CME Diabetic Foot

Diabetic Foot Infections - Essential Management Concepts

Barry Rosenblum, DPM

Barry Rosenblum, DPM, FACFAS discusses the parameters of evidence-based management of diabetic foot ulcers. Dr Rosenblum describes classification systems in detail, along with the evaluation and treatment processes. He also reviews diagnosis and treatment guidelines, along with some of the associated controversies.

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Goals and Objectives
  1. Understand a classification system for diabetic foot ulcers.
  2. Learn the current evidence-based methodology for accurately assessing infections.
  3. Review the current treatment guidelines for diabetic foot ulcers.
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    Release Date: 03/16/2018 Expiration Date: 12/31/2018

  • Author
  • Barry Rosenblum, DPM

    Assistant Clinical Professor of Surgery
    Harvard Medical School
    Associate Chief of Podiatry
    Beth Israel Deaconess Medical Center
    Boston, MA

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  • Lecture Transcript
  • Robert Frykberg: Thank you Steve. He led us very nicely into our next discussion, I would ask Dr. Rosenblum to come back and speak on Diabetic Foot Infections Essential Management Concepts, so for the next fifteen minutes pay attention very specifically on the current updates on the appropriate management. Probably the most limb threatening problem that we will deal with which is usually aggressive diabetic foot infections. So let's welcome back Barry Rosenblum, fifteen minutes, okay, Barry and we fly.

    Barry Rosenblum: I couldn�t help but think when Dr. Kaminski mentioned the quarter in the bottom of the cast that I would have looked at that and said oh cast change, but anyway. So anyway for the next fifteen minutes or so I am going to talk a little bit about, well about essential management concepts of diabetic foot infections. Dr. Joseph yesterday talked about the, an update on the guidelines in diabetic foot from the Infectious Disease Society of America. So I didn�t want to go into that in as much detail, I wanted to talk about our approach to the acutely infected diabetic foot as well as our approach to patients with osteomyelitis.

    This quote I think you have all seen at numerous diabetic conferences throughout the world from George Bernard Shaw, The Doctor�s Dilemma, �I am marveled that society would pay a surgeon a large sum of money to remove a patients leg but nothing to save it�. I don�t want to go into epidemiology in great detail but suffice to say that up to 25% of the patients that develop that foot ulcer in their lifetime will require an amputation and as Bob talked about earlier there is substantial morbidity that results from patients with diabetic foot infections.

    So when we talk about an evidenced based protocol for diabetic foot ulcers and this is the only slide that�s going to talk about the things that Dr. Kaminski referred to and also the things later on. I think what's really; really important when you take home the messages to your practice from here to your residency and then later on when you are in practice, what we need to keep in mind is objective evaluation of blood flow, debridement, antibiotics and offloading those are the essential tenets of diabetic foot care. Make sure there is good enough circulation, treat the infection, debridement and offloading. If you can do those four things most of your patients will heal and most of the patients that you see from outside practitioners that haven�t healed probably weren't addressing those four aspects.

    Dr. Frykberg showed this slide earlier on about the gatekeeper and I think it's very important that if you are part of a team, if you are looking to practice, if you are looking to go somewhere where you are going to be part of a team, keep in mind you maybe the gatekeeper, you may not be but be part of that team when it comes to diabetic foot care and that is very important when it comes to patients with diabetic foot infections. The thing to keep in mind and I think one of the thing that�s very overlooked is the fact that not every wound we see is infected. So you might see a superficial wound in the setting of severe arterial insufficiency or you might see a deep wound that�s relatively clean that shows no evidence of infections. So it's extremely important to evaluate profusion in the setting of diabetic foot ulcerations and more importantly in those cases that are infected.

    So when we look at an overview of infections what we need to do there is numerous classification systems out there, both for infected wounds as well as for diabetic foot ulcerations. I think what's important is to keep in mind and be consistent with whatever classification system you use, superficial wounds that show no bone or joint involvement and I will talk a little bit about probing to bone with minimal or no cellulites, no ischemia, no toxicity, those are usually going to be non-limb threatening. Differentiate that from those ulcerations that are deeper that may involve bone or joint. Those that can be and I showed earlier superficial ulcer if the foot is ischemic. Those that have cellulites, lymphangitis the patient comes in systemically toxic those patients are going to have polymicrobial organisms, those are limb threatening infections if you are going to use any classification system whatsoever that�s the simplest one to use for diabetic foot infections not ulcerations.

    So when we look at these patients to make a diagnosis we need to do an aggressive examination, we need to inspect, palpate for any gas, we need to stick a probe in the wound whether it's a stainless steel probe, whether it's a culture swab, we need to stick something in the wound to assess how deep that is. We need to then size and we need to debride that is extremely important, your internist colleagues or endocrinology colleagues they are looking at the foot, they are not doing these other things where they are actually touching the foot. We use an MRI only when we are uncertain and I am going to go into that as far as the diagnosis of osteomyelitis shortly.

