Chapter Clinical Summary
Academic synthesis, diagnostic methodology, and surgical recommendationsPosterior cervical spine fixation is a critical surgical tool for restoring multiplanar stability in traumatic fracture-dislocations, multi-level compressive myelopathy, severe cervical deformity, post-laminectomy kyphosis, tumors, and revisions. The evolution of posterior cervical instrumentation transitioned from early interspinous wiring (Rogers, Bohlman) and interlaminar clamps to contemporary lateral mass screw fixation (Roy-Camille, Magerl, Anderson, An) and subaxial cervical pedicle screws. Lateral mass screw-rod systems provide reliable three-dimensional stability with a high safety margin regarding the vertebral artery and exiting spinal nerves. For severe instability, high biomechanical demands, osteoporotic bone, or cervicothoracic junction reconstructions (C7-T1), subaxial pedicle screws offer superior pullout strength and rotational control. Masterful execution requires deep anatomical comprehension of lateral mass quadrants, pedicle trajectories, and the neighboring vertebral artery and nerve roots.
Detail the anatomical landmarks, biomechanical foundations, and step-by-step techniques for posterior cervical fixation (lateral mass screws, subaxial pedicle screws, translaminar screws, and cervicothoracic junction constructs). The reader will master Roy-Camille, Magerl, Anderson, and An lateral mass trajectories, understand pedicle screw insertion protocols and navigation, and prevent neurovascular complications.
The subaxial lateral mass is bounded medially by the lamina-facet junction, laterally by the lateral edge, superiorly by the superior facet joint, and inferiorly by the inferior facet joint (Figure 76.1). The exiting nerve root passes anteroinferiorly over the transverse process, and the vertebral artery courses in the transverse foramen directly anterior to the lateral mass.
Multiple trajectories have been developed to maximize bone purchase while avoiding neurovascular injury. Roy-Camille: entry at the center of the lateral mass, directed straight anteriorly with 10° lateral angulation. Magerl: entry 1-2 mm medial and superior to the center, directed 25°–30° cephalad and 25° lateral parallel to the facet joint. Anderson: entry 1 mm medial to center, directed 30°–40° cephalad and 10° lateral. An: entry 1 mm medial to center, directed 30°–40° cephalad and 25°–30° lateral (maximizing nerve root protection).
Subaxial pedicle screws (especially at C7 and C6) provide exceptional pullout strength, critical for rigid deformity correction, osteoporosis, and bridging the cervicothoracic junction (C7-T1). Entry point is located at the superior-lateral margin of the lateral mass, angled 30°–45° medially in the axial plane and parallel to the superior endplate. Computer navigation or continuous fluoroscopy is strongly recommended due to proximity to the spinal cord and vertebral artery.
The transition from mobile, lordotic cervical spine to rigid, kyphotic thoracic spine creates immense cantilever stress. Constructs terminating at C7 carry higher failure rates; extending instrumentation into the upper thoracic spine (T1-T3) with robust thoracic pedicle screws prevents construct failure and junctional kyphosis.
Complications include vertebral artery laceration, nerve root injury (radiculopathy), spinal cord contusion, lateral mass fracture, screw loosening, and pseudarthrosis. Preoperative thin-slice CT planning, lateral angulation of lateral mass drills, and rigorous hemostasis ensure procedural safety.
In clinical practice, posterior cervical fixation is indicated when multi-level laminectomy or laminoplasty requires stabilization, in facet fracture-dislocations, or when anterior fixation alone is insufficient. When performing lateral mass screw fixation from C3 to C6, the Magerl or An trajectories provide superior nerve root and vertebral artery clearance compared to straight-forward trajectories. At C7, the lateral mass is often thin and transitional; placing a C7 pedicle screw provides far superior mechanical purchase. In constructs crossing C7-T1 into the thoracic spine, transitioning from 3.5 mm cervical rods to 5.5 mm thoracic rods via dual-diameter transition rods prevents rod fatigue fracture. Preoperative CT must be reviewed to measure pedicle diameter and lateral mass thickness, and to rule out vertebral artery anomalies.