Biomechanical Study Of Lumbar Spine With Rigid And Dynamicstabilization Device Using Finite Element Method

Objective: To predict the biomechanics due to the insertion of the rigid and dynamic spinal stabilization system using a finite element model of the spinal segments (L₃–L₅)Methods: In this study, a detailed L₃-L₅ level three dimensional nonlinear finite element model of a normal aged 30 man was established with the aid of two softwares , Geomagic and Ansys, which can derive a three-dimensional finite element model from CT images. The model was validated in contrast to the former biomechanical studies of cadaveric spine. The model was then fused at the L4.5 level. Two spines were analysed and compared: (1) L3.4 level was done nothing; and (2) L3.4 level stabilized with a dynamic stabilization device。Result:A finite element model of the spinal segments (L3–L5) was developed. Biomechanical analysis was done between rigid and dynamic spinal stabilization system,and the simulation results suggested that the implant caused a reduction in range of motion of the instrumented level,stress concentration on the facet joint disappear and distribute uniformly in the bilateral pedicle. The intervertebral disc at the L3.4 level was unloaded by40.6% in flexion, by 41% in extension, and by 76% in lateral flexion, while no variations in pressure were caused by the device in axial compress but more uniform distribution.Conclusion: A dynamic fixator at an adjacent segment is superior to a posterior rigid fixation device,for it can reduce the range of motion of the adjacent segments, significantly depresse the pressure of intervertebral disc,and prevent facet joint and intervertebral disc stress concentration. The use of dynamic stabilization devices may effectively prevent adjacent segment degeneration accelerated after fusion.