The Basic And Applied Research Of Internal Fixation On Axis Using Posterior Screw-Rod System

The craniovertebral arthrodesis / atlantoaxial fixation and fusion proceduce are major methods for the upper spine disease. The goals of surgical management are to provide neural decompression , restoration of occipitocervical spinal alignment , and stabilization of unstable segments to allow for successful osseous fusion. At present,the rigid short segment fixation methods using screw are often focused on the location of C2 pedicle and isthmus .As a transitional vertebrae,the structure of Axis is so special that the transverse foramen varies obviously because of the variation of the vertebral artery course. Therefore ,both secureity of surgery and biomechanical stability of the fixational segment surroundings will be the further research objective .On the other hand , there isn't any nationalized posterior polyaxial screw and rod fixation system for upper cervical spine for clinical application as we know.So the following studies were designed .PartⅠAnatomic and Imaging Study1. Clinical anatomic study of the C-2 pedical and isthmusObjective. To make sure of the locations of the C-2 pedical isthmus for clinical application of C-2 fixation. Methods. 30 dry C-2 vertebrae and 10 dry C-3 vertebrae were observed and compared focusing on the structure surrounding transverse foramen . The projection coordinate of C-2 pedicle axis on the dorsal of inferior articular processs was conformed. Results .The outlook of inferior structure of C-2 vertebrae was similar with the inferior structure of C-3 vertebrae. Compared with the superior structure of C-3 vertebrae , the superior articular processs of C-2 moved inferolaterally to odontoid processs ,then the isthmus between superior and inferior articular processs was elongated to the frontage,which exhihited a lateral-medial 11.1±2.38o angle. The projection of C-2 pedicle axis, which exhihited a lateral-medial 42.6±4.90o angle ,was intersected with superior edge of superior articular peocess,the point of intersection was located away 1.65~1.10mm from the midpoint of superior edge of superior articular peocess. Conclusions . The structure of C2 between superior and inferior articular processes is pediculoisthmic components , which superior flat aspect is isthmus .The pedicle draped by isthmus is a hemitubular structure projecting posteromedially to the transverse foramen and connecting the inferior articular processs to the vertebral body. If the superior articular process of C2 was drawed to the location of comparative lower cervical vertebrae process ,the structures of both C2 pedical and isthmus were...