Transcutaneous electrostimulation for osteoarthritis of the knee

Abstract

Background: Osteoarthritis is the most common form of joint disease and the leading cause of pain and physical disability in the elderly. Transcutaneous electrical nerve stimulation (TENS), interferential current stimulation and pulsed electrostimulation are used widely to control both acute and chronic pain arising from several conditions, but some policy makers regard efficacy evidence as insufficient.

Objectives: To compare transcutaneous electrostimulation with sham or no specific intervention in terms of effects on pain and withdrawals due to adverse events in patients with knee osteoarthritis.

Search strategy: We updated the search in CENTRAL, MEDLINE, EMBASE, CINAHL and PEDro up to 5 August 2008, checked conference proceedings and reference lists, and contacted authors.

Selection criteria: Randomised or quasi-randomised controlled trials that compared transcutaneously applied electrostimulation with a sham intervention or no intervention in patients with osteoarthritis of the knee.

Data collection and analysis: We extracted data using standardised forms and contacted investigators to obtain missing outcome information. Main outcomes were pain and withdrawals or dropouts due to adverse events. We calculated standardised mean differences (SMDs) for pain and relative risks for safety outcomes and used inverse-variance random-effects meta-analysis. The analysis of pain was based on predicted estimates from meta-regression using the standard error as explanatory variable.

Main results: In this update we identified 14 additional trials resulting in the inclusion of 18 small trials in 813 patients. Eleven trials used TENS, four interferential current stimulation, one both TENS and interferential current stimulation, and two pulsed electrostimulation. The methodological quality and the quality of reporting was poor and a high degree of heterogeneity among the trials (I(2) = 80%) was revealed. The funnel plot for pain was asymmetrical (P < 0.001). The predicted SMD of pain intensity in trials as large as the largest trial was -0.07 (95% CI -0.46 to 0.32), corresponding to a difference in pain scores between electrostimulation and control of 0.2 cm on a 10 cm visual analogue scale. There was little evidence that SMDs differed on the type of electrostimulation (P = 0.94). The relative risk of being withdrawn or dropping out due to adverse events was 0.97 (95% CI 0.2 to 6.0).

Authors' conclusions: In this update, we could not confirm that transcutaneous electrostimulation is effective for pain relief. The current systematic review is inconclusive, hampered by the inclusion of only small trials of questionable quality. Appropriately designed trials of adequate power are warranted.

Conflict of interest statement

None.

Figures

1

Flow chart

2

Methodological characteristics and source of funding of included trials. (+) indicates low risk of bias, (?) unclear and (‐) a high risk of bias on a specific item.

3

Forest plot of 16 trials comparing the effects of any type of transcutaneous electrostimulation and control (sham or no intervention) on knee pain. Values on x‐axis denote standardised mean differences. The plot is stratified according to type of electrostimulation. Law 2004 reported on knee level, we inflated the standard error with sqrt(number knees)/sqrt(number patients) to correct for clustering of knees within patients. Adedoyin 2005 and Cheing 2002 contributed with two comparisons each. In Adedoyin 2005, the standard error was inflated and the number of patients in the control group was halved to avoid duplicate counting of patients when including 2 both comparisons in the overall meta‐analysis. Data relating to the 3, 2, 3 and 4 active intervention arms in Cheing 2003, Grimmer 1992, Law 2004 and Defrin 2005, respectively, were pooled.

4

Funnel plot for effects on knee pain. 
 Numbers on x‐axis refer to standardised mean differences (SMDs), on y‐axis to standard errors of SMDs.

5

Forest plot of 8 trials comparing patients withdrawn or dropped out because of adverse events between any transcutaneous electrostimulation and control (sham or no intervention). Values on x‐axis denote risk ratios. Risk ratios could not be estimated in 5 trials, because no drop‐out occurred in either group. The plot is stratified according to type of electrostimulation. Data relating to the 3 and 2 active intervention arms in Cheing 2003 and Grimmer 1992, respectively, were pooled.

6

Forest plot of 9 trials comparing the effects of any type of transcutaneous electrostimulation and control (sham or no intervention) on function. Values on x‐axis denote standardised mean differences. The plot is stratified according to type of electrostimulation. In Adedoyin 2005, the standard error was inflated and the number of patients in the control group was halved to avoid duplicate counting of patients when including both comparisons in the overall meta‐analysis.

7

Funnel plot for effects on functioning of the knee. 
 Numbers on x‐axis refer to standardised mean differences (SMDs), on y‐axis to standard errors of SMDs.

8

Forest plot of 3 trials comparing patients experiencing any adverse event between any transcutaneous electrostimulation and control (sham or no intervention). Values on x‐axis denote risks ratios. The risk ratio in one TENS trial could not be estimated because no adverse event occurred in either group. The plot is stratified according to type of electrostimulation.

9

Forest plot of 4 trials comparing patients experiencing any serious adverse event between any transcutaneous electrostimulation and control (sham or no intervention). Values on x‐axis denote risk ratios. Risk ratios could not be estimated in 3 trials, because no serious adverse event occurred in either group. The plot is stratified according to type of electrostimulation. Data relating to the 3 active intervention arms in Cheing 2003 were pooled.

1.1. Analysis

Comparison 1 Any type of transcutaneous electrostimulation versus control, Outcome 1 Pain.

1.2. Analysis

Comparison 1 Any type of transcutaneous electrostimulation versus control, Outcome 2 Number of patients withdrawn or dropped out because of adverse events.

1.3. Analysis

Comparison 1 Any type of transcutaneous electrostimulation versus control, Outcome 3 Function.

1.4. Analysis

Comparison 1 Any type of transcutaneous electrostimulation versus control, Outcome 4 Number of patients experiencing any adverse event.

1.5. Analysis

Comparison 1 Any type of transcutaneous electrostimulation versus control, Outcome 5 Number of patients experiencing any serious adverse event.