两种不同C2椎弓根螺钉加“Ω”形横连治疗Ⅱ型Hangman骨折的生物力学研究

Biomechanical study of two different pedicle screws combining "Ω" transverse connection in the treatment of type Ⅱ Hangman fracture

目的:探讨普通C2椎弓根螺钉和双螺纹中空万向螺钉(新型)加“Ω”形横连固定Ⅱ型Hangman骨折的生物力学特点.方法:选择1名健康成年男性志愿者对其颈椎C0-3椎节进行CT扫描,获得CT图像原始数据.利用Mimics 10.01等软件建立正常颈椎C0-3椎节三维有限元模型(包含椎间盘、韧带等组织),并进行有效性验证.在已验证的有限元模型的基础上,分别建立以下模型:Hangman骨折模型(Levine-EdwardsⅡ型);Hangman骨折+普通C2椎弓根螺钉+“Ω”横连模型;Hangman骨折+新型C2椎弓根螺钉+“Ω”横连模型;比较各模型在不同工况(屈伸、侧屈、旋转)下的三维活动范围(ROM)及置入螺钉所受应力情况,运用秩和检验方法进行统计学分析.结果:生理载荷下Hangman骨折模型在屈伸、侧屈、扭转方向上的ROM较正常颈椎模型明显增大,集中表现在C2-3椎节,各工况下分别增加3.89°、5.65°、2.10°;内固定模型不同椎节ROM较骨折模型显著减小,其中两内固定模型之间的ROM差别无统计学意义(P>0.05).不同工况下,内固定模型中螺钉均在后伸时所受应力最大,分别为403.3MPa、370.4MPa,应力主要集中在螺钉通过骨折线的部分,而新型C2椎弓根螺钉在各工况下最大应力均小于普通C2椎弓根螺钉(P<0.05).结论:两种不同C2椎弓根螺钉(普通和新型)加“Ω”横连固定装置在最大限度保留颈椎生理性活动的同时,均能有效恢复Ⅱ型Hangman骨折颈椎稳定性;“Ω”横连下新型C2椎弓根螺钉较普通C2椎弓根螺钉具有更好的抗疲劳性能.

Objectives:To investigate the biomechanical characteristics of two different C2 pedicle screws(common and new)combining"Ω"transverse connection for typeⅡHangman fractures.Methods:C0-3 vertebrae of a healthy male adult were scaned by CT,and the original data of CT images were obtained.The finite element model(including intervertebral disc,ligament and other tissues)of normal C0-3 was established by Mimics10.01 et al,and the validity of the model was verified.On the basis of the verified finite element model,the following models were established:Hangman fracture model,Hangman fracture+common C2 pedicle screws+"Ω"transverse model,Hangman fracture+new C2 pedicle screws+"Ω"transverse model.Range of motion(ROM)and implant stress of each model in different working conditions were compared.Results:Under physiological load,the ROM of Hangman fracture model in flexion,extension,lateral flexion and torsion was significantly higher than that of normal cervical spine model,mainly in C2-3,which increased by 3.89°,5.65°and 2.10°,and the ROM of C2-3 of two internal fixation models was significantly lower than that of fracture model.The ROM between two internal fixation models was similar.The stress of screws in two internal fixation models reached the largest when they extended back,which was 403.3MPa and 370.4MPa respectively,and the stress mainly concentrated in the part of the screws passing through the fracture line.The maximum stress of the new C2 pedicle screws was lower than that of the common C2 pedicle screws in all working conditions.Conclusions:Two different C2 pedicle screws(common and new)combining"Ω"transverse connection can effectively restore the stability of cervical vertebra while retaining the physiological activity of cervical vertebra.The new C2 pedicle screws had better anti-fatigue effect than the common C2 pedicle screws.