Design And Biomechanical Evaluation Of Occipital Cervical Fusion Instrument

The disease between the occipital and cervical spinal includes rheumatoid arthritis ,atlantoaxial, discloation, trauma, tumor, and deficit of intial et al .The surgical management has envolved rapidly along with the deeper 梪nderstanding of occipital-cervical and the development of the imageology and biomechanics Athough several different surgical techniques using steel, screw through later mass or external fixation(Halo devices) have been developed to fix the occipital-cervical, there are still some problems with stability. Using the plate-stick system can increase thestability and prepare for the next operation The occipital lies behind the skull. The screw can fix in the occipital,but the thick of the occipital must be cared. The deeper research in the occipital morphology should be done before operation. In the cervical spine ,three-colunn fixation using transpedicular screw fixation offers some advanges in that fixed segments could be eliminated while it provides stability greater than that of other posterior instrumentation .Using the stick-plate system is stronger than steel system. .In order to develop this new technique, the study of transpedicular screw fixation of upper cervical spine has been explored. The study of this subject includes the following six aspects: 1. The applied anatomy of occipital thickness and morphology: In this section, occipital bone (10cm>< 5cm) morphologic characteristics were evaluated to determine the postion of the greatest bone thickness for safe and effective internal fixation. The results III P show:(l)The distribution of the occipital thickness is irregular, the external occipital protuberance is the thickest place and the region of cerebellar fossa is the thinnest place.(2)The body surface projection of confluens sinnum was concorded with external occipital protuberance.Most of left tranverse sinus were distributed slightly lower to the superior nuchal line.Occipital is mainly composed of compact cortical bone. (2)The applied anatomy of upper cervical pedicle: In this section ,the three-dimension quantitative anatomy of upper cervical pedicle was determined.The results show:the pedicles of the upper cervical spine are wide enough to aspect 3.0-4.0mm screw. The depth of insertion of screw is 25mm. (3)The research of the occipital-cervical angle measure: During the operation ,we should make the angle between the occipital and the axial in 0-300.We could bend the stick in ~l4.4o according to the cervical spine. (4)Design of the device of plate-stick transpedicular screw fixation for occipital-cervical fusion: The device was designed based on the results of the anatomy of occipital,upper cervical, and O-C2 angle.This system consist of plate- stick, U transpedieular screws, screw nuts, cortical screw. (5)Biomechanical Evaluation: The biomechanical stability of plate-stick system is stronger than the plate system under flexion loading,extending loading, lateral bending loading. (6)The clinical application: From March 1999, 2 patients with atlas metastatic tumors,received fusion through plate system.One patient has cut away the tumor through anterior entrance after the postior fusion. Using the plate system for fusion i...