| Abstract | Study Design. An original investigation that characterizes poly (vinyl alcohol) cryogel (PVA-C) in the context of the human lumbar intervertebral disc. Objectives. To evaluate the mechanical properties of PVA-C under physiological conditions; to assess PVA-C's suitability as a tissue-mimicking artifical lumbar intervertebral disc material; and to identify suitable formulations that mimic the nucleus pulposus and annulus fibrosus. Summary of Background Data. Current lumbar intervertebral disc prostheses provide suboptimal symptom relief and do not restore natural load-cushioning. PVA-C is a promising material due to its high water content, excellent biocompatibility, and versatile mechanical properties. Methods. PVA-C samples were prepared with different PVA concentrations and number of freeze-thaw cycles (FTC). Unconfined compression was conducted to charaterize various PVA-C formulations. Compressive stress relaxation and creep were performed to assess the stability of PVA-C under loading. The results were compared with the mechanical properties of human lumbar intervertebral disc obtained from the literature. Results. PVA-C compressive elastic modulud increases with increasing PVA concentration and number of FTC's. The 3%-3FTC is the optimal formulation for mimicking the nucleus pulposes. In general, compressive stree relaxation and creep decreased with increasing PVA concentration and number of FTC's. Compressive stree relaxtion and creep were lower for PVA-C than human lumbar intervertebral discs, suggesting that PVA-C will likely exhibit stable and predictable mechanical response in-vivo. Current formulations did not have adequate compressive elastic modulus to mimic the annulus fibrosus. Conclusion. The 3%-3FTC PVA-C formulation is likely the optimal choice for a tissue mimicking artifical nucleus pulposus. Good compressive stress relaxation and creep behavior, combined with excellent biocompatibility, make PVA-C a suitable choice for a tissue-mimicking artificial IVD. Future investigations will focus on increasing the stiffness of PVA-C by approximately an order of magnitude in order to mimic the material properties of the annulus fibrosus. |
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