Assessing The Role Of Radiofrequency Nerve Ablation For Plantar Fasciitis

In recent years, radiofrequency nerve ablation has emerged as a potential modality for plantar fasciitis. Accordingly, this author details his experience in using radiofrequency nerve ablation, provides a closer look at the literature and compares the modality to other treatments for heel pain.

Radiofrequency nerve ablation uses radiofrequency energy to create heat in a very small area in order to disrupt the myelin sheath on the surface of sensory nerves. The application of heat at 80º to 90ºC for 90 seconds results in gaps in the sheath, thereby stopping conduction of the nerve. The literature has previously described the response of nerve tissue to radiofrequency nerve ablation.1

   Using radiofrequency nerve ablation, one can easily control pain associated with plantar fasciitis by eliminating the sensory perception of inflammation in the heel. In fact, this technology is effective at reducing or eliminating pain from a variety of etiologies associated with heel pain, including nerve entrapments, scars from open plantar fascial releases, calcaneal bursitis and, of course, plantar fasciitis.

   As with all unfamiliar technologies, there is a certain level of understanding needed in order to demystify the treatment process. In reality, radiofrequency technology has been available for quite some time. Microwave ovens are based on this technology on a much larger scale and many electrocautery devices used in the operating room use radiofrequency to generate heat.

   Radiofrequency nerve ablation differs from these much simpler devices in the ability to regulate the heat administered. In addition, the device discussed here uses a simple nerve stimulator to localize the placement of the electrode adjacent to the target nerve and differentiate sensory from motor nerves. Accordingly, clinicians can be certain they are only treating the targeted nerve.

   Radiofrequency nerve ablation technology was first described in 1968 and has been in widespread use for pain management since the 1980s.1,2 Physicians specializing in chronic pain management have been using this technology successfully to disrupt conduction to nerves as they exit the spine. For example, in cases in which sensory nerves are being pinched by compressed vertebrae, nerve ablation can halt chronic pain. Similarly, ablation of the nerve can control hyperstimulated cardiac tissue.3 This can result in a more regular heartbeat by eliminating ectopic stimulation.

Targeting Nerves In The Plantar Fascia

When managing chronic pain, the clinician must identify the associated sensory nerve. Then the clinician must place the radiofrequency nerve ablation probe close enough to the nerve to create sufficient thermal damage to stop conduction. Current devices such as the NeuroTherm NT250 (NeuroTherm) provide the clinician with a mechanism to assess the position of the probe relative to the nerve by measuring impedance. Impedance is the resistance of the tissues between the tip of the probe and the target nerve. The greater the distance between the nerve and the probe, the greater the impedance will be. The ability to measure impedance between the probe and the nerve represents a significant advance in the treatment of plantar fasciitis with radiofrequency nerve ablation and allows the clinician to move the procedure from the operating room to the clinic.

   Although plantar fasciitis is widely believed to result from inflammation of the medial and central portions of the plantar fascia at the origin from the calcaneus, researchers have suggested other mechanisms. Authors have cited nerve entrapments, stress fractures, calcaneal bursitis and a variety of other causes for heel pain.4 In fact, Lemont and co-authors have proposed the term plantar fasciosis to describe the cluster of problems that can cause heel pain.4

   Although the etiology is potentially multifactorial, the nerve that transmits the pain remains consistent for most types of heel pain. The posterior and anterior branches of the inferior calcaneal nerve provide sensory innervation to the area where the plantar fascia originates from the calcaneus. The medial calcaneal nerve provides sensory innervation to the more medial aspects of the heel as well as the calcaneal bursa regions. Ablation of these nerves can reduce the deep heel pain associated with each of these areas.

A Step-By-Step Guide To Performing The Procedure

In order to perform the ablation procedure, one must carefully localize the target nerves. This step can be quite simple if you insert the electrode with the same orientation that you would use for giving a steroid injection for plantar fasciitis. Prior to administering the injection, examine the patient to determine the areas of greatest tenderness. The more carefully one can identify the areas of greatest pain, the better the chance of nerve localization.

   Insert the electrode so the tip is at the area of greatest discomfort. After positioning the electrode, perform high frequency sensory stimulation. The patient should feel a sensation resembling a vibration when the probe is close to the nerve. With the NT250 device, one can measure impedance, which should be less than 0.6 volts when the nerve is close to the probe.

