Diabetes mellitus is primarily responsible for at least 50,000 non-traumatic lower extremity amputations in the US per year, yet it is now widely believed that many of these amputations are preventable. In particular, there are many statements in the literature suggesting that appropriate footwear can reduce the risk of plantar skin ulceration, which is often the critical event that initiates that path to amputation. Such statements are based on clinical experience from several specialized centers where the use of footwear empirically designed to reduce the likelihood of foot injury by cushioning the plantar surface of the foot has been pioneered. There are, however, very few studies in the literature which have attempted to evaluate the effects of specific footwear modifications in diabetic patients in an objective manner. Despite this paucity of objective information which could guide the practitioner in the prescription and evaluation of footwear designed to alleviate a particular foot problem, a major demonstration supported by HCFA is currently underway to determine if prophylactic footwear is cost effective in diabetics deemed to be at risk for foot injury. The proposed study is designed to fill this void by a systematic investigation of footwear typically prescribed for the diabetic foot. Based on the assumption that a reduction in plantar pressure is the desired mechanical effect of footwear that may reduce plantar ulceration, the applicants will test the hypothesis that elevated plantar pressure in the diabetic neuropathic foot can be reduced to normal levels by appropriate footwear intervention. Standards for normal plantar pressure' barefoot and in standard shoes will first be developed in a healthy control population. Diabetic patients who have lost protective sensation in their feet and who have elevated plantar pressure (but who are free of current significant foot lesions) will then be invited to participate in the study. Starting with the collection of plantar pressure in barefoot walking, the effects on plantar pressure of a standard shoe, a running shoe, an extra depth shoe with standard and custom insoles will be examined in all subjects and compared to the normal group. In the later stages of the study, patients with significant foot deformity will be studied while walking in custom shoes with custom molded insoles and another sub-group of the diabetics will be used to study the effects on plantar pressure of various configurations of the rocker bottom shoe, a frequently prescribed footwear modification in diabetic patients with marked foot deformity. The effects of the various footwear conditions will be examined using analyses of variance. A secondary analysis will also examine the relationship between deformity and plantar pressure, a relationship which has been often implied but never clearly proven. It is anticipated that the results of this study will have wide ranging implications for the prescription of footwear for the diabetic patient which is, at present, an almost entirely empirical process.
