新型可降解镁合金胆道支架的体外降解规律及力学性能

背景：大量文献表明镁合金可在体内降解，具有优良的机械支撑性能，并且可作为血管支架材料、骨固定材料及多孔骨修复材料，但未见将其应用于胆道支架的报道。目的：评估AZ 31B镁合金胆道支架在体外人胆汁中的降解过程及力学性能变化规律。方法：将AZ31B镁合金激光镂空雕刻成球囊扩张可膨式胆道支架，其中表面经微弧氧化处理的胆道支架、裸胆道支架各15枚，分别为实验组和对照组。体外建立动态数值化模拟系统，模拟人体胆道内环境，将两组支架置于模拟系统内，每20d为一个观察单位，定期观察支架的大体形态、质量及径向支撑力，扫描电镜观察支架表面形态。结果与结论：①实验组较对照组降解速度明显减慢，对照组20d开始出现连杆的断裂，降解高峰在30d左右，70d内完全降解；实验组40d开始出现连杆的断裂，降解高峰在50d左右，90d内完全降解。两组随着降解时间的延长，支架表面变得粗糙，蚀坑的密度增加，蚀坑的面积增大，蚀坑的深度加大。在相同阶段，对照组相对于实验组降解程度明显严重。②实验组与对照组支架的质量及径向支撑力随降解时间的延长逐渐下降，实验组较对照组下降速度明显减慢。表明AZ31B镁合金胆道支架经过表面微弧氧化处理后降解速度适宜，能够达到临床上对胆道支架降解时间的要求。

In vitro biodegradation and mechanical characteristics of a novel biliary stent made of magnesium alloy

BACKGROUND： Numerous evidence has demonstrated that the magnesium aloy with excelent mechanical properties can degradein vivo, and can be used as vascular stent materials, bone fixation materials, porous materials for bone repair. But it is not reported in the biliary stent. OBJECTIVE：To observe the degradation procedures and evaluate the changes of mechanical characteristics of biliary stents made of magnesium aloy （AZ 31B） in human bilein vitro. METHODS：The baloon-expandable biliary stents were made of magnesium aloy with laser sculpture. Then, 15 stents treated with micro-arc oxidation on the surface served as experimental group and another 15 stents without micro-arc oxidation as control group. A dynamic numerical simulation system was establishedin vitro to simulate the internal environment of human biliary tract. Al of the biliary stents were placed into this system. Their shapes were observed, and their qualities and radical forces were measured every 20 days. At the same time, their surfaces were scanned by scanning electron microscope. RESULTS AND CONCLUSION：（1） The degradation speeds of the stents in the experimental group were obviously slower than those in the control group. The fracture of the connecting rods in control group and experimental group appeared 20 days and 40 days later, respectively. The peak time of degradation in the control group and experimental group were 30 days and 50 days, respectively. The stents were fuly biodegraded within 70 days in the control group while within 90 days in the experimental group. With time, the stent surface became more rough, and the density, area and depth of etch pits were al increased in the two groups. At the same stage, the degradation speed of the control group was more rapid than that in the experimental group. （2） The qualities and radical forces of the stents were gradualy reduced with time in both groups. However, the degradation speed of stents in the experimental group was much slower than that in the control group. In summa