In a patient with diabetes mellitus, a small, untreated blister can easily develop into a full-thickness ulceration. A diabetic ulcer, whether of neuropathic or ischemic origin (Figure), is potentially limb-threatening, because it can easily progress to sepsis or gangrene and eventuate in amputation. The outcome depends on timely assessment and initiation of optimal treatment.
Hundreds of millions of dollars are spent each year for the direct care of foot-related pathology in diabetic patients.1,2 Approximately 15% to 20% of the estimated 18.2 million Americans with diabetes are hospitalized because of a foot complication.2 In many cases, these complications-whether the result of infection, ischemia, neuropathy or a combination of these factors-lead to lower extremity amputations. Approximately 82,000 amputations unrelated to trauma are performed on patients with diabetes each year.2
Prevention of diabetic foot wounds is the ultimate goal. The key components of multidisciplinary foot disorder and amputation programs are early detection of foot ulcers and appropriate management of risk factors associated with foot wounds (Table 1). The main risk factors associated with ulceration and eventual amputation are neuropathy, vascular disease, impaired immune response, and structural deformities.3-5 Once a manageable lesion is detected, prompt and aggressive treatment is essential to prevent an exacerbation, thus reducing the risk of amputation. Identification of the cause is crucial to prevent recurrence.
In this article, we discuss the components of a diabetic foot examination, the principles of wound care, and strategies for prevention.
A thorough, systematic lower extremity examination is crucial to the initial treatment of a diabetic foot ulcer4,5 and may provide valuable clues about whether the cause of the wound is mechanical, thermal, or chemical. A stepwise approach that addresses key areas—skin, blood flow, sensation, muscle strength, and pedal deformities—is vital (Table 2). Equally important is the inspection of the patient's shoes for appropriate fit, foreign objects, and patterns of wear. The examination findings help determine the risk level for each patient.
Dermatologic assessment. Inspect the skin and interdigital areas of both feet. Pay particular attention to skin quality, integrity, atrophy, and callus formation, as well as ulcerative or pre-ulcerative changes. Skin color changes that are associated with petechial rashes, small eschars, or heel fissures may indicate a critical level of ischemia or autonomic neuropathy. Toenail changes and subungual drainage or paronychias may be sources of more proximal infection. Thickened or dystrophic onychomycotic toenails may cause subungual pressure ulceration. Close inspection of such nail pathology, especially when the nails are loosened from the nail bed, often reveals lesions that might otherwise be missed.6
Wound assessment. Clinical evaluation includes description and measurement of the wound.7 A tracing of the ulcer on a transparent film or plastic sheet can facilitate this process. Record the tracing and remeasure at subsequent visits to evaluate treatment progress. Digital close-up photography is another option; the photographs can be easily incorporated into the patient's chart or electronic medical record.
Explore the depth and extent of the wound with a small, sterile blunt probe. Check for hidden sinus tracts and deep abscesses, as well as for tendon, muscle, bone, and joint involvement. Palpable bone in the depths of diabetic foot ulcers strongly suggests osteomyelitis.8
Clinical signs of infection—such as purulent drainage, odor, cellulitis, fever, and leukocytosis—must be recorded. Fever and leukocytosis are not always evident, even in the presence of osteomyelitis. Aerobic and anaerobic cultures should be obtained from curettage of the ulcer base; such cultures are more reliable than a superficial swab in elucidating the true pathogens.9,10
Order radiographs to detect osteomyelitis; however, bear in mind that radiography has a low sensitivity and should not be the sole determinant of the need for further interventions. Other imaging modalities can aid in the diagnosis of osteomyelitis. Technetium bone scans, indium- and technetium-99m HMPAO-labeled leukocyte scans, monoclonal anti-granulocyte antibody scans, CT, and MRI are all useful; each has its own advantages and limitations. However, it is unclear whether patients for whom these expensive imaging tests are ordered have better outcomes than those who undergo empiric surgical and medical therapy.11