BACKGROUND: Jefferson fracture associated with unstable odontoid fracture is rare, and little reported.Occipito-cervical fusion is the commonly used treatment method, but it causes a severe loss of the motion of cervical vertebrae, which affects the patients' quality of life, so the curative effect is poor.OBJECTIVE: To evaluate the feasibility and therapeutic efficacy of atlantoaxial transpedicular screw fixation for Jefferson fracture associated with unstable odontoid fracture, so as to avoid occipito-cervical fusion and preserve the motion of the atlanto-occipital joint.METHODS: Fifteen patients with Jefferson fracture associated with unstable odontoid fracture from March 2010 to August 2015, were treated with atlantoaxial transpedicular screw fixation. There were 13 cases of Anderson type II and 2 cases of Anderson shallow type lll odontoid fracture, as well as 5 cases combined with transverse atlantal ligament rupture. All patients underwent skull traction after admission, as well as three-dimensional CT was applied preoperatively to determine the atlas pedicle screw trajectory and chose suitable screws. Atlantoaxial transpedicular screw was placed and atlantoaxial joint was reduced under general anesthesia. Bone graft fusion of atlantoaxial joint was applied only for the transverse atlantal ligament.The pain and neurologic function were evaluated by the Visual Analog Scale and the American Spinal Injury Association Impairment Scale before and after operation. The range of motion of the atlanto-occipital joint was observed during follow-up.RESULTS AND CONCLUSION: (1) The mean operation time was (150±41) minutes (120-270 minutes). The mean blood loss was (246±95) mL (160-500 mL). (2) Atlantoaxial transpedicular screws were successfully placed in all patients. No spinal and nerve root injury, or vertebral artery injury occurred intraoperatively. The atlantoaxial achieved good reduction. (3) The follow-up time was 12-36 months. There were nine cases of incomplete spinal cord injury, and 7 cases of obviously improved neurologic function. The visual analog scale scores were significantly improved at 1 year postoperatively, from preoperative (8.15±0.62) to postoperative (1.2±1.4) (P < 0.05). (4) All fractures and bone grafts were healed without loosening or rupture of the screws. The range of motion of the atlanto-occipital joint was (14.6±2.8)° postoperatively. (5) To conclude, atlantoaxial transpedicular screw fixation is effective for Jefferson fracture combined with unstable odontoid fracture, which not only exhibits a high rate of bone healing and stable fixation, but also avoids the occipital-cervical fusion and preserves occipito-atlantal motion.