The Finite Element Analysis of Postoperative Adjacent Segmental Lumbar Fusion Intervertebral Disc Stress

Abstract：Objective:To analysis model under different loads and stress changes by posterior lumbar discectomy through the establishment of normal, L4-5 and L4-S1 fusion and internal fixation model.Method: Analyzed 98 image nodes from 1 volunteers what were divided unit to establish the normal lumbar motion segment (L1-S1) finite element model and L4-5, L4-S1 segment of posterior lumbar interbody fusion and internal fixation model, the three models with five direction load, calculation of adjacent segment disc shall be stress variation, and the results were statistically analyzed.Result: The research showed that the upper two segments adjacent segment than the single disc fusion segment average effective stress in flexion, extension , lateral flexion , rotation load difference was statistically significant(P<0.05), vertical compression load no statistically significant difference(P>0.05), whether it was single or double segment L4-5 segment L4-S1 was fixed , the neighboring L3~4 disc effective stress in flexion, extension , vertical compression , lateral flexion, rotation were greater than unfused fixed, the difference was statistically significant(P<0.05), for each pairwise comparison loading , load average stress decreasing order of rotation, lateral flexion , extension, flexion and vertical compression, and the difference between any two distinct , with statistical significance(P<0.05).Conclusion: After posterior lumbar interbody fusion, segmental fixation stress is much higher than that of non stress fusion adjacent intervertebral disc, and easier to speed up the adjacent intervertebral disc degeneration, 2-level lumbar fusion and internal fixation is better than that of single segment in the most active state to accelerate the adjacent intervertebral disc degeneration, especially the rotary activities.