12: Cervical Spine: Lateral Mass Screw Fixation

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Procedure 12 Cervical Spine

Lateral Mass Screw Fixation

Kern Singh, Jonathan A. Hoskins, Vamshi Yelavarthi, Alexander R. Vaccaro

Indications

image Acute and chronic instability

• Posterior element fractures
• Posterior ligamentous injuries
• Postlaminectomy instability

image Destruction of bony anatomy secondary to neoplasm

image Stabilization after multisegment anterior decompression and fusion (long anterior fusions for tumor, infection, ankylosing spondylitis, diffuse cervical spondylosis)

image Stabilization after failed cervical arthroplasty

image Pseudarthrosis following anterior cervical fusion

Indications Pearls

• Beware of patients with aberrant bony anatomy making screw placement difficult, such as those with erosive rheumatoid arthritis or osteoarthritis, or ectatic coursing of the vertebral artery.

Indications Controversies

• In severe osteopenia/osteoporosis, lateral mass fixation may be inadequate. It may be supplemented with posterior wiring if posterior elements are present and/or with pedicle screw fixation if the anatomy allows.

Examination/Imaging

image Fine-cut (2-mm) computed tomography with two-dimensional reconstruction allows assessment of the lateral mass quality in the lower cervical spine.

image T2-weighted sagittal magnetic resonance imaging may allow identification of neural compression and determination of the vascular anatomy (Figure 12-1).

image

FIGURE 12-1

Treatment Options

• Posterior wiring

• Posterior hook fixation

• Posterior cervical pedicle screw fixation

Surgical Anatomy (Figure 12-2)

image Nerve root injury may occur if the screw trajectory is incorrect, if the screw penetration is too deep (bicortical screw purchase), or if there is significant past pointing of the drill.

image Vertebral artery injury is an exceedingly rare complication that may occur if the trajectory is medial and the screw penetration is too deep.

image If brisk, pulsatile arterial bleeding is encountered from the drill hole, hemostasis should be obtained using bone wax, thrombogenic agents, and, potentially, placement of a screw in the hole. Postoperative angiography should be obtained to determine the status of the injured vertebral artery.

image

FIGURE 12-2

Positioning

image Mayfield tongs are applied, rigidly fixing the head to the table in the prone position (Figures 12-3 and 12-4).

image The neck is slightly extended. If this compromises spinal canal patency to a detrimental degree, lordosis may be obtained following decompression by having an unscrubbed assistant readjust the head holder to improve cervical lordosis.

image The arms and elbows are placed adjacent to the torso and are well padded to prevent pressure ulcers.

image The shoulders are gently pulled caudad by adhesive tape.

image The knees are flexed to prevent distal migration of patient.

image

FIGURE 12-3

image

FIGURE 12-4

Positioning Pearls

• A slightly reverse Trendelenburg position allows venous drainage and less bleeding during surgery.

Positioning Pitfalls

• Extreme flexion or extension of the head should be avoided to prevent fusion of the neck in a nonanatomic position.

Positioning Equipment

• Mayfield tongs

• Lateral plain radiography to visualize cervical alignment

Positioning Controversies

• Placing instrumentation without appreciating cervical alignment may lead to loss of horizontal gaze, or the need for compensatory mechanisms to maintain horizontal gaze, in the postoperative period.

Portals/Exposures

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