Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Biomedical Engineering

Supervisor

Dr. Wankei Wan

Abstract

Spinal fusion is currently the gold standard for surgical intervention of intervertebral disc (IVD) diseases leading to neck and back pain failing conservative treatments. However, fusion removes motion between the vertebrae and can result in adjacent level degeneration. Total disc replacement (TDR) is an emerging treatment alternative that preserves motion, but materials found in clinically available devices bear little resemblance to the properties of the native IVD. Poly(vinyl alcohol) (PVA) hydrogels are biocompatible, have mechanical behaviour similar to natural tissues, and properties that can be tuned by varying polymer concentration and physical crosslinking through freeze-thaw cycling. Furthermore, their properties can be modified with the addition of nanofillers. In the present study, PVA hydrogels and its nanocomposites containing Laponite and bacterial cellulose (BC) were investigated in compression and crossing-paths wear for potential application in cervical TDR. While increases in PVA concentration increased stiffness and decreased time-dependent response in neat PVA hydrogels, viscous response increased with nanofiller addition. BC addition also increased stiffness of the hydrogels without large changes in water content. To measure wear in the hydrogels, a technique using three-dimensional ultrasound imaging was developed. Wear volume and depth decreased with decreasing water content, while fatigue wear was eliminated with the addition of nanofillers in crossing-paths wear. Finally, a two-component PVA hydrogel demonstrated that compression properties could be tailored by mimicking the natural IVD structure. These results indicated that various parameters could be used to optimize the properties of PVA and PVA-nanocomposite hydrogels for applications in cervical TDR.

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