椎体间融合器的单节段植入对腰椎多节段椎弓根固定装置中螺钉应力的影响

 【目的】 通过体外生物力学实验评价椎体间融合器（cage）的单节段植入对腰椎多节段固定装置中椎弓根钉应力的影响。【方法】10具牛新鲜尸体腰骶椎标本L2-S1用于实验。经后方行L3-L4、L4-L5和L5-L6椎板和椎间盘部分切除，用椎弓根钉和一对碳纤维cage行以下3种三节段固定：①无cage植入；②L4-L5cage植入；③L5-L6 cage植入。每组分别行载荷量为600N的轴向压缩试验，记录各节段椎弓根钉的折曲应变量，并加以比较。【结果】在无cage植入组中，L3和L6椎弓根钉的折曲应变量显著高于L4和L5；在L4-L5 cage植入组中，L4和L5椎弓根钉的折曲应变量显著低于L3和L6；在L5-L6cage植入组中，L5和L6椎弓根钉的折曲应变量显著低于L3和L4。【结论】多节段椎弓根固定结构可导致上下两端椎弓根钉的应力增大；Cage的植入可降低上下相邻椎弓根钉的应力，但使相邻以远的椎弓根钉的应力增大。

Effect of One-segmental Interbody Cage Insertion on Screws Strain in Lumbar Multi-segmental Pedicle Fixation Construct

Objective] To evaluate the effect of one-segmental cage insertion on screws strain in lumbar multi-segmental pedicle fixation construct.Methods] Ten fresh calf spines(L2-S1)were used.After L3-L4,L4-L5,L5-L6 laminectomy and partial diskectomy,three-segmental pedicle screw fixations with and without two carbon cage insertion were performed as follow:(1)no cage insertion,(2)L4-L5 cage insertion,and(3)L5-L6 cage insertion.Biomechanical testing was undergone under 600 N compressive loading mode.Screw bending strains at every vertebra were measured and compared.Results] In no cage insertion group,L3 and L6 screws bending strain were significantly higher than L4 and L5;In L4-L5 cage insertion group,L4 and L5 screws bending strain were markedly lower than L3 and L6;In L5-L6 cage insertion group,screws strain at L5 and L6 were significantly lower than at L3 and L4.Conclusion]Multi-segmental pedicle fixation construct may lead to high strain at the cranial and caudal screws.Cage insertion can decrease adjacent up and down screws strain,but increase the other screws strain.