| Objective: Evaluate the effects of the spinal fusion and internal fixation on the degeneration of the adjacent segments, guided the clinical treatment of degenerative lumbar unsteadiness, suggested what is the most important in the clinical operation and which segment should be fused and fixed, guided patients how to do functional exercise.Methods: Used a finite element analysis software Super-SapV to create a finite element model of normal L2-S1 motion segment. Then finite element models of spinal segment L4-5 with disc degeneration and posterior internal fixation were established through changing the material properties of disc tissues. Cut in loading of seven orientations on them and calculated the stress alteration of the adjacent segments, and contrasted to each other.Results: 1 After fused and posterior internal fixed the L4-5 segment of degeneration, the Von Mises stress of all the node points of the adjacent segments (L3-4,L5-S1) increased under loading of all orientations (P<0.01). 2 After fused and posterior internal fixed the L4-5 segment of degeneration, the Von Mises stress of the node points of the L3-4 segments increased more significant than the L5-S1 segment under loading of anteflexion, lateriflexion and torsion (P<0.01). 3 Under the loading of torsion, the Von Mises stress of the adjacent segments increased most significant (P<0.01). Conclusion: 1 After fusion and internal fixation of degenerative lumbar unsteadiness, the Von Mises stress of the adjacent segments increased, and the proximal adjacent segment increased more significant than the distal adjacent segment. In other words, the degeneration of them was accelerated, and the proximal segment was accelerated more significant than the distal segment. 2 After fusion and internal fixation of degenerative lumbar unsteadiness, the loading of torsion accelerated the degeneration of the segments adjacent to the fused and fixed segment. |
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