Facet joint loading after Kevlar-reinforced disc replacement vs. lumbar fusion. A cadaveric model study.

Background: Lumbar spinal fusion, while effective for degenerative disc disease, eliminates motion and may accelerate adjacent segment degeneration. Total disc replacement (TDR) with anterior annular reinforcement may offer a motion-preserving alternative. Objective: To compare spinal kinematics and facet joint pressures between (1) total lumbar disc replacement with anterior Kevlar band reinforcement (TDR group) and (2) standard 360° lumbar fusion (fusion group) in a cadaveric model. Methods: Six fresh-frozen human lumbar spines (L2-S1) were tested in a custom motion simulator under both surgical conditions at L4-L5. Kinematic parameters included range of motion (ROM), peak angles, and motion harmony (angle-acceleration correlation). Zygapophyseal joint pressures were measured using Tekscan sensors. Data were analyzed using repeated-measures ANOVA. Results: The TDR group preserved significantly greater flexion (-25.7° vs -21.8°, p < 0.001) and left axial rotation (p = 0.025), while the fusion group showed greater extension (p < 0.001). TDR demonstrated superior motion harmony across all axes (p < 0.01) and better preserved ROM at adjacent levels. No significant differences in mean maximum facet joint pressures were observed (p > 0.05), though slightly higher values were noted in TDR during axial rotation. Conclusion: Anterior annular reconstruction with Kevlar bands during total disc replacement restores near-physiological motion and improves kinematic control without increasing facet joint stress. This technique may offer a biomechanically favorable alternative to lumbar fusion.