Authors of section

Authors

Ronald Lehman, Daniel Riew, Klaus Schnake

General Editor

Luiz Vialle

Open all credits

Occipitocervical fusion (screw fixation)

1. Introduction – Occipitocervical injury

Occipital condyle fractures are only treated operatively in very rare cases. The main indications are:

  • Neurologic deficit
  • Instability
  • Patients with chronic pain
occipitocervical fusion screw fixation

Chronic pain

These injuries are initially treated with a collar or a halo vest. If chronic plain persist (particularly for type C injuries) occipito-cervical fusion is performed.

occipitocervical fusion screw fixation

Neurologic deficit

There may be associated paralysis of the cranial nerves, especially the hypoglossal nerve.

Instability

The following points are generally considered as criteria for occipitocervical instability:

  • > than 8° axial rotation to one side
  • > than 1mm C0-C1 translation

2. Appraoch and positioning

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

posterior fixation

3. Occipital fixation

Occipital plate

There are several plate systems available for the occiput (examples shown on the left). Their application is based on the same principles and to illustrate these concepts, we will show the use of plate placed in the midline which allows for modularity and rotation when connecting to the rods.

atlanto occipital dissociation

If plates are not available, wiring techniques may also be used. These will not be described in detail here.

occipitocervical fusion screw fixation

Plate placement

Independently of the plate system used, its placement should be close to but still caudal to the external occipital protuberance (EOP).

Placement of the plate at the EOP will increase the risk of erosion of the skin.

A too caudal position may compromise the foramen magnum.

occipitocervical fusion screw fixation

Screw placement

The thickest part of the cranium is the dense ridge which runs vertically in line with the internal occipital crest.

The thickness of this crest is 11.5-15 mm in males and 10-12 mm in females, and provides the best bone stock for screw purchase.

As you move laterally this crest becomes thinner and around 7-8 laterally to the midline, the bone thins out to a thickness of only 5-6 mm.

occipitocervical fusion screw fixation

Another landmark with thicker bone is the superior nuchal line which runs horizontally.

occipitocervical fusion screw fixation

An occipital condyle screw may provide added stability in cases where additional occipital or skull fixation is needed (skull fracture).

occiput condyle screw insertion

4. Plate application

Preparation of plating site

The occiput bone is dissected up to the external EOP and laterally as far as needed to accommodate the plate.

occipitocervical fusion screw fixation

Landmarks

The following landmarks are identified;

  • EOP
  • Superior nuchal line
  • Caudal aspect of the occiput (foramen magnum)
occipitocervical fusion screw fixation

Neurological deficit

In cases of neurologic deficit or when decompression is indicated, the posterior arch of C1 is now removed.

occipitocervical fusion screw fixation

The midline of the posterior aspect of the skull which is in line with the EOP is identified.

The plate is placed centered in the midline on the posterior aspect of the occiput. This allows for optimal placement, sizing and shape of the plate.

occipitocervical fusion screw fixation

Once the optimal plate is chosen, the location of the central cranial screw entry point is marked with the plate in place.

occipitocervical fusion screw fixation

The drill guide is set to 8 mm (female) or 10 mm (male) and the central cranial screw hole drilled.

occipitocervical fusion screw fixation

The screw hole is palpated to verify that the anterior cortex is still intact.

occipitocervical fusion screw fixation

If intact, additional drilling in 2 mm increments is performed until the anterior cortex is penetrated.

occipitocervical fusion screw fixation

A screw of appropriate length is inserted through the plate into the predrilled hole.

occipitocervical fusion screw fixation

After insertion of the first screw, there is enough flexibility in the system to allow for adjustments. Ensure the plate is flush with the skull and that it is level.

occipitocervical fusion screw fixation

The remaining screws are then inserted with the same drill technique as for the first screw ensuring bicortical purchase in the order 2-5.

However, care is taken during drilling of the lateral holes (2 and 3) as the bone will be thinner than in the midline (4 and 5).

occipitocervical fusion screw fixation

When additional occipital or skull fixation is needed, an occipital condyle screw is now inserted.

occipitocervical fusion screw fixation

5. Cervical screw fixation

C1 fixation

For C1 fixation, C1 lateral mass screws can be used.

occipitocervical fusion screw fixation

C2 fixation

For C2 fixation the following options are available:

A consideration is given to use pedicle or interlaminar screws when doing an occiput to C2 fusion as oftentimes the starting point for the pars screws may compromise the facet joint.

occipitocervical fusion screw fixation

6. Alignment in the occipital cervical region

If there is a preoperative X-ray available the surgeon can use this as a guide to properly align the occipito cervical junction during fusion. Ideally proper alignment allows for horizontal gaze.

7. Rod contouring

When the correct alignment is verified, rods are temporarily placed.

Some systems have the advantage of rod with a ball point which allows for easier placement and contour of the occipito cervical region (which can be relatively difficult when bending straight rods to the proper contour). If these rod-screw systems are not available a standard rod can be bent.

occipitocervical fusion screw fixation

8. Decortication

Prior to final placement of the rods, decortication of lamina facets, and posterior aspects of the skull is performed.

occipitocervical fusion screw fixation

When using intralaminar screw fixation at C2, care must be taken not to decorticate deeply which might compromise screw fixation.

occipitocervical fusion screw fixation

9. Fusion

Rod insertion

The rods are inserted.

occipitocervical fusion screw fixation

Bone grafting

There are several options for bone grafting material including:

  • Autograft (iliac crest cancellous bone)
  • Allograft (cortico cancellous or cortical onlay graft).
  • Local bone
  • Various biomaterials

Bone grafting material is placed against the decorticated dorsal elements of the spine.

occipitocervical fusion screw fixation

Transverse rod connectors may be used to enhance axial stability and help hold cortical-onlay graft in place.

atlanto occipital dissociation

10. 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.