Anterior cervical discectomy and fusion for cervical radiculopathy

Case Presentation

• 27-year-old male presents with > 6 months of pain radiating down the RIGHT arm to the thumb and index finger.
• He has failed conservative therapy including physical therapy and NSAIDs.
• Past medical history: None
• Past surgical history: None
• Allergies: None
• Medications: None
• Physical Exam:
  • Motor exam: 5/5 throughout
  • Sensory exam: decreased to light touch along a RIGHT C6 dermatome
  • Reflexes: normal and symmetric
  • Absent Hoffman's reflex
  • Normal gait

Approach

• Anterior cervical discectomy and fusion
  • The patient ultimately decided to proceed with a single-level ACDF for definitive decompression and stabilization of the motion segment.

Alternatives

• Conservative
  • Physical therapy, NSAIDs, cervical traction, epidural steroid injections, selective nerve root block
    • In this case, the patient had failed conservative treatment options for > 6 months.
• Anterior
  • Anterior cervical discectomy and fusion
    • The patient ultimately decided to proceed with a single-level ACDF for definitive decompression and stabilization of the motion segment.
  • Anterior cervical disc replacement
    • Cervical disc replacement ("cervical arthroplasty," "cervical artificial disc") is a reasonable alternative procedure in this patient. Cervical disc replacement generally results in equivalent neurologic, pain and functional benefit as ACDF. The advantage of cervical disc replacement over ACDF is better preservation of radiographic range of motion. The long-term benefit of single-level cervical disc replacement versus ACDF on adjacent segment disease remains unclear. Anterior foraminotomy (i.e., uncinate process resection)
    • This nonfusion technique is utilized for anterior decompression of a unilateral cervical nerve root. Generally, it is indicated for primarily foraminal disc herniations without spinal cord compression. This is a technically challenging approach, given the close proximity of the vertebral artery.
• Posterior
  • Posterior lamino-foraminotomy
    • This nonfusion technique is utilized for decompression of a unilateral cervical nerve root. Generally, it is indicated for primarily foraminal disc herniations without spinal cord compression. There is potentially more approach-related morbidity than an anterior approach, as it involves dissecting through the posterior paraspinal musculature.
• Laminectomy, laminectomy and fusion, or laminoplasty
  • These posterior approaches for decompression of the spinal cord and/or spinal nerve root(s) generally involve more approach-related morbidity as they involve more extensive dissection of the posterior paraspinal musculature. Comparatively, these posterior approaches are preferred when multiple levels of spinal cord compression are involved (in the absence of cervical kyphosis).

Positioning

• Supine positioning
• Jackson or standard operating table
• Head in neutral position or with slight cranial extension (e.g., with a horizontal shoulder bump)
• Additional intraoperative adjuncts
  • Fluoroscopy
  • Operating microscope or Loupe magnification
  • +/- Intraoperative neuromonitoring

Anatomy

• Important anatomical considerations:
  • Neurologic:
    • Extraspinal:
      • Recurrent laryngeal nerve
      • Superior laryngeal nerve
      • Vagus nerve
      • Sympathetic chain
    • Intraspinal
      • Spinal cord
      • Cervical nerve roots
  • Vascular:
    • Extraspinal
      • Carotid sheath (common carotid artery, internal jugular vein)
    • Intraspinal
      • Vertebral artery
  • Soft Tissue:
    • Esophagus
    • Trachea
    • Thoracic duct

Incision

• For a single-level ACDF, a single horizontal incision is made from the medial border of the sternocleidomastoid (palpated) to the midline.
• Deciding LEFT- vs RIGHT-sided incision
  • A RIGHT-sided incision is often preferred by RIGHT-handed surgeons.
  • For a LEFT-sided incision, the left recurrent laryngeal nerve takes a more predictable course in the tracheo-esophageal groove and is theoretically less prone to injury.
  • A point to consider is that unilateral foraminal disc osteophyte complex is easier to resect using a Kerrison from the contralateral side (e.g., a RIGHT-sided disc-osteophyte complex may be approached from a LEFT-sided incision).

