Abstract
Background: Currently, the comprehensive biomechanical evaluation of polyetheretherketone (PEEK) rods in transforaminal lumbar interbody fusion (TLIF) is limited. The purpose of this study was to compare the biomechanical differences between titanium alloy (Ti) rods and PEEK rods in TLIF. Methods: L3-5 lumbar models were developed using the finite element method. Four surgical models of TLIF were constructed by simulating different fusion methods and rods: cage fusion with Ti rods, cage fusion with PEEK rods, bone graft alone with Ti rods, and bone graft alone with PEEK rods. The range of motion (ROM) and stress distribution of the surgical and adjacent segments were then compared. Results: Compared to the Ti rods, the PEEK rods increased the ROM by 0.7–20% at the L4/5 segment and decreased the ROM by 0.8–15.1% at the L3/4 segment. The disc stresses at the L3/4 level were similar among the surgical models (0.79–1.80 MPa). The peak stresses of the screws, rods, and bone-screw interfaces in the PEEK rod models were 0–1.2 times, 1.6–4.4 times, and 0–1.4 times lower than those of the Ti rod models, respectively. PEEK rods increased the average strain of the bone graft by 0.5–61.6% and the stresses of the cage by 0.9–44.1% and endplates by 2.1–52.9%. Conclusion: In TLIF, PEEK rods played a positive role in restoring the ROM. They also increased the strain of the bone graft, stresses of the endplates and cages, and the risk of rod fracture and reduced the stress of the screw-rod system. Bone grafts alone combined with PEEK rods had acceptable biomechanical behavior in TLIF.
Bilateral pedicle screw fixation provides superior biomechanical stability in transforaminal lumbar interbody fusion: a finite element study
