Tan Nathanael, van Arkel Richard J
Department of Mechanical Engineering, Imperial College London, London SW7 2AZ, UK.
Materials (Basel). 2021 Nov 25;14(23):7184. doi: 10.3390/ma14237184.
Stiff total hip arthroplasty implants can lead to strain shielding, bone loss and complex revision surgery. The aim of this study was to develop topology optimisation techniques for more compliant hip implant design. The Solid Isotropic Material with Penalisation (SIMP) method was adapted, and two hip stems were designed and additive manufactured: (1) a stem based on a stochastic porous structure, and (2) a selectively hollowed approach. Finite element analyses and experimental measurements were conducted to measure stem stiffness and predict the reduction in stress shielding. The selectively hollowed implant increased peri-implanted femur surface strains by up to 25 percentage points compared to a solid implant without compromising predicted strength. Despite the stark differences in design, the experimentally measured stiffness results were near identical for the two optimised stems, with 39% and 40% reductions in the equivalent stiffness for the porous and selectively hollowed implants, respectively, compared to the solid implant. The selectively hollowed implant's internal structure had a striking resemblance to the trabecular bone structures found in the femur, hinting at intrinsic congruency between nature's design process and topology optimisation. The developed topology optimisation process enables compliant hip implant design for more natural load transfer, reduced strain shielding and improved implant survivorship.
僵硬的全髋关节置换植入物会导致应力遮挡、骨质流失和复杂的翻修手术。本研究的目的是开发拓扑优化技术，以设计出更符合人体的髋关节植入物。采用了带惩罚的固体各向同性材料（SIMP）方法，并设计并通过增材制造制造了两种髋关节柄：（1）基于随机多孔结构的柄，以及（2）选择性掏空方法。进行了有限元分析和实验测量，以测量柄的刚度并预测应力遮挡的降低情况。与实心植入物相比，选择性掏空的植入物使植入周围股骨表面应变增加了高达25个百分点，同时不影响预测强度。尽管设计上存在显著差异，但两种优化后的柄的实验测量刚度结果几乎相同，与实心植入物相比，多孔和选择性掏空植入物的等效刚度分别降低了39%和40%。选择性掏空植入物的内部结构与股骨中的小梁骨结构惊人地相似，这暗示了自然设计过程与拓扑优化之间的内在一致性。所开发的拓扑优化过程能够设计出符合人体的髋关节植入物，实现更自然的载荷传递、减少应力遮挡并提高植入物的存活率。
