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Indications / Contraindications
Indications
- Lumbar radiculopathy (sciatica) — L4, L5, or S1 nerve root pain from disc herniation or foraminal stenosis; pain radiating below the knee in dermatomal pattern
- Neurogenic claudication from lumbar spinal stenosis (interlaminar approach preferred)
- Failed conservative management ≥ 6 weeks (NSAIDs, physical therapy, activity modification)
- Post-surgical radiculopathy (failed back surgery syndrome — epidural fibrosis, residual stenosis)
- Acute disc herniation with severe pain — bridge to natural resolution or surgery
- Transforaminal preferred: Single-level unilateral radiculopathy; level-specific steroid delivery; post-surgical anatomy; diagnostic injection to confirm target level
- Interlaminar preferred: Bilateral or multilevel symptoms; central stenosis; post-fusion anatomy; central disc herniations
Contraindications
- Absolute: Active spinal infection · Uncorrectable coagulopathy · Allergy to contrast or corticosteroids
- Anticoagulation (SIR Category 2 — moderate risk): INR ≤1.5, platelets ≥50K required. Warfarin: hold 5 days (verify INR ≤1.5 day-of). LMWH: hold 24h (therapeutic); hold 12h (prophylactic). DOACs: hold 24–48h. Heparin IV: hold 4–6h. Aspirin: continue. Clopidogrel / P2Y12 inhibitors: hold 5–7 days (epidural hematoma risk)
- Relative: Prior spinal fusion at target level (use CT guidance); uncontrolled diabetes; pregnancy; coagulopathy not fully correctable
- Note: Bridging anticoagulation is an individualized decision. Consult prescribing team for high-thrombotic-risk patients (mechanical heart valves, AF with CHA₂DS₂-VASc ≥4, VTE <3 months, recent coronary stent). NSAID / aspirin does NOT routinely need to be held for LESI per SIR guidelines
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Pre-Procedure Checklist
MRI review. Identify pathology level and laterality. Disc herniation vs. foraminal stenosis vs. central stenosis. Determine approach (transforaminal vs. interlaminar). Assess for post-surgical hardware that may require CT guidance.
Labs. PT/INR and platelet count required before epidural injection. Target INR ≤1.5–1.8; platelets ≥50 × 10⁹/L. Epidurals carry higher bleeding risk than simple Cat 1 joint injections.
Anticoagulation (SIR Cat 2 — moderate risk). Warfarin: hold 5 days (INR ≤1.5 day-of); DOACs: hold 24–48h; LMWH: hold 24h therapeutic / 12h prophylactic; Heparin IV: hold 4–6h. Aspirin: continue. Clopidogrel/P2Y12: hold 5–7 days (epidural hematoma risk).
Approach selection. Transforaminal for unilateral radiculopathy; interlaminar for bilateral/stenosis. Document selected approach, level, and laterality in plan before starting.
Steroid selection. Use non-particulate steroid (dexamethasone 8–10 mg) for ALL transforaminal approaches — particulate steroid (triamcinolone, methylprednisolone) in radicular artery = spinal cord infarction. Interlaminar approach: either particulate or non-particulate acceptable.
Consent. Discuss: dural puncture headache, epidural hematoma (rare; increased with anticoagulation), intravascular injection / cord infarct (rare; prevented by live fluoroscopy + contrast), transient lower extremity weakness from local anesthetic (requires a driver), infection, failure to relieve pain.
NPO not required. Sedation is not necessary and not recommended — alert patient can communicate symptom changes (paresthesias, motor block) in real time during injection.
