Posterior Approach To C1-2

Posterior Approach to C1-2

– prone with Mayfield head rest or tongs & bed in reverse Trendelenberg (reduces venous pooling)
– midline incision from external occipital protuberance to C2 spinous process
– incise ligamentum nuchae & paravertebral muscles to expose posterior elements of C1-3
– avoid lateral exposure beyond 1.5 cm on C1 ring to avoid vertebral artery & cervical ganglion
– separate ligamentum flavum (posterior atlantoaxial ligament) from bone off the inferior aspect of C1
– separate posterior atlanto-occipital membrane from bone off superior aspect of C1
– never retract spinal cord at this level

Dangers:
– greater occipital nerve (C2) – runs beneath & over inferior oblique muscle laterally
– suboccipital nerve (C1 – motor only) – runs within suboccipital triangle laterally
– 3rd occipital nerve (C3) – lateral to suboccipital triangle
– vertebral artery – passes from transverse foramen of atlas immediately behind atlanto-occipital joint & pierces lateral angle of posterior atlanto-occipital membrane