Direct Internal Fixation for Unstable Atlas Fractures

Purpose: To investigate the radiologic and clinical outcomes of direct internal fixation for unstable atlas fractures. Materials and Methods: This retrospective study included 12 patients with unstable atlas fractures surgically treated using C1 lateral mass screws, rods, and transverse connector constructs. Nine lateral mass fractures with transverse atlantal ligament (TAL) avulsion injury and three 4-part fractures with TAL injury (two avulsion injuries, one TAL substance tear) were treated. Radiologic outcomes included the anterior atlantodental interval (AADI) in flexion and extension cervical spine lateral radiographs at 6 months and 1 year after treatment. CT was also performed to visualize bony healing of the atlas at 6 months and 1 year. Visual An-alog Scale (VAS) scores for neck pain, Neck Disability Index (NDI) values, and cervical range of motion (flexion, extension, and rotation) were recorded at 6 months after surgery. Results: The mean postoperative extension and flexion AADIs were 3.79±1.56 (mean±SD) and 3.13±1.01 mm, respectively. Then mean AADI was 3.42±1.34 and 3.33±1.24 mm at 6 months and 1 year after surgery, respectively. At 1 year after surgery, 11 patients showed bony healing of the atlas on CT images. Only one patient underwent revision surgery 8 months after primary surgery due to nonunion and instability findings. The mean VAS score for neck pain was 0.92±0.99, and the mean NDI value was 8.08±5.70. Conclusion: C1 motion-preserving direct internal fixation technique results in good reduction and stabilization of unstable atlas fractures. This technique allows for the preservation of craniocervical and atlantoaxial motion.