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Expert Insights On Damage Control Debridement For DFUs
Given the variety of potential complications with diabetic foot ulcers, these authors discuss keys to patient and wound assessment, and how appropriate surgical debridement can facilitate improved wound healing.
The goal of any podiatric surgeon practicing limb salvage is to heal any type of wound in a timely fashion with the highest possible functional outcome. In our specialty, we recognize the diabetic population has a particularly high risk for lower extremity ulcerations often secondary to neuropathy (sensory, motor and autonomic deficits), ischemia or both. Singh and colleagues noted that patients with diabetes have as high as a 25 percent lifetime risk of developing a foot ulceration.1
The lack of successful treatment of these wounds can have catastrophic outcomes. Diabetic foot ulcers (DFUs) are the most important risk factor for lower extremity amputations and numerous studies have noted increased mortality following an amputation in patients with and without diabetes.2–5 Therefore, it is vital to recognize the importance of proper treatment for lower extremity ulcerations as significant data and clinical experience have proven the cascade of diabetic ulceration to increased amputation risk to increased mortality rates in complicated limb salvage patients.
With this in mind, it is important for clinicians to have a strong understanding of the core fundamental factors of surgical debridement, which is an invaluable tool in infection control and wound healing. Additionally, one should also be aware of other critical elements that play a role in impeding and improving wound healing.
A key step to achieve wound healing in a normal and timely fashion is wound debridement. Debridement has proven effective in both acute and chronic wounds. We can define an acute wound as a recent wound that has yet to progress through the sequential stages of healing. A chronic wound is a wound arrested in one of the stages of wound healing (i.e. inflammatory stage) and fails to progress further.6 Control of chronic or infected wounds is a multifactorial process altered by the quality of debridement, virulence of bacterial species, degree of bioburden and the host’s ability to launch an effective immunological response.7 The ability to launch this response is the foundation of clearing infection because with scarce local resources (oxygen, nutrition, growth factors, chemoattractants), the body cannot initiate a fight against an infection. We find this situation daily in our complex compromised patients. Patients with poorly controlled diabetes, renal failure, peripheral vascular disease or a combination of all the aforementioned are limited by their inability to begin the launch to healing.
Infected tissue, necrotic tissue and foreign material produce and stimulate the production of proteases, collagenases and elastases that impede the body’s local wound healing process.6 When utilizing a proper technique as we describe, aggressive debridement has the ability to convert a chronic wound into an acute wound and facilitate the normal phases of healing.
As a multifactorial process, limb salvage requires physicians of multiple specialties to work as a team. This approach between podiatric surgeons, vascular surgeons, plastic surgeons and infectious disease physicians optimizes successful outcomes. Preoperatively, there are many considerations. The factors for preoperative assessment that we will focus on in this article are: identifying the etiology of the wound; recognizing the factors impeding healing; deciding when to operate; and developing a surgical plan to achieve a functional outcome.
Considering The Wound Etiology Before Debriding DFUs
As we previously mentioned, the diabetic population develops foot ulcerations secondary to neuropathy, ischemia or both. Neuropathic ulcers, resulting from tissue-damaging mechanical loads applied to an insensate foot, are the most common DFUs.8 Mechanical loads in insensate patients with an underlying biomechanical deformity, such as restricted joint mobility or bony prominences, cause a high volume of ulcerations due to elevated plantar pressures.
Petre and coworkers validated this idea by demonstrating how pressure between the foot and ground at a plantar prominence can exceed 1,000 kPa.9 In contrast, pressure between a correctly applied offloading total contact cast and a potential ulcer site is less than 100 kPa. This idea illustrates why offloading, whether conservatively with footwear/casting or surgically with reconstruction, remains widely accepted.
Ischemia remains another leading cause of ulceration. Preoperatively, it is imperative to evaluate a patient’s vascular status through palpation and a handheld Doppler. Upon Doppler examination, triphasic and biphasic signals correlate to sufficient blood flow.6 A monophasic signal indicates questionable flow. A monophasic signal or any concern for underlying ischemic etiology warrants consultation to a vascular surgeon, specifically one who specializes in distal revascularizations.
