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Board Review Diabetic Foot

Offloading the Diabetic Foot - Lessons from the Literature

Lawrence Lavery, , DPM, MPH,

Lawrence Lavery, DPM, MPH reviews and cites research studies that support mechanical and surgical off-loading techniques. Dr Lavery discusses the reasons for success or failure of specific techniques over others and supports his discussion with the literature.

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Goals and Objectives
  1. Review the etiology for foot ulcers
  2. Recognize the evidence for mechanical off-loading
  3. Describe the evidence for surgical off-loading
  4. Discuss clinical outcomes and adverse events
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    Release Date: 03/16/2018 Expiration Date: 12/31/2018

  • Author
  • Lawrence Lavery, , DPM, MPH,

    Professor and Director of Clinical Research
    Department of Plastic Surgery
    University of Texas
    Southwestern Medical Center - Dallas, TX

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  • Lecture Transcript
  • Male Speaker: One of the basics is offloading and I think sometimes, we don’t pay enough attention offloading and more attention to advanced therapy. I’d really like to focus on offloading as a key component in your management of diabetic foot ulcers, I’ve asked Larry Lavery who has a good deal of experience in this regard to speak about offloading the diabetic foot and giving us lessons from literature that support exactly why it’s so important to do. Let’s welcome back Larry Lavery.

    [Applause]

    Larry Lavery: There you go. Thank you. I’m going to spend just a slide probably talking about the etiology of diabetic foot ulcers. I’m still surprised that the people that missed this and certainly this is not the traditional group that I speak to. I’m going to talk about the, most of my time, about the evidence from mechanical offloading to heal foot ulcers and then I’m going to spend a few slides talking about surgical offloading and some of the evidence in that area because I think that’s a growing area that we’re going to have impact. This is a meta analysis from Dave Margolis which is a fabulous way to start this discussion I think. Dave looked at the control arms of phase three clinical studies and diabetic foot ulcer healing at 12 weeks and 20 weeks. If you look at this and if this is what is standard of care, it’s horrible. The bar is low. It gives us a lot of opportunities for improvement. The problem is the two offloading, main offloading devices that were used in these three studies were either healing sandals or therapeutic shoes and insoles. I’ll show with some other randomized clinical studies that when you use these devices, this is what other people report as well. You get a 20 to 30% wound healing in 12 or 20 weeks when you use therapeutic shoes and healing sandals. One of these was the dermograph study. When the dermograph study was presented at the ADA in 1998 in Chicago, it’s usually a very pleasant group. But there are couple of people that really got their fur up and were telling the people from dermograph that there study was horrible because they didn’t use more aggressive offloading. This is the community standard though. What they did was not horrible care. It’s what the vast majority of people with diabetic foot ulcers get because either insurance doesn’t pay for something more aggressive like removable cast boot or people taking care of that patient aren’t comfortable using something more aggressive with stronger evidence like a total contact cast. In real life, this is 90%of how people are treated in the world. We started a long time ago looking for alternatives and we started in the Gait Lab [Phonetic] to see the relative effectiveness of pressure reduction with total contact cast and other removable cast boots We subsequently expanded this and looked at postop shoes and healing sandals and felted foam dressings to see how they all compared. We were looking 20 years ago to see if there was something that was as good as a total contact cast that we could use that would be easy in clinic that a high school educated cast tech could apply that would be fast and patients would accept it. At that time, there was only one product on the market that was specifically designed for diabetic foot ulcers and it was the DH Pressure Relief Walker which was designed by a podiatrist. Since then, that company has changed hands three or four times. The products still looks very similar several companies have looked at that design and copied it, if you will. And so now there are more products that probably are similar to this. If you look at this data from 1996, the Aircast fracture walker was a closed third and then the 3D Dura-stepper which I don’t think exist in that form and then the CAM walker was the last and the least. EXDS on here or extra depth shoes and CVO is a campus oxford shoes so we could measure walking. A lot of studies now use a DH walker. A lot of the phase three clinical trials because of some of these early data. If you’re going to use the shoe, you’re going to have 50% more pressure on the foot. If would look at the old, the fancy technology, bioengineered tissue or platelet-derived growth factor, about 50% of people are going to heal in 12 weeks.

