Pain Relief Through an Antinociceptive Effect After Radiofrequency Application

Background: Many patients with chronic tendinosis have experienced early pain relief after application of bipolar radiofrequency treatment. Pathologic nerve ingrowth or nerve irritation in the tendon has been considered as a possible cause of the pain experienced with tendinosis. Hypothesis: Bipolar radiofrequency treatment will ablate nerve fibers, resulting in pain relief. Study Design: Controlled laboratory study. Methods: Eighteen Sprague-Dawley rats were used in this study. Eight rats were treated with 2 points of bipolar radiofrequency applications applied to the hind paws with the Topaz microdebrider device, 6 sham rats had a needle applied to the hind paws, and there were 4 control rats. Tissues were processed for neural class III β-tubulin (TUJ-1) or calcitonin gene-related peptide (CGRP) immunohistochemistry by using the free-floating avidin-biotin complex technique. The numbers of TUJ1-immunoreactive and CGRP-immunoreactive nerve fibers in the epidermis were counted and compared with sham and control. Results: The number of nerve fibers demonstrated by both the antibodies of TUJ1 and CGRP were significantly decreased ( P = .0002–.002) during the first 2 weeks after bipolar radiofrequency treatment. Macroscopically, the foot pad showed 2 dimples on the surface after bipolar radiofrequency treatment. Although it still showed a scar after 7 days, after 14 days it looked no different than the untreated contralateral control foot pad and foot pad of the sham group. Conclusion: Bipolar radiofrequency treatment induced acute degeneration and/or ablation of sensory nerve fibers. Clinical Relevance: Degeneration or ablation of nerve fibers after bipolar radiofrequency treatment may explain the early postoperative pain relief after microtenotomy for tendinosis. Keywords: bipolar radiofrequency chronic tendinosis microtenotomy pain relief