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The medical literature provides a range of evidence on which to base treatment decisions regarding care of the diabetic foot, but the practitioner must interpret and evaluate that evidence in the context of his or her own clinical expertise.

By Cordell Atkins, PT, DPT, CWS, CDE, CPed

Since the early 1990s evidence based medicine has been an interesting topic of conversation in the medical community. Evidence based medicine has been used to seek guidance on the safest and most effective treatments for a variety of illnesses and diseases, reduce needless disabilities and loss of function, and reduce wasteful expenditures by third party payers and patients.

So what is evidence based medicine? In 1996, David L. Sackett, MD, wrote: “Evidence based medicine is the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients. The practice of evidence based medicine means integrating individual clinical expertise with the best available external clinical evidence from systematic research.”1 Evidence based practice integrates relevant, reliable, pertinent, and trustworthy research information with clinical expertise and the patient’s specific needs and problems.

Levels of evidence

Evidence based care often requires searching published sources for evidence to help direct and guide care for the specific clinical question. Sources are often obtained from searches in databases such as PubMed, EBSCO, Cochrane Collaboration, association resources or collections, government sites, and other electric resources. The clinician or practitioner must be able to evaluate the evidence obtained for its usefulness, importance, and validity as related to the specific clinical question.

There is a hierarchy of evidence used to rank the strength and validity of the evidence from expert opinion to systematic reviews and meta-analyses (see table 1). Randomized controlled trials (RCT) assess the efficacy of an intervention. Efficacy is the capacity or power to produce an effect. (Levels I and II)  Observational studies, cohort, case control, case series and case reports address effectiveness—the quality or amount of the effect in practice, outside the laboratory or other controlled environment. (Level III).  Evidence from expert committees, opinions or clinical experience may introduce bias in the evidence (Level IV).

The clinician or practitioner can incorporate the published evidence, the individual patient’s needs or problems, and their own clinical expertise to develop a plan of care. Additionally, clinical guidelines or algorithms may be available to assist in care planning. These guidelines are generally developed by a multidisciplinary team with support from professional organizations, institutions or governmental agencies that publish the guidelines. The American Diabetes Association; the American College of Foot and Ankle Surgeons; the Wound, Ostomy, Continence Nurses Society; the American Pharmaceutical Association; the American Orthopedic Foot and Ankle Society; the International Working Group on the Diabetic Foot and the Infectious Diseases Society of America have all developed diabetic foot ulcer guidelines as a resource for clinicians and practitioners.

Guideline development is generally accomplished by a group of stakeholders concerned and interested in a certain clinical question or condition. The group will identify and gather evidence, assess the evidence for relevance, summarize and categorize the evidence and then translate the evidence, or lack of evidence, into clinical practice guidelines. As the evidence is being interpreted, the opinion of the group will be needed to create recommendations in the absence of evidence, or to assess other  issues such as the generalizability of the evidence2–for example, whether the results of a small RCT can be applied to a large population. Additionally, the opinions or conclusions of a speciality group may differ from that of a multidisciplinary group when presented with the same evidence. The multidisciplinary group tends to represent a more deversified viewpoint.

In a study published in 1998, Schuster reported that 30% to 40% of patients were not receiving care directed by evidence based guidelines and 20% to 30% were receiving care that was inappropriate, unnecessary, potentially dangerous or contraindicated.3 These data unfortunately demonstrate that there appears to be a gap between evidence based research and application in actual clinical practice.

Diabetes

According to the Centers for Disease Control and Prevention 2007 statistics,4 23.6 million people in the U.S. have diabetes. Unfortunately 5.7 million are undiagnosed. Complications of diabetes include heart disease, stroke, high blood pressure, blindness, kidney disease, nervous system disease, amputation, and dental disease.

Appropriate diabetic care can reduce the occurrence of diabetic complications. The Diabetes Control and Complications Trial (DCCT) demonstrated that tight glycemic control can reduce the occurrence of complications and even slow the progression of existing complications.5-12 In a follow up study of the original DCCT study, it was shown that the effects of early tight glycemic control demonstrated positive effects on neuropathy more than 10 years later.13 With regard to clinical practice, the newly published evidence strongly indicates that tight glycemic control should be the initial intervention for the care and prevention of diabetic complications and especially neuropathic complications.l3

The diabetic foot

In spite of all the published evidence for care and prevention of diabetic complications, these complications continue. More than 60% of all non-traumatic amputations occur in patients with diabetes. In the U.S. in 2004 there were approximately 71,000 lower extremity amputations in people with diabetes.4 According to the International Diabetes Federation, an amputation in a person with diabetes occurs every 30 seconds worldwide.14