    [05:10]

    It’s not especially compelling. The average healing time ranges from 65 to 86 days. It takes people on average, two or three months to heal. Not fabulous. All of these factors, again, we talked about this morning, I think offloading is pivotal. You can knock down the bioburden, you can debride the wound adequately, you can put all kinds of fancy growth factors on the wound bed. If you don’t offload the foot, it’s not going to work. Thoreau said, “For every thousand hacking at the leaves of evil, there’s one striking at the root.” The roots of evil, no pun intended, are biomechanics. It’s the biomechanics of how the foot functions and why people get foot ulcers. Often, when we get residents and students and they’re on a clinic and someone has an ulcer at face, so why did you get that ulcer. The next day, Willy [Phonetic] has neuropathy. Why did he get that ulcer on his big toe or on his fourth metatarsal head or. It’s like they’re stuck. I think the huge advantage we have in is we understand mechanics and how to change mechanics or improve mechanics. This is one of my favorite slides of a nice cut through a normal foot and someone that has diabetes, obviously, they have Charcot in their midfoot. My little pointer is kind of weak. They’re similar to this slide, Sue [Phonetic] had showed they have a dislocated metatarsophalangeal joint and everyone says, “Well this guy doesn’t have a fat pad.” He does. It’s just in the sulcus now instead of under the bulb of his foot. Because of the mechanics of this foot, this is a picture from the Gait Lab, because of the mechanics of his foot, this guy has a huge spike where his metatarsophalangeal joint is dislocated and he ulcerates, we can heal them and they always re-ulcerates. I’ll go back to exactly what Sue Hud [phonetic] said, what’s the best strategy offloading the diabetic foot? You might guess from looking at Albert Einstein. It’s all relative. Meaning, there are bunch of factors that we need to understand. The patient’s postural stability, we have a lot of patients that have severe neuropathy, they’re obese, they have limited joint mobility, they have joint implants, they have poor vision. And if you look at any of the criteria for fall risk, they have everything. You can’t lock up their ankle and limit their ability to adopt because they fall probably on a regular basis with the lights out anyway. You have to go to some compromised position. There are economic reasons, there are living conditions. I have patients who have to walk up four flights of stairs and they can barely make it. And if you put a cast on them they’ll never make it. A lot of the adherence and social factors come into your decision making. I have people, they drive, you can’t put a cast on the right foot, and they’ll say, “I’ll just drive with my left foot.” It’s like “Yeah, we’re going to do something else.” Offloading to heal diabetic foot ulcers is probably the most studied treatment for DFU. These are a number of cohort studies reported by podiatrist, physical therapist, physiatrist, and orthopedic foot and ankle surgeons. The results are very similar. The 75% to 100% of wound heal in about six weeks, the same data we’re going to see when we look at randomized clinical studies. This is a survey from Stephanie Wu who is at the Schull College that asked people what they used for offloading. Two or 3% percent use total contact cast, so it’s a tremendous minority. A little more than 10% use removable cast boots, but most people get to use insoles because that’s what Medicare pays for, and that’s what they can get. Even though people at meetings like this, at the ADA, the American College of Foot and Ankle Surgeons say that the gold standard is a total contact cast, it’s an ideal gold standard. I think that we can use it more. One of the interesting things is I think a lot of people get this wrong, I mean, you can still get the classic total contact cast video from the Hansen Disease Center in Carville, Louisiana. It’s a minimally padded technique so this is the amount of padding people get. You roll plaster first, you mold it in well, and then if you can you put a cast shoe or a heel [indecipherable] [09:47]. It has a couple of tremendous advantages. If your patient has to get up 15 times in the middle of the night to pee, his foot is protected. If he thinks he’s safe at home and he can take off his boot or he can’t with a cast.

