Posterior Fixation of the Craniovertebral Junction in Nontraumatic Instability

Abstract

The craniovertebral junction is the region of the spine with the highest local mobility. With 40° of unilateral axial rotation, the C1–C2 joint is crucial for everyday head rotation. The large diameter of the upper spinal canal allows any physiological movement without compromise of the spinal cord. Strong ligaments like the transverse ligament of C1 and the alar ligaments of C2 combined with strong joint capsules ensure that the bony elements stay in position. When this system is disturbed, acute as well as chronic irritations of the spinal cord can cause neurological disturbances up to a transverse spinal cord syndrome. In most cases, instability triggers these symptoms. A minor symptom, indicating malfunction of the upper cervical spine, is neck pain, which can extend up to the occiput. Insufficiency of the transverse ligament, for example, in rheumatoid arthritis raises the risk of spinal cord compression during flexion of the cervical spine. Progressive destruction of C0–C1–C2 joints can be followed by a compressive myelopathy or a basilar invagination. Further nontraumatic causes of malfunction in the craniovertebral junction are congenital or developmental malformations, tumors, and infections or degenerative diseases.