Computer work and musculoskeletal disorders of the neck and upper extremity: A systematic review
From: BMC Musculoskeletal Disorders 2010, 11:79
This review examines the evidence for an association between computer work and neck and upper extremity disorders (except carpal tunnel syndrome). A systematic critical review of studies of computer work and musculoskeletal disorders verified by a physical examination was performed. A total of 22 studies (26 articles) fulfilled the inclusion criteria. Results show limited evidence for a causal relationship between computer work per se, computer mouse and keyboard time related to a diagnosis of wrist tendonitis, and for an association between computer mouse time and forearm disorders. Limited evidence was also found for a causal relationship between computer work per se and computer mouse time related to tension neck syndrome, but the evidence for keyboard time was insufficient. Insufficient evidence was found for an association between other musculoskeletal diagnoses of the neck and upper extremities, including shoulder tendonitis and epicondylitis, and any aspect of computer work.
There is limited epidemiological evidence for an association between aspects of computer work and some of the clinical diagnoses studied. None of the evidence was considered as moderate or strong and there is a need for more and better documentation.
As related to tension neck syndrome, we will cover this specific entity from the study:
Tension neck syndrome, a condition characterized by pain complaints and neck muscle tenderness elicited by palpation and/or movement of the neck, is in this review by far the most common diagnosis in the neck region and is included in the examination protocol of a majority of the included studies. In three studies the diagnosis somatic pain syndrome, with a similar definition, is used. In a prospective study of newly hired computer workers hours of keying per week was not associated with incident tension neck syndrome. The baseline cross-sectional analysis in the NUDATA-study showed an increased risk for tension neck syndrome, including an exposure-effect relationship, for work with a computer mouse for more than 15-20 h/w. A similar relationship was not observed for keyboard use. The one-year incidence of tension neck syndrome was too low for reliable analyses even if the NUDATA-study included several thousand subjects. Another much smaller and older study found no association between amount of computer work in itself and tension neck syndrome. A community-based case-control study found for women a significant association for shoulder-neck diagnosis (58% of affected subjects had tension neck syndrome) with computer work ≥ 4 hours/day. Several studies of low to moderate quality have found an association between computer work and clinical findings. These studies examine mainly keyboard work. This is supported by a study finding more trigger points and pain provoked by neck sideways flexion in subjects performing data entry work compared with subjects doing data dialogue work. A prospective study of air-traffic controllers changing from varied computer work to a strict mouse-based system, only found significant increase of musculoskeletal disorders in the neck and shoulders among the younger half of the study group. At baseline a majority of the affected controllers had tension neck syndrome, however there is no information on specific diagnoses at follow-up.
The work-related load of the neck in computer work is influenced by the computer workstation lay-out (including use of specific devices) and individual working technique, and several of the studies in this review have tried to take accord of some of these factors. The NUDATA-study with more than six thousand subjects found no significant associations between tension neck syndrome and several recorded ergonomic factors. Among newly hired computer workers a “protective” effect of inner elbow angle above 121° during keyboard use was observed, but this effect was attenuated with increasing hours of keying per week. This study also showed a tendency for increased risk with shoulder flexion above 35° during mouse use, and for a protective effect of the use of chair armrests. In a randomized controlled intervention study a forearm support board was associated with a reduced incidence of neck/shoulder disorders among female call centre operators (tension neck syndrome was found in 59% of the subjects with one or more neck/shoulder diagnoses). However, this relation was not found in a similar randomized intervention study on engineers (male majority), and the NUDATA study gave no support for a protective effect of forearm support on the occurrence of tension neck syndrome. In a study with no observed association to computer work in general, an association to tension neck syndrome was found in subjects with limited rest break opportunities, in subjects who had their keyboard too highly placed relative to elbow level, and in subjects who used bifocal glasses. The association of tension neck syndrome to use of bifocals was also shown in another study. Neck flexion more than 20° was identified as a risk factor, however the outcome measure was not precisely described.
In a comparison of daily workload by comparing part-time and full-time air-traffic controllers, there was no difference in neck-shoulder or arm-hand disorders. However, a significant effect was observed on subjective complaints from the same body regions, illustrating that an effect seen in complaint scores may not be reflected in the number of diagnoses from a physical examination.
Previous critical reviews that include evidence based on subjective reports of pain and symptoms conclude mostly with a causal relationship between computer work per se (or computer work in general) and neck pain. In the NUDATA-study the results on tension neck syndrome were supported by baseline data for neck and shoulder pain symptoms; neck symptoms showed a weaker but still significant exposure-effect relationship to mouse use but not to keyboard use. Some indications were presented that the incident of new neck pain symptoms was associated to mouse use more than 30 h/w and almost significant to keyboard use for more than 15 h/w. Several cross-sectional studies recording subjective pain symptoms only have shown an association between neck and shoulder pain and computer work. However, a number of high quality prospective studies do not confirm these findings. Aspects of work station design, data equipment and work technique have been shown to influence subjective reporting, such as forearm support for neck symptoms, and mouse position, mouse design and neck flexion angle for neck/shoulder symptoms.
Jensen et al. found a lower number of EMG-gaps and a more repetitive activity on the mouse side compared to opposite side, indicating a more harmful muscle activity pattern on the mouse side. However, increased activity in the trapezius muscle has also been reported after exposure to psychological stress and high precision demands. The population at risk is perhaps more prone to a high level of perceived muscular tension, which has been found even when adjusting for high physical exposure, high job strain and age. Several studies document an interaction between mechanical work load in computer work and psychosocial risk factors.
Evidence of a causal relationship for tension neck syndrome?
Of the studies included in this review one cross-sectional study of moderate quality suggests an association between computer work per se and tension neck syndrome. One case-control study of high quality had similar findings, especially for women. One prospective study of high quality found no association. With respect to specific aspects of computer work, one very high quality prospective study documents a clear association between mouse use and tension neck syndrome. In a prospective study following a work-task redesign with intensified mouse use, a similar effect was seen in the younger half of the involved workers. In two very high quality intervention trials the introduction of forearm support protected against shoulder-neck diagnoses among female call centre operators but not in among male engineers. Several high quality prospective studies of symptoms do not support an association. Possible pathomechanisms have been documented.
The authors conclude that there is limited evidence for a causal relationship for computer work per se and for mouse time, but not for keyboard time. Several pathophysiological and experimental studies give biological plausibility to this conclusion. However, indications are found of the importance of individual working technique and work station lay-out in causality of tension neck syndrome. These include lack of forearm support, non-neutral position of forearm and neck flexion. This conclusion is in part also a consequence of the limited number of studies.
Resource: Neck and shoulder symptoms and disorders among Danish computer workers
