Objective To investigate the safe trajectory of the fixation of cervical lateral mass screw by anatomic study.Methods Twenty-eight cervical specimens (C_ 3-7 ) of human cadavers aged from 28 to 79 years were studied.The safe exit and entrance point of screw were studied.The transverse radiographs of C_ 3-6 vertebrae were taken and the angle between the parasagittal plane and the line connecting the entrance point of the lateral mass with the lateral limit of the transverse process foramen of C_ 3-6 measu...