Section: New Board Review Category: Diabetic Foot

Epidemiology of the Diabetic Foot

Robert Frykberg, DPM, MPH

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Goals and Objectives
  1. Recognize the significance of diabetes in our population
  2. Describe the importance of diabetic foot complications
  3. Report the epidemiology of the diabetic foot syndrome
  4. Describe the pathophysiology of diabetic foot complications
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  • CPME (Credits: 0.75)

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  • Lecture Transcript
  • TAPE STARTS – [00:00]

    Male Speaker 1: So I'm going to start with a more or less an overview, and I really think you need to appreciate the magnitude of this disease and this problem, not just here in America, but also in the country. I don't have any conflicts with this. These were just my main objectives, pretty much as I've said. You just have to understand the magnitude of the problems underlying these patients, and then you'd be better prepared to manage their foot disorders.

    So we know diabetes in the USA continues to grow and it encompasses about 9% of the US population, and as we all know, it's growing. And there's a large number of undiagnosed people as well as diagnosed people. And the data always follow several years behind, so it's not exactly accurate, but with all the immigration that we have into this country from third world countries, even from the Middle Eastern countries, this number is going to continue to grow.

    At great cost, as you can see, $250 billion is an old figure, quarter of a trillion dollars just on taking care of patients with diabetes, and of course the seventh leading cause of death in United States related to not just amputations, but also heart disease and renal failure. So a significant problem for us. And if we look at the major lower extremity complications, which is why we're really here, we have to recognize the important role of neuropathy, ulceration, infection, PAD, lower extremity amputation, and Charcot foot, which we talked about somewhat during our course.

    But of all these peripheral neuropathy is the most important risk factor for every other complication. It is always the most important risk factor and in fact neuropathy in patients without diabetes is important risk factor for ulceration, infection and amputation.


    So remember, a patient with neuropathy, you must place at a much higher risk for potential complications because that is where the problem lies, neuropathy. It's not the diabetes. It's the neuropathy associated with the diabetes that's most important, and that's related to all these other conditions as well. And we'll be talking about a number of them during the course of our program.

    This is a little bit dated, not too much, but we can just see hospitalizations for lower extremity conditions were associated with diabetes and ulceration, 113,000 hospitalizations. This was in one year from the National Diabetes Surveillance System, also PAD and neuropathy. So these are the three major admitting diagnoses. But as all of you can realize, many of these people have the same thing. Most of people with ulcer is going to have neuropathy of course and many of the people with PAD are going to be admitted also with an ulcer and neuropathy. So this is the problem with survey data, such and such. But it just shows the magnitude of these problems as well.

    And we've made some headway over the last certainly 20 years in terms of reducing the number of major amputations. 1996 was really the high point in the country where we had 80,000, 90,000 amputations in diabetic patients. Now, it's gone down to about 73,000 non-traumatic LEAs. When we talk about amputations, we always remind ourselves to talk about non-traumatic amputations in diabetes.


    These are the ones that are really due to ulcers, infections and gangrene. And the course continues as you can see, we have a reduction in number of major amputations while we have an increase in a number of minor amputations or stabilization, the number or minor amputations due to improvements in diagnosis, as well as vascular intervention for PAD. And a graph like this is similar no matter what country you go to around the world that is instituted appropriate multidisciplinary diabetic foot teams. You might have seen graphs similar to this that actually comes from the study by Belch in 2003 where he's comparing lower extremity complications including PAD to other types of cancer in five year mortality rates.

    And we can see amputation, foot ulcer, Charcot foot, PAD, have higher five year mortality rates than prostate, Hodgkin's disease, breast cancer. And so it just goes to show that these are very, very serious problems in these individuals. I used to often say, "Well, you know, some patients have malignant diabetes." Meaning, they have retinopathy, nephropathy, neuropathy, PAD, and this graph goes to show you how really relevant the problem is where their mortality rates are higher than very common rates of cancer.

    So again, illustrating the magnitude of the problems that we're facing when we take care of these patients. This paper is from Van Baal and Fran Game who is here several years ago, and William Jeffcoate as well, published in 2010, and it's from their series at Nottingham. And what they're showing here is the one, three, and five years survival rates – or excuse me, one, three, and five year mortality rates for their patients with Charcot foot and DFU, diabetic foot ulcers.


    And you can see now diabetic foot ulcer and Charcot foot have pretty much the same five year mortality rate, about 40% mortality. So these are indeed big problems for us and we see another paper that came out of the Hines VA also looking at the five year percent mortality, looking at patients with diabetes as a baseline without Charcot foot and DFU. We see that Charcot foot five year mortality is 28% and DFU is 37%. So when we recognize and we treat these people, we see that they are at a heightened risk for premature mortality compared to certainly non-diabetic patients but also compared to non-diabetic patients without these underlying problems.

