The Method To Calculate The Sagittal Angle And Depth Of Lumbar Pedicle Screw By Using Intraoperative C-arm Anteroposterior Position Fluoroscopy

Objectives:To explore the method of assessing the sagittal angle and depth of pedicle screw by only using intraoperative C-arm anteroposterior position fluoroscopy instead of AP and lateral position,which can reduce the operation time,the X-ray exposure dose and the risk of contaminating sterilized area.Methods:Establish the space rectangular coordinate system based on the basement of the pedicle screw.And we deduced the formula for calculating the sagittal angles and sagittal depths of the screws.From March 2017 to February 2019,20 patients with lumbar degenerative diseases which received the posterior pedicle screw fixation and fusion in Qilu hospital orthopedic ward were randomly selected,with 86 pedicle screws placed.Calculate the sagittal angles(? ? ap)and depths(Dap)using the parameters of anteroposterior position images according to the formula.Measure the sagittal angles(? ? 1)and depths(Dlr)from the lateral position images.The equivalence of the two methods for measuring data was analyzed.Results:The differences of ?? a ap and ?? 1 were-3.728°-4.778?,mean difference was(0:332±1.613)°.In the two groups,the double single-side paired t test was conducted with the equivalent boundary value of 1 °,demonstrating the two methods are equivalent(P1?P2<0.05).The 90%confidence interval of the difference between the two groups is(0.041°,0.623°).The differences of Dap and Dlr were,0.426cm?0.134cm,mean difference was-0.034±0.144cm.In the two groups,the double single-side paired t test was conducted with the equivalent boundary value of 0.1cm,demonstrating the two methods are equivalent(P1?P2<0.05).The 90%confidence interval of the difference between the two groups is(-0.060cm,-0.008cm).Conclusion:This experiment has proved that,the sagittal angle of pedicle screws can be calculated accurately according to the anteroposterior position fluoroscopy.With the lateral image before operation,the pedicle screws can be simulated on lateral position fluoroscopy.Thus,the intraoperative C-arm anteroposterior position fluoroscopy can take the place of AP and lateral position fluoroscopy.In addition,the transverse angle of screw can be obtained through calculation,and the three-dimensional position of pedicle screw can be determined to better guide the operation of freehand screw placement.It is of high clinical value to increase the accuracy of the screw insertion and to reduce the risk of medical personnel X-ray exposure dose and the risk of contaminating sterile area.