椎弓根皮质劈裂经伤椎置钉内固定的生物力学研究

Biomechanical Study of the Influence on the Stability for the Pedicle Screws Fixation by Injured Vertebral Screw in the Pedicle Cortex Perforation

目的 探讨椎弓根皮质劈裂对椎体骨折内固定稳定性生物力学的影响,通过生物力学测试对椎弓根皮质劈裂后不同伤椎置钉方式的螺钉内固定稳定性进行评价.方法 取新鲜小牛胸腰段（T11～L3）标本36具,随机分为4组,分别为A、B、C、D组.A组为椎弓根皮质完整组,B、C、D组均为椎弓根皮质破裂组.4组标本于L1椎体上制作单椎体压缩骨折模型,然后对B、C、D3组T12胸椎任意一侧椎弓根行外侧1/4切除,作为椎体压缩骨折合并椎弓根皮质劈裂模型.A、B组均为四钉组,C组为经与劈裂椎弓根同侧的伤椎椎弓根置入一钉组（5钉组）;D组为经伤椎置入两钉组（6钉组）.各组标本行相应螺钉固定,然后在HY-3080微机控制电子万能材料试验机上以500N的载荷对4组标本均进行10000次疲劳试验,分别测量疲劳试验后4组标本的轴向压缩刚度、T12椎体椎弓根劈裂侧螺钉拔出力的大小及4个方向的活动范围,比较4组的差异.结果 与B组比较,A、C、D3组的模型刚度和最大拔出力均高于B组（P＜0.05）;B组模型在屈伸、侧弯4个方向的运动范围（ROM）均明显高于A、C、D3组（P＜0.05）.C、D两组模型刚度大于A组（P＜0.05）;C、D两组模型在屈伸、侧弯4个方向的运动范围（ROM）及螺钉最大拔出力均低于A组（P＜0.05）.C组各个检测指标与D组比较差异均无统计学意义（P＞0.05）.结论 椎弓根劈裂将严重影响椎体骨折内固定的稳定性,经伤椎置钉可以明显提高劈裂椎弓根内固定的稳定性.

Objective Explore the impact on stability of the vertebral body fracture when fixing the pedicle screw internal fixation with the pedicle cortex perforation.By biomechanical testing to evaluate the internal fixation stability by different way injured vertebra transpedicular screw when when the pedicle cortex perforation.Methods Totally 36 of fresh thoracic and lumbar vertebrae samples of calf （T11-L3）,were randomly divided into four groups,A,B,C and D.The compression fracture of the single vertebrae was modeled in L1 of the four groups.Then the samples of group B,C and D were removed a quarter of either side of lateral T12 thoracic pedicle,which was considered as the pedicle cortex perforation model.The groups of A and B were placed four screws ; group C with splitting pedicle ipsilateral in the injured vertebral pedicle were placed five screws; group D with splitting pedicle ipsilateral in the injured vertebral pedicle were placed six screws.After 10000 times by 500N load on the HY-3080 almighty material test machine.The drawing force of the screw and the stability of injured thoracolumbar vertebrae were measured and the differences in every group were compared.Results Compared with group B,the stiffness and the drawing force in the other three groups were higher than in group B （P ＜ 0.05）,the group of B in four directions （ROM） were significantly higher than those of the other three groups （P ＜ 0.05）.The stiffness and the drawing force in groups of C and D were greater than group A （P ＜ 0.05） ; two groups of C and D in the four directions （ROM） were lower than group A （P ＜ 0.05）.Every testing index in group C had no statistically significant difference with group D （P ＞ 0.05）.Conclusion The pedicle cortex perforation will seriously affect the stability of the fractured vertebral body.The injured vertebra transpedicular screw can increase the internal fixation stability.