12.    Ochiai, N.; Tasto, J. P.; Ohtori, S.; Takahashi, N.; Moriya, H.; and Amiel, D.: Nerve regeneration after radiofrequency application. Am J Sports Med, 35(11): 1940-4, 2007.

BACKGROUND: Many patients with chronic tendinosis have experienced early pain relief after application of bipolar radiofrequency treatment. It is hypothesized that the mechanism of action may be the acute degeneration and/or ablation of sensory nerve fibers.

HYPOTHESIS: After ablation or degeneration by bipolar radiofrequency, nerve fibers will have the ability to regenerate with time.

STUDY DESIGN: Controlled laboratory study.

METHODS: Eighteen Sprague-Dawley rats were used in this study. These rats were divided into 3 groups (30, 60, and 90 days after bipolar radiofrequency). These rats were treated with 2 points of bipolar radiofrequency applications to the left hindpaws with the Topaz microdebrider device. Right hindpaws were used as the contralateral control. Tissues were processed for neural class III beta-tubulin or calcitonin gene-related peptide immunohistochemistry by using the free-floating avidin biotin complex technique. The numbers of neural class III beta-tubulin-immunoreactive and calcitonin gene-related peptide-immunoreactive nerve fibers in the epidermis were counted and compared with those in the contralateral control.

RESULTS: Although the numbers of nerve fibers demonstrated by both the antibodies of neural class III beta-tubulin and calcitonin gene-related peptide were significantly decreased (P <.0001) until 60 days after bipolar radiofrequency treatment, regeneration of the epidermal nerve fibers occurred 90 days after treatment.

CONCLUSION: Bipolar radiofrequency treatment induced degeneration of sensory nerve fibers immediately after treatment, but by 90 days posttreatment, there was evidence of complete regeneration.

CLINICAL RELEVANCE: Early degeneration followed by later regeneration of nerve fibers after bipolar radiofrequency treatment may explain long-term postoperative pain relief after microtenotomy for tendinosis.