Causal pathways for incident lower-extremity ulcers in patients with diabetes from two settings

OBJECTIVE - To determine the frequency and constellations of anatomic, path ophysiologic, and environmental factors involved in the development of inci dent diabetic foot ulcers in patients with diabetes and no history of foot ulcers from Manchester, U.K., and Seattle, Washington, research settings. RESEARCH DESIGN AND METHODS - The Rothman model of causation was applied to the diabetic foot ulcer condition. The presence of structural deformities, peripheral neuropathy, ischemia, infection, edema, and callus formation wa s determined for diabetic individuals with incident foot ulcers in Manchest er and Seattle. Demographic, health, diabetes, and ulcer data were ascertai ned for each patient. A multidisciplinary group of foot specialists blinded to patient identity independently reviewed detailed abstracts to determine component and sufficient causes present and contributing to the developmen t of each patient's foot ulcer. A modified Delphi process assisted the grou p in reaching consensus on component causes for each patient. Estimates of the proportion of ulcers that could be ascribed to each component cause wer e computed. RESULTS - From among 92 study patients from Manchester and 56 from Seattle, 32 unique causal pathways were identified. A critical triad (neuropathy, m inor foot trauma, foot deformity) was present in >63% of patient's causal p athways to foot ulcers. The components edema and ischemia contributed to th e development of 37 and 35% of foot ulcers, respectively. Callus formation was associated with ulcer development in 30% of the pathways. Two unitary c auses of ulcer were identified, with trauma and edema accounting for 6 and <1% of ulcers, respectively. The majority of the lesions were on the planta r toes, forefoot, and midfoot. CONCLUSIONS - The most frequent component causes for lower-extremity ulcers were trauma, neuropathy, and deformity, which were present in a majority o f patients. Clinicians are encouraged to use proven strategies to prevent a nd decrease the impact of modifiable conditions leading to foot ulcers in p atients with diabetes.