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Database of Abstracts of Reviews of Effects (DARE): Quality-assessed Reviews [Internet]. York (UK): Centre for Reviews and Dissemination (UK); 1995-.

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Database of Abstracts of Reviews of Effects (DARE): Quality-assessed Reviews [Internet].

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Efficacy of electrical nerve stimulation for chronic musculoskeletal pain: a meta-analysis of randomized controlled trials

and .

Review published: .

CRD summary

The authors concluded that, compared with placebo, electrical nerve stimulation is an effective treatment for chronic musculoskeletal pain. The evidence presented appears to support the authors' conclusion, but the studies were conducted in different populations and the amount of benefit varied amongst the studies.

Authors' objectives

To assess the efficacy of electrical nerve stimulation (ENS) compared with placebo for the treatment of chronic pain with multiple aetiologies.


The Cochrane Library, EMBASE and the National Library of Medicine were searched from January 1976 to November 2006. Only studies published in the English language were eligible for inclusion.

Study selection

Study designs of evaluations included in the review

Randomised controlled trials (RCTs) were eligible for inclusion in the review. Both parallel and crossover design studies were included in the review.

Specific interventions included in the review

Studies that compared any form of ENS with placebo for any duration were eligible for inclusion. Studies could combine ENS with other treatments if the same concomitant treatment was given to all treatment groups or the patient controlled the amount of the concomitant treatment. Studies that compared ENS with a potentially active control treatment or a control of unknown effectiveness were excluded. The included studies used the following forms of ENS: high-, low- and variable-frequency transcutaneous nerve stimulation (TENS), acupuncture-like TENS, and high-, low- and variable-frequency percutaneous electrical nerve stimulation (PENS).

Participants included in the review

Studies of individuals with chronic musculoskeletal pain at any site, of at least 3 months' duration, were eligible for inclusion in the review.

Outcomes assessed in the review

Studies that measured pain at rest were eligible for inclusion. Eligible studies were required to assess pain either at baseline and following treatment or as a single measure of degree of pain relief following treatment. All scales assessing pain were eligible for inclusion. Studies assessing only load bearing, joint mobility or other indirect aspects of pain relief were excluded from the review.

How were decisions on the relevance of primary studies made?

Two reviewers independently assessed studies for inclusion in the review

Assessment of study quality

Two reviewers independently assessed the validity of the studies using a modified form of the Jadad scale. The criteria used were randomisation, allocation concealment, blinding and use of intention-to-treat analysis. The studies were awarded a score of between 0 and 5. Any disagreements were resolved through discussion.

Data extraction

The authors did not state how the data were extracted for the review, or how many reviewers performed the data extraction.

Baseline measurements and final post-treatment measurements of means were extracted for outcomes related to pain. Where necessary, data were extracted from graphical representations or calculated from alternative statistics. Data expressed as a categorical variable was converted to a mean. Pre-post differences and within-group standard deviations were calculated and the standardised mean difference used as an effect size.

Methods of synthesis

How were the studies combined?

The studies were combined in a random-effects meta-analysis. Studies that compared more than one ENS modality with a sham control group were included in the meta-analysis as multiple studies.

How were differences between studies investigated?

Statistical heterogeneity between the studies was assessed using the Q statistic. Sensitivity analyses of the impact of including non-independent studies (by including only one comparison from each study), and the impact of excluding studies with a Jadad score lower than 4, were conducted. A meta-regression examined the influence of factors including Jadad score and time of final treatment session. Subgroup analyses for ENS frequency and electrode type (TENS versus PENS) were also carried out.

Results of the review

Twenty-nine RCTs (n=1,227) were included in the review. These studies provided 38 comparisons of ENS with placebo.

In terms of study quality, 9 studies scored less than 3 points on the Jadad scale and 15 studies scored 4 or 5.

The proportion of placebo patients that were double counted by being in studies that provided more than one comparison was 8.4% (63 out of 753).

The pooled effect size for all 38 studies showed a significant benefit for ENS therapy over placebo (p<0.0005). However, there was a highly significant degree of heterogeneity (Q=221, p<0.0005).

When only studies with a Jadad score of 4 or 5 were included in the analysis there remained a significant benefit for ENS therapy over placebo (p<0.0005).

The significant benefit with ENS compared with placebo remained when only one comparison per study was included (p<0.0005).

Authors' conclusions

ENS therapy provides significant pain relief as a single therapy, and is therefore a viable treatment for chronic musculoskeletal pain.

CRD commentary

The review question and the inclusion criteria were clearly stated. The authors searched some relevant databases, but the decision to limit the search to published articles reported in English might have increased the possibility that some relevant studies were not included in the review. The authors reported using appropriate methods to minimise bias and error in the study selection and validity assessment processes, but not in the extraction of data for the review. An appropriate validity assessment was conducted, and the results of this used to inform the analysis.

A meta-analysis was undertaken despite considerable clinical heterogeneity; however, appropriate sensitivity analyses and subgroup analyses were also undertaken. The decision to include non-independent comparisons in the meta-analysis appears inappropriate, but the authors were aware of the potential problems introduced and undertook analyses to determine the impact of their inclusion; this analysis showed similar effects. Despite the significant statistical heterogeneity found, studies showed a consistent direction of treatment effect. As a result of the inappropriate methodology it is not possible to accurately determine the reliability of the conclusions, although the results of the sensitivity analyses suggest that they may be robust.

Implications of the review for practice and research

The authors did not state any implications for practice or further research,


Empi Inc. (a distributor of ENS products).

Bibliographic details

Johnson M, Martinson M. Efficacy of electrical nerve stimulation for chronic musculoskeletal pain: a meta-analysis of randomized controlled trials. Pain 2007; 130(1-2): 157-165. [PubMed: 17383095]

Indexing Status

Subject indexing assigned by NLM


Chronic Disease; Humans; Musculoskeletal Diseases /complications; Pain /etiology; Pain Management; Randomized Controlled Trials as Topic; Transcutaneous Electric Nerve Stimulation; Treatment Outcome



Database entry date


Record Status

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.

Copyright © 2014 University of York.
Bookshelf ID: NBK74101


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