Carpal tunnel syndrome
A problem in both the factory and the office
Carpal tunnel syndrome (CTS), a musculoskeletal disorder, is the compression of the median nerve at the wrist, which can cause numbness, tingling, weakness, or muscle atrophy in the hand and fingers. CTS affects both white- and blue-collar workers.
How CTS Occurs
Eight bones in the wrist, called carpals, form a tunnel-like structure filled with flexor tendons that control finger movement. This tunnel also provides a conduit for the median nerve to reach sensory cells in the hand. Repeatedly flexing and extending the wrist can cause the protective sheaths that surround each tendon to thicken. Thickened tendons exert increased pressure on the median nerve, causing CTS.
Some studies suggest that CTS primarily is associated with medical or physical conditions that put workers at risk, such as diabetes, osteoarthritis, hypothyroidism, and rheumatoid arthritis. It also generally tends to occur in people with certain genetic or environmental risk factors, such as obesity, smoking, alcohol abuse, or significant mental stress.
Workers, especially at-risk workers, who perform tasks that involve highly repetitive manual acts and stressful wrist postures are likely candidates for CTS, particularly when working in cold-temperature, high-force, high-vibration conditions and when frequent rest is impossible.
According to the Bureau of Labor Statistics (BLS), CTS is more severe than the average workplace nonfatal injury or illness case. In 2001 CTS cases involved on average 25 days away from work compared with six days for all nonfatal injury and illness cases. The BLS reported 26,794 CTS cases involving days away from work in 2001. Seventy percent of these cases fell into one of two occupational groups: operators, fabricators, and laborers (36.7 percent, or 9,808 cases); and technical, sales, and administrative support (34.2 percent, or 9,144 cases).
Although cases throughout all sectors declined from 1992 to 2001, CTS continues to be a problem in the workplace. In April 2002 the Occupational Safety and Health Administration (OSHA) unveiled a comprehensive plan designed to reduce ergonomic injuries through a combination of industry-targeted guidelines, tough enforcement measures, workplace outreach, advanced research, and dedicated efforts to protect Hispanic and other immigrant workers. In 2003 the agency released guidelines for nursing home employees and in 2004 for retail grocery store and poultry processing employees. In process are guidelines for shipyard and construction workers.
In the Office
Many office workers who spend their days pounding a computer keyboard experience CTS symptoms, as well as other musculoskeletal disorders caused by poor posture and ergonomically challenged equipment.
According to a report about CTSon about.com, the tendency to roll the shoulders forward, round the lower back, and thrust the chin forward can shorten the neck and shoulder muscles, compressing nerves in the neck. This, in turn, can affect the wrist, fingers, and hand. People with poor posture also may have physical abnormalities that increase the risk for CTS.
Studies indicate that workplace psychosocial factors, such as intense deadlines, a poor social work environment, and low levels of job satisfaction, are major contributors to carpal tunnel pain. Such psychosocial conditions are more likely to be important factors in contributing to CTS in office workers, although they also complicate the condition in workers whose work primarily is physical.
In the Factory
Factory workers often perform repetitive tasks that strain the musculoskeletal system—often under high-force, high-vibration conditions. An example can be found in an OSHA ErgoFact publication that describes how a punch press operation created undue ergonomic stress.
Three recognized ergonomics risk factors (stressors)—repetitive motions, awkward postures, and forceful exertions—were present in one operation used by a metal parts manufacturer.
The job required the operator to feed small metal parts simultaneously into a punch press. The parts were supplied to the press by two slide conveyors, which approached the operator from the rear and stopped approximately 2.5 feet from the press. The operator would reach forward to place the parts in the press and finally raise both hands up to the top of the press to actuate two palm buttons. Upon the operation's completion, the finished parts were ejected out the press's back side and the cycle repeated throughout the work shift.
The operator experienced moderate pain at the wrists, hands, and fingers and severe pain at the shoulders, and made regular requests to be removed from the job. The employer conducted an ergonomic analysis of the work methods and workstation by videotaping the operation and interviewing the operator.
Motion analysis noted that the task required simultaneous extended reach behind the operator's back, blind groping for and grasping of the conveyed parts, moving them approximately 4 ft. to the press, precisely placing them in the press, then reaching above head height to actuate the press with the two palm buttons. The operator then brought his arms down rapidly to the conveyors behind him as the cycle repeated.
Analysis of the punch press operation resulted in three primary workstation changes (see Figure 1).
Workstation Reconfiguration; Image courtesy of OSHA.
