Reduction of the fracture risk of modular taper interfaces in orthopedic implants by enhancing their resistance towards fatigue and fretting-corrosion by the application of targeted surface modifications

从临床角度来看，髋关节翻修植入物的组配式界面发生骨折的风险增加，这可能导致患者的后续手术费用高昂。该项目的目的是提高这些模块化接口的耐用性，并显着降低骨折的风险。这将通过组配式锥体界面处的目标表面改性来实现。机械加工工艺的目的是减少界面的敏感性，材料疲劳下的组合机械腐蚀负荷。因此，焦点在于近表面中残余应力（RS）的有针对性的诱导，因为已知残余应力对金属材料的疲劳特性具有很大影响。在联合项目中，将使用不同的机械表面处理工艺（深滚、喷丸、车削）来修改外锥表面，从而产生不同的残余应力深度分布和不同的表面粗糙度。除了优化界面，更好地了解机械表面处理对腐蚀环境中疲劳行为的影响，因为很少有人知道在负载情况下，包括机械和腐蚀应力的残余应力的影响。系统地研究了连接件残余应力状态、锥体形貌和锥体几何形状等因素对界面耐久性的影响。对于锥体界面的所有变化，将在生理学框架中表征动态-机械载荷组合下的摩擦疲劳行为。此外，在动态加载过程中的RS的稳定性进行了分析，以评估RS的有效性的疲劳试验的过程中。随后，将腐蚀载荷添加到载荷方案中，以评估锥体界面的失效是疲劳驱动还是腐蚀驱动。最后，在恒定载荷水平下进行长期动态试验，以评估机械和微动腐蚀载荷联合作用下不同表面改性的效果。在该项目中获得的知识将使种植体制造商能够解决迄今为止尚未解决的摩擦腐蚀磨损问题以及由此导致的种植体断裂风险增加。最终，历史上建立的锥形界面将专门适应现代植入系统的需求。最后，该项目旨在最大限度地减少与材料和设计相关的植入物失效，并显著减轻患者和医疗保健系统的负担。

From a clinical point of view, the modular interfaces of revision hip implants are subject to an increased risk of fracture, which can result in costly follow-up operations for patients. The aim of the project is to improve the durability of these modular interfaces and to significantly reduce the risk of fracture. This is to be realized by means of targeted surface modifications at the modular taper interface. The machining processes aim at reducing the susceptibility of the interface to material fatigue under combined mechanical-corrosive loading. The focus lies thereby on the targeted induction of residual stresses (RS) in the near- surface, because residual stresses are known to have a high impact on the fatigue properties of metallic materials. In the joint project, different mechanical surface treatment processes (deep rolling, shot peening, turning) will be used to modify the outer cone surface, resulting in different residual stress depth distributions and different surface roughness. Aside from optimizing the interface, a better understanding of the effects of mechanical surface treatments on the fatigue behavior in a corrosive environment is sought because little is known about the effect of residual stresses in loading situations which comprise mechanical and corrosive stress. A systematic approach is intended to investigate the influence of the factors residual stress state of the joining partners, cone topography and cone geometry on the durability of the interface. For all variations of the cone interface, the frictional fatigue behavior under combined dynamic-mechanical loading will be characterized in a physiological framework. Furthermore, the stability of the RS during the dynamic loading is analyzed to evaluate the effectiveness of the RS over the course of the fatigue tests. Subsequently, corrosive loading is added to the loading scenario to evaluate whether the failure of the cone interfaces is fatigue-driven or corrosion-driven. Finally, long-term dynamic tests with a constant load level will serve to evaluate the effects of the different surface modifications under combined mechanical and fretting-corrosive loading. The knowledge gained during the project will allow implant manufacturers to address the hitherto unsolved problem of frictional-corrosive wear and the resulting increased risk of implant fracture. Ultimately the historically established taper interfaces will be specifically adapted to the demands of modern implant systems. Finally, the project aims on minimizing material- and design-related implant failures and on a significant reduction of the burden on patients and the healthcare system.