This study was conducted to evaluate individual susceptibility to carpal tunnel syndrome (CTS) by ultrasonographic measurement of the carpal tunnel configuration in workers doing repetitive work.

The study subjects consisted of 24 male and 11 female workers in a soundproof material manufacturing company in Gyeongju. We conducted a self-reported questionnaire survey, a physical examination and an electrodiagnostic study (EDS) in April 2000. After the examination, jobs were rearranged for workers with CTS. A follow up physical examination, EDS, and measurement of the carpal tunnel by ultrasonography was done six months later.

Of those studied, prevalence of CTS was 63.6/100 persons among women and 29.2/100 persons among men. Mean depth and width of wrist was shorter in those with CTS compareal to the controls (p<0.05). The risk of CTS was higher in workers whose carpal tunnel ratio (displacement/width) was 0.17 or higher (OR 7.13, 95 % confidence interval 1.18-43.1), and in workers whose carpal tunnel area was less than 300 mm2 (OR 8.00, 95 % confidence interval 1.18-68.5). Carpal tunnel depth and depth/width ratio had a positive correlation with motor latency of the median nerve and median-ulnar sensory latency difference (p<0.05), whereas the carpal tunnel width, displacement/depth ratio, and area (width X displacement) had a negative correlation with median nerve latencies after adjusting for gender. Workers who showed an improvement in the clinical stage of CTS after job rearrangement had a significantly lower carpal tunnel displacement/width ratio and displacement/depth ratio. They also had smaller upper carpal tunnel area ( width X displacement) and larger upper carpal tunnel area [(depth-displacement) X width] than the controls (p< 0.05 ).

Ultrasonographic measurement of the carpal tunnel is a good predictor of susceptibility and prognosis of CTS in workers doing repetivive work.