1 Introduction topenlarge
This procedure can be used to achieve additional stability in osteoporotic bone when odontoid screw fixation alone is insufficient.
It generally serves as an alternative to posterior C1-C2 fusion, in particular when prone positioning is contraindicated.
The advantage of this screw is that it requires less muscle dissection than a posterior trans articular screw.
2 Preoperative evaluation top
A preoperative CT image must be evaluated to determine if this screw is possible.
3 Approach topenlarge
When C1-C2 screws are used as an adjunct to odontoid screws, then these screws are inserted using the same approach as the odontoid screws.
If these screws are used as a stand alone procedure, the standard anterolateral approach to the cervical spine is utilized for the insertion of anterior trans articular C1-C2 screws.
4 Screw insertion topenlarge
Screw entry point
The starting hole for the screw is 7-8 mm distal to the C1-C2 joint.
It is 3-5 mm lateral to the medial boarder of the C1-C2 joint.
K-wires are inserted and directed approximately 30° laterally and 30° posteriorly across the joint.
Drill, tap, measure and insert the cannulated screws under fluoroscopic guidance (3.5 or 4.0 mm cortex screws, typically 15-20 mm long). The screw should not perforate the dorsal cortex of C1, nor should it violate the occipital cervical joint.
A radiolucent retractor is useful to visualize the joint.
K-wires are removed.