Bioresorbable devices made of forged composites of hydroxyapatite (HA) particles and poly-L-lactide (PLLA): Part I. Basic characteristics
Bioresorbable devices made of forged composites of hydroxyapatite (HA) particles and poly-L-lactide (PLLA): Part I. Basic characteristics
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DOI：
10.1016/s0142-9612(98)00241-5
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发表时间：
1999-05-01
期刊：
影响因子：
14
通讯作者：
Okuno, M
中科院分区：
文献类型：
--
作者：
Shikinami, Y;Okuno, M
既没有煅烧也没有烧结的羟基磷灰石 (u-HA) 颗粒（粒径 0.2-20 μm，平均 3.0 μm，Ca/P = 1.69，含有 CO32-）的化合物，均匀分布在聚 L-丙交酯（PLLA，(M) over bar(v)：400 KDa）基质中，含量为 20-50 wt%（含 10%）通过锻造工艺（一种独特的压缩成型）将其增强为复合材料，然后在车床上加工，以生产实用的不透射线的内部骨固定装置，该装置具有在骨愈合过程中保持的高机械强度、总可吸收性和生物活性（例如骨结合能力和骨传导性）。从各种机械性能的测量结果可以证实，该复合材料通常在迄今为止已知的此类增强生物陶瓷纤维或颗粒/可生物再吸收聚合物复合材料中表现出最高的机械强度。弯曲强度（S-b）约为270 MPa，远远高于皮质骨，模量（E-b）为12 GPa，几乎与皮质骨相当。特别是，冲击强度(S-i)极高，约为聚碳酸酯的值(166KJ/m(2))的两倍。通过将样品浸入磷酸盐缓冲溶液 (PBS) 中，还检查了 S-b、(M) over bar(v)（粘均分子量）、(M) over bar(w)/(M) over bar(v)（分子量分布）和结晶度的体外变化以及它们之间的关系。在具有高 u-HA 含量 (30-50 wt%) 的复合材料中，可以发现初始 (M) 相对于 bar(v) 的立即下降，尽管在仅 PLLA 或具有低 u-HA 含量 (20 wt%) 的复合材料中，初始 A (M) 相对于 bar(v) 几乎没有变化的降解时滞阶段很明显。 Sb 随 (M) 超过棒 (v) 的相应递减曲线变化，并在长达 24 周内保持超过 200 MPa，这是完全骨愈合所需的时间，因此复合材料满足初始机械强度，同时保持内骨固定装置所需的时间。这些结果支持这样的观点，即降解过程存在差异，单独的 PLLA 需要一段时间才能实现水解到内侧的可能性，而具有高 u-HA 含量 (30-50 wt%) 的复合材料立即充满水到内侧并均匀水解。通过能量色散 X 射线 (EDX) 评估，3-6 天后，许多羟基磷灰石晶体在表面沉积和生长，并在模拟体液 (SBF) 中浸泡 7 天后，在表面上覆盖了相当厚的一层。这表明不透射线复合材料具有与骨骼粘合的能力。由于该复合材料致密、具有超高强度，且加工性能优异，可通过机械加工生产多种用于骨科、口腔颌面、颅面、整形外科等精细、精密的螺钉、钉、板等骨内固定器械。在体内研究期间进行适应性评估后，这些设备具有临床应用的潜在应用。 (C) 1999 Elsevier Science Ltd. 保留所有权利。
Compounds that had neither calcined nor sintered hydroxyapatite (u-HA) particles (particulate size 0.2-20 mu m, averaging 3.0 mu m, Ca/P = 1.69, and containing CO32-) uniformly distributed in a poly-L-Iactide (PLLA, (M) over bar(v): 400 KDa) matrix with a content of 20-50 wt% (with 10% increment) were reinforced into composites by a forging process, which was a unique compression molding, and were then machined on a lathe in order to produce practical radiopaque internal bone fixation devices having high mechanical strength which was maintained during bony union, total resorbability and bioactivity such as bone bonding capability and osteoconductivity. From the results of measurement of various mechanical properties, it was confirmed that the composites generally showed the highest mechanical strength among this type of reinforced bioceramic fibers or particles/bioresorbable polymer composite known to date. The bending strength (S-b) of about 270 MPa was a far higher value than that for cortical bone, and the modulus (E-b) of 12 GPa was almost equivalent to that for cortical bone. In particular, the impact strength (S-i) was extremely high at about two times the value (166 KJ/m(2)) of polycarbonate. The in vitro change in S-b, (M) over bar(v) (viscosity average molecular weight), (M) over bar(w)/(M) over bar(v) (molecular weight distribution) and crystallinity, and their relationship with each other was also examined by immersing samples in a phosphate buffer solution (PBS). An immediate decrease in the initial (M) over bar(v) could be found in composites with high u-HA contents (30-50 wt%), although a time-lag stage for degradation where the initial A (M) over bar(v) hardly changes was apparent in cases of PLLA-only or in a composite with a low u-HA content (20 wt%). The Sb changed with corresponding decremental curves for the (M) over bar(v), and retained over 200 MPa for up to 24 weeks, the period of time necessary for full bony union, so that the composites satisfied initial mechanical strengths while maintaining them for as long as necessary for internal bone fixation devices. These results supported the idea that then is a difference in the degradation process such that PLLA alone required a period of time to achieve the possibility of hydrolysis into the inner side, whereas composites with high u-HA contents (30-50 wt%) immediately filled with water through to the inner side and were hydrolyzed homogeneously. Many hydroxyapatite crystals deposited and grew on the surface after 3-6 d and generously covered the surface with a fairly thick layer after 7 d of post-immersion in simulated body fluid (SBF) as evaluated by means of energy dispersive X-ray (EDX). This suggested the ability of the radiopaque composites to bond to bone. Since the composites were dense and had ultra-high strength, and the processability was so excellent, many kinds of fine and accurate screws, pins, plates, and other internal bone fixation devices for orthopedic, oral and maxillofacial, craniofacial, and plastic and reconstructive surgeries could be produced by machining treatment. These devices have potential applications for clinical use following the assessment of adaptation during in vivo studies. (C) 1999 Elsevier Science Ltd. All rights reserved.