What is the step-by-step procedure for a partial discectomy by endoscopy at the L4-L5 level?

Endoscopic Partial Discectomy at L4-L5: Step-by-Step Procedure

Endoscopic partial discectomy at L4-L5 is an effective minimally invasive procedure for treating contained disc herniations with less tissue trauma and faster recovery compared to traditional open approaches.

Patient Selection and Preoperative Considerations

• Appropriate indications:

  • Contained or small non-contained disc herniations at L4-L5 level
  • Radicular pain that is disabling and intrusive
  • Failure of conservative management for at least 6 weeks 1
  • Absence of significant spinal instability

• Preoperative imaging:

  • MRI without contrast is preferred for evaluating neural foraminal stenosis and thecal sac compression 1
  • CT may be considered if MRI is contraindicated

Anesthesia Options

• Local anesthesia with sedation is preferred:

  • Allows for patient feedback during the procedure
  • Associated with shorter hospital stays compared to general anesthesia 2
  • Enables immediate neurological assessment
  • Requires anesthesiologist availability if needed 3

• General anesthesia may be considered for:

  • Anxious patients
  • Complex cases requiring longer operative time
  • Patient preference

Surgical Approaches for L4-L5 Endoscopic Discectomy

Two main approaches can be used for L4-L5 endoscopic discectomy:

1. Transforaminal Approach

• Best for:
  • Shoulder-type disc herniations (lateral to the traversing nerve root)
  • Centrally located disc herniations
  • Recurrent disc herniations 4

2. Interlaminar Approach

• Best for:
  • Axillary-type disc herniations (medial to the traversing nerve root)
  • Migrated disc fragments, especially high-grade migrations 4
  • Cases with high iliac crest that makes transforaminal approach difficult

Step-by-Step Procedure for Transforaminal Approach

1. Patient Positioning:

   • Position patient prone on a radiolucent table
   • Ensure proper padding of pressure points
   • Flex hips and knees slightly to open the interlaminar space

2. Entry Point Marking:

   • Use fluoroscopy to identify the L4-L5 disc space
   • Mark entry point 8-12 cm lateral to midline (typically 10 cm)
   • Confirm trajectory with anteroposterior and lateral fluoroscopic views

3. Local Anesthesia Administration (if using local):

   • Infiltrate skin and subcutaneous tissue at entry point
   • Advance needle along planned trajectory, infiltrating deeper tissues
   • Inject anesthetic into the facet joint capsule and around the annulus

4. Needle Insertion:

   • Insert an 18G spinal needle through the entry point
   • Direct toward the intervertebral foramen at L4-L5 under fluoroscopic guidance
   • Confirm position with anteroposterior and lateral views
   • Needle tip should be positioned at the medial pedicular line in AP view and posterior vertebral line in lateral view

5. Guidewire and Sequential Dilation:

   • Remove needle stylet and insert guidewire
   • Make a small skin incision (7-8 mm)
   • Insert sequential dilators over guidewire
   • Place working cannula over final dilator

6. Endoscope Insertion:

   • Insert endoscope through working cannula
   • Connect irrigation system with normal saline
   • Establish clear visualization of anatomy

7. Foraminoplasty (if needed):

   • Use endoscopic drill or reamer to enlarge the foramen
   • Remove ventral portion of the superior articular process
   • Preserve facet joint stability

8. Discography:

   • Perform discography using indigo carmine mixed with radio-opaque dye 5
   • Helps identify pathological disc material (stains blue)
   • Confirm needle position in disc space

9. Disc Removal:

   • Identify herniated disc material
   • Use endoscopic forceps to grasp and remove fragments
   • Use radiofrequency probe for hemostasis and to shrink the annular tear
   • Continue removal until adequate decompression is achieved
   • Confirm free mobilization of the nerve root

10. Final Inspection and Closure:

    • Perform final inspection to ensure complete decompression
    • Remove endoscope and working cannula
    • Close skin incision with single suture or adhesive strip
    • No need for muscle or fascial closure

Step-by-Step Procedure for Interlaminar Approach

1. Patient Positioning:

   • Position patient prone on a radiolucent table
   • Ensure proper padding of pressure points
   • Flex hips and knees slightly to open the interlaminar space

2. Entry Point Marking:

   • Use fluoroscopy to identify L4-L5 interlaminar space
   • Mark entry point 1-2 cm lateral to midline on the symptomatic side

3. Local Anesthesia Administration (if using local):

   • Infiltrate skin and subcutaneous tissue at entry point
   • Advance needle along planned trajectory, infiltrating deeper tissues
   • Inject anesthetic into ligamentum flavum and epidural space

4. Skin Incision and Dilation:

   • Make a small skin incision (7-8 mm)
   • Insert sequential dilators under fluoroscopic guidance
   • Place working cannula over final dilator targeting interlaminar window

5. Endoscope Insertion:

   • Insert 6-mm working channel endoscope through cannula 5
   • Connect irrigation system with normal saline
   • Establish clear visualization of anatomy

6. Ligamentum Flavum Identification and Opening:

   • Identify ligamentum flavum
   • Create a small opening in ligamentum flavum using endoscopic scissors or punch
   • Expand opening to access epidural space

7. Epidural Space Exploration:

   • Identify dural sac and traversing nerve root
   • Protect neural structures with patties or dissectors

8. Disc Herniation Identification and Removal:

   • Identify herniated disc material
   • Use endoscopic forceps to grasp and remove fragments
   • Use radiofrequency probe for hemostasis
   • Continue removal until adequate decompression is achieved
   • Confirm free mobilization of the nerve root

9. Final Inspection and Closure:

   • Perform final inspection to ensure complete decompression
   • Check for dural tears or CSF leakage
   • Remove endoscope and working cannula
   • Close skin incision with single suture or adhesive strip

Biportal Endoscopic Technique (Alternative Approach)

For bilateral disc herniations, a biportal endoscopic approach can be used:

1. Create two separate portals:

   • Viewing portal for endoscope
   • Working portal for instruments

2. Perform unilateral laminotomy with bilateral discectomy:

   • Access both sides of the disc through a single-sided approach
   • Mean operative time approximately 67.5 minutes 6

Postoperative Care

• Typically outpatient procedure with mean hospital stay of 12 hours 5
• Early ambulation encouraged (within hours of procedure)
• Return to work in approximately 4-7 weeks 4, 5
• Follow-up MRI may be performed 1 day after surgery to confirm adequate decompression 6

Potential Complications and Management

• Dural tear (1-3%): May require conversion to open procedure if significant CSF leakage
• Transient dysesthesia (5-10%): Usually resolves within weeks
• Recurrent herniation (3-7%): May require repeat procedure or open surgery
• Infection: Rare with proper sterile technique
• Incomplete removal: May require subsequent open surgery (3-7% of cases) 4

Clinical Outcomes

• Significant improvement in Visual Analog Scale (VAS) scores for leg pain
• Significant improvement in Oswestry Disability Index (ODI)
• Success rates of 80-90% for properly selected patients 3, 5
• Faster recovery compared to traditional open approaches

Endoscopic discectomy at L4-L5 offers a minimally invasive alternative to traditional open procedures with comparable efficacy, less tissue trauma, and faster recovery when performed by experienced surgeons in properly selected patients.