Dong Jian-wen, Feng Feng, Zhao Wei-dong, Rong Li-min, Liu Xiao-ming
Department of Spine Surgery, the Third Affiliated Hospital of Sun Yat-sen University, Guangzhou 510630, China.
Zhonghua Wai Ke Za Zhi. 2011 May 1;49(5):436-9.
To analyze the biomechanical efficacy of unilateral pedicle screw fixation on human cadaveric lumbar spine model simulated by two-level posterior lumbar interbody fusion (PLIF).
Six fresh-frozen adult human cadaveric lumbar spine motion segments (L(2)-S(2)) were simulated to unilateral/bilateral L(4)-S(1) PLIF constructs augmented by unilateral/bilateral pedicle screw fixation sequentially and respectively. All configurations were tested by MTS 858 in the following sequential construct order: the intact, UI (unilateral instability), UIUF1C (unilateral instability via unilateral pedicle screw fixation plus one cage), BIUF1C (bilateral instability via unilateral pedicle screw fixation plus one cage), BIBF1C (bilateral instability via bilateral pedicle screw fixation plus one cage) and BI (bilateral instability without pedicle screw and cage). Each specimen was nondestructively tested in flexion/extension, lateral bending, and axial rotation. An axial compressive load ranged from 40 N to 360 N and the maximum peak moment of 8 N·m was applied during testing. The range of motion (ROM) and neutral zone (NZ) of fusion segment were recorded by a 6-Eagle Motion Analysis F40 system, and then statistic comparison were performed between different simulated constructs with One Way of ANOVA and Post hoc LSD tests.
BIBF1C had the lowest ROM and NZ of L(4)-S(1) fusion segments in all loading models, which were significantly lower than those of any uninstrumented construct (the intact, UI and BI) (P < 0.05). In flexion/extension, lateral bending, and axial rotation, the ROM of UIUF1C was respectively 2.53 ± 1.12, 4.03 ± 2.19, 2.78 ± 1.00 and the NZ of UIUF1C was respectively 1.14 ± 0.70, 1.96 ± 1.13, 1.28 ± 0.71, which were significantly lower than those of the intact (P < 0.05). Compared to BIBF1C, the ROM and NZ were respectively increased 60.13% and 17.52% in flexion/extension, 315.46% and 243.86% in lateral bending, 8.17% and 6.20% in axial rotation, however, there were no significant differences between these two constructs (P > 0.05). In lateral-bending and axial rotation, the ROM and NZ of BIUF1C were significantly higher than those of BIBF1C (P < 0.05). In flexion/extension, the ROM and NZ of BIUF1C were higher than those of BIBF1C but there were no significant differences (P > 0.05). Compared to the intact, BIUF1C had lower ROM and NZ except for higher NZ in axial rotation, and there were significant differences only in flexion/extension (P < 0.05).
All tested two-level unilateral fixation on simulated human cadaveric model with unilateral PLIF can achieve similar initial biomechanical stability in comparison with two-level bilateral pedicle screw fixation. However in most test modes, two-level unilateral pedicle screw fixation on simulated human cadaveric model with bilateral PLIF can not achieve enough biomechanical efficacy in comparison with two-level bilateral pedicle screw fixation.
分析在两级后路腰椎椎间融合术（PLIF）模拟的人体尸体腰椎模型上，单侧椎弓根螺钉固定的生物力学效果。
依次分别对6个新鲜冷冻的成人尸体腰椎运动节段（L₂-S₂）模拟单侧/双侧L₄-S₁PLIF结构，并通过单侧/双侧椎弓根螺钉固定进行强化。所有构型按以下顺序通过MTS 858进行测试：完整状态、UI（单侧不稳定）、UIUF1C（通过单侧椎弓根螺钉固定加一个椎间融合器实现单侧不稳定）、BIUF1C（通过单侧椎弓根螺钉固定加一个椎间融合器实现双侧不稳定）、BIBF1C（通过双侧椎弓根螺钉固定加一个椎间融合器实现双侧不稳定）和BI（无椎弓根螺钉和椎间融合器的双侧不稳定）。每个标本在屈伸、侧弯和轴向旋转时进行无损测试。测试过程中施加40 N至360 N的轴向压缩载荷以及8 N·m的最大峰值力矩。融合节段的活动范围（ROM）和中性区（NZ）通过6-Eagle Motion Analysis F40系统记录，然后采用单因素方差分析和事后LSD检验对不同模拟构型进行统计学比较。
在所有加载模型中，BIBF1C的L₄-S₁融合节段的ROM和NZ最低，显著低于任何未植入器械的构型（完整状态、UI和BI）（P<0.05）。在屈伸、侧弯和轴向旋转时，UIUF1C的ROM分别为2.53±1.12、4.03±2.19、2.78±1.00，NZ分别为1.14±0.70、1.96±1.13、1.28±0.71，均显著低于完整状态（P<0.05）。与BIBF1C相比，屈伸时ROM和NZ分别增加60.13%和17.52%，侧弯时分别增加315.46%和243.86%，轴向旋转时分别增加8.17%和6.20%，但这两种构型之间无显著差异（P>0.05）。在侧弯和轴向旋转时，BIUF1C的ROM和NZ显著高于BIBF1C（P<0.05）。在屈伸时，BIUF1C的ROM和NZ高于BIBF1C，但无显著差异（P>0.05）。与完整状态相比，BIUF1C除轴向旋转时NZ较高外，ROM和NZ较低，仅在屈伸时有显著差异（P<0.05）。
在模拟人体尸体模型上进行的所有测试两级单侧固定联合单侧PLIF与两级双侧椎弓根螺钉固定相比，可实现相似的初始生物力学稳定性。然而，在大多数测试模式下，在模拟人体尸体模型上进行的两级单侧椎弓根螺钉固定联合双侧PLIF与两级双侧椎弓根螺钉固定相比，无法实现足够的生物力学效果。
