The Study About Implanting Pedicle Screws In Lower Cervical Vertebra That Guided By The Computerized Three-demensional Reconstruction And Visualization Technology

Objective:Pedicle screws fixed in lower cervical vertebra had been confirmed to have significant mechanical stability,but this method had high risk because of injuries of spinal cord and vascellum around pedicle.To solve the challenge,this study will establish the method of multiple slice computerized tomography(MSCT) scan,three-dimensional(3D) reconstruction assisting lower cervical transpedicular fixation,and measurement program of referenced parameters about lower cervical pedicle screws implant.Based on above experiments,MSCT 3D reconstruction technique was used to assist pedicle screws placement in spinal surgery,clinic experience,therapeutic effect and limitation were recorded and analyzed as well. According to the shortage of the method,combined with the demand on intraoperative 3D image guide,a scheme of spinal surgery simulation system based on 2D/3D image registration was designed to deal with those limitations and accomplish intraoperative 3D image guide.Material and methods:For the pedicle screw insertion in lower cervical vertebra,MSCT scan was performed in 8 cadaveric cervical spines,and VR (volume rending) and MPR(multiplannar reconstruction) technique,which were incorporated within MSCT 3D reconstruction,were studied and used to measure the parameter for guiding pedicle screw insertion.Then all parameters were analyzed by statistic methods,aiming at gaining the parameters of morphologic characteristics in lower cervical spine.When established the method,MSCT 3D reconstruction technique was supplied in vivo.Diagnosis,preoperative individualized design, measurement and postoperative assessment were performed in 9 patients with multilevel degenerative stenosis combining with traumatic instability of lower cervical spine,and cervical pedicle screw fixation(44 pedicle screws) and double-door laminoplasty(42 volumes) had been finished under the plan.According to the analysis of clinic results in first section,the deficiency and limitation of this method was found as well,including the difficulty of data translation and lower ability of real time monitoring.To deal with the limitation and accomplish intraoperative 3D image guide,the simulation system for spine surgery based on 2D/3D image registration,associated with advantages of fluoroscopy and MSCT,was schemed initially,and secondly correlative techniques were study,then achieving the further valuable plans eventually.Results:In vitro,VR and MPR reconstruction techniques of MSCT can satisfy to finish the preoperative plan for transpedicular fixation in cervical vertebra,and the parameters of entry point and angles about pedicle screw insertion can be gained by measurement in axial,sagittal and coronal MPR reconstruction.When the technique was applied in vivo,grade 1 of perforation rate by Richter's method was 72.7% (32/44) in patients of lower cervical pedicle screw fixation,Grade 2 was 27.3% (12/44),and no cases of grade 3 and iatrogenic damage occurred.By using this method in vitro and vivo,some limitations had been found,which included lower abilities of translation from measurement data,and accuracy of 2D imaging monitor from intraoperative fluoroscopy.To deal with limitation of this method,a visualized spinal surgery simulation system has been designed and studied,and the system be based on microcomputer,the platform of Windows XP2,X-ray 2D and MSCT 3D images registration as key technology,the development envioronment on Visual studio6.0 and the program design combined C++ language with VTK/ITK and OpenGL software packages.Conclusions:Through MSCT 3D reconstruction technique assisting lower cervical pedicle screw fixation,preoperative anatomic structural details,reasonable design and individual datum measurement can be obtained.According to the information guiding the procedure,surgeons will not only depend on excellent handling and experiences.The rates of successful screw placement can be improved significantly,and simultaneouly operation times can be shortened.For cases of pedicle mutation,obturation or minor,the method will present more significant advantages.However,because major objective of MSCT 3D reconstruction technique is to assist diagnosis,when used in operation plan,it still has some limitation in lower abilities such as interaction and direction,translation from measurement data,and accuracy of 2D imaging monitor from intraoperative fluoroscopy.So combined with advantages of fluoroscopy and MSCT,to design and establish a visualized spinal surgery simulation system may be a solution.Depending on the simulation system based on 2D/3D medical image registration,intraoperative guide,convenient plan, repeated simulated manipulation and interactive education will be performed in future days.