RESEARCH FOR HA/ POLY-L-LACTIDE COMPOSITE AS BIORESORBABLE HIGH-STRENGTH OSTEOSYNTHETIC IMPLANTS

研究了超高强度羟基磷灰石/聚1-乳酸（HA/PLLA）复合材料骨折修复棒在兔皮下和髓腔内的生物降解行为。植入皮下的复合材料的弯曲强度在25周时保持在200 MPa以上，在52周时保持在150 MPa。分子量在第5周下降至初始值的45%，在第52周下降至约10%。扫描电镜显示，随着时间的推移，HA颗粒逐渐从棒表面消失，并且在52周时，这些HA颗粒留下的空间在复合材料表面形成许多孔隙。组织学上，从4周开始，在皮下组织和髓腔骨干区域的复合棒周围形成纤维组织层。在髓腔中，随访期间所有复合棒的亲和指数均显著高于未填充PLLA棒的亲和指数（p < 0.01 ;双因素ANOVA）。在c-HA 40杆中，在4周时达到最大亲和力指数（41%）。复合材料之间亲和指数的唯一显著差异是煅烧的HA 40比未烧结的HA 40具有更高的亲和指数（在4周时p < 0.05）。在实验期间，没有炎症细胞，如单核或多核吞噬细胞。虽然需要进一步的长期降解研究，但该复合材料具有良好的机械强度，在实验期间用作骨固定器械时没有不良组织反应。

The biodegradation behavior of the ultra-high-strength hydroxyapatite/poly(1-lactide) (HA/PLLA) composite rods for fracture repair was investigated both in subcutis and medullary cavity in rabbits. The bending strength of the composites implanted in the subcutis was maintained at more than 200 MPa at 25 weeks and at 150 MPa at 52 weeks. The molecular weight dropped to 45% of the initial values at S weeks and to approximately 10% at 52 weeks. SEM demonstrated that HA particles disappeared increasingly from the rod surfaces over time and that the spaces left by these HA particles formed many pores in the composite surfaces at 52 weeks. Histologically, a fibrous tissue layer was formed around the composite rod from 4 weeks in the subcutis and in the diaphyseal area of the medullary canal. In the medullary cavity, the affinity indices of all composite rods were significantly higher than those of unfilled PLLA rods during follow-up, (p < 0.01 ; two-way ANOVA). The maximum affinity index (4 1%) was attained at 4 weeks in c-HA40 rods. The only significant difference in affinity indices among the composites was that calcined HA40 had a higher affinity index than unsintered HA40 (p < 0.05 at 4 weeks). During the experimental period, there were no inflammatory cells such as mono- or multi-nuclear phagocytes. Although further long-term studies for degradation are needed, the composites have promising mechanical strength and no adverse tissue reaction for use as fracture-fixation devices during the experimental periods.