Development of artificial Osteo-chondral composite material

我们研究并比较了天然关节和人工关节的生物力学。关节最重要的功能依赖于良好的润滑和均匀分布的冲击载荷对底层骨骼。在润滑方面，光学测量了关节空间的动态变化，验证了天然关节存在液膜润滑。从液膜润滑方面来看，超高分子量聚乙烯（UHMWPE）的性能不如聚乙烯醇（PVA-H）和关节软骨。通过试样传递的瞬时应力表明，软骨下松质骨起主要作用，UHMWPE比关节软骨和PVA-H具有更高的峰值应力和更短的持续应力时间，表明其阻尼效果更差。从有限元分析结果来看，髓内固定可能无法避免应力屏蔽。在未来的人工关节中，希望尽可能多地保留软骨下松质骨，并用力学性能与关节软骨相似的材料代替受损伤的关节表面。我们将该材料植入狗的膝关节，检测其生物相容性，证实其具有良好的生物相容性。为了将材料牢固地固定在材料上，我们首先将PVA溶液渗透到多孔氧化铝的孔隙中，并通过凝胶化PVA将这两种材料结合起来。我们将这种人工骨软骨复合材料植入兔股骨的髌骨沟。手术后两周，未钙化组织切片的组织学结果显示相当多的新骨长入到氧化铝孔中。虽然仍有一些问题有待解决，但pva - h似乎是一种非常有趣和有前途的材料，符合人工关节软骨的要求。

We investigated and compared biomechanics of natural and artificial joints. The most important functions of the joints rely on excellent lubrication and uniform distribution of impact loads on the underlying bones. As to the lubrication, we measured dynamic changes of the joint space optically and verified the existence of fluid film lubrication in natural joints. From the aspect of fluid film lubri-cation, ultra high molecular weight polythylene(UHMWPE)is not as good a material as polyvinyl alcohol(PVA-H)and articular cartilage. The momentary stress transmitted though the specimens revealed that sub-chondral cancellous bones played the most important role and the UHMWPE had a highter peak stress and ashorter durations of sustained stress than articular cartilage and PVA-H, suggesting a worse dampingeffect. From the results of finite element method (FEM) analysis, intramedullary stem fixation mightnot avoid stress shielding. In artificial joints in the future, it is desirable to preserve as muchsubchondral cancellous bone as possible and to replace the involved joint surface with materials whose mechanical properties are similar to those of articular cartilage. We examined biocompatibility of this material by implanting them into dog's knee joints and confirmed good biocompatibility. In order to fix the materials firmly to the been, we first infiltrate a PVA solution into the pores of porus alumina and bind these two materials by gelling the PVA. We implated this artificial osteochondral composite material into the patellar groove of a rabbit femur. The histological findings of the undecalcified tissue sections revealed considerable new bone ingrowth into the pores of alumina, just two weeks after the operation. Although some problems still remain to be solved, PVA-Hseems to be a very interesting and promising material which meets the requirements of artificial articular cartilage.