Anterior C1-2 Fixation

Instability of C1-2 may be due to trauma, infection, tumors, or rheumatoid arthritis. In deciding the appropriate management of unstable C1-2 injuries, the patient’s age, medical status, and compliance—along with the fracture pattern and whether ligamentous injury is involved—must be considered. One treatment modality that is widely accepted is closed reduction with halo vest placement. This treatment can cause patient dissatisfaction, however, and lack of compliance may lead to infection at the pin site and loss of alignment.

Over the last decade, internal fixation has become a standard treatment for managing unstable C1-2. Posterior wiring techniques as described by Brooks and Jenkins and by Gallie have been widely used but have a significant rate of nonunion and fracture displacement. Posterior transarticular screw fixation, as later described by Magerl and Seeman, results in lower failure rates but is technically more demanding and has a high risk of inadvertent injury to the vertebral artery. Anterior C1-2 fixation may be used as an alternative method when posterior fusion is undesirable.

Anterior C1-2 fixation can be performed to treat C1-2 instability, which can result from trauma, infection, tumors, or rheumatoid arthritis, or unstable odontoid fracture, nonunion, or os odontoideum.

Patients requiring C1-2 fixation who are unable to tolerate the prone position for the duration of a surgery because of pulmonary issues opt for anterior C1-2 fixation. In addition, anterior fixation is performed if a patient has posterior arches of C1-2 that are injured and cannot hold hardware for stability or if a patient has atypical dorsal bony anatomy of C1-2 that thus precludes placement of posterior transarticular screws.

Finally, anterior C1-2 fixation can be performed as part of tumor resection involving the dens or to help correct basilar impression, which involves upward movement of the dens in response to softening of bones at the skull base and can cause atlantoaxial subluxation.

A number of factors hinder the success of anterior C1-2 fixation: the patient having a short neck, whether due to anatomic variation or due to diseases like Klippel-Feil syndrome, or the patient having a barrel-shaped chest, often due to respiratory conditions like chronic bronchitis or asthma.

In addition, fracture of bones of the face, temporomandibular pathology, or injury to anterior bony architecture all render a patient unable to hold the hardware involved in C1-2 fixation.

In deciding the appropriate management of unstable C1-2 injuries, considerations must include the patient’s age, medical status, and compliance. It is also crucial to understand the fracture pattern and to decipher whether ligamentous injury is involved.

Preoperative computed tomography (CT) should be reviewed to assess for adequate bony integrity of the lateral masses of C1 and the vertebral body of C2. Preoperative CT will also allow for selection of screws of appropriate length.

Closed reduction of the C1-2 segment may be adequately achieved with halo or Gardner-Wells tong traction.

The patient is positioned supine on a radiolucent table with the neck slightly extended. Proper positioning should be assessed with fluoroscopic guidance. The table may need to be rotated 180 degrees on its base to allow maximum room for fluoroscopic positioning.

The patient is intubated via awake fiberoptic technique, and broad-spectrum antibiotics with gram-positive and gram- negative coverage should be given 30 minutes before the incision.

Spinal cord monitoring is highly recommended and can be achieved by measurement of motor evoked potentials (MEPs) in combination with somatosensory evoked potentials (SSEPs) and comparison to baseline values.

A biplanar fluoroscope is brought around the operating table and covered with sterile drapes at the beginning of the case. When the fluoroscope is draped, it can be pushed toward the foot of the table and brought in to ensure adequate reduction and appropriate placement of hardware.