Vol. 17• Issue 7 • Page 24
Continuing Education Offering: The goal of this article is to educate nurse practitioners about diabetic foot ulcers. Nurse practitioners may obtain 2 contact hours by reading this article and earning a passing score on the test that follows. For immediate test results, take the quiz online at www.advanceweb.com/NP. The author has completed a disclosure statement and stated no real or perceived conflicts of interest.
How to Obtain Contact Hours by Reading This Article
Instructions: Nurse practitioners may receive 2 contact hours by reading the article noted below and earning a passing score on the accompanying quiz. To obtain contact hours:
1. Read the article "Diabetic Foot Ulcers. An Update on Risk Assessment, Prevention and Management," carefully noting the tables and other illustrative materials provided to enhance your knowledge and understanding of the content.
2. Read each question, and record your answers on the registration form provided.
3. Fill out the evaluation portion completely. You will not receive CE credit if this section is not completed.
4. Type or print your full name and address in the space provided on the registration form.
5. Forward the completed registration form with your check or money order for $10.00 payable to Merion Publications, or provide your credit card information. Quizzes are accepted up to 24 months from publication.
Continuing Education Credit: Merion Publications Inc. is approved as a provider of continuing education in nursing (Provider #008-0-07) by the Pennsylvania State Nurses Association, which is accredited as an approver of continuing education in nursing by the American Nurses Credentialing Center Commission on Accreditation, the California Board of Registered Nursing (Provider #CEP 13230) and the Florida Board of Nursing (Provider #CEP 3298). California and Florida participants must retain certificates for 4 years.
You will be advised of your score within 30 to 60 days of receipt of the completed test. A score of 70% or above comprises a passing grade. A certificate will be awarded to participants who pass. Participants who score less than 70% can retest one time for no additional charge. No refunds are provided.
Objectives: The purpose of this article is to educate nurse practitioners about diabetic foot ulcers. After reading this article, the nurse practitioner should be able to:
• discuss the significance of diabetic foot ulcers with regard to amputation rate and mortality
• identify at least four causal factors of diabetic foot ulceration
• list components of a comprehensive foot exam
• discuss management of the at-risk diabetic foot or ulcer.
Directions: On the registration form, check the box next to the best answer.
Diabetic foot ulcers are associated with high morbidity, mortality and expense. With diabetes prevalence on the rise, a solid understanding of the significance of foot ulcers and current strategies for assessment and treatment is necessary to meet this challenge head on.
The State of Diabetes Complications in America report examined the prevalence and costs of health problems related to type 2 diabetes.1Foot problems, defined as foot or toe amputations, foot lesions and foot numbness, occurred in 22.9% of patients. They were second only to chronic kidney disease, defined as microalbuminuria and affecting 27.8% of patients. Eye damage (18.9%), heart failure (7.9%) and coronary artery disease (9.1%) were next in incidence.
Up to 25% of diabetes patients develop a foot ulcer in their lifetimes, and more than half of these ulcers become infected.2,3Infected foot ulcers precede up to 85% of diabetes-related amputations.2Diabetic foot ulcers recur at an average rate of 34% after 1 year, 61% after 3 years and 70% at 5 years.2-4Within 2 years of amputation, 50% of patients undergo a subsequent amputation.5Amputation carries significant social, psychological and economic consequences.2
The prevalence of comorbidities is higher in diabetes patients with foot ulcers, which may account for postamputation mortality rates that range from 13% to 40% after 1 year, 35% to 65% after 3 years and 39% to 80% after 5 years.2,6This is higher than the amputation rates for many malignancies.2
Etiology of Ulceration
Multiple etiologic factors contribute to diabetic foot ulcers. Four dominant clusters are considered causal pathways. Neuropathy, deformity, callus and elevated peak pressures form the most dominant cluster.7The remaining three - ischemia, ill-fitting footwear and penetrating trauma - can be considered pivotal events in ulcer formation.7
Diabetic peripheral neuropathy occurs in nearly 60% of patients with diabetes.8One of the most common manifestations is chronic sensory motor neuropathy. Peripheral sensory motor neuropathy results in loss of protective sensation and significantly reduces response to the discomfort of repetitive mechanical stress. This loss of sensation is a prime factor associated with ulcer occurrence.8
Sensory motor neuropathy causes imbalances between flexor and extensor muscles, resulting in atrophy, weakness, foot deformities and maldistribution of weight bearing.9Soft tissue glycosylation causes tendon thickening and joint stiffness with subsequent reduction in joint mobility.9Plantar fat pad thinning with forward shift creates prominent metatarsal heads.8These biomechanical abnormalities result in increased plantar pressures with callus formation, which is associated with an 11-fold increase in ulceration risk.9Foot deformities and high pressures, combined with loss of protective sensation, allow for unnoticed injury that can lead to ulcer formation on the tips of contracted toes, bony prominences and plantar areas (Figure 1).
