Comparative Biomechanical Evaluation of Spinal Cages Made from PCL, PEEK, and Ti6Al4V via Support-Free Additive Manufacturing

This study introduces a novel biodegradable spinal cage design optimized for additive manufacturing (AM) through topology optimization with overhang constraints, enabling the fabrication of designs without the need for support structures. The biomechanical performance of nonbiodegradable materials (Ti6Al4V and PEEK) and a biodegradable polymer (PCL) was evaluated using finite element analysis (FEA) and mechanical testing. A multilevel spinal model (T10-S1) simulates realistic biomechanics, focusing on the L4-L5 segment with a gyroid porous structure. Results demonstrate that Ti6Al4V exhibits the highest stiffness (78000 N mm-1) but raises stress-shielding concerns due to von Mises stress peaks (112.3 MPa). In contrast, PEEK and PCL demonstrate lower stress values (9.40 MPa and 7.59 MPa, respectively) and better biomechanical compatibility with spinal discs. This study highlights the potential of AM-filtered designs combined with biodegradable materials, such as PEEK and PCL, to advance patient-specific spinal cage applications while addressing challenges in AM fabrication. By eliminating support structures, this approach reduces material waste, manufacturing time, and postprocessing requirements, making spinal cage production more efficient and sustainable.