Chiang Ming-Fu, Zhong Zheng-Cheng, Chen Chen-Sheng, Cheng Cheng-Kung, Shih Shih-Liang
Department of Neurosurgery, Mackay Memorial Hospital, Mackay Medicine, Nursing and Management College, Taipei Medical University, Taipei, Taiwan.
Spine (Phila Pa 1976). 2006 Sep 1;31(19):E682-9. doi: 10.1097/01.brs.0000232714.72699.8e.
Using finite element models to study the biomechanics of lumbar instrumented posterior lumbar interbody fusion (PLIF) with one or two cages.
Analyzing the biomechanics of instrumented PLIF with one or two cages as to evaluate whether a single cage is adequate for instrumented PLIF.
Implantation of a single cage in instrumented PLIF of lumbar spine is still controversial.
Three validated finite element models of L3-L5 lumbar segment were established [intact model (INT), one cage model (LS-1), and two cages model (LS-2)]. The available finite element program ANSYS 6.0 (Swanson Analysis System Inc., Houston, TX) was applied. To analyze the biomechanics of these models, 10 Nm flexion, extension, rotation, and lateral bending moment with 150 N of preload were respectively imposed on the superior surfaces of the L3.
Compared with the INT model, the decrease of ROM in the LS-1 and LS-2 models were exaggerated from 0.67 degrees to 3.73 degrees and ranged from 37.2% to 86.1% in all motions. The mean subsidence was found to be slightly higher in the LS-1 model. Most of the cage dislodgement in both models was less than 0.03 mm. The mean dislodgement was slightly higher in the LS-1 model. The stress of cage was found to be high in the LS-2 model. The mean stress of screw was raised to 4.5% to 9.7% in the LS-1, which was higher than that in the LS-2 model. In general, stress of adjacent disc was more pronounced in the LS-2 model. The most stress distributed at the anterior portion of the adjacent disc, which could be used to interpret the clinical findings of the early adjacent disc degeneration.
A single cage inserted in an instrumented PLIF gains approximate biomechanical stability, slight greater subsidence, and a slight increase in screw stress but less early degeneration in adjacent disc. Adjusting these factors, instrumented PLIF with one cage could be encouraged in clinical practice.
使用有限元模型研究采用一个或两个椎间融合器的腰椎后路器械辅助腰椎椎间融合术（PLIF）的生物力学。
分析采用一个或两个椎间融合器的器械辅助PLIF的生物力学，以评估单个椎间融合器对于器械辅助PLIF是否足够。
在腰椎器械辅助PLIF中植入单个椎间融合器仍存在争议。
建立了三个经验证的L3-L5腰椎节段有限元模型[完整模型（INT）、单融合器模型（LS-1）和双融合器模型（LS-2）]。应用现有的有限元程序ANSYS 6.0（Swanson分析系统公司，得克萨斯州休斯顿）。为分析这些模型的生物力学，分别在L3上表面施加10 Nm的前屈、后伸、旋转和侧方弯曲力矩以及150 N的预载荷。
与INT模型相比，LS-1和LS-2模型中活动度（ROM）的降低在所有运动中从0.67度夸大到3.73度，范围为37.2%至86.1%。发现LS-1模型中的平均下沉略高。两个模型中大多数椎间融合器的移位小于0.03 mm。LS-1模型中的平均移位略高。发现LS-2模型中椎间融合器的应力较高。LS-1模型中螺钉的平均应力提高到4.5%至9.7%，高于LS-2模型。总体而言，LS-2模型中相邻椎间盘的应力更明显。最大应力分布在相邻椎间盘的前部，这可用于解释早期相邻椎间盘退变的临床发现。
在器械辅助PLIF中植入单个椎间融合器可获得近似的生物力学稳定性、稍大的下沉以及螺钉应力的轻微增加，但相邻椎间盘的早期退变较少。综合考虑这些因素，临床上可鼓励采用单个椎间融合器的器械辅助PLIF。
