Aerospace Engineering Department, Iowa State University, Ames, IA, 50011, United States.
Veterinary Clinical Sciences, Iowa State University, Ames, IA, 50011, United States.
J Mech Behav Biomed Mater. 2021 Apr;116:104345. doi: 10.1016/j.jmbbm.2021.104345. Epub 2021 Jan 29.
A tunable stiffness bone rod was designed, optimized, and 3D printed to address the shortcomings of existing bone fixation devices, such as stress shielding and bone nonunion in the healing of fractured bones. Current bone plates/rods have constant and high stiffness. High initial stiffness prevents the micromotion of newly formed bone and results in poor bone healing. Our novel design framework provides surgeons with a ready-for-3D-printing, patient-specific design, optimized to have the desired force-displacement response with a stopping mechanism for preventing further deformation under higher-than-normal loads, such as falling. The computational framework is a design optimization based on the multi-objective genetic algorithm (GA) optimization with the FE simulation to quantify the objectives: tuning the varied stiffness while minimizing the maximum von Mises stress of the model to avoid plastic and permanent deformation of the bone rod. The computational framework for optimum design of tunable stiffness metamaterial presented in this paper is not specific for a tibia bone rod, and it can be used for any application where bilinear stiffness is desirable.
设计、优化并 3D 打印了一种可调刚度骨棒，以解决现有骨固定装置的缺点，如在骨折愈合过程中的应力遮挡和骨不连。目前的骨板/棒具有恒定的高刚度。初始高刚度会阻止新形成的骨的微动，导致骨愈合不良。我们的新颖设计框架为外科医生提供了一种可用于 3D 打印的、针对特定患者的设计，经过优化，可在具有停止机制的情况下实现所需的力-位移响应，以防止在高于正常负荷（如跌倒）下进一步变形。计算框架是基于多目标遗传算法（GA）优化和有限元模拟的设计优化，以量化目标：调整变化的刚度，同时最小化模型的最大 von Mises 应力，以避免骨棒的塑性和永久变形。本文提出的可调刚度超材料最优设计的计算框架不仅适用于胫骨骨棒，也可用于任何需要双线性刚度的应用。
