The independent contributions of diabetic neuropathy and vasculopathy in foot ulceration. How great are the risks?

OBJECTIVE

To describe the relative contributions of neurological and vascular abnormalities to the overall risk of diabetic foot ulceration.

RESEARCH DESIGN AND METHODS

A case-control study of diabetic veterans from the Seattle Veterans Affairs Medical Center was conducted using data collected from 46 patients with diabetic foot ulcers and 322 control subjects. Neuropathy was determined by vibratory, monofilament, and tendon reflex testing. Macrovascular disease was measured by ankle-arm blood pressure index, and cutaneous perfusion was measured by transcutaneous oxygen tension (TcPO2) on the dorsal foot. A multivariate logistic regression model was used to adjust for confounding variables and to calculate the odds ratios (ORs) for each independent risk factor.

RESULTS

Three variables were significant independent predictors of foot ulceration: absence of Achilles tendon reflexes (adjusted OR 6.48, 95% confidence interval [CI] 2.37-18.06), insensate to the 5.07 monofilament (adjusted OR 18.42, 95% CI 3.83-88.47), and TcPO2 < 30 mmHg (adjusted OR 57.87, 95% CI 5.08-658.96). Absent vibratory sensation and low ankle-arm blood pressure index were not significant independent risk factors.

CONCLUSIONS

Both neuropathy and vasculopathy are strong independent risk factors for the development of diabetic foot ulcers. In our model, the strongest risk factor is impaired cutaneous oxygenation. However, in the clinical setting, sensory examination with a 5.07 monofilament probably remains the single most practical measure of risk assessment.