Segmental C1-2 screw fixation using C1 lateral mass screws and C2 pedicle screws is a technically demanding procedure which can cause injuries to the vertebral artery or neural structures as well as massive bleeding from the epidural venous plexus. In particular, this procedure is more difficult in revision cases because of the lack of normal anatomical landmarks, adhesion, and bleeding. The authors report a case of a patient in whom preoperative surgical simulation and planning using computer software was very helpful in the direct screwing of the atlas and axis for a revision of atlantoaxial fusion.