Objective:To determine the three-dimensional stability of atlantoaxial reconstruction with anterior approach screw fixation through C2 vertebral body to C1 lateral mass and Gallie’s technique for C1~2 instability.Methods:25 human cadaveric specimens were randomly divided into 5 groups.The three-dimensional range of motion C1 relatively C2 was measured under five different conditions

the intact state(intact group)

odontoid tape Ⅱ fracture(group OTF)

fixation with posterior C1~2 transar- ticular screw(group PTS)

anterior approach screw fixation through C2 vertebral body to C1 lateral mass(group ASM)

ASM and Gallie’s technique(group ASMG). The obtained data were statistically analyzed. Results:The range of motion in all directions group ASMG

ASM and PTS was significantly decreased.There was significant difference among group ASMG

ASM and PTS in flexion/extension and lateral bendings by statistical analysis(P<0.05)

and no difference in axial rotation by statistical analysis (P>0.05). Conclusion:In vivo biomechanics studies showed that ASMG had unique superiority in the reconstruction of the atlantoaxial stability

especially in controlling the instability of flexion/extension and lateral bendings.It was one kind of reli- able surgical choice for the treatment of the obsolete insta- bility or dislocation of C1~2 joint.