A Comparative Study Of CT Reconstruction For Preoperative Evaluation Of Safe C2 Pedicle Screws Placement

Objective:The purpose of this study was to compare morphometric parameters between the orthogonal transverse PIC width(TPW),oblique PIC width(OPW)and minimum PIC diameter(MPD)measured in multiplanar reconstruction CT images and to compare the evaluative performance of safe C2 pedicle screw placement between TPW,OPW,the definition of high-riding vertebral artery(HRVA)and MPD.We also aimed to reveal the potential correlation between TPW,OPW and MPD to create an accurate predictor of PIC morphology based on conventional measurements of TPW or OPW.Methods:Consecutive patients who underwent CT and CT angiography of the cervical spine were included.The DICOM data of the scans were reconstructed by imaging software,and five groups of measurements were obtained from different methods:transverse PIC width(TPW),internal height and isthmus height for defining HRVA,oblique PIC width(OPW),and minimum PIC diameter on the narrowest portion(MPD).Disparities and relationships between morphometric parameters measured from different methods were calculated,the evaluative performance of feasibility of safe C2 pedicle screw placement was compared,and the correlation between MPD and TPW and OPW was characterized.Results:A total of 304 consecutive C2 PICs were measured in 152 patients between April 2020 and December 2020.In OPW and MPD,the endosteal diameter,outer diameter and ratio of ED/OD were significantly larger than those in TPW(P<0.01).A difference in measurement was noted between the right and left PICs.The preclusion of C2 pedicle screw placement evaluated from TPW and HRVA was significantly higher than that evaluated from OPW and MPD.Strong agreement on the evaluative feasibility of C2 pedicle screw insertion and no significant difference in measurements were found between OPW and MPD,and the highest correlation coefficient(0.879)and determination coefficient(0.7720)suggested that the outer diameter of OPW could be useful for the precise prediction and estimation of MPD.Conclusion:MPD measurement of the C2 PIC with MPR-CT scans allows accurate measurement of the narrowest section of the C2 PIC.TPW and the definition of HRVA had partial false-positive rates and false-negative rates to evaluate the feasibility of the C2 pedicle for surgical fixation.The risk of vertebral artery injury due to misjudgment of C2 pedicle screw placement may be increased when the feasibility of screw placement is evaluated only from TPW.Conversely,when evaluating only the definition of HRVA,screw placement with relatively insufficient biomechanics,such as C2 pars screws,may be chosen because of preclusion of C2 pedicle screws.The outer diameter of OPW showed better evaluative performance and could be useful for precise prediction and estimation of MPD.