Collagen Changes and Realignment Induced by Low-Level Laser Therapy and Low-Intensity Ultrasound in the Calcaneal Tendon

Background and Objective: The treatment of calcaneal tendon injuries requires long-term rehabilitation Ultrasound (US) and low-level laser therapy (LLLT) are the most used and studied physical agents in the treatment of tendon injuries, however, only a few studies examined the effects of the combination of US and LLLT. Therefore, the purpose of this study was to investigate which treatment (the exclusive or combined use of US and LLLT) most effectively contribute to tendon healing. Study Design/Materials and Methods: This was a controlled laboratory study with 50 rats whose Achilles tendon was injured by direct trauma. The rats were randomly divided into five groups and treated for 5 consecutive days, as follows: group 1 (control) received no treatment; group 2 was treated with US alone, group 3 was treated with LLLT alone, group 4 was treated first with US followed by LLLT, and group 5 was treated first with LLLT followed by US On the sixth post-injury day, the tendons were removed and examined by polarized light microscopy. The organization of collagen fibers was assessed by birefringence measurements Picrosirius-stained sections were examined for the presence of types I and Ill collagen. Results: There was a significantly higher organization of collagen fibers in group 2 (US) than in the control group (P=0.03). The amount of type I collagen found in groups 2 (US), 3 (LLLT), and 5 (LLLT+US) was significantly higher than that in the control group (P <= 0.01), but no significant differences were found between treatment groups. There were no differences in the amount of type III collagen between groups. Conclusion: Ultrasound, LLLT, and the combined use of LLLT and US resulted in greater synthesis of type I collagen; US was also effective in increasing collagen organization in the early stages of the healing process Lasers Surg. Med. 42 559-565, 2010 (C) 2010 Wiley-Liss, Inc.