Objective To analyze the clinical effect of anterior cervical decompression with double-way connection intervertebral fusion device (ROI-C) implantation for type Ⅱ or type Ⅱ a Hangman fracture.Methods A retrospective study was made on 14 patients with type Ⅱ or type Ⅱ a Hangman fracture treated with anterior cervical ROI-C implantation between February 2011 and March 2014.The patients (11 males and 3 females) were aged between 22 and 46 years (mean,26.4 years).Nine patients sustained traffic injury,4 fall injury and 1 crash injury.Nine patients were classified as type Ⅱ and 5 type Ⅱ a according to the Levine-Edwards classification.All were completed cervical anteroposterior and lateral X-ray,CT scan,three-dimensional CT reconstruction and MRI examination after adnission.American Spinal Injury Association (ASIA) grade E was noted in all before operation.Clinical posttraumatic neck score,visual analogue scale (VAS) as well as angle deformity and displacement of the axis were recorded before operation and at the latest follow-up.Results All patients were operated successfully.Mean operation time was 61 min(range,45-116 min).There were no injuries of superior laryngeal nerve,hypoglossal nerve,throat wall and vessel during operation.Laryngeal edema,dysphagia,paralysis of tongue,hematoma and wound infection were not observed after operation.Mean period of follow-up was 24.2 months (range,4-32 months).All segments and fracture sites showed solid fusion after 3 months.No cages became subsided or displaced,no discs collapsed,and no malunion occurred at the latest follow-up.Data of preoperation and latest follow-up differed significantly with respect to clinical posttraumatic neck score[(53.1 ±7.2) points vs.(91.1 ±5.0)points],VAS[3.38(2.43,4.33)points vs.0.58(0,1.29) points],axis displacement[(4.0 ± 1.5) mm vs.(1.3 ± 1.2) mm],and angle deformityoftheaxis[(9.2±4.7)° vs.(2.1 ±1.9)°] (P＜O.05 or O.01).Conclusion Anterior cervical surgery with ROI-C implantation for type Ⅱ or type Ⅱa Hangman fracture provides good fusion rate and satisfactory clinical effect.