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Authors of section


Ronald Lehman, Daniel Riew, Klaus Schnake

General Editor

Luiz Vialle

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Posterior C1-C2 fusion

1. Introduction

C1 and C2 are anatomically unlike any other vertebrae in the spine. Their unique anatomy allows for 50% one's flexion-extension motion at the occipital C1 joint and 50% of one's rotational motion at the C1-C2 joint. Consequently, they are the most important vertebrae for cervical range of motion.

When treating fractures of these two vertebrae, every effort should be made to avoid arthrodesing these two joints.

The goals of treatment are to stabilize the spine until the fractures have healed or to perform an arthrodesis in cases where stability cannot be achieved after healing is completed (such as with ligament ruptures).

If closed reduction and immobilization is not possible, one should consider open reduction and internal fixation followed by subsequent removal of instrumentation for cases that will become stable once the fractures have healed.

The vertebral artery trajectory must be fully evaluated prior to any surgery in this area.

anterior c1 c2 trans articular screws

Dislocated lateral mass fractures

This occurs when both the anterior and the posterior C1 arches are fractured, resulting in a "floating" lateral mass. These cannot be reduced closed and requires an open reduction followed by internal fixation.

posterior c1 c2 fusion

With acute fractures reduction is usually not difficult. With chronic fractures, one can manipulate this fractured fragment by placing a lateral mass screw into it and using it as a "joystick".

c1 lateral mass screws

While all techniques are possible for this fracture, if a C1 lateral mass screw can be placed lateral to the fracture line, it can aid in the anatomic reduction of the displaced fracture, which minimizes the risk of posttraumatic arthritis.

posterior c1 c2 fusion

In rare cases, the transverse atlantal ligament remains intact. If the fracture fragments can be reasonably closely realigned such that healing is likely, internal fixation without arthrodesis followed by subsequent removal of instrumentation can be performed.

posterior c1 c2 fusion

Bilateral C1 lateral mass screws compressed together with a rod is the preferred choice.

If the transverse atlantal ligament is ruptured, a C1- C2 arthrodesis must be performed.

posterior c1 c2 fusion

2. Approach and positioning

This procedure is performed through a posterior approach with the patient placed in the prone position.

posterior fixation

3. Wires and structural bone grafts

The oldest technique involved wires and structural autograft. This is rarely used and will not be described here.

posterior c1 c2 fusion

4. Magerl technique

Magerl first described the use of trans articular screws. This is a relatively simple and inexpensive way to fixate the C1-C2 joint. The disadvantage is that screw insertion requires fluoroscopy. Furthermore, the C2 pars must be large enough to accommodate a 3.5 mm diameter screw.

trans articular screw insertion

5. Goel and Harms technique

Goel and subsequently Harms described the use of C1 lateral mass and separate C2 fixation techniques.

posterior c1 c2 fixation


C1 can be fixed using either lateral mass screws that start just caudal to the posterior arch or that start on top of the posterior arch and then capture the lateral mass. The latter can only be used if the posterior arch is thick enough to allow for the screw.

occipitocervical fusion screw fixation


C2 can be fixed using either of the three techniques:

occipitocervical fusion screw fixation

Be aware that some posterior arches have a ponticulus posticus that appears to be a thick posterior arch, but in fact is a small bridge of bone that overlies the vertebral artery.

posterior c1 c2 fixation

This X-ray shows the ponticulus posticus.

posterior c1 c2 fusion

Rod placement

Since there are only two screws on each side there is no need for rod bending. A straight rod is placed and tightened. Keep the rods as short as possible.

posterior c1 c2 fixation

If there is spreading of the ring of C1, or a laterally displaced intra articular fracture, one can use the C1 lateral mass screws to reduce the displacement. After placement of bilateral C1and C2 screws and rods, one can place a cross link and compress the rods together, thereby reducing the fracture.

posterior c1 c2 fusion

An alternative in patients who have an anatomic reduction of the lateral mass fracture, but in whom C1 lateral mass fixation is not possible, one can instrument up to the skull but only fuse the C1-C2 joint. Once the fractures have healed, the instrumentation can be removed.

posterior c1 c2 fusion

6. Posterior fusion

Cancellous allograft placed dorsally over the lamina does not work in the vast majority of cases and should be avoided. One can place cancellous allograft intra-articulary after decorticating.

To decorticate the joint, reflect the C2 nerve cranially.

posterior c1 c2 fixation

Burr into the joint or use a curette to scrape the articular cartilage. Be aware that the vertebral artery can in some cases be just below the articular surface of C2. This can be verified by CT scan.

anderson dalonzo type iii

If an intra-articular fusion is not performed, one must use a structural cortical cancellous graft to bridge the C1 posterior arch to the C2 lamina. Auto iliac crest bone graft is the most reliable.

posterior c1 c2 fusion

Bone grafting following Goel/Harms technique

Fashion the bone graft as illustrated.

posterior c1 c2 fixation

If a Goel/Harms technique has been used, place a wire under the left rod over the graft and under the right rod and cinch it in place to push the graft onto the decorticated C1 posterior arch and C2 lamina.

posterior c1 c2 fixation

Add additional cancellous autograft strips to fill the voids between the lamina of C2 and the structural autograft.

posterior c1 c2 fixation

Bone grafting following trans-articular screw insertion

The bone graft is identical as for the Goel/Harms technique, but the wiring technique differs. Since there are no rods, the graft is secured with wires. A loop of wire is passed under the arch of C1, and the two free ends are passed through this loop.

posterior c1 c2 fixation

A second wire is passed through the spinous process of C2.

posterior c1 c2 fixation

After decorticating the C1 posterior arch and the C2 lamina, the graft is placed and the two wires are twisted together over the graft.

posterior c1 c2 fixation

Add additional cancellous autograft strips to fill the voids between the lamina of C2 and the structural autograft.

posterior c1 c2 fixation

7. Aftercare

Patients are made to sit up in the bed on the evening following the operation.

A collar is commonly used following surgical stabilization to moderate patient activity.

The purpose of a collar is to prevent ranges of motion outside of limits deemed unfavorable for fracture healing. Collar is optional.

Patients with intact neurological status are made to stand and walk on the first day after surgery. Patients can be discharged when medically stable or sent to a rehabilitation center if further care is necessary. This depends on the comfort levels and presence of other associated injuries.

Patients are generally followed with periodical x-rays at 6 weeks, 3 months, 6 months, and 1 year.