Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Kinesiology

Faculty/School

Faculty of Science

First Advisor

Diane Gregory

Advisor Role

Supervisor

Abstract

Introduction: Disc herniations transpire when the nucleus pulposus (NP) within the intervertebral

disc (IVD) breaks through the surrounding annulus fibrosus (AF) (Gooyers et al., 2015). Disc

herniations have been demonstrated to be a result of cumulative damage brought on by repeated

flexion under compressive stresses (Aultman et al., 2005). Limited research has investigated the

changes in mechanical properties that occur as a consequence of disc herniation to the AF. Further,

it is not known if these changes are isolated to only the region of the herniation or the entire AF.

Aims: The purpose of the current work is to investigate if site specific changes to the mechanical

properties of the AF fibrosus post disc herniation.

Methods: A total of 30 porcine cervical spines were used (10 control, 10 static, 10 experimental).

The C3/4 and C5/6 functional spine units (FSUs) were excised from these spines and randomized

into groups via block randomization for each condition. The experimental porcine FSUs were

loaded into a uniaxial material testing system (MTS Systems Corporation, Eden Prairie, MN,

USA) under a compressive load of 1200 N, with repetitive cycles of off-axis bending at 30°, at 0.5

Hz to create herniation in the 10 experimental spines. The static FSUs were also loaded at 1200 N

compression but did not undergo repetitive flexion-extension. The control FSUs only underwent

preloading. The reasoning for the off-axis herniation protocol was to force the migration of the

nucleus (i.e., prolapse) to one side of the posterolateral region of the AF (Aultman et al, 2005).

This yielded a herniated region, and an internal control region of the posterolateral AF. Following

loading, two AF samples were excised from each of the herniated and the intact regions. Similarly,

from the control FSUs, two AF samples were excised from the left and right posterolateral region

of the disc. A lamellar adhesion peel test was conducted on one AF sample and a single lamellae

layer test was conducted on the other sample using the UStretch (Cellscale, Waterloo, Ontario)4

and Biotester (Cellscale, Waterloo, Ontario), respectively. Mechanical properties were quantified

from both tests. A two-way repeated measures ANOVA was conducted to examine the main effect

of condition (experimental, control, and static) and posterolateral side (ipsilateral and contralateral

sides), and the interaction between these two variables.

Results: 3/10 of the experimental IVDs showed evidence of nucleus tracking and thus herniation

in the posterior, and contralateral region to the bending axis. There was a statistically significant

(p= 0.03) difference in stress at toe region (mPa) when comparing the experimental group to the

control group. The control group had greater stress (M=0.29 MPa) at toe region than the

experimental group (M=0.068 MPa). There was also a statistically significant (p= 0.02) difference

in strain at toe region (mPa) when comparing the experimental group to the control group. The

control group had greater strain (M=0.19%) at toe region when compared to the experimental

group (M=0.13%). There was found to be a statistically significant difference between the

contralateral and ipsilateral sides of the IVD for peel stiffness regardless of loading condition

(p=0.01).

Discussion/Conclusion: The toe region of the stress-strain curve is where elastin largely

functions. From the current study, it is possible that fatigue-related degradation to the elastin

fibres occurred, which could have contributed to the separation of lamellae, eventually leading to

NP prolapse. The shorter toe region in the current study could be explained by damage to the

elastin fibres in the experimental group, which resulted in a disruption to elastin.

Convocation Year

2024

Convocation Season

Fall

Download

Available for download on Thursday, September 02, 2027

Share

COinS