Radiological Anatomical and biomechanical study of new L5 insertion point for Placement of Pedicle Screw
Objective Three-dimensional CT reconstruction and biomechanical analysis were used to evaluate the feasibility of pedicle screw placement technique based on the new L5 insertion point(Cao's point)and the differences in fixation strength compared with traditional technique.Methods From Janu-ary 2024 to October 2024,30 volunteers who underwent lumbar CT at the First Affiliated Hospital of Nan-jing Medical University were recruited for three-dimensional reconstruction to determine the new screw entry points.Additionally,100 cases of lumbar CT conducted at the same hospital during the same period were collected.The distances between the new insertion points and the pedicle axis,as well as the angles in the sagittal and horizontal planes,were measured.Six spinal specimens provided by the Anatomy Teaching and Research Department of Nanjing Medical University were selected for biomechanical analysis to measure the maximum insertion torque and the maximum axial pull-out force.The Wilcoxon rank-sum test was employed to assess and analyze the differences in fixation strength between the novel screw placement technique and the traditional method.Results The mean distance from the new insertion point to the pedicle axis was 4.67 mm.The Angle between the endplate on the sagittal plane and the line at the posterior edge of the L5-S1 spinous process is about 80°.The mean water plane Angle was 20.84°when the simulated screw was incised to the medial wall of the pedicle.The mean water plane Angle was 10.22°when tangential to the lateral wall of the pedicle.The average horizontal safety Angle is 11.14°.The mean value of the new L5 insertion point is 163.3 N/cm,and that of the Magerl method is 98.2 N/cm.Wilcoxon rank sum test showed a statistically significant difference between the two groups(Z=-2.201,P＜0.05).The average maximum axial pull-out force of the new L5 insertion point is 551.09 N,and that of the Magerl method is 514.68 N.Wilcoxon rank sum test showed a statistically significant difference between the two groups(Z=-1.992,P＜0.05).Conclusion The pedicle screw placement technique based on the new L5 insertion point(Cao's point)is technically feasible and can offer a more stable internal fixation effect compared with the traditional technique in terms of fixation strength.
L5 pedicle screwInsertion pointAnatomyBiomechanicsExtraction forceInsertion moment
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