those points of fixation would be in the same frontal plane meaning that there will be stacked side by side not necessarily one up one down. Rings and bars should be placed as close to the bone for stiffness as possible and you want to look ahead in that if you may convert some of the external fixation to internal fixation, you want to not burn your soft tissue window. Diameter is crucial. With any given bone, we have to recognize that the radius of the pin should not be greater than one-third of the radius of the bone. That's an important take-home. That's something that you will likely be asked on many tests that you take going forward. The radius of the bone should be less than -- the radius of the pin should be less than one-third of the radius of the bone, otherwise, you run the risk of cracking. Obviously, the intramedullary blood flow to any bone is pretty significant as well. So if you get into a bigger radius, then you serve to disrupt the blood supply to that bone. Stiffness is increased with the increased tension on the wires. Lot of people don't understand what tensioning is with the wire. Tensioning is basically you have a rigid point and then this tensioner which grabs the wire and really pulls it tightly like a piano string and by creating that tension, the bone responds. All the osteoblasts rest on that bone. It slows down the osteoclastic activity on the metal and this is the principle that allows Charcot to calm down faster.


    It's the principle that allows the fracture fragment to fall into line tighter if we are not talking about Charcot, we are talking about fracture. This also allows for earlier weightbearing. Earlier weightbearing is an important tenet to any foot and ankle surgery not too soon but right around the four to six week of bone fixation. Cyclical loading or dynamization of the fracture or the osteotomy or what have you is actually paramount to getting the bone stronger in a faster period of time. So external fixation device will oftentimes allow people to weightbear faster. The advantages to external fixation you can use it as provisional or definitive utilization. So there is many times where I have done a fracture. I put on an external fixator and then I am getting ready to go back in for internal fixation and I say, you know what, you are going to be fine with this. I am going to leave it on. I am not happy with their soft tissue or the blood flow or their compliance or what have you. You know I don't want to make a bad situation worse. Let's just leave it as it is and people heal. This is a first line of defense, but is also a final line of defense for any treatment. There is less damage to the bone and blood supply because you are not making larger incisions and again as long as you respect that radius of the size of the wire, there is minimal blood supply damage to the bone. Fracture reduction and stabilization in the acute setting. Obviously, we know this complicated highly comminuted soft tissue window paramount fractures, you don't want to go and make an incision in and then risk a wound dehiscence or late infection or what have you. So in some cases external fixation devices can be used to allow that soft tissue to kind of calm down. You can use external fixation with nonunion and malunion and even in the case of osteomyelitis. There is such a thing as a septic fusion. So septic fusions can be obtained and they are stable fusion. But obviously, you can't take a screw and run a screw up through osteomyelitis or what have you because all you are doing is pushing the osteomyelitis up the leg.


    In the case where you can use external fixation device, you can get a nice fusion. You can actually compliment your antibiotics by blood supply from the two bones that you are fusing coming from both their endosteal blood supply and hopefully cure the osteomyelitis even if it's a nonunion or malunion to begin with. And then of course, there is a limb deformity correction. You can use with arthrodesis, supramalleolar osteotomies, hexapod systems, some of the stuff we will get into. So patient has to know what he or she is signing up for obviously. Three months, that's the timeframe that I usually tell any patient they are going to be in external fixator. They have to understand their activities. Some people hate the idea of being in external fixator. They get cage rage. They would much rather be in a cast but guess what, casts are not a panacea either. They can't shower, they can't weightbear. They are hot in the summer time. So I usually tell my patients that it's like an ear piercing. You know it's painful for the first 7 to 10 days and then after that your body kind of gets used to it and it's just like an ear piercing. It's just kind of there. You can wash it, you will be able to weightbear at some point and by and large, if that doesn't work, then this is when we get into our anxiolytics. Obviously, if someone needs to take a small course of Ativan or Valium or what have you to avoid cage rage, cage rage is a real thing. People pick their face, they scratch, they, you know, the most calm people, once they have an external fixator on, become a different person. Bone biology, external fixation assists with the bone's innate processes. Load sharing will help accelerate or modeling. So external fixation can be placed on the tension side of the bone as opposed to compression side of bone just like metatarsal fracture.


