This study examines the biomechanical performance of intervertebral cage implants with different sizes and materials using the finite element analysis method. Static analysis revealed the impact of implant size and material type on the stress distribution in the spine, and it was determined that Ti alloy implants induce higher stresses compared to PEEK implants. While small-sized implants exhibited higher stress concentrations, larger implants distributed the load more evenly. Fatigue analyses based on the Goodman criterion indicated that implant size is a decisive factor in fatigue strength. In Ti alloy implants, the highest equivalent alternating stress values were observed in the larger designs, thereby reducing fatigue life. PEEK implants, owing to their lower stiffness, reduced the stress shield but resulted in greater deformation in the screw systems. In the M1 titanium cage, the highest equivalent alternating stress was recorded as 340.88 MPa, indicating reduced fatigue resistance in smaller implant designs. Conversely, the M3 PEEK cage exhibited the lowest stress value (32.31 MPa), demonstrating the benefit of larger, more compliant structures in distributing load effectively. The results demonstrate that in the design of intervertebral cages, the choice of size and material is critical for mechanical stability and long-term implant success. While larger implants optimize load distribution, material selection must be carefully evaluated to achieve biomechanical balance.
Fahri Murat (Sat,) studied this question.