College of Metallurgy Engineering, Xi'an University of Architecture and Technology, Xi'an, China.
School of Engineering, University of Leicester, Leicester LE1 7RH, UK.
J Mech Behav Biomed Mater. 2020 Dec;112:104022. doi: 10.1016/j.jmbbm.2020.104022. Epub 2020 Aug 6.
Finite element analysis is a powerful tool for the design of bioresorbable medical implants made of aliphatic polyesters such as bioresorbable vascular scaffolds. However polymer erosion has been traditionally modelled using empirical rules rather than differential equations. The rule-based models are difficult to implement in a finite element analysis. Consequently, these models have been limited to simple geometries such as plates or spheres. This paper presents a set of differential equations that govern the hydrolytic chain scission and bulk erosion of bioresorbable implants where polymer erosion is modelled using a differential equation instead of empirical rules. These differential equations can be conveniently solved using a commercial finite element package to calculate the molecular weight and mass loss as functions of time for bioresorbable implant made of aliphatic polyesters. A case study of Absorb bioresorbable vascular scaffolds (BVSs) is presented using data obtained from the literature, where 98 Absorb BVSs were implanted in 40 porcine coronary arteries. It is demonstrated that the finite element model can fit the data of both molecular weight and mass loss as functions of time to an accuracy of approximately 5%. The finite element model and the back-calculated model parameters can be used to design future implants that degrade in a controlled pattern with required mechanical performance.
有限元分析是设计生物可吸收聚酯（如可吸收血管支架）医学植入物的有力工具。然而，聚合物侵蚀传统上是使用经验规则而不是微分方程来建模的。基于规则的模型很难在有限元分析中实现。因此，这些模型仅限于简单的几何形状，如板或球。本文提出了一组微分方程，用于控制生物可吸收植入物的水解链式断裂和整体侵蚀，其中聚合物侵蚀是使用微分方程而不是经验规则来建模的。这些微分方程可以方便地使用商业有限元软件包来计算生物可吸收聚合物的分子量和质量损失随时间的函数。本文使用文献中获得的数据，对 Absorb 生物可吸收血管支架（BVS）进行了案例研究，其中 40 个猪冠状动脉中植入了 98 个 Absorb BVS。结果表明，有限元模型可以将分子量和质量损失随时间的函数数据拟合到大约 5%的精度。有限元模型和反向计算的模型参数可用于设计未来的植入物，使其以所需的机械性能降解。
