体内環境下における最先端人工関節材料のビーリングスの分光学的・力学的評価

该研究项目进一步深入了解了各种陶瓷生物材料在体外和体内骨科假体植入物中的耐久性。模拟磨损测试和回收材料分析清楚地表明，与传统的实验室模拟相比，大多数常用的陶瓷生物材料（单片氧化铝、氧化锆和氧化锆增韧氧化铝）在体内降解的速度要快得多。研究还表明，金属染色引起的种植体脱位，导致更快的降解。润滑的存在限制了摩擦接触的严重程度，降低了摩擦系数，但可能促进四边形氧化锆转变为单斜晶，降低了植入物的力学性能。生物惰性生物材料的概念因此受到质疑：即使从化学角度来看极其稳定的氧化物，也会与人体环境产生明显而意想不到的相互作用。考虑到这些结果，氮化硅已被引入作为一种替代生物材料。体外研究清楚地表明，Si3N4与人体环境积极相互作用，因此可以成功地用于不同的应用，从促进骨骼生长和骨整合（例如，脊柱植入物或骨填充物）到耐磨（例如，用于髋关节植入物的股骨头）。在骨科中使用的其他传统陶瓷材料中，从未观察到Si3N4赋予的额外抗菌效果。

This research project provided a further insight on the durability of various ceramic biomaterials applied in orthopaedic prosthetic implants both in-vitro and in-vivo. Simulated wear testing and retrieved materials analysis clearly showed that most commonly applied ceramic biomaterials (monolithic alumina, zirconia and zirconia toughened alumina) degrade in-vivo at a rhythm which is significantly higher when compared to conventional laboratory simulations. It was also shown that metal staining caused by dislocation of the implant, leads to an even faster degradation. The presence of lubrication limits the severity of the tribological contact reducing the friction coefficient but might promote the transformation of tetragonal zirconia into monoclinic, reducing the mechanical properties of the implant. The concept of bioinert biomaterials has then been questioned: even oxides, which are extremely stable from a chemical point of view, have a clear and unexpected interaction with the human body environment. Taking into account these results, silicon nitride has been introduced as an alternative biomaterial. Studies conducted in-vitro clearly showed that Si3N4 positively interact with the human body environment and can thus be successfully used for different applications, from promotion of bone growth and osteointegration (e.g.: in spinal implants or bone fillers) to wear resistance (e.g.: in femoral heads for hip implants). The additional anti-bacterial effect granted by Si3N4 has never been observed before for other conventional ceramic material used in orthopaedics.