• K Josh Briar and Diane E Gregory.
• Department of Kinesiology and Physical Education, Wilfrid Laurier University, Waterloo, ON, Canada.
• Eur Spine J. 2023 Mar 1; 32 (3): 831838831-838.

PurposeTo observe the effect of static flexion, in combination with compression, on the intralamellar and interlamellar matrix properties of the annulus fibrosus.MethodsC3/C4 cervical functional spinal units of porcine specimens were selected. Following preloading, all specimens were loaded under 1200 N axial compression in either a neutral or static end range flexion posture (15º) for 2 h. Following loading, six annulus samples were dissected from each disc: four single-layer and two multi-layer samples. The multi-layer samples underwent peel tests to quantify the mechanical properties of the interlamellar matrix while the single-layer samples underwent tensile tests to quantify the mechanical properties of the intralamellar matrix. Statistical comparisons between properties were performed to determine differences between postural condition, extraction location, and extraction depth.ResultsFlexion elicited a decrease in lamellar adhesive strength (p = 0.045) and in single-layer failure strain (p = 0.03) when compared to a neutral posture. Flexion also had extraction depth-specific effects namely increased intralamellar matrix stiffness in the inner annulus when compared to neutral (p = 0019). Flexion also resulted in a significant decrease in toe region strain for the inner region of the annulus (p = 0.035). The inner region of the annulus was shown to have a significant increase in stress at 30% strain when compared to the outer region after flexion (p = 0.041).ConclusionThe current findings suggest that the mechanical properties of the interlamellar and intralamellar matrices are sensitive to flexion, creating an environment that promotes an increased potential for damage to occur.© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

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