Biomechanical analysis and optimization of gradient porous TPMS-based cervical fusion cage: a finite element study

Anterior Cervical Discectomy and Fusion (ACDF) often suffers from cage subsidence, compromising alignment and causing postoperative pain. To address this, we propose a gradient porous titanium alloy fusion cage based on Triply Periodic Minimal Surface (TPMS) structures and variable-density topology optimization. Using a Gyroid microstructure, the design was evaluated in an ACDF C4-C5 model. Compared with solid cages, the optimized design reduced maximum contact stress on the C5 superior surface by 25.6% and improved normal strain by up to 19.2%, demonstrating reduced subsidence risk and preserved biomechanical stability.