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References & Links

National Institute of Occupational Safety and Health (NIOSH)
www.cdc.gov/niosh

Journal of the American Medical Association (JAMA)
jama.ama-assn.org

Carpal tunnel syndrome (CTS) is a compression neuropathy of the median nerve at the wrist, which causes pain, numbness, and tingling in the forearms, wrists, and fingers. It is a common problem treated by occupational medicine clinics. Patients with CTS frequently have questions about their condition. Important research over the last three years has helped clarify some of the answers to these questions.

Here are research-based answers to seven common patient questions.

"Did my job contribute to my getting CTS?"

In the July 1997 report of the National Institute of Occupational Safety and Health (NIOSH), a research panel examined over 30 epidemiologic studies of physical workplace factors and their relationship to CTS. From this evaluation, the NIOSH research panel concluded:

There is evidence of a positive association between highly repetitive work and CTS.

There is evidence of a positive association between forceful work and CTS.

There is evidence of a positive association between work involving hand/wrist vibration and CTS.

There is strong evidence of a positive association between exposure to a combination of risk factors (e.g., force and repetition, force and posture) and CTS.

An appropriate answer to a patient’s question on CTS and work-related risks would be: "If your job involves repetitive, forceful hand and wrist movement and exposure to vibration, it probably did contribute to the CTS."

"Could other things, not related to my job, affect my getting carpal tunnel syndrome?"

Atroshi and colleagues published the largest epidemiologic study on CTS to date, entitled "Prevalence of carpal tunnel syndrome in a general population" in the July 14, 1999 issue of the Journal of the American Medical Association (JAMA). In that study, they found that in addition to work-related risks, carpal tunnel syndrome:

occurs much more commonly in women

increases with age

is associated with obesity and other diseases (e.g., rheumatoid arthritis).

An appropriate answer would be: "There are many non-work related factors that contribute to getting CTS. Four factors are: being female, getting older, being overweight, and having rheumatoid arthritis."

"Do you really know all the things that contribute to carpal tunnel syndrome?"

One of the puzzles in carpal tunnel syndrome is that some workers who have abnormal nerve conduction studies develop the symptoms of carpal tunnel syndrome and some do not. Werner and colleagues published the study "Median mononeuropathy among active workers: are there differences between symptomatic and asymptomatic workers?" in the April 1998 issue of the American Journal of Industrial Medicine. They evaluated 184 workers with median neuropathy and concluded that most logistic regression models explained less than 15% of the variance between the group that had symptoms and the group that did not. Thus, 85% of the variance between groups could not be explained. In this circumstance, then, what we understand about the cause of CTS is less than what we don’t understand.

An appropriate answer therefore would be: "There is a lot about the cause of CTS we don’t know."

"Is carpal tunnel syndrome usually caused by tendonitis?"

Many occupational health providers assume that the cause of carpal tunnel syndrome is the inflammation and swelling of the tendons in the carpal tunnel, causing the nerve to become entrapped. Over the last decade, several studies have demonstrated that this hypothesis is rarely true. Here are two recent examples:

In a September 1999 study in the Journal of Bone and Joint Surgery [British] entitled "Work practices and histopathological changes in the tenosynovium and flexor retinaculum in carpal tunnel syndrome in women," Chell and colleagues studied 58 women with CTS. They concluded that "work practices do not affect tenosynovial thickening, fibrosis, or edema in patients with carpal tunnel syndrome."

In an October 1998 study in the Journal of Hand Surgery [American] entitled "Histology of the transverse carpal ligament and flexor tenosynovium in idiopathic carpal tunnel syndrome," Nakamichi and colleagues studied 130 patients with CTS. They concluded that in CTS "the ligament and tenosynovium often show normal histology and there are no typical or consistent changes with which idiopathic carpal tunnel syndrome can be associated."

In answer to a patient’s question, an appropriate response would be: "As a general rule, carpal tunnel syndrome is not caused by tendonitis."

"Will electrical studies accurately confirm whether I have carpal tunnel syndrome?"

In their 1999 JAMA study, Atroshi and colleagues found electro-diagnostic evidence of CTS in:

70% of the subjects diagnosed as having clinically certain CTS

46% of the subjects with paresthesias in the median nerve distribution in the hands

18% of the non-symptomatic control subjects.

An appropriate answer to a patient’s question would be: "If you appear to have CTS on examination, electro-diagnostic tests will confirm the diagnosis about 70% of the time."

"What is the chance that I will be very satisfied with my surgery?"

In many studies, the workers’ compensation carpal tunnel surgery patient group has poorer results than the non-workers’ compensation group. Consequently, providing workers’ compensation patients with non-workers’ compensation statistics is misleading. The Maine Carpal Tunnel Study evaluated patient-assessed outcomes of community-based surgery for patients on workers’ compensation. The study authored by Katz and colleagues appeared in the July 1998 Journal of Hand Surgery [American]. The study found that "[w]hile workers’ compensation recipients had worse outcomes than non-recipients, 36 of 68 (53%) of workers’ compensation recipients were completely or very satisfied with the results of the procedure 30 months after surgery."

An appropriate answer to a patient’s question would be: "You’ll be very satisfied or completely satisfied with your carpal tunnel surgical results a little better than 50% of the time."

"Which surgery gives better long-term results for carpal tunnel release: endoscopic or open?"

Endoscopic carpal tunnel release surgery has been available long enough to compare its long-term effects to the older, open technique. The Maine Carpal Tunnel Study performed such a comparison and concluded: "There were no significant differences in outcome between patients treated with endoscopic versus open carpal tunnel release." Although studies have shown that endoscopic release may have advantages, particularly in the immediate post-operative period, most studies agree with the Maine study in finding it offers long-term outcomes similar to the older, open procedure.

An appropriate answer to a patient’s question about the comparison of surgical techniques would be: "The long-term results of endoscopic and open carpal tunnel release surgery are about the same."