First, the conveyors were extended in length to end closer to the press and just forward of the operator. This allowed the operator to reach down in his field of view and easily grasp the metal parts. Hinges and handles were installed on these extensions to allow easy access to and from the workstation.
The second change was to install a platform to elevate the worker and give him easier access to the press, which then brought it to just below chest height.
Finally, the two overhead palm buttons were replaced by light beam actuators. This redesign reduced reach distances, reach heights, grasping problems, hand forces, overall fatigue, and joint stress points, as well as cycle time. The cost of fabricating and installing the conveyor extensions and light actuators was approximately $700.
According to a fact sheetfrom the National Institute of Neurological Disorders and Stroke (NINDS), symptoms usually start gradually, with frequent burning, tingling, or itching numbness in the palm of the hand and the fingers, especially the thumb and the index and middle fingers. Some sufferers say their fingers feel useless and swollen, even though little or no swelling is apparent.
The symptoms often first appear in one or both hands during the night, since many people sleep with flexed wrists. A person with CTS may wake up feeling the need to shake out the hand or wrist. As symptoms worsen, people might feel tingling during the day.
Decreased grip strength may make it difficult to form a fist, grasp small objects, or perform other manual tasks. In chronic and/or untreated cases, the muscles at the base of the thumb may waste away. Some people are unable to tell between hot and cold by touch.
Diagnosis and Treatment
Early diagnosis and treatment are important to prevent permanent damage to the median nerve. Physically examining the hands, arms, shoulders, and neck can help a physician determine if the patient's complaints are related to daily activities or to an underlying disorder, and it can rule out other painful conditions that mimic carpal tunnel syndrome. Physicians can use specific tests to try to produce the CTS symptoms.
NINDS recommends beginning treatments for CTS as early as possible, under a doctor's direction. Underlying causes such as diabetes or arthritis should be treated first. Initial treatment generally involves resting the affected hand and wrist for at least two weeks, avoiding activities that may worsen symptoms, and immobilizing the wrist in a splint to avoid further damage from twisting or bending. If there is inflammation, applying cool packs can help reduce swelling.
Depending on the circumstances, the doctor may prescribe drugs to help ease the pain and swelling associated with CTS. Nonsurgical treatments and nonsteroidal antiinflammatory drugs such as aspirin, ibuprofen, and other nonprescription pain relievers may ease symptoms that have been present for a short time or have been caused by strenuous activity. Orally administered diuretics (water pills) can decrease swelling.
Corticosteroids (such as prednisone) or the drug lidocaine can be injected directly into the wrist or taken by mouth (in the case of prednisone) to relieve pressure on the median nerve and provide immediate, temporary relief to persons with mild or intermittent symptoms. These drugs can have serious side effects and should not be taken without a doctor's prescription.
Additionally, some studies show that vitamin B6 (pyridoxine) supplements may ease the symptoms of CTS.
Stretching and strengthening exercises can be helpful in people whose symptoms have abated. These exercises may be supervised by a physical therapist trained to use exercises to treat physical impairments, or an occupational therapist trained in evaluating people with physical impairments and helping them build skills to improve their health and well-being.
Alternative therapies can help. Acupuncture and chiropractic care have benefited some patients, but their effectiveness remains unproved. Yoga has been shown to reduce pain and improve grip strength among patients with CTS.
Generally recommended if symptoms last for six months, carpal tunnel release surgery, among the most common surgical procedures in the U.S., involves severing the band of tissue around the wrist to reduce pressure on the median nerve. Surgery is done under local anesthesia and does not require an overnight hospital stay. Many patients require surgery on both hands.
Although symptoms may be relieved immediately after surgery, full recovery from CTS surgery can take months. Some patients may have infection, nerve damage, stiffness, and pain at the scar. Occasionally the wrist loses strength because the carpal ligament is cut. Patients should undergo physical therapy after surgery to restore wrist strength. Some patients may need to adjust job duties or even change jobs after recovery from surgery.
CTS recurrence following treatment is rare. The majority of patients recover completely.
Ideally, employers will make every effort to prevent job-related CTS by developing ergonomic programs that adapt workplace conditions and job demands to the workers' capabilities. Workstations, tools and tool handles, and tasks can be redesigned to enable the worker's wrist to maintain a natural position during work. Jobs can be rotated among workers. However, research has not shown conclusively that these workplace changes prevent CTS.
Regardless of how much the employer does to improve ergonomics, workers should practice on-the-job conditioning, perform stretching exercises, take frequent rest breaks, wear splints to keep wrists straight if necessary, and use correct posture and wrist position. Wearing fingerless gloves can help keep hands warm and flexible.