The biomechanical study of atlantoaxial fixation.

ABSTRACT

Recent studies of various C(1-2) constructs have confirmed superior stability with transarticular screw fixation. In the meantime, our study on the C2 morphology in Thai people found about 4 per cent of the pedicles were too small for the 3.5 mm. C(1-2) transarticular screw. In order to select a smaller screw to use in this operation, we performed a biomechanical testing of 2 sizes of screw (2.7 mm, 3.5 mm) for transarticular screw fixation and Gallie's wiring, comparison in terms of stiffness in flexion, extension, torsion, anterior and posterior shear loads. There were no statistical differences of the stiffness between 2.7 mm and 3.5 mm transarticular screw fixation in all directions, whereas there were significantly greater stiffness of transarticular screw over Gallie's wiring in various directions (P<0.05).