颈椎前路单节段减压融合与减压融合联合钢板内固定对相邻节段生物力学效应的有限元分析

Finite element analysis of biomechanical effects of anterior cervical single-segment decompression fusion and decompression fusion combined with internal fixation on adjacent segments

目的比较颈椎前路单节段减压融合与减压融合联合钢板内固定对相邻节段生物力学的效应。方法根据1例正常成人的颈椎CT构建C3-C7有限元模型,验证模型有效性。在此模型基础上,分别以C4/5或C5/6为融合部位,构建颈前路单纯减压融合与减压融合联合钢板的术后模型。以无损模型和术后模型作为研究对象,约束C7椎体的下表面,于C3椎体的上表面施加73.6 N的轴向力和1 N·m的力矩,比较融合部位相邻节段的活动度以及纤维环和髓核应力的差异。结果与C4/5单纯融合模型相比,C4/5联合钢板模型上级节段活动度和应力均增大,其中活动度最大增幅为5.44%,纤维环与髓核应力的最大增幅为8.10%;而下级节段活动度和应力降低,其中活动度最大降幅为17.29%,纤维环与髓核应力的最大降幅分别为21.96%和15.67%。与C5/6单纯融合模型相比,C5/6联合钢板模型上级节段活动度和应力主要表现为增长,其中活动度最大增幅为4.64%,纤维环和髓核的最大应力增幅分别为7.16%和6.84%;而下级节段C6/7活动度和应力主要表现为降低,其中活动度最大降幅为7.85%,纤维环和髓核应力的最大降幅分别为12.52%和6.74%。结论相比于单纯融合模型,联合钢板模型上级水平的活动度和应力增加,而下级水平的活动度和应力降低。联合钢板可能会促进融合部位上级水平椎间盘的退变,减缓下级水平因融合造成的应力增加。

【Objective】To compare the effects of anterior cervical single-segment decompression fusion and decompression fusion combined with plate internal fixation on the biomechanics of adjacent segments.【Methods】A C3-C7 finite element model was constructed based on the CT of a normal adult cervical spine to verify the validity of the model.Then,based on this model,postoperative models of anterior cervical simple decompression fusion and decompression fusion combined with plates were constructed with C4/5 or C5/6 as the fusion sites,respectively.Then,the nondestructive model and the postoperative model were used as the study objects to constrain the lower surface of the C7 vertebral body and apply an axial force of 73.6 N and a moment of 1 N·M on the upper surface of the C 3 vertebral body to compare the rang of motion of the adjacent segments at the fusion site and the differences in the stresses on the annular fibrous and the nucleus pulposus.【Results】Compared with the C4/5 simple fusion model,both range of motion and stress increased in the superior segment of the combined C4/5 plate model,with a maximum increase in range of motion of 5.44%and a maximum increase in annular fibrous and nucleus pulposus stress of 8.10%;whereas range of motion and stress decreased in the inferior segment,with a maximum decrease in range of motion of 17.29%and a maximum decrease in annular fibrous and nucleus pulposus stress of 21.96%and 15.67%,respectively.Compared with the C5/6 simple fusion model,the range of motion and stress in the superior segment of the C5/6 combined plate model mainly showed an increase,with the maximum increase in range of motion of 4.64%and the maximum increase in stress in the annulus fibrosus and nucleus pulposus of 7.16%and 6.84%,respectively;while the range of motion and stress in the inferior segment of C 6/7 mainly showed a decrease,with the maximum decrease in range of motion of 7.85%and the maximum decrease in stress in the annulus fibrosus and nucleus pulposus of 12.52%and 6.74%,respectively.【Conclusion】Compared with the simple fusion model,the combined plate model showed increased range of motion and stress at the superior level and decreased range of motion and stress at the inferior level.The combined plate may promote disc degeneration at the superior level of the fusion site.