Biomechanical Comparison of Two Intervertebral Fusions for L4-L5 Spinal Segment Using the Finite Element Methods: Titanium Alloy Versus PEEK Intervertebral Fusion Cages

Purpose The primary objective of this study was to evaluate and compare the biomechanical performance of titanium alloy and polyether ether ketone (PEEK) intervertebral fusion cages in the context of L4–L5 spinal segment stabilization. The central research question addressed whether differences exist between these materials in terms of mechanical stability, specifically with regard to range of motion (ROM) reduction and stress distribution patterns. Methods A three-dimensional nonlinear finite element (FE) model of the intact L4–L5 lumbar motion segment was developed and validated. Titanium alloy and PEEK cages were separately integrated into the model. Simulations under six different loading conditions were conducted to evaluate and compare the mechanical behavior of both cage types. Results Finite element analysis demonstrated that the titanium alloy fusion cage exhibited significantly greater mechanical stability compared to the PEEK cage. Specifically, the titanium alloy cage resulted in a more pronounced reduction in ROM across all loading modes. Additionally, it showed a more uniform stress distribution along the endplates and surrounding bony structures, suggesting a lower risk of subsidence and improved load transmission. Conclusion The findings of this study indicate that titanium alloy intervertebral fusion cages offer superior biomechanical performance when compared to PEEK cages in the context of transforaminal lumbar interbody fusion (TLIF) at the L4–L5 level. These results support the potential preference for titanium alloy cages in clinical applications requiring enhanced mechanical stability during the early postoperative healing phase.