Safety of atlantoaxial transarticular screw combined with C 1 pedicle screw fixation / 中华创伤杂志

ABSTRACT

Objective:To investigate the safety of posterior atlantoaxial transarticular screw combined with atlas pedicle screw fixation in Chinese.Methods:CT data of upper cervical spine in 48 patients were collected from Ningbo No.6 Hospital, including 26 males and 22 females aged 26-58 years [(37.3±13.5)years]. All CT data was transformed into 3D dimensional model and inserted with virtual screws by Mimics 19.0. Firstly, the vertical plane P 1 and the horizontal plane P 2 of the atlas were built in those atlantoaxial models, secondly the atlantoaxial transarticular screw S 0 was inserted by Margel method, and it's insertion point was located at 3 mm lateral and 2 mm cephalad in the C 2 inferior articular process. Finally, four atlas pedicle screws were inserted at the midline of atlas lateral mass. The four screws are inserted as follows. S 1: the screw was tangent to the lateral side of the S 0 or the medial of the atlas pedicle. S 2: the screw was tangent to the lateral wall of the atlas pedicle. S 3: the screw was tangent to the upper wall of the atlas pedicle. S 4: the screw was tangent to the inferior wall of the atlas pedicle. The angles between S 1, S 2 and P 1 as the camber angle, and the angle between S 3, S 4 and P 2 as the gantry angle were measured. Then the safety range of camber angle and gantry angle were calculated, and the screw length of S 1, S 2, S 3 and S 4 was measured. In all models, the camber angle and gantry angle of the screws were adjusted an interval of 2°, the number of successful cases was calculated and the success rate of insertion was calculated. Results:All 3D models were inserted successfully. The minimum value, maximum value and safety range of the camber angle of atlas pedicle screws were (-6.7±5.2)°, (10.4± 4.3)°, (17.1±3.7)°, respectively; and of the gantry angle were (-0.5±3.5)°, (11.0±5.8)°, (11.5±4.9)°, respectively. The length of screw placement was S 1: (31.1±2.4)mm, S 2: (28.3±2.5)mm, S 3: (29.2±3.8)mm, S 4: (29.6±3.0)mm, respectively ( P<0.05). When the camber angle was from -1°to 5°, the success rate of screw placement was 87.5%; when inserting with 2° camber angle, the success rate was 100%; when the gantry angle was 5°, the success rate was 93.8%. Conclusion:The posterior atlantoaxial transarticular screw combined with atlas pedicle screw can achieve satisfy insertion length and success rate.