PhD Dissertation - Investigations of Polyethylene Damage Modes of Lumbar Total Disc Replacement

Abstract

Discogenic lower back pain results in a substantial reduction in the quality of life and affects a significant portion of the world’s population. Currently, the gold standard for surgical intervention involves removing the lumbar intervertebral disc, which is thought to be causing the pain and fusing the adjacent bony vertebrae. This practice has existed for almost a century, and generally results in successful clinical outcomes. However, the lack of flexibility at the fused segment may lead to degenerated discs at adjacent levels. As a result, disc replacement technologies have been introduced as a motion preserving alternative to spinal fusion. Like preceding hip and knee replacements, these devices typically involve articulating bearing surfaces, which pose the potential for similar clinical failure modalities. Specifically, impingement of these devices can lead to accelerated polyethylene wear. Despite the relatively recent introduction of these devices, osteolysis has been reported in a small number of cases. Therefore, a better understanding of the biomechanical environment associated with impingement is needed in order to properly assess device performance. The current dissertation outlines several studies, which evaluated the biomechanics of total disc replacement. Specifically, an in situ model of lumbar total disc replacement impingement was generated and validated based on clinical data from retrieved implants. The clinical parameters associated with impingement sensitivity were also determined in order to provide better guidance to both clinicians and designers.