Odontoid Screw Fixation and Anterior C1-C2 Fixation Techniques

Abstract

Until 1974 (according to Anderson and D’Alonzo’s work) most odontoid fractures and the instability of the upper cervical spine were treated through immobilization or posterior bone graft plus the wiring standard techniques (Gallie and Brooks-Jenkins method). On the other hand, transoral approaches were rarely considered as optional, due to the high complication rate. During the last two decades, better understanding of the anatomy and biomechanics of the C1-C2 complex, along with modern neuroradiology development (CT/MRI) defining vertebral artery trajectory and neural elements position, the study of bone, and ligamentous morphology have boosted a radical change in the surgical strategy.

Transverse fractures crossing the base of odontoid process near the junction of the axis body (type II according Anderson and D’Alonzo classification) are, especially in elderly patients, unstable with high risk of nonunion. The odontoid screw fixation is a minimally invasive procedure which allows early patient’s mobilization, an effective immediate stability with high fusion rates and a preservation of the C1-C2 segment motion. In addition to fractures that involve individually the atlas and axis vertebrae, combination fractures involving both can cause atlantoaxial instability. Atlantoaxial instability can be caused by several factors: traumas (fractures and luxations), neoplasms, malformations, inflammatory, and degenerative diseases. In order to achieve stability of the C1-C2 junction, atlantoaxial instability can be managed by a variety of different techniques: among them, the anterior C1-C2 transarticular fixation has proved safe and successful as the posterior fixation approaches, although less used by most spine surgeons.

The supine vs prone positioning with minimal soft tissue dissection make the anterior approach less traumatic. In this chapter we describe two surgical techniques that can be performed through an anterior approach: odontoid screw fixation and C1-C2 transarticular fixation.