Risk Factors for Diabetic Foot Ulcers: The First Step in Prevention
ABSTRACT: Approximately one-third of diabetes treatment costs in the United States are spent on treating diabetic foot ulcers. This article discusses risk factors that primary care practitioners can use for early diagnosis. Remember, the first step to prevention is patient education. The more information you can provide your patient, the better they understand the condition and adhere to treatment.
“Preventing ulcer recurrence may be the most important topic in diabetic foot disease,” said Peter Cavanagh, PhD, DSc, professor and vice chair for research in the department of orthopedics and sports medicine at the University of Washington Medical Center in Seattle.1
About 26 million Americans, representing 8.3% of the total US population, have diabetes.2 In 2007, the total costs of treating patients with diabetes was an estimated $14 billion.3 At least one-third of these costs were associated with the treatment of diabetic foot ulcers (DFUs).4
Approximately 85% of lower limb extremity amputations are preceded by non-healing foot ulcers.5 We believe that a high percentage of these problems are preventable by recognizing the major risk factors that lead to DFU and implementing 4 essential measures to prevent these wounds from occurring.
Defining the Condition
DFUs might connote superficial problems while diabetic foot wounds are deeper problems; we consider the terms interchangeable. DFU is the preferred terminology. As different DFU classification systems indicate, presentation can range from superficial, partial skin ulcerations to deep abscesses, bone infection, and necrotic tissue. From another perspective, wounds often suggest a direct traumatic cause while DFU is a spontaneous occurrence. In reality, both derive from trauma with traumatic wounds usually occurring with a single event and DFU most frequently as a summation of repetitive subthreshold (for direct wound formation) stresses.
Risk factors that are predictive and/or precursors of DFU include direct and indirect causes (Table 1).6 For example, deformities are a direct cause of DFU. Deformities develop from a multitude of reasons including joint contractures, clawing of toes, spurs, bunions, bunionettes, extrusions of bones (as in Charcot neuroarthropathy), malunited fractures, and arthridities. Clawed toes, repetitive shear stresses, and trauma are other conditions that can be direct causes of DFU.
Indirect causes of DFU lead to wounds through secondary processes. For example, patients with diabetes with sensory neuropathy may disregard callus formation over deformities because no pain is associated with pressure being placed on the callus. Without attention to removing the deformity and/or debulking the callus, an ulcer frequently develops with continuing loading (ie, weight bearing) over the sites. Enzymatic glycosylation of soft tissues reduces the elasticity of tissues as well as soft tissue padding, and is another indirect cause of DFU.7 With loss of elasticity and padding, wounds are likely to occur with repetitive minimal stresses or constant pressure. However, they would not ordinarily occur if the tissues were normal. Most DFU occur because of a combination of indirect and direct causes. Direct causes make the sites more vulnerable to wound formation, and the indirect causes delay management and/or attenuate the healing/wound prevention processes.
Deformity, peripheral artery disease, peripheral neuropathy, previous foot wound, and/or a prior amputation are risk factors predictive of new or recurrent DFU (Table 2).8-10 The more risk factors that are present, the more likely DFU will occur.7,11,12 Within 1 year of wound healing following DFU, up to 60% of patients with a previous DFU history will develop a recurrent wound.13,14 Reasons for this include failure to implement preventive measures as well as the wound site being more vulnerable to reinjury due to less resiliency and elasticity of scar tissue, abnormal mechanics from tissue loss with amputations and debridements, or combinations of these. Hence, this healed ulcer group presents a dichotomy; it has the highest risk for developing new or recurrent ulcerations and conversely is the easiest group to recognize the risk factors.7,15
This is the target group that will especially benefit from the DFU preventative measures. The primary care physician (PCP) or qualified care provider (eg, nurse practitioner, physician assistant, wound and ostomy care nurse, and/or home health caregiver) usually has the initial contact with patients with diabetes. Consequently, health care providers are crucial in recognizing and discussing the risk factors, initiating preventative measures, and referring patients to surgeons for wound and surgical management for their patients at risk.
Other risk factors contribute to the development of DFU. These include smoking, diabetes, malnutrition, immobility, older age, deficits in cognitive function, lack of insight, and inability to follow optimal management (such as lower extremity elevation) because of other significant comorbidities (Table 3). Smoking is known to have negative effects on wound healing outcomes and essentially doubles the complication rate for any surgery or wound healing intervention as compared to nonsmokers.16
Metabolic syndrome is another risk factor for development of foot ulcers. It includes a combination of hypertension, abdominal obesity, hyperglycemia, dyslipidemia (hypertriglyceridemia and low high-density lipoprotein), and is a precursor of diabetes.17 The primary and associated risk factors are additive for developing DFU; that is, the more that are present, the more likely a wound problem will arise. Consequently, it is crucial that the PCP recognize these issues and initiate appropriate management before a problem arises. Improper management can lead to serious and costly wound care problems, especially with DFU.
The first step in any preventive care is patient education, and the PCP role is crucial. All patients with diabetes need a PCP to supervise their medical management and initiate referrals to specialists for selection of higher order protective footwear and surgeries. Sir William Osler’s maxim “it is better to know the patient than the disease” epitomizes our philosophy that for successful DFU prevention, the caregiver must appreciate how well the patient will follow instructions. If to the point of being almost obsessive-compulsive, follow-up visits can be widely spaced; however, if the patient is almost oblivious to management recommendations, very frequent follow-ups are needed to prevent DFU.
Next month we will highlight the 4-pronged approach of patient education, foot skin and toenail care, appropriate footwear, and proactive surgical interventions to effectively prevent new and recurrent diabetic foot ulcers. ■
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Lisa Nhan, DPM, is a third year podiatric surgery and medicine resident with special interest in forefoot reconstructive surgery and diabetic limb salvage at Long Beach Memorial Medical Center, Long Beach, California. She is also a co-investigator on a comprehensive wound scoring research project with Drs Strauss and Miller.
Michael B. Strauss, MD, is an orthopaedic surgeon who focuses on managing limb threatening wounds is the medical director of Hyperbaric Medicine at Long Beach Memorial Medical Center, a clinical professor of orthopaedic surgery at the University of California Irvine and orthopaedic consultant for the Foot & Ankle Clinic at the Veterans Affairs Medical Center, Long Beach, California.
Stuart S. Miller, MD, is the associate medical director of Hyperbaric Medicine at Long Beach Memorial Medical Center, is an emergency medicine physician and has co-authored over 30 articles, book chapters, posters, and a wound care textbook with Dr Strauss.