Endoscopic Cervical Spine Surgery

Courtesy: Prof Osama N Kashlan, Dubai, UAE

 

Endoscopic Cervical Spine Surgery:

1. Learning Curve & Prerequisites

• Progression Pathway: Begin with lumbar transforaminal and interlaminar microdiscectomies. Attain proficiency in lumbar canal stenosis decompression (unilateral laminotomy for bilateral decompression [ULBD]) over 40 to 50 cases before transitioning to the cervical spine.

• Initial Cervical Procedures: Posterior cervical foraminotomy is the preferred entry procedure. The endoscope and burr operate lateral to the thecal sac rather than hovering directly over the cervical spinal cord, reducing the risk of catastrophic neural injury compared to central laminectomies.

2. Endoscopic Cervical Foraminotomy

• Indications:

  • Cervical radiculopathy refractory to conservative therapy (analgesia, physiotherapy, selective nerve root blocks).

  • Unilateral 1- or 2-level bony or ligamentous foraminal stenosis (hypertrophic facet, osteophytes, ligamentum flavum).

  • Soft disc herniations located lateral to the lateral margin of the thecal sac / spinal cord.

• Biomechanics & Hydraulic Retraction: Continuous saline inflow creates local hydrostatic pressure that gently displaces the thecal sac medially. When paired with angled optics (15° to 30°), this enables visualization and decompression of lesions extending slightly medial to the cord margin without direct neural retraction.

• Patient Positioning & Room Setup:

  • Prone position on a padded face plate (preferred over pin Mayfield clamps to prevent pin site morbidity).

  • Head positioned in slight flexion; this slides the superior articular process (SAP) and inferior articular process (IAP) apart, opening the neuroforamen.

  • Arms secured (“burrito” wrapped) to stabilize the torso, or placed on armrests to depress the scapulae and optimize lateral fluoroscopic visualization.

  • Continuous intraoperative neuromonitoring (SSEP / MEP / EMG) recommended.

• Scope Selection: Small interlaminar scope (preferred for manoeuvrability and bone conservation around tight neurovascular corners) or a larger stenosis scope (~10 mm, offering lower plunge risk for early adopters).

• Fluoroscopic Trajectories:

  • Anteroposterior (AP): Target the anatomical “V-point” (junction of the cranial and caudal lamina with the medial facet) along the medial pedicular line.

  • Lateral Option 1 (Angle Bisection): Angle bisects the intervertebral disc plane and facet plane. Minimizes resection of the cranial level’s IAP to reach the offending caudal SAP; however, feeling the inferior pedicle is more difficult.

  • Lateral Option 2 (Perpendicular to Disc): Standard trajectory parallel to the disc space. Sacrifices more IAP bone but is ergonomic, highly reproducible, and allows tactile palpation of both the cranial and caudal pedicles to confirm adequate decompression.

• Surgical Steps:

  1. Radiofrequency soft-tissue debridement over the medial facet and lamina until the “V-point” is exposed.

  2. High-speed diamond burr drilling under continuous saline irrigation. Resect the medial aspect of the cranial IAP and caudal SAP, transitioning the “V-shape” into a “U-shape.”

  3. Identify the cranial and caudal attachments of the ligamentum flavum. Detach both margins to create a mobile, trampoline-like ligament flap, safely unroofing the exiting root.

  4. Excision of ligamentum flavum with small punches/pituitary forceps to visualize the thecal takeoff and the dorsal root.

  5. Disc fragment excision (if indicated): Differentiate the ventral motor root from disc material using a blunt nerve hook passed lateral to the thecal sac; tissue lying ventral/deep to the hook is safe for disc plucking.

• Endpoint Criteria: Bony and soft-tissue unroofing from the cranial pedicle to the caudal pedicle, and mediolaterally from the dural root takeoff to past the lateral margin of the pedicles (typically involves resecting roughly 50% of the facet joint without compromising spinal stability).

3. Endoscopic Cervical Laminectomy (ULBD)

• Indications:

  • Painless or minimally painful cervical spondylotic myelopathy secondary to posterior ligamentous hypertrophy and central canal stenosis.

  • Preserved cervical sagittal alignment without gross kyphosis or segmental instability.

  • Alternative to multi-level laminoplasty or open laminectomy with fusion.

• Technique:

  • Scope: Larger stenosis endoscope used to prevent accidental canal plunging over the vulnerable, compressed spinal cord.

  • Trajectory: Starting point begins more lateral (at the midpoint or lateral edge of the pedicle) and parallel to the spinous processes to facilitate a working trajectory toward the contralateral dorsal lamina.

  • Decompression: Drill the inferior margin of the cranial lamina and superior margin of the caudal lamina. Undercut the base of the spinous process and follow the deep ligamentum flavum across the midline to decompress the contralateral cord.

  • Preservation of Sagittal Stabilizers: The interspinous ligament, nuchal ligament, and contralateral dorsal musculature remain structurally intact, reducing post-laminectomy kyphosis.

4. Hemostasis and Pressure Management

• Pharmacological Hemostasis: Pre- and post-operative IV tranexamic acid (1 g); dilute epinephrine (1 mg per 3 L irrigation bag) added to the initial fluid bags.

• Fluid Dynamics: Maintain the lowest functional pump irrigation pressure to avoid cord compression or elevated intracranial/epidural pressures while providing a fluid buffer against inadvertent durotomy.

• Thermal & Mechanical Protection: Use diamond burrs under continuous irrigation to prevent thermal injury to nerve roots; avoid aggressive use of Kerrison rongeurs, which can tear epidural veins.

• Uniportal vs. Biportal Endoscopy: Biportal endoscopy allows separate inflow/outflow channels and independent large-instrument insertion (e.g., standard bone wax), whereas uniportal systems utilize a single working channel with integrated irrigation and optics.

Master Revision Summary

• Surgical Indications: Endoscopic foraminotomy targets unilateral radiculopathy and lateral/foraminal disc-osteophyte pathology; endoscopic ULBD addresses dorsal, ligamentous central cervical myelopathy without kyphosis.

• Anatomical Target: The “V-point” at the junction of the medial facet joint and the cranial/caudal laminae along the medial pedicle line.

• Bone Work: Conversion of the laminar “V-point” into a wide “U-shape” using a high-speed diamond burr under continuous fluid irrigation.

• Decompression Margins: Pedicle-to-pedicle craniocaudally, and dural root takeoff to lateral pedicle margin mediolaterally (~50% medial facetetomy).

• Nerve vs. Disc Distinction: The ventral motor root is identified by sweeping a nerve hook along the lateral dural edge; tissues ventral/deep to the hook represent herniated disc material.

• Complication Prevention: Maintain minimal pump pressures to prevent cord barotrauma, strictly verify operative levels via intraoperative fluoroscopy/navigation, and preserve the dorsal tension band to prevent post-laminectomy kyphosis.