Craniocervical fixation using inside-outside instrumentation

The clinical knowledge of biomechanics of atlantoaxial complex demonstrated that progressive instability tipically occurs after anterior decompression of the craniocervical junction. We report the so-called inside-outside technique for occipitocervical fixation, originally described by Pait et al. applied in two patients. One patient with rheumatoid artrhitis underwent a transoral resection of basilar invagination; in another case the craniocervical junction instability was due to the presence of tumor. The "inside-outside" occipitocervical fixation technique consists in the use of a titanium rod bended according with occipital cervical angle, placed and fixed laterally over the cervical spine. The rod is fixed to the occipital bone using a screw with the flat portion positioned onto the epidural space. In the cervical spine the rod is attached to transarticular screws placed at the superolateral quadrant of the articular mass. In the axis the screw is introduced through the pars interarticularis finishing at the axis body or the lateral mass of the atlas. In both patients, stabilization was achieved immediately. This technique proved to be safe and easily applied in the patients who developed instability in the craniocervical junction procedure.