Neurosurgery notes/C3-C6 fixation

C3-C6 fixation

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Status
In progress
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Parent item
Cervical fixation

Indication

  • Instability due to
    • Surgical decompression
    • Trauma with bony or ligamentous instability,
    • Discitis/ osteomyelitis with instability and kyphosis,
    • Degenerative spine disease with kyphosis or anterolisthesis

CI

  • Soft CI: Osteoporosis use halo instead

Positioning

  • Montreol mattress and table in a reverse Trendelenburg position
  • Skull pins (e.g. Mayfield clamp)
    • Accurate positioning with intraoperative adjustment as required.
    • Avoids any pressure on the face or eyes
    • Affords the anaesthetist good access at all times
  • A slight degree of flexion will improve access and exposure but fixation in an unduly flexed position should be avoided.

Approach

  • Midline incision → avascular midline raphe is opened to the spinous processes → bilateral muscle stripping → expose the laminae and lateral masses
  • Further lateral screening is required to confirm the levels to be instrumented.
  • Define the lateral, superior, and inferior edges of each lateral mass:
    • The medial edge of the lateral mass is at the point where the lamina, sweeping downwards, ends, and there is a distinct change of contour.

Fixation method

Lateral mass screw

  • Most commonly used technique for posterior cervical fixation
  • Entry point
      • Surgeon’s view of the exposed lateral masses. The entry point is generally in the midpoint of the square or just inside the inferomedial quadrant (shaded).
      Surgeon’s view of the exposed lateral masses. The entry point is generally in the midpoint of the square or just inside the inferomedial quadrant (shaded).
      Schematic diagram demonstrating the appropriate screw trajectory on the axial (A) and sagittal (B) planes. On the axial plane, the surgeon must aim laterally enough to avoid the vertebral arteries (red) and on the sagittal plane, superiorly enough to avoid the exiting nerve root (yellow).
      Schematic diagram demonstrating the appropriate screw trajectory on the axial (A) and sagittal (B) planes. On the axial plane, the surgeon must aim laterally enough to avoid the vertebral arteries (red) and on the sagittal plane, superiorly enough to avoid the exiting nerve root (yellow).
  • Trajectory
    • Aim the hand drill laterally enough to avoid the vertebral artery in the foramen transversarium and to aim superiorly enough to avoid the exiting nerve root in the neural foramen
    • An angle of around 20° in both the axial and sagittal planes should be sufficient.
      • Often the correct trajectory in both planes involves the drill resting on the spinous process immediately inferior to the level which is being instrumented.
    • Use burr drill to break the cortex
    • Ball- tipped probe used to assess for possible breaches
  • Screw choice
    • Diameter: 3.5 mm
    • Length:
      • 14– 16 mm if unicortical fixation
      • Slightly longer if bicortical
  • Technique - Joaquim 2020
      • Technique
      Entry point
      Lateral angulation
      Sagittal angulation
      Riew technique (best-used by Ganga)
      1 mm medial and 1 mm caudal to the center of the lateral mass
      Aim toward the upper and outer corner of the lateral mass
      Aim toward the upper and outer corner of the lateral mass
      Roy-Camille et al.
      Center of the lateral mass
      10° lateral
      90° to the lateral mass surface
      Nazarian and Louis
      At the intersection of a vertical line 5 mm medial to the lateral edge of the facet joint, and a horizontal line 3 mm below the inferior edge of the facet joint line above
      Straight ahead, no lateral angulation
      90° to the lateral mass surface
      Magerl et al.
      1 mm medial and 1 mm cranial to the center of the lateral mass
      20–30° lateral
      Parallel to the adjacent facet joints
      Anderson et al. (modified Magerl et al.)
      1 mm medial to the center of the lateral mass
      10° from the sagittal plane
      30–40° cephalad (also parallel to the facet joints)
      An et al.
      1 mm medial to the center of the lateral mass for C3–6
      30° lateral
      15° cephalad
      Roy-Camille technique
      • (A) Entrance point: Midpoint of the lateral mass
      • (B) Lateral angulation: 10°
      • (C) Sagittal inclination: Screw inserted at 90° with the cortical surface of the lateral mass (perpendicular)
      notion image
      An technique
      • (A) Entrance point: 1 mm medial to the midpoint of the lateral mass
      • (B) Lateral angulation: 30°
      • (C) Sagittal inclination: Screw inserted at 15° with the cortical surface in a cephalad angulation
      notion image
      Magerl technique
      • (A) Entrance point: Slightly medial and cranial to the midpoint of the lateral mass
      • (B) Lateral angulation: 20° to 30°
      • (C) Sagittal inclination: Screw inserted parallel to the adjacent facet joints
      notion image
      Lateral mass screw fixation
      • Potential complications - injury of the vertebral artery
      • Ebraheim et al.
        • The relative positions between the transverse foramen and the posterior midpoint of lateral mass vary with different levels
        • The transverse foramens are anteromedial to the posterior midpoint of the lateral mass at C3–C5, and directly in front of the posterior midpoint of the lateral mass at C6.
      notion image

Pedicle screw

Technique
Entry point
Lateral angulation
Sagittal angulation
Abumi et al.
Starting slightly lateral to the center of the lateral mass and close to the inferior margin of the lower facet joint of the cranially adjacent vertebra
About 25° to 45° medially oriented
Parallel to the superior endplates for C5, C6 and C7 pedicles; slightly cephalad oriented for the C2, C3 and C4 pedicles
  • Entry point
    • Mediolateral:
      • 5mm lateral to the midpoint of the lateral mass.
      • Lee 2011: 2 mm directly medial to the lateral notch (LN)
      • Albumi 1997: 1/4 medial to the lateral border of the lateral mass at the facet joint edge
    • Cranio-caudal: as close to the facet joint line and sometime drilling into joint line is better.
  • Trajectory
    • Medially 40-60 deg
    • 90 degree to lateral mass surface
  • Adjunct option
    • C arm
      • Get an inline view by tilting the xray beam
    • O arm navigation
    • Drill the lamina to expose the medial pedicle wall
  • Note
    • Average pedicle width C3-C6: growing from 5 to 6mm
      • Provides 3.5 to 4 times the pullout resistance of lateral mass screws.
      • Challenging placement due to
        • Small pedicle diameter
        • Proximity to the vertebral artery.
notion image
LN: Lateral notch, CM: Central Mass.
LN: Lateral notch, CM: Central Mass.
 
Albumi entry
Albumi entry
 

Other steps

  • Rods
    • 3 mm diameter rods, cut and contoured to the desired length and shape are placed within the polyaxial screw heads on both sides.
  • Reduction of facet dislocations
    • From the back can usually be carried out under direct vision of the dislocation
    • Sometimes the inferior facet may need to be drilled off before reduction will occur.
      • Care should be taken to avoid damage to the nerve root.
  • Final tightening, final X- ray screening is performed.
  • Fusion
    • Decortication → placement of autologous/synthetic bone graft
    • Any fixation, no matter how expertly constructed, will ultimately fail unless bony fusion or indeed fracture union is achieved

Morbidity and mortality

  • Badiee 2020
    • Complication rate (15% to 25%)
      • Surgical site infections: 2.9–10.3 %
      • Neurologic deficit (overall): 8.5 %
      • C5 palsy: 6.7–9.5 %
      • Dural tear: 0.8–3.9 %
      • Adjacent segment pathology 3.4–17.6 %
      • PJK (proximal junctional kyphosis): 6.2–41.7 %
      • DJK (Distal junctional kyphosis): 23.8 %
      • Pseudarthrosis: 1.2–21.2 %

Images

notion image
notion image