A Cochrane review [Abstract] 1 included four trials with a total of 585 patients. The trials differed in study design, methodological quality, inclusion and exclusion criteria, type and method of TENS application, treatment schedule, co-interventions and final outcomes.
There was conflicting evidence about whether TENS was beneficial in reducing back pain intensity and consistent evidence in two trials (410 patients) that it did not improve back-specific functional status. There was moderate evidence that work status and the use of medical services did not change with treatment. Conflicting results were obtained from two studies regarding generic health status, with one study showing no improvement on the modified Sickness Impact Profile and another study showing significant improvements on several, but not all subsections of the SF-36 questionnaire. Multiple physical outcome measures lacked statistically significant improvement relative to placebo. In general, patients treated with acupuncture-like TENS responded similarly to those treated with conventional TENS. However, in two of the trials, an inadequate stimulation intensity was used for acupuncture-like TENS, given that muscle twitching was not induced. Optimal treatment schedules could not be reliably determined based on the available data. Adverse effects included minor skin irritation at the site of electrode placement.
A RCT included 236 adult patients consulting for chronic LBP, with orwithout radicular pain. Patients were randomly assigned toreceive either active (n = 117) or sham (n = 119) TENS in four 1-h dailytreatment sessions for 3 months. he primaryoutcome measured was improvement of functional status at 6 weeks(Roland-Morris Disability Questionnaire). Secondary outcome measureswere improvement of functional status at 3 months, pain relief (weeklyvisual analogue scale assessments), positive functional repercussions ofpain levels on quality of life, a diminution of the use of analgesic andanti-inflammatory medication, satisfaction with the overall treatmentstrategy and compliance. Functional status did not differ between the groups, whether at6 weeks or 3 months (p = 0.351 at 6 weeks). An improvement of at least 50% in lumbar painbetween the first and last assessments was achieved by25.0% of patients in the active TENS group comparedwith 6.7% in the sham TENS group (p = 0.0003),corresponding to a number needed to treat (NNT) of 5. Respective numbers in radicular pain were 33.8% vs. 15.0%, NNT=5. Other outcome measures did not differsignificantly between the two groups.
Comment: The quality of evidence is downgraded by sparse data and inconsistency (variability in results across studies and heterogeneity in interventions and outcomes).
Primary/Secondary Keywords