Electroacupuncture for the treatment of frozen shoulder: A systematic review and meta-analysis

Electroacupuncture represents one of the most promising therapeutic approaches for the treatment of frozen shoulder, also known as adhesive capsulitis. This condition affects between 2% and 5% of the population, primarily individuals between 40 and 65 years of age, causing intense shoulder pain and significant movement limitation. Symptoms can appear suddenly and recovery is slow, potentially taking 1 to 4 years for complete healing. During this lengthy period, patients experience considerable impairment of quality of life, including sleep disturbances and restrictions in daily activities.

Although conventional treatments exist, such as intra-articular corticosteroids—which provide temporary pain relief and improvement in range of motion—their effects are limited in duration. Electroacupuncture emerges as an attractive therapeutic alternative, combining the traditional benefits of acupuncture with low-intensity electrical stimulation delivered through the needles. This method potentiates analgesic effects by activating complex neuroimmune and neuroinflammatory mechanisms, including the release of bioactive substances such as opioids, serotonin, and neurotransmitters that modulate pain perception.

To scientifically evaluate the efficacy and safety of electroacupuncture in the treatment of frozen shoulder, researchers conducted a comprehensive systematic review and meta-analysis. The study followed rigorous medical research protocols, searching 11 electronic databases from inception through June 2022. International databases such as EMBASE, MEDLINE, and the Cochrane Library were included, along with Chinese and Korean databases, ensuring a broad search of the available scientific literature. Two independent researchers performed study selection, data extraction, and methodological quality assessment, following predefined rigorous criteria.

The analysis included only randomized controlled trials that compared electroacupuncture with manual acupuncture or conventional treatments in patients with confirmed diagnosis of frozen shoulder. Researchers primarily evaluated pain intensity, measured through validated scales, and secondarily evaluated shoulder function, treatment response rate, and possible adverse effects. To ensure the reliability of the results, they used appropriate statistical tools and assessed the risk of bias of the included studies.

The results revealed promising evidence regarding the benefits of electroacupuncture. Thirteen studies involving 936 patients were included in the final analysis. When compared with traditional manual acupuncture, electroacupuncture demonstrated significant superiority across multiple aspects. For pain reduction, patients treated with electroacupuncture showed substantially greater improvement, with a mean difference of 1.11 points on the pain scale.

Shoulder function also showed greater improvement with electroacupuncture, as did the overall response rate, which was 16% higher compared with manual acupuncture.

When used as adjunctive therapy alongside conventional treatments, electroacupuncture also demonstrated additional benefits. Patients who received electroacupuncture combined with conventional medicine experienced significantly greater pain reduction than those treated with conventional medicine alone. These results suggest that electroacupuncture may serve both as an effective alternative and as a valuable complement to existing treatments. Importantly, no significant adverse effects were reported in the analyzed studies, indicating a favorable safety profile.

For patients with frozen shoulder, these findings represent an encouraging perspective. Electroacupuncture offers a non-pharmacologic therapeutic option that can provide effective pain relief and functional improvement without the risks associated with medications or invasive procedures. For health care professionals, the results provide scientific evidence supporting the incorporation of electroacupuncture into treatment protocols, either as primary or complementary therapy. The technique appears particularly valuable considering the chronic and debilitating nature of frozen shoulder, offering patients an alternative with a favorable benefit-risk ratio.

However, several important limitations must be considered when interpreting these results. The methodological quality of the included studies showed significant deficiencies, including inadequate randomization methods and lack of appropriate blinding, which may have influenced the outcomes. All studies were conducted in China, limiting the generalizability of the findings to other populations. The relatively small sample size and high heterogeneity across studies also reduce confidence in the conclusions.

Furthermore, treatment protocols varied considerably across studies, making it difficult to determine the optimal therapeutic regimen.

Considering these limitations, although the results are promising and suggest that electroacupuncture may emerge as a potent intervention against frozen shoulder, additional studies of higher methodological quality are needed to definitively confirm its efficacy. Future clinical trials should employ more rigorous randomization methods, larger samples, and standardized treatment protocols, and should include geographically more diverse populations to strengthen the available scientific evidence.