Are occupational repetitive movements of the upper arm associated with rotator cuff calcific tendinopathies?

Calcifying tendinopathy (CT) of the shoulder is a common painful disorder, although the etiology and pathogenesis remain largely unknown. Recent theories about the role of excessive mechanical load in the genesis of CT have been proposed. Driven by the interest for these new theories, we investigated the hypothesis of a relationship between work-related repetitive movements of the upper arm, considered a potential cause of shoulder overload, and the presence of shoulder CT. A secondary aim was to obtain data on CT prevalence in a female sample from the working-age general population, as little data currently exist. 199 supermarket cashiers and 304 female volunteers recruited from the general population underwent a high-resolution ultrasonography of the rotator cuffs of both shoulders, and the presence of tendinopathies, with or without calcification, was recorded. The prevalence of calcific tendinopathy was 22.6 % in the cashiers group and 24.4 % in the control group. There were no statistically significant differences in the prevalence of calcifications between the two groups (p = 0.585), either for the dominant shoulder [OR = 0.841 (95 % CI 0.534-1.326)] or for the non-dominant shoulder [OR = 0.988 (95 % CI 0.582-1.326)]. We observed bilateral calcifications in 8.5 % of cashiers, and 9.6 % of controls, and an increase in prevalence of CT with age in both groups. Work-related repetitive movements of the upper arm did not induce a higher prevalence of shoulder CT compared with the female sample from the general population. If CT etiopathogenesis is related to mechanical load, CT onset may be influenced not only by loading history, but also by individual factors. Level of evidence Prognosis study, Level II.