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Warning: your job may be hazardous to your hands.


Ever since early man struck two stones together to start a fire, people have been at risk for developing problems that come with rigorous and repetitive motions of the hands and wrists.

Commonly called cumulative trauma disorders, overuse syndromes or repetitive motion injuries, these problems have become increasingly common in today's mechanized work place. If you're a computer programmer, an assembly line worker or a word processor, you may be at risk for one of these painful and sometimes debilitating conditions.

"The National Institute of Occupational Health and Safety estimates that, at any given time, 15 to 20 percent of the work force is at risk for cumulative trauma disorder," says Dr. Dean S. Louis, professor of surgery and director of the orthopaedic hand surgery clinic at the University of Michigan.

Tenosynovitis, or inflammation of the linings of the tendons -- bands of dense fibrous tissue that connect muscle to bone -- and synovitis, or inflammation of the joint lining, are two common results of overuse. But perhaps the most common cumulative trauma disorder, says Dr. Louis, is carpal tunnel syndrome (CTS), a condition that occurs in the wrist and can lead to diminished hand function.

Causes and Effects

Also referred to as nerve entrapment injury, CTS is caused by the compression of the median nerve, which runs down the arm to the thumb and two middle fingers. To reach the hand, the median nerve must pass through a tunnel on the underside of the wrist formed by a tight, fibrous band of connective tissue. The tendons from the forearm muscles also pass through this tunnel. Since these structures fill this tunnel to capacity, any swelling inside the carpal tunnel puts pressure on the nerve, causing tingling, pain, numbness or loss of grip strength in the hand.

Although the disorder can occur with pregnancy, arthritis or any other condition that would cause the wrist to swell, it is most common in people who work with their hands.

Unlike CTS, tenosynovitis can occur in any area of the body, but it most frequently affects the hands, according to Dr. Louis. Synovitis, too, can occur in any joint that is overused, but it presents a particular hazard to the hands -- primarily the thumb joints.

The biggest danger of synovitis is that it can lead to arthritis, according to Dr. Harold M. Dick, chairman of the Department of Orthopaedic Surgery at Columbia Presbyterian Medical Center. "When the joint lining becomes inflamed, the blood vessels within that lining also become inflamed," he explains. "This causes damage to the cartilage surface and, over long duration, destruction of the cartilage."

Who's at Risk?

"In a recent study of 652 factory workers, researchers at the University of Michigan's Center for Urban Studies found that cumulative trauma disorders were most common in workers required to perform highly repetitive and highly forceful tasks with their hands," Dr. Louis says. Use of awkward hand positions and working with vibrating machinery were other key risk factors.

"When small injuries occur constantly over a period of time, the body loses its ability to recover, leading to these disorders" he continues.

Manual labor isn't the only type of work that can cause repeated small injuries of the tendons and joints. Dr. Louis and other orthopaedic surgeons are seeing an increasing number of CTS cases in people who work with computers and word processors. The reason, Dr. Louis suspects, is that computer or video display terminal use is constant in nature. "Now that we're no longer using typewriters, there's no need to stop and return the carriage, shift the paper or manually change margins -- we just keep going," he explains. "The same is true for data entry processors."

Professional athletes, who constantly use their muscles and joints -- to hit, throw or catch a ball, or to grip a racquet or bat -- also frequently develop the disorders.

Prevention and Treatment

A variety of factors can contribute to these disorders. In rare instances, for example, a tumor or cyst in the carpal tunnel may cause CTS. Therefore, it is important to see a doctor to determine the true cause -- and thus the best treatment.

"Treatment may include rest, nonsteroidal anti-inflammatory drugs and use of splints," says Dr. Dick. For carpal tunnel syndrome, injections of steroids into the wrist are often effective, adds Dr. Louis.

The best treatment for the disorders, however, is to eliminate the activity that caused the problem originally, the doctors agree. For most people however, eliminating a potentially harmful activity -- particularly when performing that activity is how they earn their living -- is easier said than done, Dr. Louis points out.

"People who work on assembly lines are usually getting a great deal of money for their work. And in most industries their skills aren't easily transferable to another job. You can't just go from using a punch press to shuffling papers."

In some cases, modifying -- not quitting -- an activity can help, but that too is difficult, Dr. Louis says. "Ergonomic interventions -- equipment designs that reduce operator fatigue and discomfort -- have shown to be highly effective, if you have a management team that is willing to make these kinds of changes. Modification of the machinery is certainly the obvious thing to do, but frequently it is not possible because of the expense involved."

