Radiofrequency preserves histoarchitecture and enhances collagen synthesis in experimental tendon injury

Flavia Emi Akamatsu¹, Samir Omar Saleh², Flávio Hojaij³, Carlos Augusto Real Martinez⁴, Mauro Andrade¹, Walcy Rosolia Teodoro⁵ and Alfredo Luiz Jacomo<sup>1

1</sup>Department of Surgery, Laboratory of Medical Research-Division of Human Structural Topography, Faculty of Medicine of the University of São Paulo (FMUSP), ²Surgical Clinic of Faculty of Medicine of the University of São Paulo (FMUSP), ³Department of Surgery Medicine, Laboratory of Medical Research, Faculty of Medicine of the University of São Paulo (FMUSP), ⁴Post-Graduate Program in Health Sciences of the São Francisco University Medical School (USF), Bragança Paulista-SP and ⁵Division of Rheumatology, Faculty of Medicine of the University of São Paulo (FMUSP), Brazil

Offprint requests to: Dra. Walcy Rosolia Teodoro, Faculdade de Medicina da Universidade de São Paulo, Disciplina de Reumatologia, Av. Dr. Arnaldo 455, sala 3124, CEP 01296-903, São Paulo, SP, Brasil. e-mail: matrix@lim17.fm.usp.br

Summary. We investigated the action of radiofrequency (RF) on the healing process after inducing experimental lesions of the Achilles tendon in rats. Wistar rats were surgically subjected to bilateral partial transverse sectioning of the Achilles tendon. The right tendon was treated with radiofrequency (RFT), whereas the left tendon served as a control (CT). On the third postoperative day, the rats were divided into three experimental groups consisting of ten rats each, which were treated with monopolar radiofrequency (Tonederm™) until they were sacrificed on the 7^th, 14^th or 28^th days. The histological specimens were studied for inflammatory cell content, collagen types I and III, immunostaining and morphometry. Total collagen were biochemically analyzed and to evalute fibroblast and myofibroblast proliferation by vimentin and α-actin smooth muscle immunohistochemistry methods. Statistical analysis was performed using the Student's t-test, the sign test and the Kruskal-Wallis test to compare tendons treated with radiofrequency with the non-treated tendons (α=5%; α=10%). Larger amounts of collagen I with hydroxyproline content and myofibroblast cells were clearly evident within 7 days (p<0.05). No difference was observed in the inflammatory cell content between the groups. We found better collagen arrangement with RF administration across the entire time studied. Radiofrequency administration preserves histoarchitecture and enhances collagen synthesis during the initial phases of cicatrization, suggesting that the treatment can provide improved stiffness during the most vulnerable phases of tendon healing. Clinical studies may include RF among the therapeutic tools in tendinous lesion management. Histol Histopathol 31, 515-522 (2016)

Key words: Tendon, Collagen, Healing, Radiofrequency

DOI: 10.14670/HH-11-660