Both diagnostic and interventional angiography are useful as they can provide the surgeon with a map of the patient’s vascular network. With this knowledge, a surgeon can delineate where the patient has enough blood flow to heal a wound, surgical incision, local flap or free tissue transfer. For example, if a patient requiring a transmetatarsal amputation has angiography results showing strong anterior tibial artery flow but diminished posterior tibial artery flow, a surgeon should plan accordingly. In this scenario, one should focus on a prominent dorsal flap, given the strong anterior tibial artery flow, rather than a standard plantar flap, in order to optimize perfusion and prevent flap necrosis.
In the face of an interventional angiography or open bypass to reestablish blood flow, Rhodes and colleagues have shown it is preferable to wait four to 10 days after revascularization to optimize blood flow before further operative intervention for debridement or closure.10 In this intermediary period, it is crucial to observe the wound closely as the renewed blood supply can convert dry gangrene to wet gangrene, and immediate debridement will be called for regardless if one has achieved vascular optimization. Understanding the etiology, whether it is neuropathic, ischemic or neuroischemic, as well as the biomechanical deformities will drastically change the surgical plan to enhance successful and functional outcomes.
How Debridement Can Overcome Some Of The Obstacles With Wound Healing
An essential part of the complete preoperative evaluation is recognizing any factors impeding wound healing. When unabated, wound healing progresses in an orderly, predictable fashion through inflammation (reactive), proliferation (regenerative) and maturation (remodeling).11 Numerous factors can play a detrimental role in healing. These factors include biofilm constructs, nutritional status, medications, excess mechanical loads and inadequate perfusion. Without properly evaluating and addressing each element, even the best surgical debridement will not lead to a successful outcome.
Over 90 percent of chronic wounds contain bacteria living within a biofilm construct.12 The presence of necrotic tissue, foreign material and/or bacteria impedes the ability to heal. Changes in cellular DNA synthesis lead to increased formation of matrix metalloproteases, obstructing the body’s attempt to heal by overwhelming the building blocks for normal wound healing.13 This process creates a hostile environment, allowing bacteria to proliferate and construct protected colonies known as biofilm. Newly formed biofilm lives in a more active phenotypic stage with a less developed matrix, causing more susceptibility to antibiotics, biocides and host immune mediators in comparison to older, mature biofilm.12
Wolcott and coworkers described the timing and success of attacking biofilm with repeated physical debridement and antibiotics in two separate articles.14,15 In 2009, Wolcott and coworkers emphasized the importance of repeated physical removal of the biofilm to suppress regrowth and keep the biofilm in the earlier, more susceptible stage.14 In 2010, the authors showed how bacteria are more susceptible to selective antibiotics in the first 48 hours of formation.15 Comprehending the physiology underlying biofilm allows the surgeon to take advantage of this small window to attack biofilm before it reaches its mature stage and hinders wound healing.
Emphasizing The Need To Assess Nutritional Status And Patient Medications
Physicians often overlook nutritional status and patient medications that have strong influences on wound healing. Without adequate protein, a patient cannot provide an appropriate healing environment. Protein depletion decreases angiogenesis and fibroblast proliferation, which results in decreased synthesis as well as accumulation and remodeling of collagen.11 Protein levels are not difficult to evaluate and one can do so through lab tests such as albumin, prealbumin, transferrin and insulin-like growth factor 1 (IGF-1).
Hypoalbuminemic tissue edema occurs with an albumin level below 3.0 g/dL, which causes impairment to collagen formation and decreased oxygen delivery.11 Though 3.0 g/dL is the start of the hypoalbuminemic edematous state, most authorities agree that normal wound healing will not occur when the albumin level is below 2.0 g/dL.11
Physicians often miss certain medications in a patient’s history. Chemotherapeutic agents, steroids and anti-inflammatory agents directly blunt the cellular response in fibroblast proliferation and collagen synthesis, making healing more difficult.11 Surgeons should fully evaluate a patient’s history and consider measuring and replenishing protein stores to optimize the healing environment.
Where Biomechanical Considerations And Adequate Perfusion Come Into Play
We mention mechanical loads and inadequate perfusion again as a reminder that without addressing these factors, a successful outcome is unlikely in DFUs. The surgical plan should include biomechanical considerations to limit high pressure points to promote decreased risk of reulceration postoperatively. The focus should always be to create the most functional limb. Within the field of limb salvage, when considering limb length versus function, physicians have prioritized preserving length, given data showing increased mortality and morbidity with higher level amputations.16 However, in some patients, one must sacrifice limb length to achieve the ultimate goal of a functional limb.
