摘要
目前可降解式固定器所面临最大的难题在于强度的大小及降解时间的维持。为了评估可降解式固定器的降解速率，可建立一套体外强度衰减测试模式，以评估材料的机械强度。然而文献报道的测试流程及方法并不一致。本研究参考国外文献的报道及ＡＳＴＭ相关标准，以二种不同材料制成的可降解骨螺钉为对象，建立一套可降解固定器的体外强度衰减测试模式。 使用恒温水槽，提供回旋摇晃运动，使磷酸盐缓冲液（ＰＢＳ）与骨螺钉表面产生相对流动，ｐＨ值维持在７．４±０．２，温度控制在３７±２℃，在设定的时间点取出骨螺钉进行强度测试。采用剪力及三点弯曲测试，每次测试五根骨螺钉，以得到强度衰减与时间的关系、结果表明，ＰＬＬＡ骨螺钉在第６～７周时强度产生急速衰减，ＰＬＧＡ骨螺钉在第４周强度已几乎消失。 通过本研究建立的体外强度衰减测试模式，可得到可降解骨螺钉机械强度随时间衰减的曲线。此套测试模式的建立可作为研发可降解固定器的体外测试评估及参考依据．
The strength and decay rate of biodegradable fixation device can be monitored and improved by mean of in vitro degradation tests. However, from literature review, it is found that the testing procedure and controlled degradation environment applied in various vitro tests are not the same. Therefore, the purpose of this research is to establish an in vitro degradation system by monitoring the degradation system of mechanical strength of a biodegradable bone screw. Conditions set for In vitro degradation and mechanical tests refer to ASTM F1635 and relevant papers. The sample screws, offered by Industrial Technology Research Institude, are made of two different materials, ie, Poly-L-lactic(PLLA) acid and the copolymer of Poly-L-lactide and Poly-glycolide(PLGA). They were put in several containers and immersed in isotonic PBS(pH=7.4±0.2, 0.15M NaCl). The temperature of buffer solution was maintained at 37±20℃ by a shake bath. Both of the shear and three points bending tests were carries out to monitor the decay of the mechanical strength of the screws. The resulting mechanical strength reported here in is an average of 5 samples. The present results indicate that the strength of PLLA screws decreased significantly among week 6 to week 7 and PLGA screws lost almost all of its strength in about 4 week. The in vitro degradation system developed here in could be applied to help evaluating the performance of a biodegradable screw.
出处
《医用生物力学》
CAS
CSCD
2000年第3期129-134,共6页
Journal of Medical Biomechanics
