Principles and types of radiofrequency therapy
There are two main approaches to radiofrequency treatment of pain syndromes, which differ in physical parameters and indications:
- Pulsed radiofrequency (PRF). A method with a high level of evidence for treating cervical radicular pain, chronic shoulder pain, and trigeminal neuralgia. It is applied to the dorsal root ganglia (ganglion spinale). Standard parameters: voltage 45 V, frequency 2 Hz, total session duration 4 minutes. Its efficacy in the lumbosacral region remains controversial.
- Continuous thermal radiofrequency ablation (CRF). Considered the "gold standard" for relieving pain in facet syndrome. Alternating current causes tissue heating and Wallerian degeneration of pain Aδ- and C-fibers, interrupting impulse transmission.
Facet syndrome and radiofrequency neurotomy
Facetogenic pain is axial (mechanical) in nature and arises due to the degeneration of the zygapophyseal joints (zygapophyseal joints). This is one of the most common causes of lower back pain.
For long-term pain relief, denervation of the medial branch of the posterior spinal nerve is performed:
- Positioning and access: The patient lies prone. The needle is inserted under fluoroscopic guidance in an oblique projection (the landmark is the "scotty dog" figure).
- Insertion technique: A parallel technique is used (in a caudocranial direction). The target is the tip of the transverse process near the superior articular process. This maximizes the contact area of the active cannula tip with the nerve.
- Adjacent level rule: Due to significant overlap in the innervation of the zygapophyseal joints, it is essential to treat adjacent superior and inferior levels.
Specifics of cervical procedures
Cervical radicular pain requires extreme precision and strict adherence to pharmacological restrictions. Interventional treatment involves epidural corticosteroid injection (interlaminar or transforaminal).
- Needle positioning: In the transforaminal approach, the needle tip should be located in the dorsal part of the intervertebral foramen, posterior to the spinal nerve. This prevents accidental puncture of the vertebral artery (arteria vertebralis), which runs anteriorly.
- Choice of drugs: Only particulate-free dexamethasone is permitted. The administration of local anesthetics in the cervical spine is strictly prohibited, as it can lead to transient phrenic nerve palsy and severe central nervous system depression.
Safety and control during RFA
Before turning on the radiofrequency generator to destructive power, a series of checks is always performed:
- Test contrast injection: Necessary to visualize the spread of the drug (it should outline the nerve and spread into the epidural adipose tissue) and to rule out intravascular placement.
- Sensory and motor testing: This is a mandatory step. The tests allow precise reproduction of the patient's pain pattern. If stimulation causes motor contractions in the lower extremities or radiating paresthesia, this is a red flag: the electrode tip is too close to the exiting spinal nerve, and the position must be adjusted immediately.
When performed correctly, complications are minimal, and significant pain relief (greater than 60%) persists until nerve regeneration occurs from the proximal to the distal end (usually within 6–12 months).
Briefly: answers to topical questions
Which spinal structures are innervated by the sinuvertebral nerves (Luschka's nerves)?
The sinuvertebral nerves (meningeal branches) provide sensory innervation to the structures of the spinal canal and intervertebral discs.
Innervated structures include:
- Posterior longitudinal ligament (lig. longitudinale posterius) — the main receptor zone.
- Annulus fibrosus (annulus fibrosus) — its outer layers and dorsal circumference are innervated.
- Dura mater — the connective tissue membrane of the spinal cord.
- Periosteum — the membrane of the bone structures of the vertebra.
- Epidural vessels — blood vessels inside the spinal canal.
- Capsular and ligamentous apparatus — structures of the affected spinal segment.
For successful facet joint denervation, always remember the "neighbors": make sure to treat adjacent superior and inferior levels due to the overlapping innervation of the joint capsule.
Class and exam questions
What radiological landmark is used for access to the lumbar facet joints?
The ipsilateral oblique projection is used, in which the classic landmark is the "scotty dog" projection.
Why can facet syndrome cause pain radiating to the leg (sciatica) when the joint is affected rather than the disc?
Chronic inflammation of the facet joints is often accompanied by ligamentum flavum hypertrophy, which can lead to secondary spinal canal stenosis and nerve root compression.
Why are sensory and motor testing required before delivering destructive RF current?
Testing confirms that the targeted pain fibers are affected while ruling out proximity of the electrode to motor fibers of the spinal nerve, thereby preventing paresis.
Which corticosteroid is used for transforaminal injections in the cervical spine?
Strictly use only particulate-free dexamethasone to avoid microvascular embolism.
What else to study on this topic
- Adhesiolysis using hyaluronidase for postoperative pain
- Epiduroscopy and spinal cord stimulation as backup methods
- Degenerative pathologies of the sacroiliac joint (SIJ)
- Diagnostic algorithm for cervical radiculopathy and search for "red flags"
- Diagnostic medial branch blocks to confirm facet syndrome
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