BACKGROUND: The treatment of upper cervical spine disorders through a posterior pedicle fixation approach have been carried out in some domestic large hospitals, but this surgery is still considered as a difficulty of cervical spine surgery. In order to minimize the risk of surgery, the authors designed a program of individual operations, and combined with self-developed pedicle locating and directing speculum to determine precise intraoperative position of pedicle screws, and no report is found by searching related database in China.OBJECTIVE: To improve the one-time success rate of internal fixation screws, to investigate the biomechanical effect of the implant, to formulate a simple, practical, individual protocol for atiantoaxial pedicle screw-plate system based on related data. METHODS: A total of 31 patients were recruited from Department of Orthopaedics in the 251 Hospital of Chinese PLA, between January 2002 and September 2006. Under the guidance of self-made atlantoaxial locating and directing speculum, the entrance point and angle for screw insertion, as well as screw diameter and length were determined according to the results of X-ray and CT measurement. Atlas pedicle screw was inserted at left (19.93±1.32) mm, and right (19.16±1.3) mm; Atlas pedicle screw insertion angle to inside was left (23.72±2.09)°, and right (23.35±1.91)°; Atlas pedicle screw insertion angle to side of head was (9.00±1.20)°. Axis pedicle screw was inserted at left (13.14±0.82) mm, and right (13.85±0.79) mm; Axis pedicle screw insertion angle to inside was left (24.52±1.26)°, and right (20.42±1.42)°; Axis pedicle screw insertion angle to side of head was (25.00±3.00)°.RESULTS AND CONCLUSION: ①Totally 124 pedicle screws were implanted into 31 patients, and 122 screws were of one-time success. The precision rate was 98.39%. Two screws were secondly inserted because of cutting lateral cortical bone of pedicle for deviation of inward angle. ②Occipital neuralgia was found in 2 cases postoperatively and cured after one month of treatment;screws penetrated atlas left vertebral lateral wall in 2 cases, no spinal or vertebral artery injury was found. ③Radiographs showed that atlas was completely reduced in all patients, and apposition of dentoid process of axis fracture was good. CT films showed the screws a good location to the vertebrarterial spinal cord. ④The follow-up visit was averaged of 10.5 months. Bony fusion was found in all patients. No screw-plate breakage was found. No inflammatory or rejection reactions occurred.⑤By JOA scale, there were 16 cases of excellent, 12 cases of good, 2 cases of fine, and 1 case of poor. The excellent and good rate was 90%. It is suggested that the success rate of atlantoaxial pedicle screw-plate mplantation can be improved through a biomechanical angle.

Objective To explore the clinical effect of the atlanto-axial pedicle screw internal fixation to reconstruct upper cervical spine instability. Methods Using atlanto-axial pedicle screw and internal fixation system combined with autogenous iliac bone graft to treat 21 patients with upper cervical spine instability. Type Ⅱ odontoid process old fracture was 13 patients, odontoid process nonunion was 5 patients, injury of the transverse ligament was 3 patients. They were placed in 84 atlanto-axial pedicle screws, autogenous bones were placed in the posterior arch of atlas and axis to fusion, so that atlanto-axial complex got stabilized. Results The left lateral cortical bone of atlas vertebral pedicle was broken by screws in 2 patients, but the spinal cord and vertebral artery was intact. X-ray film showed the atlas and the fracture of dens of axis was completely replaced in all patients. The position of screw and vertebral artery or spinal cord was good in CT image. According to JOA score standard, 15 cases of all were excellent, 3 cases were good,2 cases were common,1 case was bad, and the rate of excellent and good was 85.71%(18/21).Seventeen cases were followed up for 12-26 (12.83 ± 4.23) months, all patients had acquired bone fusion and found no screw and plate fracture. Conclusions Atlanto-axial pedicle screw combined with screw-plate system fixation to treat upper cervical spine instability, can significantly enhance the biomechanical stability of the atlanto-axial interbody, bone grafting fusion rate is higher, the application value of the atlanto-axialfusion is higher.