Schroeder Y, Elliott D M, Wilson W, Baaijens F P T, Huyghe J M
Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
J Orthop Res. 2008 Aug;26(8):1141-6. doi: 10.1002/jor.20632.
Finite element (FE) models have become an important tool to study load distribution in the healthy and degenerated disc. However, model predictions require accurate constitutive laws and material properties. As the mechanical properties of the intervertebral disc are regulated by its biochemical composition and fiber-reinforced structure, the relationship between the constitutive behavior of the tissue and its composition requires careful consideration. While numerous studies have investigated the annulus fibrosus compressive and tensile properties, specific conditions required to determine model parameters for the osmoviscoelastic model are unavailable. Therefore, the objectives of this study were (1) to complement the existing material testing in the literature with confined compression and tensile tests on human annulus fibrosus and (2) to use these data, together with existing nucleus pulposus compression data to tune a composition-based, osmoviscoelastic material constitutive law. The osmoviscoelastic material constitutive law and the experimental data were used to describe the fiber and nonfiber properties of the human disc. The compressive material properties of normal disc tissue were G(m) = 1.23 MPa, M = 1.57, and alpha = 1.964 x 10(-16) m(4)/Ns; the tensile fiber material parameters were E(0) = 77.0 MPa; E(epsilon) = 500 MPa, and eta = 1.8 x 10(3) MPa(-s). The goodness of fit ranged from 0.88 to 0.96 for the four experimental conditions evaluated. The constitutive law emphasized the interdependency of the strong swelling ability of the tissue and the viscoelastic nature of the collagen fibers. This is especially important for numerical models to further study the load sharing behavior with regard to disc degeneration and regeneration.
有限元（FE）模型已成为研究健康椎间盘和退变椎间盘中载荷分布的重要工具。然而，模型预测需要准确的本构定律和材料属性。由于椎间盘的力学性能受其生化组成和纤维增强结构的调节，因此组织的本构行为与其组成之间的关系需要仔细考虑。虽然众多研究已对纤维环的压缩和拉伸性能进行了调查，但确定渗透粘弹性模型参数所需的特定条件尚不可用。因此，本研究的目的是：（1）通过对人纤维环进行侧限压缩和拉伸试验，补充文献中现有的材料测试；（2）利用这些数据，结合现有的髓核压缩数据，调整基于成分的渗透粘弹性材料本构定律。渗透粘弹性材料本构定律和实验数据用于描述人体椎间盘的纤维和非纤维属性。正常椎间盘组织的压缩材料属性为：G(m)=1.23MPa，M = 1.57，α = 1.964×10^(-16)m^4/Ns；拉伸纤维材料参数为：E(0)=77.0MPa；E(ε)=500MPa，η = 1.8×10^3MPa·s。在所评估的四种实验条件下，拟合优度范围为0.88至0.96。本构定律强调了组织强大的肿胀能力与胶原纤维粘弹性本质之间的相互依存关系。这对于进一步研究椎间盘退变和再生的载荷分担行为的数值模型尤为重要。
