Occipito-Cervical Fixation Techniques

Abstract

The principal indications for posterior occipito-cervical fusion can be grouped into C0-C2 trauma, tumors, congenital malformations of the occipito-cervical junction, and inflammatory diseases leading to atlanto-axial instability. Historically, in situ bone fusion, wiring techniques, and rod-loop constructs have been described. Contemporary techniques use occipital fixation plates connected to cervical rod-screw constructs. Proper prone positioning of the patient using a Mayfield clamp is crucial in order to provide a horizontal gaze. A fluoroscopic image is mandatory before surgery to verify that cervical alignment is obtained. The posterior approach is made from the external occipital protuberance to C4-C5. For occipital fixation, the plate is fitted to the occipital bone and screws are inserted into a drilled pilot hole. The bone is thickest in the midline and the ideal zone of screw placement is up to 2 cm lateral to the external occipital protuberance along the superior nuchal line. Screw depth can be measured preoperatively on computed tomography. Depending on pathologic findings, cervical fixation is usually achieved by C2 pedicle or isthmus screws and lateral mass screws at C3 or C4. A clamp construct using a supra-laminar hook at C3 and a sub-laminar hook at C4 represents a valuable alternative. The rod is contoured according to the sagittal posterior occipito-cervical angle (POCA) around 110° and fixed to the plate and cervical implants. Occipito-cervical fusion is best achieved by cancellous bone from the iliac crest. Local bone harvested from spinous processes combined with bone substitutes may be used as an alternative.