Tendon injuries are a common musculoskeletal injury and can be difficult to treat [1]. This condition affects more than 102.5 million adults each year [1]. Unfortunately, many common treatments cannot restore patients to their pre-injury state [1]. When dissatisfactory treatments often fall short of full healing, patients have a higher chance of exhibiting proteoglycan accumulation, scar tissue formation, calcification, and, ultimately, impaired biomechanical regulation and function [1]. There is a pronounced need for modes of treatment that differ from typical surgical interventions [1]. One such potential treatment for tendon injuries is electrical therapy.
Over the last few years, several studies have lauded the multiple benefits of electrical techniques [1]. While there is significant variation among these techniques, electrical therapy can lead to long-term tendon repair, unlike many other forms of treatment [2]. Potential benefits of electrotherapy include improved collagen synthesis, cell migration mediation, and, ultimately, successful wound healing [1].
Multiple experiments have observed the wound healing capabilities of electrical therapy. Casagrande et al. organized a study in which 42 rats with Achilles tendon lesions were divided into two groups and given either electrical stimulation or no treatment at all [3]. Achilles tendon lesion is the most frequently recorded form of tendon injury, accounting for up to 50% of all tendon injuries [3]. The researchers found that both maximum tension (which measures the tendon’s capacity to support load) and energy absorption were significantly higher at two and six weeks among the experimental group [3]. They concluded that electrical stimulation promotes greater resistance in injured tensions [3].
Electrical forms of treatment can also have beneficial effects on gene expression [4]. In an experiment conducted by Bortolazzo et al., researchers found that microcurrent therapy stimulated several genes, such as TNC, CTGF, FN, FMDO, and COL3A1 [4]. These genes contribute to the healing process: for instance, TNC is crucial for repairing tissue, and FMDO affects the cell signaling necessary for tendon repair [4]. In the end, the rats that received microcurrent therapy exhibited greater biomechanical resistance and improved collagen fiber reorganization than the rats that had just been treated with adipose-derived stem cells [4].
Some studies also indicate that electrical therapy is superior to other forms of treatment for tendon injury as well [5]. In a study focusing on injury to the left Achilles tendon, the researchers divided 28 rats into four equally sized groups, each receiving a different course of treatment: electrical stimulation, ultrasound, laser, or no therapy at all [5]. The electrical stimulation group reported the highest increase in the number of capillaries and fibroblasts among the four groups [5]. Seeing as both measures indicate successful tendon tissue healing, the researchers hypothesized that electrical therapy posed the best course of treatment for a tendon injury in that context [5].
Of course, the use of electrical therapy in humans requires more research to ensure safety and verify its benefits. Researchers have already defined some guidelines for medical practitioners to follow when administering this treatment to patients, such as keeping currents below 50 µA to prevent protein denaturation [4]. Another recommendation advises physicians to place electrodes perpendicularly to the largest tension axis of the tendon to promote collagen and cell realignment [4]. Despite these helpful instructions, more randomized controlled studies must occur to verify the ultimate benefits of, and best guidelines for, successful electrical therapy in tendon injury healing [2, 6].
References
[1] M. A. Fernandez-Yague et al., “A Self-Powered Piezo-Bioelectric Device Regulates Tendon Repair-Associated Signaling Pathways through Modulation of Mechanosensitive Ion Channels,” Advanced Materials Early View, p. 1-18, August 2021. [Online]. Available: https://doi.org/10.1002/adma.202008788.
[2] S. B. Rajendran et al., “Electrical Stimulation to Enhance Wound Healing,” Journal of Functional Biomaterials, vol. 12, no. 2, p. 1-17, June 2021. [Online]. Available: https://doi.org/10.3390/jfb12020040.
[3] S. M. Casagrande et al., “Tensiometric evaluation of the effect of low frequency electric stimulation on healing Achilles tendons in rats,” SciFlo Brazil, vol. 35, no. 11, p. 1-10, December 2020. [Online]. Available: https://doi.org/10.1590/ACB351103.
[4] F. O. Bortolazzo et al., “Microcurrent and adipose-derived stem cells modulate genes expression involved in the structural recovery of transected tendon of rats,” The FASEB Journal, vol. 34, no. 8, p. 10011-10026, June 2020. [Online]. Available: https://doi.org/10.1096/fj.201902942RR.
[5] R. C. Araújo et al., “Effects of laser, ultrasound and electrical stimulation on the repair of achilles tendon injuries in rats: a comparative study,” Journal of Morphological Sciences, vol. 24, no. 3, p. 187-191, May 2007..
[6] Y. Hsu et al., “Healing of Achilles tendon partial tear following focused shockwave: a case report and literature review,” Journal of Pain Resolution, vol. 10, p. 1201-1206, May 2019. [Online]. Available: https://doi.org/10.2147/JPR.S132951.