Purdue News

Research may help workers avoid carpal tunnel syndrome

NOTE TO JOURNALISTS: An abstract of the Purdue study is available from Amanda Siegfried, Purdue News Service, (765) 494-4709.

WEST LAFAYETTE, Ind. -- Purdue University researchers are lending a helping hand to the thousands of people who may be at risk of developing carpal tunnel syndrome.

In a recent study, researchers developed a model that can predict the odds of an individual acquiring carpal tunnel syndrome, a cumulative disorder of the hand and wrist and one of the most common disabling injuries in people who use computer keyboards.

The model is based on more than 60 factors, including the time spent working at a keyboard, posture, wrist position and wrist size. "It's similar to giving someone a cholesterol screening test and being able to determine how much at risk that person is for heart disease," says Gavriel Salvendy, the NEC Professor of Industrial Engineering. His former graduate student, Aura Matias, collected the data and developed the model for her doctoral dissertation. She now resides in the Philippines.

"Other assessment models typically describe a person's condition, often after they have already acquired carpal tunnel syndrome or are beyond treatment," Salvendy says. "This model can be used to assess people's risk before they acquire the problem."

According to the Purdue study, the risk factor contributing most to developing carpal tunnel syndrome is the amount of time spent using the keyboard, Salvendy says. "We knew that increased duration was bad, but we didn't know quantitatively how much damage is done," he says.

For example, increasing the duration of keyboard work from 15 minutes a day to four hours a day increases a person's probability of acquiring the syndrome from about 30 percent to more than 90 percent. Factors such as the length of an individual's arms, age, height and weight contributed least to the development of the syndrome. Other contributing risk factors include:

• Trunk angle -- Instead of sitting straight up, which increases a person's risk by about 60 percent, the study suggests that leaning back at a 25 degree angle, with back straight, decreases your risk factor to less than 10 percent.
  
• Wrist position -- Typing with the wrist bent upwards by about 80 degrees from the arm increases your risk to 90 percent, while keeping it in line with the rest of the arm carries only a 10 percent risk factor.

"Now that we know these risk factors, we can tell people what needs to be changed to reduce the likelihood of their getting carpal tunnel syndrome," Salvendy says. For example, to reduce the duration factor, Salvendy suggests that office workers rotate between jobs such as typing and copying.

Matias' model was based on a study of 100 female office workers who used computer keyboards without a mouse. Forty-five subjects had medically documented cases of carpal tunnel syndrome, while 55 did not.

CONTACT: Salvendy, (765) 494-5426; e-mail, salvendy@ecn.purdue.edu

Purdue News Service: (765) 494-2096; e-mail, purduenews@purdue.edu

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