1.School of Medical Instrument and Food Engineering,University of Shanghai for Science and Technology;2.China;3.MicroPort Neur TechShanghai Co,Ltd
目的 开口式取栓支架是治疗急性缺血性脑卒中(Acute Ischemic Stroke,AIS)的有效装置,本文从生物力学角度对开口式取栓支架的取栓过程进行仿真分析,为取栓支架的设计以及临床选择提供理论支持。方法 建立支撑单元个数不同(3、4、5)的K3、K4和K5开口式取栓支架、压握工具、模拟血管和模拟血栓(三种类型)的有限元模型。对压握工具的径向施加位移载荷,取栓支架外径压握至0.5mm,分析支架的最大主应变峰值和径向支反力；恢复压握工具的位移,取栓支架自膨胀与血管接触,分析支架的最大主应变和血管的Mises应力；对取栓支架的近端施加轴向位移,让支架带动血栓进行迁移,分析血管的Mises应力和支架的回撤力(捕获血栓的能力)。结果 压握过程中三款取栓支架的最大主应变峰值分别为6.94%、8.30%和5.48%,都小于断裂极限12%；支架外径为3mm时(等于血管内径),K4支架的径向支反力最大；自膨胀释放过程结果表明,取栓支架的支撑单元数越多,对应血管的Mises应力值越大,但均小于血管的极限应力1.44MPa；迁移取栓阶段发现,血管Mises应力值普遍较小且集中在血栓所在部位；在迁移取栓的初始阶段,取栓支架的回撤力达到最大值,后渐渐下降趋于平稳,其中K4支架的回撤力峰值大于K3和K5。结论 虽然三款取栓支架在取栓模拟中的最大主应变以及血管Mises应力均在安全范围内,但K4支架在径向支反力、拉取三种血栓的回撤力方面表现更优。该研究结果可为优化开口式取栓支架提供一种分析方法及思路,来避免血管损伤等临床并发症,提高取栓支架安全性和有效性。
Objective Open-type stent retrievers are effective devices for the acute ischemic stroke (AIS). This article simulated the thrombus removal process of the open-type stent retrievers and the results can be used as the design and clinical application of the open-type stent retrievers. Methods Established finite element models of different supporting cells (3, 4, 5) open-type stent retrievers(K3,K4,K5), crimping tools, simulated vessels and simulated thrombus (three types) .Displacement load was applied on the radial direction of the crimping tool until the stents was crimped to 0.5mm, the maximum principal strain(MPS) peak and the radial force of the stents were analyzed. Restored the displacement of the crimping tool, stents self-expanded and contacted with blood vessel, analyzed the MPS of the stents and the Von Mises stress (VMS) of the blood vessel. Applied axial displacement on the proximal end of the stent retrievers, analyzed the blood vessel VMS and withdrawal force (the clot-capturing ability). Results The MPS peaks of the three stent retrievers during the crimping process were 6.94%, 8.30%, and 5.48%, which were all less than the fracture limit of 12%.When the outer diameter of the stents was 3mm (equal to the inner diameter of the blood vessel), the number K4 stent had the largest radial force. The results of self-expanding release process showed that the larger the number of support cells, the greater the VMS of the blood vessel. And the results were all less than the limit stress 1.44 MPa. During the migration and removal stage, it was found that the VMS of the blood vessel were generally small and concentrated on the thrombus. The withdrawal force of the stents reached the maximum value at first, then gradually decreased. The peak withdrawal force of the K4 stent was biggest of all. Conclusions Although the MPS and VMSthe three open-type stent retrievers were within the safe range, the K4 stent had the advantages on radial force and withdrawal force with the three types of thrombus. The results of this study can provide an analysis method and ideas for optimizing the open-type stent retrievers to avoid clinical complications such as vascular injury and improve the safety and effectiveness of the stent retrievers.