To evaluate the risk factors of the carpal tunnel syndrome (CTS) and the impact of the wrist ratio on the prevalence of CTS in workers on repetitive work over a long term.

Study subjects consisted of 45 male and 16 female workers in a company that produces soundproof material in Gyeongju. We conducted a physical examination, a self-reported questionnaire survey and a nerve conduction study. CTS cases were defined as those subjects that had a positive finding in both the nerve conduction study and the physical examination done by a doctor specializing in rehabilitation medicine.

Prevalence of CTS among the study subjects was 26.2/100 persons. The prevalence of CTS was positively associated with increasing age (p<0.01, using the chi-square test for trend) and female gender (OR=6.98, 95% CI=1.66-31.0), but was negatively associated with the educational level (p<0.01 by the chi-square for trend). Workers in the production area had a higher prevalence of CTS compared to those in the clerical area (OR=10.8 in the frame manufacturing process, OR=32.2 in the vacuum molding process). Patients with CTS had a narrower mean wrist width and a shorter mean hand and palm length, compared to those that had no disease (p<0.01 by the Student's t-test). The number of subjects who had a wrist ratio of 0.74 or more was significantly higher in cases of CTS (OR=4.0, 95% CI=1.01-16.3). However, a multiple logistic regression analysis showed only that the type of work was a significant variable after adjusting for the other variables.

The wrist ratio, a surrogate of carpal tunnel configuration, can represent individual susceptibility to CTS. However this study shows that the use of the wrist ratio for predicting CTS risk is not adequate. The development of a new carpal tunnel configuration index based on more direct measurements of the tunnel shape will provide a better predictor of individual susceptibility to CTS.