Radiofrequency

RADIOFREQUENCY ABLATION IN PAIN MANAGEMENT

by Dr Shrutirekha Hota

What exactly is a radiofrequency ablation procedure?

A radiofrequency ablation procedure is a minimally invasive and non-surgical procedure that can be done as outpatient treatment. In this procedure, the nerve fibers carrying pain signals to the brain are destroyed using heat. It is usually performed under image guidance like USG or X-ray. This procedure usually takes 30 minutes. It provides long-term pain relief in patients suffering from chronic neck, back, lower back, osteoarthritis knee, and sacroiliac pain.

Who does the radiofrequency procedure?

The ablation procedure is usually done by a pain management doctor who has been specifically trained to perform it.

  • What are the goals of radiofrequency ablation?
  • Reduces pain for a longer duration.
  • Improves the neck, back, knee, and shoulder functions by improving the range of motion. As a result, the patient returns to work quickly, performs routine activities, and enjoys an active lifestyle.
  • Reduces consumption of pain medications.
  • Avoid or delay surgery- for example, to avoid TKR at a younger age.

Why is it called a radio frequency machine?

The frequency band of radiofrequency is similar to the frequency of radio waves; that is why it is called radiofrequency. The machine uses alternating current with an input frequency of 50Hz and produces 300,000 Hz of alternating current output. The radiofrequency lesioning process involves the passage of a very high-frequency current through a 27G thermocouple probe. The probe is passed through a 14-22G cannula, which is insulated except at the tip where the electromagnetic field generates heat and lesioning occurs.

What are the types of radiofrequency?

Conventional radiofrequency– Here thermocouple probe itself is not heated, and it dissipates heat generated at surrounding tissue. Tip temperature ranges from 65-90 degrees Celsius. Lesion generated is like the shape of a matchstick head with a diameter of 2-4mm. Size of lesion maximum around shaft and minimum around the tip, so needle placement parallel to the nerve is needed. A longer duration of pain relief is attained. Sometimes there might be faulty regeneration of nerves. The failure rate is relatively less.

Pulsed radiofrequency– High-frequency current is delivered in pulses with complete silence in between. Here we can put the needle perpendicular to the nerve as a maximum electric field is generated at the tip. The lesion is due to a strong electromagnetic field (maybe due to stimulation of analgesic chemicals), not temperature. The temperature remains at 42 degrees Celsius. It is safe as there is no nerve damage, so no deafferentation pain. The disadvantages are the high failure rate with a short duration of pain relief.

Cooled radiofrequency– Here, the tip temperature is controlled by circulating cold water through a channel in the needle at room temperature. So we can deliver more extensive power that causes the large size of the lesion. Again, we can put the needle perpendicular to the nerve or any degree.

Bipolar RF– Current flows between two electrodes instead of a ground pad. So there will be a larger size lesion. So here, one electrode produces a large, and one makes a smaller lesion.

Multichannel RF– Here, current passes through the ground pad. Both electrodes produce large size lesions.

How can we increase the size of the radiofrequency lesion?

By using a larger gauge needle

Protruding cannula, trident cannula, venom cannula can be used

By using cooled radiofrequency, bipolar RF

By increasing time up to 150 sec

Who are the candidates of radiofrequency?

Conventional radiofrequency–

Patients have trigeminal neuralgia with failed conservative treatments for Gasserian ganglion block.

Sphenopalatine ganglion block for chronic head/facial pain like trigeminal neuralgia, TMJ pain, cluster headache, CRPS

Occipital neuralgia – 3rd occipital nerve RFA

Cervical, thoracic, and lumbar facet arthropathy- RFA  of medial branches done for long term relief of pain in patients with chronic pain and conditions such as arthritis of the spine (spondylosis)

T2, T3 sympathetic nerve RFA has been done in case of pain arising from the upper and middle back, e.g., CRPS.

Splanchnic nerve RFA- Done in chronic pancreatitis pain refractory to medical management.

Lumbar sympathetic RFA has been done in patients with CRPS of the lower limb as well as for pain of ischaemic origin, e.g., Thromboangitis obliterans.

Pulsed radiofrequency–

Occipital neuralgia

Suprascapular nerve RFA for adhesive capsulitis, frozen shoulder, rotator cuff tear, degenerative or inflammatory glenohumeral arthritis.

Cervical/thoracic/lumbar DRG radiofrequency is done in chronic post-surgical pain, nerve compression due to a herniated disc, or spine arthritis or spine surgery.

Intercostal nerve RFA for postherpetic neuralgia, scar neuralgia in the chest, post-thoracotomy syndrome.

Cooled radiofrequency–

Lateral branches of sacroiliac joint RFA are done in chronic or refractory SI joint pain.

Genicular nerve RFA for chronic knee pain due to osteoarthritis knee

RFA of articular branches of hip and shoulder joint due to hip and shoulder arthritis

RFA of medial branches of lumbar facet joint due to facet joint arthropathy

What are the success rates of radiofrequency ablation?

