Non-invasive Scrambler Therapy (ST) reduces pain by attaching electrodes to neural pathways of major nerves, transmitting information along with microcurrent to the nerves to induce a painless sensation. The ST has been widely used to reduce pain for patients with musculoskeletal pain. However, little is known about the musculoskeletal pain relief effect of the ST. Therefore, this study aims to evaluate the treatment effectiveness of the ST.

A systematic literature review was conducted based on the following search strategy and databases, and all studies published before August 2021 were included in Pubmed, Embase, and Cochrane library, Ovid Medline, Koreamed, kmbase, and Science On. The subjects were patients with intractable and musculoskeletal pain, excluding cancer pain, and intervention methods included non-invasive ST alone or in combination with physical therapy. In addition, the comparative method was not limited. The outcome variables were the degree of pain relief, total analgesic use, health-related quality of life, pressure pain threshold, pain intensity and functional interference scales, and pain sensitivity. Safety-related outcome variables were all side effects. Cochrane Risk of Bias 1.0 was used to assess the risk of bias in the literature.

Two hundred forty-one articles were retrieved using a pre-determined search strategy. Of these, 15 duplicate articles, 215 articles after reviewing the abstract and title, and nine articles after checking the full text were excluded. Two studies with randomized controlled trials (RCTs) were finally selected. When comparing ST and placebo groups for musculoskeletal pain, the pain reduction effect of ST lasted for three weeks. Moreover, patients with neuropathic pain treated with ST had a lower pain intensity for one to three months compared to the drug treatment group.

Based on this systematic review, the effectiveness of ST is yet sufficient owing to small sample size and possibility of selective report bias. More studies with well-designed RCTs are required to further assess the effectiveness of the ST.