ObjectiveTo explore the application value of thin CT angiography (CTA) of pedicle sagittal plane of axis for preoperative evaluation planning pedicle screw placement.MethodsBetween February 2016 and August 2017, 34 patients (68 pedicles) who underwent thin CTA scan before posterior axial surgery were retrospectively analyzed. The vertebral artery development was statistically analyzed. The continuous layers of transverse process hole pedicle height more than or equal to 4 mm (f) were measured and read. The axial fixation methods, clinical manifestations of vertebral artery and spinal cord injury and the bone union of fractures or implants were recorded. Postoperative results of pedicle screws were evaluated by CT scan.ResultsThe right sides of 8 cases and the left sides of 18 cases were dominant vertebral arteries, and equilibrium was reached in 8 cases; f>9 layers were found in 16 pedicles,f=9 layers in 27 pedicles, f=8 layers in 17 pedicles, and f<8 layers in 8 pedicles. The 43 pedicles off≥9 layers used pedicle screw fixation; in the 17 pedicles of f=8 layers, 16 used pedicle screw fixation, and the other one used laminar screw fixation; in the 8 pedicles of f<8 layers, 4 used pedicle screw fixation, and the other 4 used laminar screw fixation. A self-defined pedicle screw grading system was used to evaluate the excellence, and the result showed that,f>9 layers: 14 pedicles were class A, 2 were class B, none was class C;f=9 layers: 16 pedicles were class A, 7 were class B, 4 were class C; f=8 layers: 3 pedicles were class A, 5 were class B, 8 were class C; f<8 layers: none was pedicles class A or class B, 4 were class C. The other 4 lamina screws fixation didn’'t invade the spinal canal. One case of pedicle class C showed clinical manifestations of mild dizziness and drowsiness. The patients were followed up for 6-11 months with an average of (8±3) months, and the fracture or bone graft fusion were observed after 6 months of following-up.ConclusionBased on preoperative CTA thin layer scanning, through measuring and reading continuous layers of transverse process hole pedicle height more than or equal to 4 mm, can effectively judge the security of axial pedicle screws in order to subsequently choose the reasonable operation methods so as to improve success rate and decrease surgical risk.