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

这项研究为各种陶瓷生物材料在体内和体外应用于骨科假体的耐久性提供了进一步的见解。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，最常用的陶瓷生物材料(单块氧化铝、氧化锆和氧化锆增韧氧化铝)在体内的降解节奏明显加快。研究还表明，种植体脱位引起的金属染色，会导致更快的降解。润滑剂的存在限制了摩擦学接触的严重程度，降低了摩擦系数，但可能会促进四方氧化锆向单斜相转变，从而降低种植体的力学性能。生物惰性生物材料的概念随后受到质疑：即使是从化学角度来看极其稳定的氧化物，也会与人体环境发生明显和意想不到的相互作用。考虑到这些结果，氮化硅作为一种替代生物材料被引入。体外研究清楚地表明，Si3N4与人体环境有积极的相互作用，因此可以成功地用于不同的应用，从促进骨生长和骨整合(例如：在脊柱植入物或骨填充物中)到耐磨性(例如：在股骨头中用于髋关节植入物)。在骨科使用的其他传统陶瓷材料中，Si3N4赋予的额外抗菌效果是以前从未观察到的。

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.