One stage atlantoaxial pedicle screw fixation for unstable atlas burst fracture

Objective To assess the clinical results of one stage posterior atlanloaxial pedicle screw fixation and fusion for unstable atlas burst fracture. Methods A retrospective analysis of clinical data including 32 cases, which were admitted according to the inclusion and exclusion criteria between May 2010 and December 2013. There were 11 females and 21 males whose age ranged from 22 to 59 years (mean 41.8 years). X-ray, CT scan reconstruction and MRI were done before operation to evaluate the injury of ligament and fracture. There were 17 cases of unstable atlas burst fracture,including 5 cases Jefferson fracture,8 cases untypical Jefferson fracture, and 4 cases lateral mass fracture combined with anterior arch or posterior arch fracture. There were 15 cases combined with axial fracture, 9 cases combined with dens fracture, 4 cases with axial body fracture, and 2 cases with Hangman fracture. The patients had various degrees of occipital neck pain, limited mobility and neurological dysfunction. Degree C in 1 case and degree D in 5 cases were assessed by the American Spinal Cord Injury Association (ASIA) impairment scale. All patients were treated with one stage posterior atlantoaxial pedicle screw fixation and fusion. All patients were assessed clinically by neurologic recovery, atlantoaxial reduc tion and bone graft fusion. The preoperative and postoperative atlanto-dens interval (ADI), lateral mass distance (LMD) and VAS were measured and statistically analyzed. Complications were observed. Clinical outcome of last follow-up was evaluated by dynamic X-ray and CT scan. Results All patients were followed up. The follow-up time ranged from 10 to 24 months (mean 15.6 months). The healing time of bone fusion ranged from 5 to 10 months with an average follow-up time of 6.9 months. The average preoperative VAS score was 5.0±1.4 while the score of last follow-up was 1.0±0.7, with statistically significant differences. Neurological status improved in all patients but one. Four cases with grade D improved to E, and one cases with grade C improved to D. Postoperative cervical spine X-ray and CT showed that the sagittal cervical spine alignment was restored. The preoperative ADI was 4.6±1.2 mm, which was statistically significant different with last follow-up the ADI of 2.4±1.0 mm. There were statistically significant difference between preoperative LMD of 5.6±2.2 mm and postoperative LMD of 1.2±1.0 mm. Conclusion The posterior atlantoaxial pedicle screw for unstable atlas burst fracture combined with atlantoaxial instability seems to be effective. It is technically demanding to place screw into thelateral mass of the atlas. Key words: Cervical atlas; Spinal fractures; Atlanto-axial joint; Joint instability; Spinal fusion