Abstract: Objective    To explore the biomechanical characteristics of different modes of new horizontal screw-screw crosslink (hS-S CL) in C1-C2 pedicle screw-rod fixation (C1-C2 PSR) by three-dimensional finite element, which provided theoretical basis for clinical selection of the optimal hS-S CL. Methods The atlantoaxial finite element models were established respectively: the normal group was group A , the unstable group was group B, C1-C2PSR group was C, C1-C2PSR+ upper/lower hS-SCL , C1-C2PSR+ dS-SCL and C1-C2PSR+xS-SCL groups were D-H group respectively. The Range of motion (ROM) and Von Miss Stresses in flexion and extension, lateral flexion and rotation of the normal group, the unstable group and the six kinds of internal fixation groups were calculated by applying 1.5 Nm torque to each finite element model, and the stress cloud was extracted.    Results   ①Under the 6 working conditions, the ROM in the normal group and the internal fixation group was significantly lower than that in the unstable group. In flexion and extension state: the ROM of all internal fixation groups was basically the same. Under the conditions of lateral flexion and rotation, compared with that in the without crosslink group, the ROM in the D-H group was reduced by 34-44% and 79%, 36-46% and 76-80%, 39-47% and 78-79%, 40-46% and 78-79%, 49-50% and 91-93%, respectively,  and the ROM in the H group decreased most obviously in the rotation state. ② The stress peak of internal plant model: the maximum stress of the crosslink group was generally smaller than that of the non-crosslink group, and the stress peak value of all the internal fixation groups was the lowest when the extension was carried out. ③ The stress cloud of internal plants showed that the stress distribution areas of the internal fixation in the crosslink fixation group were basically the same, and there was no obvious stress concentration phenomenon in the internal fixation, and the main stress distribution areas were the screw root and bone joint, and the crosslink ends were the screw tail groove or the joint rod joint.     Conclusions    The new hS-S CL in posterior C1-C2 pedicle screw-rod fixation has the strongest anti-rotation stability, but the stress distribution at both ends of the transverse connection is obvious, which may be prone to transverse fracture.

Key words: Crosslink,  ,  , Posterior,  ,  , Atlantoaxial,  ,  , Three-dimensional finite element