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Relevant Anatomy
Epidural Space
- Posterior epidural space at L3-5 is the target — widest at L3-4 (7–9 mm); posterior epidural fat provides "cushion" and drug distribution medium
- Bounded posteriorly by ligamentum flavum; anteriorly by posterior longitudinal ligament and posterior disc/vertebral body
- Spinal cord ends at L1-2 (conus medullaris) — below L2, only the cauda equina floats in the CSF; true intrathecal injection below L2 is less catastrophic than above, but still requires detection
- Anterior epidural space contains Batson's venous plexus — rich, valveless venous network; intravascular injection risk is real and must be checked before every medication injection
- Posterior epidural space can communicate between levels — but drug delivery is most targeted with transforaminal approach directly onto the affected nerve root
Transforaminal Safe Zone
- Safe triangle (subpedicular approach): Superior border = pedicle undersurface; inferior border (hypotenuse) = dorsal root ganglion; lateral border = lateral foraminal margin
- Needle target: 6 o'clock position of the pedicle on AP view — inferior and slightly medial; in the superior posterior neural foramen, posterior to the nerve root
- Kambin's triangle (alternative): inferior border = pedicle; superior border = dorsal root ganglion; medial border = articular process — useful when safe triangle is inaccessible (hardware)
- Artery of Adamkiewicz: Usually left T9-L1; can rarely extend to lumbar range — explains why particulate steroid into the radicular artery causes cord infarct
- Radicular arteries and venous plexuses are present within every neural foramen — aspirate and use live fluoroscopy with contrast before every injection
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Technique
Default RadCall approach · share your own below
Supplies
22G or 25G spinal needle (Quincke / Chiba)
C-arm fluoroscopy
Omnipaque 180 or 240 (contrast)
Extension tubing (primed, air-free)
1 mL + 3 mL syringes
Dexamethasone 8–10 mg (transforaminal)
Triamcinolone 40–80 mg (interlaminar)
0.25% bupivacaine or 1% lidocaine
Loss-of-resistance syringe (interlaminar)
ChloraPrep
Sterile drape
Sterile dressing
Approach A — Transforaminal LESI
Steps
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Positioning + oblique view
Patient prone. Rotate C-arm to ipsilateral oblique 15–30° until "Scottie dog" view appears — pedicle projects as an oval. Identify the target pedicle (e.g., L4 pedicle for L4 nerve root injection).
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Skin entry + needle advance
Local anesthesia at skin. Advance 22G spinal needle in the 6 o'clock position of the pedicle — target the inferior and slightly posterior aspect of the pedicle. Use tunnel view (looking directly down the needle in the AP oblique). Advance until the tip projects just inferior and medial to the pedicle on AP view.
▶ TF — needle at "safe triangle"
Transforaminal approach: needle at the “safe triangle” — inferolateral to pedicle, above exiting nerve root; oblique view confirms position before advancing.
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AP + lateral confirmation
AP: needle tip at 6 o'clock of pedicle, not crossing medial pedicle margin (would be intrathecal). Lateral: needle at posterior foramen — do NOT advance anterior to the posterior vertebral body line (epidural venous plexus / disc). Tip should be in the posterior neural foramen.
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Aspirate + contrast injection
Aspirate — no blood, no CSF. Attach primed extension tubing. Inject 1–2 mL contrast under LIVE fluoroscopy (AP view). Look for: nerve root sleeve opacification and epidural spread (acceptable). STOP immediately if: linear flow in vessel (intravascular), contrast entering spinal canal in a column (intrathecal). If vascular: reposition needle before proceeding.
▶ TF — epidurogram confirming spread
Transforaminal epidurogram: contrast outlining the nerve root sleeve and flowing medially into the epidural space — confirms pre-neural placement before steroid injection.
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Inject steroid + anesthetic
Confirmed epidural spread: inject 1 mL dexamethasone 8–10 mg (non-particulate — mandatory for transforaminal) + 1–2 mL 0.25% bupivacaine. Total volume 2–3 mL. Inject slowly. Communicate with awake patient — paresthesias are common and expected; STOP if severe pain or new motor symptoms appear.
Approach B — Interlaminar LESI
Steps
1
Positioning + target level
Patient prone. AP fluoroscopy. Target L4-5 or L3-4 interlaminar space — typically the most caudal accessible level above the pathology. Paramedian approach (ipsilateral to symptoms if unilateral).
