Computational Mechanics and Materials Lab, Department of Mechanical Engineering, Ostbayerische Technische Hochschule (OTH) Regensburg, Regensburg, Germany; Technology Campus Neustadt a. d. Donau, Department of Mechanical Engineering, OTH Regensburg, Regensburg, Germany.
Department of Mechanical Engineering, University of Utah, Salt Lake City, UT, USA.
J Mech Behav Biomed Mater. 2022 Jan;125:104878. doi: 10.1016/j.jmbbm.2021.104878. Epub 2021 Oct 8.
Customized additively manufactured (laser powder bed fused (L-PBF)) stents could improve the treatment of complex lesions by enhancing stent-artery conformity. However, geometric irregularities inherent for L-PBF stents are expected to influence not only their mechanical behavior but also their interaction with the artery. In this study, the influence of geometrical irregularities on stent-artery interaction is evaluated within a numerical framework. Thus, computed arterial stresses induced by a reconstructed L-PBF stent model are compared to those induced by the intended stent model (also representing a stent geometry obtained from conventional manufacturing processes) and a modified CAD stent model that accounts for the increased strut thickness inherent for L-PBF stents. It was found that, similar to conventionally manufactured stents, arterial stresses are initially related to the basic stent design/topology, with the highest stresses occurring at the indentations of the stent struts. Compared to the stent CAD model, the L-PBF stent induces distinctly higher and more maximum volume stresses within the plaque and the arterial wall. In return, the modified CAD model overestimates the arterial stresses induced by the L-PBF stent due to its homogeneously increased strut thickness and thus its homogeneously increased geometric stiffness compared with the L-PBF stent. Therefore, the L-PBF-induced geometric irregularities must be explicitly considered when evaluating the L-PBF stent-induced stresses because the intended stent CAD model underestimates the arterial stresses, whereas the modified CAD model overestimates them. The arterial stresses induced by the L-PBF stent were still within the range of values reported for conventional stents in literature, suggesting that the use of L-PBF stents is conceivable in principle. However, because geometric irregularities, such as protruding features from the stent surface, could potentially damage the artery or lead to premature stent failure, further improvement of L-PBF stents is essential.
定制的增材制造（激光粉末床融合（L-PBF））支架可以通过增强支架-动脉的一致性来改善复杂病变的治疗效果。然而，L-PBF 支架固有的几何不规则性预计不仅会影响其机械性能，还会影响其与动脉的相互作用。在这项研究中，在数值框架内评估了几何不规则性对支架-动脉相互作用的影响。因此，比较了重建的 L-PBF 支架模型引起的计算动脉应力与预期支架模型（也代表了通过传统制造工艺获得的支架几何形状）和考虑 L-PBF 支架固有增加的支柱厚度的修改后的 CAD 支架模型引起的动脉应力。结果发现，与传统制造的支架类似，动脉应力最初与基本支架设计/拓扑结构有关，支架支柱的凹陷处出现最高的应力。与支架 CAD 模型相比，L-PBF 支架在斑块和动脉壁内引起明显更高和最大体积的应力。相反，由于其均匀增加的支柱厚度及其与 L-PBF 支架相比均匀增加的几何刚度，修改后的 CAD 模型高估了 L-PBF 支架引起的动脉应力。因此，在评估 L-PBF 支架引起的应力时，必须明确考虑 L-PBF 引起的几何不规则性，因为预期的支架 CAD 模型低估了动脉应力，而修改后的 CAD 模型则高估了它们。L-PBF 支架引起的动脉应力仍在文献中报道的传统支架的范围内，这表明 L-PBF 支架的使用在原则上是可行的。然而，由于几何不规则性，例如支架表面的突出特征，可能会对动脉造成潜在的损害或导致支架过早失效，因此必须进一步改进 L-PBF 支架。