    [10:01]

    I think one of the underlying reasons besides taking pressure off the foot is it changes your mechanics, it decreases your stride length, it reduces your cadence, it substantially reduces your activity. It certainly changes your pressure on your foot, it probably changes sheer forces because you can’t be propulsive, and it allows patients to still walk and do a lot of activities of daily living. This is a hard sell in July in Dallas, Texas when it’s a hundred degrees, but we have 30 people at any time in our clinic that are in total contact cast. Many of them are repeat patients, just as Sue Hud said, and they will not go back in anything other than a cast because they know how fast it works and they know they failed another modalities. There are some bad things, it’s heavy, it’s hot, you’ll beat the hell out of whoever you sleep with, it’s difficult to bathe. I tell patients, “If you came in and you fractured your ankle, you would have no thought that you would leave in your shoes.” As a matter of fact you’re going to sue if I said, “You know, you have a trimalleolar fracture, I’m going to get you some extra rubber shoes, go with God.” But the same thing for a cast, the risk of losing their leg is much, much, much higher from their 2-centimeter foot ulcer than it would be if they fractured their leg, probably not if they left in their shoes. But that’s the context I give for patients and their family. There are some relative contraindications, infection, vascular disease and instability. I put people in cast for all of these reasons depending on their social support and their severity. There are certainly complications. The gentleman in your left, I inherited from one of the orthopedic surgeons that was a residency maid of mine, and he got a cast, he had peripheral vascular disease. He ends up losing his leg. There are some people that you have to modify your results. There’s now a growing body of evidence. A lot of it from Europe about using total contact cast. The Italians are early adopters and have done some great research in this area. These are some of the randomized clinical studies in this area. I’m going to talk about just a couple of them. The first is from Mike Miller’s [Phonetic] group at Wash U. If you want to read a good body work, pull up his group’s lecture, they do fantastic work. All of these studies are small studies. There’s 20 patients in each treatment arm. The results are very similar, we are just finishing, actually, we just finished the last visit for a large randomized clinical study that’s sponsored by NIH where we enrolled 245 people and randomized them in three offloading treatment arms. Our results are a little bit different. One of the things you’ll see from all these studies is people -- none of these people have adverse events or they’re not important. Mike Miller’s group says, three people in the traditional shoe group got infections. Everyone else has no complications, but if you look at this, the people in the cast group, 90% healed in 12 weeks, on average it was 42 days, no infection, and then the shoe group, just like the other studies, 30% healed, 65 days average time to heal for those who healed, three people had infections. This was a randomized clinical study that was funded by a DA merit award when Dave Armstrong and I were at UT in San Antonio. The sample size was supposed to be 225 people. Dave, I laughed and went to work for disease management group, Dave took over the study, 63 people were randomized. The removal cast boot, a half shoe or a total contact cast. The DH pressure relief lock or the Aircast boot was used. In this study with these three modalities, there is a significant difference in healing and offloading, 90% of the people in total contact cast field, just like Mike Miller’s group, 65 in the removable cast boot, 58 in the half shoe group. We looked at activity in that group, at this time there were, computerized activity monitors were just being commercially available. They are like $500 a piece, so we were able to use some of those. People in the total contact cast took significantly fewer steps than people that were in the half shoe. Six hundred steps compared to 1400 steps. The durability around the need is very high in both of these groups. Two hundred forty percent more steps in the half shoe, there wasn’t a difference in TCC in removable cast boot, 128% more but not a significant difference. We looked at this then said the DH Walker, the Aircast boot was about the same as the total contact cast in the Gait Lab. Why is it different? We looked at activity monitoring, the people were on their ways which is what they did in this first study because we couldn’t afford multiple activity monitors per patient, and we duct taped one on their boot and we ask them to wear it.

