Accuracy Study Of Preoperative Measurement Of Pedicle Screw Fixition For Thoracolumbar Vertebra On Virtual Surgery System

ObjectiveTo plan pedicle screw fixition preoperatively for thoracolumbar Vertebra on virtual surgery system,and to establish a method to measure the parameters of screw routine:To compare the the measured parameters of ideal screw routine with the data of practical measurement.Material and methods1.Plan of pedicle screw fixition preoperatively on virtual surgery system and measure the parameters of screw routine.1) CT scanning8 adult cadavers were scanned with 64-slice spiral CT(slice 0.5 mm) and the data were reserved as DICOM images.2) Three-dimensional reconstruction in vitual surgery systemThe data from CT were imported into the vitual surgery system,and the images were reconstucted with VR and MPR technology.Then three-dimensional model and two-dimensional changeable picture were displayed simultaneously.3) Planning and measuring ideal screw routineIn the spine model,two plane were displayed and then moved to the axial and sagittal position of pedicle(vertically).Besides,projective line of one plane were situated in axial line of pedicle in axial image,and projective line of the other plane were situated in axial line ofpedicle in sagittal image.At this time,the intersection line of the two plane was correctly axial line of pedicle,also as the ideal screw routine.Then the parameters of ideal screw routine were measured in the 2D images.The following parameters were included.The direction parameters of ideal screw routine: Angle of axial view(Aa),Angle of sagittal view(As);The coordinate parameters of ideal screw routine;Total Pedicle Length of axial view(TLa),Total Pedicle Length of sagittal view(TLs);The length parameters of ideal screw routine:X-direction Entrance(XE),Y-direction Entrence(YE).The radial parameters of pedicle:Pedicle Height(PH),Pedicle Width(PW),Pedicle Spongy Width(PSW).2.Practical measurement.in cadaversThe verteb was splited in transverse cross section of pedicle axial,the position of pedicle axial was directly exposured.Then the parameters of ideal screw routine corresponding to vitual measurement,were measured again,including Aa',As',TLa', XE',YE',PW' and PSW'.3.Statistics analysis of the data from virtual and practical measurement The data from from virtual and practical measurement was analyzed with paired-sample t test.Results1.In vitual surgery system,three-dimensional reconstruction,2D and 3D images corresponding presentation,image segmentation and assisted measurement,satisfied the request to plan and measure pedicle screw routine.2.There was no difference of the vitual measuring parameters of screw routine between bilateral pedicles at the same level(p＞0.05).There was no difference of the pratical measuring parameters of screw routine between bilateral pedicles at the same level(p＞0.05).And There was no difference between Tla and TLs from vitual measurement.3.After Statistics analysis,There was no difference of the parameters(Aa,As,TLa, TLs,YE,PW,PSW and PH) of screw routine between vitual and practical measurement(p＞0.05).There was little difference of the parameters XE of screw routine on T11 between vitual and practical measurement(p＞0.05).Conclusions1.Planing and measuring of ideal pedicle screw routine were accurate and direct.2D and 3D images corresponding presentation makes determining the pedicle axial easily and mistakelessly.2.The feasibility and accuracy of preoperational plan in vitual surgery systemwas confirmed in this experiment.That made foundation to widen application of the spinal simulation system.3.The tendency of the pratical measure of screw routine in this experiment exactly meet the report before.It indicated that pratical measurement was precise.