多裂肌损伤对腰椎后路椎间融合术后邻近节段生物力学的影响

Biomechanical effects of multifidus injury on adjacent segments after posterior lumbar interbody fusion

中文关键词:  腰椎后路椎间融合  多裂肌  生物力学  邻近节段  有限元分析

英文关键词:Posterior lumbar interbody fusion  Multifidus  Biomechanics  Adjacent segment  Finite element analysis

中文摘要:

  【摘要】 目的：应用有限元分析探讨多裂肌损伤对腰椎后路椎间融合术后邻近节段生物力学的影响。方法：提取1名健康成年人的腰骶椎CT图像数据，建立L1~L5和骶椎的有限元模型并进行有效性验证，通过建立参考点并设置载荷方向和大小模拟多裂肌的作用，得到正常生理模型（normal model，NM），并分别建立L4/5后路融合模型（posterior fusion model，PFM）、多裂肌离断模型（multifidus severed model，MSM）、L4/5后路融合同时离断近端多裂肌模型（posterior fusion and multifidus severed model，PFMSM）。在NM的L1上终板调整多裂肌肌力和外部载荷，施加7.5N·m力矩载荷分别模拟前屈、后伸、侧弯和扭转运动，记录这四种运动工况下L1上终板的转动角度分别为18.8°、14.4°、15.4°和12.5°，其余三种模型以此参照在L1上终板施加不同力矩载荷模拟前屈、后伸、侧弯和扭转运动达到相同转动角度，分析各模型的多裂肌肌力及总做功情况、上下邻近节段（L3/4、L5/S1）的活动度（range of Motion，ROM）和椎间盘最大Von Mises应力。结果：正常腰骶椎模型有效性得到验证。相比NM，PFM、MSM和PFMSM的多裂肌平均肌力分别增加63.41％、38.16％和84.43％，多裂肌总做功在前屈时分别增加30.02%、6.40%和39.95%，其他三种工况增加的百分比与前屈时相近。在不同运动工况下邻近节段ROM的变化，相比NM，PFM在L3/4增加12.85％~40.06%，在L5/S1增加11.73%~68.77%；MSM在L3/4前屈、后伸增加13.78%、7.51%，侧弯和扭转时分别减少7.30%和4.81%，在L5/S1增加0.26%~20.72%；PFMSM在L3/4增加16.15%~27.86%，在L5/S1增加14.38%~39.67%。椎间盘最大Von Mises应力方面，相比NM，PFM在L3/4增加15.52%~48.55%，在L5/S1增加6.97%~65.13%；MSM在L3/4前屈、后伸时分别增加1.05%、0.10%，侧弯和扭转时分别减少6.13%和12.33%，在L5/S1前屈时增加15.09%，后伸、侧弯和扭转时分别减少12.91%、4.96%、2.18%；PFMSM在L3/4增加18.94%~30.85%，在L5/S1增加20.08%~38.92%。结论：腰椎后路椎间融合和近端多裂肌的离断均会导致上下邻近节段ROM和椎间盘的Von Mises应力增加，腰椎后路椎间融合和近端多裂肌离断同时存在时对邻近节段的生物力学影响最大，尤其在前屈运动时较为明显。

英文摘要:

  【Abstract】 Objectives: To investigate the biomechanical effects of multifidus injury on adjacent segments after posterior lumbar interbody fusion using finite element analysis. Methods: A finite element model of the lumbar spine of L1-L5 and sacral spine was constructed according to the CT image data of the lumbosacral spine of a healthy adult, and the validity was verified. The function of multifidus muscle under normal physiological conditions was simulated by establishing reference points and setting load direction and magnitude, through which the normal model(NM) was obtained. And the L4/5 posterior fusion model(PFM), the multifidus severed model(MSM), the posterior fusion and multifidus severed model(PFMSM) were established respectively. A 7.5N·m moment load was applied to the superior endplate of L1 of the NM to simulate flexion, extension, lateral bending and torsion, respectively, the rotation angles of the upper endplate of L1 during different motion conditions were recorded as 18.8°, 14.4°, 15.4° and 12.5°, respectively. Taking NM as reference,different moment loads were applied on L1 upper endplate of the other three models to simulate flexion, extension, lateral bending and torsion to achieve the same rotation angle, after that the muscle strength and the total work of multifidus, the range of motion(ROM) and the maximum Von Mises stress of the intervertebral discs of the upper and inferior adjacent segments(L3/4, L5/S1) were analyzed statistically. Results: The validity of normal lumbosacral model was demonstrated. Compared with the NM, the average multifidus muscle strength increased by 63.41%, 38.16% and 84.43% in the PFM, MSM and PFMSM, respectively. The total work of multifidus increased by 30.02%, 6.40% and 39.95% during flexion, respectively, which increased by similar percentages during the other three motion conditions. The changes in the ROM of adjacent segments during different motion conditions, compared with the NM, the PFM increased by 12.85%-40.06% in L3/4 and 11.73%-68.77% in L5/S1; the MSM increased by 13.78% and 7.51% in L3/4 during flexion and extension, decreased by 7.30% and 4.81% during lateral bending and torsion, and increased by 0.26%-20.72% in L5/S1; the PFMSM increased by 16.15%-27.86% in L3/4 and 14.38%-39.67% in L5/S1. In the aspect of the maximum Von Mises stress of the intervertebral discs, compared with the NM, the PFM increased by 15.52%-48.55% in L3/4 and 6.97%-65.13% in L5/S1, the MSM group increased by 1.05% and 0.10% during flexion and extension, decreased by 6.13% and 12.33% during lateral bending and torsion in L3/4, increased by 15.09% during flexion, and decreased by 12.91%, 4.96%, 2.18% during extension lateral bending and torsion in L5/S1; the PFMSM increased by 18.94%-30.85% in L3/4 and 20.08%-38.92% in L5/S1. Conclusions: Posterior lumbar interbody fusion and the severing of upper multifidus will cause the increase of the ROM and the Von Mises stress of the intervertebral disc in the upper and lower adjacent segments. The concurrence of posterior lumbar interbody fusion and the severing of upper multifidus have the greatest biomechanics effects on the adjacent segments, especially in flexion.