三种后路单节段固定方式治疗Ⅱ型Hangman骨折的生物力学性能

Biomechanical properties of three types of posterior single-segment fixation for type Ⅱ Hangman’s fracture

背景:单节段普通C2椎弓根钉在治疗Hangman骨折时存在拉力较弱、双枚螺钉孤立固定稳定性差的特点。目的:应用三维有限元方法分析3种后路单节段内固定方式治疗Ⅱ型Hangman骨折的生物力学性能,探讨新型内固定系统在治疗Ⅱ型Hangman骨折中的应用价值。方法:通过CT扫描获取1例健康成年男性上颈椎的影像学数据资料,利用Mimics 10.01、Abaqus 6.12等软件,建立正常的上颈椎(C0-3)的三维有限元模型并行有效性验证。基于有效性验证的基础上,首先建立Ⅱ型Hangman骨折模型,然后建立3种内固定模型:模型A:普通椎弓根螺钉内固定模型;模型B:新型双螺纹中空椎弓根螺钉内固定模型;模型C:新型双螺纹中空万向椎弓根螺钉+“Ω”形横连内固定模型,比较各模型在不同工况下的三维活动度和螺钉所受应力情况。结果与结论:①3种内固定方式下C0-3各节段在不同工况下的三维活动度与正常模型相差较小,相差最大的在C2-3扭转方向上,模型A、B、C较正常模型分别增大了0.6°、0.8°及0.8°,且3种内固定模型与正常模型之间三维活动度相比差异无显著性意义(P>0.05);②3组内固定植入物各工况下最大应力的大小顺序均为:A组>B组>C组,且螺钉应力集中点在骨折线部位,经统计学分析3种内固定模型的最大应力差异有显著性意义(P<0.05);③提示新型双螺纹中空万向椎弓根螺钉+“Ω”形横连内固定方式具有更优良的抗疲劳特性,且能最大程度地保留颈椎生理活动度,是一种可用于治疗Ⅱ型Hangman骨折的内固定方式。

BACKGROUND:Single-segment common C2 pedicle screw has the characteristics of weak tension and poor stability of isolated fixation with two screws in the treatment of Hangman’s fracture.OBJECTIVE:To analyze the biomechanical properties of three posterior single-segment internal fixation methods for type II Hangman’s fractures with threedimensional finite element method,and to explore the value of the new internal fixation system in the treatment of type II Hangman’s fractures.METHODS:The imaging data of a healthy adult male upper cervical spine were obtained by CT scanning.A three-dimensional finite element model of the normal upper cervical spine(C0-3)was established by software(Mimics 10.01 and Abaqus 6.12),and its availability was verified.Based on the availability verification,the model of type II Hangman’s fracture was established,and then three kinds of internal fixation models were established:Model A:common pedicle screws model,Model B:new pedicle screws model,Model C:new pedicle screws+“Ω”transverse model.The range of motion and the stress of the implanted screw of the each model under different working conditions were compared.RESULTS AND CONCLUSION:(1)The range of motion of each segment of C0-3 under different working conditions was smaller than the normal model,and the largest difference was in the rotation direction of C2-3,which was increased by 0.6°,0.8°and 0.8°in the three internal fixation models A,B,and C.There was no statistically significant difference in range of motion between the three internal fixation models and the normal model(P>0.05).(2)The order of the maximum stress of the three groups of internal fixation implants in each working condition was as follows:Group A>Group B>Group C,and the screw stress concentration point was in the middle of the screw.The three internal fixation models of the difference in maximum stress were statistically significant by statistical analysis(P<0.05).(3)New pedicle screws+“Ω”transverse internal fixation has better anti-fatigue characteristics and could retain the physiological activity of the cervical spine to the greatest extent.It is a well type that can be used to treat type II Hangman’s fracture internal fixation.