    When it comes to surgical treatment of the diabetic foot especially that with infection diabetic patients do not tolerate un-drained sepsis, infections tend to go up tissue plains, they tend to go up tendon, you can�t rely on antibiotics alone and those patients need to be taken to the operating room as soon as possible. One of the vascular surgeons at the Deaconess used to be known to hear from residents that a patient was too sick to go to the operating room and in fact the opposite was true. The patient was too sick not to go to the operating room. And I just love showing this slide because I happen to catch it in midstream, but this is the type of abscess that we see that needs to be opened up, we squeeze on the foot, pus came out, we took the patient urgently to the operating room.

    This is an example of a young type I diabetic patient, she was seen by her internist and sent home with a surgical shoe and Ciprofloxacin, you could see what could be a relatively benign appearing ulceration but there are some redness significantly in the in step. Dorsal aspect of the foot doesn�t look too bad, it's a little swollen but there is no ascending cellulites, no redness dorsally. A probe we were able to stick this ophthalmic probe deep into the mid step, into the in step of the foot. We took her to the operating room that night and we opened up all the way down to the plantar fascia. These patients need to be inspected, palpated, probed in order to determine whether or not they have a limb threatening infection.

    As far as deep infection management is concerned this paper came out back in �96, a retrospective evaluation of one hundred and sixty four patients hospitalized with diabetic foot infections, divided into two groups. Those that had no surgery within the first three days but were on IV antibiotics, typically the patients we see that are admitted to the medicine service, consult to podiatry takes 24 to 72 hours unfortunately in some cases, versus a group that had prompt surgery and IV antibiotics and that prompt surgery was either debridement or limited amputation both with IV antibiotics. And what they found was the rate for the subsequent need for above ankle amputation or below knee amputation was 27% in the first group that delayed surgery and only 13% in the second group and these are people with severe deep infections. Keep in mind the take home message here is these are emergent if not urgent infections that need to go to the operating room. In addition to increasing limb salvage rate this aggressive approach to deep infections decrease the length of hospitalization by six days.

    When it comes to osteomyelitis in the feet of diabetic patients and this was looked at a little bit in more detail and the idea say recent clinical practice guidelines that came out just recently. When it comes to osteomyelitis very often it's difficult to differentiate a soft tissue from a bone infection at least clinically. It's also difficult to differentiate from those patients that have Charcot deformity and you are going to hear a little bit more about that later on today. Studies have shown that many of those patients will have Charcot when they are looked at and told that they have an infection going on. The SED rate has a high sensitivity when elevated and the white blood cell count is not nearly as predictive. I tend to use not just their temperature, not just their white blood cell count but also their blood sugars, which can be a nice little parameter to look at when it comes to measuring how much or how little infection is taking place.

    When it comes to clinical findings in making your diagnosis, Newman reported that the larger and deeper skin ulcerations had an increased risk of osteomyelitis underlying that wound. At our institution Lindsay Grayson back in a paper that looked at probing to bone found that if you can contact a bony surface the sensitivity of osteomyelitis being present was 66% with a specificity being 85% and the most important take home message here was that the positive predictive value was 89%. Now unfortunately these patients had all been admitted as part of another study so these were patients that at the outset had a more significant wound then all comers that we might have seen in office setting or combining an office with a hospital based setting.

    So, Lavery back in 2007 looked at Probing to Bone whether it was reliable or relic and what he found is that the probe to bone test was both sensitive and specific but found that the positive predictive value was only 57% and what he found and again this is looking more at outpatients then at our study or the Grayson looked at inpatients then the negative test may exclude diagnosis of osteomyelitis. Subsequently Lozano out of Spain a few years ago looked at a prospective study trying to validate the probe to bone test and found that the ulcer infection, not osteomyelitis but infection was diagnosed with clinical signs and culture, a presumptive diagnosis of osteomyelitis was made based on simple test such as x-rays and probing to bone and found that this had a significant sensitivity, specificity in both positive and negative predicted value. And what they concluded was that it was of great diagnostic value and efficient for detecting osteomyelitis in the diabetic foot.

    So the question then comes up will an MRI help with the diagnosis of osteomyelitis. So Kroll looked at a number of years ago the role of MRI and the diagnosis of osteomyelitis and compared it to plain radiographs, technetium bone scans and indium bone scans and found that they concluded that the MRI was the only test that was statistically significant and cost effective. And keep in mind you are not just trying to find the diagnosis that you give the patient an ICBM code you are trying to find that diagnosis so that you could treat them either with something more expensive such as taking them to the operating room or putting them in a situation where they are going to have a prolonged course of antibiotics and this is a debate that we constantly have with our infectious disease service.

    There are controversies in diagnosing and managing osteomyelitis in the feet, the microbiology of osteomyelitis, the bone biopsies, the gold standard but it's difficult to do in metatarsals or toes and unfortunately the diagnostic sensitivity for MRI is high but the specificity is limited due to neuropathy. And it's interesting when I have this conversation with my patients and they come and say oh I did an MRI, it says I have osteomyelitis, I had a SED rate it tells me I have osteomyelitis. I take my two hands and I walk out of the treatment room right outside the door and I say okay your SED rate was high Mr. Smith. If it was high because of infection I am going to tap on the wall with my left hand. If it was high because of something else I am going to tap on the wall with my right hand and I walkout where they can�t see me and I tap on the wall and I say which is it and they said I can�t tell. So that shows the patient on their level how non-specific a test such as a SED rate or an MRI could be.