Inadequate perfusion can be secondary to a variety of etiologies. Common etiologies to consider are: smoking, microvascular disease (diabetes mellitus), macrovascular arterial disease (atherosclerosis), vasospastic disease (Raynaud’s disease), vasculitis (scleroderma, lupus) and venous insufficiency. The wide variety of clinical conditions affecting blood vessels leads to hypoxia of the tissue. Lower extremity wounds with transcutaneous oxygen tension (TcPO2) readings below 35 mmHg will not heal.11 Again, we reiterate the need for proper vascular workup and intervention to achieve adequate perfusion.
Assessing For Osteomyelitis And Soft Tissue Emphysema
Reasons to progress into surgical debridement include dry gangrene (necrotic tissue at risk for infection), wet gangrene (clinically infected ulceration), osteomyelitis or a chronic wound stalled in healing. A generally accepted concept is that clinical infection is the presence of purulent drainage or at least two of the signs of inflammation (erythema, warmth, tenderness, pain, induration).17 Upon examination, signs such as friable tissue, undermining, sinus/deep probing or malodor imply possible infection. Assess wound depth for tendon, joint or bone involvement.
Grayson and colleagues note that if a clinician can probe to bone, there is an 85 percent chance of osteomyelitis with an 89 percent positive predictive value.18 More recent literature by Lavery and coworkers reveals the probe to bone test may be more valuable in ruling out osteomyelitis.19 The article showed positive probe to bone only correlated to osteomyelitis 57 percent of the time but negative probe to bone correlated to 98 percent predictive value that there was no underlying osteomyelitis. Both studies strongly validate that deep probing correlates to worsening infection and possible osteomyelitis.
Outside of physical examination, it is important to include treatment objective parameters such as vitals, imaging and labs to drive management more accurately. Once a clinical infection invades systemically, we begin to see signs such as fever, tachycardia and leukocytosis, all indicating a severe infection requiring operative intervention. Evaluate white blood cell count, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). A substantially raised ESR (>70 mm/hr) suggests bone infection although studies show the sensitivity of this finding could be low.20
Always take radiographs and evaluate for osteomyelitis and soft tissue emphysema. It is important to remember that it can take up to three weeks for osteomyelitis to be visible on a radiograph.21 If soft tissue emphysema is present, it is imperative to take proximal radiographs to ensure the infection is not tracking up the leg. In addition, it is recommended to obtain a computed tomography (CT) scan to fully evaluate the soft tissue emphysema as this is a surgical emergency. If an operating room is not available, one should perform a bedside debridement immediately to decompress the wound until an operating room is available for formal debridement. Ideally, during any bedside procedure, one would make the incision with consideration for future operative flap planning.
Pertinent Techniques And Principles In Surgical Debridement
The single most important surgical step in treating any wound is adequate debridement to remove all foreign material and unhealthy/non-viable tissue until the wound edges and base consist only of normal and healthy tissue.21 The remaining tissue will become the basis for the wound healing process to progress normally.
One should take pre-debridement cultures at the start of the case. All infected ulcerations require antibiotics for a period of time and one should review the Infectious Diseases Society of America guidelines.17 After debridement, take postoperative cultures. The utility in taking both pre- and postoperative cultures lies in tailoring the antibiotics to specific bacteria. If post-debridement cultures return with no growth, the pre-debridement cultures will allow the infectious disease physician to choose the appropriate antibiotic while the post-debridement cultures will show the success of debridement.
Always use an atraumatic surgical technique to avoid damaging underlying healthy tissue. Damaging this tissue by crushing or burning may establish a nidus for bacteria to proliferate.21 For appropriate monitoring of bleeding, it is best not to inflate a tourniquet. When debriding skin, if the border between live and dead tissue is unclear, start at the center and remove concentric circles until you reach viable tissue. If there are clotted venules at the skin edge, this indicates complete interruption in the local microcirculation and the need for further excision.6 Viable skin will have punctate bleeding.
In the area of non-bleeding, nonviable skin, there is a high concentration of harmful proteases and bacteria inhibiting wound healing. If one does not surgically address this early, the slow course of liquefactive necrosis will cause dead skin to separate from the underlying healthy tissue, leading to loss of function, bad scarring, deeper tissue damage and disseminated infection.21 Therefore, we recommend removing all nonviable skin as soon as possible. Only when there is normal arterial bleeding at the wound edges can one be satisfied that the cutaneous debridement is adequate. All of these factors lead to the strong recommendation of wide excision during initial operative intervention.
