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Hi, this is Dr. David Armstrong, and it is a privilege to be speaking with you today about a topic that I believe is very germane as we move forward into improving our overall care of diabetic foot wounds that is specifically the appropriate use of negative pressure wound therapy in the treatment of this wound type.



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I think we are all intermittently aware of the problem of the infected diabetic foot. We know that the most common reason with our patient with diabetes who live in the hospital is not for DKA or MI or a CVA or an HAV or whatever letters we want to string together, it is for an infected hole in the foot that encompasses at least a quarter of all diabetes-related hospital admissions in United States, perhaps even more in parts of the developed world outside of the United States, and even more than that in the developing world outside of the United States. We also understand that as even for patients admitted to the hospital with the diabetes-related complication, those patients are evaluated shall we say euphemistically rather poorly very frequently, and this is not because there are somehow conditions which are simply are inadequate in taking care of the diabetic foot. It is merely because that in most parts of the country and most parts of the world, there are not dedicated teams taking care of this problem, and it certainly does take a team to manage these diabetic foot complications.



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Following along with that, we see the dismal results following that first lower extremity amputation. These data have not changed in well over 40 years. After that first amputation, over about 7 of 10 of these patients will have the other leg off within 5 years. Generally, at least half will be dead in 3 years. This is worse than most high-grade carcinomas in terms of the life expectancy. We understand also from some work that my friend Larry Lagrey and I did in South Texas about 10 years ago was that only 2% of patients receiving their lower extremity amputation are admitted from a long-term care facility like nursing home, over quarter of them are discharged after that amputation. So, this is the one thing that takes patients from being ambulatory, productive members of the society, and put some really forever on the dole, and we wonder why now this is a problem that costs in the billions of dollars and I would say that this only the scratching the surface. We know that there are at least 100,000 diabetes-related amputations per year. This encompasses probably about 2600 bed-years/annum, and at the cost of $30-100K per amputation. All we need to do is to do the math and we see the problem and the scope of the significant public health malady.



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Of those data previously warned enough to convince us, if we look at it in slightly other way and perhaps look at the most significant diabetes related complications, we see that the story continues. We know that foot ulcers are the most prevalent severe complications of diabetes occurring from some work that we did again about a year ago at about 68 per 1000 patients with diabetes per year. This is about as common as impotence as we do sort of metanalysis of the survey of the literature. It is more common than diabetic foot infection obviously because about probably 99% of diabetic foot infection start out as diabetic foot ulcers from again based on work that we and others had performed in the past. Amputations are slightly less common but a significant public health problem. End-stage renal disease and blindness, two very feared complications, are significantly less common then amputation infections and foot ulcers. But the figure that I want to highlight is if look at these data we see that the infection to ulcer ratio is rather frightening in the even at centers that are very judicious and have a used antibiotics. In the average lifecycle of the wound, there is about a 56% chance that the patient with diabetes is going to require antibiotics and that leads often to an inpatient stay that drives up cost and drives down the quality of life and drives up risk for amputation.

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The reason that we are together today is not just to talk about the diabetic foot, is to talk about a rather small aspect of diabetic foot and that is the treatment of diabetic foot wounds and specifically a smaller aspect of that treatment of diabetic foot wounds using a certain technology that in this case being negative pressure wound therapy and hopefully the goals of our time together will be to give us all a slightly better idea where and how we could use negative pressure therapy effectively in the treatment of the diabetic foot.



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Before we can begin discussing any type of specific therapy, it is important to know the terminology and there are a number of commonly used terms to describe negative pressure wound therapy. Perhaps the most common being VAC therapy which refers to the most prevalently used device to deliver negative pressure wound therapy. Also, vacuum-assisted closure is frequently used. Negative pressure wound therapy is the sort of generic version or the generic term use to describe this type of therapy in United States, particularly in the North America. A subatmospheric pressure is often seen in the slightly older literature describing this type of therapy. And if we move over to Europe and other parts of the world, topical negative pressure is commonly used there, particularly in the European plastic surgery and wound healing literature. So those are the terms and they can be used interchangeably depending on where in the world where you are or what specific aspect you are talking about. For our purposes, we are going to be discussing this type of therapy and referring to it as a negative pressure wound therapy or perhaps a shorthand vacuum therapy.



