胸椎旁路法植入椎弓根螺钉的力学实验研究

目的：研究在胸椎节段应用椎弓根旁路法植入椎弓根螺钉的力学可行性。方法：5副成人新鲜尸体胸椎（T1-8）, 分解为40个单一椎体标本，每一标本左右两侧分别使用经椎弓根入路法（n=40）和旁路法（n=40）植入螺钉，并进行螺钉沿椎体矢状轴拔出强度的力学测量，比较两种方法的拔出强度。结果：旁路法植入螺钉后出现两种情况A和B，A：19个椎体（47.5%），为螺钉经横突后沿椎弓根外壁固定至椎体；B：21个椎体（52.5%），为螺钉经椎弓根外侧皮质至椎体。旁路法中A植入螺钉的拔出强度为（827.01±260.00）N，旁路法中B植入螺钉的拔出强度为（954.25±254.00）N。结合A、B两种情况，旁路法中植入螺钉的平均拔出强度为（890.63±342.00）N，胸椎经椎弓根入路螺钉的拔出强度为（1 001.23±220.00）N，二者比较，旁路法螺钉的平均拔出强度较经椎弓根入路法螺钉的拔出强度降低11.04%，但差异无显著性（P>0.05）。结论：胸椎椎弓根旁路法植入椎弓根螺钉在力学上是可行的。

Biomechanics study on pull-out strength of thoracic extrapedicular screw

Objective To identify the biomechanical feasibility of the extra-pedicular technique for screw insertion in thoracic.Methods Five fresh adult cadaveric thoracic spine from T1 to T8 were harvested and divided into forty single vertebrae.Pedicle screw and extra-pedicular screw were inserted in each specimen respectively.Pull-out strength of pedicle screw and extra-pedicular screw through sagital axis of vertebral were measured and compared statistically.Results Two kinds of insertion result were obserbed in extra-pedicular group,A and B.A:(19 screws) were inserted through transverse into vertebrae directly;B: 21 screws were inserted into vertebrae through lateral cortex of pedicle.In extrape-dicular group,along the sagital axis,the mean pullout strength of A was(827.01±260.00) N,and the mean pull-out strength of B was(954.25±254.00) N.The mean pull-out strength of all screws in extra-pedicular group was(890.63±42.00) N,and the mean pull-out strength of screws in intrapedicular group was(1 001.23±220.00) N.Compared with pull-out strength of screws in intrapedicular group,the mean pull-out strength of all screws in extra-pedicular screw was decreased by 11.04%,the difference was no significant((P>0.05).)Conclusion The extra-pedicular technique is feasible in biomechanics.