The use of methylene blue dye is a technique we frequently employ at our institution to guide precise surgical debridement. We paint the dye over the entire wound bed before debridement. The methylene blue binds irreversibly to superficial cells of the wound base and any exposed crevices or tracks.13 Removing all the blue-stained tissue (through rongeur, curettage, hydrosurgical debridement, etc.) is a simple, visual method to ensure the entire wound surface has had debridement, including as many colonized cells from biofilm as possible.
Color plays an important role in surgical debridement. Remove all gray and black tissue. Healthy colors of note are yellow for subcutaneous fat, red for muscle and white for fascia, tendon or bone. Unlike skin, bleeding is not a reliable indicator for subcutaneous tissue. One should debride subcutaneous fat until the soft yellow color is visible. Similarly, if muscle viability is in question, only remove what is not bleeding as excess excision could compromise blood flow to the surrounding tissue.6
Tendon debridement can be difficult secondary to its correlation with function and the risk for spreading infection along tissue planes within tendon sheaths or fascial layers. Remove smaller tendons entirely if they are exposed or infected. Only excise the necrotic or infected portions of larger tendons. With any size tendon, examine the possible routes for infection spreading along the tissue planes. Similar to skin, non-bleeding and discolored bone are characteristic of necrosis. Debride bone until punctate bleeding (paprika sign) of cortical bone or normal appearing marrow of cancellous bone is apparent. Although biomechanical considerations are important, they should never deter the surgeon from ensuring the eradication of all osteomyelitis.
After surgical debridement, flush the wound with copious amounts of normal saline. There is no proven benefit to adding antibiotics to lavage fluid. Physicians most commonly use saline.6 Cysto tubing is preferable over pulse lavage to decrease the theoretical risk of driving any remaining bacteria into deeper tissue through higher pressures with pulse lavage. A double instrument set up with new instruments, gloves, drapes, suction and Bovie minimizes the risks associated with cross contamination. This extra step is based upon research by Attinger and Bulan, who showed that instruments clinicians use for debriding wounds have a residual concentration of bacteria >104 per gram of tissue.6 With new instrumentation, obtain post-debridement cultures as we explained previously.
We do not recommend closing/covering an infected wound upon initial debridement. Our institution utilizes serial debridement. In between debridements, negative pressure wound therapy or VAC Instill (Acelity) are good choices for temporary wound coverage.
When Is A Wound Clean Enough To Close?
When is a wound clean enough for permanent closure? Should cultures show absolutely no growth or is scant/rare growth clean enough? Elmarsafi and colleagues demonstrated that positive yet low growth cultures (scant/rare; growth in enrichment broth) did not affect overall dehiscence rates.22 This finding proves that successful coverage or closure does not necessarily rely on completely negative cultures.
Once wounds are clean, coverage/closure options are limitless from skin graft to free tissue transfer. Our institution is fortunate enough to have a strong team approach between podiatric, plastic and vascular surgery, allowing us access to complex surgical options not necessarily available at every institution. However, one can close more than 90 percent of wounds without resorting to complex podiatric surgical reconstruction or sophisticated plastic surgery techniques, providing that the wound is well vascularized and free of infection.6 Vacuum-assisted closure therapy has simplified wound care because it can stimulate formulation of granulation tissue, allowing wounds to become manageable in depth and width. This modality provides surgeons with the ability to close most wounds primarily or with a skin graft/biologic graft.
Final Notes
To reiterate, our primary goal as limb salvage surgeons is to heal any type of wound in a timely fashion with the highest possible functional outcome. Recognizing key features of a wound preoperatively, understanding when to operate and practicing appropriate surgical techniques will allow the podiatric surgical community the best chance to achieve this goal and provide patients with a functional ulcer-free limb.
Dr. Arneson is a second-year resident in the Division of Podiatric Surgery at MedStar Georgetown University Hospital in Washington, DC.
Dr. Elmarsafi practices in the Department of Plastic Surgery at MedStar Georgetown University Hospital in Washington, DC.
Dr. Kim is a Professor in the Department of Plastic Surgery at MedStar Georgetown University Hospital in Washington, DC. He is a Fellow of the American College of Foot and Ankle Surgeons.