    [15:02]

    This is someone’s activity on their hip and then this is their activity when we look at their activity on their boot. When we ask patients if they were compliant, they would say “yes” that they were, they were all the time. And then when we show them this data and said, “Well, it looks like at 3:00 in the afternoon everyday, you keep on going but your boot doesn’t.” And they would say, “Well, I get home at 3:00 and I take this boot off. I had a carpet, it’s soft, I’m safe.” It’s either an error on our part, which is what one of the things Sue Hud was saying, that we didn’t educate our patients well enough. They didn’t know the importance of this or their interpretation of offloading is different. Then we look at activity with people’s boots on and with their boots off, the majority of their steps were taken inside their house where the boot off where they were safe. We have to do more to help people understand how important this is if they have a product that they can remove. The idea of an instant total contact cast where you take removable cast boot and you put something on it so patients can’t easily take it off was attempted. There were two studies, one at the University of Miami by Andrew Bolton’s group at that time and one by Alberto Piaggesi in Italy. They both had very similar results where there wasn’t any difference in the total contact cast and instant total contact cast and the time to healing. This is the cast study, this is Piaggesi’s study or the proportion of people that healed. No difference in those two groups. Maybe we have something easy that anyone in their clinic can fit and wrap $75 Coban around and they will leave it alone. Subsequently the NIH study that we’re doing has a similar premise except we have like little ski, like the things that you see on cops where, except it looks like a ski boot. You snap it so it looks nice. It doesn’t look like they just bought their boot in a garage sale, but they can’t open it up. It’s a little more elegant look. This is something to add from the last time we looked at this data. This is not up to date with probably the last 25 subjects. But if you look at the study where we offloaded 245 people, these are the people, these are not 245 obviously. But with an intent to treat analysis there’s a huge difference, this is a 20-week study, in the total contact cast group, 67% healed, 42 in the removable cast boot and 41 in the instant total contact cast, because of adverse events and people dropping out. If you look at intent to treat the percent healing is much different than if you look at people that drop out. Most of the studies in this area don’t report dropouts and so they are really good at retaining people or they’re looking at a per protocol analysis. If we did the per protocol analysis it would probably be 90% in the total contact cast group. Adverse events are common in this group. The adverse events reported here are just study-related adverse events. People can have multiple adverse events during the 20-week treatment period. On average, over 65% adverse events reported. If you capture all comings, “I have the flu, I had chest pain, I went to the emergency room for diarrhea.” These are sick people, they had a lot of bad things going on, a lot of changes in the medical status. Their study-related adverse events are not that high and actually lower than if you look at study-related adverse events and phase three clinical trials that are 20% or 30%. The voluntary drops are what kills you for an intent to treat analysis. To summarize, if you look at this, if someone is just use therapy [indecipherable] [19:16] there’s going to be a 12% to 20% pressure reduction, they’re going to take about 1500 steps a day and 20% are going to heal in 12 weeks. If you put them in a removable cast boot, you’re going to reduce their pressure by 72% to 85%. They’re going to take 700, 800 steps a day and 65%, and actually with our data, 40% to 65% are going to heal in 12 weeks. If you look at a total contact cast population, you’re going to take 79%, 85% of pressure on average off the ulcer site. They’re going to take many fewer steps, they’re going to take 600 steps a day, and 70% to 90% of those people are going to be healed in 12 weeks if you look all comers.

    [20:00]

