Transforaminal Epidural Steroid Injections (TFESI)

Standard Lumbar TFESI Technique

Transforaminal epidural steroid injection (TFESI) is the preferred approach for delivering corticosteroid to the ventral epidural space in patients with unilateral radiculopathy. The procedure requires fluoroscopic guidance and real-time contrast confirmation.

Step-by-Step Procedural Approach

1. Patient positioning: Prone on the fluoroscopy table with a pillow under the abdomen to reduce lumbar lordosis
2. Level identification: Use AP fluoroscopy to identify the target vertebral level by counting from the sacrum. Verify transitional anatomy if present — correlation with cross-sectional imaging and counting from T1 is essential when there is transitional lumbosacral anatomy.
3. Oblique the C-arm: Rotate 15-30 degrees ipsilateral to the side of pathology to visualize the "Scotty dog" anatomy
4. Identify the target: The "safe triangle" — inferior to the pedicle (eye of the Scotty dog), superior to the exiting nerve root, lateral to the spinal canal
5. Needle selection: 22-25 gauge spinal needle (Quincke-type), typically 3.5-inch (90 mm) or longer for lumbar procedures. A slight bend near the distal tip enhances directional control during steering. Use microbore extension tubing for all injections.
6. Coaxial advancement: Use tunnel vision technique to advance the needle toward the target under intermittent fluoroscopy
7. Confirm position: Check AP and lateral views to verify the needle tip is at the correct location — in the superior-anterior aspect of the foramen
8. Contrast injection: Inject 0.5-1.0 mL of non-ionic iodinated contrast under live fluoroscopy (with or without digital subtraction imaging) through microbore extension tubing to confirm epidural spread
9. Pattern recognition: Look for nerve root outlining and medial epidural flow; ensure NO vascular uptake pattern
10. Steroid injection: After confirming a safe epidural pattern, inject the steroid preparation (typically 1-2 mL total volume)

Three Approach Options (per IPSIS)

The IPSIS Technical Manual describes three distinct approaches to the lumbar foramen, each with specific indications:

• Supraneural approach: Needle positioned above the nerve in the superior foramen, just below the pedicle. Uses 10-15 degrees of ipsilateral obliquity to pass under the pars interarticularis. On lateral imaging, the needle tip should lie immediately beneath the pedicle without contacting the posterior vertebral body. This is the classical approach targeting the ventral-superior quadrant of the foramen.
• Infraneural approach: Needle positioned below the segmental nerve in the inferior foramen. Requires greater obliquity (SAP at midpoint of vertebral body). The needle contacts the lateral SAP border and advances medially a few millimeters. On lateral view, the needle tip should be posterior to the dorsal disc border. This approach offers a safety advantage because the artery of Adamkiewicz is located almost universally in the anterior-superior quadrant of the foramen — it is essentially never found posterior to the nerve in the inferior foramen.
• Retroneural approach: Needle placed directly posterior to the nerve. Useful when the exiting nerve has been displaced superiorly (e.g., by intraforaminal disc extrusion). Also used for diagnostic spinal nerve blocks.

Level Selection: A Critical Decision

Level selection is a major teaching point with evolving practice patterns:

• Traditional approach: Needle placed at the level of herniation (e.g., L4-5 disc = L5 TFESI at L5-S1 foramen)
• "Below the disc" rationale: An L4-5 disc herniation typically compresses the traversing L5 nerve root, which exits at the L5-S1 foramen. Injecting at L5-S1 targets the affected nerve directly where it exits
• Key principle: Determine whether the pathology affects the exiting or traversing root to select the optimal injection level
• S1 TFESI: Performed through the posterior S1 foramen. The arcuate line of Aprill (continuity of the medial cortical margin of the S1 pedicle and lateral wall of the S1 root canal) is the key fluoroscopic landmark. Slight ipsilateral oblique rotation (10-15 degrees) and cephalocaudal tilt help visualize the posterior foramen. The S1 nerve lies deep in the foramen, and the target zone is directly posterior to the nerve.
• Transitional anatomy: When transitional lumbosacral vertebrae are present, complete spinal radiographs or scout images are needed to accurately enumerate vertebral levels by counting from T1.

Contrast Patterns

• Epidural pattern: Outlines the nerve root sleeve, spreads medially with vacuolization (filling around epidural fat) — this is the desired pattern. On lateral view, contrast flows into the concavity of the posterior vertebral body.
• Vascular uptake: Rapid clearing of contrast in a branching (arborizing) pattern that fades quickly — STOP and reposition if venous; ABORT if arterial
• Intrathecal pattern: Central accumulation with fluid-fluid level on lateral imaging — STOP immediately
• Intradural pattern: "Tram track" sign of parallel longitudinal bands or globular accumulation with sharp margins — ABORT the procedure
• Intradiscal flow: If contrast enters the disc, retract the needle and re-inject until epidural spread is confirmed

Needlecraft Principles (per IPSIS)

The IPSIS Needlecraft chapter emphasizes key handling skills:

• Bevel awareness: For Quincke-type spinal needles, tissue pressure on the bevel face deflects the tip away from the bevel/hub notch. The physician must always know bevel orientation.
• Tip bending: A slight permanent bend near the distal tip (away from the bevel face) provides finer directional control. The closer to the tip and smaller the angle, the more precise the steering.
• Counter-bending: For flexible needles (22G or smaller), deflecting the hub toward the desired direction of tip movement augments steering.
• Fascial fixation: Once the needle has crossed the paraspinal fascia, its trajectory becomes relatively fixed at two points (skin and fascia). If the trajectory is incorrect at this point, the needle should be repositioned rather than forcing futile manipulation.
• Injection safety: Maintain hand contact with the patient during injection through extension tubing and keep slack in the tubing to prevent needle displacement if the patient moves.