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，翻修髋关节植入物的模块化接口容易导致骨折风险增加，这可能会导致患者昂贵的后续手术。该项目的目的是提高这些模块化接口的耐用性，并显著降低骨折的风险。这将通过在模块锥度界面进行有针对性的表面修改来实现。机械加工工艺的目的是降低界面在机械-腐蚀复合载荷作用下对材料疲劳的敏感性。因此，重点在于有针对性地在近表面诱导残余应力(RS)，因为已知残余应力对金属材料的疲劳性能有很大的影响。在联合工程中，将采用不同的机械表面处理工艺(深轧、喷丸、车削)对外锥表面进行改性，导致不同的残余应力深度分布和不同的表面粗糙度。除了优化界面外，还寻求更好地了解机械表面处理对腐蚀环境中疲劳行为的影响，因为对包括机械应力和腐蚀应力在内的加载情况下残余应力的影响知之甚少。用系统的方法研究了连接副残余应力状态、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，动-机械联合载荷下的摩擦疲劳行为将在生理框架下表征。此外，还对RS在动态加载过程中的稳定性进行了分析，以评估RS在疲劳试验过程中的有效性。随后，在加载方案中添加腐蚀性加载，以评估圆锥界面的破坏是疲劳驱动的还是腐蚀驱动的。最后，在恒定载荷水平下的长期动态试验将用于评估在机械和微动-腐蚀联合载荷下不同表面改性的效果。在项目期间获得的知识将使植入物制造商能够解决迄今为止尚未解决的摩擦腐蚀磨损问题，以及由此增加的植入物破裂风险。最终，历史上建立的锥形接口将专门适应现代植入系统的要求。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故障，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.