References
1. Singh N, Armstrong DG, Lipsky BA. Preventing foot ulcers in patients with diabetes. JAMA. 2005; 293(2):217-28.
2. Pecoraro RE, Reiber GE, Burgess EM. Pathways to diabetic limb amputation. Basis for prevention. Diabetes Care. 1990; 13(5):513-21.
3. Kald A, Carlsson E, Nilsson E. Major amputation in a defined population: incidence, mortality and results of treatment. Br J Surg. 1989; 76(3):308-10.
4. Lavery LA, van Houtum WH, Armstrong DG, et al. Mortality following lower extremity amputation in minorities with diabetes mellitus. Diabetes Res Clin Pract. 1997; 37(1):21-27.
5. Faglia E, Favales F, Morabito A. New ulceration, new major amputation, and survival rates in diabetic subjects hospitalized for foot ulceration from 1990 to 1993: a 6.5-year follow-up. Diabetes Care. 2001; 24(1):78-83.
6. Attinger CE, Bulan EJ. Debridement: The key intial step in wound healing. Foot Ankle Clin N Am. 2001; 6(4):627-60.
7. Elmarsafi T, Garwood CS, Steinberg JS, et al. Effect of semiquantitative culture results from complex host surgical wounds on dehiscence rates. Wound Rep Reg. 2017; 25(2):210-16.
8. Cavanagh PR, Lipsky BA, Bradbury AW, Botek G. Treatment of diabetic foot ulcers. Lancet. 2005; 366(9498):1725-35.
9. Petre M, Tokar P, Kostar D, Cavanagh PR. Revisiting the total contact cast: maximizing off-loading by wound isolation. Diabetes Care. 2005; 28(4):929-30.
10. Rhodes GR, King TA. Delayed skin oxygenation following distal tibial revascularizations. Implications for wounds healing in late amputations. Am Surg. 1986; 52(3):519-25.
11. Burns JL, Mancoll JS, Phillips LG. Impairments to wound healing. Clin Plastic Surg. 2003; 30(1):47-56.
12. Attinger CE, Walcott R. Clinically addressing biofilm in chronic wounds. Adv Wound Care. 2011; 1(3):127-32.
13. Cornell RS, Meyr AJ, Steinberg JS, Attinger CE. Debridement of the noninfected wound. J Vasc Surg. 2010; 52(3 Suppl):31S–36S.
14. Wolcott RD, Kennedy JP, Dowd SE. Regular debridement is the main tool for maintaining a healthy wound bed in most chronic wounds. J Wound Care. 2009; 18(2):54–56.
15. Wolcott RD, Rumbaugh KP, James G, et al. Biofilm maturity studies indicate sharp debridement opens a time dependent therapeutic window. J Wound Care. 2010; 19(8):320–8.
16. Evans KK, Attinger CE, Al-Attar A, et al. The importance of limb preservation in the diabetic population. J Diab Complications. 2011; 25(4):227-31.
17. Lipsky BA, Berendt AR, Deery HG, et al. Diagnosis and treatment of diabetic foot infections. Clin Infect Dis. 2004; 39(7):885-910.
18. Grayson ML, Gibbons GW, Balogh K, et al. Probing to bone in infected pedal ulcers: A clinical sign of osteomyelitis in diabetic patients. JAMA. 1995; 273(9):721–3.
19. Lavery LA, Armstrong DG, Peters EJG, Lipsky BA. Probe to bone test for diagnosing diabetic foot osteomyelitis: reliable or relic? Diabetes Care. 2007; 30(2):270-274.
20. Karr JC. The diagnosis of osteomyelitis in diabetes using erythrocyte sedimentation rate. J Am Podiatric Med Assoc. 2002; 92(5):314.
21. Attinger CE, Janis JE, Steinberg JS, et al. Clinical approach to wounds: Debridement and wound bed preparation including the use of dressings and wound-healing adjuvants. Plas Recon Surg. 2006; 117(7 Suppl):72S-109S.
22. Elmarsafi T, Garwood CS, Steinberg JSS, et al. Effect of semiquantitative culture results from complex host surgical wounds on dehiscence rates. Wound Rep Reg. 2017; 25(2):210-216.
For further reading, see “Current And Emerging Debridement Options In Wound Care” in the December 2016 issue of Podiatry Today, “Current And Emerging Modalities In Wound Debridement” in the August 2013 issue or “Pertinent Insights On Effective Debridement Tools” in the September 2011 issue.