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Now if we try to define negative pressure wound therapy or VAC therapy, we can do so by saying that it is the controlled application of subatmospheric pressure to a wound using an electrical pump. It is used to intermittently or continuously convey subatmospheric pressure to a specialized wound dressing which includes a open-cell foam surface dressing. This is sealed with an occlusive dressing which we will see in moment that it is meant to contain the subatmospheric pressure at the wound site and thereby periodically promote wound healing. Drainage from the wound is collected in a canister which we will also see momentarily.



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Now let us look at the few different VAC devices. This is the original VAC device often known now as the VAC Classic.



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This is the replacement model in many parts of the world for the VAC Classic known at the VAC ATS. It has the number of improvements, both in the method of application of negative pressure wound therapy, the speed at which the pressure can ramp up, also the size, and robust nature of the collection canister.



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This is the mini-model of VAC ATS. If you will, this is known as the VAC Freedom and this device is commonly used in the outpatient setting. It has a very large canister as well. In fact, the canister on this modality is very similar to the original canister on the VAC Classic Device. So it is very robust and allows for capturing a significant amount of drainage and applying a similar type of negative pressure wound therapy to the patient generally again in the outpatient setting.



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So, it is now to discuss the reported mechanism of action of negative pressure wound therapy. We know that by virtue of the fact that it removes fluids and that is an occlusive type of dressing that it may remove infectious materials along with some of those fluids and also some proinflammatory exudate which can be deleterious in some cases to wound healing. It certainly promotes a moist wound-healing environment, and again by the fact that we are delivering negative pressure, if you will, to the wound site we are helping to exploit viscoelasticity of the wound and draw the wound edges together. This particularly in the cyclic nature may help promote perfusion and certainly helps protect the wound environment. Again, the less that we and our patient’s monkey with the wound in general, the better. The clinical benefits are obvious based on those mechanisms of action. It may help promote wound healing, decrease wound size, certainly manage the wound environment, may assist flap and certainly assist full-thickness skin graft take. It assists in bringing about a robust granulation tissue response and helps promote healing in rather complex tunneling and/or undermining wounds.



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Negative wound pressure therapy indications for use are as you see here, we are going to discuss the majority of these indications subsequently. We are not going to have the time to discuss the use of the VAC Instill System, although it may very well be a very promising modality in many types of wounds by allowing us to instill various types of fluids into the wounds and again those types of fluids are limited only by our collective therapeutic imaginations.



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Specifically, the indicated wound types for treatment using negative pressure wound therapy are acute wounds, chronic wounds, we will discuss some of those in a moment, traumatic wounds, partial-thickness burns, dehisced wounds, diabetic ulcers, pressure ulcers, flaps and grafts as we discussed briefly a moment ago.



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Specifically, the types of acute and traumatic wounds that may be indicated for benefit through negative pressure wound therapy are abdominal compartment syndrome, burns of various etiologies, orthopedic injuries with exposed hardware and trauma, surgically dehisced wounds, again flaps and grafts.



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There are varieties of chronic wounds that may benefit from negative pressure wound therapy. Those being specifically pressure ulcers neuropathic/diabetic foot ulcers, and a variety of lower extremity ulcers. Most specifically referring to venous leg ulcers but again not limited to venous leg ulcers based on etiologies.





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There are specific precautions we should undertake when embarking on negative pressure wound therapy, specifically we should not apply this commonsensically to a patient who has active bleeding or difficult wound hemostasis along the same lines or a patient who is on active anticoagulant therapy that is leading to uncontrolled active bleeding or difficult wound hemostasis. We want to avoid putting the dressing in close proximity to exposed blood vessels or organs, and those if they are major blood vessels or organs, require a protective barrier.



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If we continue with our precautions, we want to avoid applying it to a weakened, irradiated, or sutured blood vessels or organs, again that is commonsensical. We want to avoid applying it over bone fragments or sharp edges, those should be either rasped down or covered in some method to avoid harming either the caregiver or the patient. If one is applying it over an enteric fistula, one should take precautions and therapy there. Clearly, one always has to follow universal precautions when taking care of any wound. Again, I would argue that negative pressure wound therapy precautions are all commonsensical precautions.



