Craniocervical fixation, instrumentation or occipitocervical fusion refer to surgical fixation techniques with the goal to stabilize the craniocervical junction.
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Indications
Craniocervical fixation is indicated in the setting of craniocervical instability including 2,3:
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iatrogenic craniocervical instability after surgical decompression
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neoplastic invasion of the craniocervical junction
spinal metastases, chordoma or other extradural tumors
intradural tumors requiring spinal decompression
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inflammatory arthritis (e.g. rheumatoid arthritis)
atlantoaxial subluxation where atlantoaxial fixation is not feasible
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traumatic injury to the craniocervical junction
atlantooccipital and atlantoaxial dislocations
complex C2 fractures
Contraindications
Contraindications occipitocervical fixation include:
extensive occipital destruction
active local infection
A relative contraindication is an aberrant or unilateral vertebral artery with an increased operative risk of injury.
Procedure
The surgical procedure usually involves a posterior approach and application of various interfaces including occipital-plate-screw-rod, occipital-wire-rod-screw or occipital-hook-clamp-rod-screw systems 1-3:
an incision from the inion to the caudal vertebral body and splitting of the occipital muscles
dissection of the occipital and paraspinal muscles away from the spinous processes and laminae
occipital plate fixation close but caudal to the external occipital protuberance
alternatively burr hole drilling with wire or hook placement
variably occipital condyle screw placement
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posterior cervical screw fixation
atlas lateral mass screw insertion
axis pars screw, pedicle screw or laminar screw insertion
occipitocervical alignement and rod contouring
rod insertion and occipital fixation with plate-screw, rod-wire or rod-clamp interface
variably decortication and bone graft placement
An alternative approach is an atlantooccipital condyle screw placement with a screw trajectory from the midpoint of the atlas lateral masses to the midpoint of the occipital condyles at a 10-20° medial angulation 1,2.
Complications
Complications of craniocervical fixation techniques include complications of spinal surgery and the following 1-4:
dural leak/pseudomeningocele
suboccipital hematoma
brainstem injury
nerve root injury
injury to the vertebral artery
Radiographic features
Plain radiograph
Plain radiographs can assess implant position and vertebral alignment.
CT
In addition to the exact position of implants, CT might detect upper cervical and intracranial complications and characterize bony fusion.
MRI
MRI can be used to evaluate the spinal canal and posterior cranial fossa in the setting of suspected complications 1.
Radiology report
The postoperative radiological report should include a description of the following features:
implanted hardware
bone grafts if present
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position of screws especially in relation to the following structures
complications
Outcomes
Occipitocervical fusion leads to reduced mobility in the atlantooccipital and atlantoaxial joints with restriction in inclination, reclination and cervical rotatory capacity.
History and etymology
An occipitocervical fusion with fibular only bone graft was already described by Forrester in 1927 1,2. Several different bone graft techniques with and without wiring have been described later 1.
A rod-wire technique has been described by Sonntag and Dickmann 1993 and an inverted hook-clamp system was introduced by Faure in 1998 1,2. Rod-screw systems extending to the occiput have been described in the late 90s of the last millennium 1-4.
Transarcticular atlantooccipital condyle screw fixation has been introduced by LF Gonzalez and colleagues in 2003 1,5.
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