Clinical epidemiological study of relations between upper limb soft tissue disorders and repetitive movements at work

A case-control study of subjects attending orthopaedic clinics has examined the influence of activity at work on risk of upper limb soft tissue disorders. The aims of the study were to determine: whatactivitiesare associated with clinically defined upper limb soft tissue disorders; the relative risks of these disorders in different activities at work and elsewhere; what proportion of clinically diagnosed upper limb soft tissue disorders in the community as a whole are attributable to physical activities at work; and what major ergonomic factors can be identified as common to high risk situations. Subjects between the ages of 16 and 65 attending orthopaedic clinics in Doncaster, Edinburgh and Nottingham, in which defined conditions were diagnosed by the participating orthopaedic surgeons, were invited to take part. Diagnostic criteria for the cases included all soft tissue conditions of the upper limb to which repetitive strain may contribute. Controls were subjects attending the same, clinics within the same age-range whose clinical diagnoses did not include disease of the upper limb, cervical or thoracic spine. The case:control ratio was 1:2. Subjects who agreed to participate answered a questionnaire about activities at work during the previous two years. The questionnaire was designed to elicit as much information as possible, within practical constraints, about repetitive movements of the upper limb at work, including detailed interrogation about the direction and range of movements at each joint or group of joints, enquiring additionally about complex movements thought to be relevant to repetitive strain injuries. The questionnaire also asked about frequency of repetition, application of force, spells of activity, total duration of activity, and sustaining fixed postures. Information on use of tools, wet conditions, sports and hobbies, height and weight was also recorded.580 cases and 996 controls were studied, representing 96% and 93% respectively of those invited to participate. The diagnoses of the cases included soft tissue conditions affecting the shoulder, elbow, forearm, wrist, thumb, hand and fingers. The two most frequent diagnoses were carpal tunnel syndrome and ganglion; tenosynovitis of the forearm accounted for only 4% of cases; tenovaginitis of the tendons of the thumb (de Quervain’s disease) for 5% of cases. The diagnoses of the controls included traumatic, degenerative and inflammatory conditions, mostly of the legs and lower back. Forty percent of controls and 12% of cases attributed their illness to an accident, and 33% of controls and 23% of cases often worked in wet conditions. Women predominated among the cases (70%) and men among-.the-controls (66%);- Over four-fifths of both cases and controls had worked in at least one job during -the previous two years.The statistical analysis aimed to identify factors contributing to risk of injury irrespective of recruiting centre, and did not study local differences in these relationships. Jobs statistically significantly over-represented among the cases compared with controls were cleaner, hairdresser, video display unit operator and other keyboard users, butcher, music teacher and machine operator. Jobs over-represented among the controls compared with the cases included miner and policeman. Cases in general were older and shorter than controls. Cases with conditions of the wrist and forearm were heavier than controls (after adjustment for height), and more likely to be female.Associations between movements performed at work and risk of upper limb soft tissue disorder were demonstrated. Notably, movements which were associated with arm conditions included repeated gripping in the palm with fingers and thumb, related to finger conditions; pinching between thumb and fingers, not in the palm, related to thumb conditions; bending the thumb, related to forearm tenosynovitis; wrist supination/pronation with wrist and forearm conditions; rotating the shoulder with arm raised, related to shoulder conditions.Rates of movements above the once per minute threshold apparently influenced only risk of thumb conditions in relation to rate of wrist flexion and – extension (except for a negative association between rate of rotating the wrist and tenosynovitis of the forearm). Hours spent per day performing movements more frequently than once per minute influenced risk of forearm—tenosynovitis- -in relation to pinching, tapping with the fingers and flexing/extending the-wrist; ; and-risk of’shoulder conditions in relation to bending the elbow. Some other positive and negative associations between movements of joints anatomically rather distant from the site of disease were demonstrated.Sustaining a fixed position increased the risks of thumb, wrist and forearm conditions in relation to keeping the thumb bent. Performing movements forcibly did not appear to influence the risks, except for an association between flexing the elbow forcibly and risk of wrist or forearm conditions. The influence of interactions between movements has not yet been examined.Sporting activities contributed to risks of thumb and elbow conditions. Hobbies involving use of the arms contributed to risk of wrist and forearm conditions.Calculation of attributable risks of injury in relation to named occupations indicated that work as a keyboard operator, cleaner, hairdresser and machine operator together account for about 9% of cases of upper limb soft tissue disorders presenting to orthopaedic clinics nationally. The results suggest that occupation makes a not negligible contribution to the upper limb soft tissue disorders seen at orthopaedic clinics, and that attention should be directed initially towards the modification of work activities to minimise use of the thumb, pronation/supination and flexion/extension of the wrist, and rotation of the shoulder with arm elevated. Further ergonomic and epidemiological studies of high risk occupations would enable these findings to be translated into recommendations for task or machine modification. Studies, similar to that reported here, but based in other areas where different jobs are represented might identify other potentially harmful components of activities at work, and would provide an opportunity to test the stability of the relationships described here. Additional analyses of our data, to study the influence of interactions between movements, and relations between activities and injury specific to recruiting centre, would be desirable. “”