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Specific contraindications, both relative and firm, include applying this over untreated osteomyelitis. While negative pressure wound therapy delivered through the VAC is a very effective means of covering exposed bone, it is not a treatment for osteomyelitis. Ideally, the osteomyelitis that we treat generally in the lower extremity should be either:

A. Surgically resected.

B. Medically stabilized and/or suppressed.

C. Both A and B.



It should not be applied over a malignancy in the wound. Placement of the VAC therapy over exposed blood vessels or organs are relative contraindications as are over a non-enteric and unexposed fistula. Common sensically, we are



not going to apply this over the necrotic tissue with eschar present, this is why God made a scalpel for us to debride the wound.



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Again, in summary before we get into specifics how to use it in case studies, negative pressure wound therapy applies controlled and localized negative pressure to help uniformly draw wounds closed. It may help remove interstitial fluid which contains inflammatory and potential infectious exudates. It certainly allows tissue compression and again as I said it helps remove those infectious materials, provides a closed moist wound-healing environment. As we discussed earlier may assist in promoting robust granulation tissue and may help improve graft survival and also flap survival.



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So, one of the major components of VAC therapy system before we get into how to use them, specific uses of these modalities. First, there is a therapy delivery unit which we showed. We showed the various types of those in the beginning portion of this lecture. There is a track tubing device which consists of a tube which is attached to a sophisticated sensor unit which helps to apply the localized subatmospheric pressure to the wound in a uniform manner and monitor it throughout the course of therapy. There are VAC canisters of varying sizes depending on the type of VAC therapy device that we are using. There are application specific dressings and there are more of these coming out all the time for various wound types and anatomic locations. There are semi-occlusive drapes not unlike the offside brand that many of us are very familiar using in the operating theatre.



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And now if we move on to specific types of foam dressings, we see the VAC polyurethane foam known by the trade name GranuFoam and we see there are small, medium, large, and extra large foams which can be cut into specific shapes, and there are precut heel dressings with devices that allow one to bridge the track pad away from the site of the heel to reduce potential pressure necrosis which we are going to momentarily and there are thin and round foam shapes. If we move on to polyvinyl alcohol dressings the white foam we see that is under the trade name VersaFoam, and it comes in small and large sizes. These do not promote as much of a robust granulation tissue response which may be useful in certain wound types and again much of this is based on empiricism at this time. There are no good studies presently that identify when to use one over the other, but I think having more of these available for the clinician is better than having to few.



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As you learn when you become more facile with the use of negative pressure wound therapy, there is a 5-step approach. First is after appropriate debridement of the wound and devising and offloading strategy, one is going to place the foam. The second step is application of semi-permeable dressing. The third is to ensure that one has a seal with that semi-permeable dressing. The fourth is the connection of that seal dressing with a central unit and finally there is the setting of device. Each of these requires some degree of experience and training, but as these devices are getting more and more sophisticated, the learning curve thankfully is becoming less and less steep.



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This cartoon merely depicts the various types of dressing applications whether one is using the VAC Classic System as you can see on the right or the VAC Freedom ATS or mini systems on the left, and the slightly more complicated although not much more complicated VAC Instill System in the central aspect that being figure 2 where one has an ingress and an egress port.



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Where runner meets the road I think is this question that is how should negative pressure wound therapy be ideally used in treatment of diabetic foot wounds.



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And it is our opinion really that the negative pressure wound therapy device should really be used not necessarily all the way through to wound healing in most cases, but rather until one develops a healthy granular bed. Essentially the goal of VAC. therapy and what it seems to be most effectively doing is making very complex deep wounds into much more superficial simple wounds. When that task is done, it may be optimal to move to another type of therapy in temporal fashion or to have some sort of overlapping type of strategy. Through our times, however, when one might use the VAC from the offer to the omega from the actual wound presentation through to the end, but in our experience, that has been the exception rather than the rule and the study that we preformed largely to ask that question based on our initial experience with VAC several years ago, what we found was the most frequent dose of the VAC was significantly less than one month, and in fact, generally about a half a month of therapy in many cases just from when we had a complex wound perhaps with exposed bone or tendon to the point where we had a superficial wound with a healthy granular bed.



