Can transcutaneous electrical nerve stimulation improve achilles tendon healing in rats?

Roberta A C Folha,Lydia M Ferreira,Érika P Rampazo,Carlos E Pinfildi,Raphael N Pereira,Richard E Liebano

doi:10.1590/bjpt-rbf.2014.0107

Abstract

BACKGROUND: Tendon injury is one of the most frequent injuries in sports activities. TENS is a physical agent used in the treatment of pain but its influence on the tendon's healing process is unclear. OBJECTIVE: To evaluate the influence of TENS on the healing of partial rupture of the Achilles tendon in rats. METHOD: Sixty Wistar rats were submitted to a partial rupture of the Achilles tendon by direct trauma and randomized into six groups (TENS or Sham stimulation) and the time of evaluation (7, 14, and 21 days post-injury). Burst TENS was applied for 30 minutes, 6 days, 100 Hz frequency, 2 Hz burst frequency, 200 µs pulse duration, and 300 ms pulse train duration. Microscopic analyses were performed to quantify the blood vessels and mast cells, birefringence to quantify collagen fiber alignment, and immunohistochemistry to quantify types I and III collagen fibers. RESULTS: A significant interaction was observed for collagen type I (p=0.020) where the TENS group presented lower percentage in 14 days after the lesion (p=0.33). The main group effect showed that the TENS group presented worse collagen fiber alignment (p=0.001) and lower percentage of collagen III (p=0.001) and the main time effect (p=0.001) showed decreased percentage of collagen III at 7 days (p=0.001) and 14 days (p=0.001) after lesion when compared to 21 days. CONCLUSIONS: Burst TENS inhibited collagen I and III production and impaired its alignment during healing of partial rupture of the Achilles tendon in rats.

Highlights

Partial rupture of the Achilles tendon and tendinopathologies are frequent lesions and their incidence has grown due to the increase in sports practice by the general population[1]
After the Tukey Post hoc test was possible observe that the transcutaneous electrical nerve stimulation (TENS) group presented lower percentage of collagen type I 14 days after the lesion (p=0.033, Figure 3)
The main effect of group showed that the TENS group presented worse collagen fiber alignment (p=0.001) and lower percentage of collagen III (p=0.001) than the Sham group

Summary

Introduction

Partial rupture of the Achilles tendon and tendinopathologies are frequent lesions and their incidence has grown due to the increase in sports practice by the general population[1]. Experimental studies have shown beneficial effects on vascularization, collagen fiber alignment, collagen type present in the tissue, and tensile force of the tendon after the application of electrophysical agents during the tendon healing process, such as low level laser therapy[4], ultrasound[5,6], electromagnetic fields[7], and electrical stimulation[8] Among these resources, transcutaneous electrical nerve stimulation (TENS) can be highlighted as a simple, non-invasive, low-cost method that, in addition to modelling pain perception, has effects on local blood flow[9,10], wound healing[11], and reduction of the necrotic area of ischemic skin flaps[12]. According to Sluka and Walsh[9], only the low-frequency and burst modalities are capable of reaching the A-delta

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Conclusion