Emerging Treatments and Technologies N A L A R T I C L E Role of Neuropathy and High Foot Pressures in Diabetic Foot Ulceration ROBERT G. FRYKBERG, DPM, MPH LAWRENCE A. LAVERY, DPM, MPH HAU PHAM, DPM CAROLYN HARVEY, DPM LAWRENCE HARKLESS, DPM ARISTIDIS VEVES, MD OBJECTIVE — High plantar foot pressures in association with peripheral neuropathy have been ascertained to be important risk factors for ulceration in the diabetic foot. Most studies investigating these parameters have been limited by their size and the homogeneity of study subjects. The objective of this study was therefore to ascertain the risk of ulceration associated with high foot pressures and peripheral neuropathy 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 Hispanic (group H) (n = 94) racial origins with an overall age of 58.5 ± 12.5 years (range 20-83). There was an equal distribution of men and women across the entire study population. All patients underwent a complete medical history and lower extremity evaluation for neuropathy and foot pressures. Neuropathic parameters were dichotomized (0/1) into two high-risk variables: patients with a vibration perception threshold (VPT) ^25 V were categorized as HiVPT (n = 132) and those with Semmes-Weinstein monofilament tests 5:5.07 were classified as HiSWF (n = 190). The mean dynamic foot pressures of three footsteps were measured using the F-scan mat system with patients walking without shoes. Maximum plantar pressures were dichotomized into a high-pressure variable (Pmax6) indicating those subjects with pressures ^6 kg/cm 2 (n = 96). A total of 99 patients had a current or prior history of ulceration at baseline. RESULTS — Joint mobility was significantly greater in the Hispanic cohort compared with the other groups at the first metatarsal-phalangeal joint (C 67 ± 23°, B 69 ± 23°, H 82 ± 23°, P = 0.000), while the subtalar joint mobility was reduced in the Caucasian group (C 21 ± 8°, B 26 ± 7°, H 27 ± 11°, P = 0.000). Maximum plantar foot pressures were significantly 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 regression 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 duration, sex, and race (all P < 0.05), multivariate logistic regression yielded the following significant associations with ulceration: Pmax6 (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 pressures (^6 kg/cm 2 ) and neuropa- thy are independently associated with ulceration in a diverse diabetic population, with the lat- ter having the greater magnitude of effect. In black and Hispanic diabetic patients especially, joint mobility and plantar pressures are less predictive of ulceration than in Caucasians. Diabetes Care 21:1714-1719, 1998 From the Deaconess-Joslin Foot Center and Microcirculation Laboratory (R.G.F), Beth Israel Deaconess Med- ical Center; the Division of Podiatry (R.G.F, H.P), Department of Medicine (A.V), Harvard Medical School, Boston, Massachusetts; the Division of Podiatry (L.A.L., L.H.), Department of Orthopedics, University of Texas Health Sciences Center, San Antonio, Texas; and the California College of Podiatric Medicine (C.H.), San Francisco, California. Address correspondence and reprint requests to Robert G. Frykberg, DPM, MPH, Beth Israel Deaconess Medical Center, Deaconess-Joslin Foot Center, One Deaconess Rd., Boston, MA 02215. E-mail: rgfdpm© aol.com. Received for publication 15 April 1998 and accepted in revised form 10 June 1998. Abbreviations: HiSWF, patients with Semmes-Weinstein monofilament test ^5.07; HiVPT, patients with vibration perception threshold >25 V; LJM, limited joint mobility; MPP, maximum peak plantar pressures; MTP, metatarsal-phalangeal; OR, odds ratio; Pmax6, high-pressure variable; STJ, subtalar joint; VPT, vibra- tion perception threshold. A table elsewhere in this issue shows conventional and Systeme International (SI) units and conversion factors for many substances. F oot ulceration is a significant cause of morbidity in patients with diabetes and can lead to prolonged lengths of hospital stay (1-6). A recent epidemiolog- ical review of National Hospital Discharge Survey (NHDS) data indicates an increase in diabetes-related foot ulcer hospitaliza- tion rates from 1983 to 1990 and that the average length of hospital stay for such admissions was 59% longer than that for diabetes discharges without them (1). In fact, it has been estimated that ~20% of hospitalizations attributable to diabetes are the result of foot ulcers and infection (7), with an ~15% lifetime risk for foot ulcer- ation in all diabetic individuals (8). Another report further indicates that there is an increased risk of mortality associated with diabetic foot ulcers (9). Numerous putative risk factors for foot ulceration in diabetes have been ascertained (5,10-14). Among others, peripheral neu- ropathy, vascular disease, limited joint mobility (LJM), high plantar pressures, and associated extrinsic sources of trauma have all been implicated as significant predispos- ing factors leading to ulceration in popula- tion-based and clinical studies seeking to quantify such relationships (15-25). The value of determining these associations is that such knowledge can be useful in estab- lishing screening programs for patients at risk of developing ulceration or in assigning levels of risk (5,26-29). Risk assessment is also an integral component of prevention- based foot care programs (12,30,31). How- ever, there is no consensus as to which specific testing modality is best suited for screening diabetic patients. Usually several modalities, such as monofilaments, biothe- siometry and/or plantar pressure assess- ments, are used in conjunction with a brief history and physical examination (27,31-33). Racial differences in LJM, asso- ciated foot pressures, and rates of ulceration do exist, however, and these racial charac- teristics must be considered when assessing levels of risk (34,35). We therefore chose to study the association of neuropathy and plantar foot pressures with ulceration in a geographically diverse population of dia- betic patients. Furthermore, we sought to determine and categorize levels ofriskasso- ciated with patients of Caucasian, black, 1714 DIABETES CARE, VOLUME 21, NUMBER 10, OCTOBER 1998 Downloaded from http://diabetesjournals.org/care/article-pdf/21/10/1714/585414/21-10-1714.pdf by guest on 28 December 2022