胸椎旁路法植入椎弓根螺钉的力学实验研究

Biomechanics study on pull-out strength of thoracic extrapedicular screw

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。

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. Fie,suits 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 pull-out 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）. Oonclusion The extra-pedicular technique is feasible in biomechanics.