Abstract: BACKGROUND: At present, there is a lack of an internal fixation system with good reduction and simple operation for the treatment of atlas burst fracture by posterior single-segment fixation.
OBJECTIVE: Based on the atlas CT measurement data, a new posterior atlas fracture reduction and internal fixation system was designed and optimized, which was in line with the characteristics of human local anatomical structure, easy to operate and with good reduction.
METHODS: CT images of 347 adults were analyzed retrospectively. In the images, the length of pedicle screw track with a medial inclination of 0°, the angle of the maximum medial inclination angle and the length of pedicle screw track at this time, the height of vertebral artery groove, the distance between the entry points of bilateral pedicle screws and the midline, the radius of the posterior arch of atlas, the distance between the posterior tubercle of the atlas and the posterior edge of the foramen magnum, and the distance between the posterior tubercle of the atlas and the upper surface of the axial arch were measured. The imaging data were analyzed and a reduction and internal fixation system was designed and optimized for atlas fracture in line with human anatomical characteristics. 
RESULTS AND CONCLUSION: (1) There was no statistically significant difference in the the length of pedicle screw track with a medial inclination of 0°, the maximum medial inclination angle and the length of pedicle screw track at this time, the height of vertebral artery groove, the distance between the entry points of bilateral pedicle screws and the midline, the radius of the posterior arch of atlas, the distance between the posterior tubercle of the atlas and the posterior edge of the foramen magnum, and the distance between the posterior tubercle of the atlas and the upper surface of the axial arch measured on the left and right sides of all subjects (P > 0.05). There were statistically significant differences in each index measured between the male and female groups (P < 0.05). (2) The new posterior atlas fracture reduction and internal fixation system has been successfully designed and obtained the national patent. The internal fixation system is suitable for the anatomical characteristics of the posterior arch of the atlas. It can not only effectively treat the atlas burst fracture, but also retain the movement function of the occipital atlantoaxial joint.  

Key words: internal fixation of atlas fracture, atlas anatomy, CT image measurement, internal fixation system design