The Clinical Application of Pulsed Radiofrequency Induces Inflammatory Pain via MAPKs Activation: A Novel Hint for Pulsed Radiofrequency Treatment

Pulsed radiofrequency (PRF) works by delivering short bursts of radiofrequency to a target nerve, thereby affecting nerve signal transduction to reduce pain. Although preliminary clinical investigations have shown that PRF treatment can be used safely as an alternative interventional treatment in patients with refractory pain conditions, unexpected damage to a normal nerve/ganglion is still one of the possible complications of using the PRF strategy. Noxious pain may also be triggered if PRF treatment accidentally damages an intact nerve. However, few studies in the literature have described the intracellular modifications that occur in neuronal cells after PRF stimulation. Therefore, in this study, we evaluated the effects of PRF on unimpaired nerve function and investigated the potential mechanisms of PRF-induced pain. Wistar rats were stimulated with 30–60 V of PRF for 6 min, and mechanical allodynia, cold hypersensitivity, cytokine and matrix metalloproteinase (MMP) production, and mitogen-activated protein kinase activity (p38 MAPK, ERK1/2, JNK/SAPK) were analyzed. The results indicated that PRF stimulation induced a significant algesic effect and nociceptive response. In addition, the protein array and Western blotting analyses showed that the clinical application of 60 V of PRF can induce the activation of MAPKs and the production of inflammatory cytokines and MMPs in the lumbar dorsal horn, which is necessary for nerve inflammation, and it can be suppressed by MAPK antagonist treatment. These results indicate that PRF stimulation may induce inflammation of the intact nerve, which in turn causes inflammatory pain. This conclusion can also serve as a reminder for PRF treatment of refractory pain.

A Double-Blind, Placebo-Controlled Study of Ultrasound-Guided Pulsed Radiofrequency Treatment of the Saphenous Nerve for Refractory Osteoarthritis-Associated Knee Pain

BACKGROUND: While the efficacy of pulsed radiofrequency (PRF) for shoulder pain has been demonstrated, its efficacy on the saphenous nerves for knee osteoarthritis (OA)-associated pain has only been reported in observational studies. OBJECTIVES: The aim of this study was to compare saphenous nerve PRF to placebo for knee OA-associated pain. STUDY DESIGN: Patients, practitioners, and outcome assessor-blinded randomized placebo-controlled trial. SETTING: Pain management clinics at 2 hospitals in Japan. METHODS: Patients were randomly allocated to the PRF (n = 37) or placebo group (n = 33). Patients aged 40-85 years with refractory anteromedial knee pain. PRF in the saphenous nerve under ultrasound guidance. The placebo group underwent the same procedure, but with motor stimulation. The primary endpoint was the average pain intensity measured using the visual analog scale (VAS) at the 12-week post-treatment visit; secondary outcomes included the average VAS at 1 and 4 weeks, and pain intensities at rest, in flexion, at standing, and at walking. Other secondary outcomes were knee pain, symptoms, activities of daily living, knee-related quality of life, mobility, range of motion, and adverse events. RESULTS: In the PRF group, the mean VAS score was 52.41 ± 26.17 at 12 weeks, while in the sham group, the mean VAS score was 63.06 ± 27.12 (P < 0.05). There were no significant differences between the groups in any of the secondary outcomes. LIMITATIONS: Patients with comorbidities were excluded from this study. The follow-up time was limited to 12 weeks. CONCLUSIONS: Ultrasound-guided saphenous nerve PRF proved to be effective for at least 12 weeks in patients with knee OA and showed no adverse events. KEY WORDS: Pulsed radiofrequency treatment, knee osteoarthritis, saphenous nerve, ultrasound-guided, randomized controlled trial, pain, pain management, placebo

Comparison between ultrasound-guided monopolar and bipolar pulsed radiofrequency treatment for refractory chronic cervical radicular pain: A randomized trial

BACKGROUND: Many patients complain of chronic cervical radicular pain, and pulsed radiofrequency (PRF) is known to have a positive effect for alleviating neuropathic pain. OBJECTIVES: In the present study, we used ultrasound (US) guidance and compared the effects of monopolar PRF with those of bipolar PRF in patients with chronic cervical radicular pain refractory to repeated transforaminal epidural steroid injections. METHODS: Sixty-six patients with chronic cervical radicular pain were included in this study. Patients were randomly assigned to one of the two groups: monopolar or bipolar PRF group (n= 33 per group). Pain intensity was evaluated using a numeric rating scale (NRS) at pretreatment, and at 1 and 3 months after the treatment. Target stimulation site was the extraforaminal nerve root. RESULTS: Compared to the pretreatment NRS scores, patients in both groups showed a significant decrease in NRS scores at 1 and 3 months after the treatment. Reductions in the NRS scores over time were significantly larger in the bipolar PRF group. Three months after the treatment, 18 patients (54.5%) in the monopolar PRF group and 27 (81.8%) in the bipolar PRF group reported successful pain relief (pain relief of ⩾50%). CONCLUSIONS: US-guided PRF can be an effective interventional technique for the management of chronic refractory cervical radiculopathy. Moreover, bipolar PRF has better treatment outcome than monopolar PRF.

Dorsal Root Ganglion Pulsed Radiofrequency Treatment for Chronic Radicular Pain: A Narrative Mini Review

Chronic cervical and lumbar radicular pain represents a very widespread neuropathic pain in the population with serious repercussions on the individual and social health. To date, we do not have sufficient evidence available to allow us to make recommendations on the optimal therapy, despite the fact that various ways of treating root pain have been described over the years. Currently, conservative treatment of radicular pain relies on combined therapeutic, pharmacological and physiotherapeutic management. Interventional therapeutic procedures are reserved for those patients with root pain refractory to conservative therapies. Radio frequency (RF) can provide a good treatment option with Pulsed Radio frequency (PRF) modality. We evaluate clinical and radiologic effects of the therapeutic outcome of pulsed radiofrequency (PRF) treatment adjacent to the dorsal root ganglion (DRG) for patients with chronic intractable lumbar and cervical radicular pain in this narrative minireview, describing mechanism of action, biological effects and evidence for clinical effects and safety in recently published studies.