胸腰椎不同程度前中柱骨折内固定后的生物力学特征及前路重建的意义

目的分析胸腰椎不同程度前中柱骨折经椎弓根螺钉内固定器固定后的生物力学效果，并探讨前路重建的生物力学意义。方法收集12具新鲜猪T10～L4节段胸腰椎脊柱标本，分为两组，将L1椎体行两种不同范围的“V”形预损伤，然后前屈压缩至“V”形区破坏，造成不同程度前中柱骨折。对骨折标本依次进行以下处理：安放AF椎弓根螺钉内固定器；AF内固定加前路植骨重建。每种状态依次在CMT4104多功能力学试验机上进行轴向压缩和前屈压缩测试，分别计算每组的完整标本、骨折内固定标本和植骨内固定标本的轴向压缩刚度和前屈压缩刚度。结果标本前中柱骨折经椎弓根螺钉内固定后轴向刚度和前屈压缩刚度较完整标本明显下降（P〈0．01），椎体前中柱较大范围累及的骨折与较小范围累及者相比，刚度下降更明显（P〈0．01），而前路植骨重建者刚度恢复至完整标本水平（P〉0．05）；同一状态轴向压缩刚度明显大于前屈压缩刚度（P〈0．01）。结论胸腰椎前中柱骨折后经椎弓根螺钉系统固定不能使其恢复至原来的力学性能，椎体骨折累及范围越大，固定后力学性能越差；前中柱重建是减少后路内固定器械承载的关键。

Biomechanic character and anterior reconstruction significance posterior to internal fixation of various extents of anterior median spine fractures of thoracolumbar vertebrae

Objective To analyze the biomechanic effect of internal fixation of vertebral pedicle screw on various extents of anterior median spine fractures of thoracolumbar vertebrae and evaluate biomechanic significance of anterior reconstruction. Methods Twelve fresh porcine T_ 10 -L_4 vertebrae were harvested and divided into two groups. The L_1 segment of the vertebrae suffered V-shaped preinjury by flexion-compression at two different extents and then was mounted in the CMT 4104 testing machine. The fracture specimen was first placed with an AF vertebral pedicle internal fixator and then treated with AF internal fixation plus anterior implant reconstruction. Stiffness of axial compression and anteflexion compression was measured at every status on the CMT 4104 testing machine to compare with that of the intact specimens. Results In the fixation alone group, the stiffness of axial compression and anteflexion compression was significantly lower than that of the intact group (P<0.01). The construction stiffness had an association with the extent of vertebral body comminution, ie, less extent of vertebral body comminution had significantly higher compression stiffness than greater extent (P<0.01). While the compression stiffness of anterior reconstruction recovered to level of the intact specimens (P>0.05). At a same status, the axial compression stiffness was significantly higher than the anteflexion compression stiffness (P<0.01). Conclusions Transpedicular fixation of anterior median spine fractures of thoracolumbar vertebrae can not provide efficient stability for thoracolumbar fractures, with larger extent of vertebral body comminution resulting in poorer construction stability. Recovering mechanical property of anterior median spinal column is a valuable measure for reducing load-sharing of posterior instrument.