The American Diabetes Association estimates that in the United States, there are 20 million individuals with diabetes; this condition remains undiagnosed in about 50% of these individuals. The incidence of diabetes increases with age. Fifteen percent of patients with diabetes will develop a foot ulcer during their lifetime, and 3% to 4% of diabetic patients currently have ulcers. Vascular diabetes is 30 times more common, and gangrene is 70 times more common. Once an ulcer develops, the risk of needing a LEA increases eightfold.

The etiology of this problem is peripheral neuropathy that affects sensory, motor, and autonomic pathways. Sensory neuropathy is the most important form of neuropathy and is the primary cause of unrecognized injury. This form of neuropathy deprives the patient of early warning signs of pain or pressure from footwear. This could be caused by inadequate soft tissue padding or infection. It appears in a stocking-glove distribution with many of these individuals complaining of burning or searing pain. The primary risk factor for the development of DFUs is loss of protective sensation, best measured by insensitivity to the Semmes-Weinstein 5.07 (10 g) monofilament. Abnormal white blood cell (WBC) function and the presence of peripheral vascular disease allow wounds to become contaminated and infected by normally nonpathogenic organisms; this explains the identification of unusual bacteria from the wounds of patients with diabetes.

It has been estimated that 2% of people with diabetes develop a Charcot joint. This is a condition in which certain joints, most commonly the midfoot, collapse and degenerate. This occurs only in people who have peripheral neuropathy and ambulate. The earliest stage consists of a red, hot, swollen foot. This is often mistaken for an infection. X-rays will often show severe destruction and erosions of the involved joints. Later stages are without the inflammation but may show either a completely flattened arch or the classical “rocker bottom” foot.

How does the clinician determine if there is an active infection? This is usually done by clinical evaluation. For example, redness, swelling, pain, and pus all point to infection. Keep in mind that all ulcers will have some drainage. Since the skin (which is ordinarily a barrier to prevent dehydration) is disrupted, drainage (which is usually watery or blood tinged) will be present. This is in distinction to drainage that is thick, white and creamy, which usually indicates pus and an infection. Also, culture swabs should not be used alone as an indication of infection, because most diabetic ulcers will have bacterial colonization
on the surface of the ulcer but do not represent a true infection. Culture swabs are most useful as a means of determining which bacterial organisms are causing an infection once a diagnosis of infection has been made from clinical findings. It is critical to determine whether the ulcer is deep to the dermis or not. Ulcers that are superficial to the dermis are likely more responsive to local care, whereas those that are deep to the dermis usually require aggressive surgical management in a timely fashion.

Weight-bearing views of the foot are obtained in anteroposterior (AP), lateral, and oblique planes (Fig. 34-1). X-rays are helpful in assessing for fractures associated joint destruction or Charcot joint.