Manufacturing conditioned roughness and wear of biomedical oxide ceramics for all-ceramic knee implants

Abstract

BackgroundCeramic materials are used in a growing proportion of hip joint prostheses due to their wear resistance and biocompatibility properties. However, ceramics have not been applied successfully in total knee joint endoprostheses to date. One reason for this is that with strict surface quality requirements, there are significant challenges with regard to machining. High-toughness bioceramics can only be machined by grinding and polishing processes. The aim of this study was to develop an automated process chain for the manufacturing of an all-ceramic knee implant.MethodsA five-axis machining process was developed for all-ceramic implant components. These components were used in an investigation of the influence of surface conformity on wear behavior under simplified knee joint motion.ResultsThe implant components showed considerably reduced wear compared to conventional material combinations. Contact area resulting from a variety of component surface shapes, with a variety of levels of surface conformity, greatly influenced wear rate.ConclusionsIt is possible to realize an all-ceramic knee endoprosthesis device, with a precise and affordable manufacturing process. The shape accuracy of the component surfaces, as specified by the design and achieved during the manufacturing process, has a substantial influence on the wear behavior of the prosthesis. This result, if corroborated by results with a greater sample size, is likely to influence the design parameters of such devices.

State of the art of bioimplants manufacturing: part I

“…Generally, the milled conventional orthopaedics joints are subjected to a serious of grinding processes by machines with three or more axes [114]. Polishing is employed as the last step to achieve desired smooth surfaces, where the manual process is often involved [115,116].…”

“…Therefore, precise grinding and polishing processes must be applied to ensure the material removal mode maintains in the ductile region. It is reported that there are about 60 individual machining steps required for even the relatively simple geometry of a ceramic hip replacement [114]. In contrast to hip implant components, the artificial knee joint has more complex and partly freeform surfaces, which raises the difficulty of manufacturing.…”

“…One typical example is presented by Turger et al [114]. In their work, means of calculation and modelling works were applied to predict the surface quality after pre-grinding.…”

State of the art of bioimplants manufacturing: part II

“…It should be noted that this technology is a simplified model of normal walking, and simulation of the motion and loading in activity is very limited. In fact, there are three complicated articulation mechanisms that are involved in the motion of a tibiofemoral joint, namely gliding, pure rolling and rolling-slipping [129]. Investigations are required to elucidate the complex environment of the host body and increased patient activities.…”

Assessment of non-contacting optical methods to measure wear and surface roughness in ceramic total disc replacements

“…They can measure both form and surface roughness in one scan with a vertical resolution of approximately 1 nm and a resolution across the contacting surfaces of approximately 1 µm. Non-contacting optical methods such as white light interferometry 11,17 and laser confocal profilometry 18 have been successfully used to measure the volumetric wear of ceramic hip and knee implants. They also have the advantage over the gravimetric method that the pattern of wear across the implant surface can be seen and areas of severe wear identified.…”