Ordog 1987.

Study characteristics
Methods	Type of study: randomised, double blind, placebo‐controlled, parallel design. Condition and number of participants randomised: acute trauma outpatients, 100. Groups: functioning TENS group (N = 25); placebo TENS group (N = 25); functioning TENS plus Tylenol (N = 25); placebo TENS plus Tylenol (N = 25).
Participants	Demographics: N = 100, age/gender not detailed. Setting: outpatients. Inclusion: acute trauma outpatients. Exclusion: < 21 yrs; hx cardiac disease or pacemaker; insufficient aptitude or personality for operation of apparatus; allergies to acetaminophen or codeine; pregnancy. Withdrawals/dropouts: not detailed.
Interventions	Where applied: at home by participant. Applied by: participant. Waveform: not detailed. Frequency: not detailed. Pulse duration: not detailed. Pulse amplitude/Intensity: instructed to adjust energy knob to level at which pain disappeared or until they felt a mild electric shock from the unit. Placebo TENS group: unit appeared like active but no electrical current transmitted to the skin. It produced the slight hum and vibration that active unit produced. Participants were not told that the functioning units could produce a mild electrical shock by turning up the unit. Electrodes: 2 metal electrodes and a disposable sterile skin pad, size not detailed. Applied over area of injury or as close to it as practical. Duration and frequency of Rx: could be worn at all times or as often as required for pain control. Device/manufacturer: disposable TENS‐PAC unit measures ½ x 3 x 4 inches.  Dow Corning, Arlington, Tennessee. Adverse effects: no complications and no side effects except a mild tingling sensation at higher output levels, 20% of participants reported this effect.
Outcomes	Pain outcome: 11 point VAS for pain intensity, administered pre Rx, after two days of Rx, and a month after initial injury. ITT/per protocol analysis: not detailed. Statistical analysis: statistically significant reduction in pain severity in functioning TENS vs placebo group at day 2, not at 1 month. No significant difference between functioning TENS unit and Tylenol group when either the subjective levels of pain versus time or pre‐Rx and post‐Rx pain levels at 2 days and 1 month were compared. Mean length of use of TENS in all groups was 3 days versus a mean of 5 days for the oral analgesics in the 2 Tylenol groups.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"One hundred consecutive consenting acute trauma outpatients seen by the researcher were randomly assigned to four pain treatment groups. Randomization of the TENS‐PAC units was achieved by mixing the two boxes of 50 functioning and 50 placebo units together. A decoding process was released when all of the TENS‐PAC units were returned after the trial was completed. All of the units were returned to the researcher following the trial to determine which units the patient had and also to assure their function".
Allocation concealment (selection bias)	Low risk	"A decoding process was released when all of the TENS‐PAC units were returned after the trial was completed. All of the units were returned to the researcher following the trial to determine which units the patient had and also to assure their function".
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	No details provided.
Source of funding bias	Unclear risk	No details provided.
Blinding (Participant)	High risk	It is impossible to adequately blind participants who receive electrical stimulation. "In the study, 50% of the patients received a functioning TENS‐PAC, and the other 50% received a ‘placebo’ unit, which appeared and operated in all ways similar to the functioning unit except that no electrical current was transmitted to the skin. This ‘placebo’ unit was originally a functioning TENS‐PAC, but in this unit, an internal wire that supplied the electrical current to the skin was cut. The TENS‐PAC produces a slight hum and vibration that the ‘placebo’ unit also produced. The ‘placebo’ units were prepared by an independent source, and neither the researcher nor the patient was able to identify which unit was given until the trial was completed. The possibility that the patients might have figured out whether they had the placebo units seems remote, as patients were not told that the functioning units can produce a mild electrical shock by turning up the unit. As none of the patients had used TENS previously, it is unlikely that they would have known that an electrical shock could be produced only by the functioning units".
Blinding (Outcome Assessor)	Low risk	"The 'placebo' units were prepared by an independent source, and neither the researcher nor the patient was able to identify which unit was given until the study was completed".
Sample Size	High risk	TENS (N = 25); placebo TENS (N = 25); TENS plus Tylenol (N = 25); placebo TENS plus Tylenol (N = 25).