Dissertation
A complementary experimental and computational modeling framework to assess the influence of carbon fiber bracing on ankle function and contact mechanics
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Summer 2024
DOI: 10.25820/etd.007605
Abstract
Post-traumatic osteoarthritis (PTOA) is common following severe ankle injuries, such as tibial pilon intra-articular fractures (TP-IAFs). TP-IAFs often lead to chronic elevated contact stress during daily activities, with debilitating PTOA predictably following. Exploring the potential efficacy of post-operative carbon fiber custom dynamic orthoses (CDOs) in mitigating PTOA risk by reducing plantarflexor muscle force, joint reaction force (JRF), and corresponding contact stress is the topic of the research here reported. A multi-faceted approach was employed, combining multi-scale computational musculoskeletal (MSK) modeling and cadaveric testing.
Kinematic and kinetic gait data from nine healthy subjects ambulating under various CDO conditions that were collected as part of a separate study were used as modeling input. A sequential multi-scale computational MSK modeling framework, implemented in OpenSim, was used to simulate the influence of CDO rotational stiffness on ankle loading and contact mechanics. This was followed by the first-time implementation of concurrent MSK modeling for the ankle, implemented in OpenSim using the previously reported Concurrent Optimization of Muscle Activations and Kinematics (COMAK) algorithm, to improve simulation accuracy. The concurrent framework enforces dynamic consistency between whole-body kinematics and joint-level contact stress. As proof-of-concept, input data from one healthy subject were used to study the influence of varied CDO stiffness upon contact stress.
Complementary cadaveric testing was also conducted to study the influence of CDO rotational stiffness on tibiotalar joint mechanics. A servohydraulic load frame was used to test five cadaver ankles, with axial loading and pneumatic actuation of the Achilles tendon serving to quasi- statically model multiple points in the stance phase of gait. Three CDO rotational stiffness v conditions were tested. JRF and contact stresses were measured using a piezoresistive pressure sensor inserted into the tibiotalar joint. CDO use decreased JRF, with associated decreases in contact stress, but results varied based upon CDO characteristics.
Taken together, results obtained using this complementary experimental and computational modeling framework demonstrate that CDOs can effectively support ankle moments, thereby reducing plantarflexor muscle force, JRF, and contact stress during midstance to terminal stance in healthy walking. However, the relationship between CDO characteristics studied and the resulting amount of stress reduction underscore the need for personalized CDO prescription.
Details
- Title: Subtitle
- A complementary experimental and computational modeling framework to assess the influence of carbon fiber bracing on ankle function and contact mechanics
- Creators
- Lucinda A Williamson
- Contributors
- Donald D. Anderson (Advisor)Jason Wilken (Committee Member)Nicole M. Grosland (Committee Member)M.L. Suresh Raghavan (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Biomedical Engineering
- Date degree season
- Summer 2024
- Publisher
- University of Iowa
- DOI
- 10.25820/etd.007605
- Number of pages
- xviii, 136 pages
- Copyright
- Copyright 2024 Lucinda A Williamson
- Language
- English
- Date submitted
- 07/20/2024
- Description illustrations
- illustrations, graphs, tables
- Description bibliographic
- Includes bibliographical references (pages 128-136).
- Public Abstract (ETD)
- Osteoarthritis (OA) that develops secondary to joint injury is classified as post-traumatic OA (PTOA). PTOA is an all too predictable outcome following ankle fracture with patients going on to experience functional deficits with persistent debilitating pain. When the ankle is fractured or otherwise injured, harmful elevated contact stress can arise. Ankles subjected to habitually elevated contact stresses, during routine daily tasks like walking, are known to rapidly develop disabling PTOA within a few years of the initial injury. Post-operative bracing with carbon fiber custom dynamic orthoses (CDOs) presents a non- invasive treatment option that can decrease ankle joint reaction force (JRF) and contact stress. Studies affirm widespread clinical CDO use, with patients across a range of pathologies experiencing significant reductions in pain, high levels of comfort, and improved gait function. The effectiveness of these orthoses is largely attributed to their personalized customization. However, clinicians face many design decisions that are subjective and not based on well- established prescription guidelines. This research set out to evaluate the role of CDO rotational stiffness in mitigating PTOA risk through preferential offloading of the limb. Computational modeling and concurrent simulation approaches were developed to analyze data from conventional gait analysis. CDO rotational stiffness was varied and its effect on gait kinematics, kinetics, and ankle contact mechanics were assessed. Simulation outputs were corroborated with cadaveric testing. Results indicated that CDOs supported ankle moments, thereby reducing peak plantarflexor muscle force, JRF, and corresponding contact stress during the late stance phase of gait. However, there was not a direct relationship between stiffness and contact stress reduction, suggesting the need for personalized CDO brace prescription.
- Academic Unit
- Roy J. Carver Department of Biomedical Engineering
- Record Identifier
- 9984698249702771
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