   After sensory stimulation, perform low frequency motor stimulation. After determining that the probe is near the nerve and that the nerve is a sensory nerve and not a motor nerve, the ablation process can start. Landsman has offered a detailed description of the actual technique.5

   The actual ablation process is quite simple and involves the delivery of approximately 0.5 cc of local anesthetic through the probe cannula, just prior to ablation, normally at 90ºC for 90 seconds. The tip of the probe creates a sphere of heat sufficient to disrupt the myelin sheath, which is 5 mm in diameter.

   Devices such as the NeuroTherm NT250, which are designed to do this procedure, have built-in timers and are temperature controlled so the 90ºC temperature is precisely regulated. As a result, the surrounding tissues will not be burned. In most cases, one would perform the ablation procedure three times in order to treat the anterior and posterior branches of the inferior calcaneal nerve and the medial branch of the calcaneal nerve.

   Typically, the patient will report at least 50 percent improvement in the first two weeks and will reach maximum improvement between four and six weeks after treatment. Patients who do not fully respond to treatment during the first four to six weeks should consider a second treatment in order to get maximum relief.

What The Research Reveals About The Efficacy Of Radiofrequency Nerve Ablation

A review of the literature reveals several studies that support the use of radiofrequency nerve ablation for the treatment of plantar fasciosis. Liden and colleagues recently studied 31 feet treated for plantar fasciitis.6 The results demonstrated an average decrease in pain from 8.12 out of 10 to 1.46 out of 10 one month after treatment. Similar results occurred six months after treatment. A study by Sollitto and co-workers involved the treatment of 39 feet with radiofrequency nerve ablation and they found a 92 percent success rate.7 Their technique was slightly different in that they used a plantar rather than an anterior medial approach to the nerve.

   Cozzarelli and colleagues conducted the largest study to date involving the treatment of plantar fasciitis with radiofrequency nerve ablation.8 The study of 82 patients with up to 12 years of follow-up showed an 89 percent success rate. The same article reports details of the authors’ technique and involves a more detailed explanation of their method for nerve localization. According to their description, these investigators will attempt to pinpoint each area of pain individually around the heel region and then perform individual ablations. Although this approach may be more laborious, it may increase the chances of success since the treatment targets a greater area.

   More recently, my group has submitted a study to the Journal of the American Podiatric Medical Association and the study involves a prospective evaluation of patients who were randomly assigned to active or placebo treatment. Those who did not respond received the opportunity to cross over. We found that those who received active treatment demonstrated dramatic improvement within the first month while those who received placebo showed no statistically significant improvement. This manuscript is under peer review at this time.

How Does Radiofrequency Nerve Ablation Stack Up To The Alternatives?

Many alternatives exist for the treatment of common plantar fasciitis. Treatments such as corticosteroid injections, extracorporeal shockwave therapy (ESWT), partial surgical release of the plantar fascia, physical therapy, arch supports and behavior modifications are all known to provide some level of relief.

   However, there are associated risks with many of these treatments. Corticosteroid injections may lead to irreversible soft tissue atrophy.9 Partial release of the plantar fascia can cause collapse of the arch, cuboid crush symptoms and painful scar formation.10 Shockwave can be quite expensive and research has shown ESWT to produce a significant reduction of symptoms in approximately 50 percent of the cases following a single treatment.11

   The risks associated with radiofrequency nerve ablation are comparatively low and the clinical outcomes are generally much higher. Although radiofrequency nerve ablation does give relief to those afflicted with inflammation at the origin of the plantar fascia, it is also beneficial for those with scar related heel pain, calcaneal bursitis, nerve entrapments and even fat pad atrophy. Furthermore, radiofrequency nerve ablation does not diminish the strength of the plantar fascia in any way and therefore will not result in medial arch collapse or cuboid crush conditions.

   The types of complications associated with radiofrequency nerve ablation center around the types of problems normally associated with a standard injection. These problems may include a hematoma at the injection site. Also in some cases, one may have to repeat the procedure if the probe was not close enough to the affected nerve at the time of ablation.

Why Radiofrequency Nerve Ablation Has Become A ‘Treatment Of Choice’ For The Author

Due to the safety profile, proven efficacy and the ease of the procedure, radiofrequency nerve ablation is becoming my treatment of choice rather than a go-to treatment when all else has failed. In over 80 percent of cases, I have found that patients get almost complete relief within one month following a single treatment that normally occurs in the office.

