Résumé
Nous avons étudié les propriétés mécaniques d'échantillons d'anneau fibreux de disques lombaires humains soumis à la tension. La première partie de ce travail étudie l'effet de la taille de l'échantillon et de la rupture du collagène sur le résultat obtenu. Des tranches verticales de disque de 5 mm d'épaisseur et de 30 mm de largeur ont été taillées à partir des bords latéraux de l'annulus et des corps vertébraux adjacents. Les extrémités osseuses de chaque tranche ont été fixées dans un appareil destiné à tester les matériaux de manière à ce que l'annulus puisse être étiré verticalement, comme cela se produit lors des mouvements de flexion du rachis dans la vie courante. La raideur sous tension a été mesurée de manière répétitive après réduction de la taille effective de l'échantillon par des sections verticales successives de l'annulus. La raideur (par unité de surface) a diminué avec la taille du spécimen. La longueur moyenne des faisceaux de fibres de collagène dans les échantillons étudiés a été calculée à partir d'un modèle géométrique et il apparaît qu'elle est proportionnelle à la raideur sous tension. L'extrapolation des résultats a suggéré que la rigidité verticale et la solidité d'échantillons d'annulus de 15 mm de largeur devrait se situer autour de 44% de leur valeur in-situ. En conclusion, les fibres de collagène doivent être en continuité pour renforcer l'annulus, et les interactions fibresmatrice contribuent largement à la rigidité sous tension et à la résistance.
Summary
We investigated the tensile properties of samples of human lumbar annulus fibrosus. Here we consider the effect of sample size, and hence collagen disruption, on the results obtained. Vertical slices, 5 mm thick and 30 mm wide, were cut from the lateral margins of the annulus and adjacent vertebral bodies. The bony ends of each slice were secured in a materials testing machine so that the annulus could be stretched vertically, as occurs during bending movements of the spine in life. Tensile stiffness was measured repeatedly after successive vertical cuts in the annulus had reduced the effective size of the sample. Stiffness (per unit cross-sectional area) decreased as the specimen size decreased. The mean length of collagen fibre bundles in the specimens was calculated from a geometrical model and shown to be proportional to the tensile stiffness. Extrapolation of the results suggested that the vertical stiffness and strength of 15-mm-wide specimens of annulus would be about 44% of their values in situ. We conclude that collagen fibres need not be continous to reinforce the annulus and that fibre-matrix interactions make a large contribution to the tensile stiffness and strength.
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Adams, M.A., Green, T.P. Tensile properties of the annulus fibrosus. Eur Spine J 2, 203–208 (1993). https://doi.org/10.1007/BF00299447
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DOI: https://doi.org/10.1007/BF00299447