ROLE OF NEUROPATHY AND HIGH FOOT PRESSURES IN DIABETIC FOOT ULCERATION

OBJECTIVE - High plantar foot pressures in association with peripheral neuropathy have been ascertained to be important risk factors for ulc eration in the diabetic foot. Most studies investigating, these parame ters have been limited by their size and the homogeneity of study subj ects. The objective of this study was therefore to ascertain the risk of ulceration associated with high foot pressures and peripheral neuro pathy in a large and diverse diabetic population. RESEARCH DESIGN AND METHODS - We studied a cross-sectional group of 251 diabetic patients of Caucasian (group C) (n = 121), black (group B) (n = 36), and Hispan ic (group H) (n = 94) racial origins with an overall age of 58.5 +/- 1 2.5 years (range 20-83). There was an equal distribution of men and wo men across the entire study population. All patients underwent a compl ete medical history and lower extremity evaluation for neuropathy and foot pressures. Neuropathic parameters were dichotomized (0/1) into tw o high-risk variables: patients with a vibration perception threshold (VPT) greater than or equal to 25 V were categorized as HiVPT (n = 132 ) and those with Semmes-Weinstein monofilament tests greater than or e qual to 5.07 were classified as HiSWF (n = 190). The mean dynamic foot pressures of three footsteps were measured using the F-scan mat syste m with patients walking without shoes. Maximum plantar pressures were dichotomized into a high-pressure variable (Pmax6) indicating those su bjects with pressures greater than or equal to 6 kg/cm(2) (n = 96). A total of 99 patients had a current or prior history of ulceration at b aseline. RESULTS - Joint mobility was significantly greater in the His panic cohort compared with the other groups at the first metatarsal-ph alangeal joint (C 67 +/- 23 degrees, B 69 +/- 23 degrees, H 82 +/- 23 degrees, P = 0.000), while the subtalar joint mobility was reduced in the Caucasian group (C 21 +/- 8 degrees, B 26 +/- 7 degrees, H 27 +/- 11 degrees, P = 0.000). Maximum plantar fool pressures were significan tly higher in the Caucasian group (C 6.7 +/- 2.9 kg/cm(2), B 5.7 +/- 2 .8 kg/cm(2), H 4.4 +/- 1.9 kg/cm(2), P = 0.000). Univariate logistic r egression for Pmax6 on the history of ulceration yielded an odds ratio (OR) of 3.9 (P = 0.000). For HiVPT, the OR was 11.7 (P = 0.000), and for HiSWF; the OR was 9.6 (P = 0.000). Controlling for age, diabetes d uration. sex, and race (all P < 0.05), multivariate logistic regressio n yielded the following significant associations with ulceration: Pmax 6 (OR = 2.1. P = 0.002), HiVPT (OR = 4.4, P = 0.000), and HiSWF (OR = 4.1, P = 0.000). CONCLUSIONS - We conclude that both high foot pressur es (greater than or equal to 6 kg/cm(2)) and neuropathy are independen tly associated with ulceration in a diverse diabetic population, with the latter having the greater magnitude of effect. In black and Hispan ic diabetic patients especially joint mobility and plantar pressures a re less predictive of ulceration than in Caucasians.