Journal ArticleAtlantoaxial instability can result from trauma, rheumatoid arthritis, congenital malformation, or tumor invasion. The goal of treatment is stabilization of the C1-C2 complex to prevent neurologic and neurovascular compromise. First described in 1987 by Magerl and Seemann, C1-C2 transarticular screw fixation has been shown to yield excellent fusion rates.1-4 Several authors have reported that this technique offers the best biomechanical stability and allows the least amount of rotation.5-8 However, placement of transarticular screws (TASs) is technically challenging and incurs significant risk of neural and vascular injury. Previous clinical studies of C1-C2 TAS fixation have reported screw misplacement in up to 15% of patients, with an 8% rate of vertebral artery (VA) injury.9,10 Safe and accurate screw placement requires thorough radiologic assessment of the cervical spine with careful preoperative planning of screw trajectory