    Fixation principles, external fixation can be used for compression like in the setting of a fusion, neutralization like in the setting of a fracture or distraction if you are doing callotasis or if you are doing arthrodiastasis. I have injected off-labeled Hyalgan or Supartz into an ankle with an arthrodiastasis as well and people do pretty well. Soft tissue safe zones, number one paramount thing that you take home today is avoid the soft tissue structures that are paralyzed. Second thing is after you drill your pins through, hammer, hammer, hammer, don't continue to drill. You have to know the safe zone. One of the other things with the safe zones are paralytics. If you are using the paralysis type anesthesia, we have to be cognizant that people are not going to react when you tickle their nerves or what have you. So if someone is just under regular general anesthesia as that pin goes through and you just kind of brush by the tibial nerve, it will move out of the way and the person will spasm and you will know that that's not where the pin should be. But if they are under succinylcholine or another paralytic or you are doing a pop locker or what have you, they won't have that ability to respond. I recently defended a case on the west coast of someone who does a lot of external fixator and just happen to bag a nerve and the person was in excruciating pain. It was a big deal. So watch the safe zones and as you pass through your pin, make sure you hammer the pin through as it's through bone. Don't wrap up the soft tissues and document so. Middle zone of the tibia, the red line is the bad idea. So if you plough through here, you are going to hit this neurovascular bundle. Ideally, you are going to cross any pin at 90 degree construct but if you have to get less than 90 degrees or greater than 90 degrees to accept the soft tissue that you are working with, then certainly I would rather have a little bit less stability and more safeness with the internal structures.


    As we go farther down the tibia, the safe zones become bigger because there is greater anatomy in smaller surface area. So we have to be cognizant again of straight anteriorly and straight medially and cheat kind of anteromedial and posteromedial for any of your wires. With that said, these are half pins that these are depicting. Skinny wires are not necessarily half as scary to use but can cause some damage. I tried to stay away from half pins because if you ever want to get the patient a tibial fracture, all you got to do is let them fall with an external fixator. That half pin becomes a cantilever and it just cracks the tibia right open. So I will try to avoid half pins whenever possible. Two crossing K-wires is more stable than one half pin and more rigid. In the calcaneus, I usually do the rule of three. Residence in the room, from the posterior malleolus to the anterior Achilles, you put three fingers. The middle finger is where the nerve goes. So you put your first finger here, last finger there, middle finger is always where that neurovascular runs. So it gives you safe zone of the calcaneus of about this quadrant. I wouldn't even cheat up this high. I would say this little quadrant is where I feel the safest being in the calcaneus because you do have Baxter's nerve that runs, that changes course sometime and there is a branch of the medial posterior tibial nerve that can -- medial aspect of the tibial nerve that can lay in the calcaneus. So really that little triangle is where I would like to stay. Olive and Skinny wires, you attempt to go through as many metatarsals as possible, more metatarsals, more stable more you can do.


    I usually like my patient to be supine with a bump on the ipsilateral hip, something to stop that other leg from falling off. You want to certainly prep all the way up to the knee so that you can adjust for any knee pathology, knee replacements, valgus, genu varum, genu valgum has to all be considered. Wire pin inserted, again avoid the paralytics. You are going to push the wire straight into the bone. Don't even turn anything on. Just use a very sharp wire and push it right to where you believe it should be. Now, you are going to use your wire driver to bully through the bone and then once you see the bone is over, now tap the rest. We used to use alcohol in the operating room to drip it on the pins in the hopes of cutting down bacteria, thermal necrosis. Obviously, there is a fire risk now. So saline is the way to go. But I will even put some gentamicin or bacitracin in my saline to act as the alcohol would have been in prior years. Irrigate while drilling. These pins will oftentimes heat up and create thermal necrosis in the bone of which you are drilling through, so make sure you are using cool saline to stop that from happening. Inserting near a joint is dangerous because as someone walks or what have you, the pins can trampoline and go right into the joint. So if you are going to insert close to a joint, make sure that joint can always go through range of motion without the pin engaging that joint. These are some of the external fixators we are going to talk about. It's the typical Ilizarov frame, hybrid, this is the deltoid frame for your pile-on fracture of your heavy trimalleolar fractures or what have you. This is a mini-rail for metatarsal fracture and in this case it looks like callotasis. And then this is actually the old EBI frame that we used to use for Agility ankle implants way back. So uniplanar of biplanar frame constructs, it's usually a pin-to-bar construct otherwise known as Ganley external fixator.


