Keyboard Use and Musculoskeletal Disorders
Computer use has been associated with musculoskeletal problems of the upper extremities: neck, shoulders, arms, etc. Several postures and behaviors have been suggested as related to these disorders, including position in which the hands are held, neck and shoulder position, wrist posture and hyperextension of the fingers, to name a few.
What Problem Was Studied?
To determine appropriate workplace interventions, the postures and behaviors associated with musculoskeletal disorders must be specifically identified and measured. However, the tools and methods used for measuring human motion – such as electric goniometry, optical markers and electromagnetic systems – are highly technical, expensive and cumbersome to use. Having an evaluator observe a client using a keyboard is less expensive and easier, but the results are dependent upon the individual observers and may not be transferable from one observer to another.
A research team from the University of Pittsburgh in Pennsylvania, including Arthritis Foundation-funded occupational therapist and researcher Nancy A. Baker, OTR/L, developed a valid and reliable observational instrument to measure keyboarding postures. The Keyboard-Personal Computer Style instrument is a 19-item instrument that documents postures and behaviors during typing. The research team designed a study to determine whether this new instrument can discriminate between people with and without upper-extremity musculoskeletal disorders (MSD-UE).
What Was Done in the Study?
A total of 42 people participated in the study; 21 with an MSD-UE and 21 controls without any disorder. A variety of diagnoses were eligible, including radiating neck pain, carpal tunnel syndrome and arthritis. The participants were interviewed and observed at their own workstations using their own keyboards. Three cameras were set up around the participants and they typed a standardized paragraph that took approximately 10 minutes to complete. Only the final minute of typing was rated using the newly developed instrument.
What Were the Study Results?
After analyzing the data from 19 different postures from all 42 people, only one factor demonstrated good ability to predict who had an MSD-UE: neck flexion angle ≥20 degrees. This means that the participants who had their heads pointing downward had a higher likelihood of having some form of upper extremity problem. In fact, all participants who identified themselves as having a neck disorder kept their heads in a downward position at ≥20 degrees. Furthermore, 90 percent of those who did not have a neck disorder kept their heads positioned more upright, with a flexion angle of 20 degrees or less.
What Does This Mean for People With Arthritis?
Baker is quick to point out that these results “do not indicate that neck flexion is a causal factor for developing an upper-extremity musculoskeletal disorder. These participants could have adapted their neck postures after they developed the disorder.” However, other studies have found that a flexed neck posture also is associated with MSD-UE. Computer users may want to ensure that their head is as upright as possible by making sure the monitor is high enough, using a document holder when working off paper documents, and shifting their eyes to look for keys rather bending their neck.
Baker hopes that, with additional studies, the instrument the team developed could eventually be used to identify individuals with keyboarding styles that put them at risk for MSD-UE. Once those behaviors have been identified, they can be addressed through equipment set-up and training.
Baker NA, Sussman NB, Redfern MS. Discriminating between individuals with and without musculoskeletal disorders of the upper extremity by means of items related to computer keyboard use. J Occup Rehabil 2008;18:157-65.
