Anterior Cervical Discectomy/Fusion Overview

Anterior Cervical Discectomy/Fusion (ACDF)

• ACDF surgery involves a skin incision on the anterior neck, retracting tissue to expose the anterior cervical spine.
• The surgical area is between the esophagus and trachea medially and the sterno-cleidomastoid muscle and carotid sheath laterally.
• The omohyoid muscle and recurrent laryngeal nerve are retracted inferiorly.
• Handheld or self-retaining retractors expose anterior vertebral column and longus colli muscles.
• Disc tissue is removed to relieve nerve root pressure.
• Vertebrae are fused to the adjacent vertebra with bone, plates, or screws to prevent dislocation.
• Disc space filling methods include pituitaries, curettes, and Kerrison rongeurs, using autografts (patient's bone) or allografts (cadaver bone).
• The Smith-Robinson technique is one example of ACDF procedure.
• Bone grafts are inserted to maintain a neutral vertebral position.
• Plates and screws provide additional spinal stabilization.
• Surgical complications often include:
  • Thrombophlebitis
  • Infection
  • Nerve damage
  • Graft inadequacy (migration, erosion, degradation)
  • Nonunion of cervical vertebrae
  • Chronic pain
  • Acute spinal cord injury
  • Spinal nerve injury
  • Dural tear
  • Anterior spinal artery syndrome
  • Hematoma
  • Venous air embolism
  • Airway edema
  • Unilateral recurrent laryngeal nerve injury
  • Pneumothorax

Preoperative Considerations

• Thorough preoperative evaluation is crucial, including:
  • Sensory and motor function assessment
  • Documentation of symptom exacerbating factors
  • Identification of coexisting diseases
  • Evaluation of pain medication use (type, amount) and potential for anesthetic requirements related to pain tolerance.
• Patients should remain on their current pain medication regimen until the morning of surgery to avoid abrupt narcotic withdrawal leading to sympathetic nervous system response (tachycardia, hypertension, seizure activity).
• Cardiovascular function assessment is critical before ACDF.
• Optimization of cardiac status before surgery minimizes risks, including labile blood pressure, dysrhythmias, myocardial ischemia, myocardial infarction, and heart failure.
• Preoperative ECG assessment, including patient exertion, can assess coronary artery reserve for sufficient supply and absence of ischemia.
• Evaluation of existing hypertension treatment with medications like atenolol is essential. Atenolol should be taken as directed on the day of surgery.

Anesthetic Concerns

• Airway assessment is critical for all patients undergoing anesthesia but with added concerns for ACDF patients.
• Patients with unstable cervical spines may be in external fixation devices, requiring prophylactic neck immobilization or traction.
• "Sniffing position" elevation is contraindicated in acute or unstable cervical spine cases.
• Careful head positioning to prevent pain in the neck or arms (brachial plexus pressure).
• Minimal neck movement during airway management and surgery to minimize cervical spine injuries.
• Preoperative evaluation, including neck mobility, mouth opening, and intubation feasibility assesses patient readiness.
• Cricoid pressure application requires caution, as it carries a risk of neurological damage during intubation.
• Succinylcholine administration is contraindicated for patients with chronic myopathies, as it may cause severe and life-threatening hyperkalemia due to extrajunctional acetylcholine receptors proliferation.
• Regional anesthesia is usually inadequate for ACDF; general anesthesia is the preferred technique.
• Superficial and deep cervical plexus blocks are used for intraoperative and postoperative analgesia; however, this does not typically provide sufficient anesthetic conditions.

Cervical Spine Considerations

• Cervical disc degeneration, a common cause of ACDF, most often affects individuals aged 40-55, but can be evident radiographically/via MRI in younger individuals (30).
• Disc instability is caused by trauma, neoplasms, degeneration, or congenital issues affecting stabilizing structures like ligaments, pedicles, and articulations.
• Cervical vertebrae's significant range of motion, close proximity, and complex anatomy make them vulnerable to injury.
• Degenerative disc disease involves fibrous changes to the disc, reducing pliability.
• Degeneration frequently occurs between C5-C7 vertebrae.
• Cervical compression hinders blood flow potentially leading to canal narrowing, myelopathy, and neural injury and resulting in progressive and permanent spinal cord damage.
• Patients with cervical degeneration may experience worsened discomfort with head and neck movement.
• Symptoms, including neck and shoulder pain, arm and hand pain, weakness, and paresthesia commonly result from disc herniation or rupture and compression of nerve roots or the spinal cord.
• Disc bulging and compression in the softer inner nucleus potentially damages nerves.
• Osteophytes (spondylosis) and congenital spinal stenosis can contribute to cervical nerve compression and symptoms.
• Disc degeneration symptoms typically emerge later in life, but ruptures can be due to age, degeneration, or trauma.
• Conservative treatments (rest, pain relievers, traction, physical therapy) may assist, but some patients with ongoing pain and functional limitations might benefit from surgical interventions.

Intraoperative Period

• Patient positioning is crucial for access. Arms are tucked to surgical field. Ensure less than 90-degree abduction and padding of all pressure points. A gel roll under shoulders to hyperextend neck. Proper head support to minimize cervical vertebra pressure. Endotracheal tube positioned contralateral to incision and free from traction.
• Neurologic monitoring (SSEPs, MEPs) is possible but not common during anterior ACDF. SSEPs are sensitive to inhalation anesthetics (>0.5% MAC). Intravenous anesthetics (narcotics) do not affect SSEPs as much. TIVA is an alternative. Paralytics do not affect SSEPs, but do affect MEPs. Monitoring of MEPs is possible with incomplete paralysis (train-of-four ratio of 3/4).

Fluid Requirements

• Estimated blood loss is typically less than 50 ml. But significant bleeding is possible. Autologous transfusion, blood salvage, and normovolemic hemodilution are possible. Prevent excessive fluid administration to minimize edema (superior vena cava syndrome). Urinary catheters are often used for procedures exceeding two hours to monitor output and prevent bladder distention. Avoid glucose-containing fluids during periods of potential ischemia.

Postoperative Complications: Airway Management in Hematoma

• Rapid respiratory distress/arrest can occur due to tracheal compression by hematoma.
• Hematoma formation can be rapid or slow.
• Tracheal deviation can occur without a large external hematoma.
• Definitive treatment is surgical removal of sutures and hematoma evacuation.
• No single airway management technique is absolutely contraindicated.
• Visualization during induction might be impossible due to hematoma-shifted airway structures.
• Supraglottic devices (laryngeal mask airway, mask ventilation) may be ineffective.
• Fiberoptic intubation may be challenging due to edema and blood.
• Airway anesthetization with nebulized lidocaine can cause collapse.
• Tracheotomy may be needed immediately for establishing the airway.
• Having the ability to perform a rapid tracheotomy is crucial.

This quiz covers essential aspects of Anterior Cervical Discectomy and Fusion (ACDF), including intubation challenges, neurological assessments, surgical risks, and potential postoperative complications. Test your knowledge of the critical considerations involved in this surgical procedure.