https://orcid.org/0009-0003-6658-2656
Abstract
Prolonged anterior shear loading may contribute to disc degeneration by damaging the annulus fibrosus. To address this, annular mechanical properties were quantified following static shear loading using a porcine model. Twelve porcine cervical motion segments were dissected, with posterior bony elements removed to isolate shear to the intervertebral disc. Specimens were randomized into two conditions: (1) shear-loaded (100 N static anterior shear applied to C3/C4, n = 6) or (2) control (0 N, n = 6). Shear force was applied via a pin through C4, secured to a testing system to prevent rotation, while C3 was clamped such that anterior shear of C3 with respect to C4 resulted. Following 1 h of loading, two anterior annulus samples were extracted per specimen. The first sample underwent circumferential tensile testing, while the other was prepared for a peel test to assess interlamellar adhesion. Tensile properties in the circumferential direction remained unchanged after shear loading. However, interlamellar adhesive stiffness decreased by 52% (p = 0.02), and adhesive strength dropped by 46% (p = 0.02) in shear-loaded specimens compared to controls. Shear loading weakened the interlamellar matrix, reducing resistance to delamination and compromising disc integrity. These findings suggest that prolonged shear loading may contribute to early-stage disc damage.
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