Marie Williams, DPM guides you through the complex world of locking plate technology. Dr Williams discusses the different types of locking plates as well as helps you choose which plate is best for your patients.
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Marie Williams, DPM, DHL
Director, Podiatric Medical Education
Aventura Hospital and Medical Center
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Male Speaker: Okay. Now we have a couple lectures by Dr. Williams.
Dr. Williams: Alright, thank you. We're going to wait until I get my lecture pulled up. I'm going to talk about two lectures. One is about plate fixation and the other is about hemi-implant or implant of the first metatarsal. We'll just move one to the next, okay. We'll try to move the time as well. Here is about the plate fixation. Actually, I wanted to tell that this wasn't an easy lecture to put together because I don't know about anyone else, when you're actually getting or deciding on plates, there's a hundred reps coming into your office everyday. You have to decide what plate you're going to use. Early on, we have like three plates to pick from and we just didn't want it to be too thick or wasn't like a semitubular plate or what was it. Now we have plate after plate after plate, some are prettier in colors, some are thinner, some are thicker, some have locks, some are not locking. I'm going to try to put this in a little bit of a perspective. I don't have any one company that I worked for or use any plates that are more specific than another. What is plate fixation? You want stability across the fracture site and/or the osteotomy site. The primary osteo bone healing is done from primary bone healing as opposed to secondary bone healing. The plate is a neutralizing force and also it is something that can bridge comminuted fractures. That's why you would consider using plates. I mean, I'm talking plates, plates, plates everywhere. It makes you laugh, right? There're so many types. There is calcaneal plates, there is slide plates, there is walking plates, there is nonwalking plates. Here's an example of something that we've used. We used a locking plate with the compression plate, one because of an osteotomy, one because of a fusion in a person who had trauma to the foot and we were getting the whole medial column down to the ground. We just started to use different plates for the different concepts that we were trying to heal. One was for arthrodesis and one was for stabilization of osteotomy that we created. Compression plates, compression from either the plate or the interfragmentary screw, basically the lag technique. Then you have a plate that is used without a lag screw and it has compression, but it may be used through the plate. You'll get the compression through the plate and then if the plate is used with the lag screw then the plate functions to protect the screw against the deforming forces and the compression is not afforded by the plate but by the screw. Here's the locking plate system. Locking plates, you have locking screw threads into the locking plate which create a single uniform construct and the plate does not sit flush on the bone. It eliminates screw toggle and creates a fixed angle single beam construct. When I first put a walking plate, one of the mistakes that I made is we thought we had compression over our osteotomy. I know we put the locking plate on and we did not put the compression and we thought we would get it with the plate. But once you lock the plate, it actually does not compress over the fracture site, so make sure that you have good compression before you put your locking screws in because the plate will then be fixed to the bone and will not achieve compression. It dissipates axial load along the entire plate which is what you may want to do in a comminuted fracture or something where you want to actually dissipate pressure from the osteotomy or fixation or fracture to the plate itself. It's indicated for large metaphyseal-diaphyseal comminution or poor bone stock. With plate function, you have different types of plates, some cause compression, some are for protection. There's others that are buttress, some plates just have a tension banding concept and others are bridging. We'll kind of just review that a little bit. Here, a compression plate is a dynamic compression plate. It has compression from eccentric screw insertion and it has limited contact. You want a plate that has limited contact to the bone because it reduces the surface area, therefore less insult to the periosteal capillary network and there’s an example of a plate that has limited contact. You'll see these plates will be thin, sometimes there’ll be multiple to the bone with less actual thickening which causes some periosteal destruction and less healing in some cases.
This is just an example of that over a fifth metatarsal where you can see where you're going to get good compressive forces across the fracture site with the plate intact. Plate function for protection. You'll see here that you have a lag. They call this a protection plate. It was also called a neutralization plate with lag screw fixation and it is indicated for simple fractures. A neutralization plate protects the screw failure by reducing a bending force or shearing or rotational force. This is most common in that typical lateral ankle where you have a fibular fracture and having interfrag screws, stabilizing the fracture and then the plate neutralizing the compressive forces over that screw. Here's an example of an ankle fracture where you needed a combination of things. We had the neutralization plate with lag screws within the plate itself. Also through that, we had fixed the medial mal with just regular screws. But the plate is definitely a stabilizer as well. There's buttress plates, now with the buttress-type plate, it is usually called the buttress or antiglide plate and most commonly found in the proximal tibia. The buttress plate resist axial load by applying forces at a 90-degree angle or axis to the deforming force and it protects the screw from shearing. That's where this high-impact injuries at the proximal tibia are most indicated. It’s seen at perpendicular aspects to the bone and typically contour to the bone. Tension banding is also important with plate function and here what you'll see is where do you put that plate? What side of the bone do you put that plate and that's what tension banding is about. It converts the tensile force into the compressive forces. You can see here where in the bone there's actually the opposite cortex which provides a buttress support and I think if you've actually seen some of the lectures where the plate was put on the plantar surface of the first metatarsal, that had the concept of a tension band because what it was doing, it was actually converting those tensile forces on the plantar surface which is really where the tension is or lies. The bone must have a secondary eccentric load and it's placed on a tension side, opposite side must withstand compressive forces and the plate must be able to withstand the tensile forces. That is a tension band plate and the way you place it makes a tension banding. If you look at a bridge plate, a bridge plate is really something that bridges comminuted or sparing and comminuted bone and actually any areas that where there's bone supply that have been disruptive. Bridge plates are common with very long, sometimes tibial fractures or comminuted bone where you want to actually use the plate as a long bridge plate which increases the lever arm and distributes the bending forces. Usually, the plate length recommendation is three times the length of the comminuted portion and eight to 10 times of length of a simple fracture portion. When you look at something like that and you see comminuted tibia and you put this long plate on there, that's called the bridging plate on the tibia. Of course, we have the neutralization plate with lag screw fixation on the fibula but an example of bridging is on the tibia. Here's compression plates, now they're come in all sizes and shapes and kinds. This is a very simple compressive plate where you have lock and screws and as you compress the plate to the bone with a little device, you will get compression of our osteotomies. It's good to get compression for arthrodesis. Here's an example of the displacement plate or a slide plate where you're doing a calcaneal slide osteotomy. You may want to fixate with this plate. Now as the plate compression, no. The plate is actually more stabilization of that osteotomy so that you don't get movement but it’s the plate locked to the bone that actually creates or dissipates pressure or forces to the plate itself and away from the bone. This plate is a weightbearing locking and nonlocking plate. Interestingly enough, this is one of the plates on the market that allows you to ambulate a patient who you do a Ludloff type or a base wedge type osteotomy because the screws dorsally are actually compression screws and the screws going from medial to lateral are locking screws.
