Lumbar Interlaminar Epidural Steroid Injection

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Pre-Procedure0/2

Perform time-out: verify patient identity, procedure, level, allergies, and anticoagulation status.

Review coagulation status per ASRA guidelines. Interlaminar approach has higher risk of epidural hematoma than transforaminal.

The interlaminar approach accesses the dorsal epidural space. It is less selective than transforaminal but may provide bilateral coverage for central pathology.

Review imaging to identify target interlaminar level and assess for ligamentum flavum hypertrophy or epidural lipomatosis.

Avoid levels with prior laminectomy where the ligamentum flavum may be absent, increasing dural puncture risk.

At post-laminectomy levels, the protective ligamentum flavum barrier is disrupted. Consider an adjacent intact level or contralateral paramedian approach.

Setup0/2

Position patient prone with pillow under the abdomen. Prep and drape the lumbar region.

Ensure adequate monitoring and IV access. Have resuscitation equipment available.

The prone position with abdominal support reduces epidural venous engorgement by decreasing intra-abdominal pressure, reducing bleeding risk.

Set up C-arm in AP view with squared endplates. Identify the target interlaminar space and mark skin entry point.

Use a paramedian or midline approach based on the interlaminar window size. Narrow windows may require contralateral oblique.

The contralateral oblique view can open a narrow interlaminar window by rotating the beam away from the target side, effectively widening the apparent gap between laminae.

Procedure0/5

Select a 17- or 18-gauge Tuohy needle (or 20-gauge for thinner patients). Advance to the ligamentum flavum using intermittent fluoroscopy.

The Tuohy needle has a curved tip designed to tent the dura rather than puncture it. Advance with bevel facing cephalad.

The ligamentum flavum is typically 3-5 mm thick in the lumbar spine and provides a distinct change in resistance (loss of resistance technique).

Perform loss-of-resistance (LOR) technique with saline or air to identify the epidural space.

Use gentle, controlled pressure. A sudden loss of resistance confirms epidural entry. Aspirate to check for CSF or blood.

LOR to saline is preferred by many practitioners as air can cause pneumocephalus or patchy block. The hanging-drop technique is an alternative.

Confirm needle depth on lateral fluoroscopy: the tip should be at the dorsal epidural space, posterior to the posterior vertebral body line.

If CSF is aspirated, the needle has penetrated the dura. Remove and either abort or reattempt at a different level.

On lateral view, the ventral epidural space lies between the posterior vertebral body line and the thecal sac. The dorsal space is between the thecal sac and the ligamentum flavum.

Inject 1-2 mL of contrast to confirm epidural spread and exclude intrathecal or intravascular placement.

Intrathecal contrast will show a myelogram pattern (outlining nerve roots within the thecal sac). Epidural contrast hugs the dorsal sac.

Epidural contrast spreads in a characteristic 'Christmas tree' pattern on AP view, with streaks along nerve root sleeves bilaterally.

Inject injectate: typically 80 mg triamcinolone or 80 mg methylprednisolone in 2-3 mL total volume with preservative-free saline.

Particulate steroids may be used for interlaminar approach as the needle is posterior to the epidural vasculature.

Unlike transforaminal, the interlaminar needle tip is in the dorsal epidural space, distant from the radiculomedullary arteries, making particulate steroids acceptable.

Post-Procedure0/1

Remove needle and monitor patient for 20-30 minutes. Assess for headache (dural puncture), new weakness, or hypotension.

Post-dural puncture headache (PDPH) presents as positional headache worse when upright. If suspected, consider epidural blood patch.

PDPH risk is higher with larger gauge needles and multiple attempts. Onset is typically within 24-48 hours of the procedure.