Lower-extremity amputation in diabetes. The independent effects of peripheral vascular disease, sensory neuropathy, and foot ulcers.
OBJECTIVE: To identify risk factors for lower-extremity amputation (LEA) in individuals with diabetes and to estimate the incidence of LEA. RESEARCH DESIGN AND METHODS: This is a prospective study of 776 U.S. veterans in a general medicine clinic in Seattle, Washington. The outcome was first LEA during follow-up. Potential risk factors evaluated in proportional hazards models included, among others, peripheral vascular disease (PVD), sensory neuropathy, former LEA, foot deformities and ulcers, diabetes duration and treatment, and hyperglycemia. RESULTS: Associated with an increased risk for LEA were PVD defined as transcutaneous oxygen < or = 50 mmHg (relative risk [RR] = 3.0, 95% CI 1.3-7.1), insensitivity to monofilament testing (RR = 2.9, odds ratio = 1.1-7.8), lower-extremity ulcers (RR = 2.5, CI 1.1-5.4), former LEA, and treatment with insulin when controlling for duration of diabetes and other factors in the model. PVD defined as absent or diminished lower-extremity pulses or an ankle arm index < or = 0.8 was also associated with a significantly higher risk of LEA in separate models. Foot ulcers were associated with an increased ipsilateral risk of amputation. The age-adjusted incidence among men only for LEA standardized to the 1991 U.S. male diabetic population was 11.3/1,000 patient-years. CONCLUSIONS: This prospective study shows that peripheral sensory neuropathy, PVD, foot ulcers (particularly if they appear on the same side as the eventual LEA), former amputation, and treatment with insulin are independent risk factors for LEA in patients with diabetes.