The long-term objective of this research is to determine the contribution of foot progression angle (FPA), a spatial gait variable that represents foot rotation in the transverse plane, to the development of neuropathic plantar ulcers in adults with diabetes mellitus and peripheral neuropathy (DMPN). Clinical Significance: There are approximately 80,000 non-traumatic lower extremity amputations annually in the United States, 84% of which are preceded by neuropathic plantar ulcers. Adults with DMPN are at high risk for neuropathic plantar ulceration secondary to increased peak plantar pressure under bony prominences on an insensate foot. Therefore, peak plantar pressure is frequently used as a proxy measure of risk for skin breakdown and subsequent non-traumatic lower extremity amputation. Preliminary studies suggest a direct relationship between excessive external FPA and the timing and magnitude of medial peak plantar pressure in children with neurological pathology and in adults with DMPN. Given that adults with DMPN have nearly three times the rate of functional mobility deficits associated with lower extremity impairment than their healthy counterparts, it is imperative to improve our understanding of the contribution of excessive external FPA to the impairment cascade of excessive medial peak plantar pressures, medial neuropathic plantar ulceration, and non-traumatic lower extremity amputation. Unexplored areas of research: Despite the strong relationship between excessive external FPA and plantar pressure, to our knowledge there are no studies that have examined joint mobility limitations that contribute to FPA in individuals with DMPN. Furthermore, there are no studies probing whether excessive external FPA can be reduced in adults with DMPN, thereby creating a potential strategy for early rehabilitation intervention in the non-traumatic lower extremity amputation impairment cascade. Our proposed research seeks to improve understanding of specific movement impairments that contribute to increased external FPA magnitude in adults with DMPN, and if those impairments are amenable to early intervention.
Aim 1 : Determine the characteristics of FPA in groups of subjects with diabetes mellitus without peripheral neuropathy (DM only), without diabetes mellitus (CON), with diabetes mellitus and peripheral neuropathy WITH a history of neuropathic plantar ulcers (DMPN [+] NPU), and with diabetes mellitus and peripheral neuropathy WITHOUT a history of neuropathic plantar ulcers (DMPN [-] NPU).
Aim 2 : Determine ability of select lower extremity joint variables to predict FPA magnitude;
Aim 3 : Determine the effect of reducing FPA on medial peak plantar pressure in individuals with diabetes with excessive FPA magnitude. Expected outcomes: We hypothesize that foot, ankle, and hip joint motion limitations contribute substantially to excessive external FPA magnitude in adults with DMPN. We also hypothesize that after instruction, participants with DMPN can intentionally reduce their FPA, resulting in concomitant decreases in medial peak plantar pressure.

Public Health Relevance

Knowledge gained from these findings will clarify our understanding of risk factors for the development of a region-specific foot ulcer, an impairment associated with non-traumatic lower extremity amputation, in individuals with diabetes across a broad spectrum of disease severity. Furthermore, we will determine the impact of risk factor modification on pressure variables that serve as indices of risk for foot ulcer development using non-invasive, cost-effective intervention strategies.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Predoctoral Individual National Research Service Award (F31)
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Special Emphasis Panel (ZDK1-GRB-R (M1))
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Mcbryde, Kevin D
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Washington University
Other Health Professions
Schools of Medicine
Saint Louis
United States
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Merriwether, Ericka N; Hastings, Mary K; Bohnert, Kathryn L et al. (2016) Impact of foot progression angle modification on plantar loading in individuals with diabetes mellitus and peripheral neuropathy. Edorium J Disabil Rehabil 2:15-23