Optimal Screw Entry Point And The C1 Pedicle Screw Method For Atlantoaxial Disease In Children

ObjectiveThis study will provide a reference for the best insertion point and angle of the atlas pedicle screw in children by measuring the diameter parameters of the atlas in children,and improve the accuracy and safety of screw placement.MethodThe study population included 2-6-year-old children who underwent 64-slice CT scans from January 2017 to June 2020,and 153 children who met the criteria were selected.There were 23-45 children,with an average of 30 children in each age group.Children who met the study criteria requirements were further divided into four groups,according to sex and according to age:2-4 years old(N=79)and 5-6 years old(N=74).Measurements were collected for the gap width available for bilateral C1 pedicle screws at different inclination angles as well as for the length of the pedicle screw path at the best position,the horizontal distance from the point of entry to the intersection of the lateral mass and the inner edge of the posterior arch,and the inclination angle.Statistical analysis was conducted to explore whether age and gender differences were statistically significant.ResultsWhen the screw path is parallel to the line connecting the inner intersection of the anterior arch and the lateral mass and the inner intersection of the posterior arch and the lateral mass,the available gap width is the largest,and the difference in the maximum usable gap width of the screw at different introversion angles is statistically significant.Significance(P<0.01).When children’s C1 pedicle screws are at the best screw-in angle,the screw path length for children aged 2-4 years is(23.05± 1.92)mm,and the screw path length for children aged 5-6 years is(26.56±3.58)mm(P<0.01).The horizontal distance e from the screw insertion point to the point of intersection of the lateral mass and the inner edge of the posterior arch for boys aged 2-4 years was(5.10±0.69)mm,and that for girls was(5.39±0.83)mm(P<0.05).There was no gender difference in e-values for children aged 5-6 years.(P>0.05),both are(6.24±1.16)mm(P<0.05).The optimal inclination angle is(20.57±3.25)° for children aged 2-4 years,and(21.32±2.83)° for children aged 5-6 years(P<0.05).ConclusionAt the intersection of the inner edge of the posterior arch of the children’s atlas and the lateral mass as a reference mark,draw a vertical line 5.7mm horizontally outward.The intersection point between this line and the lower edge of the posterior arch of the atlas is the best insertion point,but the difference caused by age and gender should be considered.The screw path is parallel to the line connecting the inner intersection of the anterior arch and the lateral mass with the inner intersection of the posterior arch and the lateral mass at the optimal inclination angle.At this time,the inclination angle is 20.93°,and the difference caused by age needs to be considered.