One study found that 80 percent of nontraumatic LEAs are preceded by a foot ulceration, which provides a portal for infection.⁹ According to BRFSS data, approximately 12 percent of U.S. adults with diabetes had a history of foot ulcer, a risk factor for LEA.¹⁰ Another report identified minor trauma, ulceration, and faulty wound healing as precursors to 73 percent of LEAs, often in combination with gangrene and infection.¹¹ Other risk factors include the presence of sensory peripheral neuropathy, altered biomechanics, elevated pressure on the sole of the foot, and limited joint mobility.¹²

People with diabetes who have neuropathy are 1.7 times more likely to develop a foot ulceration; in persons with both neuropathy and foot deformity, the risk is 12 times greater; in those who also have a history of pathology (prior amputation or ulceration), the risk is 36 times greater.^13,14

People with diabetes who have increased risk for lower-extremity ulceration and amputation are males, people with diabetes for more than 10 years, people who use tobacco and those with a history of poor glycemic control or the presence of cardiac, retinal, or renal complications.^15,16,17

Foot Evaluation in People With Diabetes

The podiatrist uses the following considerations in evaluating the feet of people with diabetes to assess the risk for complications.

• Neuropathy. The presence of subjective tingling, burning, numbness, or the sensation of bugs crawling on skin may indicate peripheral sensory neuropathy. On clinical examination, this condition can be detected with an instrument known as a Semmes-Weinstein 5.07 (10 gram) monofilament.
• Vasculopathy. Cramping of calf muscles when walking ("charley horse") that requires frequent rest periods suggests intermittent claudication. This condition, often caused by insufficient blood supply to the region beneath the knee, indicates the presence of early or moderate occlusion of the arteries that is common to the lower extremities of people with diabetes. Intense cramping and aching in the toes only at night indicates "rest pain," which is usually relieved by hanging the feet over the side of the bed and by walking. This symptom signifies the end-stage blood vessel disorder and tissue ischemia that precedes diabetic gangrene. Although poor blood supply is not a risk factor for developing ulceration, it is a significant risk factor for amputation.
• Dermatological conditions. Corns and calluses (hyperkeratotic lesions) of the feet result from elevated mechanical pressure and shearing of the skin. They often precede breakdown of skin and lead to blisters or ulceration. Superficial lacerations and fissures, or maceration (softening) between the toes or on the heel, all can serve as portals for infection. Corns, calluses, and bleeding beneath the nail may signify the presence of sensory neuropathy.
• Musculoskeletal symptoms. Structural changes in the diabetic foot may develop in conjunction with muscle-tendon imbalances as a result of motor neuropathy. These deformities include the presence of hammertoes, bunions, high-arched foot, or flatfoot - all of which increase the potential for focal irritation of the foot in the shoe.
• Lifestyle and family history. People with diabetes who smoke are four times more likely than nondiabetic smokers to develop lower-extremity vascular disease. Poor diet and low physical activity levels worsen long-term control of blood glucose and increase the risk of progression of disorders of the peripheral nervous system and/or blood vessels. A family history of cerebrovascular accidents and coronary artery disease may indicate a risk of developing lower-extremity arterial complications. Inherited foot types may predispose to biomechanical deformities that lead to problems with skin breakdown.

Comprehensive Foot Examination

A comprehensive foot examination (including checking pulses, checking sensation, evaluating general foot structure, and evaluating skin and nails for abnormalities) helps determine the person's category of risk for developing foot complications. Persons with diabetes who are at high risk have one or more of the following characteristics: (1) loss of protective sensation, (2) absent pedal pulses, (3) foot deformity, (4) history of foot ulcers, or (5) prior amputation. Low-risk individuals have none of these characteristics.¹⁸ Assessment of risk status identifies people who need more intensive care and evaluation. Further patient education, early intervention, and special footware if indicated can prevent ulcers and ultimately LEAs.