腰椎皮质骨螺钉联合椎弓根螺钉固定对融合节段应力影响的有限元分析

Finite element analysis of the effect on the stress of fusion segment by fixation combining lumbar cortical bone screw and pedicle screw

中文关键词:  皮质骨螺钉  椎弓根螺钉  腰椎融合  有限元分析  生物力学

英文关键词:Cortical bone trajectory screw  Pedicle screw  Lumbar fusion  Finite element analysis  Biomechanics

中文摘要:

  【摘要】 目的：应用三维有限元法分析腰椎皮质骨螺钉（cortical bone trajectory screw，CBTS）联合椎弓根螺钉（pedicle screw，PS）固定对融合节段应力的影响。方法：采集1例正常成年人腰椎三维重建CT数据，应用三维有限元方法建立L3/4节段PS固定（A组）、CBTS固定（B组）和联合固定（C组）腰椎融合模型。固定L5椎体下表面，对模型施加7.5N·m力矩模拟脊柱在生理负荷状态下前屈、后伸、侧屈及旋转运动。分析3组内固定、椎间融合器和椎间植骨的应力峰值，并测量各组在生理运动下L3/4节段的活动度（range of motion，ROM）。结果：与A组相比，B组和C组模型在腰椎六维运动下螺钉和连接棒的应力显著增加。其中，在前屈时L3螺钉应力B组较A组增加84.7%，C组较A组增加79.7%；在后伸时L3螺钉应力C组较A组增加47.7%，较B组增加46.3%；在左侧屈时，L3螺钉应力C组较A组增加72.5%，较B组增加30.5%；在右侧屈时，L3螺钉应力C组较A组增加71.9%，较B组增加30.0%。前屈时L4螺钉应力B组较A组增加11.6%，C组较A组增加18.9%；后伸时L4螺钉应力B组较A组增加40.1%，C组较A组增加109.3%。在左右旋转时，L3和L4螺钉应力总和C组较A组增加37.9%，较B组增加1.4%。在左侧屈时，连接棒应力C组较A组增加48.8%，较B组增加13.0%；在右侧屈时，连接棒应力C组较A组增加8.8%，较B组增加4.9%。A、B、C组固定模型Cage的应力总和分别为318.8MPa、319.6MPa和311.4MPa。在L3/4节段ROM方面，B组在屈、伸方向ROM最小，而在侧屈和侧旋方向ROM最大。结论：CBTS固定技术可增加腰椎融合节段的内固定结构的力学强度。CBTS和PS的联合应用可进一步增加手术节段的力学强度和稳定性，同时获得相似的椎间融合应力环境。

英文摘要:

  【Abstract】 Objectives: We aimed to analyze the effect of the combined application of lumbar cortical bone trajectory screw(CBTS) and pedicle screw(PS) on the stress of fusion segment using three-dimensional finite element method. Methods: Lumbar CT data was collected from a healthy adult. The finite element method was applied tosimulate the lumbar fusion(L3/4) models, including PS fixation(group A), CBTS fixation(group B), and CBTS and PS combined fixation(group C). The lower surface of the L5 vertebral body was fixed, and 7.5N·m torque was applied to the model to simulate spinal flexion, extension, lateral flexion and rotation under physiological load. Range of motion(ROM) at L3/4 level was measured under physiological movement, and the stress peaks of internal fixation, interbody fusion device and interbody bone grafting were analyzed. Results: The stress of screw and connecting rod of group B and group C increased significantly comparing with that in group A in the 6 motion dimensions of the lumbar spine. During flexion, comparing with that in group A, the L3 screw stress increased by 84.7% in group B and 79.7% in group C. During extension, the stress of L3 screw in group C increased by 47.7% and 46.3% comparing with that in groups A and B, respectively. In left flexion, the stress of L3 screw in group C increased by 72.5% and 30.5% comparing with that in groups A and B. In right flexion, the stress of L3 screw in group C increased by 71.9% and 30.0% comparing with that in groups A and B. During flexion, comparing with that in group A, the L4 screw stress increased by 11.6% in group B and 18.9% in group C. During extension, comparing with that in group A, L4 screw stress increased by 40.1% in group B and 109.3% in group C. During rotation, screws stress of L3 and L4 in group C increased by 37.9% and 1.4% comparing with that in groups A and B. In left flexion, the stress of connecting rod in group C increased by 48.8% and 13.0% comparing with that in groups A and B. In the right flexion, the stress of connecting rod in group C increased by 8.8% and 4.9% comparing with that in groups A and B. The total stresses of Cage in the three groups were 318.8MPa, 319.6MPa, and 311.4MPa respectively. Group B had the smallest ROM in flexion and extension, and the largest ROM in lateral flexion and lateral rotation. Conclusions: CBTS fixation can increase the mechanical strength of the internal fixation structure of the lumbar fusion segment. The combined application of CBTS and PS can further increase the mechanical stability of the surgical segment while obtaining a similar stress environment for intervertebral fusion.