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A Computational Method for the Design of an Additively Manufactured Personalized Artificial Spinal Disc With Physiological Stiffness Under Multiple Loading Conditions

The main limitations of currently available artificial spinal discs are geometric unfit and unnatural motion. Multi-material additive manufacturing (AM) offers a potential solution for the fabrication of personalized free-form implants with a better fit and variable material distribution to achieve a set of target physiological stiffnesses. The structure of the artificial spinal disc proposed in this paper is inspired from a natural disc and includes both a matrix and a crisscross fiber-like structure, where the design variables are their material properties. After carrying out design variable reduction using linking strategies, a finite element-based optimization is then conducted to calculate the optimized material distribution to achieve physiological stiffness under five loading cases. The results show a good match in stiffness of the multi-material disc compared with the natural disc and that the multi-material artificial disc outperforms a current known solution, the ball-and-socket disc. Moreover, the potential of achieving an improved match in stiffness with a larger range of available 3D printable materials is demonstrated. Although the direct surgical implantation of the design is hindered currently by the biocompatibility of the 3D printed materials, a potential improvement of the design proposed is shown.