The effects of transcutaneous electrical nerve stimulation on tissue repair: A literature review

Transcutaneous electrical nerve stimulation (TENS) consists of a generic application of low-frequency, pulsed electrical currents transmitted by electrodes through the skin surface (1–6) to stimulate the peripheral nerves to produce various physiological effects (7). It is a nonpharmacological, noninvasive, inexpensive, easy to use and widely applied therapeutic modality used in clinical practice (1–4,8). The common electrical pulses emitted by TENS devices are described as monophasic rectangular, balanced asymmetrical biphasic rectangular, or symmetrical biphasic rectangular; the biphasic pulses are the most commonly used (9–12). The first TENS units were developed (6) and soon became popular after the publication of the gate control theory of pain postulated by Melzack and Wall in 1965 (13). According to this theory, the activation of large-diameter afferent fibres (A-beta fibres) activates local inhibitory mechanisms in the dorsal horn of the spinal cord causing the presynaptic inhibition of nociceptive afferent fibres (A-delta and C) (2,6,7,14,15). Since 1965, TENS has become known worldwide and is also considered to be one of the most common therapeutic resources used in clinical practice for the relief of chronic and acute pain. However, in recent decades, some authors have observed that, in addition to its analgesic effects, TENS can alter skin temperature and increase blood flow (2,7,14,15). This observation led many studies to focus on the effect of TENS on the peripheral vascular system, showing increases in blood flow (16) and, therefore, possibly facilitating tissue repair. The purpose of the present narrative review is to describe the scientific evidence regarding the effects of TENS on tissue repair with respect to wound healing, the viability of skin flaps and tendinous repair.