Posterior C1-C2 fusion with polyaxial screw and rod fixation

Study Design. A novel technique of atlantoaxial stabilization using individ ual fixation of the C1 lateral mass The C2 pedicle with minipolyaxial screw s and rods is escribed. In addition, the initial results of this technique on 37 patients are described. Objectives. To describe the technique and the initial clinical and radiogra phic results for posterior C1-C2 fixation with a new implant system. Summary of Background Data. Stabilization of the atlantoaxial complex is a challenging procedure because of the unique anatomy of this region. Fixatio n by transarticular screws combined with posterior wiring and structural bo ne grafting leads to excellent fusion rates. The technique is technically d emanding and has a potential risk of injury to the vertebral artery. In add ition, this procedure cannot be used in the presence of fixed subluxation o f C1 on C2 and in the case of an aberrant path of the vertebral artery. To address these limitations, a new technique of C1-C2 fixation has been devel oped: bilateral insertion of polyaxial-head screws in the lateral mass of C 1 and through the pars interarticularis into the pedicle of C2, followed by a fluoroscopically controlled reduction maneuver and rod fixation. Methods. After posterior exposure of the C1-C2 complex, the 3.5-mm polyaxia l screws are inserted in the lateral masses of C1. Two polyaxial screws are then inserted into the pars interarticularis of C2. Drilling is guided by anatomic landmarks and fluoroscopy. If necessary, reduction of C1 onto C2 c an be accomplished by manipulation of the implants, followed by fixation to the. 3-mm rod. For definitive fusion, cancellous bone can be added. No str uctural bone graft or wiring is required. In selected cases, e.g., C1-C2 su bluxation or fractures in young patients in whom only temporary fixation is necessary, the instrumentation can be removed after an appropriate time. B ecause the joint surfaces stay intact, the patient can regain motion in the C1-C2 joints. Results. Thirty-seven patients underwent this procedure. No neural or vascu lar damage related to this technique has been observed. The early clinical and radiologic follow-up data indicate solid fusion in all patients. Conclusion. Fixation of the atlantoaxial complex using polyaxial-head screw s and rods seems to be a reliable technique and should be considered an eff icient alternative, previously reported techniques.