关键词: 可降解接骨板, 超微结构

Abstract: Abstract:Objective To study the characters of degradation of poly-L-lactic acid (PLLA) internal fracture-fixing system.Methods The mandible fracture of dogs was fixed with PLLA internal fracture-fixing system.In 1,3,6,12 months after operation , the materials were taken out from dogs, and the changes of ultrastructures of miniplates were observed using the scanning electron microscope after macroscopic observation.Results Under macroscopic observation,the miniplate was elastic,hard and semitransparent,there was no obvious changes on the surface one month later.The surface of PLLA miniplate became rough, soft,cretaceous, opaque and hard to break three months later.But the miniplate became even softer,still opaque and easy to break with some gabs on the surface six months later.The miniplate became into something like cheese,softer and exquisite twelve months later.Observed by scanning electron microscope, the surface of the miniplate was smooth,there was no fissuaring and hole on it before implantation.One month later,the surface became rough.Three months later there were many gabs on it.Six months later,the gabs entered deeply into the materials.Twelve months later the miniplate had degradated and broken completely.And much of micropore could be seen on the cross-section of miniplate.Conclusion PLLA miniplate degrads on the surface at the beginning and then at 6 months after the operation,the material begins to degrade deeply.The decrease of the mechanic strength speed of degradation is moderate,it matches with the speed of fracture healing.It will help to avoid stress shielding and accelerate the speed of fracture healing.

Key words: biodegradable miniplate, ultrastructure