Date of Award

5-2005

Document Type

Thesis

Degree Name

Doctor of Philosophy (Medical Science)

Program

Biomedical Engineering

Research Advisor

Denis DiAngelo, Ph.D.

Committee

James Robertson, Ph.D. Michael Yen, Ph.D. Richard Kasser, Ph.D. Teong Tan, Ph.D.

Keywords

cervical spine, dynamic multibody model, virtual simulation, axial rotation, in vitro testing; mounting configuration, adjacent segment disease, biomechanics, fusion, disc arthroplasty

Abstract

Utilizing recent advances in computer technology, Our Biomechanics Laboratory have made an effort to integrate computer animation and engineering analysis software into biomedical research, specifically towards simulation and animation of in vitro experimentation of the human cervical spine in the virtual world. The objectives of this study were to develop a virtual model of the human cervical spine for physics-based simulation and to apply the virtual model to studies of different surgical procedures and instrumentation.

A process for creating an accurate virtual model of the human cervical spine was developed. The model consisted of seven vertebrae (C2-T1) connected with soft tissue components: intervertebral joint, facet joints, and ligaments. The soft tissue components were assigned nonlinear viscoelastic properties. The evaluation of the model included the percent contribution of rotation relative to global rotation, coupling behaviors, helical axes of motion pattern, global rotational stiffness curves, and animations of the disc and facet forces. This model was used to evaluate different mounting configurations for axial rotation testing and to identify a set of end constraint conditions that produced physiologic responses during axial rotational loading. This model was also used to simulate the biomechanical responses of single-level cervical fusion.

The single-level fusion was found to produce increased motion compensation at the adjacent segments during flexion and extension. Greater increases in the disc forces were found in the spinal level superior to the fusion during flexion and inferior to the fusion during flexion extension. This model was also used to study of the biomechanical effects of different design features for cervical disc arthroplasty. A constrained spherical joint placed at the disc level significantly increased facet loads during extension. Lowering the rotational axis of the spherical joint into the subjacent body also caused a marginal increase in facet loading during flexion, extension, and lateral bending. Un-constraining the spherical joint to a plane at the disc level minimized facet load build up.

The virtual model bridges the gap between the cadaveric-based in vitro tests and clinicalbased experimental studies to further the research and educational knowledge of cervical spine biomechanics.

DOI

10.21007/etd.cghs.2005.0008

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