Radiofrequency Ablation (RFA) for Facet Pain

RFA Technique Essentials

Radiofrequency ablation uses thermal energy to create a lesion that interrupts the medial branch nerve, preventing pain signal transmission from the facet joint.

Step-by-Step Procedure

1. Patient positioning: Prone on fluoroscopy table
2. Level identification: AP fluoroscopy to identify target transverse processes at each level
3. Electrode placement: The RF electrode (typically 18-22 gauge cannula with active tip) must be placed PARALLEL to the medial branch nerve along the junction of the transverse process and SAP
4. Why parallel matters: Standard thermal RFA creates a lesion approximately 1 cm long by the width of the electrode shaft. Parallel placement maximizes contact between electrode and nerve. Perpendicular placement may miss the nerve entirely.
5. Confirm position: AP and lateral fluoroscopy
6. Sensory stimulation: At 50 Hz — concordant pain reproduction at <0.5 V suggests optimal placement near the target nerve
7. Motor stimulation: At 2 Hz — should see multifidus muscle contraction (confirming medial branch proximity) and absence of limb motor response at <2.0 V (confirming the electrode is not near a motor nerve root)
8. Local anesthetic: Inject 0.5-1 mL of local anesthetic before each lesion to reduce procedural pain
9. Lesion creation: Heat to 80-85 degrees C for 60-90 seconds per lesion
10. Multiple lesions: Consider creating 2-3 overlapping lesions per level to increase the probability of capturing the nerve

Lesion Parameters

| Parameter | Standard Value | |-----------|---------------| | Temperature | 80-85 degrees C | | Duration | 60-90 seconds | | Sensory stimulation | 50 Hz, <0.5 V | | Motor stimulation | 2 Hz, no limb response at <2.0 V | | Lesion size | ~1 cm long x electrode diameter |

IPSIS Cervical RFN Technique Details

The IPSIS evidence-based technique for cervical medial branch radiofrequency neurotomy (CMBRFN) has specific hallmarks:

Cannula and Electrode Selection

• Large-gauge cannulae (16G or 18G) with a 10 mm sharp, bent active tip are preferred
• Available in 100 mm and 145 mm lengths
• The RF cannula bevel direction is non-coincident with the hub notch (opposite of spinal needles) — the cannula deflects toward the hub notch/dot marking
• Recent consensus guidelines have advised safety studies before using alternative technologies (bipolar, cooled RF, multi-tined) in the cervical spine

Cervical Target Zones

• Because medial branches assume variable positions relative to their articular pillars, there is no single electrode placement point — instead, there is a zone of likely nerve location that must be covered
• Typical levels (C3-6): The C5 medial branch is consistently at the mid-pillar; C3, C4, and C6 branches are progressively higher. Two parallel large-gauge cannula placements in the middle and upper aspects of the lateral pillar are typically needed
• C5 level: May only need one cannula placement if using 16G
• C7 medial branch: Three lesion locations needed (C7 SAP apex, SAP base, and root of the transverse process). The narrow C7 SAP requires a near-sagittal or slightly (5 degrees) ipsilateral oblique trajectory to avoid passing into the C6-7 neural foramen
• Third occipital nerve (TON): Three lesion locations along the C2-3 joint (equator, cephalad, caudal to joint)

Critical Safety — Depth Control

• The cannula tip must NEVER advance ventral to the anterior margin of the articular pillar (C3-6) or the SAP (C7/TON)
• Foraminal oblique views provide essential auxiliary imaging to verify the cannula is safely posterior to the cervical foramen and exiting nerve/vertebral artery
• If the physician is uncertain about cannula position relative to vulnerable structures, RF lesioning should NOT commence

Cervical Lesion Parameters

• Temperature: 80-85 degrees C for at least 90 seconds per lesion
• Multiple tightly overlapping lesions are made to cover the entire zone of nerve probability
• The cannula must be manually held in place during lesioning if it is mobile

IPSIS Lumbar RFN Technique Details

Cannula Trajectory and Placement

• 15-20 degrees ipsilateral obliquity helps avoid the mamillo-accessory ligament (MAL) when positioning the cannula alongside the nerve
• Excessive obliquity (25-30 degrees) results in a more transverse approach that is less parallel to the nerve and less effective
• A declined fluoroscopic tilt of approximately 35-40 degrees is required to parallel the nerve as it crosses the lateral SAP base
• True lateral imaging establishes cannula depth: the active tip should overlie the middle two-fourths of the lateral SAP for L1-4 medial branches
• For the L5 dorsal ramus, the cannula should be over the posterior two-thirds of the S1 SAP

Avoiding Collateral Nerve Injury

• Do NOT lesion over the ventral one-fourth of the SAP (L1-4) or ventral one-third of the S1 SAP (L5 DR) to avoid lateral/intermediate branch injury
• Do NOT lesion over the posterior one-fourth of the SAP (L1-4) where the nerve may escape beneath the MAL
• This MAL concern does not apply to the L5 DR target (MAL is rudimentary/absent at S1)

Lumbar Lesion Parameters

• Temperature: 80-85 degrees C for 90 seconds
• A properly placed single 16G cannula should cover all possible medial branch locations at a given level
• If using 18G or smaller, additional placements and lesions are needed to create an equivalent lesion zone
• For the L5 DR, the deep sulcus means a second higher lesion placement is usually unnecessary; instead, the cannula can be withdrawn 3-5 mm to extend the lesion length

Advanced Technology: Cooled RF

Cooled radiofrequency is a newer technology that internally cools the electrode tip during lesioning:

• Creates larger, more spherical lesions compared to conventional RF
• May improve nerve capture rates, especially for anatomically variable nerves
• Particularly useful for SI joint lateral branch ablation where nerve courses are variable
• Most positive SI joint RFA studies use cooled RF technology

Post-Procedure Expectations

• Onset of relief: May take 2-6 weeks due to Wallerian degeneration of the nerve
• Temporary neuritis: ~5% of patients experience temporary worsening of pain for 1-4 weeks as the nerve degenerates
• Full effect: Typically achieved by 6-8 weeks post-procedure
• Patients should be counseled about the delayed onset to prevent premature conclusions of failure