LIMITS AND CHALLENGES OF ADDITIVE MANUFACTURING TECHNIQUES IN THE PRODUCTION OF IMPLANTABLE METAL PROSTHESES

Objectives: There is growing interest in the adoption of additive manufacturing (AM) techniques for, but not limited to, patient-specific prostheses. This study aims to critically analyze advantages and limits to their use to produce metal implantable prostheses as compared to conventional manufacturing techniques.Methods: This study was based on a non-systematic analysis of the scientific literature addressing theoretical and practical features of AM techniques for the production of metal implantable prostheses. Information was gathered from subjectively selected relevant peer-reviewed papers found with scientific and general-purpose search motors with pertinent keywords. Information was critically analyzed with respect to geometrical accuracy, mechanical and tribological properties, and functional outcomes of implanted prostheses. Challenges were also discussed in terms of production and quality monitoring that AM is to meet to successfully replace conventional manufacturing techniques.Results: The search yielded a limited number of comprehensive quantitative studies reporting on characterization and short and long-term functional performance of implanted prostheses produced by AM. Metallic prostheses produced by AM exhibit peculiar features as a result of their characteristic manufacturing conditions. The thermal cycles they are subjected to yield microstructures that result in improved mechanical strength but at the expense of ductility and fatigue performance. They often present difficult to eliminate flaws, discontinuities and geometrical errors and frequently require secondary treatments. This often leads to controversial prostheses behavior in severe bodily environments and may hinder the rapid production and implantation of personalized prostheses, the most relevant advantage of additive manufacturing techniques.Conclusions: Metal prostheses produced with traditional manufacturing techniques still feature more robust features and better performance than those produced by AM. The added complexities due to the relatively new technology still need to be thoroughly investigated to properly develop novel device evaluation procedures, likely followed by the reinvention of the overall production practice towards patient-specific prostheses.