Three-dimensional computed tomography-based, personalized drill guide for posterior cervical stabilization at C1-C2

Study Design. Cadaver and preliminary clinical study. Objectives. To enhance the precision of screw positions for posterior transarticular fixations according to Magerl at C1-C2. Summary of Background Data. The vertebral arteries are at risk during the Magerl operation and may be damaged in up to 4.1% of cases. Even intraoperative navigation, as often used nowadays, does not provide optimal screw positioning in all patients. Methods. According to the three-dimensional CT data obtained for every individual cadaver or patient, a template was designed for the posterior course of C2: the template contains a drill guide allowing navigated screw positioning inside the left and right isthmus of C2. For a first series of five cadavers a template with clamps connecting only to the lamina of C2, excluding the spinous process from the interface, was carried out, For a second series of three cadavers the template was connected not only to the lamina but also to the spinous process of C2. Both cadaver series were performed without any fluoroscopic control at surgery. Eventually the technology was applied in two clinical cases. Results. The rotational stability of the template toward the lamina C2 was insufficient in the first series, but for the second series both the entry points and screw trajectories were very satisfactory. Conclusions. Although the actual experience is limited, the idea of using a template with drill guide might simplify and shorten the surgical act and at the same time enhance the accuracy of C1-C2 transarticular screw positioning.