Examining The Evidence For Preventing Diabetic Foot Ulcers
When it comes to patients with diabetes and lower extremity ulcers and complications, what does the evidence-based medicine say about high-risk patients and proactive prevention? These panelists examine risk factors for ulcerations, appropriate screening and offer their thoughts on what works and what does not work in terms of prevention.
Q: What does evidence-based medicine show in regard to who is at risk for limb loss and foot ulcerations?
A: Thomas Zgonis, DPM, says approximately 15 percent of patients with diabetes will experience a diabetic foot ulcer (DFU).1,2He says some of the most significant risk factors for DFUs and subsequent lower extremity amputations (LEA) are multiple systemic complications that are caused by chronic hyperglycemia. Citing different studies, Dr. Zgonis says significant predictors for the development of a DFU include poor glycemic control, impaired vision, progressive foot deformities with abnormal pedal pressures and minor repetitive trauma to the insensate foot.2-5
Dr. Zgonis, Nicholas Bevilacqua, DPM, and Kazu Suzuki, DPM, cite peripheral arterial disease (PAD) as a predictor for ulceration. Dr. Bevilacqua says PAD is a part of the University of Texas Diabetic Foot Risk Classification, the levels of which range from risk category 0 (patients with diabetes but no neuropathy or PAD) to level 3 (patients with a history of ulceration, amputation or Charcot foot).6
However, Dr. Bevilacqua says this classification system may have undervalued PAD. Lavery, et al., modified the University of Texas system and he says their classification includes PAD but not deformity.7
“This modified classification system predicts future foot complications better than the previous one,” says Dr. Bevilacqua.
Peripheral arterial disease and critical limb ischemia (CLI) are “by far” the major cause of limb loss in the United States, according to Dr. Suzuki. He cites data from the Trans-Atlantic Inter-Society Consensus (TASC-II) guideline 2007, which notes that risk factors for developing CLI (and subsequent limb loss) are diabetes (a fourfold risk), smoking (a three-fold risk), and age over 65 (twice the risk).8
In regard to patients with risk factors for PAD or leg complains (fatigue, cramps, claudication), Dr. Suzuki says the TASC-II guidelines encourage physicians to evaluate leg pulses and utilize “objective testing” such as ankle brachial index and skin perfusion pressure. TASC-II also advocates objective testing for PAD in “all diabetic patients with an ulceration,” according to Dr. Suzuki. He adds that the TASC-II guidelines also emphasize PAD testing for suspected CLI patients with rest pain and pedal ulcers, including gangrenous toes.8
Dr. Suzuki also emphasizes the TASC-II conclusion that, “Early identification of patients with PAD at risk of developing foot problems is essential for limb preservation. This can be achieved by daily visual examination by patient or (his or her) family and, at every visit, referral to the foot specialist.”8 Similarly, Armstrong, et al., suggested that up to 85 percent of amputation may be prevented by early detection and appropriate treatment of foot ulcers.9
A history of previous ulceration or amputation is another risk factor for ulceration and limb loss, according to Dr. Zgonis, Dr. Bevilacqua, Lawrence Karlock, DPM, and Geoffrey Habershaw, DPM.10
Dr. Zgonis also notes that patients with diabetes are about 15 to 40 times more likely of undergoing a non-traumatic LEA compared to non-diabetic patients.2,11 Certain ethnicities, older patients and male patients are also at higher risk, according to Dr. Zgonis.2,3,12,13
Dr. Karlock cites research by Pham, et al., who concluded that the clinical exam and the 5.07 Semmes-Weinstein monofilament test were the two most sensitive tests for identifying patients at risk for ulceration.14 He notes the study also concluded that foot pressure measurements offered a high degree of specificity and one can use them as a post-screening test along with providing appropriate footwear.14
Dr. Habershaw concurs, noting that evidence-based medicine says patients are at risk for ulceration and limb loss if they have clinically diminished protective sensory loss via screening with a Semmes-Weinstein 5.07 filament, 10 years or more of diabetes, poor glycemic control, a history or symptoms of vascular disease, extremity bypass, endovascular surgery or impaired vision. He says other risk factors include: structural abnormalities such as calluses, hammertoes, pes planus/ cavus, or bunions; reduced joint mobility; dry or fissured skin; chronic tinea; or severe onychomycosis.
Greg Mowen, DPM, cites evidence from the Center for Lower Extremity Ambulatory Research (CLEAR), which developed a foot risk classification system and treatment recommendations that rank patients from 0 (no loss of protective sensation) to 3 (prior ulceration or amputation).
Q: What does the evidence show about what works for foot ulcer prevention in patients with diabetes?
