Abstract:

Objective　To evaluate the transoral screw pull-out srength on C2 of transoralpharyngeal atlantoaxial reduction plate (TARP).　Methods　Six fresh spine specimens involving C1 and C2 (12 sides) were designed to compare screw pull-out strength  of C1 and C2. C1 screw was implanted into the lateral mass, while C2 screw was separately implanted into pedicle, vertebrae and articular process, and then the pull-out strength was tested and compared.　Results　There were no statistical difference of the screw pull-out strength between C1 lateral mass screw（546.45±85.07 N）and C2 pedicle screw（593.14±97.77 N），however, C1 lateral mass screw was stronger than C2 vertebrae screw and C2 screw underneath the articular process. The pull-out strength of C2 articular process screw（469.94±73.32N）was stronger than that of C2 vertebrae screw（395.15±75.07 N）. Conclusions: Experimentally, screw fixation transoral approach to C2 pedicle and C2 articular process of TARP is strong and safe.

Key words: Axis;　Screw;　Pull-out strength；　Biomechanics