Preventive foot care

Benjamin Franklin’s old saying “an ounce of prevention is worth a pound of cure” is probably very appropriate when discussing diabetic foot complications. Effective preventive care and management of the diabetic foot relies on assessment and risk identification. To prevent foot complications, it is essential to identify, assess, and screen those at risk. Several publications have confirmed this requirement for proper care of the diabetic foot and diabetic foot ulcerations.15-19

Everyone with diabetes should have an annual foot exam. The initial screening allows the clinician to examine and asses the foot for loss of protective sensation (LOPS),20-22 bony deformities, joint mobility, peripheral circulation, skin integrity, and callus formation. Gait and balance should also be evaluated. Many people with diabetes are at a low risk for foot ulceration while others may be classified as high risk.23,24 Those at high risk may have LOPS, foot deformities, peripheral arterial disease (PAD), or a history of previous foot ulcers. Table 217 demonstrates the risk categories with their definitions, treatment recommendations, and suggested follow-up visits for foot examinations that were developed by a multidisciplinary Task Force of the Foot Care Interest Group of the American Diabetes Association, with endorsement by the American Association of Clinical Endocrinologists.

Diabetic foot ulcers

Even with good preventive care, diabetic foot ulcers may occur. Published literature demonstrates that diabetic foot ulcers are a result of either PAD and/or diabetic peripheral neuropathy, with additional causative factors such as bony deformities, callus buildup, and trauma.25-28 The lifetime risk of foot ulceration in an individual with diabetes is about 15%.29 The published two-year cost of caring for a diabetic foot ulcer in 1999 was about $28,000.30

Evaluation

A key component of providing evidence based care is a thorough and comprehensive evaluation of the foot and the ulcer including a patient history and physical examination.17 The evaluation has several components that provide data to the clinician. It should include a vascular assessment to rule out arterial disease31,32 and a neurological assessment to assess LOPS.33 Additional laboratory tests that may assist the clinician in the assessment could include a prealbumin test to assess protein deficiency,34 a lipid profile to assess risk for developing cardiovascular disease,35 and, if not already ordered by the primary care physician, a hemoglobin A1c test.36 The data gathered, combined with applicable published evidence and clinician expertise in assessing the patient’s specific needs, should lead to optimal care for the patient.

Infection, debridement and wound care

Infection occurs when bacteria is greater than the host defense mechanism. The classic signs of soft tissue infection are redness, heat, pain, and swelling. Many individuals with neuropathy may have an impaired neuroinflammatory response and may not have the normal physiological response to pain. Other methods may be needed to assess for infection. Additional symptoms may include but are not limited to exudates, delayed healing, friable or discolored granulation tissue, foul odor, and wound breakdown.37 The use of erythrocyte sedimentation rate (ESR) and C-reactive protein as markers for bone infection, or osteomyelitis, has been supported by recent evidence.38,39

Necrotic and devitalized tissue is a source of bacterial growth and reduces the body’s ability to fight infection. Debridement and removal of the nonviable tissue help the diabetic ulcer to heal more rapidly.40,41 Diabetic wounds tend to be chronic in nature, and it is important to have a proper wound bed for healing. The goal of debridement is to convert the stagnant chronic wound bed of the diabetic ulcer into an active, acute wound by removing all necrotic, dysvascular, nonviable tissue to obtain a red granular wound bed.42 The most effective treatment of an infected bone is debridement of the infected bone, followed by an adequate course of antibiotics.43,44 Thorough surgical debridement has been shown to be effective in wound healing, and other methods such as enzymatic, mechanical, biological, or autolytic debridement may be appropriated depending on the status of the wound, the patient condition, or professional licensing restrictions.45-48

After the wound has been debrided and cleaned, it is necessary to maintain an environment that facilitates continued wound healing. Studies published in the 1950s and ‘60s by Odland,49 Winter,50 and Hinman and Maibach51 demonstrated that a clean, moist, occluded wound healed more rapidly than a wound left open to the air. Continued research has supported moist wound healing.52,53 An appropriate dressing should allow for moist wound healing but should also provide protection to the periwound area; reduce physical trauma, friction and shear; protect from external contamination; and, in today’s economic environment, be cost effective.54-57

Offloading the wound

Diabetic foot ulceration may be a result of increased pressure on the foot due to foot deformity, decreased joint mobility, or neuropathy. Pressure reduction in the area of high pressure, or offloading, has been the mainstay in preventing and healing diabetic neuropathic ulcers.58-61 Pressure relief is essential to maximize the healing potential of a diabetic wound. It has been said “it’s not what you put on the wound, it’s what you take off“62 that facilitates healing in diabetic neuropathic wounds.

