Abstract
Pedicle screws give the best bone purchase of all posterior fixation techniques of the cervical spine, which would suggest a frequent utilisation. However, the cervical pedicles are small and the potential danger of misplacing a screw limits their use. In in vitrostudies the misplacement frequency has been shown to be unacceptably high, whereas this is not seen clinically, maybe due to different insertion techniques. Fortunately a misplaced screw rarely leads to a clinical complication.
To minimise the risks, however, we now only use pedicle screws in the cervical spine where stability is critical, i.e. at the extremes of a fixation. For example: A C1–C2 fixation in rheumatoid arthritis or in fracture of the dens would utilise C2–C1 transarticular screws (i.e. C2 pedicle screws). A cranio-cervical or cranio-thoracic fixation would involve 1 or 2 levels of pedicle screws as distal anchorage, and lateral mass screws in between. A short cervical fixation with pedicle screws could be in a trauma patient where it would be desired to have a very reliable fixation with a minimum number of fixation levels.
Computer navigation is a promising technique, however, not free from misplaced screws. So far we have experience of 83 navigated screws in 18 patients evaluated with postoperative computed tomography (CT). 67 screws were in correct position, 11 had insignificant breach fractures of the pedicle wall, whereas 4 were incorrectly placed, usually laterally into the foramen for the vertebral artery, none however with a clinical consequence. The main problem with computer navigation in the c-spine seems to be to obtain a good enough CT scan to allow good matching between the virtual and real worlds.
Theses abstracts were prepared by Professor Dr. Frantz Langlais. Correspondence should be addressed to him at EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
