OrthoNet

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