ObjectiveTo investigate the clinical effects of posterior atlantoaxial fusion fixation in treatment of old atlantoaxial injury secondary to atlantoaxial dislocation.MethodsA retrospective analysis was carried out on 16 patients ( 14 males and 2 females) with old atlantoaxial injuries secondary to atlantoaxial dislocations managed with posterior atlantoaxial fusion fixation from March 2008 to March 2012.The time from injury to operation lasted for 3-36 months ( average 10.5 months).Posterior atlantoaxial transpedicular fixation was performed in 13 patients including 10 patients with old odontoid fractures and three with old traumatic transverse ligament disruptions of the atlas combined with atlantoaxial dislocations.Also,posterior atlantal arch transpediclar fixation combined with axial pedicle screw fixation was performed in three patients who had old odontoid fractures combined with atlantoaxial dislocations.All patients had simultaneous autogenous bone grafting between atlas and axis during reduction and fixation.The preoperative and postoperative Japanese Orthopaedic Association (JOA) scores were compared.Follow-up X-ray films and CT was performed to evaluate the atlantoaxial reduction and fusion.ResultsAll the patients were followed up for 9-18 months ( mean 13 months).None of the patients had spinal cord or vertebral artery injuries.Follow-up CT showed that two patients had partial penetration of one side axial pedicle screws into transverse foramen without nerve and blood vessel injuries.Clinical symptoms obtained different degree of improvement.The postoperative JOA scores ranged from 13 to 16 points ( mean 14.8 points) and the improvement rate of JOA was 71％-92％ ( mean 82％ ).The X-ray films and CT showed sound bone fusion,with good location of screws but with no signs of atlantoaxial instability or loss of reduction,or loosening or breakage of the screws.ConclusionPosterior atlantoaxial fusion fixation can effectively reconstruct atlantoaxial stability,improves neurologic function of spinal cord and has reliable curative effects.