Biomechanical evaluation of atlantoaxial transarticular screw fixation technique

OBJECTIVE: To compare the biomechanical differences among the atlantoaxial transarticular screw fixation (Magerl) and other posterior fixation techniques. METHODS: Seven preserved atlantoaxial-complex specimens were harvested and fixated with Magerl, Magerl plus Gallie wiring, Magerl plus Brooks wiring, pure Brooks, pure Gallie, and Halifax interlaminar clamping fixation, respectively. The torque for every fixation technique was measured at the point of five-degree rotation of the atlantoaxial joint. RESULTS: The torque for Magerl was 6.59 Nmplus minus1.14 Nm, which was significantly higher than any other pure posterior techniques including Gallie (1.74 Nmplus minus0.31 Nm). Brooks (4.06 Nmplus minus0.48 Nm) and Halifax (3.44 Nmplus minus0.87 Nm) (P<0.01), but less than Magerl plus brooks (9.94 Nmplus minus1.45 Nm) (P<0.01). No statistically significant difference was found between Magerl and Magerl plus Gallie wiring (7.61 Nmplus minus1.10 Nm) or between Brooks and Halifax. CONCLUSIONS: Compared with other pure posterior fixation techniques the atlantoaxial transarticular screw fixation technique provides more torsion-resistance capacity. It is also suggested that combined Gallie wiring do not add any biomechanical superiority to this technique.