Study design: Systematic review.
Objective: To determine the effectiveness of transcutaneous electrical nerve stimulation (TENS) in the management of chronic LBP.
Summary of background data: Chronic low back pain (LBP) affects a significant proportion of the population. TENS was introduced more than 30 years ago as an adjunct to pharmacologic pain management. However, despite its widespread use, the usefulness of TENS in chronic LBP is still controversial.
Methods: We searched MEDLINE, EMBASE, PEDro, and the Cochrane Central Register of Controlled Trials (Issue 2, 2005), up to April 1, 2005. Only randomized controlled clinical trials (RCTs) evaluating the effect of TENS on chronic LBP were included. Two reviewers independently selected trials and extracted data using predetermined forms. Heterogeneity was tested with Cochrane's Q test. A fixed effect model was used throughout for calculating continuous variables, except where heterogeneity existed, in which case a random effects model was used. Results are presented as weighted mean differences with 95% confidence intervals (95% CI), where the difference between the treated and control groups was weighted by the inverse of the variance. Standardized mean differences were calculated by dividing the difference between the treated and control by the baseline variance. Standardized mean differences were used when different scales were used to measure the same concept. Dichotomous outcomes were analyzed with odds ratios.
Results: Two RCTs (175 patients) were included. They differed with respect to study design, methodologic quality, inclusion and exclusion criteria, characteristics of TENS application, treatment schedule, cointerventions, and measured outcomes. In one RCT, TENS produced significantly greater pain relief than the placebo control. However, in the other RCT, no statistically significant differences between treatment and control groups were shown for multiple outcome measures. Preplanned subgroup analyses, intended to examine the impact of different stimulation parameters, sites of TENS application, treatment durations, and baseline patient characteristics were not possible because of the small number of included trials.
Conclusions: Evidence for the efficacy of TENS as an isolated intervention in the management of chronic LBP is limited and inconsistent. Larger, multicenter, RCTs are needed to better resolve its role in this condition. Increased attention should be given to the risks and benefits of long-term use, which more appropriately addresses the realities of managing chronic low back pain.