Craniovertebral junction: biomechanical considerations.

The craniovertebral junction is a complex region that incorporates the occiput-C1-C2 portions of the spine. It is a transition between the cranium and the mobile cervical spine that permits significant motion. The motions afforded and the anatomy are vastly different at the occiput-C1 and C1-C2 articulations. These differences make treating pathology in this region very difficult. Problems include bony fixation of the cranium and the cervical spine (specifically C1 and C2), which limits complex motions, and limited bony sites available for arthrodesis. A thorough knowledge of the normal anatomy and biomechanics is required for fixation of this region. Moreover, an understanding of pathologic motions and the biomechanics of fixation is needed for successful construct design and good patient outcome.