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Loss-of-resistance needle advance
Advance 22G Tuohy or Quincke needle from midline or paramedian angle, aiming for the interlaminar space. Attach loss-of-resistance syringe with saline. Advance through supraspinous ligament → interspinous ligament → ligamentum flavum — firm resistance. LOR (sudden give) indicates epidural entry. Confirm on lateral view: tip at posterior epidural space.
▶ IL — needle in posterior epidural space
Interlaminar approach: Tuohy needle at posterior epidural space via loss-of-resistance — lateral view confirms tip just anterior to ligamentum flavum, not intrathecal.
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AP + lateral confirmation
AP: tip midline or slightly ipsilateral. Lateral: tip at posterior epidural line. Do not advance past the posterior vertebral body line. Aspirate: no CSF (dural puncture), no blood (vascular).
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Contrast injection — "Christmas tree"
Inject 2–3 mL contrast under live fluoroscopy. Epidural spread: bilateral midline spread along ligamentum flavum / posterior epidural space (classic "Christmas tree" or "angel wing" pattern on AP view). Intrathecal: dye outlines nerve roots in sharply defined columns — abort.
▶ IL — "Christmas tree" epidurogram
Interlaminar epidurogram: bilateral “Christmas tree” spread confirms epidural placement — if intrathecal (myelographic pattern), withdraw needle and redirect.
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Inject steroid + anesthetic
Confirmed epidural: inject triamcinolone 40–80 mg or methylprednisolone 80 mg + 2–3 mL 0.25% bupivacaine. Total volume 4–5 mL. Inject slowly over 60–90 seconds. Communicate with patient throughout.
Approach C — Caudal Epidural (Alternative)
Access via sacral hiatus with 22G spinal needle; confirm in sacral canal on lateral view; inject 10–15 mL dilute steroid/anesthetic. Useful for L5-S1 access in post-surgical patients or when superior approaches are inaccessible. Higher total drug volume required for cephalad spread to lumbar levels.
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Troubleshooting
Problem
Intravascular contrast uptake — linear flow in vessel
Likely cause: Needle tip in epidural venous plexus (Batson's) or periforaminal radicular artery. More common with transforaminal approach and in post-surgical patients (distorted anatomy).
Next step: STOP injection immediately. Withdraw needle 1–2 mm; redirect slightly. Re-aspirate. Repeat contrast under live fluoroscopy before any steroid. If repeatable vascular uptake: try different trajectory. Consider switching to non-particulate dexamethasone if not already. Do NOT inject particulate steroid with any vascular uptake.
Problem
CSF return on aspiration (dural puncture)
Likely cause: Needle advanced too far anteriorly into the thecal sac. More common with interlaminar approach or when epidural fat is thin (prior surgery, spinal stenosis).
Next step: Do not inject steroid intrathecally. Withdraw needle back into epidural space and re-confirm with contrast. If intrathecal injection desired (rare — selective nerve root block): reduce volume to ≤1 mL and use preservative-free dexamethasone only. If accidental intrathecal: observe for spinal headache, total spinal anesthesia (bilateral leg weakness); most intrathecal dexamethasone injections at lumbar level are tolerated without permanent injury.
Problem
Unilateral contrast spread — drug not reaching target root
Likely cause: Midline septum or post-surgical adhesions limiting epidural spread in interlaminar approach; needle too far lateral in transforaminal.
Next step: For interlaminar: reposition needle to ipsilateral paramedian and repeat. Consider contralateral injection if bilateral symptoms. For transforaminal: confirm needle at 6 o'clock of pedicle; increasing volume slightly (up to 3 mL) can improve spread. Re-image with contrast before additional medication.
Problem
Severe radiculitis / paresthesias during injection
Likely cause: Needle tip too close to the nerve root (contact); or rapid injection into tightly stenosed foramen (pressure effect).
Next step: Stop injection immediately. Ask patient to describe: severe lancinating pain in dermatomal pattern = nerve contact → withdraw needle 1–2 mm. Diffuse burning = possible intravascular. Resume injection very slowly (0.5 mL/min maximum). If motor symptoms develop (quadriceps weakness): stop and monitor before considering additional medication.