   I have found that the safety profile is outstanding with no worsening of the condition and no significant adverse events. The most common complication was bruising at the injection site.

   I have tried to perform radiofrequency nerve ablation with other painful conditions of the foot as well. One area in which I have had great success is with heel pain that is associated with scar tissue and nerve entrapment. This occasionally occurs following a percutaneous or open plantar fascia release where the incision site becomes hypertrophic. In combination with a steroid infiltration, the success rate becomes even higher for this procedure.

   Another application for radiofrequency nerve ablation is with Morton’s neuroma. My success rate with this condition has been good but this frequently requires more than one treatment. I have attributed this to the fact that the nerves are more difficult to localize due to their variable position within the interspace and the need to ablate both intermetatarsal nerves sufficiently to stop the pain.

   In many cases, I am able to partially ablate the nerves on the first treatment. Although this may reduce the pain, it may not eliminate it. However, subsequent ablation becomes easier as the area of pain is smaller. Since the area is smaller, localization of the nerve becomes easier.

In Summary

Radiofrequency nerve ablation has become an important part of my practice. I have found it to be a highly effective way to dramatically reduce pain associated with a variety of types of heel pain, particularly plantar fasciitis.

   Furthermore, I now consider it in the earliest phases of treatment, even before steroid injections, in order to avoid fat pad atrophy, spikes in blood glucose and other steroid-related complications. Typically, one can perform the procedure in 10 minutes or less.

   Dr. Landsman is the Chief of the Division of Podiatric Surgery at Cambridge Health Alliance in Cambridge, Mass. He is an Assistant Professor at the California School of Podiatric Medicine at Samuel Merritt University. Dr. Landsman is a Fellow of the American College of Foot and Ankle Surgeons.

References

1. Letcher FS, Goldring S. The effect of radiofrequency current and heat on peripheral nerve action potential in the cat. J Neurosurg. 1968; 29(1):42-47.
2. Smith HP, McWhorter JM, Challa VR. Radiofrequency neurolysis in a clinical model, neuropathological correlation. J Neurosurg. 1981; 55(2):246-253.
3. Leather RA, Leitch JW, Klein GJ, Guiraudon GM, Yee R, Kim YH. Radiofrequency catheter ablation of accessory pathways: a learning experience. Am J Cardiol. 1991; 68(17):1651-5.
4. Lemont H, Ammirati KM, Usen N. Plantar fasciitis: a degenerative process (fasciosis) without inflammation. J Am Podiatr Med Assoc. 2003; 93(3):234-7.
5. Landsman A. Radiofrequency nerve ablation for the treatment of heel pain. Tech Foot Ankle Surg. 2011; 10(2):76-81.
6. Liden B, Simmons M, Landsman A. A Retrospective analysis of 22 patients treated with percutaneous radiofrequency nerve ablation for prolonged moderate to severe heel pain associated with plantar fasciitis. J Foot Ankle Surg. 2009; 48(6):642–647.
7. Sollitto RJ, Plotkin EL, Klein PG, Mullin P. Early clinical results of the use of radiofrequency lesioning in the treatment of plantar fasciitis. J Foot Ankle Surg. 1997; 36(3):215-9.
8. Cozzarelli J, Sollitto RJ, Thapar J, Caponigro J. A 12-year long-term retrospective analysis of the use of radiofrequency nerve ablation for the treatment of neurogenic heel pain. Foot Ankle Spec. 2010; 3(6):338-46.
9. Brinks A, Koes BW, Volkers AC, Verhaar JA, Bierma-Zeinstra SM. Adverse effects of extra-articular corticosteroid injections: a systematic review. BMC Musculoskelet Disord. 2010; 11:206.
10. Tweed JL, Barnes MR, Allen MJ, Campbell JA. Biomechanical consequences of total plantar fasciotomy: a review of the literature. J Am Podiatr Med Assoc. 2009; 99(5):422-30.
11. Rompe JD, Furia J, Weil L, Maffulli N. Shock wave therapy for chronic plantar fasciopathy. Br Med Bull. 2007; 81- 82:183–208.

   For further reading, see “Study Assesses Long-Term Results Of Radiofrequency Nerve Ablation” in the November 2010 issue of Podiatry Today, “Top Innovations In Podiatric Care” in the August 2009 issue, or the blog “Overcoming Podiatric Dogma On Neuromas And Peripheral Nerve Surgery” at https://bit.ly/c9P8Wt .