C2 pedicle screw and plate combined with C1 titanium cable fixation for the treatment of atlantoaxial instability not suitable for placement of C1 screw.

STUDY DESIGN

A method of atlantoaxial stabilization using individual fixation of the C1 posterior arch and the C2 pedicle with C2 pedicle screws and plates combined with C1 titanium cables is described. In addition, the clinical results of this method on 8 patients are described.

OBJECTIVE

To describe the method and the clinical and radiographic results for posterior C1-C2 fixation with a combined implant system.

SUMMARY OF BACKGROUND DATA

Stabilization of the atlantoaxial complex is a challenging procedure because of the unique anatomy of this region. Fixation by plate or rod and C1 and C2 screw and structural bone grafting leads to excellent fusion rates. The technique is technically demanding and has a potential risk of the injuries to the vertebral artery, the internal carotid artery, spinal cord, and hypoglossal nerves. In addition, how to stabilize the atlantoaxial complex in the cases not suitable for placement of C1 screw is not described in the literature. To address these limitations, a method of C1-C2 fixation has been developed: bilateral insertion of C2 pedicle screws and rolling of C1 titanium cable through the posterior arch of atlas and the cranial hole of the plate, followed by C1-C2 plate fixation.

METHODS

From February 2003 to March 2006, 8 patients with atlantoaxial instability and not suitable for placement of C1 screw were included in this study: 5 cases of broken C1 pedicle screw trajectory and 3 cases of C1 anatomic anomalies. Skull traction was performed in each patient preoperatively. The pedicle screws were inserted into C2 pedicles in the direction as its axis. C1 titanium cable was rolled superior to lower through posterior arch of atlas in the cases not suitable for placement of C1 screw. The C1-C2 plate was slightly bent to fit the upper cervical contour. Hyperflexion alignment of the atlantoaxial complex was corrected by application of extension force created by tightening of the nut on the pedicle screws and the C1 titanium cable, which was passed through the cranial hole of the plate. Morselized autogenous cancellous iliac grafts were placed on the surface of the posterior arches of both atlas and axis. All patients were assessed clinically for neurologic recovery by Odom's method.

RESULTS

There were 5 males and 3 females with a mean age of 37.8 years (range, 17 to 59 y). There were 2 cases of old odontoid fracture, 2 cases fresh odontoid fracture (Aderson II C), 2 cases atlas transverse ligament laxation, 2 cases atlas transverse ligament rupture, and in these cases, 5 cases had failed placement of C1 screw because of broken C1 pedicle screw trajectory and 3 cases not suitable for placement of C1 screw because of anatomic anomalies. There were no spinal cord and vertebral artery and nerve injury after surgery. Follow-up duration was from 18 to 55 months with the average of 29 months. The plant bones all fused and there were no internal fixation rupture and mobility. All the patients showed improvement.

CONCLUSIONS

C2 pedicle screw and plate combined with C1 titanium cable could be used to treat atlantoaxial instability in the cases not suitable for placement of C1 screw.