The health-care cost of problems related to the diabetic foot, the most common cause of hospitalization in patients with diabetes, is estimated to be more than $1 billion annually (73). In 2003, the total annual cost of diabetic peripheral neuropathy and its complications were estimated to be between $4.6 and $13.7 billion (74). In large cohort studies, prevalence rates for neuropathy have ranged from 7.5 percent at time of diagnosis of diabetes, to 50 percent 25 years after initial diagnosis (75). It is present in more than 80 percent of diabetic patients with foot lesions (73). Poor glycemic control is associated with an increased risk for neuropathy and amputation (76). In one study, a HbA1c > 13.4 was associated with 2.2 relative risk of amputation (76). In another study, a 50 mg/dl increase in the mean random glucose was associated with a 1.6 OR for amputation (76). Diabetic peripheral neuropathy predisposes to foot ulceration and lower-extremity amputation (74). The presence of peripheral neuropathy is associated with eightfold to eighteenfold higher risk of ulceration and twofold to fifteenfold higher risk of amputation (76). The incidence of self-reported foot ulcers in people with diabetes is 2.4 percent to 2.6 percent per year (76). The prevalence of foot ulcers ranges from 4 percent to 10 percent, and it is estimated in the U.S. that 15 percent of patients with diabetes will develop foot ulceration at least once during their lifetime (74, 76, 77).
While vascular disease does play a role, 60 percent to 70 percent of diabetic foot ulcers are neuropathic in origin (74). It is also estimated that approximately 85 percent of all diabetic lower-extremity amputations are preceded by a nonhealing foot ulcer (76). It is estimated that 45 percent of lower-limb amputations are done on people with diabetes, with the relative probability of lower-extremity amputation reported to be as high as 27 times more likely among patients with diabetes (78, 79). The risk of diabetic ulcers and lower-extremity amputation increases twofold to fourfold with age and duration of diabetes (76). Most studies of people with type 2 diabetes have shown a 1.6 increased risk of lower-extremity ulcers and a 2.8-fold to 6.5-fold higher risk of amputation associated with male sex (76). Lack of patient education on foot care is associated with a 3.2 increased risk of amputation (76). A comprehensive review showed that in the U.S. between 1989 and 1993, the prevalence of amputations was 1.6 percent for people age 18-44 years, 2.4 percent for people age 45-64 years, and 3.6 percent for people > 65 years old (76).
A statewide analysis performed in California showed Hispanics to have proportionally more amputations associated with diabetes than African Americans or non-Hispanic whites (82.7 percent versus 61.6 percent versus 56.8 percent) (80). Overall, however, the incidence of diabetes-related, lower-extremity amputations was higher in African Americans at every level of amputation (80). The level of amputation was: toe (19.9-41.02 percent); foot (3.58-12.91 percent); leg (12.25-37.07 percent); and thigh (4.29-18.73 percent) (80).
A retrospective review of patients admitted to a university hospital showed that patients admitted with diabetic foot ulceration underwent less-than-adequate foot examinations, with 31.4 percent not having documentation of pedal pulses, 59.7 percent not being evaluated for presence of protective sensation, 90 percent of wounds not evaluated for involvement of underlying structures, and 32.9 percent not having foot radiographs (81). This study highlighted the need for a systematic, detailed lower-extremity examination for every patient with diabetes admitted to a hospital (81).
Patients with extremity infections should also be carefully evaluated for the presence of undiagnosed diabetes mellitus (82). In a large retrospective study, 17.2 percent of all patients seen with extremity infections had previously undiagnosed diabetes mellitus, with 12.1 percent having lower-extremity infections (82). Other studies have reported a 3 percent to 7 percent incidence of newly diagnosed diabetes in people presenting with extremity infections (82).
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