Three Dimensional Finite Element Analysis Of Two Different Internal Fixation Methods For Hangman Fracture

Objetive:Using three dimensional finite element technology to analyze the biomechanical properties of two different internal fixation methods for Levine-Edwards type? Hangman fracture.Method:(1).Using three dimensional finite element modeling software and thin-slice CT scan data of adult's normal upper cervical vertebra to establish the model of adult's normal upper cervical vertebra(c0-c3)and verifying the effectiveness of the model.(2).On the basis of the model of adult's normal upper cervical vertebra(C0-C3),establishing the model of Pure C2 pedicle screw fixation for Levine-Edwards type ?Hangman fractures(traditional internal fixation group)and the model of C2 pedicle screw with a cross in the shape of ? for Levine-Edwards type ? Hangman fractures(new internal fixation group),respectively.Measuring the motion of upper cervical vertebra ? the maximum stress of pedicle screw ?the axial pulling force of pedicle screw of two different internal fixation groups under different working conditions,comparing and analysising the biomechanical properties of the two different internal fixation for Levine-Edwards type ? Hangman fracture.Results:(1).The three dimensional finite element model of adult's normal upper cervicalvertebra has been successfully established and verified,which can be used for the biomechanical analysis of upper cervical vertebra.(2).Upper cervical range of motion:Under different operating conditions,the mobility of each segment of the upper cervical spine in the traditional and new internal fixation groups is the same.(3).The maximum stress of pedicle screw:In the direction of forward flexion?backward extension?lateral flexion(left + right)? rotation(left + right),the maximum stress of pedicle screw in the new internal fixation group decreased by 7.02%,6.09%,0.32% and0.40%,respectively,compared with the traditional internal fixation group.(4).The axial pull-out force of pedicle screw:In the direction of forward flexion ?backward extension?lateral flexion(left + right),the axial pull-out force of pedicle screw in the new internal fixation group decreased by 27.2%,18.6% and 1.1%,respectively.Compared with the traditional internal fixation group,the axial pull-out force of pedicle screws of the new internal fixation group in rotation(left + right)is basically the same with that of the traditional internal fixation group.Conclusion:(1).The influence of the new internal fixation method:C2 pedicle screw with a cross in the shape of ? on the upper cervical physiological activity is similar to that of the traditional internal fixation,which are all able to retain the maximum motion of the upper cervical spine.(2).Compared with the traditional internal fixation method,the new internal fixation method can reduce the maximum stress of pedicle screw ? improve the anti-fatigue performance of screw,and reduce the risk of screw breakage.(3).Compared with the traditional internal fixation method,the new internal fixation method can reduce the axial pulling force of the pedicle screw?reduce the risk of screw unnailing,and it is more conducive to maintaining the stability of the fracture,which is amore ideal internal fixation for Levine-Edwards type?Hangman fracture.