下腰椎不稳融合术式的生物力学评价

Different Lumbar Fusion Methods for Management of Instability ofLower Lumbar Spine: A Biomechanical Study in Vitro

目的 观察下腰椎后路不同融合方法及疲劳对腰椎稳定性的影响。方法 9具新鲜腰 1～骶椎标本分别头尾端固定 ,在脊柱三维运动实验机上模拟人体行屈伸、左右侧弯及旋转活动 ,观察腰 4 5节段运动范围 ,随后进行各种模拟手术并安装内固定 ,依次测定失稳腰椎、CD内固定、CD加椎体间植骨、CD加TFC状态下腰 4 5的运动范围值。并在 86 8Mini MTS多轴生物力学实验机上对三种术式腰椎进行 15 0 0次疲劳加载 ,随后再观察腰 4 5节段的运动范围。结果 ①失稳腰椎与正常腰椎比较在各运动方向上运动范围均明显增加 ;②单纯CD内固定即可稳定性好 ,但疲劳后呈不稳趋势 ,在屈伸及左右旋转方向明显失稳 ;③CD加椎体间植骨、CD加TFC稳定性好 ,疲劳后仍能维持良好的稳定性 ;④CD加椎体间植骨与CD加TFC疲劳组比较在屈伸及左右侧弯时运动范围无明显差异 ,但CD加TFC在抗旋转方向优于CD加椎体间植骨。结论 单纯CD内固定能够实现腰 4 5节段即刻稳定性 ,但抗疲劳性差 ;CD内固定加椎体间植骨TFC稳定性好 ,并具有良好的抗疲劳稳定性。

Objective To investigate different lumbar fusion methods and fatigue loading in the management of instability of lower lumbar spine biomechanically in vitro.Methods A total of nine fresh human cadaver specimens from lumbar 1 to sacrum were used in this study. Each intact lumbar spine was tested in flexion-extension, lateral bending and axial rotation on a modeified testing machine with 8.0 Nm pure moment. After testing the intact lumbar spine, the L 4-5 segment instability were created by L 4 laminectomy, partial facet joint resection and discectomy. The L 4-5 functional spinal unit was then stabilized by three methods: segment pedicle screw fixation with CD implant; CD implant combined with intervertebral body strut bone graft (CD-graft) or TFC (CD-TFC). The range of motion (ROM) were determined in three dimension by stereophotogrammetry. After testing that order, 1 500 cycle fatigue loading were applied by 868 Mini-MTS, the ROM of L 4-5 were determined again by stereophotogrammetry.Results By resecting L 4 laminar, partial L 4-5 facet joint resecting and discectomy, the ROM of L 4-5 were increased significantly in all six motions. Compared with the intact lumbar spine, ROM were significantly reduced in flexion-extension by CD implant, but there were no significant changes in lateral bending and axial rotation. Both CD-graft and CD-TFC yielded high valves for stiffness in flexion-extension, lateral bending and axial rotation compared with the intact lumbar spine, even after fatigue loading test, and the ROM of L 4-5 did not increase significantly. The ROM of L 4-5 in axial rotation with CD-TFC was smaller than that with CD-graft. Conclusion All of CD implant, CD-graft and CD-TFC may provide instant stability of L 4-5. CD implant did not maintain L 4-5 segment stability after fatigue loading, but CD-graft and CD-TFC had still kept L 4-5 segment stability after fatigue loading. L 4-5 segment with CD-TFC was much stable in resisting axial rotation compared with CD-graft.