Integration of Cervical Nervous Tissues into a Head-Neck Finite Element Model for the Investigation of Radiculopathy
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URI
Date
July 2024
Access
2026-07-01
Authors
Bruns, Rachel Elaine
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Publisher
East Carolina University
Abstract
Radiculopathy of the spine is a prevalent chronic disorder caused by a wide number of pathologies, affecting up to 10% of individuals over the age of 50 (Mansfield et al., 2020). It is caused by compression of the nerve roots within the spinal column and intervertebral foramen of the spine as they travel from the spinal cord distally to the rest of the body. While cervical radiculopathy is prevalent within the common aging population, recent concern has been raised at the increasing incidence of reported neck pain in fighter pilots, helicopter pilots, and crewmen (Ang & Harms-Ringdahl, 2006; Harrison et al., 2015; Posch et al., 2019; Walters PL et al., 2012). Repetitive loading activities such as wearing heavy helmets can cause compression of the spine which could be contributing to chronic neck pain, decreasing quality of life and safety while operating aircraft (Mansfield et al., 2020; Van den Oord et al., 2012).
Due to the ethical concerns of researching loading the neck in human experiments, mechanisms of nerve root pain and potential radiculopathy can be investigated using finite element (FE) modeling, which is a computational method that utilizes constitutive mathematical equations to simulate mechanical behavior of one or multiple components under loading conditions. While there has been development of many FE models of the cervical spine for different applications (Ah Shin et al., 2016; Khuyagbaatar et al., 2017, 2018; H.-J. Kim et al., 2009; Mihara, 2017; Xue et al., 2021, 2023), to our knowledge, no previous studies investigated cervical radiculopathy, nerve root compression, or the soft-tissue interaction within the spinal canal and intervertebral foramen (IVF). In this thesis, the focus was on the development and implementation of the nerve root geometry and surrounding ligaments into a full model of the cervical spine. The Nerve CSM (Cervical Spine Model) was developed in this thesis by adding nervous tissue to an existing head-neck model, the VIVA Open Human Body Model (OpenHBM) published by (Östh et al., 2017). The VIVA OpenHBM already contained a skull, vertebrae, intervertebral discs, vertebral ligaments, passive muscles, and surrounding soft tissues. The nervous tissue modeled and incorporated into the VIVA OpenHBM to create the new Nerve CSM in this thesis encompassed gray and white matter of the spinal cord, cerebrospinal fluid, dura mater, root sheaths, spinal nerves, nerve roots, dorsal root ganglions, nerve rootlets, denticulate ligaments, foraminal ligaments and epidural ligaments. Geometry was created in SolidWorks (SOLIDWORKS 2023, Dassault Systèmes-SolidWorks Corporation, Waltham, MA, USA) using anatomical measurements from the literature the part’s meshes were generated in ANSYS. These meshes were incorporated into the VIVA OpenHBM in LS-Prepost (LS-PrePost 4.10, © 2024 DYNAmore GmbH, an Ansys Company, Hauptniederlassung Stuttgart) , where the nerve rootlets, denticulate ligaments, foraminal ligaments, and epidural ligaments were created using discrete tension-only spring elements.
Validation of the Nerve CSM’s global head and spinal cord kinematics was performed by replicating the 2.3 m/s whiplash simulation published by (Östh et al., 2017) and the flexion/extension simulations published by (Stoner et al., 2019). The global head kinematics of the Nerve CSM in the 2.3 m/s whiplash simulation did not change substantially compared to the VIVA OpenHBM. Additionally, the correlation score for the time response of the Nerve CSM compared to the experimental data was similar to the VIVA OpenHBM, thus, it is reasonable to conclude that the addition of the nerve geometry did not considerably alter the global kinematics of the VIVA OpenHBM. The results of the spinal cord kinematic validation of the Nerve CSM demonstrated that the spinal cord during flexion and extension of the head moved within the bounds of variation presented in the experimental data (Stoner et al., 2019), pointing to a conclusion that the Nerve CSM demonstrates suitable spinal cord kinematics for a healthy participant. Future work will encompass the integration of the Nerve CSM into subject-specific pilot neck models to investigate the effect of cervical spine compression and flight related loading conditions on the interaction between the nerve roots and surrounding tissues.