Crutches, walkers, wheelchairs, custom shoes, custom inserts, Charcot Restraint Orthotic Walker (CROW) boots, relief boots and total contact casting have been used and are acceptable methods of offloading the diabetic foot.63,64 Of all the offloading techniques, none has been studied more than the total contact cast (TCC). Another method, the instant total contact cast (iTCC),65 has demonstrated success in healing wounds using the principle of pressure offloading 24/7, as with the total contact cast.

Not all patients are good candidates for the TCC or the CROW boot, both the TCC and the CROW tend to be somewhat large and heavy. Individuals of smaller stature or even the morbidly obese may find these difficult to use. Other devices, such as a below knee walking boot, or CAM (controlled ankle motion) walker, have been successful for pressure offloading in patients who cannot easily tolerate the TCC. The major success, wound closure, comes when the patient wears the boot 24/7 as with the TCC.

Adjuvant agents and hyperbaric oxygen

Adjuvant agents have been divided into topical agents, devices to accelerate healing, and systemic agents for patient treatment.

Topical agents that have demonstrated positive research outcomes in the care of the diabetic foot ulcer are platelet-derived growth factor (PDGF)66-68 and other cytokine growth factors.69-71 The use of these topical agents can be expensive, and not all third party payers are willing to cover the costs.

Devices that have been evaluated and have demonstrated a positive and sustainable improvement in diabetic foot wounds are negative pressure wound therapy (NPWT), and electrical stimulation.  NPWT has also been called vacuum-assisted wound closure. NPWT aids in wound healing by reducing edema, removing excess fluid and bacterial products and assisting to draw the edges of the wound together by a vacuum effect under the dressing.72-74 Use of NPWT can be expensive and not all payers provide coverage for the device. In addition, there are some contraindications for its use, including untreated osteomyelitis and inadequate debridement.75

The use of electrical stimulation may be beneficial in diabetic wound healing by affecting protein synthesis, cell migration and reduction of bacterial growth.76,77 The electrical stimulation waveform that has the most evaluation and use in wound care is monophasic high-voltage pulse current (HVPC).  HVPC devices provide polarity selection and a variation of the pulse width that appear to be important in wound healing.78 Two methods have been reported in the literature for application of the electrodes in wound healing.79,80 Electrical stimulation is contraindicated in cases of malignancy, evidence of osteomyelitis, cardiac pacemaker, and electrode placement over or near the phrenic nerve, carotid sinus or laryngeal musculature. The Centers for Medicare and Medicaid Services (CMS) coverage policy81 states that electrical stimulation is covered for diabetic ulcers when used as adjunct to standard wound therapy and not as an initial treatment modality, and when the patient has undergone at least 30 consecutive days of treatment with standard wound therapy with no measurable signs of healing.

Hyperbaric oxygen therapy (HBOT) is the medical use of oxygen at a level higher than atmospheric pressure. HBOT increases the partial pressure of oxygen in all the tissues of the body.  The systemic use of oxygen requires a doctors order as oxygen is considered a drug. HBOT used as a systemic agent has been associated with a reduction in amputation rates in patients who were at risk of below knee or above knee amputation due to severe ischemia, underlying osteomyelitis, or both.82 The Wound Healing Society has given HBOT a level I evidence rating in their “Guidelines for the treatment of diabetic ulcers.”49 CMS has established guidelines for reimbursement for the use of HBOT83 in the care and treatment of diabetic foot wounds:

  • Type 1 or Type 2 Diabetes Mellitus, with lower extremity wound due to DM
  • Wagner grade III or higher
  • Failed standard wound care (no measurable signs of healing for 30 days)
  • Wound must be re-evaluated every 30 days during HBOT course
  • Continued HBOT will not be covered if there are no measurable signs of healing during the 30 day period.

Conclusion

Providing evidence based care for the diabetic foot requires the clinician to integrate personal clinical expertise with the best available external clinical evidence from systematic research while assessing what is best for the patient’s specific needs and problems. Because diabetes and diabetic foot care is such a large concern socially, emotionally, and financially, a great deal of research has been done and will continue to be done to resolve the underlying disease and complications. The truly concerned clinician will have to continue to keep abreast of the most current, relevant, reliable, and pertinent research and care guidelines to provide the best evidence based care.

There are many more evidence based articles to support the care of the diabetic foot than those referenced in the preceding text. Table 3 provides a partial list of additional references, with the associated level of evidences, for the care of the diabetic foot.

Cordell “Corky” Atkins PT, DPT, CWS, CDE, CPed, is the manager of the Intermountain Diabetic Foot Clinic in Salt Lake City, UT.

References

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