计算机辅助的腰椎单节段融合后邻近节段的力学变化研究

Computer assisted analysis in adjacent segment disease after singe -level lumbar fusion

目的利用有限元分析方法，建立L2-L5多节段腰椎有限元模型，模拟L3-L4后路单节段经椎弓根钉棒固定手术，观察融合后邻近节段L2-L3和M—L5椎间盘的应力变化。方法建立A、B、C3组L2-L5的有限元模型。A组：L0-L4末手术尉定，无椎间盘退变；B组：L3—14手术固定，术前邻近节段无退变；C组：L3-14手术固定组，术前邻近节段已有退变；在0．3、0．5、1．0、2．0MPa4种轴向压力作下，比较各组作为邻近节段的L2-L3椎间盘和L4-L5椎间盘的应力变化。结果得出A组、B组、C组的L2-L3椎间盘和L4-L5椎间盘最大主应力平均值，经统计学处理结果，L2-L3椎间盘的A组和B组之间在4种受力情况下，应力都无显著性差异，L2-L3椎间盘的A组和C组间及L4-L5椎间盘各组间在4种受力情况下，应力都有显著性差异。结论单节段后路腰椎固定融合不足引起邻近节段退变的重要原因；但邻近节段的椎间盘如果已经发生退变，则可能是影响形成的重要因素。

Objective To evlutate the biolneehanieal alterations occuring at the adjacent segment after posterior intertransverse fusion in L3 - L4 segment with the finite element analysis. Methods Three 3D finite element models of the human L2 - L5 segments of Group A, Group B, Group C were established. Group A： uninstrumented fusions, with healthy discs of adjacent segment（ L2 -L3, L4 -L5） , Group B： posterior intertransverse fusion in L3 -L4 segment with healthy discs, GroupC： posterior intertransverse fusion in L3 - L4 segment, with degenerated discs of adjacent segment （ L2 - L3, L4 - L5 ） . The stress on the discs of adjacent segment（ L2 - L3, L4 - L5 ） under axial pressure（0.3 MPa, 0. 5 MPa, 1.0 MPa, 2.0 MPa） was analysed. Results The stress on the disc L2 - L3 was no statistically significant difficenee between Group A and Group B, but there was statistically significant difficence between Group A and Group C; The stress on the disc L3 - L4 was statistically significant difficence anong Group A, Group B, Group C. Conclusion There is no increased risk of adjacent segment disease （ASD） after instrumented posterolateral fusions. An already degenerated disc of adjacent segment maybe be a significant risk factor for ASD.