Application of High Strength Polylactide Implants for Osteosynthesis

为了克服金属器械用于骨折修复的缺点，使用拉伸技术制造超高强度聚（L-丙交酯）（PLLA）棒。直径为3.2 mm、拉伸比为2.5：1的棒显示出初始弯曲强度和模量值分别为240 MPa和13 GPa，这是降解详细研究中使用的非增强聚（L-丙交酯）棒报告的最高值。棒直径越大，在37 ℃磷酸盐缓冲盐水中保持的弯曲强度越长。植入兔皮下的棒的抗弯强度保持率与体外研究中的棒的抗弯强度保持率几乎相等，而植入兔股骨髓腔的棒的抗弯强度保持率略低。植入后52周，髓腔内PLLA棒的重量减少了22%，78周时减少了70%。组织学检查，52周髓腔内未见异物或炎症反应。植入后52周观察到组织细胞的吞噬作用，并在植入后2至2.5年达到最高水平。另一项关于PLLA螺钉修复兔骨折的研究显示，PLLA组和不锈钢组的碎片无显著差异，PLLA组的新骨更丰富。这些结果表明，拔出的PLLA螺钉和棒可用于修复骨折的人骨。

To overcome the drawback of the metallic device for fracture repair, ultra-high-strength poly(L-lactide)(PLLA) rods were fabricated using a drawing technique. Rods with a diameter of 3.2 mm and a draw ratio of 2.5 : 1 showed initial bending strength and modulus values of 240 MPa and 13 GPa, respectively, which is the highest reported for nonreinforced poly(L-lactide) rods used in detailed investigations of degradation. The greater the rod diameter, the longer the bending strength was maintained in phosphate buffered saline at 37ﾟC. The bending strength retention of rods implanted in the subcutis of rabbits was almost equal to that of rods in the in vitro study, while those rods implanted in the medullary cavity of rabbit femora showed a slightly lower bending strength retention. The weight of PLLA rods in the medullary cavity was reduced by 22% at 52 weeks and by 70% at 78 weeks after implantation. Histologically, no foreign body or inflammatory reaction was observed in the medullary cavity for 52 weeks. Phagocytosis by histiocyte was observed after 52 weeks and reached to the maximum level at 2 to 2.5 years after implantation. The another study on the PLLA screw in the repair of fractured rabbit bone showed that there was no significant difference of the fragments in the PLLA and stainless steel group and new bone was more abundantly detected in the PLLA group. These results suggest that the drawn PLLA screws and rods may be useful in the repair of fractured human bones.