Atlantoaxial fusion using anterior transarticular screw fixation of C1-C2: technical innovation and biomechanical study

This study is an attempt to describe a new technique for anterior transarticular screw fixation of the atlantoaxial joints, and to compare the stability of this construct to posterior transarticular screw fixation with and without laminar cerclage wiring. Nine human cadaveric specimens were included in this study. The C1 - C2 motion segment was instrumented using either anterior transarticular screws ( group 1), posterior transarticular screws alone ( group 2), or posterior screws with interlaminar cerclage wires ( group 3). Using an unconstrained mechanical testing machine, the specimens were tested in rotation, lateral bending, and flexion-extension using nondestructive loads of +/- 2 N m. The specimens were also tested in translation using nondestructive loads of +/- 100 N. All values for the three groups with regards to anterior-posterior displacement, rotation, and lateral bending were similar as determined using a Kruskal - Wallis rank sum test with a significance level of p< 0.05. The only significant difference was registered in flexion-extension where the cerclage wire added some strength to the construct. Anterior transarticular screw fixation of the atlantoaxial spine has several advantages over posterior fixation techniques, and is as stable as posterior transarticular fixation in all clinically significant planes of motion. The addition of posterior interlaminar cerclage wiring further improves resistance to flexion-extension forces. Anterior transarticular screw fixation of the atlantoaxial joint is a useful technique for achieving C1 - C2 stabilization.