Design of orthopedic implants made of porous metallic materials using additive manufacturing technologies

使用增材制造技术设计由多孔金属材料制成的骨科植入物

• 批准号: RGPIN-2017-05958
• 负责人: Nuño, Natalia
• 金额: $ 1.82万
• 依托单位: École de technologie supérieure
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=661077
• 关键词: Design; orthopedic; implants; made; porous

Long-term survivorship of orthopedic implants remains a challenge as patients are becoming younger and more active. One factor compromising the longevity of the implant is bone resorption believed to be due to stress shielding. Bone is a living tissue and reacts to its mechanical stimuli. When bone is removed to be replaced by an artificial implant, a redistribution of the stresses within the bone occurs. This stress shielding phenomenon occurs because of the large difference in rigidity between the metallic implant and the surrounding bone. The bone is thus stress shielded, consequently the bone is resorbed and its density decreased, eventually leading to failure of the arthroplasty. New materials are needed to mimic the natural bone to reduce the stress shielding phenomenon.****Nowadays, additive manufacturing technologies make possible complex, well-controlled porous materials such as metals with high porosity (50-80%) having material properties tailored to the desired need. Such new materials can be used to design implants with reduced stiffness to diminish the stress shielding. Furthermore, they allow for good osteointegration within the porosity (cell growth through the implant for appropriate stability). Infinity of structures at the mesoscale can be fabricated, thus infinity of mechanical properties can be designed. The implant can be functionally graded by having regions of high porosity and other regions with less porosity or no porosity. Finally, customized implants adapted to each patient can be manufactured.****The aim of this research program is to design and model new porous metallic materials obtained using additive manufacturing technologies for orthopedic applications. Numerical modeling is widely used to predict the mechanical behavior of implants of total joint replacements. Accurate prediction can be obtained because of the homogeneity of the solid material. However, for highly porous metallic materials, the mechanical behavior is not predicted accurately since the structure at the mesoscale is made of slender struts and voids. The nominal dimensions at the mesoscale are of the order of hundreds of microns. As an example for an implant, strut diameters are approximately 500 microns and pores 800 microns. The discrepancy between nominal and actual (manufactured) dimensions becomes important for highly porous materials. As a result, the mechanical behavior predicted with finite element models differ importantly from experimental data. Finite element analysis is essential to study the overall (at the macroscale) and local (at the mesoscale) mechanical behavior of porous materials to design implants, before mechanical testing and pre-clinical testing. This research program will develop numerical tools to predict the porous metallic materials using experiments to validate the numerical model.******

随着患者变得更加年轻和活跃，骨科植入物的长期生存仍然是一个挑战。影响植入物寿命的一个因素是骨吸收，据信是由于应力屏蔽造成的。骨骼是一种活组织，对机械刺激有反应。当骨头被取出，被人工植入物取代时，骨骼内的应力发生了重新分布。这种应力遮挡现象的发生是因为金属种植体和周围骨之间的硬度差异很大。因此，骨被应力遮挡，因此骨被吸收，其密度降低，最终导致关节置换失败。需要新的材料来模仿天然骨骼以减少应力遮挡现象。*如今，添加剂制造技术使复杂的、可控的多孔材料成为可能，例如具有高孔隙率(50-80%)的金属，其材料特性可根据需要量身定做。这种新材料可以用来设计降低硬度的植入物，以减少应力遮挡。此外，它们允许在孔洞内良好的骨整合(细胞通过种植体生长以获得适当的稳定性)。可以在介观尺度上制造无限大的结构，从而可以设计出无穷无尽的力学性能。植入物可以通过具有高孔隙率的区域和具有较少孔隙率或没有孔隙率的其他区域来进行功能分级。最后，可以制造适合每个患者的定制植入物。*这项研究计划的目的是设计和模拟使用添加剂制造技术获得的用于整形外科应用的新型多孔金属材料。数值模拟被广泛用于预测全关节置换植入物的力学行为。由于固体材料的均质性，可以得到准确的预测。然而，对于高孔隙率的金属材料，由于细观结构是由细长的支柱和空洞组成的，其力学行为并不能准确预测。介观尺度上的标称尺寸为数百微米量级。以植入物为例，支柱直径约为500微米，孔洞约为800微米。标称尺寸和实际(制造)尺寸之间的差异对于高渗透性材料来说变得很重要。因此，用有限元模型预测的力学行为与实验数据有很大不同。在机械测试和临床前测试之前，有限元分析对于研究多孔材料的整体(宏观)和局部(中观)力学行为以设计植入物是必不可少的。这项研究计划将开发数值工具来预测多孔金属材料，使用实验来验证数值模型。