Repetitive Strain Injury

Repetitive
Strain Injury

Stifling the Pain in a Pinch

Repetitive strain injury is the reason secretaries are wearing wrist splints and hairdressers are having hand surgery.

The injuries--which generally involve muscles and tendons pinching nerves in the neck, shoulder, elbow, wrist or hand--are the result of repetitive actions usually related to on-the-job activities such as typing and cutting. These motions frequently interfere with the body's normal movement, and they can cause chronic pain.

How common are these problems? In a series of studies by the National Institute for Occupational Safety and Health, researchers found that repetitive strain injury (RSI) occurred in as many as 40 percent of newspaper workers who work at computers. People who use keyboards or calculators, assemble small parts, cut fabric and package small items are at increased risk, as are welders, musicians and truck drivers.

The common denominator is that the jobs these workers do generally involve the execution of fine motor movements of the hands and arms at a pace that is not natural.

RSI is increasing at a rapid rate, experts agree. Possibly caused by the increasing number of jobs that require repetitive motions such as keyboarding, these injuries now account for 50 percent of all occupational illnesses reported in the United States.

The Tunnel of Pain

Of all the repetitive strain injuries that can occur, carpal tunnel syndrome is the most common in women. Smaller bone structure and hormones put women between the ages of 30 and 45 at twice the risk of men for this injury, experts say.

The carpal tunnel is just that--a tunnel that's formed by the carpal bones of the wrist and a ligament. Through the middle run nine tendons and the median nerve, a sensitive structure that provides feeling to the thumb, index finger, part of the middle finger and half of the ring finger.

Normally the nerve has plenty of room inside the carpal tunnel, and feeling and function in the hand are normal. But when the nerve gets pinched by swollen tendons as it passes through the tunnel, blood flow to the nerve is reduced, the nerve swells, and scar tissue begins to form. The result is the tingling, numbness, weakness and pain that lead to a diagnosis of carpal tunnel syndrome.

The major symptoms of carpal tunnel syndrome are pain and numbness that awaken you at night, although when the syndrome is severe, it can cause loss of grip strength and weakness in the hands that results in clumsiness. Half of all patients who get carpal tunnel syndrome eventually get it in both hands.

What's behind It

Carpal tunnel syndrome is believed to be caused by activities that involve repetitive upward and downward motions of the wrist and those in which the wrist is placed continually in a cocked or bent position. Upward and downward motions cause the tendons to become inflamed and swollen. A cocked or bent position narrows the carpal tunnel, compressing the median nerve.

Typing on a computer keyboard, working on an assembly line, cutting hair or keying on a calculator or cash register are the kinds of repetitive activities that can cause carpal tunnel syndrome. And so can home activities and hobbies such as kneading bread or knitting, says Karen Piegorsch, an ergonomist and clinical specialist in orthopedic physical therapy in Columbia, South Carolina. In a study conducted by researchers in Colorado, for example, 15.9 percent of 552 individuals visiting a doctor for the first time for carpal tunnel syndrome were homemakers.

Body size is also believed to play a role. Because the average woman's body is smaller than a man's, it may predispose her to carpal tunnel syndrome. Decreased carpal tunnel size (along with sex differences related to hormones) contribute to the development of the condition, says Richard Katz, M.D., medical director of SSM Rehabilitation Institute in St. Louis. The tendons and nerves in a woman's hand may be similar in size to those of a man, yet her bones, which support the hand, may be much smaller. This means they have less room in which to operate and are more in danger of becoming compressed, says Amy Ladd, M.D., a hand surgeon and assistant professor of functional restoration in the Division of Hand and Orthopedic Surgery at Stanford University School of Medicine.

A woman's smaller body size in relation to the large equipment and tools she operates at work may also make her more susceptible, says Piegorsch. That's because tools designed for a man may force her to work with equipment that is too high, too heavy or at the wrong angle.

What Hormones Can Do

Many women also develop carpal tunnel in the second and third trimesters of pregnancy because of hormonal changes, says Dr. Ladd. Studies indicate that between 2 and 25 percent of pregnant women have it. During pregnancy there is more fluid retention, and as the body swells, so do the structures in the carpal tunnel. Researchers believe that the change in the estrogen/progesterone balance may be responsible for fluid retention, says Dr. Ladd.

