How is a Transforaminal Epidural Steroid Injection (TFESI) performed?

Transforaminal Epidural Steroid Injection (TFESI) Technique

TFESI must be performed under fluoroscopic guidance with specific C-arm angle settings that vary by spinal level to ensure accurate needle placement and minimize radiation exposure. 1, 2

Pre-Procedure Setup

Patient Positioning

• Place patient prone on a flat radiolucent fluoroscopy table without devices to alter lumbar spine curvature 3
• Maintain sterile technique throughout the procedure 1

Equipment Preparation

• C-arm fluoroscope positioned for optimal visualization 1
• Contrast medium to confirm needle placement and rule out intravascular injection 1, 2
• Steroid mixed with local anesthetic for injection 4

Fluoroscopic Angle Settings by Level

L4-5 Level

• Oblique angle: 30° (±5°) - achieved in 71% of cases 3
• Cephalad/caudal tilt: 0° (neutral ±5°) - achieved in 94% of cases 3

L5-S1 Level

• Oblique angle: 30° (±5°) - achieved in 72% of cases 3
• Cephalad tilt: 15° (±5°) - achieved in 62% of cases 3
• In men: cephalocaudal angle of 11.0° and oblique angle of 25° provides maximal safe triangle area of 18.3 mm² 5
• In women: cephalocaudal angle of 13.9° and oblique angle of 30° provides maximal safe triangle area of 23.6 mm² 5

S1 Level

• Oblique angle: 5° (±5°) - achieved in 73% of cases 3
• Cephalad tilt: 15° (±5°) - achieved in 69% of cases 3
• Alternative "Scotty dog" oblique approach reduces needle passage time (24.4 seconds vs 47.8 seconds with AP approach) 4

Step-by-Step Needle Insertion

Initial Targeting

• Adjust C-arm to level-specific angles as outlined above 3
• Identify the "safe triangle" formed by the exiting nerve root superiorly, the lateral border of the vertebral body medially, and the pedicle above 5
• Mark skin entry point using fluoroscopic guidance 1

Needle Advancement

• Insert needle at the predetermined angle toward the superior-anterior aspect of the neural foramen 1, 3
• Advance needle incrementally with intermittent fluoroscopic confirmation 1
• Expected needle passage time into foramen: 24-48 seconds depending on approach and patient anatomy 4
• Critical warning: Obese patients (higher BMI) require significantly longer procedure times 4

Confirmation of Needle Position

• Obtain AP and lateral fluoroscopic views to confirm needle tip position at the superior-anterior aspect of the foramen 1, 2
• Mandatory contrast injection to visualize spread pattern and rule out intravascular uptake (occurs in 11-23% of cases) 4, 6
• If intravascular flow detected, reposition needle before injecting therapeutic substance 1, 6

Therapeutic Injection

Injection Technique

• After confirming negative intravascular flow, inject steroid mixed with local anesthetic 1, 4
• Observe contrast spread along nerve root and into epidural space 1
• Document final needle position and contrast pattern 1

Radiation Safety Considerations

C-Arm Positioning

• Source-superior position is preferred when working space is required 7
• Source-superior position delivers approximately 2.3 mSv effective dose per case 7
• Source-inferior position with 300mm working space delivers 6.8 mSv (nearly 3 times higher) 7
• Scatter dose to operator remains below 10% of recommended limits for hands, thyroid, and eyes in source-superior position 7

Fluoroscopy Time

• Average fluoroscopy time: 1.4 minutes per case or 0.33 minutes per screw 7
• Minimize fluoroscopy time by using predetermined angle settings as starting points 3

Common Adverse Events and Management

Immediate Complications (9.2% incidence)

• Vasovagal reaction (4.2%): most common immediate adverse event 6
• Intravascular flow requiring procedure interruption (1.7%): reposition needle and re-confirm with contrast 6

Delayed Complications (20.0% incidence within 24-72 hours)

• Pain exacerbation (5.0%) 6
• Injection site soreness (3.9%) 6
• Headache (3.9%) 6
• Facial flushing/sweating (1.8%) 6
• Insomnia (1.6%) 6

Risk Factors for Adverse Events

• Female gender associated with higher complication rates 6
• Younger age associated with higher complication rates 6
• Higher preprocedure pain scores associated with higher complication rates 6
• Longer fluoroscopy time associated with higher complication rates 6
• Important note: Trainee involvement does NOT increase complication rates 6

Critical Safety Warnings

Shared decision-making must include specific discussion of potential serious complications including dural puncture, insertion-site infections, sensorimotor deficits, cauda equina syndrome, discitis, epidural granuloma, and retinal complications. 1, 8, 9