3D-printed metamaterial femoral prostheses via scalar field fusion and directional porous structure regulation

This study integrates topology optimization, scalar field fusion (a method to realize smooth transition between solid and porous regions through implicit function interpolation), and directional porous structure control to develop a design method for customized metamaterial femoral prostheses, addressing key problems of conventional prostheses including poor implant compatibility, excessive bone resection, and insufficient long-term stability. We initially completed the personalized design of femoral prostheses using a combination of retrograde and antegrade methods. This was followed by integrating topology optimization with porous structure filling to design the metamaterial. The prostheses were directly manufactured using 3D printing technology, and their performance was thoroughly evaluated. The results showed that the femoral prosthesis experienced the highest stress at 70° knee flexion (half-squat position), with a maximum stress of 1.269 × 4 MPa and a maximum displacement of 2.77 mm. Following topology optimization, although stress concentration and displacement slightly increased, the stress distribution became more uniform, resulting in a weight reduction of approximately 38.19%. Prostheses treated through scalar field fusion and adjustment of the filling direction of the porous structure exhibited metamaterial properties. The 3D-printed femoral prostheses and their matching components maintained high surface quality with no significant warping or deformation. Moreover, the porous structure displayed a well-defined pore configuration and connectivity. The prostheses and their components achieved a close fit, with dimensional accuracy and compatibility that generally met the requirements. After post-processing, the developed prototype serves as a valid proof-of-concept, thus establishing a foundation for the subsequent development and practical application of high-performance personalized biofix femoral prostheses.