Biomechanical study of lumbar spine with dynamic stabilization device using finite element method

A finite element model of the human lumbar spine was developed for the parametric study of the stiffness of a dynamic stabilization device. Spinal segments (L2–L5) were used to investigate the effect of dynamic stabilization and the influence on the mobility of adjacent intervertebral segments. Three spines were analysed and compared: (1) a lumbar spine with intact discs, used as a reference; (2) a fused spine with a fixation device after the the facetectomy and the total laminectomy; and (3) a spine stabilized with a dynamic stabilization device after the facetectomy and the total laminectomy.The Range of Motion (ROM) and the intervertebral disc pressure of L3–L4 and the ROM and disc pressure of the adjacent segments were examined to determine the influence of the implant on the adjacent segments.In the case of the dynamically stabilized spine, the total ROM was greater than that of the fused spine but similar to that of the intact spine. Furthermore, the disc pressure on the adjacent segments in the fused spine was greater than that of the intact spine, but the disc pressure of the dynamically stabilized spine was similar to the intact spine. In particular, the dynamic stabilization device having a stiffness of 10–15 N/mm made the destabilized spine more similar to the intact spine.Results indicated that the use of dynamic stabilization devices restored functionality closer to that of the intact spine as compared to the fused spine. The stiffness value utilized in the device was determined to be an important design parameter in manufacturing the dynamic stabilization device.