RR&D Research Career Scientist Award Application

Va Puget Sound Healthcare System, Seattle WA

Investigators

Linked publications & trials

Abstract

PROJECT SUMMARY/ABSTRACT Dr. Ledoux’s current research activity aims to reduce both functional and anatomical limb loss by: exploring the disease processes that lead to aberrant limb function; quantifying the effects of conservative and surgical treatment options; and developing novel, state-of-the-art technologies for studying the foot. His research focuses on two veteran populations: those with musculoskeletal impairment at the foot and ankle, where pain and limitations in mobility are the key issues (i.e., functional limb loss); and those at risk of lower limb amputation due to diabetes and foot ulceration, where loss of the foot or leg is a major concern (i.e., anatomical limb loss). The overarching goals of his research include: (1) insight into the pathomechanics of: diabetic foot ulceration, ankle and midfoot arthritis, and severe foot deformities; (2) quantitative comparison of different treatment options for foot deformities/pathologies that can lead to improved limb function or prevention of amputation; and (3) the development of novel research tools that can be employed in a wide range of clinical studies. This third goal is implicit in the first two, but has and will continue to guide much of Dr. Ledoux’s research efforts. For instance, his lab has developed a state-of-the-art cadaveric gait simulator that has been licensed by another foot biomechanist/clinician group. Additionally, he has invested significant resources in the development and validation of his biplane fluoroscope, which is one of only a few primarily designed to study the foot and ankle. Moving forward, two areas of research will dominate Dr. Ledoux’s efforts. First, he has a funded VA Merit Review (RX002008) to study how in-shoe foot orthoses achieve improvements in foot and ankle function for people with ankle osteoarthritis (OA) and/or adult acquired flatfoot. These are common, painful, and often highly debilitating conditions, and it has been shown that foot orthoses can be an effective conservative intervention that can help to postpone or negate the need for surgery. Measuring how the individual bones of the foot move using traditional motion analysis techniques is very difficult due to the size and position of the foot bones, and because of soft tissue artifact, which introduces significant errors into the measurements. This is further complicated by the need to wear shoes to use orthoses. The biplane fluoroscopy system can accurately measure foot bone kinematics throughout the stance phase, and has the advantage of being able to measure the effects of foot orthotics in shoes. This project will improve our understanding of how foot orthotics work and will help us to prescribe and design more effective devices to meet the needs of individual patients. This will benefit the large number of veterans who suffer from ankle osteoarthritis and adult acquired flat foot. Second, Dr. Ledoux has a recent NIH proposal entitled “Reducing Internal Stresses in Deformed Diabetic Feet” that was well scored (20 percentile); if not funded, it will be resubmitted. The structure of the foot, combined with the intrinsic tissue properties, dictates the loading within the tissue. Aberrant internal stresses are thought to be associated with diabetic, neuropathic ulceration, but due to methodological difficulties, it is not possible to quantify these stresses in living subjects. Computer modeling, however, is a technique that can be used to explore this issue; recent finite element foot modeling studies are suggestive of aberrant internal stresses in diabetic feet. The purpose of this study is to use a novel, anatomically detailed, patient-specific computational model to explore how foot deformity and stiffer diabetic tissues can lead to increased internal stresses, and to quantify how conservative and surgical treatment options can modulate these stresses. We will use an MRI- compatible loading device to develop patient-specific computational foot models of subjects that are: i) healthy, ii) diabetic neuropathic, and iii) diabetic neuropathic with claw toes. Both conservative (i.e., insoles) and surgical (i.e., correction of clawed toes) treatments will be modeled. This will improve clinical understanding of how subtle differences in tissue properties and foot shape alter internal stress and change the risk for ulcer development.