羟基磷灰石/聚DL-乳酸复合材料在不同植入部位降解机制研究

STUDY OF BIODEGRADATION OF HYDROXYAPATITE/POLY(D-LACTIDE) COMPOSITES AT DIFFERENT SITES

将同一规格的自制可吸收羟基磷灰石 /聚DL 乳酸复合骨折内固定材料置于缓冲液、肌肉和骨组织中 ,进行扫描电镜和组织学观察 ,评价材料在不同植入部位的降解过程及细胞反应。结果 :材料在体外降解最慢 ,肌肉内居中 ,骨内最快 ,骨组织内细胞反应更严重。早期材料表层与内层降解速度不一致 ,出现分层现象 ,这种现象在三种环境下均可出现 ,只是形态改变程度不一。最后 ,体外降解时形成空心壳状结构 ;骨内植入时大量降解物不能及时清除 ,在壳外堆积 ,迫使壳层塌陷内移 ,自催化作用更强 ;肌肉内植入时后期残留降解慢的高结晶度颗粒。结论 :材料在不同植入部位降解速度和降解机制不同。

In order to investigate biodegradation and tissue reaction of self designed absorbable hydroxyapatite/poly(DL Lactide) (HA/PDLLA) fracture fixation devices at different sites, HA/PDLLA rods were immersed in phosphate buffered saline, or implanted in muscle or bony tissue for 52 weeks. Scanning electron microscopic and histologic studies were done. Results: The degradation were lowest in saline, lower in muscle tissue and fast in bone tissue. At the early stage of degradation, the composites degraded heterogeneously, the degradation at the deeper layer being faster than at the surface where a layer of less degraded crust was formed. This crust was observed both in vitro and in vivo. Finaly, a hollow structure was formed in vitro. Intraosseously, significant amount of soluble oligomeric residues accumulated outside the crust and the hollow structure was not formed. The limited clearing capacity lead to the accumulation of oligomeric debris, which contribute totally to the autocatalytic effect. So, the fastest degradation and intense tissue response were seen. In musde tissue, howerer, remnants of less degraded high crystalline particles were found. Consequently, the degradation rate and mechanism were different of the same size HA/PDLLA composites at different sites, together with severity of complications.