Pulsed radiofrequency in peripheral posttraumatic neuropathic pain: A double blind sham controlled randomized clinical trial.

Background and purpose Pulsed radiofrequency (PRF) is widely used for the treatment of chronic pain, although its mechanism of action is not known. The evidence of efficacy of PRF for neuropathic pain (NP) conditions is limited. A double-blind, randomized, sham-controlled parallel study was conducted to evaluate the efficacy and safety of PRF in the treatment of peripheral posttraumatic NP. Methods Forty-five patients with peripheral posttraumatic NP in their upper or lower limb were randomly assigned to receive PRF or sham treatment to the injured peripheral nerve (s) causing peripheral posttraumatic NP. Only patients whose pain intensity was at least 5 on numerical rating scale (NRS) 0-10 and who had suffered from their NP for at least 6 months were included. All patients had dynamic mechanical allodynia or pinprick hyperalgesia in their painful area. They had achieved temporary pain relief of at least 50% with a local nerve block performed at a previous visit. The primary efficacy variable was the difference in 3-day mean pain intensity score from the baseline to 3 months. Other variables included response defined as ≥30% reduction in mean pain intensity at 3 months compared to baseline, Neuropathic Pain Scale (NPS) results, health related quality of life (SF-36) and adverse effects. The skin was anesthetized with 1% lidocaine. A radiofrequency needle was introduced through the skin, and then guided to a SMK cannula (52, 100 or 144mm depending on the target nerve) with 4 or 5mm active tip (SMK-C5-4, SMK-C10-5, SMK-C15-5, Radionics®, Burlington, MA, USA). The nerve was located accurately by stimulating at 50 Hz (threshold <0.5 V). Sham treatment or PRF was applied for 120s 1-4 times at each treatment point (Radionics®, Burlington, MA, USA). The total treatment time was up to 8 min. Both patients and clinicians were blinded during the whole treatment and follow-up period. Results Forty-three patients were included in the analyses. There was no statistically significant difference between PRF and sham treatment for the primary outcome efficacy variable. Seven patients (3 in PRF group and 4 in sham treatment group) achieved ≥30% pain relief (difference between groups was not significant). There was no statistically significant difference in the NPS or any dimension of SF-36 between the treatments. Eighteen patients reported adverse effects. They were mild and did not necessitate any treatment. Transient pain was reported by 17 patients, local irritation by 5 patients and local inflammation by 1 patient. There was no significant difference between the groups in the presence of adverse effects. Conclusions PRF was well tolerated, but this study failed to show efficacy of PRF over sham treatment for peripheral posttraumatic NP. Implications Based on our results, we do not recommend PRF for peripheral posttraumatic NP. More research of the possible use of PRF for various pain conditions is needed to determine its role in the management of prolonged pains.