Investigation of Plantar Shear Stresses in Diabetic Patients: Relevance to Foot U

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DESCRIPTION (provided by applicant): Diabetic foot ulcers continue to burden US healthcare system with an annual cost of $11 billion and yearly amputation rates of 100,000. Unfortunately, the exact etiology of the problem remains to be resolved. Developing effective footwear and intervention strategies to prevent diabetic amputations requires a comprehensive understanding of the complication pathway. Diabetic foot lesions are known to have a biomechanical pathology that involves increased stresses acting under the foot. However, studies have shown that foot pressure alone is not a good predictor of ulcerations. This is due to the fact that ulcers might occur at pressure levels that are not considered harmful and locations that do not bear peak pressures. Preliminary studies suggest a relationship between diabetic foot ulcers and shear stress, the other mechanical component, which occur at the foot-ground interface. These studies demonstrated the importance of plantar shear by revealing elevated shear stresses in diabetic patients with respect to control subjects, while foot pressures remained the same. Studies by others have shown that frictional shear stresses are responsible for creating calluses, which are known to be strongly associated with the occurrence of diabetic foot lesions. The significance of shear stresses arises from the fact that they fundamentally act with twice the temporal frequency of pressure under the foot. It is hypothesized that diabetic foot wounds are associated with high frictional shear forces experienced on the plantar surface of the lower extremity. Unlike earlier preliminary studies, this study will investigate plantar shear stresses in a large sample of subjects classified under four groups and a location-wise relationship between foot lesions and frictional shear stresses. The first specific aim of this study is to investigate and compare peak shear stress values, which will be obtained by a custom-built device in a total of 153 subjects. These subjects will include; (a) diabetic neuropathic patients with an ulcer history, (b) diabetic neuropathic patients without previous ulcers, (c) diabetic control patients and (d) healthy individuals. The second specific aim will explore whether previous foot ulcers developed at peak shear locations, in patients with recently healed wounds. If the presence of such an association is confirmed, these data will provide invaluable information in the design of preventive approaches to lower the prevalence of diabetic foot wounds. Prevention of diabetic foot ulcers will lift not only the financial burden on the US healthcare, but also the physical and psychological burden on diabetic patients who are vulnerable to complication. PUBLIC HEALTH RELEVANCE: Although the exact etiology of the diabetic neuropathic foot ulcerations is still not known, it is thought that these lesions are directly related with increased frictional shear forces under the diabetic foot. If the hypotheses of this study are confirmed, then the US healthcare system will realize substantial savings by the effective design of preventive devices and approaches aiming at reducing the prevalence of diabetic foot ulcers. Furthermore, diabetic neuropathic patients, who have to face the risk of losing their limbs, will be provided with greater physical and psychological comfort.