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Purpose: Several techniques have been introduced to manage irreducible atlantoaxial dislocation (IAAD). However, no study has reported the surgical method for the management of IAAD caused by odontoid fracture malunion. This study aimed to introduce a surgical method of transoral anterior release, odontoid partial resection, and reduction with sequential posterior fusion for the treatment of IAAD caused by odontoid fracture malunion. We also evaluated the clinical efficacy of this surgery. Methods: This study included seven cases of IAAD caused by odontoid fracture malunion, collected from January 2008 to January 2011. Anterior atlantoaxial release was performed through anterior transoral approach, followed by partial resection of the odontoid process. C1-C2 were then fixed through pedicle screws and rods, and then fused posteriorly by single stage. Neurologic status was evaluated using the Japanese Orthopaedic Association (JOA) scoring system. Results: All seven patients had complete release, and satisfactory reduction. Bony fusion was seen in all patients postoperatively. The patients were followed up for an average of 19.6 months (ranged from 9 to 36 months). The average of patients JOA scores at the final follow-up was significantly higher than that of their preoperative scores. Furthermore, the average improvement in neurological function was 87.4 %. No screw loosening, implant migration or implant failures, atlantoaxial redislocation, or signs of instability were observed in any of the patients during the follow-up period. Conclusions: Transoral anterior release, odontoid partial resection, and reduction combined with posterior fusion are effective, reliable, and safe procedures for the treatment of IAAD caused by odontoid fracture malunion. [ABSTRACT FROM AUTHOR]