[Three-dimensional finite element investigation of lateral mass screw fixation and transarticular screw fixation in lower cervical spine].
OBJECTIVE
To establish sophisticated three-dimensional finite element model of the lower cervical spine and reconstruct lower cervical model by different fixation systems after three-column injury, and to research the stress distribution of the internal fixation reconstructed by different techniques.


METHODS
The CT scan deta were obtained from a 27-year-old normal male volunteer. Mimics 10.01, Geomagic Studio10.0, HyperMesh10.0, and Abaqus 6.9.1 softwares were used to obtain the intact model (C3-7), the model after three-column injury, and the models of reconstructing the lower cervical spine after three-column injury through different fixation systems, namely lateral mass screw fixation (LSF) and transarticular screw fixation (TSF). The skull load of 75 N and torsion preload of 1.0 N*m were simulated on the surface of C3. Under conditions of flexion, extension, lateral bending, and rotation, the Von Mises stress distribution regularity of internal fixation system was evaluated.


RESULTS
The intact model of C3-7 was successfully established, which consisted of 177 944 elements and 35 668 nodes. The results of the biomechanic study agreed well with the available cadaveric experimental data, suggesting that they were accord with normal human body parameters and could be used in the experimental research. The finite element models of the lower cervical spine reconstruction after three-column injury were established. The stress concentrated on the connection between rod and screw in LSF and on the middle part of screw in TSF. The peak values of Von Mises stress in TSF were higher than those in LSF under all conditions.


CONCLUSIONS
For the reconstruction of lower cervical spine, TSF has higher risk of screw breakage than LSF.
Department of Orthopaedics, Zhujiang Hospital, Southern Medical University, Guangzhou Guangdong 510282, PR China.
Yang
Y
Duan
Anmin
A
Jin
Hui
H
Zhang
Shaoxiong
S
Min
Konghe
K
Hu
D000328:Adult; D001696:Biomechanical Phenomena; D001863:Bone Screws; D002574:Cervical Vertebrae / Q000293:injuries / Q000601:surgery*; D020342:Finite Element Analysis; D005593:Fracture Fixation, Internal / Q000295:instrumentation* / Q000379:methods*; D006801:Humans; D021621:Imaging, Three-Dimensional; D016268:Internal Fixators; D008297:Male