Optimum Material Composition Design of Functionally Graded Material Artificial Hip Joint with Functions of Bioactivity and Dynamic Contact Stress Relaxation

功能梯度材料作为可重复使用的火箭发动机和空天飞机飞行体的轻量化结构材料之一，在医学领域也可用于制造具有新性能和重要功能的人造材料。在本研究中，基于弹塑性接触应力分析，对具有与活骨结合的生物活性和接触应力松弛功能的功能梯度材料组成的人工髋臼杯进行了材料组合设计。将人工髋臼杯假定为仅在径向上具有任意非均匀力学性能的非均匀空心半球，利用有限元方法对该半球内球面上受轴对称静、脉冲载荷作用时的静、动应力和位移进行了数值分析。(a)用PMMA骨水泥固定超高分子量聚乙烯杯；(b)用界面生物活性骨水泥将超高分子量聚乙烯杯固定在骨上；(c)带多孔aw -玻璃涂层的超高分子量聚乙烯杯，通过骨长入将多孔aw -玻璃涂层固定在涂层的孔隙中。此外，还对功能梯度材料人工髋关节的接触应力进行了分析。超高分子量聚乙烯（UHMWPE）的磨损是限制人工关节植入寿命的主要障碍。现在众所周知，超高分子量聚乙烯髋臼杯的磨损碎片引发一系列不良组织反应，导致髋关节骨溶解和松动。通过改善磨损行为来延长全髋关节置换术的使用寿命一直是骨科学界正在进行的研究课题。循环接触应力是造成超高分子量聚乙烯磨损的主要因素。因此，对在静、动载荷作用下股骨头与髋臼杯接触面及其附近具有静、动接触应力松弛功能的具有活骨生物活性的功能分级材料组成的人工髋臼杯进行了基于有限元弹塑性接触应力分析的材料组合设计。少

Functionally graded materials (FGMs) which have been developed as one of light-weight structural materials of the reusable rocket engine and flight body in space-plane, could be also applied to create artificial materials with new properties and significant functions in the medical field. In this study, a material composition design is performed based on elastic-plastic contact stress analysis for the artificial acetabular cup composed of functionally graded material having the bioactivity able to bond to living bone and the function of contact stress relaxation. The artificial acetabular cup is assumed to be a non-homogeneous hollow hemisphere with arbitrary non-homogeneous mechanical properties only in the radial direction, and then the static and dynamic stresses and displacements in the hemisphere subjected to axisymmetric static and impulsive loadings on the inner spherical surface, are analyzed numerically by using finite element method. The following three analysis models are us … More ed : (a)UHMWPE cup fixated to bone with PMMA bone cement ; (b)UHMWPE cup fixated to bone with interface bioactive bone cement ; and (c)UHMWPE cup with porous AW-glass coating fixated by bone ingrowth into the pores of the coating layer. Furthermore, the contact stress in the functionally graded material artificial hip joint is analyzed. The wear of UHMWPE is a major obstacle limiting the longevity of implanted artificial hi joint. It is now well known that the wear debris of UHMWPE acetabular cup initiates a cascade of adverse tissue response leading to osteolysis and loosening of the article hip joint. Extending the longevity of total hip joint replacements by the improvement of wear behavior has been the subject of ongoing research in the orthopaedic community. The major factor of the UHMWPE wear is the cyclic contact stress. So, material composition design based on FEM elastic-plastic contact stress analysis is performed for the artificial acetabular cup composed of functionally graded material having the bioactivity able to living bone and the relaxation function of static and dynamic contact stress on the contact surface and its neighborhood of the femoral head and the acetabular cup subjected to static and dynamic loadings. Less