Date of Award

Fall 2002

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Biomedical Engineering

First Advisor

Pintar, Frank A.

Second Advisor

Silver-Thorn, M. B.

Third Advisor

Yoganandan, Narayan

Abstract

Cervical spondylosis is a disorder that affects the spinal columns of elderly persons. It is a progressive disorder that starts in the intervertebral discs, affects all of the adjacent tissues, and ultimately leads to the endangerment of the surrounding nerve roots and the spinal cord. To better understand how the initial stages of degeneration affect the stability of the cervical spine, a kinematic analysis was performed on normal and degenerated cervical spines. Differences found in the responses will aid early detection and treatment of cervical spondylosis. It is thought that an unstable phase exists during the initial stages of the degeneration process. The goal of this study was to quantify the biomechanical response of the degenerated cervical spinal column during this phase and compare it to normal (non-degenerated) spines. Therefore, it was hypothesized that during the initial stages of spondylosis both the translational and rotational sagittal plane motions would increase at the level of degeneration. Additionally, it was hypothesized that the coronal and transverse plane motions, as well as the motions at the nondegenerated levels of the spinal column would not demonstrate differences as compared to the normal group. The hypotheses were tested in vitro through the application of pure moment loading and combined loading on a full column cervical spine model. A controlled comparison of the kinematics associated with normal, C5-C6 disc degenerated, and C5-C6/C6-C7 disc degenerated spinal columns was achieved by comparing three distinctly different groups of specimens. Pure moment loading was applied in flexion, extension, lateral bending and axial rotation. Each plane of motion was analyzed separately to determine how the asymmetric anatomy of cervical vertebrae is affected by spondylosis. Loads up to 2.0 Nm were applied in each direction and the resultant rotational and translational motions and bending stiffnesses were measured about all three axes. Combined loading was performed to measure the total column bending stiffness in compression-flexion, compression-extension and compression-lateral bending. Loads up to 90N were applied at a distance of 10 cm from the center of the spinal column. Results indicate that the mobility at both the degenerated and the adjacent discs are affected by spondylosis. Under extension loading, the degenerated joint displayed both rotational and translational hypermobility. Conversely, under flexion loading, hypomobility was found in single-level disc degenerated group at the inferior, adjacent joint and at the inferior, degenerated joint in two-level disc degenerated group. When axial rotation and lateral bending were applied, the degenerated joints displayed a decreased amount of mobility. These results suggest that clinicians can use lateral sagittal plane radiographs, especially in extension, to evaluate the initial stages of the degeneration process and possible future symptomatic conditions. Additionally, the knowledge of which planes of motion are most affected will help improve treatment methods and surgical techniques. Collectively, these results will aid the reduction of morbidity for cervical spondylosis.

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