Precise design, preparation, and biomechanical evaluation of customized additively manufactured Ti6Al4V porous fusion cage

The stress shielding phenomenon and subsidence risk caused by the excessive stiffness of dense Ti6Al4V (Ti64) cages affects their application in lumbar fusion surgeries. Advances in additive manufacturing techniques have facilitated the production of porous Ti64 cages with decreased stiffness for the better biomechanical performance. Precise design and preparation of porous cage were crucial for achieving the optimal performance in the fusion surgery. This study introduced a workflow for precise design, preparation, and biomechanical assessment of porous Ti64 cage with designated mechanical properties. Hierarchical optimization was used to obtain the porous cage with designated mechanical properties, including microscale optimization based on the compression load condition to obtain the basic cellular structure and macroscale optimization to determine the framework layout within the cage to achieve the desired stiffness under simulated physiological loading conditions. Numerical simulations of fusion surgery confirmed that the optimized porous cage reduced the stress shielding phenomenon and the subsidence risk of the cage. Further, the cage was prepared via laser powder bed fusion and post-treated via flowing acid etching method to achieve the designed mechanical properties and topological morphology. The compression experiments confirmed that the porous cage contributed to enhancing subsidence resistance. The proposed workflow can be expanded to the precise design, preparation, and biomechanical assessment of various porous implants.