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Many of you may know that our unit is very active in both the description and survey of various types of diabetic foot procedures. We know now that diabetic foot surgery is rapidly becoming a robust surgical subspecialty unto itself. This has been topped off recently by the first diabetic foot surgery classification system by our unit and the use of this type of modality in diabetic foot surgery has been rather useful, we think, but our goal is really to find its optimal use, and what we believe is that it may be very useful after surgical debridement with the goal again as we said earlier and as we see in this heel ulcer both before and after to provide a healthy granular bed that will be acceptable for grafting, use of other modalities, and certainly for offloading.



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What about potential complications and most importantly how to avoid them because my definition of a good clinician is not someone who necessarily does the procedure the fastest, although that sometimes is a good metric. It really is how someone can figure out how to get out of the trouble and that comes with experience, and experience comes with doing and with listening. And if look at the most frequent complications that we saw in a recent survey as we said was published only a couple of years ago and done several years ago, maceration was by far the most common complication that we encountered. Cellulitis and deep space infections were much less frequently encountered, and those were probably just problems with patient selection rather than specific types of application. So, how do we get rid of that first problem, maceration?



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There are a variety of methodologies to limit maceration. The most useful methodology has been the introduction of the new type of VAC device meaning the VAC Freedom and the VAC ATS dressings with the TRACK pad as we discussed earlier which by allowing for a much easier consistent seal has reduced the amount of maceration that we have seen in from about 1 in 5 to probably about 1 in 8 to 1 in 10 patients in terms of significant amount of maceration. We also are able to modulate and mitigate the amount of maceration in this patient population through the use of stoma adhesive, stoma barriers as you see being done in this case on a couple of small leg ulcers to the use of other types of barrier dressings, and again this is only up to your imagination and common sense.



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And if evaluate specific uses of this in leg ulcers and ulcers that are prone to maceration, we see the dressing being applied here over that stoma adhesive.



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What about less common complications? Well, perhaps the most significant less common complication that we are most afraid of in the diabetic foot would be tuberculosis of the skin. Remember, these patients often will walk on their foot because even with large wide open wound because they do not have the gift of pain. They are not able to feel when that foot should be hurting. Therefore, we have to do everything we can to get that tube out of way and what we often will do, you see being done on this video the patient with large complex diabetic wound on whom we applied cadaveric skin graft, is that we are bridging the dressing away and the tube being bridged away from the bottom of the foot up to the top of the foot.



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And this leads us to the definition of what we call the instant VAC Contact Cast. Many of you may be familiar with our instant total contact cast which is merely a robust removable cast walker like a DH pressure relief walker or an Aircast walker with the foot appropriately dressed and the removable cast walker locked on to the foot with a single layer of plaster or even just some cohesive bandage. Well, the instant VACC is very similar. We see again this large wound as we described when you saw on the last video. The dressing is then bridged up to the top of wound. The tubes that you see there can either be run up or out to the end of removable cast walker. In this case, this is a DH pressure relief walker also known as Active Offloading Walker that construct and then can be wrapped in some cohesive bandage to protect the patient from him or herself and from his or her doctor. And, now you may ask, however, is this dangerous? By the way, this patient can be seen back every couple of days on an outpatient basis and we have been rather successful with this in allowing these patients to do basic activities of daily living at home like cook a meal, use the restroom, or even take a shower, but the first question we ask before doing this was was this applying undue amount of pressure to the bottom of the foot, that dressing that you see there on the bottom left and what we saw in the study that we published recently was that did not seem to be case. In fact, when taken in terms of the initial barefoot pressure there was only about 2% difference in pressures between barefoot and the removable cast walker, pressure reduction in the barefoot and removable cast walker/bridged negative pressure wound therapy, so we felt rather comfortable and we do feel rather comfortable in allowing these patients to go home provided they have a good seal and provided we can make adequate instant VAC Contact Cast Construct.



