Author: John J. Souza

Publisher:

Published: 2007

Total Pages: 94

ISBN-13:

Human intervertebral disc replacement is quickly becoming a superior substitute for cervical disc fusion as a surgical treatment for degenerative disc disease. The current disc implants share similar materials and show significant improvements over past designs. Scientific studies continue to evaluate the results of the implants compared to fusion, with the primary focus placed on the preservation of normal spine biomechanics with the articulating abilities of the implant versus absence of motion with fusion. This thesis investigated the biomechanical effects on the spine with eccentricity of the implant. More specifically, implantation at a location that is laterally offset from the midsagital axis, thus yielding misalignment to the patient's left or right from the geometric vertical axis. This study concentrates on the three main joints in the cervical spine and the load distribution on them due to a static axial loading case only. Three separate evaluations were used to compare results. A mechanical testing apparatus that simulates eccentric implantation was designed, built, and tested. Numerical and mathematical models of this apparatus completed the trio of evaluations. The results showed a characteristic that is linear. That is, minor offsets in the order of millimeters demonstrate significant increases in static loads on the facet furthest from the implant. A consideration of these results and research suggests that this could be the cause of long-term facet degeneration. The conclusion of this thesis suggests future research is needed to further understand this phenomenon, improve the surgical technique, or improve the implant, all in order to either better understand the biomechanical sacrifices with eccentric implantation or eliminate it all together.