Pistner H, Stallforth H, Gutwald R, Mühling J, Reuther J, Michel C
Klinik und Poliklinik für Mund-, Kiefer- und Gesichtschirurgie der Universität Würzburg, Germany.
Biomaterials. 1994 May;15(6):439-50. doi: 10.1016/0142-9612(94)90223-2.
Three different poly(L-lactide) rods (25 x 3 x 2 mm) were produced either by injection moulding or machined out of a solid as-polymerized polylactide block and were implanted for 1-116 months into the dorsal muscle of rats. After recovery, the polylactide specimens were carefully cleaned, dried, photographed and weighed. Bending strength and Young's modulus of elasticity were determined. The surfaces of the broken rods were examined by scanning electron microscopy. Block polylactide samples initially looked milky. They became friable and broke into white or brownish fragments during the implantation period, whereas total disintegration could not be observed. Electron scanning microscopy revealed a porous surface with crystalline elements persisting for the whole time. Mechanical stability fell from 127 +/- 3 MPa at implantation time to about half after 3 wk (61 +/- 4 MPa) and about a quarter (32 +/- 4 MPa) after 6 wk. Both injection-moulded polyactides (A1 and A2) were clear and transparent initially. After implantation they gradually became whitish, fragmented after about 64 wk and disintegrated 90 wk later into small parts and powder. Electron scanning microscopy at first showed a homogeneous surface. A kind of cortex developed after about 4 wk and deep cracks ran through the rod after 32 wk. Round pores of 1.5-10 microns diameter developed after 1 yr of implantation. Bending strengths were 130 +/- 8 MPa (A1) and 115 +/- 14 MPa (A2); these remained nearly stable over about 12 wk, then declined linearly. Although a higher initial mechanical strength is desirable for use in osteosynthetic devices, mechanical stability of amorphous injection-moulded polylactides over the first 12 wk and total disintegration thereafter approaches the requirements for their use as a material for osteosynthesis.
通过注塑成型或从块状聚乳酸实体材料加工制作出三种不同的聚（L-丙交酯）棒（25×3×2毫米），并将其植入大鼠背部肌肉1至116个月。恢复后，小心清洗、干燥聚乳酸样本，拍照并称重。测定弯曲强度和杨氏弹性模量。通过扫描电子显微镜检查折断棒材的表面。块状聚乳酸样本最初呈乳白色。在植入期间它们变得易碎，断裂成白色或褐色碎片，但未观察到完全分解。电子扫描显微镜显示整个过程中表面都有带有结晶成分的多孔结构。机械稳定性在植入时为127±3兆帕，3周后降至约一半（61±4兆帕），6周后降至约四分之一（32±4兆帕）。两种注塑聚乳酸（A1和A2）最初都是透明的。植入后它们逐渐变白，约64周后破碎，90周后分解成小碎片和粉末。电子扫描显微镜最初显示表面均匀。约4周后形成一种皮层，32周后棒材出现深裂缝。植入1年后出现直径为1.5至10微米的圆形孔隙。弯曲强度分别为130±8兆帕（A1）和115±14兆帕（A2）；这些强度在约12周内基本保持稳定，然后线性下降。尽管用于骨合成装置时需要更高的初始机械强度，但无定形注塑聚乳酸在前12周的机械稳定性以及随后的完全分解情况接近其作为骨合成材料的使用要求。