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We will look at a few case records from our High Risk Diabetic Foot Clinic and then we will close. This is a gentleman who presented to our clinic after having an incision and drainage by another service at another hospital and was advised that he was going to have a below-knee amputation which based on the initial severity of his diabetic foot infection was not at all out of the question. What we see here is that he had exposed first metatarsal which you see there in the center of the wound. Our goal, of course, was to try to heal as rapidly as possible. One certainly could just have taken out a sizable amount of first metatarsal, but our goal was to preserve as much of that parabola as possible to give as much of a weightbearing surface as possible in this case. What we see here is that the VAC. was applied to this gentleman again in an inpatient setting.



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And we see here in his next slide this was his wound approximately 3-1/2 weeks later. As you see the VAC has done what we had described it to do which was to exploit the viscoelasticity of the wound, helping to draw the wound close both distally and proximally. The central aspect of the wound has been drawn together significantly as well. This could just now be closed very simply primarily after it is aggressively debrided.



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And we this done finally in this final photograph with a single-retention stitch applied and that was removed approximately 2-1/2 weeks and this patient now is ready to go off toward prevention.



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We always show cases that seem to show off our common sense or our erudition, but I think it is always useful to show cases that show the opposite that, sometimes our clinical myopia or stupidity and this is an excellent example one of those when it comes to yours truly. This is a patient who presented to us wanting to be treated aggressively for a diabetic foot wound that he had had for several years. You can this is draining a fair amount of pus in this area and we thought perhaps we can aggressively debride this wound which was under its cuboid and you see that being done here with aggressive debridement of the cuboid down to hard bleeding bone. This was packed with antibiotic impregnated calcium sulfate pellets. I believe they were impregnated with a glycopeptide I believe vancomycin.



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And now to look at this wound on the left what we see is we had vacced this wound until it was a robust granular base. When we are left with this, we could do several things, we could certainly rotate something over this area or we could put a skin graft in this area, but if you see here now, this gentleman had come in to see us from another few centers and had several procedures done on him and he had just really what we call Hitchhiker toe which is just that he had one big hallux and no other toes left in the extremely prominent lateral column. In many cases, this was an ill-defined use of the VAC and the VAC may have worked very well in this case, but it was the failure of common sense marry an appropriate post VAC therapeutic regime with what we were doing. We were so enamored with what we thought we can do in terms of to get this wound healed and think very well about how we are going to keep it healed. And you can put whatever you want on this wound and do whatever you want to this wound, but the chances of keeping this wound with almost no fat pad healed over the long-term is probably a fool’s errand, so ultimately what you see being done on the other slides is that he had a ________ of toe flap. We use that hallux to the best of our ability and removed his forefoot.



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And we covered his large defect and tied in his anterior tibial to afford some tendon balancing after doing an Achilles tendon lengthening procedure.



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And we see the final result here, both immediately postoperatively and then at 2 years, so again this was probably what we would consider to be an inappropriate use of negative pressure wound therapy. Again, it did its purpose, but we did not do our bit.



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What about the use of the VAC device or negative pressure wound therapy in split-thickness skin graft? What we know that there are some good works that support the fact that the use of the VAC concomitant with or before or even after the use of split-thickness skin grafting either to optimize or to secure the skin graft in place significantly fewer repeat graftings and improved graft take. In many centers, this type of methodology is standard of care.



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And we see a pertinent example of that in this case. This was actually the use of bioengineered graft, but we frequently would use this split-thickness skin graft as well, and what we see here is after the VAC on this rather large diabetic foot wound, a full-thickness graft was applied to this smaller area, it was cut into place, and subsequently the wound healed in secondarily with excellent coverage with robust granulation and soft tissue subcutaneously.



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So, in conclusion what we have discussed has been a little bit of etiology on the severity of the problem of diabetic foot inferred many of those by some outstanding lectures in this present series. We discussed the indications, contraindications, applications, and some cases associated with negative pressure wound therapy, and I hope what we have done is we have set the stage for other discussions on VAC therapy that will add to your clinical armamentarium as you develop and hopefully this will lead us to treating these patients little bit better after preventing so many unnecessary lower extremity amputations, because I think that is what we all deserve and what our patients deserve whether they have diabetes or not.



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