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A New Slant on Shear Loading: Uncovering Its Effect on the Intervertebral Disc
Jacqueline Rosenberg1,2, Eliana Seider1,2, Sabrina I Sinopoli3
1Department of Health Sciences, Wilfrid Laurier University, Waterloo, ON N2L 3C5, Canada.
Journal of Biomechanical Engineering
|June 23, 2025
Summary
Prolonged anterior shear loading weakens intervertebral disc integrity by reducing the adhesive strength and stiffness of the annulus fibrosus. This damage may contribute to early-stage disc degeneration.
Area of Science:
- Biomechanical engineering
- Spinal research
- Tissue mechanics
Background:
- Intervertebral disc degeneration is a significant health concern.
- Anterior shear loading is a potential contributing factor to disc damage.
- Understanding the effects of shear on the annulus fibrosus is crucial.
Purpose of the Study:
- To quantify the mechanical properties of the annulus fibrosus after static anterior shear loading.
- To investigate the impact of shear on interlamellar adhesion within the annulus fibrosus.
- To determine if shear loading compromises intervertebral disc integrity.
Main Methods:
- Porcine cervical motion segments were used, isolating the intervertebral disc.
- Specimens were subjected to either 100 N static anterior shear or a control condition for 1 hour.
- Annulus fibrosus samples underwent circumferential tensile testing and peel testing for interlamellar adhesion assessment.
Main Results:
- Circumferential tensile properties of the annulus fibrosus remained unchanged after shear loading.
- Interlamellar adhesive stiffness decreased by 52% (p=0.02) in shear-loaded specimens.
- Interlamellar adhesive strength decreased by 46% (p=0.02) in shear-loaded specimens compared to controls.
Conclusions:
- Prolonged anterior shear loading significantly weakens the interlamellar matrix of the annulus fibrosus.
- This weakening reduces resistance to delamination, compromising overall disc integrity.
- Shear loading is implicated as a contributing factor to early-stage disc degeneration.
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