What that construct does according to the way the plate was made takes all the compressive forces to the plate and away from the fracture site which means that you can ambulate these patients a lot quicker. Of course, in our Miami area, people want to be in their shoes as fast as they can, too hot in a cast, I can go on and on but, this is a just an advantage to that type of plate. It's a locking and unlocking plate in a C-shaped fashion so that you could get compression to the plate and forces to the plate and ambulate the patient. Here's another type, it's not a true plate but acts like a plate and it's a lag screw with what they call an expo system for arthrodesis and you can see this is in place now. The interesting thing about this is that it's a 60-degree angle to your fusion site. The 60-degree angle is a very stable construct for any type of geometric structure and stabilizing. That's how this plate came about in a 60-degree angle. Now Hyer did a study and it's a very limited study. I wanted to tell you that because it's a small case but it was interesting because you never know, are you supposed to use a locking plate? Are you supposed to use a compression plate? Should I use a screw with the plate? Should I not use the screw? I mean there’s all these questions that I mean even I ask that like in the calcaneal fractures and metatarsal fractures and osteotomies. The reps will come to your office and tell you their plates is the best or this is a locking plate, like now it's supposed to be something better. I like this article. I read it and I thought, this is an interesting thing because it's a retrospective comparative study for different fixation techniques. The static and locking plate and also lag screw for first MPJ fusion. He had four criteria. It was a successful fusion. How long did it take to fuse? The days to full weightbearing and the mean followup. Actually, as you look here, you can see the static plate. You have a static plate with lag screw, you have a locking plate and a locking plate with lag screw. Then you would think one might be better than the other but what was significantly important is overall fusion rate was 93%, no matter what plate. No statistical significance between the success fusion, days to fuse or days to weightbearing. The only thing that was actually statically valid was the actual followup days and the followup times was significant because the patients that had the locking plate with the lag screw didn't really come back for followup after four months. Their conclusion was it was likely due to the stable construct of that screw and you can't really tell or extrapolate. I know there's got to be more studies or research if we're really going to compare plate to plate, to plate, to plate. There's very different comparisons but in this little study, it just gives you the idea that it really doesn't make that much of a difference as long as you get compression over your osteotomy or your fracture and you're stabilizing that and treating them appropriately. Some of the complications to using plates is a cortical necrosis. If the plate is indirect contact and pressed down into the bone, you might get necrosis. But if you do minimal stripping of the periosteum, you have less complication of cortical necrosis. You can get infection. You can get painful hardware, nonunions and/or malalignment. You can get similar complications to using plates as you do in any type of surgery so just beware. Here's an example of not only, this was just the complete failure of fixation in a Charcot where the foot falls apart. The plate actually did stay stable but the foot was unstable. This really wasn't a very good result and the patient had to go back for IM nailing. Here's another example where they can break. You think you did a great job, you have nice fixation, you even get good fusion and they come back, and they said “It's painful on the top of my foot.” You take an x-ray and the plate is broken. That’s not uncommon. This is just some complication, you’re going to take it out and everything is fine. Here’s an example of a plate that was a little too thick in a diabetic who was compromised. Now you see the screws and the plate sticking out and when we received this patient, basically they said “There’s nothing we can do.” The orthopedic said, “Well, there’s nothing we can do. We’re going to amputate the leg.” And you’re like, wait a minute, let’s take out the plate, clean up the bone, take care of the wound and this patient should do fine.
There was good healthy granular tissue really and we knew that the there was potential to heal but the point is that in these older plates, they used to be 1/2 tubular plates that are very thick and sometimes in these elderly patients, the plate is very, very much prominent and they breakdown. The patient that is debilitated with the fibular fracture, I tend to use an IM nail in the fibula because I wouldn’t want this type of complication to occur. These are the references that I use. There is so much more out there about types of plates, kinds of plates, whether what’s better locking, and unlocking. I think that if you understand the basics of screws and plates then you can actually use them to your advantage. It’s the idea that it’s not all one plate goes to one fracture or one type of problem and nowadays the technology is so large out there with regard to screws and plates. I went out to a lab once with one company and I spent all day in their lab with their engineers and amazed me. I was amazed by the technology that goes behind making one screw or a simple plate or a plate that has crews that locked and fixed. It’s a lot. We just get them. We’re the carpenters that put it in. But the technology behind them is far greater than you can ever imagine.