<p>One of the most intricate parts of the human body is the spine. It serves multiple purposes. It supports and helps the movement of the body. It carries the weight of the entire abdomen, the upper limbs, and the head. The aim of this study is to establish a feasible 3D finite element model of the lumbar spine using the finite element method route and validate it by comparing the simulation results with data from in vitro experiments. A lumbar spine (L1–L5) finite element (FE) model was developed, and it included posterior fixation of pedicle screws (PS) at the L3–L4 segment level. This FE study investigated the impact of the posterior PS fixation system on the lumbar spine’s biomechanics using different materials for the screw-rod fixation system. Using titanium and CFR-PEEK materials, the impact of a posterior PS fixation system on lumbar spine biomechanics was examined for all physiological motions. The CFR-PEEK fixation system showed a reduction in von Misses stress at all physiological motions and an increase in the range of motion, which will increase the patient’s daily life performance rate and decrease the possibility of screw loosening and adjacent segment degeneration. The study concludes that CFR-PEEK rods are an alternate rod material to prevent the drawbacks of rigid-type rod fixation. CFR-PEEK implants have excellent mechanical stability and load-bearing capacity, reducing the likelihood of implant failure and promoting effective fusion. Results demonstrate how CFR-PEEK rods may lessen implant-related issues such as adjacent segment degeneration and screw loosening. Clinically, this could result in better long-term results for patients having lumbar fusion, decreased rates of revision surgery, and increased postoperative mobility.&#xa0;</p>