Posterior approach to C1-2

Position

  • Prone
  • Mayfield head rest with bed in reverse
  • Neck flexed to open up  C1 – 2

Landmarks

  • External occipital protuberance
  • Spinous process of C2

Incision

  • 7 cm Midline longitudinal incision
  • Start: Occipital protuberance

Internervous Plane

  • Paracervical muscles supplied by branches of left & right posterior primary rami

Superficial Dissection

  • Incise fascia & ligamentum nuchae
  • Cutting down onto the spinous process of C1 to C3
  • Reflect paraspinal muscles with Cobb Elevator
  • avoid lateral exposure beyond 1.5 cm on C1 ring to avoid vertebral artery & cervical ganglion

Deep Dissection

  • 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

  • Spinal cord
    • Never retract it
  • 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