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Lee J. Sanders, D.P.M.
06-15-2010
- Wound Healing: the body's natural process of dermal or epidermal tissue regeneration. Involves a cascade of events: activation of keratinocytes, fibroblasts, macrophages, platelets and endothelial cells. Healing consists of new epithelium, decreased area and depth of the wound and no drainage.
- Impaired wound healing (IWH): lack of orderly process of healing, associated with morbidity, amputations, mortality and health-care costs. IWH is associated with hyperglycemia and advanced glycation end products (AGE), decreased cell and growth factor response, and endothelial dysfunction with decreased local angiogenesis.
- Poor healing has impaired angiogenesis and vasculogenesis with reduced vascular endothelial growth factor (VEGF) . Bone marrow-derived endothelial progenitor cells (EPCs), essential for neovascularization, are decreased in DM. Keratinocyte and fibroblast migration and proliferation also decreased. Matrix metaloproteinases (MMPs) also play a major role in wound healing and are in excess in wound fluid.
- "The diabetic foot": refers to a constellation of pathological conditions (neuropathy, ischemia, ulceration, infection "the fetid foot", the Charcot foot, and gangrene) of which the diabetic foot ulcer (DFU) is the most characteristic.
- Failure of normal wound healing after cutaneous ulceration is the most prevalent component cause leading to amputation in 81% of cases (Pecoraro).
- Predisposing Factors: (1) abnormal cellular/inflammatory pathways, (2) peripheral neuropathy, and (3) ischemia. Hyperglycemia, advanced glycation end products (AGE) as well as physiologic impairments complicate the healing process. Ability to fight infection and to mount an adequate inflammatory response are impaired.
- Factors that negatively affect wound healing: diabetes, aging, obesity, malnutrition, decreased oxygenation of wound, smoking, and impaired renal function.
- Identify the causes of the wound: ischemia, neuropathy, minor trauma, callus, infection and/or foot deformities.
- Assess the need for hospitalization or outpatient treatment, and diagnostic tests (wound culture, metabolic panel, CBC with differential, radiographs and vascular studies).
- Assess wound: PEDIS - Perfusion, Extent/size, Depth/tissue loss, Infection, Sensation.
- Describe anatomic location, appearance, temperature, purulence and odor.
- Sterile probe to evaluate depth and extent of wound. Identify undermining of the skin edges, sinus tracts, abscess or penetration to tendon, bone or joint. Wound depth is important to outcome.
- Uninfected wounds may be remarkably asymptomatic, due to peripheral sensory neuropathy. Neuroischemic wounds are often painful, as are moderate to severely infected wounds.
- Cellulitis >2cm, lymphangitic streaking , deep-tissue abscess, gangrene, and involvement of muscle, tendon, joint or bone are signs of moderate infection.
- The presence of fever, chills, tachycardia, hypotension, confusion, vomiting, leukocytosis, acidosis, severe hyperglycemia, or azotemia indicate systemic toxicity and/or metabolic instability, characteristic of severe infection.
- Fundamentals: cleanse the wound (with sterile saline or wound cleanser); sharp wound debridement; appropriate wound dressing; adequate off-loading device; infection control; metabolic control; and revascularization of ischemic limbs.
- Wound debridement: sharp removal of callus and necrotic tissue. Maintenance debridement of chronic wounds is advised to "jump-start" the wound and keep it in a healing mode.
- Infection control: local (foot) and systemic (metabolic) issues; avoid antibiotics for uninfected ulcers, wounds lacking purulence or any manifestations of inflammation. Bacterial contamination and colonization of a wound does not constitute infection. For superficial ulcers, with infection target Staphylococcus aureus and streptococci with systemic antibiotics. Wound bioburden is best treated with wound cleansing and debridement.
- Off-loading: Relief of mechanical stress (pressure, shear and repetitive injury) on the foot to treat and prevent further insult ,using total contact cast (TCC) (the gold standard), instant TCC (iTCC), removable cast walkers (RCWs), Scotch cast boot, crutches and wheel chairs.
- Dressings: Select according to the characteristics of the wound (dry, exudative, infected, necrotic, partial or full thickness). There is no single best dressing for all wounds, and type of dressings may change throughout the process of wound healing.A physiologic moist wound environment promotes epithelialization of the wound and helps to prevent desiccation. Dressings serve as a barrier to the external environment, prevent further trauma, minimize the risk of infection and optimize the wound milieu.
- Advanced therapies: Topical growth factors (PDGF-BB), protease inhibitors, bioengineered skin substitutes. Cryopreserved human skin allografts and living skin equivalents serve as biologic dressings, contributing growth factors, cytokines and collagen to the wound.
- Negative Pressure Wound Therapy (NPWT): an open-cell foam dressing covered with an adhesive drape, connected to a vacuum pump, creating sub-atmospheric pressure. Most commonly used device is the Vacuum Assisted Closure (V.A.C.) (KCI, San Antonio, Texas, USA). Negative pressure wound therapy is widely applied, although the evidence base is weak.
- Footwear and Orthoses: Before wound has healed evaluate for appropriate footwear, orthoses and braces.
- Key points: off-load high pressure areas, accommodate foot deformities (hammertoes, bunions, prominent metatarsal heads, midfoot collapse and partial foot amputations) and brace instability of the foot/ankle. Therapeutic footwear and/or braces should be available to patients once wounds have healed and before resuming full weight-bearing .
- See "more" table for properties and indications for passive, active and biologic wound care products.
- Longer duration wounds are less likely to heal.
- Impaired renal function and dialysis are important predictors of long-term outcome.
- Percent change in foot ulcer area at 4 weeks' observation is a powerful predictor of healing at 12 weeks.
- Cost, duration of treatment and potential risk of infection and amputation highlight critical role of treating poorly healing wounds.
- Chronic wounds are more likely to become infected, require hospitalization/surgery and to incur increased costs.
- Patients with peripheral sensory neuropathy should be continually reminded of the implications of sensory loss and associated risks of recurrent ulceration, infection and amputation.
- Multidisciplinary team management, with early detection and intervention, patient education and close monitoring, is the key to prevention and treatment of diabetic foot wounds.
- Note: literature reviews provide a weak level of evidence for the clinical efficacy or superiority of different wound care products. Silver impregnated wound dressings and topical agents for the treatment of DFUs are expensive. Cell-derived wound care products in addition to standard care generate very high costs. High costs may be offset by higher healing rates and shorter treatment periods.
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