Eli M. Baron, Alexander R. Vaccaro, and Peter M. Fleischut

Description

The lateral retropharyngeal approach to the upper cervical spine was developed by Kelly and Whitesides as an alternative approach to the anterior cervical spine, avoiding the complexities of anterior extrapharyngeal approaches, which require an approach medial to the carotid sheath or dislocation of the mandible. This approach is actually done posterior to the carotid sheath, avoiding branches of the carotid artery and the facial nerve. Additionally, the approach allows access from C1 to T1 and avoids the potentially higher morbidity of a transoral/transpalatal approach.

Expectations

To perform a stand-alone C1-C2 anterior arthrodesis via a bilateral lateral approach.

Indications

Instability at C1-C2 requiring anterior fixation or when an anterior approach is required for a diagnosis. The approach is advantageous over a transoral approach where fixation is necessary for instability and a posterior approach is contraindicated (presence of posterior infection or incompetent posterior elements). It also may be useful as a salvage technique following failed posterior arthrodesis.

Contraindications

• Vertebral artery injury
  
• Local infection
  
• Inexperience with regional anatomy

Special Instructions, Position, and Anesthesia

The patient is placed in the supine position. Fiberoptic nasotracheal intubation is preferred in cases of significant instability. Intraoperative neurophysiologic monitoring, including somatosensory evoked potentials and transcranial motor evoked potentials, if available, is used during positioning and throughout the procedure. Dental occlusion should be maintained to keep the angle of the mandible from limiting the area of dissection.

Biplanar fluoroscopy or frameless stereotaxy may be useful during guidewire insertion, drilling, and screw placement to ensure proper instrumentation placement while limiting the risk of neurovascular injury.

For positioning, if not contraindicated, the neck should be rotated to the opposite side and extended as much as possible. The ear lobe can be sewn anteriorly to the cheek to facilitate exposure of the field. Postoperative prophylactic tracheostomy should be considered in cases where there is significant retropharyngeal dissection. Performance of the tracheostomy after the procedure is usually more convenient.

Tips, Pearls, and Lessons Learned

Preoperative imaging and planning are essential prior to performing the procedure. This includes computed tomography (CT) imaging for studying bony anatomy and estimating screw length. CT angiography and magnetic resonance angiography (MRA) are useful noninvasive modalities for assessing the position and patency of the vertebral arteries.

Difficulties Encountered

• Avoid the parotid gland, which may be seen superficially at the cranial end of the incision. Dissection into the gland may result in facial nerve injury or parotid fistula. Also, deep at the cephalad end of the incision lies the posterior belly of the digastric muscle. Care should be taken to avoid retraction against this muscle to minimize risk of injury to the facial nerve, which lies between the digastric muscle and the base of the skull.
  
• Excessive medial retraction on the nasopharynx may result in mucosal laceration and subsequent contamination of the field.
  
• Excessive retraction may contribute to postoperative dysphagia and possible cranial nerve injury, including the hypoglossal and superior laryngeal nerve.
  
• Excessive retraction on the spinal accessory nerve should be avoided to minimize risk of sternocleidomastoid or trapezius weakness.

Key Procedural Steps