Classical thermolesion (RFA – Radiofrequency Ablation, radiofrequency neurotomy) is a gold-standard technique, proven over decades, for the durable deactivation of the sensory nerves responsible for chronic pain in the facet joints of the spine, knees, hips and other musculoskeletal structures. Following a positive diagnostic block, RFA provides long-lasting relief without the need for surgery.

What is Classical RFA Thermolesion?

Classical thermolesion involves the introduction of a special needle with a built-in electrode under fluoroscopic X-ray (C-arm) or ultrasound guidance into close proximity to the sensory nerve transmitting pain from the affected joint or structure. Once the needle is precisely positioned, the generator produces a radiofrequency current (approximately 480 kHz) at its tip. The friction of ions in the tissue generates controlled heat – the temperature at the electrode tip is maintained at approximately 80–90°C for 90 seconds, causing thermal denaturation of the nerve proteins and its permanent deactivation from pain conduction.

The first description of thermolesion for treating facet joint pain dates from 1975 (Shealy). Since then the technique has been standardised and is one of the best-documented procedures in pain medicine (Level II evidence per international guidelines).

Mechanism of Action – Why Does Ablation Provide Long-Lasting Relief?

  • Thermal denaturation of structural proteins of C and Aδ nerve fibres (pain fibres) – their conductance is interrupted
  • A precise, elliptical lesion is created along the needle axis (which is why parallel alignment to the nerve is critical)
  • Recent studies (McCormick 2015, Provenzano 2020) confirm that 90°C increases functional efficacy 3.1-fold compared with 80°C – hence our protocol is based on 80–90°C depending on location
  • For spinal joints, 2–4 ablations are performed at each level – ensuring complete denervation (each joint is innervated by ≥2 medial branches)
  • Needles with 3 deployable tines (3-tined cannula, e.g. Nimbus) or 10 mm active tips – increase lesion volume and reduce the risk of inadequate nerve coverage
  • After nerve regeneration (6–24 months), the procedure can be repeated with similar efficacy – studies (Son 2010) show 85% efficacy for repeat procedures

Indications – When is Classical Thermolesion Effective?

RFA is only performed after a positive diagnostic block (>50% pain reduction), confirming that the nerve in question is genuinely conducting and generating pain. The most common indications are:

  • Facet joint pain syndrome – lumbar, thoracic and cervical spine – ablation of medial branches of spinal nerves
  • Chronic neck pain due to degenerative changes of C2–C7 joints
  • Third occipital nerve (TON) at the C2–C3 level – for neck and occipital pain
  • Knee joint thermolesion – genicular nerves
  • Shoulder joint thermolesion – suprascapular nerve
  • Hip joint thermolesion – branches of the obturator and femoral nerves
  • Small joints (e.g. wrist, small foot joints) with documented pain origin
  • Patients in whom pharmacotherapy, physiotherapy and steroid blocks have not provided lasting relief

Step-by-Step Procedure

  • Qualifying consultation and performance of a diagnostic medial branch block (MBB) – if the patient experiences at least 50–75% pain reduction, they are a good candidate for RFA.
  • Patient positioning on the procedure table (typically prone for the spine). Local anaesthesia of the skin is administered.
  • Under fluoroscopic X-ray guidance (with lateral and oblique projections), special RFA needles are introduced parallel to the nerve axis – the so-called parallel technique ensures maximum nerve-to-lesion coverage.
  • Sensory stimulation (50 Hz) and motor stimulation (2 Hz) are performed – the patient confirms correct localisation (feels ‘their’ pain with no muscle contraction).
  • After local anaesthesia (1 ml 2% lidocaine), the generator produces 80–90°C for 90 seconds at each point. The procedure is repeated 2–4 times at different levels to ensure complete ablation.
  • The procedure takes 45–90 minutes depending on the number of levels treated. After the procedure the patient is observed for 30 minutes and goes home with a third-party driver.

Preparation

  • Prior diagnostic block (MBB) with documented positive response
  • Current imaging studies: X-ray, MRI or CT of the spine
  • Discontinuation of anticoagulants per individual recommendation (NOACs, warfarin – minimum 3–5 days before; low-dose aspirin usually without interruption)
  • No need to fast (unless sedation is planned)
  • No driving for 24 hours after the procedure – return transport required
  • Absolute contraindications: pregnancy, active skin infection at the puncture site, uncontrolled coagulopathy, allergy to local anaesthetics

Effects

  • First relief: 1–3 weeks after the procedure (during which post-procedural denervation pain subsides)
  • Full effect: 4–6 weeks
  • Duration of effect: typically 9–12 months (in some studies up to 24 months or longer)
  • 60–70% of patients achieve complete or near-complete pain resolution (data from major centres)
  • After nerve regeneration, pain may return – the procedure can be safely repeated with similar efficacy
  • Best results are achieved in combination with physiotherapy, manual therapy and an individualised deep core muscle strengthening programme

Possible Side Effects

  • Burning, itching pain in the procedure area for 1–2 weeks (denervation effect – physiological)
  • Minor haematoma or tenderness at the puncture site
  • Transient area of numbness (paraesthesia) in the innervation field of the ablated nerve
  • Very rarely – spinal nerve injury (if technique deviates) – we employ 3-stage safeguards: sensory stimulation, motor stimulation and X-ray guidance
  • Occasionally – absence of satisfactory relief despite a positive diagnostic block

FAQ

Is classical RFA thermolesion safe?

Yes – RFA has been used in pain medicine for over 50 years and has the best-documented efficacy among neurodestructive procedures. At our Centre we exclusively use fluoroscopic X-ray guidance with sensory-motor stimulation, minimising the risk of complications.

How does RFA differ from PRF (pulsed thermolesion)?

RFA destroys the nerve with high temperature (80–90°C) – the effect is durable but requires good anatomical coverage. PRF acts in a modulatory manner at low temperature (42°C), does not destroy the nerve, but the effect is usually shorter. RFA is chosen for purely sensory nerves (medial branches, genicular nerves); PRF – for mixed (sensory-motor) nerves or where nerve function needs to be preserved.

What if the pain returns after a year?

Return of pain after 9–18 months is natural – it results from regeneration of the ablated nerves. The procedure can be safely repeated and studies (Son 2010) show 85% efficacy for the next procedure. In some patients the effect lasts 2–3 years or longer.