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Complications
Serious / Rare
- Spinal cord infarction — intravascular injection of particulate steroid into radicular artery; may cause paraplegia; prevention: live fluoroscopy + contrast before every steroid injection; use dexamethasone for all transforaminal approaches
- Epidural hematoma — rare (<1:150,000 epidurals); risk elevated with anticoagulation; presents with back pain + progressive leg weakness post-procedure; MRI urgently; neurosurgical consultation for decompression
- Epidural abscess — rare; fever, back pain, neurological deficits days–weeks post; MRI with contrast; IV antibiotics; surgical drainage if cord compression
- Total spinal anesthesia — inadvertent large-volume intrathecal injection; rapid bilateral sensory/motor block + hypotension; supportive care, airway management
Common / Minor
- Transient lower extremity weakness — from local anesthetic dorsal root block; resolves in 2–6h; patient must have a driver; observe until fully resolved before discharge
- Post-dural puncture headache — positional headache (worse upright, better supine) after accidental dural tap; conservative management (supine, caffeine, analgesics); blood patch if refractory
- Post-injection flare — temporary pain increase 1–3 days; resolves spontaneously; warn patient prior to discharge
- Hyperglycemia — steroid effect; especially in diabetics; monitor 24–48h; insulin adjustment if needed
- Vasovagal reaction — common; patient must remain supine during procedure; treat with fluids ± atropine
- Arachnoiditis — rare; associated with large volumes, intrathecal injection of particulate material, or preservatives; avoid by using preservative-free medications intrathecally
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Post-Procedure Care
Recovery Monitoring
- Observe 30–60 min — assess for lower extremity weakness from local anesthetic; patient must fully recover motor function before discharge
- Motor block from bupivacaine: document and reassess q15–20 min; typically resolves within 60–90 min
- Cannot drive for 12–24 hours after procedure — arrange transportation in advance
- Monitor for signs of dural puncture: headache onset (positional, throbbing) — instruct patient to call if this develops
- Vitals q30 min × 1h in recovery; discharge when ambulating safely
Expected Response + Follow-up
- Steroid onset: 2–5 days after injection; full effect at 2 weeks
- Local anesthetic effect: Immediate but temporary (hours); may provide early symptom insight
- Reassess at 2–4 weeks. Document: degree of pain relief (%), functional improvement, return-to-activity milestones
- >50% relief with first injection — good predictor for continued benefit; may repeat if symptoms recur
- Series limit: Maximum 3 injections per 6-month period (evidence-based; beyond this, diminishing returns and increasing steroid-related side effects)
- If inadequate relief after 2 injections: reassess diagnosis; consider surgical consultation, alternative nerve root, or different pain source
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Provide patient with a pain diary to track daily pain scores before their follow-up visit — helps calibrate treatment response and guides repeat intervention decisions.
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Critical Pearls
✶
Dexamethasone only for transforaminal. Non-particulate steroid (dexamethasone 8–10 mg) is mandatory for transforaminal LESI. Particulate steroids (triamcinolone, methylprednisolone) form aggregates that can occlude radicular arteries and cause spinal cord ischemia. Interlaminar approach: either is acceptable because the delivery site is further from foraminal vessels.
✶
Live fluoroscopy + contrast before every steroid injection — no exceptions. Aspirate first, then inject contrast under real-time fluoroscopy. A static spot film after contrast injection is insufficient — vascular flow may appear and clear before the image is taken. Watching the contrast move in real time is the only way to detect intravascular placement reliably.
✶
Transforaminal is more targeted than interlaminar for unilateral radiculopathy. The transforaminal approach places steroid directly at the epidural axilla of the inflamed nerve root, achieving much higher focal drug concentration than interlaminar injection. For single-level unilateral radiculopathy with clear dermatomal symptoms correlating to imaging: transforaminal is the preferred approach.
