Tittiranonda 1999.

Methods	Randomised, single‐blind, placebo‐controlled trial of three ergonomic keyboard designs Blinded assessors Quality of diagnostic criteria = B
Participants	Total n = 80 participants randomised Intervention group 1 n = 20 participants Intervention group 2 n = 20 participants Intervention group 3 n = 20 participants Placebo group n = 20 participants 34 males; 46 females Mean ± SD age: Intervention group 1: 45 ± 8 yrs Intervention group 2: 41 ± 10 yrs Intervention group 3: 45 ± 7 yrs Placebo group: 44 ± 8 yrs Inclusion criteria: 1. Medical history and physical examination consistent with CTS 2. Paraesthesia, numbness or tingling on volar surface of digits 1‐3 3. Numbness, tingling or diminished sensation in hands with use or with awkward posture 4. Symptom duration of at least 1 week or having occurred at least 20 times in past year 5. Positive Phalen's or Tinel's sign 6. Full‐time employee in current job for > 3 months 7. Use computer keyboard greater than or equal to 4 hours per day or greater/equal to 20 hours per week Exclusion criteria: 1. Acute major trauma to hand, wrist or shoulder within last year 2. Thoracic outlet, cervical root or pronator teres syndromes on physical exam 3. Previous hand or wrist surgery 4. CTS diagnosis > 2 years prior to assessment date
Interventions	Intervention group 1: Apple Adjustable keyboard for 6 months Intervention group 2: Comfort Keyboard System for 6 months Intervention group 3: Microsoft Natural Keyboard for 6 months Placebo group: Regular keyboard for 6 months
Outcomes	Outcomes assessed at 6 months 1. Phalen's sign 2. Tinel's sign 3. Phalen test time (in seconds) 4. Pain using visual analogue scale (0 = no pain, 10 = worst pain) 5. Hand function using questionnaire (11 items modified from Levine/Pransky scored on visual analogue scale)
Notes	Attempts to clarify allocation method with authors were unsuccessful Change scores are reported for continuous outcomes. Negative values indicate worsening of symptoms or function. For the majority of the outcomes, data were reported only for the combined group of participants (i.e. data were rarely reported for the CTS subgroup only; instead, combined data on CTS and tendonitis patients were reported). Values for Phalen's sign and Tinel's sign are an aggregate of right and left hands.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Eligible subjects were assigned one of the three alternative keyboard designs or a conventional placebo by using a random permuted block method [Pocock, 1991] and were stratified on the basis of disorder type (carpal tunnel syndrome and tendonitis or tendonitis only). Therefore, at the start of the study, there were 4 treatment groups with 20 subjects in each group." Comment: the randomisation sequence was probably adequately generated.
Allocation concealment (selection bias)	Unclear risk	Quote: "Eligible subjects were assigned one of the three alternative keyboard designs or a conventional placebo by using a random permuted block method [Pocock, 1991] and were stratified on the basis of disorder type (carpal tunnel syndrome and tendonitis or tendonitis only). Therefore, at the start of the study, there were 4 treatment groups with 20 subjects in each group." Comment: not enough information to determine whether the allocation sequence was adequately concealed until interventions were assigned.
Blinding (performance bias and detection bias) Self‐reported outcomes	High risk	Quote: "This was a 6‐month, prospective, observer‐blinded, placebo‐controlled, randomized clinical trial comparing four keyboard treatments in 80 subjects with carpal tunnel syndrome and/or tendonitis." Comment: it is unlikely that participants were blinded to treatment allocation, especially given the nature of the interventions. Images of the four keyboards are displayed in Figure 2 of the publication and the ergonomic keyboards look different to the placebo keyboard. However, the investigators did make efforts to blind participants to treatment allocation (as per quote below). Quote: "For subjects who were randomized to the placebo group, their own keyboard was taken to the ergonomics laboratory one week prior to the trial. At the laboratory, dust particles were expelled from the inner mechanism and outer surface of the keyboards using compressed air. A label containing an alphanumeric identification number and a message that read "This keyboard has been modified as part of an interventional field trial" was attached to the left corner of the keyboard cover. An additional label which read "This keyboard has been internally modified as part of the LLNL keyboard field study. Please do not attempt to repair or open it. If technical problems arise, call for immediate assistance" was attached to the bottom of the keyboard. The screws underneath the keyboard platform were painted shut with blue‐coloured ink to prevent tampering. On the day of randomisation, the keyboards were returned to the subjects and they were told that their keyboard had been "modified" in some way and that the researchers were blinded to the modification to comply with the study protocol."
Blinding (performance bias and detection bias) Other outcomes	Low risk	Quote: "Physical examination of the upper extremities was conducted for each participant at baseline and at the end of the 6‐month trial. The examination was standardized and consisted of inspection, palpation, passive and resisted movements, and a series of provocative tests that included timed Phalen’s, Tinel’s, and Finkelstein’s tests. The examiners were blinded to previous medical history and keyboard assignments." Comment: outcome assessors were probably blinded to treatment allocation.
Incomplete outcome data (attrition bias) 3 months or less	High risk	Quote: "Eleven (14%) subjects withdrew from the study during the 6 months (Table IV). Withdrawals were most frequent in the kb2 group (n = 9); five of these were due to keyboard mechanical failure. One each withdrew from the other alternative keyboard groups. Reasons given for withdrawal were: frustration with their reduced productivity (n = 2, kb2) and increased discomfort (n = 1, kb2), inadequate workspace for use of detached numeric/function key pad (n = 1, kb1), and lack of time commitment (n = 1, kb3)." Comment: the specific time points at which participants withdrew, and the number of participants in the CTS subgroup who withdrew, were not reported (the number reported refers to the total sample).
Incomplete outcome data (attrition bias) After 3 months	High risk	Comment: See above
Selective reporting (reporting bias)	High risk	Quote: "All analyses were carried out for each limb for all subjects and then for each disorder type separately (CTS and tendonitis and tendonitis only)." Comment: for the majority of the outcomes, data were reported only for the combined group of participants (i.e., few data on the CTS subgroup were reported)
Other bias	Low risk	No other sources of bias identified.

CTR: carpal tunnel release 
 CTS: carpal tunnel syndrome 
 SD: standard deviation