The Anatomy of the Atlantoaxial Complex

Operating on the atlantoaxial complex has always posed a challenge to the surgeon because of the complex anatomy and biomechanics of this region of the spine. Recent developments and refinements of surgical techniques, which proffer better surgical outcomes for patients, require that surgeons gain a better understanding of the anatomy of this vital territory. For instance, the satisfactory application of new methods ofinternal surgical fixation, using refined implants, depends on the surgeon's thorough knowledge of not only the anatomy in the immediate surgical field, but also those structures that are not visualized, including those that will not be dissected during surgery. This is certainly the case with dorsal spinal fixation procedures such as transarticular screw fixation at CI-C2, or pedicular fixation at C2. To successfully address lesions of the posterior CI-C2 complex, the surgeon must appreciate the soft tissue elements, the bony architecture, and the physiologic mechanics of all structures incorporated in this unique segment ofthe human vertebral column.