A: Home foot temperature monitoring can be effective in preventing ulcers, according to Dr. Bevilacqua. He notes a study by Armstrong, et al., in which the dermal thermometry group underwent monitoring with an infrared thermometer that measured temperatures on the sole of their foot. Temperatures of >4º F were considered to be “at-risk” and Dr. Bevilacqua says researchers found subjects were one-third as likely to ulcerate in the dermal thermometry group in comparison to the standard therapy group.15
Furthermore, Dr. Karlock cites Lavery’s 15-month multicenter study, in which patients had standard footcare, education and footwear were 4.37 times more likely to develop foot ulcers in comparison to those who underwent skin temperature monitoring.16
The panelists also emphasize the importance of a multidisciplinary team approach in preventing ulcers.2 Dr. Habershaw cites the efficacy of routine, regular follow-up visits and care at a “team-oriented” diabetes care center. He says this team would include endocrinology, vascular medicine and surgery, podiatry, nutrition, exercise counseling, eye care and a diabetes teaching nurse. Specifically for podiatry, he notes the importance of routine foot care, monitoring of shoes and orthotics, skin care, and education about foot self-care. Dr. Zgonis says specialist teams can educate patients and family members on properly managing glucose, the importance of foot care and the prompt recognition of sores or pre-ulcerative lesions.
When the skin becomes compromised, he says early, aggressive treatment is essential. Offloading, infection control, vascular workup, metabolic control of glucose, heart, renal and nutrition care are a part of his care regimen. Dr. Habershaw says continued ulcer deterioration warrants early surgical intervention whether it is vascular, reconstructive or both.
Dr. Zgonis cites evidence in the literature showing that preventing diabetic foot ulcers starts with the screening measurements for neuropathy and peripheral vascular disease.17,18 In addition, he notes that researchers have also shown that preventive care increases the survival rate and reduces the rate of ulcerations in patients with diabetes.2,19,20
Dr. Mowen thinks most doctors will do more screening for LOPS and PAD. He says DPMs usually have taught patients to do self-inspection with the use of a mirror and even self sensory evaluation with 5.07 monofilaments. Along these lines, he notes early intervention and offloading of “problem” or “pre-ulcerative” areas have been at least anecdotally beneficial.
Q: What does not work for foot ulcer prevention in patients with diabetes?
A: Dr. Suzuki does not like “white 100 percent cotton socks” that DPMs commonly recommend for patients with diabetes, although he does note that the white color identifies bleeding and drainage. He suggests using moisture-wicking material (synthetic blend or specific wool material such as “cool max” or “smart wool”) and sheer-force reducing multilayer socks with no seam, which should prevent blisters that lead to foot ulcers. Dr. Suzuki also notes the “X-Static” silver antimicrobial socks. He says the silver fiber in these socks decreases the skin flora and goes to the wound immediately when the skin is damaged.
Failing to prevent diabetic ulceration usually results from a delay in diagnosing an underlying risk factor, according to Dr. Zgonis. He says factors that may help prevent the healing of a recalcitrant wound include underlying infection, tissue hypoxia, biomechanical abnormalities and systemic factors.2
Q: What evidence do we have about diabetic shoes and insoles in the prevention role?
A: “The idea of therapeutic diabetic shoes being the answer of DFU prevention is a misconception practiced by many practitioners,” argues Dr. Zgonis. “There is no consistent supporting evidence suggesting that therapeutic shoes and inserts dispensed freely to patients with diabetes mellitus will prevent skin breakdown.”
Dr. Zgonis notes that researchers have shown that thorough foot inspections and proper foot care by healthcare professionals are more effective than therapeutic footwear.21 However, he says in patients with previous foot amputations or severe structural deformities, therapeutic footwear has shown promising results.22 Although some studies do support that inappropriate footwear is a precipitating factor for ulcerations in high-risk patients, Dr. Zgonis emphasizes that the evidence supporting ulcer prevention with therapeutic shoes and insoles in all patients with diabetes is inconsistent.21,22
“This does not imply that therapeutic footwear and orthotic management is not beneficial,” maintains Dr. Zgonis. “It simply implies that it needs to be individualized and overseen by a healthcare professional who is knowledgeable in the diabetic foot.”
Dr. Mowen is likewise skeptical of the evidence on diabetic shoes since amputation rates continue to rise.
Dr. Bevilacqua is an attending surgeon at the Foot and Ankle Clinics at Broadlawns Medical Center in Des Moines, Iowa.
Dr. Habershaw is an Assistant Professor of Surgery at Boston University School of Medicine, and is the Chief of Podiatry at Boston Medical Center.
Dr. Mowen runs a lower extremity neuropathy clinic in Ventnor, NJ. He is board certified in podiatric orthopedics and primary podiatric medicine. He is an Associate Member of the Academy of Ambulatory Foot Surgeons, and is a Member of the Fellowship of Peripheral Nerve Surgeons.
Dr. Suzuki is the Medical Director of the Tower Wound Care Center at Cedars-Sinai Medical Towers in Los Angeles. He is a consultant, researcher and lecturer on wound care and limb salvage in the U.S. and in Japan. The author can be contacted via e-mail at firstname.lastname@example.org.
Dr. Zgonis is an Assistant Professor in the Department of Orthopaedics/Podiatry Division and the Director of the Reconstructive Foot and Ankle Fellowship at the University of Texas Health Science Center at San Antonio. He is a Fellow of the American College of Foot and Ankle Surgeons.
Dr. Karlock is a Fellow of the American College of Foot and Ankle Surgeons, and practices in Austintown, Ohio. He is the Clinical Instructor of the Western Reserve Podiatric Residency Program in Youngstown, Ohio. Dr. Karlock is a member of the Editorial Advisory Board for WOUNDS, a Compendium of Clinical Research and Practice.
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