| Background:Aiming at the characteristics of weak tension and poor stability of single-segment common C2 pedicle in the treatment of Hangman’s fracture,the three-dimensional finite element method was used to explore the biomechanical performance difference between the new fixation method and the traditional treatment.Objectives:To study the biomechanical properties of three posterior single-segment internal fixation methods for type II Hangman fractures,and to explore the value of the new internal fixation system in its treatment.Methods:Thin-section spiral computed tomography(0.5mm)was performed on C0 to C3 region of cervical vertebra in a healthy male volunteer.After a three-dimensional hexahedral FE model of the normal upper cervical spine was established by software(Mimics10.01,Geomagics 2012 and Abaqus6.12),the finite element model of intact was verified with availablity.Next the grid strength was weakened to establish type II Hangman fractures and then establish three finite element internal fixation models:Model A:Hangman fracture+common pedicle screws model,Model B:Hangman fracture+new pedicle screws model,Model C:Hangman fracture+new pedicle screws+“Ω”transverse model.The range of motion(ROM),the stress of the implanted screw and the maximum extraction force of the each model under different working conditions was compared.Results:(1)The ROM of each segment of C0-3 under different working conditions is smaller than the normal model,and the largest difference is in the rotation direction of C2-3,which is increased by 0.6°,0.8 °and 0.8 °in the three internal fixation modes.There was no statistically significant difference in ROM between the three internal fixation models and the normal model(P>0.5);(2)Model C and Model B have approximately the same three-dimensional mobility of the cervical spine in flexion + extension,lateral bending(left + right),and rotation(left+ right),with minimal difference(P>0.5);(3)Compared with the Hangman fracture model,the three internal fixation models have no significant abnormalities in the flexion,extension,scoliosis and torsion directions of C0-1 and C1-2(P>0.05);on the C2-3,internal fixation model A of the stability of flexion + extension,scoliosis(left + right),and rotation(left + right)were increased compared with the fracture model: 38.45%,28.69%,12.01%,and the stability of the internal fixation model B increased compared with the fracture model: 34.55%,26.95%,4.19%,;and the stability of the internal fixation model C increased compared with the fracture model: 34.53%,26.95%,4.18%,and it can be seen that the mobility of the three internal fixation models on C2-3 is quite different from that of the Hangman fracture model(P<0.05);(4)The order of the maximum stress of the three groups of internal fixation implants in each working condition is as follows: Group A> Group B> Group C,and the screw stress concentration point is in the middle of the screw.The three internal fixation models of the difference in maximum stress is statistically significant by tatistical analysis(P<0.05).Conclusions:Hangman fracture+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 and Type IIa Hangman fracture internal fixation. |