✶
Keep the patient awake and communicating. Sedation is not needed and removes your safety net. An alert patient can report paresthesias (nerve root contact), new numbness (intravascular), or worsening pain (pressure injection) in real time. This information changes your management. NPO is not required — the patient just needs a driver.
✶
Caudal approach for L5-S1 access. When the L5-S1 foramen is narrowed by severe disc-osteophyte complex, the interlaminar L5-S1 space is obliterated by hardware, or standard transforaminal access is blocked, the caudal epidural approach via the sacral hiatus is a reliable alternative. Requires larger total volume (10–15 mL) for cephalad spread. Confirm sacral canal placement on lateral fluoroscopy before injecting.
✶
Steroid benefit is temporary — address the underlying pathology. Epidural steroid injections reduce inflammation around the nerve root and provide a window of pain relief. They do not reverse disc herniation or correct stenosis. Use this window to advance physical therapy and functional recovery. If three injections provide only transient benefit with rapid relapse, surgical consultation is appropriate.
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References & Approach Comparison
Approach Comparison: Transforaminal vs. Interlaminar vs. Caudal
| Feature | Transforaminal | Interlaminar | Caudal |
|---|---|---|---|
| Best for | Single-level unilateral radiculopathy; level-specific delivery; post-surgical anatomy; diagnostic injection | Bilateral symptoms; central stenosis; multilevel disease; neurogenic claudication | L5-S1 when other approaches blocked; post-fusion; sacral radiculopathy |
| Steroid | Dexamethasone ONLY (non-particulate mandatory) | Triamcinolone or methylprednisolone (particulate acceptable) | Either acceptable; dilute with larger volume (10–15 mL) |
| Vascular risk | Higher — needle near foraminal vessels; live fluoro mandatory | Lower — posterior epidural space away from main vessels | Low — sacral canal far from cord; rich venous plexus still present |
| Volume | 2–3 mL total | 4–6 mL total | 10–15 mL total |
| Targeting precision | High — directly at nerve root axilla | Moderate — spreads bilaterally via posterior epidural space | Low — dilution over multiple levels; least precise |
| Guidance | Fluoroscopy (standard); CT for post-surgical or hardware | Fluoroscopy; CT for post-surgical | Fluoroscopy lateral view mandatory |
Citations
- Prologo JD, Ray CE Jr., eds. Advanced Pain Management in Interventional Radiology: A Case-Based Approach. Thieme; 2024. DOI: 10.1055/b000000387
- Filippiadis DK, Kelekis A. A review of current trends in spinal interventional procedures for the management of chronic spinal pain. Quant Imaging Med Surg. 2017;7(6):651–659.
- Mitchell JW. Radicular Pain Related to Disk Disease I: Transforaminal Injections. In: Prologo JD, Ray CE Jr., eds. Advanced Pain Management in Interventional Radiology. Thieme; 2024: Chap 26.
- Manchikanti L, et al. Epidural injections for lumbar radiculopathy or sciatica: a systematic review and meta-analysis. Pain Physician. 2020;23(4S):S185–S238.
- Bensler S, et al. Fluoroscopy-guided lumbar transforaminal epidural steroid injections: a systematic review and meta-analysis. Eur Radiol. 2018;28(2):618–629.
- SIR Standards of Practice Committee. Consensus Guidelines for Periprocedural Management of Coagulation Status and Hemostasis Risk. J Vasc Interv Radiol. 2012;23(6):727–736.
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References & Resources
Primary sources · Key data · Related procedures
Key Guidelines
- ISIS Practice Guidelines
- ASIPP Evidence-Based Guidelines for LESI
- ACR Appropriateness Criteria
Primary References
- Manchikanti L et al. Comprehensive evidence-based guidelines for interventional techniques in the management of chronic spinal pain. Pain Physician. 2009;12(4):699-802.
- Abdi S et al. Epidural steroids in the management of chronic spinal pain: a systematic review. Pain Physician. 2007;10(1):185-212.
- Vad VB et al. Transforaminal epidural steroid injections in lumbosacral radiculopathy. Spine. 2002;27(1):11-16.