Anterior Cervical Foraminotomy Technique

15
Anterior Cervical Foraminotomy Technique

Neil R. Malhotra and M. Sean Grady

Description

Anterior cervical foraminotomy is performed when there are isolated one-level radicular symptoms without findings to support the need for complete diskectomy. In contrast to posterior foraminotomy, the anterior approach provides access to anterior osteophytes and free disk fragments with minimal nerve manipulation. Cervical foraminotomy performed from an anterior approach permits removal of offending spondylotic bone spur or compressive extranuclear disk material in combination with direct visualization of the nerve root. Cervical foraminotomy can significantly improve disability that has resulted from neural compression due to osteophyte formation and disk herniation. When radiculopathy is the primary presenting symptom, foraminotomy can result in significant reduction in radiculopathic symptoms.

Key Principles

Although cervical diskectomy effectively addresses myelopathy, it is foraminotomy, with clear decompression of the nerve root, that most effectively addresses unilateral upper extremity radiculopathy.

Expectations

Failure to address foraminal free disk fragments and osteophytes will plague the patient and surgeon alike. The key pathology can be accessed and removed via foraminal exploration. Decompression of the nerve root leads to excellent outcomes in the appropriately selected patient population. Always counsel the patient about the risk of postoperative sympathetic plexus injury and Horner-type syndrome, as well as hoarseness, cerebrospinal fluid leak, and swallowing difficulties.

Indications

Isolated unilateral radiculopathy, in conjunction with imaging that supports the finding of a free disk fragment, indicates the need for, and potential benefit of, anterior cervical foraminotomy.

Contraindications

Anterior cervical foraminotomy is contraindicated in patients with neck pain and myelopathy. In myelo-pathic patients anterior cervical diskectomy and fusion is appropriate with appropriate pathology. Additionally, in the setting of posterior compression, or significant spondylolisthesis at adjoining levels, anterior foraminotomy is contraindicated.

Special Considerations

Preoperative imaging, including magnetic resonance imaging (MRI), and possibly plain x-ray, in conjunction with attention to the physical exam and a description of the location of pain permits tailoring of surgery to most benefit the patient. Perform flexion extension x-ray if a question of instability exists. Consider computed tomography (CT) scan through surgical levels if other imaging does not adequately resolve questions concerning bony pathology.

Special Instructions, Position, and Anesthesia

The patient is placed supine on the operative table with a gel roll under the scapulae to aid extension and exposure of the operative field. A foam doughnut or horseshoe headrest placed under the head enables maximal safe extension and minimizes jaw intrusion into the operative field. Perioperative antibiotics should be administered 30 minutes prior to the skin incision. Fiberoptic intubation is generally not needed. Anesthesia colleagues should minimize the use of airway monitors such as temperature probe when alternative options exist. Shoulders should be taped down to maximize cervical exposure and permit adequate cross-table lateral x-ray to be taken for localization. Arms should be tucked at the patient’s side. Intraoperative physiologic monitoring is not needed.

Tips, Pearls, and Lessons Learned Dealing with Difficulties Encountered

The skin incision should be on the side of the radiculopathy to permit greatest exposure of the pathologic foramen.

Horizontal skin incisions, incorporating an existing skin wrinkle, result in the most aesthetically pleasing scar for the patient.

A vertical incision through the platysma allows the greatest freedom in the surgical approach to multiple levels and minimizes stress on the healing wound.
Lateral retraction of the longus colli permits excellent exposure.
Upturned curette or Penfield No. 4 elevator (Miltex, Tuttlingen, Germany) permits palpation of the transverse process (TP). It is the TP that will act as a crucial outer landmark for the approach.
The imaginary line formed by connecting the medial aspect of the transverse process above and below the disk level of the operation acts as an excellent lateral border of the exposure and minimizes risk of injury to the vertebral artery (Fig. 15.1). It is imperative to determine the location of the vertebral artery based on the preoperative imaging (Fig. 15.2).
Do not remove the longus colli lateral to the vertebral body as risk to the overlying sympathetic trunk is increased (Fig. 15.3).
A bent spinal needle, with stylet, can be used to localize the disk level on fluoroscopy or cross-table x-ray prior to annulotomy.
A Kerrison punch is excellent for removing the longus colli from the medial aspect of the operative field.
In the cervical spine, the nerve root exits above the pedicle of its like-numbered vertebra and closely hugs the inferior portion of the above pedicle (Fig. 15.4).
The microscope should be employed from this point forward.
A 2-mm cutting burr is excellent for creating a cylinder down to the posterior longitudinal ligament (PLL). The PLL can be pierced with an upturned curette and then resected with a 1-0 or 2-0 Kerrison rongeur.
The 2-mm cutting burr can be used to drill off the uncinate process.
The right-angled blunt nerve probe is excellent for exploration of the foramen.
If a path into the foramen cannot be safely created, a temporary increase in Caspar retraction can be employed to further open the space.
The footplate of the 2-mm Kerrison punch can be placed into the foramen for completion of the decompression.
Always reexplore the foraminotomy cavity with the nerve hook to confirm adequate decompression.