    Unilateral or bilateral, uniplane but multi-plane is more stable. Problem is a lot of these are very heavy. They pull out of bone. They are very half pin-dependent. So I only use the uniplanar constructs in metatarsal fractures or callotasis at this point. Increase number of rods increases stability, bicortical pin placement so that again it doesn't cantilever out of the bone and you certainly want to make sure that you are dead central in any bone that you put the pins in and you don't cheat medially or laterally for fear of fracture. Half pins embody the radius principle especially with half pin because they are darn wide. Again the diameter of the half pin should be less than a third of the bone diameter to minimize the risk of the fracture. Titanium is actually less stiff than stainless steel and people with stainless steel allergies, we need to be cognizant of but when we can't use the stainless steel, you would rather get cheaper and much more stronger titanium in a bending moment. Clamps, many of these clamps are just user dependent. So the idea here is a lot of guys and women will put one pin here and leave all of these open. Even if you are only using one pin, you want to put like a dummy pin or extra pin that doesn't go through the bone just so you get even compression and the clamp of each external fixator goes down upon the pin. Connecting rods can be steel, aluminum or carbon fiber. Obviously, carbon fibers are your generation's way to go because they are radiolucent. You can take C-arm through, you can see with the fracture is doing, you can adjust if you don't like the length or position. If you use one of these big guys here, you are not going to see too much other than that particular connecting rod. Unilateral frame construct is a couple -- this is a kind of smaller slide I guess for you guys to see but certainly you will have this to review.


    First of all, you want to make sure that your pin sites are well aligned. These two are farther away and these are their design perfect, they are separated perfectly and these are too close to one another and two far from the fracture. Second thing is with any external fixator, the closer to the bone that you get, the more stable it is. So here you can see the pins are very far apart and here they are much closer. You want to increase the number of connecting rods. So in other words, this is good but this is better. The idea of having two connecting rods really stops the [indecipherable] [00:16:33] in neutralization. The diameter of the pins is important up to a point. Again, if you can pass two Skinny wires at 90 degrees, that's stronger than half pin and one half pin and of course, multi-planar fixation whenever you could do so. Biplanar or multi-planar frame constructs are more stable because you are in multiple planes. You are capturing the transverse, sagittal and frontal plane as opposed to just one plane with the monoplane or uniplane. [00:17:01] [indecipherable] spanning constructs, the delta frame is an important one to us in foot and ankle surgeons. You are comfortable with it if you are plan on doing fractures. Called delta obviously because it makes this triangle, the Greek letter Delta. We usually do drop another piece off of it into the second metatarsal or medial cuneiform to stop rotational stability. What's important here is this tibia is capable of losing 700 mL of blood with the fracture. So if you have a pile-on fracture or very heavily comminuted ankle fracture, posterior mal, medial mal and fibula, fibula can lose about 75 mL of blood but the tibia is 750 mL of blood. All that 750 mL of blood rushes out into the soft tissues and can really compromise that window. So delta frame is your friend in keeping the fracture out to length, stopping the contraction of the muscles and allowing that 750 mL of blood to be reabsorbed as time goes on.


    Plus it's quite easy application, okay? This is not a super complicated frame. It's something that you are usually doing at 2:00 o'clock in the morning. When someone comes in, they may have an open fracture or what have you. It's get it on and get out of there and let the body kind of do it's thing for a week until you can do definitive treatment later. One other thing is you want to always manipulate the calcaneal pin. So in this example, these two stay loose and everything distal stays rigid so that when I grab my distal pins and I toggle my calcaneus and my fracture back into position, once I like it on C-arm, it's where the radiolucent pins come in. Now you have someone tighten the proximal aspect so the construct is stable and there is no evidence of motion. Mini-rail constructs, again for residence, this will be on every board exam you take. For brachymetatarsia or any callotasis, you usually let the external fixator stay in place for about 10 days, then quarter turn a day or one turn a day which corresponds to about millimeter of distraction in a day and then you leave it in place for 7 to 10 days of latency prior to turning and then afterwards you leave the external fixator in place doubly as long as it took you to distract. So if you distract it for 10 days, 10 mm you are going to leave that external fixator in place for 20 days. That will be a board question for ever, ever and ever. Pin-to-bar constructs, for mini-rails, I am using a metatarsal fracture and callotasis almost solely. I have used them for somebody with a failed Lapidus that has gotten osteomyelitic or hardware that has to come out or what you have and in those cases a few and far between but they are very comfortable. So even novice external fixator user input these in. Most important thing, my kind of take-home tip for you is always draw straight line and then filling the dots in between. So in other words, you go to the most distal pin, put your pin in.


