枕颈后路短节段固定的交叉棒与平行棒固定方式生物力学稳定性比较

Comparison of Biomechanical Stability between Crossed Rod and Parallel Rod with C0-2 Posterior Fixation

目的:分别比较枕颈融合中两种内固定方式——枕骨髁Y形板+枢椎一侧椎板螺钉/另一侧椎弓根螺钉(A组)和枕骨髁Y形板+枢椎双侧椎弓根螺钉(B组)的交叉棒和平行棒的生物力学稳定性。方法:取6具新鲜人体尸体颈椎标本,完成完整状态的生物力学测量后,制备寰枢椎失稳模型,每一例标本均植入枕骨髁Y形板及枢椎一侧椎板螺钉、枢椎双侧椎弓根螺钉。按顺序分别测量枢椎一侧椎板螺钉/另一侧椎弓根螺钉平行棒固定(A1组)、枢椎一侧椎板螺钉/另一侧椎弓根螺钉交叉棒固定(A2组)、枢椎双侧椎弓根螺钉平行棒固定(B1组)和枢椎双侧椎弓根螺钉交叉棒固定(B2组)的屈伸、侧屈、旋转活动度。结果:与完整状态组相比较,A1、A2、B1、B2四种内固定组合在屈伸、侧屈、旋转六个方向上的稳定性均强于完整状态组,差异均有统计学意义(P<0.05);A1、A2、B1、B2组间比较在前屈/后伸、左/右侧屈方向上差异均无统计学意义(P>0.05);A1组的稳定性在左/右旋转上较A2、B1、B2三组差,差异有统计学意义(P<0.05);而A2、B1、B2组间比较在左/右旋转上差异无统计学意义(P>0.05)。结论:枕颈后路短节段固定时,应首选枢椎双侧椎弓根螺钉,当无法置入枢椎椎弓根螺钉时,应尽量选择条件相对允许的一侧置入椎弓根螺钉,另一侧使用椎板螺钉代替。此时,采用交叉棒的连接方式可获得同双侧椎弓根螺钉相似的固定强度。

Objective:To compare the biomechanical stability of the fixation technique for the crossed rod and parallel rod by occipital plate combined with C2 one side lamina screw/other side pedicle screw and occipital plate combined with C2 bilateral pedicle screws.Methods:Six fresh adult craniocervical specimens were used to test the biomechanical stability.Following intact state testing,each specimen was implanted with occipital plate,C2 lateral lamina screws and C2 bilateral pedicle screws.The specimens were then tested in the following sequence:group A1(occipital plate+C2 one side lamina screw/other side pedicle screw+parallel rod),group A2(occipital plate+C2 one side lamina screw/other side pedicle screw+crossed rod),group B1(occipital plate+C2 bilateral pedicle screws+parallel rod),and group B2(occipital plate+C2 bilateral pedicle screws+crossed rod).The ROM of the C0-2 segments were measured in flexion-extension,lateral bending,and axial rotation.Results:The four fixed modes significantly increased stability compared with both the intact group in flexion-extension,lateral bending,and axial rotation(P<0.05).There was no significant difference between the four internal fixd modes in flexion-extension and lateral flexion(P>0.05).In the rotation,the stability of group A1 was worser than the other three groups(P<0.05),and no significant difference among A2,B1 and B2 groups(P>0.05).Conclusion:When C0-2 fixation was required,C2 bilateral pedicle screws should be preferred.when C2 pedicle screws cannot be inserted,try to select the side with relatively allowable conditions to insert one pedicle screw,and use lamina screw to replace it on the other side.At this time,the fixation strength similar to that of C2 bilateral pedicle screws could be obtained by cross rod connection.