Autonomic neuropathy can cause hypohydrosis, excessively dry skin and increased hyperkeratotic tissue buildup predisposing to deep fissures that, in conjunction with loss of protective sensation, can become unnoticed portals for infection.9Additionally, autonomic dysfunction is associated with altered blood flow in the foot, arteriovenous shunting and distended foot veins.9
When diabetic peripheral neuropathy is present, unrecognized trauma and inflammation can lead to neuropathic osteoarthropathy, otherwise known as Charcot joint disease. Charcot foot is a progressive condition characterized by joint dislocation, pathologic fractures and collapse of the foot and ankle. This is a challenging disorder to recognize and treat, and it is often misdiagnosed in the acute phase as an ankle sprain or cellulitis. Acute Charcot disease requires prompt expert referral to minimize permanent disability. Chronic Charcot arthropathy creates a "rocker bottom" foot deformity that results in severe biomechanical abnormalities that produce associated increased plantar pressures and ulcer risk (Figure 2).
Peripheral arterial disease (PAD) cannot be overlooked as a contributing factor to diabetic foot ulceration. PAD is more common in people with diabetes and has a prevalence of 29% in patients older than 50.10In diabetes, the distal femoral popliteal and tibial vessels below the knee are affected, often sparing the vessels of the foot.9In contrast, risk factors such as smoking and hypertension are associated with more proximal aortoiliofemoral disease.10In patients with diabetes, PAD is often asymptomatic.10Consequently, patients may present later in the disease continuum with more severe disease. The presence of ischemia is associated with the most serious negative outcomes.11
Ill-fitting footwear is another pivotal factor in ulcer development.7Tight shoes can cause callus formation in areas of high pressure and exaggerate deformities.9Shoes that are too large result in friction and shearing of plantar tissues.9Shoes that are not adjusted to accommodate rigid foot deformities precipitate tissue breakdown over the deformity.9The combination of these extrinsic stressors with loss of protective sensation inevitably leads to diabetic foot ulceration. In fact, inappropriate footwear is one of the most common causes of foot trauma in people with diabetes (Figure 3).9
The last pivotal event in the development of diabetic foot ulcer is penetrating trauma to the foot. Puncture injuries and subsequent ulcers in people with diabetes are 46 times more likely to lead to amputation.7As many as 41% of puncture injuries in people with diabetes occur while the patient is not wearing shoes.7
Additional Risk Factors
Although men face a higher risk for foot ulceration than women, a recent study found that women and men have similar risks for ulcer development once neuropathy and other risk factors are present.12(Women with less severe PAD and risk factors face a lesser risk of ulceration compared with men.) Additional factors associated with foot ulcer risk are listed in Table 1.
Comprehensive Foot Exam
All patients with diabetes should remove their shoes and socks each time they see a healthcare provider. In addition, annual comprehensive foot examinations are recommended; high-risk patients require more frequent exams.13Only 66% of adults with diabetes received foot exams in 2005.14
The yearly comprehensive foot exam does not require much time, and it uses common assessment tools. Components of the exam include history, visual inspection, neurologic and vascular assessment, and risk stratification. The preventive plan of care is determined based on risk and may include referral to specialty providers.
History
Suspect PAD if the patient's past medical history includes cardiovascular, cerbrovascular or renal disease. Investigate the etiology of previous ulcerations and factors that led to resolution. Ask about activity; research suggests that people who develop diabetic foot ulcers have "peak and valley" variations in exercise patterns.15In other words, periods of physical activity are interrupted by long periods of inactivity.
Also ask about any history of resistant bacterial infection; this is important when choosing antimicrobial therapy (if infection develops). In your review of systems, ask whether the patient is experiencing signs or symptoms listed in Table 2.
Inspection
Inspect between the patient's toes and from forefoot to heel. Examine the skin for injury, calluses, evidence of hemorrhage under callus, fissures, excessive dryness, maceration or other unusual conditions. Most diabetic ulcers occur on areas subject to increased pressure, such as the plantar surface of the foot (Figures 1 and 2).9Skin that is thin, shiny, fragile and hairless may indicate decreased vascular supply. Document the presence of any edema.
