BIOMECHANICAL EVALUATION OF A NEW DESIGN OF POROUS POLYMERIC CAGES FOR POSTERIOR LUMBAR INTERBODY FUSION: FINITE ELEMENT AND EXPERIMENTAL ANALYSES

Low back pain is a vertebral column pathology that is very common throughout industrialized countries. As an essential procedure to treat degenerative spinal conditions and spondylolisthesis, spine surgeons widely use intervertebral cages for spinal fusion. Although there have been remarkable developments in interbody fusion cages, there is still room to improve cage material, design, and optimization, which leads to an improvement in the fusion rate. This study proposes a new porous structure of a polyamide-based posterior lumbar interbody fusion (PLIF) cage manufactured by 3D printing with promising mechanical strength. Cage models with three different pore sizes (0.6, 0.8 and 1 mm) were designed using finite element (FE) modeling. The ultimate stress of cage models was predicted under an axial compression test simulated via the FE analysis program. Thereafter, samples of each cage structure were manufactured using the 3D printing method and the polyamide material. A displacement-control compression test was performed to establish the mechanical properties of the cage models. Results of the FE simulation revealed that cage P0.6 (void size of 0.6[Formula: see text]mm) presented the highest ultimate stress among the three cage models. The result of the experimental test also indicated that cage P0.6 has the most considerable ultimate stress and stiffness. Findings of the FE analysis were in good agreement with those of the experimental test. Cage model P0.6, therefore, was considered the most mechanically suitable cage structure for a spinal fusion cage.