Morphologic Consideration of C2 Isthmus for Placement of Transarticular Screws Using Human Cadaveric Vertebrae.

We investigated the morphology of the C2 isthmus for the placement of transarticular screws using human cadaveric vertebrae and 3D-CT, for safe screwing of C1-2 fixation in an identical manner to the Magerl technique. We measured the width of the C2 isthmus, optimum screw insertion angle, and optimum length of the screw.There were significant differences in the measured values among the cadaveric vertebrae and each side (right and left). The measured values of human cadaveric vertebrae correlated precisely with those of 3D-CT. The safe screw passage area between spinal canal and vertebral artery is severely limitted.The Magerl technique is commonly performed under anteroposterior and lateral view images. Some have pointed out that this technique is difficult because it requires a high degree of skill. These results demonstrate that preoperatively reconstructed 3D-CT is relatively valuable for safe screw fixation by the Magerl technique.