    So they are markers or significant risk factors for early mortality. Now, they don't die of DFU. They don't die of Charcot, but the DFU and the Charcot are markers of serious underlying metabolic perturbations. This paper comes from [Jim Robel] [00:07:28] and his group at University of Michigan and they're just looking at a review of a prospective observational study there with 10 years of follow up. And this study was not looking at lower extremity diabetic foot problems but it was just looking at a large cohort of diabetic patients. And they looked at the risk factors for all-cause mortality. And as you can see here, this is the unadjusted risk factors, Charcot neuropathy 80% increase risk for mortality during this time period.


    Diabetic foot ulcer, 93% increased risk, and lower extremity amputation, over three fold risk of mortality in this time period. Now, these are not adjusted for one another, so we look here at the multi-barrier or fully adjusted model, and we see that lower extremity amputation and parts, at 94% increase risk for mortality over 10 years compared to patients who do not have lower extremity amputation, diabetic foot ulcer or Charcot foot. So again, very hard data in a real life situation showing you that these are really significant problems for these patients.

    Here, we can see a graph looking at the survival curves for patients with no LEA, no lower extremity amputation, minor, and then the lower curve is from the patients who have had major amputation, and you can see how they dropped off much faster than the others. So this data is really no different than other data from around the world but it still highlights the importance that amputation plays in the life of these patients.

    I often use this group, this graph. And I'm sorry if you get tired of seeing it, but I like to reinforce the fact that these are complicated patients. And of course we have diabetes as the setting here but recognize that most of your patient is going to have neuropathy to some degree. And neuropathy just does not mean sensory neuropathy alone. It also means motor neuropathy with atrophy, equinus, high forefoot pressures, leading to osteoarthropathy. Of course sensory, and also autonomic neuropathy, which a lot of people kind of lose sight of autonomic neuropathy. It's very important with cardiovascular autonomic neuropathy, microneurovascular disturbances in the small blood vessels, leading to AV shunting or sympathetic failure.


    And then, that leads over to microvascular disease. When we talk about vascular disease in a diabetic patient, we do consider the role of microvascular dysfunction, microvascular changes like thickened capillary basement membrane, AV shunting, et cetera, as well as the all-important macrovascular, atherosclerotic occlusive disease, where we'll be having several talks on today. Recognizing all these problems should facilitate your assessment of the patients because you need to look for these problems because they are going to impact the ability of your patients to heal, and they're going to underlie the reason why there's so many complications.

    Because we have these setting problems but we also have the impaired response to infection that is inherent in the hypoglycemic diabetic state. So you apply trauma to this high risk foot. Let's say they get a break in the skin envelope. They continue to walk on it because of unrecognized trauma. They've lost the gift of pain as [Paul Bran] [00:11:17] had said. They get infected. They keep walking on it and it becomes a vicious cycle. They develop infection, gangrene, continues to walk on it, and then they are subjected to amputation.

    So while not all patients will have all of these metabolic perturbations and problems, many of them will, and you need to recognize that so that you can properly assess and properly treat them. I like to refer to Gayle Reiber's paper, Diabetes Care 1999, because it's a simplistic approach. And it's nice to be able to take a very complex system and coalesce it into something a little bit more easy to understand.


    They used the Rothman model of disease causation, which nine years previously, Roger Pecoraro had described for causal pathways, leading to amputation. They had picked this up for causal pathways leading to foot ulcers. Gayle Reiber worked with Pecoraro. And what they looked at was about 150 or so patients with foot ulcers and looked for their causal risk factors leading to those ulcerations. And they looked at neuropathy, trauma, deformity, edema, ischemia, callus and infection. And they found this critical triad and 63% of those – excuse me, of those pathways leading to ulceration.

    And of course neuropathy remains at the center of the problem as you can see but also deformity and trauma. So when you put neuropathy, deformity and trauma together into one completed causal pathway, it invariably will lead to an ulceration and that's really what this means. This becomes these component causes. Each one of these are component causes. When they come together, it's a sufficient cause, sufficient enough to cause the outcome, which in this case is a foot ulcer.

    So it's a simplified approach but it just goes to show the importance of neuropathy, deformity and trauma. Trauma can be walking barefoot in Phoenix in the summer. How many times do we see second and third degree burns, or walking with a nail or a tuck in your shoe, et cetera, et cetera? So a simplified approach but it makes good clinical sense. What are the common deformities, since we now know deformities are important risk factors in the causal pathway leading to ulceration?

    Of course hammertoes, bunions, prominent metatarsal heads, Charcot arthropathy, the classic diabetic neuropathic deformity. Equinus, we did a study that shows that diabetic patients do indeed have increased prevalence at equinus compared to non-diabetic patients.


