Transforaminal Endoscopic Foraminotomy (L5-S1): Quick Guide

Transforaminal Approach

STEPS

1. Plan and position

  • Plan the trajectory on axial CT/MRI: disc target point to SAP to skin entry point

  • Watch for a high iliac crest and screw artifact

  • Prone, hips and knees flexed, true AP and lateral fluoro

  • Mark the entry point (5 to 8 cm off midline) and iliac crest

2. Stain the disc (optional)

  • 1 to 2 mL indigo carmine if disc material identification will be critical

3. Dilate and dock the cannula

  • 8 mm incision through fascia

  • Blunt dilators, walked along the SAP to the SAP and pedicle junction. “Bone is my friend.”

  • 8 mm x 165 mm beveled cannula, tip angled caudally on entry to protect the L5 root

  • Confirm on fluoro: lateral SAP (AP), posterior foramen (lateral), not too deep

4. Scope and orient

  • 25° scope, irrigation 60 to 80 mmHg

  • Clear soft tissue off the lateral S1 SAP (rongeurs or RF probe)

5. Foraminoplasty

  • 3.5 mm diamond bur, ~65,000 rpm

  • Start at the SAP base, drill caudal to cranial, away from the L5 root

  • Stop at ~80 to 90% of the hypertrophied SAP removed

6. Partial L5 IAP resection

  • Drill the ventral IAP just until the LF is fully exposed. No complete facetectomy.

7. Detach and remove the LF

  • Spherical bur undercuts the S1 SAP rim at the LF insertion, pulling away from the thecal sac

  • Continue until the LF floats free and pulsates

  • Remove gently with a Kerrison punch or rongeurs (may be calcified; hard pulling risks a dural tear)

8. Confirm and close

  • Probe the L5 root axilla to shoulder; clear any residual spurs or adhesions

  • Goal: relaxed, free, ideally pulsating root

  • RF bipolar for bleeding, 1 or 2 sutures, no drain

Keys to success: trajectory planning, “bone is my friend,” and the detach technique.

Source: https://www.jove.com/v/69059/transforaminal-full-endoscopic-lumbar-foraminotomy-under-local

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