By Ellen Rader Smith, MA, OTR, CVE, CPE
Carpal tunnel syndrome (CTS) is one of the more familiar cumulative trauma disorders (CTDs) or repetitive strain injuries. Reported cases of occupational CTS are most common in the manufacturing sector (see Figure 1), but occur throughout industry, in office environments, and among the general population. But what is carpal tunnel syndrome, and what causes it? CTS is the result of compression or irritation of the median nerve as it passes through the carpal tunnel in the wrist. The median and ulnar nerves and flexor tendons are among the structures that pass through this narrow tunnel. CTS symptoms include pain, numbness (of the thumb and index, middle, and half the ring fingers), a loss of grip or pinch strength, and decreased coordination. Physicians diagnose CTS based on the patient's subjective complaints (which often begin with those of nocturnal numbness), objective findings based on physical examination and diagnostic tests that can reproduce compression on the median nerve, and electrodiagnostic studies that include nerve conduction velocity tests and electromyograms. At present, the latter is considered to be the most accurate test for nerve compression. Less invasive nerve tests exist and are often used by occupational health clinicians. Epidemiologists who study musculoskeletal injury trends in the workplace, such as those at the National Institute for Occupational Safety and Health (NIOSH), have developed a surveillance case definition for establishing work-related cases of CTS among state-based programs. What causes compression on the median nerve? Repetitive wrist movements, forceful gripping, contact pressure over the carpal tunnel, maintaining a pinch grip with a flexed wrist, and using vibratory tools, or any combination of these conditions are occupational CTS risk factors. These repeated motions and forceful exertions are very common in the performance of daily work tasks, homemaking, and even child care. Not everyone who performs these movements gets CTS. Some people, such as those who have diabetes or rheumatoid arthritis, are more likely to develop CTS in comparison to persons performing the same work tasks who do not have these medical conditions. Pregnant women may experience a transient CTS that subsides after delivery. However, a new mother who maintains a flexed wrist posture while feeding or holding her baby may be prone to CTS.
Figure 1. Number (thousands) and distribution of repeated trauma disorders in private industry by industry division, 1997 (Source: SOII, 1999).
