People with Diabetes Mellitus (DM) and peripheral neuropathy are at high risk for skin breakdown and subsequent lower extremity amputation due to unnoticed, repeated trauma (plantar pressures) to the plantar foot during walking. Current rehabilitation methods use subjective methods to fabricate therapeutic footwear m attempts to reduce plantar pressures and prevent skin breakdown, but ulcer recurrence is high (30-57%). The long term goal of this project is to reduce the incidence of skin breakdown and subsequent amputation by designing and fabricating orthotic devices based on structure, tissue mechanics, and external stresses of the diabetic foot. This proposal will capitalize on an efficient and complementary research design that uses the same patients and many of the same measures to conduct experimental testing in Aim 1 and to develop and validate three-dimensional computational modeling methods in Aim 2. The goal of Aim 1 is to determine the effect of a total contact insert (TCI), a metatarsal pad, and metatarsal pad placement on forefoot plantar pressures and soft tissue deformation. Combining in-shoe pressure testing with spiral x-ray computed tomography (SXCT) will indicate not only if the orthotic device is effective in reducing forefoot pressures, but also why the orthotic device is effective. The goal of Aim 2 is to develop and validate three-dimensional computational models for estimating the effects of diabetic foot orthoses on peak plantar pressure and tissue deformation. Structural data from SXCT scans, material properties (plantar soft tissue and orthotic device), and external plantar pressure data from people with DM and peripheral neuropathy will be combined to develop and validate the three-dimensional computational model and methods. The validated model will be used to predict optimal characteristics of the total contact insert and metatarsal pad (i.e. material properties, size, and placement). The predicted orthotic device will be tested against the traditional orthotic device described in Aim 1 in a new set of patients for its ability to distribute forefoot plantar pressures evenly. Experimental testing will help to keep computational models realistic and valid while three dimensional computational modeling will enhance the scientific basis of orthotic design and testing.
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