Correlation Between The Course Of Intra-axial Vertebral Artery And Feasibility Of C2 Pedicle Screw Placement

Background:The course of the intra-axial vertebral artery(IAVA)shows diversity between different individuals.The inward and upward infringement of IAVA will reduce the safe space for pedicle screw placement,which will cause vertebral artery injury during the operation.Purpose:To investigate whether the course of IAVA is related to the feasibility of C2 pedicle screw placement(C2PSP)and to provide a reference for surgeons to choose a better surgical method for atlantoaxial instability.Method:The imaging data of patients undergoing cervical CT angiography at the China-Japan Union Hospital of Jilin University from October 2018 to October 2019 was analyzed Retrospectively.With the help of volume rendering and multi-planar reconstruction on PACS,the course of IAVA was observed and classified according to vascular parameters(Medial shifting and High riding)at the same time.The pedicle diameter(D)&height(H),the medial height(E),and height(a)& width(b)of the medullary cavity of pedicle isthmus were measured and recorded in different planes,which would be sufficient to analyze the relationshipbetween the course of IAVA and axial bone parameters.High-riding vertebral artery(HRVA)and classification of IAVA were used as the evaluation criteria for the feasibility of C2 PSP,and the two groups’ results were analyzed by comparing the sensitivity,specificity,and missed diagnosis rate.Result:The sample of this study included 100 people(200 sides).Among the 9 subtypes of IAVA,the incidence of B1 was the highest(36%,72/200),followed by A0(19%,38/200)and C2(12.5%,25/200),accounting for 67.5%.The diameter(D)and height(H)of C2 pedicle,and medial height(E)were proved to relate to the course of IAVA.The Pearson correlation coefficients corresponding to the medial shifting of IAVA and D,H,and E are-0.643,-0.284,and-0.437 respectively;the Pearson correlation coefficients corresponding to the high riding of IAVA and D,H,and E are-0.589,-0.214,and-0.553.As the criterion for evaluating the feasibility of C2 PSP,HRVA showed good sensitivity(0.78)and specificity(0.93),and its missed diagnosis rate was 22.22%.In contrast,the figure for C2 type of IAVA were 0.83,1.00,16.67%,which prove obvious advantages.Conclusion:1.The incidence of type B1 was highest in course of IAVA and the female and elderly intend to have greater medial shifting and high ridingof IAVA.2.The course of IAVA is related to the diameter,height,and medial height of C2 pedicle.Those with greater MS and HR will have more narrow and shorter pedicle.3.Compared with HRVA,the C2 type of IAVA would be more suitable as the criterion for the feasibility of C2 PSP.