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Chapter Summary
• Context: The upper cervical spine (occiput, atlas C1, and axis C2) possesses exceptional anatomical complexity and mobility, accounting for more than 50% of total cervical rotation and flexion-extension. Pathologies affecting this junction—such as traumatic fracture-dislocations (odontoid fractures, hangman fractures, atlantoaxial rotatory subluxation), congenital malformations (os odontoideum, basilar invagination), rheumatoid pannus destruction, and tumors—frequently cause catastrophic instability and brainstem or spinal cord compression. The historical evolution of upper cervical stabilization transitioned from posterior wiring (Gallie, Brooks-Jenkins) and halo vests to rigid transarticular screw fixation (Magerl) and modern segmented polyaxial screw-rod constructs (Goel-Harms C1 lateral mass–C2 pedicle fixation, C2 translaminar screws, and occipitocervical plating). Masterful execution of these techniques requires an intimate three-dimensional understanding of C1-C2 osseous landmarks and the intricate course of the vertebral artery.
• Chapter Objective: Detail the anatomical landmarks, surgical indications, biomechanical principles, and step-by-step techniques for upper cervical spine fixation. The reader will master C1 lateral mass screw placement, C2 pedicle/pars/translaminar screws, Magerl transarticular fixation, anterior odontoid screw osteosynthesis, and occipitocervical fusion, alongside vertebral artery protection and navigation protocols.
• Anatomy and high-risk neurovascular relationshipsThe craniovertebral junction houses the medulla oblongata, upper cervical cord, and the vertebral artery (V3 segment) coursing over the C1 posterior arch and through the C2 transverse foramen. High-riding vertebral artery or persistent intersegmental artery anomalies occur in up to 15-20% of patients, requiring mandatory preoperative CT angiography.
• Anterior odontoid screw fixationIndicated for acute Type II and high Type III odontoid fractures with intact transverse ligament in non-osteoporotic patients. Through an anterior retropharyngeal approach at C5-C6, one or two cannulated lag screws are driven along the midline into the odontoid apex, preserving normal C1-C2 rotational motion.
• Posterior C1-C2 fusion (Goel-Harms technique)The Goel-Harms construct utilizes C1 lateral mass screws coupled to C2 pedicle screws. Screws are inserted independently and connected with rods, allowing intraoperative reduction of atlantoaxial subluxation. It provides superior biomechanical rigidity without the rigid anatomical constraints of Magerl screws.
• C2 screw variations: Pedicle, Pars, and TranslaminarWhen a high-riding vertebral artery precludes safe C2 pedicle screw placement, C2 pars screws (shorter trajectory) or C2 crossing translaminar screws (Wright technique) provide strong bicortical fixation completely outside the vascular canal, eliminating vertebral artery laceration risk.
• Occipitocervical fusion (OCF)Indicated for occipitoatlantal dislocation, severe basilar invagination, and extensive craniocervical destruction. Rigid occipital plates secured with thick midline keel screws are connected to C1-C2 or subaxial screws. Head alignment in functional neutral (avoiding flexion or extension) is mandatory for horizontal gaze and airway patency.
• Complications and preventionVertebral artery laceration, spinal cord injury, C2 nerve root neuralgia, dural tear, loss of reduction, and hardware pullout are the main risks. Thin-slice 3D CT reconstruction, CT angiography, and intraoperative navigation or fluoroscopy are essential safeguards.
• Clinical Application: When assessing upper cervical instability, the surgeon must first determine whether motion-preserving anterior osteosynthesis (odontoid screw) or posterior arthrodesis (Goel-Harms) is indicated. In odontoid fractures, irreducible displacement, transverse ligament disruption, or severe osteopenia contraindicate anterior screw fixation and mandate posterior C1-C2 fusion. Preoperative CT angiography must be evaluated for high-riding vertebral artery (internal height <2 mm or isthmus width <5 mm at C2). If present, C2 translaminar screws should be selected instead of pedicle screws. Intraoperatively during Goel-Harms fixation, the C2 nerve root and associated venous plexus must be gently mobilized inferiorly to expose the C1 lateral mass entry point. In occipitocervical fusion, positioning must guarantee that the patient's chin-brow vertical angle is neutral to prevent postoperative dysphagia, airway obstruction, or downward gaze fixation.
