Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Health Science

Faculty/School

Faculty of Science

First Advisor

Diane Gregory

Advisor Role

Supervisor

Abstract

Introduction: Low back pain is a leading cause of disability worldwide and is commonly associated with intervertebral disc degeneration (IDD) and lumbar disc herniation (LDH). Nucleus replacement strategies alone may be insufficient when annular integrity is not restored, as persistent annular defects can compromise disc containment and mechanical stability. Currently, there is no established approach for simultaneously restoring nucleus function and repairing annular defects.

Aim: This study evaluated whether a dual repair approach combining nucleus hydrogel augmentation with annular closure, better preserved intervertebral disc (IVD) height under combined physiological loading compared with hydrogel augmentation alone.

Methods: Porcine cervical functional spinal units (FSUs) (C3/4 and C5/6) were randomly assigned to four experimental conditions: control, injury, hydrogel, and dual repair. Injury consisted of a standardized 3.5-mm posterior annular puncture followed by partial nucleotomy. A glycerol-crosslinked polyvinyl alcohol hydrogel was used for nucleus augmentation, while genipin-crosslinked fibrin (FibGen) was used for annular closure. Specimens underwent 3,000 cycles of combined loading at 0.5 Hz under 1,200 N axial compression and cyclic flexion–extension. IVD height difference was determined from the mechanical testing system actuator position pre- and post- fatigue loading. Following mechanical testing, annular adhesion properties were assessed using a 180° T-peel test.

Results: Experimental condition significantly affected disc height loss (p < .001), with the injury group demonstrating significantly greater height loss than the control, hydrogel, and dual-approach groups (all p < .0001). Disc height loss did not differ significantly between either treatment group and the control group, or between the hydrogel and dual-approach groups. Experimental condition also significantly affected annular peel stiffness (p = .025) and peel strength (p = .002) but not peel-strength variability (p = .141). The dual approach demonstrated significantly greater peel stiffness than injury (p = .021) and significantly greater peel strength than both injury (p = .001) and control (p = .0497). No significant effects of annular region or Condition × Annular Region interactions were observed for any peel-test outcome.

Conclusion: GPG hydrogel augmentation, both alone and in combination with FibGen annular repair, reduced disc height loss associated with injury to levels comparable with uninjured controls. The dual approach additionally demonstrated greater annular interlamellar stiffness and strength, suggesting a potential mechanical benefit of simultaneously addressing nucleus material loss and annular disruption. Together, these findings support further investigation of combined nucleus augmentation and annular repair as a strategy for restoring intervertebral disc mechanical function following injury.

Convocation Year

2026

Convocation Season

Fall

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Available for download on Wednesday, August 30, 2028

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Biomechanics Commons

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