Posterior Approach to C1-2

Posterior midline exposure of C1 and C2 (A), followed by C1 lateral mass screws and C2 laminar screws (B) and bone graft laid over the poste
Posterior midline exposure of C1 and C2 (A), followed by C1 lateral mass screws and C2 laminar screws (B) and bone graft laid over the posterior arch of C1 and the C2 lamina (C). Image from Du HG, Trung NV, Hoang ND, Phuoc VX, Tan LD, Minh Duc T. Non-traumatic atlantoaxial dislocation co-existing with hypoplastic and high riding vertebral arteries, a case report and review of literature. Int J Surg Case Rep. 2026, 138(3), 614-620. CC BY 4.0.
Posterior Approach to C1-2, the atlas (first cervical vertebra), gray’s anatomy plate 86
The atlas (first cervical vertebra), Gray’s Anatomy plate 86. Image by Henry Vandyke Carter, Wikimedia Commons, Public domain.

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

Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.