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 o...更多ut 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. 还原