    And of course partial foot amputations as well, you take out one part of the foot, you're going to transfer the load to another part of the foot. So this become very important deformities but sometimes we need to correct and sometimes we just need to manage conservatively. Dave Armstrong, Sicoo Bus and Andrew Boulton published a paper in New England Journal Medicine this summer looking at risk factors for ulcer recurrence. Now, when you look at risk factors for ulcer recurrence, you can surmise that those same risk factors are risk factors for primary ulcerations.

    So what they looked at was of course neuropathy and these are just measures reviewed in a variety at a number of prior publications over the preceding three decades or so. Vibration perception, threshold of course and measure of neuropathy, presence of pre-ulcerative lesion, these are increased risk factors for a recurrence. PAD, number three on the list, pre-ulcerative lesions, and as we go down, I'd recommend that you look at this paper because it's very insightful.

    And this is a simple graphic to illustrate how sensory neuropathy, high pressures will predispose to a callus formation here, and then the callus formation with that goes untreated, and repetitive stress will lead to that underlying ulceration. And again, it's just a simplified way to look at the pathways that can lead to diabetic foot ulcers. And recognize diabetic foot ulcer is a very significant risk factor for amputation, which is really what we're here to discuss today and a number of possible risk factors.


    Remember, these are just risk factors isolated in a variety of studies from around the world but of course, it's neuropathy, PAD, deformity, trauma that are at the top of the list, as well as uncontrolled diabetes mellitus. And here we just see a graph over the course of time, the incidence rate of recurrence. Generally, you can plan on an ulceration recurring within three to five years. If not a recurrent ulcer, a new ulcer on the same foot, and this one is a 10-year ulcer recurrence at 100%. This is from Stephen Morbach's 10-year review out of Germany.

    But you can see most of the ulcers are going to recur early on but within one or two years, you can see there's a large number of recurrent ulcers, because people are not paying attention to preventive care, proper foot ware, proper surveillance, et cetera. So very important but simple points to remember. So what are the risk factors for amputation? Again, the same risk factors as we mentioned for ulceration, neuropathy, ischemia, infection and ulceration, in this case gangrene. Prior amputation is a risk factor for not only ulceration but for subsequent amputation.

    Trauma, and then some laboratory values had been shown to be associated most notably a high hemoglobin A1C, and high white blood count on admission to hospital, had all been isolated as possible risk factors associated with increasing rates of amputation. So as we can see, the same risk factors for ulceration are risk factors for amputation, with the exception of infection. Infection usually follows and ulceration doesn't precede the development of an ulceration. But again, neuropathy is on top of the list.


    My friend, Lee Rogers, is here at the session this morning, so I like to illustrate this. This came out of a publication that we did in general vascular surgery in 2010. And again, it's a simplistic view of the processes involved leading to amputation, which is why I like it. Most of us of a certain again remember Stairway to Heaven of course, so this is – I don't think amputation is quite heaven, but it serves the purpose. So at the bottom we have the high risk foot. That patient with neuropathy with or without PAD and deformity sustains some type of an injury.

    Sometimes just an untreated callus or here's from Phoenix walking barefoot in the summer, developed into a chronic wound because it's not addressed adequately and early enough, or aggressively enough. Then it becomes infected, then develops gangrene. And of course once you develop gangrene, amputation at some level is necessary, depending upon the extent of tissue loss and then perfusion. So a simplified approach but the important point is there are multiple areas or steps along this pathway in which you can intervene to prevent progression further.

    Like preventing such injuries by education, don't allow patients to walk barefoot. Check their shoes, et cetera. Or when there is a wound treated early so it doesn't get infected, or when it's infected, treat that infection aggressively and early, so it doesn't go to gangrene. So there's multiple points here, and if you have PAD, diagnose it early way down here as soon as you see that patient so that you can refer them out for revascularization. Many points or many opportunities for intervention in this regard.

    Again, this is from Stephan Morbach's paper, published diabetes care several years ago, looking at a 10-year perspective follow up of almost 250 diabetic foot ulcer patients. And basically he was looking at incidents of first major amputation and the risk factors underlying that.


    Basically he found that 51% had severe PAD at the time of their presentation. And looking at multivariable predictors of first major invitation of course, PAD, as you would expect 35 fold increase risk for first major amputation. And the graph here just demonstrates the curves for no PAD, mild, moderate, and severe PAD, as you would expect those limbs drop off very, very rapidly, and these patients also die accordingly with the incidents of major amputation.

