Surgical treatment with atlantoaxial pedicle screws for reduction of atlantoaxial dislocation caused by old odontoid fracture

English Keywords:Old odontoid fracture  Atlantoaxial dislocation  Screw  Fixation  Reduction

English Abstract:

  【Abstract】 Objectives: To summarize the clinical results of the posterior atlantoaxial pedicle screw-rod internal fixation with its intraoperative reduction and fusion in treatment of old odontoid fracture combined with unreducible atlantoaxial dislocation.　Methods: Twenty-one(8 females, 13 males) patients with an average age of 38.5(13-68) years at the time of injury between January 2007 and January 2010 were studied. The patients had various degrees of occipital neck pain, limited mobility and associated with neurological dysfunction. Degree B in 2 cases, degree C in 13 cases and degree D in 6 cases were assessed by the ASIA impairment scale. Japanese Orthopaedic Association(JOA) scores before operation were recorded from 4 to 14(mean, 8.3). Cervical spinal cord compression was showed by MRI examination in 18 patients, and intramedullary T2-weighted high signal change was found by MRI in 7 patients. All patients had anterior atlantoaxial dislocation, and underwent skull traction before operation. Fifteen cases were partially reduced(71.4%), and 6 not reduced at all(28.6％). The preoperative atlanto-dens interval(ADI) was from 9mm to 15mm(average 12.3mm). Patients were treated with posterior atlantoaxial pedicle screw-rod internal fixation with its intraoperative reduction and fusion. All patients were assessed clinically for neurologic recovery, atlantoaxial reduction and bone graft fusion. Results: No intraoperative vertebral artery injury and spinal cord injury were noted． A total of 84 pedicle screws was inserted. Postoperative CT reconstruction showed that 4 screw malpositions were noted， 3 of which penetrated lateral pedicle cortex but no vertebral artery injury confirmed by vertebral angiography, 1 penetrated medial pedicle cortex but no symptom of nerve root injury was found. 80 screws were sited completely in pedicle. All 21 patients were followed up for an average of 20 months(range, 6-36 months). Postoperative cervical spine CT and MRI showed that the sagittal cervical spine alignment was restored，cerebral spinal fluid line was clear in the odontoid process area and no spinal cord compression was found. The postoperative ADI was reduced to 2-4mm(average 2.8mm). Six months after surgery, all patients except 3 were substantially improved with degree C in 3 cases, degree D in 10 cases and degree E in 8 cases. JOA scores after operation were recorded from 10 to 17(mean, 14.6). The overall improvement rate was 81.2% on average. Solid bony fusion was achieved in 20 patients at 6 months after operation, but partial absorption of the bone graft occurred in one case. The rate of fusion was 95.2％, with no loosening, displacement, instability or breakage of the screws. Conclusions:　Good clinical results can be achieved by the posterior atlantoaxial pedicle screw-rod internal fixation with its intraoperative reduction and solid fusion.