Rhizarthrosis in banknote processing workers: a retrospective cohort study.

Background: Rhizarthrosis, or osteoarthritis of the base of the thumb, is a common condition affecting 10-30% of the population over the age of 60. Whether it is an occupational disease has been the subject of debate as epidemiological studies on the correlation between physical stress and the presence of rhizarthrosis have shown conflicting results.

Aims: To study the correlation between the prevalence of rhizarthrosis and the time spent by employees manually processing banknotes at the National Bank of Belgium (NBB).

Methods: We followed NBB employees currently or previously holding job titles involving the manual or automated processing of banknotes. Each participant's job history was carefully reconstructed and the number of months holding certain job titles determined. Each participant was clinically and radiologically examined for the presence of rhizarthrosis in both hands. Its presence was scored by a combination of clinical and radiological criteria.

Results: There were 195 participants. The prevalence of rhizarthrosis was 27% in women (mean age: 52.3 ± 4.4 years) and 17% in men (mean age: 53.2). The odds ratio (OR) for rhizarthrosis after 10 years' full-time overall exposure was significantly higher [OR 10 years: 1.53 (1.03-2.28)]. However, one particular job, 'manual counting', described by participants as highly straining and severely taxing on the thumbs, did not show a significantly higher prevalence of rhizarthrosis.

Conclusions: Our study confirmed the correlation between the presence of rhizarthrosis and age, gender and general manual labour, in particular banknote processing, but found no link with one specific job-manual counting.