    We look at Larry Lavery's work. This is an old study but also insightful looking at risk factors for foot infections. As you would expect, bone penetration, almost a sevenfold increase risk for infection. Wound duration, greater than 30 days. Almost a fivefold risk for infection. Recurrent foot wound, recurrent foot wound means there are high risk for infection either because they keep getting the same problem over and over because it hasn't been corrected, or there's underlying smoldering infection that keeps blowing out after a wound heals.

    A traumatic wound and of course a PAD is risk for infection within this group of patients. So again, the visualization of bone or probing to bone in and of itself, very, very significant risk factor not just for an infection but of course for osteomyelitis. A simple thing like probing to bone can facilitate the proper diagnosis and management of these problems to hopefully avoid consequences like this that occur from an untreated ulceration.


    So how can we prevent limb threatening problems? This is nothing new. If you go back to Elliott Joslin's paper, minutes of diabetic gangrene, New England Journal of Medicine in 1934, he's talking about exactly the same things we're talking about today, only he implemented them back in the '30s in Boston. Education of both patients as well as provider, that's why we're here. Protective foot ware, this is nothing new.

    And Steve, this is the old talk because I had added something in here. So regular preventive foot care, critically important. That's your prevention program with aggressive management of new lesions. Also, we presented a talk on this in the seminar. I think it was just yesterday on the use of a smart mat, new technology, a wireless remote temperature assessment mat as part of your prevention program, where you can highlight increased inflammation and foot temperatures in a patient's foot.

    And we isolated these temperatures five weeks before the onset of ulceration. So we were able to get triggers on the foot temperature assessments five weeks before the development of an ulcer. So foot temperature assessments really need to be part of your overalls scheme for preventing amputations and preventing foot ulcers. Prophylactic foot surgery, we'll be talking about this. Deformity, correction, stabilization.

    We know that deformity is an important risk factors we saw from the Gayle Reiber study in 1999. So at the opportune time, we try to correct these deformities if the patient has sufficient perfusion. If they're medically stable enough, we deform these. Hopefully, when they do not have an open ulcer. Otherwise, it becomes more of a curative procedure rather than a prophylactic or an elected procedure.


    And of course multidisciplinary management, which is a theme, and in fact our meeting was really called the multidisciplinary high risk. But somehow that's the name of this conference for many, many years. Multidisciplinary management is a necessity. It doesn't mean you have to round on people as a multidisciplinary team all the time but you have to have some kind of a team setup either in your multidisciplinary clinics or in your hospitals where you can promptly refer your patients to the appropriate specialist as you detect they have an underlying problem that needs to be addressed.

    And of course multidisciplinary management means good diabetes control, since diabetes and high A1Cs underlie many of these problems. You need your vascular colleagues, whether endovascular and open surgeons, or your interventional radiologists as we'll hear later on today. Orthopedics, podiatry, nursing, radiologists, et cetera, et cetera. You must work in a team. Elliott Joslin was promoting multidisciplinary management back in the late 1920s. It's just we've caught onto it about 30 years ago that this is an important part of our management.

    And by instituting a multidisciplinary team, this paper came out of Scotland years ago, several years ago, where they looked at the gradual reduction of amputations, both major and minor, after they instituted a team right here. They started their team in early 2005 and you can see the gradual, the green bar here refers to the total number of amputations and you can see how they steadily decreased. But if you look at the yellow versus the blue, the yellow, major amputations decreased 41% in this five-year time period because of the institution of a multidisciplinary service.


    Total amputations went down 30% due to multidisciplinary service or multidisciplinary team. This same message goes throughout all literature dealing with multidisciplinary teams. Their rates of major amputation always go down because people are focused on preventing amputation. I keep doing that, I'm sorry. Aggressively intervening and revascularizing when ischemia is detected.

    This is my model of a multidisciplinary service that I've used for many years. I guess this is an old term, podiatrist gatekeeper, but we are the ones who see this people the most frequently, even as part of our prevention program, or we get referrals from hospital or primary care physicians, or whoever when the patient has a problem. And so we need to work as a team with our vascular surgeons, with our internists, hospitalists, diabetologists, and all of our consultants as appropriate, and the ancillary services to work as a team to get these patients healed and to prevent the amputation.

    And the foot in the middle refers to the patient. Without the patients' involvement in this program and with this team, we'll never going to be successful, because we recognize that patient adherence or patient compliance is a shortfall in our proper prevention protocol. So that's where education of patients becomes so very, very important. So in summary, diabetic foot complications are leading causes for diabetes-related hospitalizations. Neuropathy, PAD, ulceration and infection are major risk factors for amputation.

    Both ulceration and amputation adversely affect survival, and knowledge of risk factors for complications provide an opportunity for early intervention and prevention, and we prevent the foot ulcer initially we're going to prevent subsequent necessity for amputation because of infection. So with that let me say, thank you. Okay.

    TAPE ENDS - [28:23]