聚内消旋乳酸(PDLLA)椎间融合器在椎间降解情况的实验观察

Degradation of PDLLA cage in the intervertebral fusion

[目的]观察可降解材料在椎间植骨融合中的降解情况。[方法]将可降解材料制成的椎间融合器通过前路手术植入山羊的腰椎间隙,与正常植骨融合组对照,通过大体观察、电镜观察了解不同阶段的可吸收材料在植骨融合过程中的降解吸收情况。[结果]材料在椎间融合过程中的降解速度是非匀速的,在早期阶段,材料主要表现为表面材料的水解,分子量的下降,随着材料各层水解逐渐加快,内部降解速度由于自催化作用而加快,最终材料塌陷,分解。[结论]在早期可保持其基本外形,力学强度虽然在后期明显有所下降,但足够维持骨融合进程,植骨部位骨融合后才逐渐分解,强度下降,最终塌陷崩解。作为椎间融合器的材料,PDLLA在椎间植骨融合中的降解情况基本符合要求。

[ Objective] To observe the degradation process of PDLLA in the intervertebral fusion. [ Method] Twenty goats were divided into 4 groups as experimental group, and their L3 -4 intervertebal spaces were implanted with PDLLA cage containing pieces of graft bone. Animals were sacrificed at 4, 8, 12, 16 wks and specimens were taken for observation of the degradation process and bone fusion by gross observation and electronic microscope. Another 12 goats were used as normal fusion control group. Their L3 -4 space were grafted with bone block for fusion. [ Result] The degradation rate was non-lineal. In the early stage of fusion, the main degradation and decrease of molecular weight was shown at the superficial decomposition. With the proceeding of fusion and degradation, as the kydrolyzation speeding-up, internal decomposition by self-catalyse resulted into the collapse and total disassemble of the PDLLA. The PDLLA cage maintained its shape in the early stage and its biomechanical strength decrease in late stage but was still enough to keep the structure from collapse, till the fusion was achieved in the bone implant area. [ Conclusion ] The velocity of degradation of PDLLA is slower than the speed of bone regeneration of bone fusion, so the PDLLA cage could provide sufficient support during the process of intervertebal fusion and is a suitable choice of degradative material for cage in the intervertebal fusion.