Additive manufacturing of an intervertebral disc repair patch to treat spinal herniation
Date
2021
Authors
Page, Mitchell Ian, author
Puttlitz, Christian, advisor
Heyliger, Paul, committee member
Susan, James, committee member
Kirk, McGilvray, committee member
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Volume Title
Abstract
Chronic low back pain is ubiquitous throughout society. The consequences of this disease are extensive and lead to physical, mental, and financial suffering in the affected population. Herniation of the intervertebral disc (IVD) is the primary cause of chronic low back pain due to the essential mechanical role of the IVD in the spinal column. Degenerative changes to the IVD tissues, in particular the annulus fibrosus (AF), lead to a pronounced vulnerability to herniation. Although numerous treatments for intervertebral disc herniation currently exist, these treatments are typically palliative and prone to hernia recurrence. Accordingly, there is a distinct need for an IVD hernia therapy that can provide long-term pain relief and recovery of spinal function. One novel strategy to repair the intervertebral disc is to tissue-engineer a construct that facilitates regeneration of the healthy and functional IVD tissue. Advances in additive manufacturing technology offer the fabrication of complex tissue-engineered structures that augment biological content and biocompatible materials. Therefore, this work sought to engineer an additive manufactured repair patch for IVD herniation towards an improved treatment for chronic low back pain. Specifically, the aims of this work were to leverage experimental and computational methods to: (1) to characterize the mechanics of additive manufactured angle-ply scaffolds, (2) evaluate the tissue response of cell-laden scaffolds cultured with dynamic biaxial mechanical stimuli, and (3) to design and implement an annulus fibrosus repair patch. The mechanics of additive manufactured scaffolds for AF repair were experimentally characterized in a physiologically-relevant, biaxial loading modality. To assess sensitivity of the scaffold mechanics to additive manufacturing parameters, a broad scope of scaffold designs were evaluated with a parameterized finite element model. A custom incubator was developed, cell-laden scaffolds were cultured with a prescribed, multi-axial mechanical loading protocol, and ECM production within the scaffold was evaluated. A finite element model was developed to aid in understanding the relationship between global scaffold loading and the local, inhomogeneous cellular micromechanical environment within the scaffold. The developed TE material was translated into an implant and was implemented in a large animal model. The efficacy of the AF repair strategy was also evaluated in finite element model of the human lumbar spine. This work formed a multi-scale approach to consolidate biological and mechanical efficacy of a novel AF repair strategy. Ultimately, this approach may facilitate regeneration of the AF and represent a revolutionary treatment for chronic low back pain.
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Subject
annulus fibrosus
intervertebral disc
tissue engineering
biomechanics
additive manufacturing
spine