For businesses that traditionally have been reluctant or unable to change machinery or working conditions because of the high cost, a rising number of workers' compensation claims and decreased productivity are causing some organizations to rethink their stances.

The meat packing industry -- where assembly line workers must constantly use knives to cut meat -- found a relatively simple solution to help alleviate the problem of cumulative disorders in its workers, according to a report in a recent issue of Health Sciences Review. Knives were redesigned with thicker, easier-to-hold handles that eliminate the awkward hand positioning required to grip the earlier models.

For people working at computer keyboards, the solution may be even simpler: adjusting their chairs and desks so they don't have to hold their hands at awkward angles to type.

In some cases, just incorporating rest periods into the workday can suffice. Resting doesn't have to mean being unproductive. For example, if you've spent a few straight hours typing on your computer keyboard, shift your attention to reading correspondence or filing papers, Dr. Louis says.

Also, changing or modifying your leisure activities can protect your hands. Injuries incurred while weeding the garden, picking a banjo, chopping vegetables or gripping a tennis racquet or ski pole can be exacerbated by repetitive motions on the job.

Ongoing scientific research will likely provide more clues as to how to prevent the disorders. For example, Dr. Kenneth D. Brandt and his colleagues at the Indiana University Multipurpose Arthritis and Musculoskeletal Diseases Center in Indianapolis are using a computerized electronic piano to study various finger techniques used by healthy musicians. The specially designed piano allows the researchers to measure the amount of force applied to the fingertips during playing. Applying this information, they developed a mathematical model of optimal finger positions that would minimize the tensions in tendons and stresses on joints during piano playing. According to the researchers, information gained from this type of analysis may be applied to prevention and treatment of a variety of performance-related hand problems in musicians, as well as in assembly line workers and others whose jobs require intensive hand motion.

Dr. Dick expects major advances in prevention and treatment of these disorders to come from the sports medicine field. Because cumulative trauma disorders often appear in professional athletes, impairing their ability to perform on the playing field or the court, team physicians are searching for the best ways to protect their valuable players.

When All Else Fails

When conservative treatments fail, surgery may be effective. For carpal tunnel syndrome, an orthopaedic surgeon opens the base of the palm and cuts loose any tissue pressing on the median nerve.

But many surgeons, including Dr. Louis, won't perform the surgery on people who plan to return to the work that caused the problem. Tendon lining can again become inflamed enough to refill the enlarged opening, necessitating additional surgery, Dr. Louis explains. And while first surgeries are generally successful, subsequent surgeries have a much lower success rate, he says.

Dr. Louis adds that while surgery is rarely indicated for tenosynovitis or synovitis, when a joint becomes irreparably damaged by synovitis joint replacement may be needed.

Protect Yourself

While most cases of cumulative trauma disorders can be treated effectively, injuries allowed to progress too far may be impossible to correct and, in rare cases, may lead to permanent loss of hand function. For that reason, it's best to avoid the problems if you can (see below for specific suggestions on how you can lower your risk) and if you do begin to notice problems, consult your doctor immediately.

Helping Hands

* Take frequent rest breaks when you're using your hands. If that's not possible, try to alternate between duties that require repetitive hand motion and those that don't. For example, take a break from typing and do some filing.

* When typing on a computer keyboard, avoid bending your wrists or resting your hands on the keyboard and flexing your fingers to reach the keys. Adjust your chair to a comfortable height that enables you to reach the keys without awkward stretching.

* When working with your hands in cold weather, avoid wearing heavy gloves, which can interfere with finger motions and actually put more stress on joints. Thin or fingerless gloves are better choices.

* When purchasing hand tools, look for models with large, easy-to-grip handles and/or curved handles that enable you to use the tools without bending your wrists.

* If you enjoy sports, combine a variety that require use of different muscles and joints. For example, if you spend every weekend playing racquetball, try jogging for a change of pace and give your arms and hands a rest.

* Be aware that your leisure activities can add to joint and tendon damage received on the job. If you're already using your hands constantly to perform your job, try to limit other activities -- such as playing the piano or pulling weeds -- that would put stress on the same joints.

* See a doctor if you notice pain and swelling in the joints and muscles of your hands and arms or tingling or loss of sensation in your hands.
COPYRIGHT 1990 Arthritis Foundation, Inc.
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Author:Dunkin, Mary Anne
Publication:Arthritis Today
Date:Sep 1, 1990
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