Work related shoulder disorders: quantitative exposure-response relations with reference to arm posture

Abstract

Aims: To determine quantitative exposure-response relations between work with highly elevated arms and supraspinatus tendinitis, shoulder pain with disability, and shoulder pain without disability. Methods: A cross sectional study was conducted in a historical cohort of 1886 males from three occupational groups. Exposure measurements were performed for four consecutive working days in a random sample of 72 currently employed subjects. Individual work histories were obtained by questionnaire and register data. Health status was ascertained by physical examination blinded towards exposure and symptoms. Data were analysed by generalised estimating equation and multiple logistic regression with adjustment for potential confounders. Results: For current upper arm elevation above 90˚, a duration increment of 1% of the daily working hours was associated with odds ratios of 1.23 (95% CI 1.10 to 1.39) for supraspinatus tendinitis, 1.16 (95% CI 1.08 to 1.24) for shoulder pain with disability, and 1.08 (95% CI 1.04 to 1.13) for shoulder pain without disability. The outcomes were not related to duration of employment in one of the three trades. Conclusions: Quantitative exposure-response relations were established between current work with highly elevated arms and clinically verified shoulder disorders. Substantial long term cumulative effects were not shown. A potential for primary prevention was revealed. Shoulder disorders have considerable impact on sickness absence, 1 utilisation of primary 2 and secondary 3 4 health services, and premature withdrawal from the labour market.5 Several occupational exposures have been associated with shoulder complaints and disorders; these include work with elevated arms, monotonous repetitive work, and forceful exertions.6 7 However, most epidemiological investigations into the work relatedness of shoulder disorders suffer from methodological limitations, in particular concerning exposure assessment and verification of disorders.8 The present lack of knowledge hampers the development of guidelines and regulations to prevent work related shoulder disorders. 9Work with elevated arms has been hypothesised to cause degenerative changes in the rotator cuff tendons 10 and thus predispose to tears. It is unclear how high the arms must be elevated and for how long a time before the harmful effects occur. Existing evidence points to elevation angles above 60˚, but the majority of studies cannot separate effects of postural load and monotonous repetitive work.6 Few studies have focused on elevation angles above 90˚, 11-13 and the literature is scarce on the effects of varied patterns of arm elevation. 14-16We aimed to establish quantitative exposure-response relations between work with highly elevated arms and shoulder disorders. The study was based on direct measurements of upper arm elevation, register based data on occupational histories, and physical examinations blinded to exposure and symptoms. METHODS PopulationWe conducted a cross sectional study in a historical cohort of male machinists...

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