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. 2012 Aug 15;2012(8):CD008570. doi: 10.1002/14651858.CD008570.pub2

Conlon 2008

Methods RCT. Participants were randomised into 1 of 4 intervention groups. The randomisation was done by means of a computer‐generated permuted‐block sequence
Participants Participants consists of employees working at a large aerospace engineering firm in California, US that estimated working at a computer for at least 20 hours per week and employed as an member of the engineering staff (93%) or a professional position supporting engineering (7%) and have completed the health questionnaire and at least 4 weekly surveys. Since 1 of the mouse interventions could only be used right‐handed, only those who agreed to use their right hand for the mouse pointing device intervention were eligible for the study
206 people volunteered out of total 437 eligible employees. The participants were randomised into 4 groups:

  1. alternative mouse with a forearm support board (n = 51);

  2. conventional mouse with a forearm support board (n = 51);

  3. alternative mouse alone (n = 52);

  4. conventional mouse alone (n = 52);


154 people volunteered for the nerve conduction testing
Interventions The study compared 4 different interventions for computer workstations

  1. Alternative mouse with a forearm support board: the forearm support board was a large butterfly‐shaped board (36 by 21 inches) that was attached to a desk and provided padded forearm support (ButterflyBoard, Metamorphosis Design and Development, Atlanta, GA, US). The board was inclined upwards at approximately 5° and the surface could accommodate a keyboard and mouse, and the alternative mouse was a 3M product that had a vertical handle for grasping and a flat base to support the ulnar side of the hand and used a roller ball for tracking. The forearm was in approximately 15° of pronation during use (Renaissance Mouse, 3M Corporation, St Paul, MN, US)

  2. Conventional mouse with a forearm support board: forearm support board (as in (1)) and conventional mouse used an optical LED for tracking the mouse movement and required the hand to be in an almost fully pronated posture during operation (IntelliMouse Optical, Microsoft Corporation, Redmond, WA, US)

  3. Alternative mouse alone: the alternative mouse was a 3M product that had a vertical handle for grasping and a flat base to support the ulnar side of the hand and used a roller ball for tracking. The forearm was in approximately 15° of pronation during use (Renaissance Mouse, 3M Corporation, St Paul, MN, US) (as in (1)

  4. Conventional mouse alone: conventional mouse using an optical LED for tracking the mouse movement and required the hand to be in an almost fully pronated posture during operation (IntelliMouse Optical, Microsoft Corporation, Redmond, WA, US) (as in (2))
Outcomes Primary outcome:

  1. Incidence of MSD: subject reported a discomfort intensity level of > 5 on the weekly survey, or used a pain medication for ≥ 2 days per week for upper body discomfort that they thought was related to computer work was referred for an examination. The examination protocol focused on the body region with discomfort and was performed by 1 physician who was blinded to the intervention status. The examination protocol assessed for the presence of 40 upper extremity and neck MSDs

  2. Mean discomfort score: the discomfort scores were assessed for 3 body regions, the neck/shoulders, right elbow/forearm/wrist/hand, and left elbow/forearm/wrist/hand, were assessed for the worst discomfort during the preceding 7 days using a 0 to 10 point scale (0 = no discomfort; 10 = unbearable discomfort). Subjects were asked whether they thought the discomfort was the result of (a) working on a computer, (b) an acute injury at work, or (c) activities or an injury away from work. Only discomfort reported by the subject as a result of working on their computer was included in the data analysis. The mean discomfort scores for pre‐intervention and post‐intervention (pre‐intervention mean discomfort scores were obtained from the weekly surveys before intervention by averaging all the pre‐intervention scores for each subject to a single value; post‐intervention discomfort scores were obtained from the weekly surveys after intervention. These scores were collapsed into a single postintervention score by body region. The first 8 weeks of post‐intervention scores were left‐censored)
Notes The study was reported in 2 papers (see Conlon 2008)
Risk of bias
Bias Authors' judgement Support for judgement
Random sequence generation (selection bias) Low risk "Participants were randomised into one of four intervention groups. The randomisation was done by means of a computer‐generated permuted‐block sequence"
Allocation concealment (selection bias) Unclear risk No information provided
Blinding of participants and personnel (performance bias) All outcomes High risk Blinding of participants not possible given that different equipment was tested in the 4 groups
Blinding of outcome assessment (detection bias) Musculoskeletal disorders High risk MSDs: although the examination was performed by 1 physician who was blinded to the intervention status, the pre‐examination criteria for inclusion in the examination was determined by subjective discomfort levels
Incomplete outcome data (attrition bias) All outcomes Low risk The analysis followed an ITT protocol. As participant exited the study they completed the exit questionnaire
Selective reporting (reporting bias) Low risk All the results for musculoskeletal discomfort, MSDs, and distal motor latency were reported
Other bias High risk Those who volunteered for the study were different:

  1. "females were more likely to volunteer for the study than males (P < 0.01)"

  2. "participants had higher levels of right arm and neck/shoulder discomfort (P < 0.01)"

  3. "participants were also more likely to take medications for discomfort related to work and had higher estimates of the number of days at work that were affected by discomfort (P = 0.05)"'


Owing to this the effect may be larger than expected