结构差异对记忆合金可扩张椎体支架生物力学的影响

目的 观察记忆合金管研制的可扩张椎体支架不同尾端结构对支架的生物力学的影响,为支架工艺参数定型。方法 选用外径4.5 mm、壁厚1.0 mm记忆合金管研制单弧形6瓣支架9枚,其中尾端“十字槽”结构5枚、内螺纹结构4枚,对支架单瓣与双瓣的生物力学分别予以测试,观察支架的体外生物力学状态;本次研制的9枚支架均在衡仪生物力学测试仪上完成,记录压力—位移曲线,压缩位移设定为5 mm,对末端力学测试结果进行对比,并对其压缩位移测试曲线分析。结果 记忆合金管研制的单弧支架测试的压力位移结果为一拱形曲线。在支架5 mm压缩位移时对外扩张力单瓣与双瓣支撑状态总体上无明显统计学差异;尾端“十字槽”结构对支架的力学强度有所影响;内螺纹结构力学强度相对稳定,在5 mm压缩位移时,内螺纹结构的不同瓣叶支撑终板的应力,单瓣为（94.27±4.81）N,双瓣为（107.43±3.40）N,差异有统计学意义（P＜0.05）;末段1.6 mm的观测点,“十字槽”支架应力测试结果显示曲线有所散乱,而内螺纹支架力量均为75 N左右,且均呈稳定的线性曲率变化,具有较好的“末段应力”。结论 支架尾端“十字槽”结构对支架的力学稳定性产生影响;尾端内螺纹支架具有更好的力学性能稳定性;同时,内螺纹结构的椎体支架具有更好的衔接功能和操作的安全性;本研究结果有助于支架工艺的定型。

Effect of structural differences on biomechanics of memory alloy expandable vertebral stents

Objective To observe the effect of different tail structures on biomechanics of expandable vertebral stents developed by memory alloy tubes and to finalize the technological parameters of stents.Methods A memory alloy tube with an outer diameter of 4.5 mm and a wall thickness of 1.0 mm was used to develop 9 single-arc-frames stents. There were 5 stents with grooves and 4 stents in internal thread. The biomechanics of single-frame and double-frame stents were tested respectively to observe the biomechanics status in vitro. The 9 stents were developed in this study were all completed on the biomechanical tester of the weighing instrument. Pressure-displacement curves were recorded and the compression displacement was set at 5 mm. The end mechanical test results were compared and analyzed.Results The pressure displacement of single arc skeleton made of memory alloy tube was each frame with arch curve. There was no statistically significant difference between single and double frame supporting state of external expansion tension when the frame was compressed with 5 mm displacement. The "cross groove" structure at the end had an effect on the mechanical strength of the frame. The mechanical strength of internal thread structure was relatively stable. When the displacement was 5 mm, the stress of different frames supporting the endplate of internal thread structure was (94.27±4.81) N for single-frame and (107.43±3.40) N for double-frames, and the difference was statistically significant (P<0.05). At the observation point of 1.6 mm from the end, the stress test results of the "cross groove" supporting showed that the curve was scattered. While the strength of the inner thread stent was about 75 N and showed stable linear curvature changing with a good "End-supporting".Conclusion The "cross groove" structure at the end of the stent had an effect on the mechanical stability of the stent. The inner thread stent had better mechanical properties and stability. And, the internal thread structure of the vertebral stent had better cohesion function and operation safety. The results of this study were helpful to finalize the stent process.