Cai Xiaojun, He Bin, Han Jianhua, Li Daijun (Department of Spine Surgery, Zunyi Hospital, The Third Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou, 563002, China) The technique of atlantoaxial pedicle screw fixation has been researched and reported by scholars at home and abroad [1-4], and based on the experience of the actual operation and the observation of the dry bone specimen, we have compared the anatomical relationship between the atlantoaxial posterior vertebral artery sulcus and atlantoaxial pedicle midpoint. We compared the anatomical relationship between the atlas “posterior vertebral artery groove node” and the midpoint of the atlantoaxial pedicle, and established the atlantoaxial pedicle screw insertion technique with the atlantoaxial “posterior vertebral artery groove node” as the reference mark for localization. Cai Xiaojun, Department of Orthopaedics, Zunyi First People’s Hospital, Zunyi City, China Data and Methods 1. General materials: 40 sets of adult atlantoaxial trunk bone specimens were taken, irrespective of age and gender, and the appearance of the specimens was excluded from damage and deformity. Vernier calipers (accuracy of 0.02mm), protractor (accuracy of 1°), Photoshop CS2 software and other tools were used for atlantoaxial anatomical observation, to observe the morphology of the atlantoaxial vertebral artery sulcus and “posterior vertebral artery sulcus nodule” and its correspondence with the midpoint of the pedicle root, and to count the number of atlantoaxial vertebrae and the number of atlantoaxial vertebrae in the “posterior vertebral artery sulcus”. The probability of the occurrence of the “posterior vertebral artery groove nodule” in the atlantoaxial spine was also counted. 2. Measurement indexes (Figure 1): D1 and D2: vertical distance between the inner and outer edges of the atlantoaxial pedicle and the midsagittal plane; D3: vertical distance between the midpoint of the atlantoaxial pedicle and the midsagittal plane of the spinal canal; D4: vertical distance between the atlantoaxial “posterior vertebral artery sulcus node” and the midsagittal plane of the spinal canal; D5: atlantoaxial “posterior vertebral artery sulcus node”. D5: the vertical distance between the atlantoaxial “posterior tubercle of the vertebral artery groove” and the inner edge of the pedicle (the difference between D4 and D1); D6: the vertical distance between the atlantoaxial “posterior tubercle of the vertebral artery groove” and the midpoint of the pedicle (the difference between D3 and D4); D7, D8, and D9: the width, upper and lower diameters, and lengths of the pedicle. 3. Statistical processing: All data were processed by SPSS12.0 statistical software, and the atlantoaxial measurements obtained from the experiments were expressed as ±S. The difference between the left and right side data was compared using the t-test with the test level of α=0.05, and the difference was considered to be statistically significant at P<0.05. Results 1. Morphology and occurrence rate of atlantoaxial "posterior vertebral artery groove nodule": the vertebral artery groove, as an important component of the atlantoaxial vertebral arch root, is located above the posterior arch and the lateral block linkage, and there is a bony spine on the posterior aspect of the groove, which was observed to have a relatively constant position in the specimen, and thus it was called atlantoaxial "posterior vertebral artery groove nodule" (Fig. 2). " (Figure 2). We observed three basic patterns of atlantoaxial vertebral artery grooves, i.e., shallow groove type, deep groove type, and annular type, and counted 47 sides of shallow groove type (59%), 28 sides of deep groove type (35%), and 5 sides of annular type (6%). "Posterior vertebral artery sulcus nodules also had different patterns, and we classified the easily recognizable posterior vertebral artery sulcus nodules into three basic types, namely, flat, elevated, and protruding (Fig. 3); in this group, there were 27 (34%) flat, 14 (18%) elevated, and 5 (6%) posterior vertebral artery sulcus nodules, and there was no evidence that they were flat. In this group, there were 27 sides (34%) of flat type, 14 sides (18%) of bulging type, and 37 sides (46%) of protruding type, and there was only one case (2 sides, 3%) of atlantoaxial arch root and vertebral artery groove dysplasia, which made it impossible to determine whether there was a "posterior nodule of vertebral artery groove" or not. Combined with the above observations, the probability of easily recognizable atlantoaxial "posterior vertebral artery groove nodules" was 97%. 2. Atlantoaxial anatomical measurements: Atlantoaxial anatomical measurements were not statistically different between the right and left sides (P>0.05 for each group), so the measurements of both sides were combined. In the data of this group, the atlantoaxial “pedicle” upper and lower diameters were <3.5mm in 12 sides (accounting for 15%), ≥3.5mm, <4.0mm in 17 sides (accounting for 21.25%), and ≥4.0mm in 51 sides (accounting for 63.75%); the smallest diameter was limited to 3.00mm, and the largest to 6.84mm; and the widths of pedicles were all above 7.00mm. The width of the atlas was above 7.00mm. 3. Correspondence between the atlantoaxial "posterior vertebral artery groove nodule" and the atlantoaxial pedicle: the atlantoaxial "posterior vertebral artery groove nodule" was located at the lateral aspect of the atlantoaxial posterior nodule (16.31±1.69 mm), 2.26±0.75 mm lateral to the inner edge of the atlantoaxial pedicle, 0.75 mm from the inner edge of the atlantoaxial pedicle, 2.26±0.75 mm from the inner edge of the atlantoaxial pedicle, and 0.75 mm from the outer edge of the atlas. 0.75) mm lateral to the inner edge of the atlantoaxial pedicle (2.26±0.75) and 2.14±0.82 mm medial to the midpoint of the atlas (i.e., between the inner edge of the atlantoaxial pedicle and the midpoint). Table 1 The measure results of the atlas. ( ±S, min~max, n=80) Tab1 The measure results of the atlas. ( ±S, min~max, n=80) Part Left side Right side Mean value D1 13.86±1.42 mm (11.21-17.22 mm) 14.47±2.11 mm (12.07-17.20 mm) 14.17±1.77 mm D2 21.99±2.14 mm (11.20-28.38 mm) 23.44±2.15 mm (12.07-28.05 mm) 22.72±2.15 mm D3 18.14±1.56 mm (15.76-22.03 mm) 19.00±1.64 mm (15.94-21.55 mm) 18.57±1.60 mm D4 16.15±1.70 mm (13.15-18.92 mm) 16.46±1.68 mm (14.01-19.89 mm) 16.31±1.69 mm D5 2.32±0.77 mm (1.36-3.50 mm) 2.20±0.77 mm (12.07-28.05 mm) 2.20±0.15 mm (12.07-28.05 mm) 22.72±2.15 mm D5 2.32±0.77 mm (1.36-3.50 mm) 2.20±0.73 mm (1.34-3.18 mm) 2.26±0.75 mm D6 2.12±0.86 mm (0.69-3.85 mm) 2.15±0.77 mm (1.35-5.04 mm) 2.14±0.82 mm D7 8.63±1.22 mm (7.04-11.72 mm) 8.47 D7 8.63±1.22 mm (7.04-11.72 mm) 8.47±1.23 mm (7.28-11.86 mm) 8.55±1.23 mm D8 4.28±0.81 mm (3.00-6.84 mm) 4.28±0.81 mm (3.00-6.84 mm) 4.28±0.82 mm D9 9.68±1.34 mm (7.14-13.78 mm) 9.51±2.09 D9 9.68±1.34 mm (7.14-13.78 mm) 9.51±2.09 mm (7.40-14.59 mm) 9.60±1.72 mm