Current Concepts In Treating Diabetic Foot Wounds
- Volume 16 - Issue 3 - March 2003
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What Is The Current Thinking About Appropriate Workup?
Plain X-rays may reveal lytic changes suggestive of osteomyelitis or a necrotizing infection with gas-forming organisms. A three-phase bone scan screens for osteomyelitis, but be aware that current radiopharmaceuticals cannot distinguish accurately between bone infection and soft tissue inflammation.8 Obtaining an MRI may give you useful information about depth of invasion, bone and joint involvement, and associated deformities.9 In one retrospective study, researchers identified abscesses on MRI in 18 percent of patients with osteomyelitis.10
When it comes to assessing the hemodynamic significance of vascular insufficiency, keep in mind that the ankle-brachial pressure index (ABI) is notoriously inaccurate in diabetic patients who have calcification of the arterial media. This calcification prevents compression and causes a falsely elevated index.
On the other hand, when you obtain a pulse volume recording (PVR) using a segmental air plethysmograph, it is not affected by calcification and gives a good indication of the hemodynamic significance of arterial disease. Measuring the transcutaneous oxygen tension (TcPO2) can be useful in some cases. A value over 30 mm Hg suggests the wound is likely to heal.
When arterial imaging is required for imaging atherosclerotic disease, consider magnetic resonance angiography (MRA) with gadolinium enhancement rather than contrast angiography. After all, radiographic dye is associated with higher risk of renal failure in diabetic patients. However, if contrast angiography is required, remember to institute nephroprotection with hydration and acetylcysteine, and to use a hyposmolar contrast agent.
Wound cultures can help you decide about appropriate antibiotic therapy for infected wounds. It has been said that a deep tissue biopsy provides more useful results. However, one study suggests that deep biopsy is no more accurate than superficial swab culture except for wounds that have been infected for over 30 days.11 This study also notes anaerobes are unlikely to grow beyond the first two weeks of antibiotic treatment. After 30 days, gram-positive bacteria predominate.
What You Should Know About Treatment
Management requires a team approach.12 There are an array of treatments and key considerations in their use.
• One key is to treat any infection, which is often polymicrobial.
• Remember that offloading is vital and can be accomplished by applying felted foam (for plantar relief reduction) or emphasizing an accomodative dressing, healing shoe, walking splint, crutch-assisted walking or sometimes bed rest. Offloading with total contact casting or non-removable fiberglass proved to be more effective than removable casts or shoes in one study and equally effective in another study.13
• Perform debridement. This may entail abscess drainage, ostectomy, removing callus, exploring undermined areas and removing hidden necrotic tissue.
• Use wound dressings that encourage epithelialization such as hydrophilic, alginate and silvadene. Hydrogels seem to be particularly effective.14
• Consider using an FDA-approved topical growth factor. In particular, using a platelet-derived growth factor-BB (PDGF-BB) protein in a cellulose gel (Regranex, becaplermin) achieved a 44 percent healing rate versus 22 percent in the control group in one study.15 However, the cost of this product may be prohibitive for many patients.
• Consider performing an excision and random flap closure as a single stage procedure for carefully selected, well-vascularized and very clean ulcers.16
• Consider split thickness skin grafting (STSG) or the use of cultured human dermis (Dermagraft) for intractible but clean wounds.
• Don’t forget the importance of glycemic control. Hyperglycemia impairs leokocyte function.