Aim: Atlantoaxial instability is a special entity that may be caused by many disorders such as trauma, tumor, arthritis, congenital malformation and infection. Atlantoaxial fixation is needed to provide stability, prevent neurological deficits and correct deformity. The objective of this study is to introduce an alternative technique for the treatment of atlantoaxial instability in patients who have vertebral artery anomaly, anomalous C2 or osteoporosis. Material and Methods: C1-2-3 fixation was performed in a 50-years-old, male patient with atlantoaxial instability due to os odontoideum. C1 lateral masses identified and screw placement was performed. C2 facet joints were identified bilaterally. Superior margin of junction of pedicle and the lamina was used as the entry point and 3.5x22 mm screws were inserted from C2 facet joint to the C3 facet joint in mediolateral and craniocaudal direction under fluoroscopic guidance with caution. The posterior fixation screws are interconnected with two rods. Finally, autologous grafts were placed posterolaterally to encourage the fusion. Results: Patient’s complaints relieved after the surgery. C1-C2 instability wasn’t seen in the postoperative radiological examinations. Conclusion: In the surgical treatment of C1-2 instability, our technique could help to reduce the possibility of vertebral artery injury in patients who have a vertebral artery course anomaly or when it is difficult to place C2 pedicle screws due to anomalous C2 pedicles and osteoporosis. High fusion rate could be achived with this technique due to passing through the four cortical surfaces. No wire or allograft was required. Thus, the instrumentation cost could be reduced.