OBJECTIVETo determine the three-dimensional stability of C1-C2 after anterior approach screw fixation through C2 vertebral body to C1 lateral mass for C1-C2 instability or dislocation.

METHODSThe three-dimensional range of motion of atlantoaxial joint were measured in 16 human cadaveric specimens under four conditions: the intact state (1st group), odontoid fracture of type II (2nd group), instrumentation with posterior C1-C2 trans-articular screw fixation (Magerl technique) (3rd group) and anterior approach screw fixation through C2 vertebral body to C1 lateral mass (4th group) respectively.

RESULTSThere was generally significant difference between 1st group and other groups and between 2nd group and other groups by statistics analysis (P < 0.001). Range of motion significantly decreased in 3rd group and 4th group in all directions. There was generally no significant difference between the two methods by statistical analysis (P > 0.05).

CONCLUSIONAnterior approach screw fixation through C2 vertebral body to C lateral mass provides satisfied stability. It provides the equivalent effect to Magerl technique. It is a kind of reliable surgery choice for the treatment of instability or dislocation of C1-C2 joint.