To compare the clinical and radiographic outcomes of irreducible atlantoaxial dislocation (IAAD) treated with posterior fusion after anterior release and direct posterior reduction of the dislocation. Online databases were searched for articles describing IAAD published from 1999 to 2015. Five studies (105 patients) described treatment with posterior fusion after periodontoid tissue release, and five studies (113 patients) described treatment with direct posterior reduction of the dislocation. The primary outcomes in this study were the complete reduction rate, Japanese Orthopedic Association score, perioperative morbidity, perioperative mortality, complications, vascular injury, and infection. Standard meta-analysis techniques were used to compare the outcomes. Of 319 citations examined, 10 articles involving 218 participants were eligible. Overall, there were no significant differences between the anterior release and posterior fixation (ARPF) group and direct posterior reduction and fixation (DPRF) group in the complete reduction rate, neurologic recovery rate, perioperative morbidity, perioperative mortality, vascular injury, or infection. However, the complication rate in the DPRF group was much lower than that in the ARPF group. Compared with posterior fusion after anterior release, direct posterior reduction of the dislocation showed no significant differences in terms of the complete reduction rate, neurologic recovery rate, or fusion rate; however, it was a simpler process associated with less surgical trauma and a shorter operation time. Because of the limitations of the small sample in this study, whether direct posterior reduction of the dislocation is more effective and safer than posterior fusion after anterior release remains unclear. III. [GRAPHICS] . These slides can be retrieved under Electronic Supplementary Material.