    Then you go to the most proximal pin, put your pin in and then everything between those two are lined up. So some people will start external fixation, will will put this one and this one and then go back to this one and find they are off the metatarsal. So always draw the two farthest points and work your way inward is my little take-home. Ring fixators or Ilizarov fixator, this is -- they resist axial and bending deformation and they allow for compression distraction of the ankle, rear foot and midfoot as well as eccentric wire compression. So this is what I probably have the most use out of because what I can do is I can take bones in acute Charcot or fracture and I can use these little wires to kind of toggle the positions back -- the bones back into position. Elements are the rings, the ring should allow about 2 to 3 cm of swelling more so posteriorly. So what I usually do is I take my two fingers and I say do I have two fingers of ring around that ankle and then posteriorly I look for three and the purpose is that that person is going to be laying with their foot down, toes kind of up to the sky, heel flat in the supine position for hours and days on end. When they swell, they are going to swell posteriorly. Olive wires are wires with little ball at the end of them. They will allow you to probe and toggle fracture pieces into place. Skinny wires don’t have the Olive but same principle. Just olive wires, you can get into trouble with because they will actually break through bone if the bone is too soft. So when it comes to tension, and you don't want to tension in the Olive wires, nearly as tight as you can the Skinny wires. Again, this is a typical tensioning device, something you will be asked on your boards. Tensioning to 120 to 130 kg in the tibia, 90 in the rear foot, 50 in the forefoot. If the bone is softer, scale that down a little bit. So I usually hit the tibia to about 110, 90 is little high.


    I am usually at about 70 in the rear foot and about 45 to 50 in the forefoot. If you go beyond to 155 kg, you will call a stretching formation, which is not good for anybody. It makes the wires just break on this with a teardrop. Bent wire techniques, there are two bent wire techniques that you should be very comfortable with. One is called Russianing when the tensioner does not grab the wire adequately as you don't have enough wire, the other one is walking wires. So wires can be used in compression in that you can bend the arch into the direction of compression or you can walk the wires away and distract as well and we will see some examples of that. There must be asymmetry in the plane of loading that eliminates the toggle effect. Half pins are more rigid but two crossing pins will stop a little trampolining. And again in some cases, you don't mind trampolining like in the tibia because you want a little bending moment for fear that if you have too much rigid fixation in the tibia and someone steps or twists awkwardly, they can crack the tibia and then you get a bigger problem. So that's my wire versus half pin - Skinny wire versus half pin spiel. Static frames are used for Charcot stabilization. They are used for some fusions like triple arthrodesis where you can walk the wire, bend the wire. Struts are the newer way. I have actually even seen some companies where their struts make the frame stronger even if you are not using extension or compression than the static frame because of the size of the actual carbon strut. So the problem with struts is while they make it a lot easier to put a frame on, in actuality each strut is anywhere from $1000 to $2000, so increases the price of the frame dramatically. Usually, use four at a minimum, sometimes up to six depending on if it's a hexapod or what have you.


    So hexapod fixators. These are nice because you can put them on any which way you like. This is actually Stryker's version of the Taylor Spatial Frame but the idea is you can put these on in varus and valgus and then there is a nice computer system as well, which will make it simple stupid so you can take a CT scan and you can send it to an engineer and you and the engineer can design which strut needs to be turned at which particular time. Now, some of these companies have even come out with a wrench where the wrench will touch a certain bolt. It will be green if that should be turned. It will be red if should not be turned and then the patient goes to the next one and they will tell right on the wrench how many times it should turn. This is like your next generation stuff. You can see where this is going. People are going to have app soon. This is what makes medicine so exciting as your generation is going to advance all this way past mine. Ilizarov versus TSF. Taylor Spatial Frame was the first kind of hexapodish idea basically showing in all of the studies that the TSF has a lower complication rate with deformity correction because this is much more patient compliance and the stresses are much better with the TSF than they are on the Ilizarov frame. Hybrid frames mostly used for tibial plateau. I include this only because in some states you know mid shaft fractures are not so out of the game. Postoperative course, again consider dynamization, consider walking this patient if it's a fracture. For the Charcot, it's lot less likely to let them walk. They walk anyways most of the time because they are big boys and big girls but it's not desirable because the bone is too soft. The dynamization of cyclical loading will make the bone stronger. You want to determine your weightbearing status based on the length that the patient is in the fixator and be willing to offer some support for the patient. They are going to want to tell you about yourself when you put this cage on them.


