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Pipsa Ylanko, AOSpine Global Education Manager

General Editor: Luiz Vialle

Authors: Ronald Lehman, Daniel Riew, Klaus Schnake

Occipitocervical trauma - Odontoid, AAII Posterior C1-C2 fixation

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Glossary

Authors: Ronald Lehman, Daniel Riew, Klaus Schnake

1 Introduction top

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The posterior C1-C2 stabilization techniques are generally the biomechanically more stable ones.

The two main techniques are:

  • C1-C2 stabilization according to Goel-Harms
  • C1-C2 trans articular screw fixation according to Magerl

Both techniques can be combined with spondylodesis (fusion).

The choice between these two techniques will mainly depend on the following factors:

  • Local anatomy
  • Nature of the injury
  • Patient factors
  • Surgical skills

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Local anatomy

The trans articular screw is not indicated in patients with high riding vertebral artery.


Nature of the injury

Adequate screw purchase may not be achievable due to the fracture morphology for either of the screws.

Typically, if trans articular screws cannot be used, the Goel-Harms technique will be possible, and vice versa.

Trans-articular screws are not indicated if the fracture cannot be reduced anatomically.

With associated C1-C2 fractures, eg dislocated C1 burst fractures, the Goel-Harms technique may not be indicated.


Surgical skills

The choice of procedure will also depend on the surgeons familiarities with the two techniques.


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Patient factors

In young patients the Goel-Harms technique is favorable as the implants can be removed after fracture healing. The Magerl procedure on the other hand will damage the C1-C2 joint.

The Magerl procedure may prove difficult or impossible in patients with hyper kyphosis.


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Reduction

Prior to the surgical access the fracture should be reduced anatomically.

Anatomical reduction is essential for the success of the trans articular C1-C2 screw fixation. If this is not possible, the Goel-Harms technique should be used.

Reduction can be performed

  1. using halo traction preoperatively.
  2. intraoperatively using Mayfield clamp or a similar tool.
  3. pushing directly on the anteriorly displaced C1/2 segment through the mouth with the index finger in the case of a persistent anterior displacement.

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Approach

Prior to draping the patient for insertion of trans articular screws the location of the skin incision needs to be determined. This is done by placing a long K-wire along the side of the neck in the intended direction of the screw and viewing on the image intensifier.


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Fixation

One of the two following techniques is chosen:

  • C1-C2 trans articular screw fixation according to Magerl
  • C1-C2 stabilization according to Goel-Harms

2 Magerl technique top

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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.


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Pitfall: Too ventral an angulation of the screw can risk injury to the vertebral artery.

3 Goel and Harms technique top

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


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C1

C1 can be fixed using either lateral mass screws, which 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.


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C2

C2 can be fixed using either of the three techniques:


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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.


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Rod placement

Since there are only two screws on each side, a straight rod is placed to link the two and set screws are placed and tightened. Keep the rods as short as possible.


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In case the fracture is not reduced yet, reduction can be achieved by pulling C1 posteriorly.

4 Posterior fusion top

Fusion is typically indicated in:

  • elderly patients when implant removal is not planned
  • in complex injuries requiring a long time to heal

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Bone grafting following Goel/Harms technique

Fashion the bone graft as illustrated.


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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.


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


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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.


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


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


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


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Intra articular C1-C2 fusion

Alternatively (or additionally) the facet joints of C1-C2 can be opened, decorticated and fused.


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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, retract the C2 nerve cranially.


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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.

v1.0 2016.12.01