The success of radiofrequency depends on multiple factors like the accuracy of diagnosis, anatomical variations of nerve, and techniques. Some patients have 100% pain relief. For example, the RFA of the facet joint provides 45 to 60% pain relief, while the RFA of the SI joint provides 75 to 85% pain relief. Repeated RFA may provide longer pain relief. Following the procedure, pain relief starts after 10 days, but in some cases, it may take up to two to three weeks. Even after 3 weeks of the procedure, if there is no pain relief, then the procedure might not be successful and should be repeated.

  • In which conditions can radiofrequency not be done?
  • In coagulopathy with INR>1.5, Platelet count<50000. INR should reach a normal level before the procedure
  • Pain due to cancer metastasis- As the pain is in multiple sites, radiofrequency does not relieve pain completely.
  • Active infections- After adequate control of infection with antibiotics, we can take up for the procedure
  • Uncontrolled diabetes mellitus- After adequate blood sugar control, we can take up the patients for the procedure.

Patients on anticoagulant and antiplatelet therapy- We ask the patients to stop blood thinner drugs for 7 days before the procedure and then take up for the procedure.

What are the complications of radiofrequency?

Initially discomfort due to hypo anesthesia and a neuritis-like reaction. Sometimes the pain may potentially worsen due to faulty nerve regeneration leading to allodynia.

Other rare complications such as hematoma, transitory diplopia, meningitis, Horner’s syndrome, and urinary retention may occur as written in the literature. Still, we have not observed such complications in our clinical experience.

How is the radiofrequency procedure performed?

The procedure is done in an operation theater. After establishing peripheral venous access, ECG monitoring, oxygen saturation, and non-invasive blood pressure measurements are done. First, we clean the body area to sterilize the skin to minimize the risk of infections. Next, we make the skin numb to make RFA probe placement painless. Once the probes are in place, we do a series of testing to ensure that we are getting rid of the nerve we are targeting and staying away from nerves we don’t want to damage. During the testing process, we make numb the nerve so that there is little or no discomfort during the ablation. A radiofrequency lesion generator was used for continuous and pulsed RF thermal ablation. The ablation takes 90 seconds plus or minus a few seconds for certain applications and techniques. Recovery from ablation is usually minimal, very infrequently. A 16 to 22-gauge, 5–15 cm RF cannula with a 2–10 mm active-pinned tip (with the matching electrode) is advanced to the target tissue. Following heat coagulation, 2 ml of 2% lidocaine mixed with steroid is applied through the cannula to avoid deafferentation pain. Post-procedure ice packs are used at the site of the procedure. All patients are monitored for 30-60 min for potential complications following 2 h after the procedure. Patients were discharged home on the same day.

Who is a candidate for radiofrequency ablation?

The radiofrequency ablation procedure is a treatment option for patients who have experienced successful pain relief after a diagnostic nerve block injection.

Radiofrequency ablation using x-ray guidance should not be performed in pregnant women. However, we can perform radiofrequency under USG guidance during pregnancy.

What is done before treatment?

Detailed medical and personal history and physical examination are made. Along with investigation reports and previous imaging studies thorough treatment plan is decided. The best location for the ablation is figured out beforehand. Patients should be felt free to ask any doubts regarding the procedure.

The procedure is usually performed as an outpatient special procedure suite with access to fluoroscopy. Still, the process should be performed in the sterile operating room for patients’ safety. In addition, the patient must not drive back to their home after the procedure.

Where is the procedure performed? What is done during treatment?

The patient will be asked to sign consent forms as per the Indian society of study of pain format at the procedure. The procedure may take 15-45 minutes, followed by a recovery period.

The patient lies on an OT table. Then, a local anesthetic is injected to anesthetize the targeted area. The patient experiences minimal discomfort with less pain throughout the procedure. The patient should remain awake and aware during the procedure to provide valuable information during sensory and motor stimulation to increase the procedure’s efficacy.

What happens after the radiofrequency treatment?

Most patients can walk freely immediately after the procedure. Post-procedure patients are monitored for 2 hours, patients can usually resume their daily activities.

Patients may experience pain after the procedure for up to 2 weeks. It may be due to some effects of the nerve ablation or muscle spasm also can be due to a large gauge of the thick needle. Patients should schedule a follow-up appointment post-procedure after two months to document the efficacy and address any concerns regarding future treatment plans.

What are the results of radiofrequency ablation?

Pain relief usually lasts from 9 months to more than 2 years, sometimes up to 5 to 10 years in Gasserian ganglion radiofrequency ablation. The nerve will regrow through the burned lesion of 3rd degree created by radiofrequency ablation. The nerve will regrow 6-12 months after the procedure. Radiofrequency ablation is most effective in patients with successful diagnostic nerve blocks with 70 to 80% pain relief. The process can be repeated if at all needed. There is no harm in repeating the procedure several times.

What are the risks involved in radio frequency procedures?

Radiofrequency is a relatively safe procedure with less chance of complications. The complications are a temporary increase in nerve pain, accidental damage to other nerves, neuritis /deafferentation pain, neuroma, localized numbness, infection, and/or failures with no pain relief; also pain relief is not immediate.

Take home message

  •  Radiofrequency ablation is a relatively safe and effective procedure for chronic pain conditions.
  • This is a daycare procedure, and the patient can go home on the same day.
  • Pain relief lasts from 9 months to more than 2 years.