Anterior fixation

Anterior fixation is a useful technique to achieve sufficient decompression and interbody fusion. It is the superior technique for restoring cervical lordosis.

Direct decompression from disk or bone material can be performed directly without mobilization of the neurological structures.

Visualization of the dura allows direct confirmation of complete decompression.

Nerve roots are better identified from a posterior approach, but experienced surgeons can also perform an anterior foraminotomy.

Pitfall: As the surgeon is placed lateral to the midline of the patient, the true midline may be difficult to recognize and there is a tendency to direct the decompression to the contralateral side as shown in the illustration. This may lead to an incomplete decompression.

To prevent this, verification of anatomical landmarks using intraoperative imaging may be useful.

Preoperative evaluation of potential anatomic variations in the course of the vertebral artery is mandatory. Unidentified anatomical variations may increase the risk of compromising the artery during decompression.

Indications for decompression during anterior reconstruction includes:

• The presence of a traumatic disc herniation causing neurologic injury (discectomy alone)
• The need to remove a portion or entire vertebral body followed by reconstruction for stability, or for relief of symptomatic neural compression
• Kyphotic angulation with ventral compression.

The procedure should be performed with adequate light and magnification; either loupes or a microscope.

Closed reduction is performed under image intensifier prior to skin incision. Extension or flexion is applied depending on the position of the fragments. This is followed by compression. Reduction should not include traction maneuvers.

This procedure is performed through the anterior approach with the patient placed in the supine position.

Prior to performing the discectomy, the level is confirmed with intraoperative fluoroscopy.

The following landmarks are identified:

• Midline
• Unciform process

The midline will dictate the AP orientation of the discectomy.

The unciform processes dictate the lateral borders of the discectomy, establishing the safe area from the artery. This will leave a 3mm safe zone to the normal anatomy of the vertebral artery.

A small (nr 15) blade is used to open the annulus from uncinate to uncinate as close as possible to the endplates.

Pearls

To help stop a slipping blade, a Frasier tip suction is held in place in the direction the blade is cutting.

To prevent accidental durotomy and spinal cord transection, the annulotomy should not go deeper than 11 mm. The sharp edge of the nr 15 blade is 11 mm and can be used as a depth gauge.

The discectomy continues using a Pituitary rongeur forceps to remove the anulus and small curettes to scrape the endplates.

The use of a distractor or an intervertebral distractor will facilitate the removal of the posterior half of the disk and visualize the posterior longitudinal ligament. However, it is difficult to place distractors in the C2-C3 level.

The normal height of the area should be reconstructed. However, care should be taken not to over distract.

A complete discectomy will allow good visualization of the spinal canal and enhance fusion.

Meticulously remove all cartilage from the endplates. Pieces of cartilage may inhibit fusion if present either on the endplates or in the bony material used for the fusion.

A small probe is used to ensure that no fragments are left in the area behind the vertebra which is not directly visualized, or in the foramen.

Magnification and correct illumination is essential to make the final decompression.

Tricortical graft is harvested from the iliac crest and inserted in to the empty disk space. Great care must be taken to trim the graft so that it shares axial load with the plate. Alternatively, a cage filled with either bone graft or bone substitutes can be used.

Care should be taken not to over distract the segment with the implant as this may compromise the postoperative stability.

When choosing the plate length, care must be taken to prevent it from damaging the mobile disks below. The necessary plate length (blue) is confirmed under image intensifier.

Ideally the plate would extend as little as possible above and below the endplates of the injured level.

The plate is bent to accommodate the patient's lordosis and fixed in place with two temporary pins placed in holes diagonal to each other.

The appropriate positioning of the plate is verified in AP and lateral views.

Malrotation of the plate is commonly seen on the AP view and can be adjusted by temporarily removing one pin while adjusting the rotation.

Based on a preoperative measurement of vertebral body depth, screw holes are prepared with the appropriate depth. This is performed under lateral fluoroscopic guidance.

Screws are then inserted but not fully tightened until all screws have been applied.

Final hardware positioning is verified in lateral and AP view.

Patients are made to sit up in the bed on the evening following the operation.

A collar is commonly used following surgical stabilization to moderate patient activity.

The purpose of a collar is to prevent ranges of motion outside of limits deemed unfavorable for fracture healing. Collar is optional.

Patients with intact neurological status are made to stand and walk on the first day after surgery. Patients can be discharged when medically stable or sent to a rehabilitation center if further care is necessary. This depends on the comfort levels and presence of other associated injuries.

Patients are generally followed with periodical x-rays at 6 weeks, 3 months, 6 months, and 1 year.