Posterior Screw Placement on the Lateral Mass of Atlas

The width and height of the atlas lateral mass were larger than that of the C2 pedicle, and there was enough space to insert a 3.5-mm diameter screw in the atlas lateral mass over the C2 nerve. The pullout force of the screw on the lateral mass of the atlas was the same as that of the C2 pedicle screw. It is possible toinsert a 3.5-mm screw in the lateral mass of the atlas. The direction of the screw should be about 20 degrees anterosuperior in the vertical plane and 15 degrees inward in the horizontal plane. The suitable length of the screw should be approximately 22 mm inside the lateral mass.