Operation

• After skin incision, the platysma is identified, elevated, and divided horizontally.
• The subplatysmal space is undermined and released to provide greater rostral-caudal exposure.
• The medial border of the sternocleidomastoid muscle (SCM) is identified.
• The superficial layer of the deep cervical fascia (connecting the SCM to the strap muscles) is elevated and divided sharply in a longitudinal manner.
• The carotid artery is palpated laterally, and the esophagus and trachea are identified medially.
• Blunt dissection is carried down in this potential space to the anterior cervical spine.
• Sweeping blunt dissection with a Kittner is performed to displace the prevertebral fascia.
• The paired longus colli muscles are identified.
• A spinal needle is placed in the disc space, and intraoperative fluoroscopy is performed to confirm the appropriate level.
• A cuff of longus colli muscle is elevated on the lateral aspect of the disc space.
• Bladed retractors are placed underneath the cuff of longus colli muscles.
• The endotracheal tube cuff is deflated and gently re-inflated to a lower cuff pressure to decrease pressure on the tracheo-esophageal groove (and recurrent laryngeal nerve).
• Caspar pins are placed into the vertebra above and below the disc space.
• Distraction across divergent ("angulated") pins opens the disc space and creates lordosis.
• Using either Loupe or microscope magnification, the anterior longitudinal ligament and anterior annulus is cut.
• Disc material is removed with rongeurs and curettes.
• Care is made to stay within the margins of the uncinate processes (white arrows) laterally. The vertebral artery courses just lateral to the uncinated process (red circles).
• The posterior longitudinal ligament is elevated and resected.
• A nerve hook can be passed gently behind the rostral and caudal vertebral bodies to confirm spinal cord decompression. The nerve hook can then be passed out both foramen to confirm spinal nerve root decompression.
• Anterior and posterior osteophytes (both rostral and caudal) are removed to create a parallel channel for insertion of the intervertebral graft.
• Endplate preparation with a curette and/or rasp is performed to enhance arthrodesis.
• A lordotic cage or structural allograft is inserted into the disc space.
• An anterior plate is sized appropriately (i.e., ideally not extending to the adjacent disc space).
• Divergent semi-constrained screws are placed in the sagittal plane to allow for eventual compression across the intervertebral graft.
• Convergent ("triangulated") screws are placed in the axial plane to resist pull-out.
• Intraoperative fluoroscopy is performed to confirm adequate anterior plate and screw and graft position.
• Meticulous hemostasis is obtained.
• A Jackson Pratt drain may be placed to prevent risk of hematoma formation resulting in respiratory compromise - an indication for emergent reopening of the incision for hematoma evacuation.
• The platysma is approximated.
• The skin is closed with a subcutaneous absorbable running suture.
• The incision is covered with skin glue.

Post Op

• Follow up x-rays demonstrate stable position of the anterior plate, screws, and intervertebral graft.

Outcome

• The patient presented again 4.5 years later with acute onset neck pain.
• An MRI was performed which confirmed stable decompression at C5-6 with arthrodesis.

Pearls and Pitfalls

• Exposure
  • Careful exposure of the anterior neck with adequate release of soft tissue structures, preserving natural cleavage planes, and meticulous hemostasis facilitates the rest of the procedure. This will also minimize excessive soft tissue retraction, which may increase risk of recurrent laryngeal nerve palsy or dysphagia.
  • Minimize electrocautery along the surface of the longus colli muscle, which may result in thermal injury to the sympathetic chain.
• Discectomy and Decompression
  • Careful use of curettes and rongeurs (as opposed to the drill) will ensure staying within the margins of the uncinate processes (laterally) and the bony endplates (rostral - caudal).
  • Assess preoperatively for ossification of the posterior longitudinal ligament (OPLL). If OPLL is present, then be prepared for possible durotomy or absent dura during the decompression.
• Cage/Graft Placement and Anterior Instrumentation
  • Removal of anterior and posterior osteophytes will ensure placement of a properly sized cage/graft.
  • Avoid oversizing the cage/graft. This may result in violation of the bony endplates and eventual excessive subsidence.
  • Careful removal of anterior osteophytes to provide a flat ventral surface will ensure the anterior plate sits flush along the vertebral bodies. A plate that sits proud may cause mechanical obstruction of the esophagus with resulting dysphagia.
  • Avoid using an oversized plate that encroaches on the adjacent disc space as this may accelerate degeneration at the next level.
• Closure and Post-op
  • Meticulous hemostasis with possible drain placement will decrease the risk of a postoperative hematoma and potential respiratory compromise.
  • A cervical collar is typically not necessary in patients undergoing 1 level ACDF and in patients who do not have significant risk factors for pseudarthrosis (e.g., smoking, chronic steroid use).
  • For single-level ACDF, it is reasonable to consider discharging patients either the same day or the next morning after surgery.

Discussion

• Anterior cervical discectomy and fusion is an effective means for treatment of cervical radiculopathy, secondary to a compressive disc-osteophyte complex.