Objective    To explore the feasibility of C

1

－C

2

pedicle screw fixation and fusion with bone autografting for treatment of atlantoaxial instability.     Methods    Twenty-three adult patients

16 males and 7 females with a mean age of 36.8 (ranging from 17 to 64)

with atlantoaxial dislocation in 2 h to 7 d (mean 18 h) after trauma were hospitalized in our department from January 2008 to December 2009. There were 5 cases having ligamentum transversum fracture

and 1 case of Anderson Ⅰ dens fracture

11 cases of Anderson II fracture

and 6 cases of Anderson Ⅲ fracture. All cases were accompanied with spinal c

ord dysfunction. After skull traction was carried out for 3 or up to 12 d until reset

these cases were treated with C

1

－C

2

pedicle screw fixation and fusion with bone autograft under general anesthesia. The entry point of C

1

pedicle screw in present technique was located on the vertical line through the central point of C

2

lateral mass

and at least 3 mm under the superior rim of C

1

posterior arch

15  in a medial inclination and 10  in a cephalic direction. The entry point of C

2 

pedicle screw was located in center of the medial-superior quadrant

30° in a medial in inclination and 30° in a cephalic direction. The screw diameter was 3.5 mm

and the screw length of C

1

and C

2

pedicle screws were 26 to 30 mm and 22 to 26 mm

respectively. The group of the patients were followed up for 8 to 25 months.     Results    No intraoperative complication such as injuries of vertebral artery or spinal cord occurred. During the follow-up

their clinical symptoms were improved to some extent. The postoperative X ray verified that not only the anatomic relationship between atlas and axis had restored well

but also all of pedicle screws were in a proper position without loosening

breaking or bending. The postoperative solid bone fusion was observed at 3 to 6 months after operation.     Conclusion    The approach of C

1

－C

2

pedicle screw fixation and fusion with bone autografting is a good approach for atlantoaxial instability with immediate stability of the operative segments and postoperative solid bone fusion. It is an option for posterior surgical approaches to treat atlantoaxial instability.