    Try to work with them. Don't get so defensive or blow them off. This is an emotional support time for these three months. Pin-tract infection, be very comfortable with pin-tract infections because there is a 1% pin-tract infection for the pin that you put in. Average frame has 14 pin sites, average frame has 14% incidence of infection. Pin-tract infection can be as simple as patient goes on Keflex or Bactrim for a little while, it can be as bad as osteomyelitis and a lot of these are dependent on your technique. Thermal necrosis, hammering the pins and good prep prior use of bio patches, things like that. How do I treat the pin-tract infection, parenteral or oral antibiotics culturing, just like you would treat any other infection. If need be, don't be afraid to take that patient back to the operating room, cut the pin and take out that pin, put a new one in. There is a CPT code for it. It's totally kosher. It's not a failure. Didn't do anything wrong and when you put your pins in, be very cognizant that you are avoiding your muscular structure. Alright. We are going to skip some of this stuff because I want to get in the good stuff, alright? Let's talk about some ways that you can use external fixation. This is a lady with Charcot, got about 45 degree angle. You can see she has a blown away talar tear. What I did was I put an external fixator on to get the soft tissues back under the ankle. Why? Not because I am ever going to use that talus again but because the medial structures are going to be a fit for me to fix anything unless I relax them. Here you can see my four struts. Alright, getting the ankle back under the foot -- back under the ankle. We are going to let this sit and cook for about a month to six weeks. Now, I am going to take her back to the operating room and I am going to change my struts into radiolucent struts and do an ankle fusion with a nail. Still, I can VAC my incision and there is your nail and your Ex-Fix in position together. This is another person with Charcot.


    You can see that there are just starting to break down in Charcot and start to lose some of the medial structures. All we are going to do is stabilize them. We are just going to put the frame on with Olive wires to hold the midfoot together and we will wait for this Charcot to calm down, which takes about three months. Follow their ESR, CRP. Once they are getting normal again, we can take the Ex-Fix off and convert them to frame or cast. This is someone with actually two places of Charcot. This had a draining wound but it kind of look like Charcot not so much like osteomyelitis because it happened overnight. I took a bone biopsy and certain enough, it was not osteomyelitis, it was Charcot. And then here you can start to see Lisfranc growing -- breaking down. So what I did was use the mini Ex-Fix here to fuse the first MPJ. Would have been a septic fusion if she had osteomyelitis and then Ex-Fix on to bring the medial structures laterally and stabilize this midfoot. She went on to heal. This is a lady who had complete dropping of her talus with dorsal and proximal subluxation of her midfoot. External fixator goes on with bended wire technique to actually get -- this is a big bend wire here to actually get the midfoot back to distract and then this is another lady with medial subluxation of her medial column. We are going to pull her back into position and here you can see this big bend wire holding the forefoot into distraction so I can get the talus back up into alignment. Internal fixation used after the external fixation goes on. This is a lady who had a completely obliterated talus. Talus is resected and again external fixator placed. Everything is negative. All the osteomyelitis is now cultured. No evidence of ongoing osteomyelitis and then this is an antibiotic spacer and now we are going to go back in and use a graft and nail.


    We are running out of time, so I will make it quick. Again, another medial subluxation or Lisfranc joint, Charcot. External fixator, bent wire technique to actually pull the midfoot away. Once I pull the midfoot away, I can actually use my Olive wire to hunk her in, my medial cuneiform back into position and allow the Charcot to come down into that position. She has a rectus foot as well and internal fixation to hold everything together. This is kind of a neat guy and I showed this again because it's a resident's conference. Guy with a scaffolding injury pile-on fracture. I did not fix this but the person who did, did a fantastic job. I mean I don't think I could have done better than the person did. Joint is aligned. Everything is great, looks fantastic except for there is a lot of comminution and the person ended up with a nonunion. So sent to me, looked at the nonunion and basically what you are looking at is from about here to here is all dead bone or osteonecrosis because of the fracture. In this case, what we do is we go to the other leg and we map out that fibula. We team up with the plastic surgeon and then we harvest the fibula with a blood supply to it. So here is the fibula coming out. We have an artery. Now, this fibula we go to the contralateral side and measure the defect of the osteonecrosis which measures about 5 cm. Then what we are going to do now is we are going to bore a hole in the talus and bore a little hole in the tibia here and we are going to take that vascular supply of the fibula and we are just going to dock it right into the tibia, dock it right into the talus. So there is our fibula in place here and then now I am going to put this external fixator on and I am holding the external fixator against my chest here and pulling into compression while the resident here is locking the struts into position.


    Now, we have compressed our anastomotic fibular graft into position locking everything rigidly. Well, the problem is that the fibular graft can still migrate north up the tibia. In order to stop that from happening, we are going to throw a screw into position. Here you can see the screw that locks everything from going up the canal. So what's going to happen is after time, after this artery is sewn in, this begins to hypertrophy and you get a new tibia out of it. Pre-fibular graft or tibia, you can see after time now we are starting to get complete grafting in the tibia. These are some ideas that you can use with external fixation device. The device is, again it is practice, practice and practice and getting your hands on it and I look forward to your generation showing [indecipherable] [00:32:56]. Thank you very much.


    TAPE ENDS - [30:42]