Patient-Specific Topology-Optimized TPMS Lattice Ankle Implants for Additive Manufacturing Using Integrated Finite Element Analysis

Additive manufacturing (AM) has revolutionized the development of patient-specific biomedical implants (SPI) by enabling the fabrication of complex geometries with superior dimensional accuracy and functional performance. In orthopedic applications, lattice-based implants offer significant advantages by reducing implant weight, stiffness, and stress shielding, while promoting osseointegration and mechanical compatibility with surrounding bone tissue. This study presents an integrated design framework for a lightweight patient-specific ankle implant based on Triply Periodic Minimal Surface (TPMS) lattice structures and stress-driven topology optimization. Several TPMS topologies, including Gyroid, Diamond, and Voronoi porous structures, are investigated to achieve an optimal balance between mechanical strength, permeability, and material efficiency. A patient-specific ankle model reconstructed from computed tomography (CT) data is processed to generate a high-quality geometric model for finite element analysis (FEA). The stress distribution obtained from the solid bone model is subsequently used to generate a functionally graded TPMS lattice by varying the lattice wall thickness according to local loading conditions. Three implant configurations, namely, solid, uniform TPMS lattice, and functionally graded TPMS lattice implant, are designed and evaluated using the native simulation environment of nTop. The proposed integrated design approach combines FEA, TPMS lattice engineering, and stress-based functional grading optimized designs to enhance the mechanical efficiency of SPI fabricated by means of additive manufacturing. The methodology provides a promising framework for the development of next-generation lightweight orthopedic implants with improved biomechanical performance and optimized material utilization.