编织型食管支架挤压刚度的研究

Study on the extrusion stiffness of braided esophageal stent

临床上人体食管腔道并非圆形截面,机体运动和病变组织生长的不确定性而使植入后的支架受到挤压作用,引起支架的局部失稳或难以适应腔道变化,从而引起并发症。利用有限元法对361L不锈钢、WE43镁合金、Ni-Ti合金、聚乳酸PLLA 4种材料编织而成的食道管支架的整体平面挤压刚度和局部挤压刚度进行分析,对比不同材料不同丝径对支架挤压刚度的影响。结果显示,材料弹性模量越高,支架的挤压刚度越大;丝线直径越大,支架的挤压刚度也越大。但是随着挤压变形的增大,挤压刚度有变小的趋势。局部挤压会产生应力集中现象,但在挤压变形为4 mm时,四种不同材料支架的等效应力均小于材料的强度极限,丝线不会发生断裂。支架挤压刚度的了解可为支架优化设计和临床选型提供重要的理论依据。

Due to the non-circular cross section of human esophageal cavity,the body movement and the uncertainty of pathological tissue growth,the implanted stent is squeezed,which causes the stent to be unstable or unable to adapt to the changes of the esophageal cavity,thus leading to complications.The overall plane extrusion stiffness and local extrusion stiffness of the esophageal stent fabricated from four different materials were analyzed by using the finite element method,and the effect of different wire diameters and different materials on the extrusion stiffness of thestent were compared.The results showed that,the higher the elastic modulus of the material was,the greater the extrusion stiffness of the stent would be;the larger the wire diameter was,the greater the extrusion stiffness of the stent would be.However,with the increase of the extrusion deformation,the extrusion stiffness tended to decrease.Local extrusion would produce stress concentration,but when the extrusion deformation was 4 mm,the equivalent stresses of the four stents of different materials were all less than the strength limits of the materials,and the wires of the stents did not break.This study has provided important theoretical reference for the optimization design and the clinical selection of braided stents.