Adjusting the Subsurface Properties of Biocompatible Magnesium–Calcium Alloys as Absorbable Implant Material by Machining Processes
Traditional methods of osteosynthesis or osteotomy use permanent metal implants e.g. bone screws and bone plates made of steel or titanium alloys, but permanent metal implants have to be excised. Especially young patients in growth require the implant removal. Biodegradable implants, which dissolve in the human organism, therefore represent an appropriate solution. Biocompatible magnesium alloys offer great potential as absorbable implant materials. Providing sufficient mechanical properties they degrade within a certain time span after surgery and are therefore suitable to temporarily accomplish medical functions, for instance as bone screws or plates. These implants support fractured bones until healing. This paper describes approaches to adjust the corrosion of the magnesium and hereby the degradation kinetics of the implant in the organism. The degradation kinetics is adjustable via modifications of surface (e.g. topography) and subsurface properties (e.g. micro hardness, residual stresses) of the implant determined by the manufacturing process. Consequently, a specific degradation profile adapted to requirements of the individual medical application is achievable.
KeywordsResidual Stress Corrosion Rate Corrosion Behavior Compressive Residual Stress Hydrogen Generation
The investigations described in this paper were funded by the German Research Foundation (DFG) within the subproject R4 of the collaborative research center SFB 599 “Sustainable Bioresorbable and Permanent Implants of Metallic and Ceramic Materials”.
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