Inspect the patient's nails for dystrophy, paronychia, onychocryptosis, length and onychomycosis. Inspect socks or hose for blood or other discharge. Examine footwear for torn linings, foreign objects, abnormal wear patterns and proper fit. Examine for the presence of deformity, contractures, muscle wasting and atrophy.16
Neurologic Assessment
The neurologic portion of the exam is designed to identify loss of protective sensation. The necessary equipment includes a 10-gram (5.07) Semmes-Weinstein monofilament, a 128-Hz tuning fork and a reflex hammer. Abnormal test results using any of these tools are highly suggestive of sensation loss.
Screening with the 10-g monofilament has been validated in a number of trials. The monofilament is designed to buckle when a 10-g force is applied. Up to 10 sites on the foot may be assessed, but testing the first, third and fifth metatarsal heads and the plantar surface of the distal great toe correctly identifies 90% of patients with sensation loss.2Before testing the foot, apply the monofilament to the patient's dorsal hand to show him or her what to expect and to disperse any fears of pain. Have the patient close his or her eyes and tell you when he or she feels the monofilament applied to any site. Avoid areas of callus.
To perform the test, touch the monofilament perpendicular to the area to be tested, and apply sufficient force to bend the monofilament into a "C" shape. Wait for the patient response no longer than 1 to 1.5 seconds, then remove the monofilament. The inability to detect this pressure at one or more anatomic sites on the plantar surface of the foot has been associated with loss of large fiber nerve function and loss of protective sensation.16Document results as 4/4 (all testing sites felt) or 0/4 to 3/4, depending on results. Complete instructions about how to perform this test are available within any of the resources listed in Table 3.
Use the 128-Hz tuning fork to assess vibratory perception. Loss of vibratory perception is associated with diabetic peripheral neuropathy.2An abnormal response can be defined as loss of vibratory sensation by the patient when the examiner still perceives vibration. For this test, place the fork at the end of the dorsal bony prominence of the patient's great toe proximal to the nail.
Lastly, the absence of ankle reflexes is associated with diabetic peripheral neuropathy and increased ulcer risk.16Place the foot in a neutral position before testing, to stretch the Achilles tendon.
Vascular Assessment
The presence of PAD elevates a patient's risk for ulceration, so PAD screening should be a standard part of care.2Assessment of the dorsalis pedis and posterior tibial pulses is a component of the comprehensive foot exam. The absence of one or more of these pulses is suspicious for PAD. However, because of the vascular pathology distribution in diabetes, pedal pulses may still be palpable even in the presence of significant vascular disease. For this reason, the American Diabetes Association Consensus Panel on PAD recommends measurement of ankle-brachial index (ABI) on all diabetes patients older than 50.10
The panel also recommends considering ABI measurement in younger patients with multiple PAD risk factors or signs and symptoms of PAD, such as nonhealing wounds, claudication or resting pain. For patients with normal test results, repeat ABI measurement every 5 years. An additional resource is the PAD guidelines drafted by the American College of Cardiology and the American Heart Association.17
ABI is a relatively easy test to perform, requiring only a handheld 5-MHz or 10-MHz Doppler and sphygmomanometer. Place the patient supine for 5 minutes. Using the Doppler, measure systolic blood pressure in each arm. Next, place the blood pressure cuff just above the ankle and measure systolic blood pressure in each foot using the dorsalis pedis or the posterior tibial artery. Divide the ankle systolic blood pressure by the higher of the two brachial pressures; the result is the ABI.16
Research shows that ABI results obtained using a pocket Doppler are of equal accuracy to vascular laboratory tests, but use caution in diabetes patients because incompressible arteries (a result of distal calcification) may yield false highs.16,18Always interpret results in the context of risk profile and clinical assessment. ABI results between 0.9 and 1.2 are considered normal. Readings below 0.9 indicate the presence of PAD, and readings below 0.4 suggest critical limb ischemia.10Values above 1.3 are considered abnormally high. Both low and high ABI results have been associated with a significant increase in mortality.19If the ABI result is abnormal, refer the patient to a vascular specialist for further diagnostic testing.
Assignment of Risk Category
The results of the complete physical examination allow determination of ulceration risk. Table 4 presents current risk criteria.11Increase in risk category is associated with higher amputation risk.16The use of an assessment tool provides a focused assessment approach and facilitates documentation and communication between providers.