The hormonal shifts of menopause also put women at high risk for carpal tunnel syndrome, researchers say, as do birth control pills in women who retain fluid, says Dr. Ladd.

And premenstrual water retention may increase pain in women who have the syndrome, says Alan Bernstein, M.D., chief of neurology at the Kaiser Permanente Medical Center in Hayward, California. "Premenstrual swelling affects everywhere in the body," he says. "If tendons swell, it doesn't take a lot to pinch the nerve."

Having long fingernails is another factor. Often women with long nails who use keyboards a lot hold their fingers in an unnatural position, which places excess stress on their fingers and wrists, according to Piegorsch.

The syndrome can also plague women who have thyroid disease or rheumatoid arthritis--two diseases that cause swelling and affect more women than men.

Playing It Safe

Women may be more susceptible to carpal tunnel than men, but there are things you can do to lower your risks. Here's how.

Sit properly. When you sit at a keyboard, make sure your chair is adjusted properly. When sitting, your back should be well-supported and your feet should be flat on the floor. Your knees and hips should be bent to 90 degrees, and your shoulders should be over your hips.

Be especially aware of the angle of the keyboard and the height of the chair relative to the keyboard. When you're seated in a chair that's properly adjusted, your wrists can gently flex upward with no extreme bends in either direction, says Piegorsch. "The goal is to adjust your workstation to allow your body to be in a balanced posture," she says.

Warm up and stretch. If you're going to use part of your upper body repetitively, be sure to warm up and stretch, says Dr. Katz. For example, start with slow typing, then speed up later.

Take breaks. Rest periodically throughout the day. Change to a less repetitive activity or one that allows you to use a different set of muscles, says Piegorsch. A good plan is to take a 30-second break every half-hour to change positions or get up and move around.

Watch your neck and shoulders. Since the nerves and blood vessels that pass through the carpal tunnel originate in the neck and shoulder area, poor neck and shoulder posture can contribute to the development of carpal tunnel syndrome, says Piegorsch. Be aware of your posture while working in the kitchen, too. Counters are often too high for shorter women and cause them to hunch their shoulders while chopping and cutting, she says. If your counters are too high, work on a lower surface or stand on a low stool.

Trim your nails. Keep your nails at the length that allows you to type with the tips of your fingers in a natural position. That's probably less than an eighth of an inch.

Tackling the Hurt

If you're suffering from the pain of carpal tunnel, here are some coping mechanisms.

Change the way you work or play. If you're doing activities with a lot of repetitive wrist motions, try cutting back. A woman who types for a living might want to limit the amount of knitting she does after work, for example, while someone who uses a screw-gun on an assembly line might want to give hedge-clipping chores to another family member.

Also take a look at your workstation and see if it's right for you. For help, call the federally sponsored Job Accommodation Network at 1-800-526-7234. The people there can suggest ways to modify your work area to help deal with repetitive strain injuries and other disabilities.

Vie for vitamins. Vitamin B₆ may help reduce carpal tunnel pain, says Dr. Bernstein. Experts believe that B₆ helps increase serotonin, a chemical messenger in your brain that can decrease pain. But since vitamin B₆ can cause nerve damage in some people, he adds, check with your doctor about how much you should take before you try it.

See a health professional. When pain starts waking you up at night, it's time to see a doctor, says Dr. Bernstein. Find an orthopedic surgeon or neurologist who specializes in carpal tunnel syndrome. She might suggest a splint to keep your wrist in a neutral position. Night splints can be useful, says Dr. Bernstein, because we often flex our wrists while we sleep. Using splints on the job is often ineffective, however, since the patient may end up fighting against the splint, which may cause further injury to the wrist and lead to other problems such as tendinitis.

Consider surgery. If your wrist still hurts eight weeks after you've tried rest, stretching, splinting and new work habits, it might be time to talk to your doctor about surgery. Surgery can alleviate pain and prevent further injury to the nerve by literally dividing the carpal ligament that runs through your wrist, thus releasing the bear hug it's got on your median nerve. Once free, the nerve begins to recover and stops sending pain messages to your brain. The whole area can then get back to business.