Topological design and biomechanical evaluation for 3D printed multi-segment artificial vertebral implants

Highlights: • A novel multi-objective optimization methodology was proposed to design the customized vertebral implants; • Maximum von Mises stresses of optimized implant under various load cases were about 41.5% of that of trussed implant; • The strength and stiffness of optimized implant were about 2 times to the traditional implant under compressive failure; • Optimized implant fabricated by SLM technology has been applied in clinical, with good outcomes in functional reconstruction. Customized spinal implants fabricated by additive manufacturing have been increasingly used clinically to restore the physiological functions. However, the mechanisms and methods about the design for the spinal implants are not clear, especially for the reconstruction of multi-segment vertebral. This study aims to develop a novel multi-objective optimization methodology based on various normal spinal activities, to design the artificial vertebral implant (AVI) with lightweight, high-strength and high-stability. The biomechanical performance for two types of AVI was analyzed and compared under different loading conditions by finite element method. These implants were manufactured via selective laser melting technology and evaluated via compressive testing. Results showed the maximum Mises stress of the optimized implant under various load cases were about 41.5% of that of the trussed implant, and below fatigue strength of 3D printed titanium materials. The optimized implant was about 2 times to trussed implant in term of the maximum compression load and compression stiffness to per unit mass, which indicated the optimized implant can meet the safety requirement. Finally, the optimized implant has been used in clinical practice and good short-term clinical outcomes were achieved. Therefore, the novel developed method provides a favorable guarantee for the design of 3D printed multi-segment artificial vertebral implants.