    There are obviously other ways to skin this cat, so this is a very busy table, but if you look at this and you look at the proportion of people that heal, it’s high. But the difference is these are mostly cohort studies, they’re not randomized clinical studies that we look and heal, healing for 12 or 20 weeks. These are people that are looking at healing until they heal or something bad happens, the average of healing time is much, much longer, 300 days for the custom splints. You can use alternative offloading and people will heal. Their healing time is going to be much longer and if you really honestly look at adverse events, their adverse events are going to be much higher because the incidents of infection and amputation increase the longer someone has a wound. Probably, the best work in this area that looks at real-life comparative workers from Jim Burke. Jim, he is a PhD physical therapist, he used to be at Carville and is now at LSU. When he retired he took a bunch of the people that worked at Carville, moved to Baton Rouge. They looked at a retrospective study of 120 consecutive patients, the biggest cohort study in this area. And they wanted to compare total contact cast to alternative offloading, walking splints, accommodative padding, and healing shoes. Now this is a group of people that live and breathe offloading, they do this extremely well, they have labs, they have materials, they have facility, they have, probably the most important, they have passion. Only 7 of 120 patients did not heal, 6%. That’s the best in the literature. I mean, no one has such a low healing rate. After adjusting for width and depth and duration of ulcer, there was no difference in healing based on their offloading modality from Jim’s study. I believe his work. I mean he has no bone to pick in this. A little bit about surgical offloading. There’s a couple of things in the literature, Keller arthroplasty, flexor tendon releases, Achilles tendon lengthening, but I think all need to be considered in our toolbox. I think that Keller is a great procedure for people that have IP joint ulcers. Because our ability to measure perfusion is so poor I usually like to do this in people that have healed and have reulcerated even when we do our best. I have some indication they’re going to heal on elective procedure on their foot. There are a couple of nice papers in this area. This is a study from Dave Armstrong when we were both at the VA. Look at a cohort of VA patients, they’re old, they’re 70-year-old people that had diabetes for a long time. Their glucose control is just okay, their ulcers have been around for 15 or 16 weeks. After they had their Keller compared to the control group, they healed faster and I think more importantly, and I think what’s interesting I think to do this study is their reulceration, their recidivism is much lower. And it’s much lower in almost every study that looks at elective surgery to heal these. A couple of years ago, percutaneous Achilles tendon lengthening was all the rage. Some people reported some high adverse events and negative results and I think a lot of people have abandoned this. I think we just changed our approach. This is a study that was published in JBJS [phonetic] looking at pre-imposed partial measurements, about 27% change in four-foot pressures when Achilles tendon is lengthened. With a relatively small increase in ankle joint motion, about a 9-degree ankle joint motion, if you look at the studies where people have healed ulcers, their ankle joint motion goes from 0 to 15 or 0 to 20 degrees. So these are folks, less is more, I mean you want to heal their ulcer, you don’t want to give them what you consider normal ankle joint motion because they’ll get heel ulcers. You guys all know the three-incision approach, most of these we use in people that had transmetatarsal amputations and had equinus during their healing. This is a study that is only randomized study in surgery in the diabetic foot, from Mike Miller’s group. Great work, they randomized people’s total contact cast, 31 people that had Achilles tendon lengthening and then were casted. A 100% of people healed when they had their Achilles tendon lengthen, 88% in total contact cast, very similar to the rest of the literature in this area. The average healing was 41 days compared to 58 days. The average ankle joint motion at followup was essentially neutral position compared to 15 degrees at baseline. The big negative is 13% of people developed heel ulcers.

    [25:01]

    The only thing worse than a nonhealing foot ulcer is for you to make a heel ulcer I think. But the great part of this, the compelling part of this is the recidivism, the recurrence rate is much lower. At seven months, in 24 months it’s 15% and 38%. That’s pretty good, that’s good compared to everything else in the literature, and it’s 59% and 81% in the total contact cast group. Now this group, Mike has done previous work that’s been NIH-funded looking at offloading after amputation. Their lab has a focus on shoes and insoles and prevention as well. They didn’t just get thrown back into the pond with bad treatment results. To summarize, if you look at what’s effective for diabetic foot ulcer healing, it’s the bread and butter stuff that we do. It’s offloading, is going to heal 80% or 90% of your ulcers in six weeks and other more expensive modalities are going to heal half the people in 70 days. I think this is pivotal. It’s part of the mechanics that I think is the strength of our profession. Obviously, offloading has to be selected based on the patient population and their needs, but I think you need to start aggressively with your initial treatment choice and discussion of the patients. I don’t have a lot of kickback telling people that they should be in a cast because I frame it first. With a few of my brother, I would put you in a cast. Second, if you had an ankle fracture you would expect to be immobilized and you need to be immobilized for this, and people appreciate that. And I think you have to modify your offloading based on their response. Thank you.