Assessing The Role Of Radiofrequency Nerve Ablation For Plantar Fasciitis
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.