C1-C2 Posterior Cervical Fixation by a Harms Technique Modification

Abstract

Introduction:The unique anatomy of the upper cervical spine in conjunction with its supportive role in the axial stabilization and rotatory function of the head increases the surgical risk and associated complications for corrective surgeries performed in this spinal region. C1-C2 posterior fixation is indicated in the occurrence of instability at the craniocervical junction; and it can be performed by specific surgical techniques, such as the Harms and Magerl techniques. In this technical note, the authors present a simplified modification of the Harms technique that increases the accuracy of screw placement in the lateral mass of the C1 vertebra and in the pedicle of the C2 vertebra. This modification provides a secure path for screw placement by obtaining fluoroscopic images of K-wires inserted in the lateral masses of C1 and the pedicles of C2 as in the original technique. According to this technique, a pin driver is used to guide a K-wire through the initially marked entry point to the lateral mass of C1. After fluoroscopic confirmation of the optimal position of the guide wire, a cannulated hand drill is placed over the guidewire. A pilot hole is drilled in the same trajectory for the screw placement under fluoroscopic control. Then the guidewire and the hand drill are removed and an appropriately sized 3.5 mm polyaxial screw is placed with a hand drill under confirmation of the correct position with anteroposterior and lateral fluoroscopy. The same procedure is followed for the placement of the C2 pedicle screws. Then, a small rod is placed and secured within the polyaxial screw heads of the C1 and C2 screws bilaterally. Decortication of the spinous processes of the involved vertebrae and the occiput is the final step before closure of the fascia, cervical muscle layer, subcutaneous tissue, and skin.