The effect of three alternative keyboard designs on forearm pronation, wrist extension, and ulnar deviation: a meta-analysis.

The growth of computer keyboard use in the workplace is believed to be one important determinant of the increased prevalence of work-related musculoskeletal disorders of the upper extremity (MSD-UE). One possible contributing factor to the development of MSD-UE is the flat standard keyboard, which places the forearm and wrist in biomechanically awkward postures. This meta-analysis examines the efficacy of three alternative keyboard designs, adjustable slope (AS), split fixed-angle (FA), and adjustable open-tented (AT), in reducing forearm pronation, wrist extension, and ulnar deviation. Analyses of pooled effect size from six studies indicated that the AT had a large effect on pronation (r= 0.85) and ulnar deviation whereas the FA had a large effect only on ulnar deviation (r= 0.79). The AS was found to have a large effect (r= 0.66) on wrist extension. The FA had a moderate effect on pronation (r= 0.33) and wrist extension (r= 0.30). None of these keyboards were found to have a significant effect on all three postures. This meta-analysis has implications for clinicians by providing objective information that may assist with the selection of an alternative keyboard that best reduces an identified problematic posture.