    Looking at, some of them looked at the culture of percutaneous bone biopsy and basically their take home message the bottom line was that it confirmed the poor liability of superficial swab cultures and the safety of percutaneous bone biopsy and the fact that there is a variability in the floor of diabetic foot ulcers that shows that there is a discrepancy between what you get on that superficial swab and what you get from the bone itself. We know a couple of years ago, last year I looked at the histology versus microbiology for the accuracy and identification of osteomyelitis and what they found is that most rely on the histological evaluation to make the diagnosis of osteomyelitis. However, looking at their paper concluded that microbiologic testing maybe just as likely to achieve a diagnosis of osteomyelitis say histological testing and gives more information such as what bacteria�s involve and more importantly it can be cost effectively.

    So I think specifically at our institution there is a debate that goes on as to which is more important the histological or the microbiologic. And we all know if you are puling bone through wound, if you are not doing your biopsy from a separate site there is a chance of contamination and I go to great strides to explain it to my patients that this might limit the length of time that they are on IV antibiotics for a confirmed diagnosis of osteomyelitis versus a shorter period of time where we remove the infected bone, made sure that the margins are clean and put up on mop-up therapy with oral antibiotics. And talking about margins this look at the effective residual osteomyelitis at the resection margins showed that if patients had margins that were still positive for osteomyelitis there was an increased risk of amputation and there was an increased risk of treatment failure.

    The antibiotic advocates that are out there, these are people that have IV infusion centers that proponents have six if not longer, six week or if not longer periods of IV antibiotics. They showed significant success rates with IV antibiotics alone. However, they did not pathologically prove it there was osteomyelitis, their diagnosis was based on a clinical and physical assessment, wound culture and radiographs and we all know that that�s not an effective way to diagnose osteomyelitis in the diabetic foot. So the idea, say this is back in 2004 recommended establishing a consensus definition of osteo on the diabetic foot and to compare outcomes of surgical and non-surgical management of osteomyelitis which really still hasn�t been done. There are controversies in diagnosing and managing osteomyelitis in the feet, the available evidence, so this is again a number of years ago may suggest that a non-surgical approach maybe effective for many if not most and in our institution that�s not the case.

    The contribution of conservative surgery here you can see patients treated with antibiotic therapy alone versus conservative surgery found that there was a significant increase in the healing rate, 78% versus 57%. Osteomyelitis of the foot and toe in adults it's a surgical disease, conservative management may worsen lower extremity salvage and what's happened is there is increased healing seen with surgical debridement but again their conclusion was that prospective randomized trials were needed. Once the foot is not infected, once the osteomyelitis has been cleaned out, this study from Yale ten years ago was very, very effective in pointing out the single stage surgical treatment of non-infected diabetic foot ulcers once you have cleaned out that infected bone. It was a retrospective study excising the ulcer with broad exposure, correcting the underlying osteo deformity as Dr. Kaminski alluded to with a primary closure using a local random flap and what they found that they significantly enhanced the healing rate and decreased the recurrence rate and most importantly reduce the healing times, decrease the cost and eliminated the need for further surgery.

    So a couple of cases just showing the approach that we have at the Beth Israel Deaconess Medical Center here is a patient with a presignificant infection of rip-roaring cellulites, probe to bone we did no further test this patient needed to go to the operating room, taking out that metatarsal head will determine A, if it's osteomyelitis, B, if it's osteomyelitis has gone, C, if it wasn�t the bony pressure point is gone and they can now have an ulcer free foot. We took out the second metatarsal head, here she is healed, she developed a transfer ulcer, we went and did a panmetatarsal head resection incision over the first metatarsal for the medially over the fourth and fifth laterally, plantarly we excised the third metatarsal, she had already lost the second and here you could see a foot after a pan metatarsal head resection. So these patients can go from osteomyelitis to healed without having a forefoot amputation.

    Another case of a patient I did an excisional biopsy of the great toe, unfortunately at the hest it went on to osteomyelitis and here you can see the toe afterwards and she went on to a ray amputation. So even in the best of situations and circumstances good enough perfusion relatively benign wound these can come to haunting, these were sick patients that will not necessarily heal the way you hope they will. This is a patient that had lost his second toe with an ulcer under the first metatarsal, you can see the cellulites, you can see a significant of debridement, this points out the team approach had a revascularization, negative pressure wound therapy and here you can see after skin grafting. So again team approach we included the vascular surgeon, the plastic surgeon in our group.

    So in summary foot infections in patients with diabetes are a clause for substantial morbidity, there were major predisposing factor to infection which you have to keep in mind is ulceration. Wound infections must be diagnosed clinically, they must be categorized based on severity, no matter what classification system you use and it may be treated I think more appropriately and effectively with surgical excision with adjunct antibiotic therapy. And I thank you for your attention.