Patient Education
Patient education improves short-term knowledge and may reduce foot ulceration risk.2Table 5 outlines basic educational points. Reinforce preventive education at every visit, including smoking cessation. Help patients and family members understand the implications of their assessed risk category and the importance of seeing a healthcare provider when they first notice any abnormalities.
Have patients demonstrate foot care practices whenever possible. Patients with arthritis, poor vision, loss of manual dexterity and memory loss may have difficulty maintaining a given plan of care.20Older patients in particular may struggle with self-examination; one study reported that up to 80% of patients older than 60 could not see or reach their feet.9
Technologies such as handheld thermometry can identify preulcerative inflammation, and research shows their use can reduce ulcer recurrence fourfold.21The use of temperature monitoring as a self-assessment tool may become a common preventive strategy in the future.21Remind hospitalized patients and families that the bedside nursing staff should be checking the posterior heel area at least daily.22They should also institute heel precautions to prevent pressure ulcer development.22
Management of Ulceration
Promptly refer patients with diabetic foot ulcers to a podiatrist or wound care center. Reassess vascular status, and document it. If you are not familiar with wound scales such as the Wagner or University of Texas grading systems, focus on assessment and description in the record. Evaluate for undermining; these ulcers may be associated with deep tissue necrosis that requires emergent surgical debridement. Suspect osteomyelitis with exposed bone or the ability to probe to bone.3Refer to the Infectious Disease Society of America's guidelines for diabetic foot infections.23Instruct the patient to cleanse the ulcer with saline daily and to avoid showering. When significant drainage is present, cover the wound with a calcium alginate dressing, and secure with dry gauze. Instruct the patient to change the dressing daily and as needed to absorb breakthrough drainage. Wounds with less drainage can be covered with a foam dressing or a piece of gauze lightly moistened with saline. These dressings must be secured and changed daily. Saline dressings are often not the preferred long-term choice because rapid evaporation can lead to a dry dressing whose removal will harm healthy tissue. On the other hand, a dressing that is too moist can lead to maceration of the periwound area and infection risk. If other options are not available, gauze that is moistened slightly with saline can serve adequately until the patient sees a specialist.
Many advanced products are available for the treatment of diabetic foot ulcers; wound care specialists can make the most appropriate recommendations for their use.24Teach the patient to observe for signs and symptoms of infection, and emphasize that the presence of pain in an insensate foot is an emergency. Follow the patient closely until a specialist appointment takes place. Lastly, monitor for signs and symptoms of depression because foot ulcers have negative effects on well-being.25Because most ulcers result from a combination of high peak pressure and loss of protective sensation, the mainstays of diabetic foot ulcer management are offloading and the sharp debridement of hyperkeratotic buildup and necrotic tissue.24The most effective modality for offloading is a total contact cast, but it is expensive and requires more complex skills for application. A total contact cast is effective because patients frequently remove offloading devices, rendering the therapeutic effect less than optimal.24A total contact cast creates a wider distribution of plantar pressures during ambulation and cannot be removed by the patient. A healthcare provider changes the cast once or twice a week.
A variety of shoes and boots are available to offload the ulcer and are good alternatives to the total contact cast. When they are worn consistently, removable cast walkers have healing rates equal to the total contact cast. But they are not available in most office settings. A postoperative shoe can protect the plantar surface from injury until a podiatrist can determine the most effective offloading strategy; be aware that this is not a long-term offloading device for most ulcerations. Patients should not wear their regular shoes after an ulcer presents. Instruct every patient with diabetes to avoid walking on any foot ulcer.
Putting It Into Practice
Clinical interventions to prevent diabetic foot ulcers include glycemic control, smoking cessation, regular foot examination, appropriate footwear, regular debridement of callus, and involvement of a multidisciplinary healthcare team.24The American Diabetes Association recommends that diabetes patients with peripheral neuropathy undergo a visual foot inspection during every visit with a healthcare professional.13
The number of prophylactic surgical procedures to correct deformities that increase plantar pressure is on an upswing.2Vascular reconstructive surgeries in the lower extremities and various endovascular procedures can promote resolution of nonhealing ulcers and improve significant PAD.9Healthy People 2010 set a goal of reducing diabetes-related amputations by 55%; this will be difficult to reach without attention to the strategies outlined in this article.9
Various tools, programs and forms are available to assist NPs in reducing the sequelae of diabetic foot ulcers, most at no charge (Table 3). Find a system that works in your practice so that you can consistently assess foot ulcer risk and provide appropriate treatments and referrals.
