Relationship between carpal tunnel syndrome and wrist angle in computer workers.

Carpal tunnel syndrome (CTS) is the most widely known entrapment neuropathy. The aim of this study was to assess the incidence of CTS in a group of computer workers by typical symptoms, median nerve conduction studies, and their combinations. The posture of extended wrists while typing on a computer keyboard seems to be a predisposing factor for CTS. However, the correlation between wrist extension angle and the incidence of CTS is not well known. Forty-five subjects (mean age, 38.8 +/- 7.8 years) who used a computer for more than 6 hours daily in a medical center in southern Taiwan were studied. All completed questionnaires to ascertain their age, employment duration, dominant hand, and the severity of symptoms. Physical examinations (Tinel's sign and Phalen's test) were performed by a physician. The maximal wrist extension angle when typing on a computer keyboard was also measured by the same physician. Nerve conduction studies were performed on each subject to determine the severity of CTS. Results showed that the incidence of CTS in the computer workers was 16.7% (15 of 90 hands). Twelve subjects showed electrodiagnostic evidence of CTS: it involved the dominant hand in seven, the non-dominant hand in two, and bilateral hands in three. The severity of clinical symptoms was compatible with the findings of the nerve conduction studies. Among the major predisposing factors, we found significant correlation between CTS development and the wrist extension angle while typing on a computer keyboard. Computer workers who kept their wrists extended by more than 20 degrees were at greater risk of developing CTS.