Development of artificial intervertebral disc and artificial nucleus pulposus

(1)循环载荷下人体L4-5功能脊柱单元力学性能评价：对10个新鲜人体L4-5功能脊柱单元进行了循环轴向压缩-拉伸试验和循环扭转试验，以研究L4-5功能脊柱单元后部构件的结构影响。在每次载荷下，功能脊柱单元的刚度随位移的增加而增加，完整的功能脊柱单元和移除每个后路元件后的功能脊柱单元的刚度均相同。所有后路元件都对L4-5功能脊柱单元的压缩、拉伸和扭转刚度有贡献。棘突关节对抗压刚度和扭转刚度有显著影响。棘关节对扭转刚度的影响随位移程度的增大而增大，而对压缩刚度的影响不变。后韧带（棘上韧带和棘间韧带）对拉伸刚度有显著影响。(2)循环加载下人体L4-5椎间盘力学性能评价：通过循环压缩-拉伸和扭转试验，对10个新鲜人体L4-5椎间盘体单元（DBUs）的L4-5椎间盘刚度特性与位移的关系进行研究。我们还研究了纤维环损伤、核切除和硅胶弹性体填充去核间隙对L4-5椎间盘刚度特性的影响。各载荷类型下L4-5椎间盘刚度随位移的增大而增大，各载荷类型下核裂后椎间盘刚度在各位移区域均显著降低。用有机硅弹性体填充去核间隙，扭转刚度得到显著恢复。然而，压缩和拉伸刚度几乎没有恢复。(3)人工椎间盘的结构设计：提出了一种新的人工椎间盘来重建人体功能脊柱单元的稳定性和可移动性。通过三维有限元模拟设计了人工椎间盘的几何形状和结构，该模型的压缩刚度和扭转刚度与尸体腰椎间盘的刚度基本一致。因此，所提出的模型由两个生物活性陶瓷板和由橡胶样材料制成的干预子结构组成。含有磷灰石和硅灰石的玻璃陶瓷被选为与骨头接触的板的材料，因为这种材料能够与骨组织形成牢固的化学键。由于人工椎间盘与尸体腰椎间盘具有相同的刚度特性，因此在两板之间的下层结构中选择医用级弹性材料。少

(1) Evaluation of the mechanical properties of the human L4-5 functional spinal unit during cyclic loading : Cyclic axial compression-tension tests and cyclic torsional tests were performed on ten fresh human L4-5 functional spinal units to investigate the structural effects of the posterior elements of L4-5 functional spinal units.The stiffness of the functional spinal unit increased with increase of displacement under every loading, This was same in the intact functional spinal units and the functional spinal units after removal each posterior element, respectively. All the posterior elements contributed to the compressive, tensile, and torsional stiffness of L4-5 functional spinal units. The apophyseal joints had a significant effect on the compressive and torsional stiffness. The effect of the apophyseal joints on the torsional stiffness became greater according to the extent of displacement, whereas their effect on the compressive stiffness was constant. The posterior ligaments (s … More upraspinous and interspinous ligaments) had a significant effect on the tensile stiffness.(2) Evaluation of the mechanical properties of the human L4-5 disc during cyclic loading : Ten fresh human L4-5 disc-body units (DBUs) were examined for investigation of the relationship between the stiffness properties of L4-5 intervertebral disc and the displacement by cyclic compression-tension and torsion tests. The effects of an injury to the anulus fibrosus, nucleotomy and the filling-up of the denucleated space with silicone elastomer on the stiffness properties of L4-5 disc were also investigated.The stiffness of L4-5 intervertebral disc increased with the increase of displacement in every type of loading, In each type of loading, the stiffness of the intervertebral disc after nucleotomy decreased significantly in every region of displacement. The torsional stiffness was restored significantly by the filling-up of the denucleated space with silicone elastomer. However, there was little restoration of both the compressive and tensile stiffness.(3) Structural design of an artificial intervertebral disc : A new artificial intervertebral disc is proposed to reconstruct the stability and mobility of a human functional spinal unit. The geometry and the structure of the artificial intervertebral disc were designed by the computer simulation at 3D-FEM, as the compressive and the torsional stiffness of this model agree with the stiffness of cadaveric lumbar discs.Consequently, the proposed model consists of two bioactive ceramic plates and intervenient substructure made from rubber-like materials. Glass-ceramic containing apatite and wollastonite was chosen as a material for the plates which come into contact with the bone, because this material is able to form a strong chemical bond with the osseous tissue. Elastic materials of medical grade in the substructure between two plates were selected, as a the artificial disc has the same stiffness properties with a cadaveric lumbar disc. Less