Diabetic foot ulcers are a complication affecting approximately 15% of people with diabetes. Treating these ulcers is costly, and the resulting disfigurement can be devastating. Twenty-five percent of all hospital admissions are for diabetic foot ulcers. The average hospital stay among patients with foot ulcers is 60% longer than the stay for other causes and costs $20,000 to $60,000 per patient, or up to $6 billion per year. The risk of amputation is 15 to 40 times greater in a person with diabetes than in one who does not have the disease.1-6
An ulcer is defined as a break in the cutaneous layer of the skin extending to the dermis.5 Diabetic foot ulcers account for more than 50% of nontraumatic amputations and are associated with high rates of mortality, reamputation, and contralateral limb amputation.2,7 Vascular insufficiency and peripheral neuropathy are the most common risk factors for developing foot ulcers 6,8 (see Table 1). The risk factors for amputation are identical to those for foot ulcers because 85% of amputations result from foot ulcers.9
Prevention as a first step
Health maintenance is an ongoing process, and optimal ulcer prevention is achieved through a multidisciplinary approach 2,6 (see Table 2). Clinicians should always remind patients with diabetes to eat a proper diet, exercise regularly, and practice good hygiene.10 The American Diabetes Association recommends examining these patients' feet at each visit, in addition to performing an annual comprehensive foot examination that includes using a monofilament to test for possible loss of sensation.5 All patients with diabetes should be evaluated by a podiatrist regularly.11 Patients should be counseled to avoid smoking cigarettes, walking barefoot, using heating pads, and stepping into a bath without first checking the temperature.5 Those with severely deformed feet need to wear custom-molded shoes or have corrective prophylactic surgery.2 Research has demonstrated that the majority of foot ulcers are caused by poorly fitting shoes. Other sources of foot trauma are foreign bodies in the shoes, burns from hot water (see Figure 1), and ingrown toenails. Therapeutic footwear and socks are essential in foot ulcer prevention.6,10
Evaluation of foot ulcers
Patients often have had glucose abnormalities for years before receiving a diagnosis of diabetes. Complications begin to occur 10 to 15 years after diagnosis, earlier if glycemic control is poor. During the initial evaluation of a patient with a foot ulcer, the clinician should obtain a comprehensive history (see Table 3) and perform a complete physical examination.11-13 At each visit, a thorough written description of the ulcer's characteristics, including appearance, size, depth, and location, should be recorded and a photograph taken. This provides a map of progress during treatment.11 Patients should be questioned about leg discomfort including sensations, location, and timing, as well as aggravating and alleviating factors.5,13 Neuropathic ulcers occur on the pressure points of the foot, while vascular ulcers occur on the side and heel of the foot and are painful.8,10
Neuropathy is defined as decreased ability to feel pain as a result of the loss of protective sensation.6,10 The nerve axon causing vasodilation in response to painful stimuli is impaired.1 Inability to perceive the pressure sensation of a 10-g monofilament indicates sensory neuropathy. The neurologic examination also includes measurements of proprioceptive, vibratory, pain, and temperature sensations and deep tendon reflexes.2,4,5,9
Next, the foot should be examined for Charcot's joint, contraction of the toes, dry skin, hammer toes, depressed metatarsal heads, and hallux valgus.14,15 Charcot's joint is defined as pathological fractures that cause joint dislocation and destroy the normal shape of the foot.2 Patients with diabetes who have a Charcot's joint typically complain of swelling and discomfort, and ulcers develop on the bony prominences.
Vascular disease
Peripheral vascular disease (PVD) is two to four times more common in patients with diabetes than in those without diabetes.6,12 Large-vessel disease manifests 10 years earlier and accounts for 70% of all deaths among these patients.12 Microangiopathy occurs at a younger age, affects both sexes equally, and typically involves the tibial and peroneal arteries.8 Cigarette smoking aggravates vascular insufficiency by increasing peripheral vasoconstriction.6
Vascular compromise develops from the inability of the capillaries to vasodilate in response to trauma.8 Patients complaining of claudication and presenting with decreased pulses, absence of hair on the legs, and cool skin temperature require prompt vascular evaluation. Other signs of vascular insufficiency are pain at rest, ischemic rubor when the feet are not elevated, and tissue necrosis.11,13,15 Pain due to vascular insufficiency is aggravated by walking and relieved by keeping the feet in a dependent position.13
The presence of both the pedal and popliteal pulses is the most reliable indicator of arterial perfusion in the foot.9 The vascular examination also includes assessment of capillary refill, evaluation for the presence of hair, measurement of skin temperature, and evaluation for stasis edema.2,11,14 Absence of a pedal pulse with presence of a popliteal pulse is a classic sign of diabetic arterial disease. Arterial Doppler studies should be performed, but arteriography should be reserved for patients in whom revascularization is being considered. 9,15 A noninvasive method for assessing PVD is the ankle-brachial index (ABI). An ABI less than 0.9 indicates PVD. If the ulcer does not appear to be healing or if there are signs of PVD, the patient should be referred to a vascular specialist.2,11-13
Classification of the diabetic foot ulcer leads the clinician to the best treatment course and its anticipated outcome.2,9 There are two commonly used classification systems. The University of Texas system was developed specifically for staging diabetic foot ulcers 2,6 (see Table 4). The second commonly used system is the Wagner system, which was initially developed for PVD and later adapted for diabetic foot ulcers 2,6 (see Table 5). The principles of treating diabetic foot ulcers are simple: good wound care, treatment of infections, and pressure relief.16