使用椎弓根钉固定的PLF和PLIF的生物力学比较

Biomechanical comparison of PLF and PLIF with pedicle screw fixation in unstable lumbar spine

目的比较在失稳腰椎使用椎弓根钉固定的侧后方融合和经后路椎体间融合的生物力学效果.方法 10具L3～S1人新鲜尸体腰椎标本用于实验.完整脊柱测试后,于L4,5后方行连续性破坏,并用椎弓根钉固定(PS)和椎体间cage行以下各脊柱重建组:①完整脊柱及PS组.②两侧关节突关节内侧切除及PS组.③两侧关节突关节完全切除及PS组.④椎间盘部分切除及PS组.⑤椎间盘部分切除及PS/cage组.各组分别行载荷量6 Nm的前后屈曲实验,记录并比较固定椎间L4,5的刚度值、L4椎弓根钉的折曲应变量、及上位相邻关节L3,4的运动范围(ROM).结果固定椎间L4,5的刚度值:椎间盘部分切除及PS以外的所有重建组的脊柱刚度均显著大于完整脊柱组,椎间盘部分切除及PS/cage组的脊柱刚度显著大于其他固定组.L4螺钉的折曲应变量:椎间盘部分切除及PS组L4螺钉折曲应变量显著大于其他固定组,而椎间盘部分切除及PS/cage的螺钉应变量在所有重建组中最小.L3,4的ROM:与完整脊柱相比,所有重建组都显著增大了L3,4的ROM.更重要的是椎间盘部分切除及PS/cage组的ROM明显大于单纯PS组.结论若脊柱前方承载能力尚存,使用PS的侧后方融合可获得足够的力学稳定性.在此情况下,椎体间融合会进一步加大相邻关节的活动范围,故不应使用.当脊柱前方丧失其承载能力,单纯PS的脊柱刚度低,椎弓根钉的应力显著增大.对此种病例,cage的使用可增加重建脊柱的初期稳定性,有利于降低后方固定器械的应力.

ObjectiveTo compare biomechanical effects of the posterolateral fusion (PLF) and posterior lumbar interbody fusion (PLIF) with pedicle screw fixation for various spinal instabilities. MethodsLumbar spine (L 3 -S 1 ) specimens from ten human cadavers were used. Sequential destabilization was performed at the posterior of L 4,5 and following posterior reconstruction using the pedicle screw fixation (PS) and interbody cages as follows: (1) intact and PS (IPS), (2) medial facetectomy and PS (MFPS), (3) total facetectomy and PS (TFPS), (4) partial discectomy and PS (DPS), and (5) partial discectomy and PS and interbody cages (DPSC). Biomechanical test was performed under 6 Nm flexion and extension loading modes. Construct stiffness (L 4,5 ), L 4 screw bending strain, and range of motion (ROM) of the upper adjacent level (L 3,4 ) were analyzed. Results Construct Stiffness (L 4,5 ): All reconstructions except DPS demonstrated significantly higher construct stiffness than the intact spine, and the DPSC revealed the highest stiffness among the all reconstructions. L 4 Screw Bending Strain: The DPS resulted in significantly higher strain than the other groups, and the DPSC presented statistically less strain than the other reconstructions. ROM (L 3,4 ): All reconstructions significantly increased the ROM compared to the intact. Importantly, the DPSC showed significantly greater ROM than the PS. ConclusionFor spinal instability with preserved anterior load-sharing, PLF using PS is biomechanically adequate and interbody fusion should not be performed as it further increases range of motion at the adjacent segment. However, only PS demonstrates lower spinal stiffness and higher implant strain following partial discectomy. In such cases, additional interbody cages significantly increase construct stiffness and decrease hardware strain.