Osteosynthesis of injuries and rheumatic or congenital instabilities of the upper cervical spine using double-threaded screws.

The surgical treatment of instabilities of the upper cervical spine, independent of their cause, requires the use of differentiated procedures if functional anatomy is to be largely restored. Successful procedures have been the diagonal screw fixation of the axis from the anterolateral aspect in case of acute fractures of the odontoid process, transpedicular screw osteosynthesis of C2 in hangman's fractures with bony instability, and the transarticular screw fixation of C 1/2 with interarcual fusion for atlantoaxial instabilities. Compared with conventional screws, the use of double-threaded screws which are almost totally imbedded in the vertebral body has the advantage of eliminating local irritation, reducing the risk of surgery, and simplifying the operative procedure itself.