Advancing Bioceramic Science in Orthopaedic Surgery - The Case for Silicon Nitride

整形外科におけるバイオセラミック科学の進歩―窒化ケイ素の場合

2016-09-26

2016-09-26

In order for synthetic materials to be applied toward the manufacture of biomedical implants, their short-term and intermediate-term biocompatibility must be tested. Such testing is accepted as a valid proxy for long-term implant performance in vivo, since practical limitations preclude a comprehensive assessment of the long-term interaction of biomaterials with the human in vivo environment. Ideally, any changes in implant biocompatibility and tissue integration should improve favorably over time in vivo. Yet, the present standard for the selection of biomaterials targets bioinert behavior as a desirable attribute. Thus, for example, ceramic bearings in orthopaedic surgery, specifically in hip and knee replacements, are believed to be superior to metal-polyethylene articulations, in part because ceramics are inert and therefore will remain stable after implantation in the body. The fallacy in this belief is that no material is entirely bioinert; acknowledgement of this fact is a key first step in thinking about the development of future biomedical devices. Bioinert behavior should apply not only to the implant, but also to the wear debris generated by implant articulations, or by micromotion of the implant during cyclic physiologic loads. It is well known, for example, that microscopic and submicroscopic wear particles of polyethylene contribute to osteolysis and attendant failures in hip and knee replacements, and that particulate metallic debris from metal-metal articulations in total hips can lead to adverse local tissue reactions. In this thesis, a new approach based on advanced spectroscopic techniques was used to investigate the performance of several advanced bioceramics used in prosthetic joint implants, and to propose a strategy to enhance their longevity in vivo. In a challenge to conventional notions that bioceramics are inert materials, our experiments have shown the opposite, i.e, that surface chemical and structural changes manifest upon ceramic contact with biological fluids. The resulting changes can be either beneficial or detrimental in terms of the predicted long-term behavior of the material in vivo. In particular, the peculiar properties of silicon nitride, a non-oxide ceramic that is widely used in industrial applications, make it an attractive candidate material for artificial joints and other biomedical devices. In distinct contrast to oxide ceramics such as alumina and zirconia, changes induced in the surface chemistry and mechanical behavior of silicon nitride by the in vivo environment may contribute to improved long-term outcomes.

博士（工学）

京都工芸繊維大学

14303乙第204号

http://hdl.handle.net/10212/2357

eng

ETD

Thesis or Dissertation

Thesis