Nancy Slone Rivera is an adult nurse practitioner who is also certified in wound and ostomy nursing. She is on faculty at the Center for Lower Extremity Ambulatory Research at Scholl College of Podiatric Medicine at Rosalind Franklin University in Chicago.
References
1. American Association of Clinical Endocrinologists. State of Diabetes Complications in America. 2007. Available at: http://aace.com/newsroom/press/2007/images/DiabetesComplicationsReport_FINAL.pdf. Accessed April 9, 2009.
2. Singh N, et al. Preventing foot ulcers in patients with diabetes. JAMA. 2005;293(2):217-228.
3. Lavery LA, et al. Risk factors for foot infections in individuals with diabetes. Diabetes Care. 2006;29(6):1288-1293.
4. Apelqvist J, et al. Long-term prognosis for diabetic patients with foot ulcers. J Intern Med. 1993;233(6):485-491.
5. Armstrong DG, et al. Amputation and reamputation of the diabetic foot. J Am Podiatr Med Assoc. 1997;87(6):255-259.
6. Doupis J, et al. High rates for comorbid conditions in patients with type 2 diabetes and foot ulcers. Wounds. 2008;20(5):132-138.
7. Lavery LA, et al. What are the most effective interventions in preventing diabetic foot ulcers? Int Wound J. 2008;5(3):425-433.
8. Armstrong DG, Lavery LA. Diabetic foot ulcers: prevention, diagnosis and classification. Am Fam Physician. 1998;57(6):1325-1332, 1337-1338.
9. Armstrong DG, Lavery LA, eds. Clinical Care of the Diabetic Foot. Alexandria, Va.: American Diabetes Association; 2005.
10. American Diabetes Association. Peripheral arterial disease in people with diabetes. Diabetes Care. 2003;26(12):3333-3341.
11. Lavery LA, et al. Reevaluating the way we classify the diabetic foot: restructuring the diabetic foot risk classification system of the International Working Group on the Diabetic Foot. Diabetes Care. 2008;31(1):154-156.
12. Dinh T, Veves A. The influence of gender as a risk factor in diabetic foot ulceration. Wounds. 2008;20(5):127-131.
13. Mayfield JA, et al.; American Diabetes Association. Preventive foot care in diabetes. Diabetes Care. 2004;27(suppl 1):S63-S64.
14. Age-Adjusted Rates of Foot Exam in the Last Year per 100 Adults with Diabetes, United States, 1994-2007. Available at: http://cdc.gov/diabetes/statistics/preventive/fX_foot.htm. Accessed April 9, 2009.
15. Armstrong DG, et al. Variability in activity may precede diabetic foot ulceration. Diabetes Care. 2004;27(8):1980-1984.
16. Boulton AJ, et al. Comprehensive foot examination and risk assessment: a report of the task force of the foot care interest group of the American Diabetes Association, with endorsement by the American Association of Clinical Endocrinologists. Diabetes Care. 2008;31(8):1669-1684.
17. Hirsch AT, et al. ACC/AHA 2005 practice guidelines for the management of patients with peripheral arterial disease. Circulation. 2006;113(1):e463-e654.
18. Bonham PA, et al. Are ankle and toe brachial indices (ABI-TBI) obtained by a pocket doppler interchangeable with those obtained by standard laboratory equipment? J Wound Ostomy Continence Nurs. 2007;34(1):35-44.
19. Resnick HE, et al. Relationship of high and low ankle brachial index to all-cause and cardiovascular disease mortality: the Strong Heart Study. Circulation. 2004;109(6):733-739.
20. Van Gils CC, Stark L. Diabetes mellitus and the elderly: special considerations for foot ulcer prevention and care. Ostomy Wound Manage. 2006;52(9):50-56.
21. Lavery LA, et al. Preventing diabetic foot ulcer recurrence in high-risk patients: use of temperature monitoring as a self-assessment tool. Diabetes Care. 2007;30(1):14-20.
22. Langemo D, et al. Heel pressure ulcers stand guard. Adv Skin Wound Care. 2008;21(6):282-292.
23. Lipsky BA, et al. Diagnosis and treatment of diabetic foot infections. Clin Infect Dis. 2004;39(7):885-910.
24. Wu S, Armstrong DG. Managing the diabetic foot: treatment, wound care and offloading techniques. Diabetes Voice. 2005;50(special issue):29-32.
25. Searle A, et al. A qualitative approach to understanding the experience of ulceration and healing in the diabetic foot: patient and podiatrist perspective. Wounds. 2005;17(1):16-26.
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