Żak Małgorzata, Pezowicz Celina
Department of Biomedical Engineering, Mechatronics and Theory of Mechanisms, Wroclaw University of Technology, ul. Łukasiewicza 7/9, 50-371, Wrocław, Poland.
Eur Spine J. 2016 Sep;25(9):2681-90. doi: 10.1007/s00586-016-4704-0. Epub 2016 Jul 13.
The aim of this study was to determine the impact of free hydration on the mechanical parameters of the annulus fibrosus (AF) of the intervertebral disc (IVD), determined in a standard manner. Attention was also given to the hydration occurring in real time and geometric changes resulting from swelling of the AF.
Uniaxial tensile tests of multilayer samples of the AF with bone attachment were performed for two groups: samples subjected to 30 min of hydration prior to the mechanical test, and control samples, which were not subjected to additional hydration.
As a result of hydration, the values of both the failure stress (σ UTS) and the tensile modulus (E) were lower than in the control group. A decrease in these values was observed for the AF from both the anterior and posterior parts of the IVD.
The tests showed a significant dependence of the determined mechanical parameters on the cross-sectional area. The larger the cross-sectional area, the lower the obtained value of stress. By contrast, the value of the stiffness coefficient is independent of the cross-sectional area. The differences in mechanical parameters are related mainly to water absorption into structures of the AF during hydration. This is confirmed by microscopic analysis of geometric dimensions of the AF during hydration conducted in real time. The greatest changes occurred in the radial direction, where the thickness increased by 2.05 mm, while in the axial direction the main change concerned an increase in height by 0.69 mm. There were negligible changes in the circumferential direction.
本研究的目的是确定以标准方式测定的自由水化对椎间盘纤维环（AF）力学参数的影响。同时还关注了实时发生的水化以及AF肿胀引起的几何变化。
对两组带有骨附着的AF多层样本进行单轴拉伸试验：一组是在力学试验前进行30分钟水化的样本，另一组是未进行额外水化的对照样本。
水化后，破坏应力（σ UTS）和拉伸模量（E）的值均低于对照组。在椎间盘前部和后部的AF中均观察到这些值的下降。
试验表明，所测定的力学参数与横截面积有显著相关性。横截面积越大，应力的所得值越低。相比之下，刚度系数的值与横截面积无关。力学参数的差异主要与水化过程中AF结构的吸水有关。实时进行的AF水化过程中几何尺寸的微观分析证实了这一点。最大的变化发生在径向，厚度增加了2.05毫米，而在轴向，主要变化是高度增加了0.69毫米。圆周方向的变化可忽略不计。
