Hand-in-Glove Relief for Carpal Tunnel Syndrome

A new soft robotic sleeve that gently straightens the wrist could help many of the six million Americans with carpal tunnel syndrome heal faster, and keep them healthy, productive, and pain-free.

One in 20 working Americans suffer from carpal tunnel syndrome, and for them pain-free hands are but a memory. Inflammation of the carpal tunnel ligaments sensitizes the median nerve, which runs from the wrist to the fingers, and their palm, thumb and index and middle fingers can tingle, burn, itch or go numb. When they type, as so many do on the job these days, some bend their wrists at awkward angles, which can exacerbate the problem.

Doctors often recommend a splint, which keeps people from using their hands normally, or, in severe cases, carpal tunnel surgery. This surgery costs more than $5,000, and 500,000 such procedures are performed each year in the United States, with an annual health care cost of $2.6 billion.

Enter the wrist-assist, a soft robotic sleeve that detects when its wearer flexes her wrist awkwardly, and responds by inflating a balloon actuator to nudge the hand to remove the strain.

“The idea was, How do you allow the hand to be mobile when needed and in a neutral position while typing?” said Wade Adams, an undergraduate engineer at Arizona State University’s Polytechnic School. 

He and Mengjia Zhu, an engineering master’s student, and Panagiotis Polygerinos, a mechanical engineer and assistant professor at the university, set out to solve the problem by creating a breathable device that was washable, breathable, and easy to don and doff.

They built a sleeve-like device that looks like a long, black, high-tech fingerless glove.

The sleeve uses an inertial measurement unit (IMU) to measure the angle of the wrist no matter how the user is holding his arm in three-dimensional space. The IMU, which contains a magnetometer and an accelerator, sits in the device on the top of the hand. Meanwhile, pressure sensors detect air pressure in the two balloon actuators.

All three sensors feed data into a microcontroller, which decides whether the wrist is bent more than 5 degrees out of the plane – an angle awkward enough to cause strain. At that point, the controller signals a micro air pump to inflate two thermoplastic balloon actuators, one on top of the wrist and one underneath, to an air pressure of 60 kPa.

“We wanted to help people when typing to keep their wrist in a neutral position,” Adams said.

The engineers tested their device by showing it can straighten when a 250-gram weight is attached, and they’re initiating tests on human subjects to get feedback. But Adams himself has tried it.

“It feels like you’re wearing a glove that extends. There’s a natural inclination to move the hand to neutral,” he said.

In March, the engineers obtained a provisional patent on their device.

The electronics, battery, bladder and sleeve, air pump and valves are all inexpensive, and the engineers estimate it would cost $76 to build, Adams said. They foresee manufacturing an FDA-regulated device that doctors would prescribe for carpal tunnel rehabilitation, as well as a preventive device for all computer users that they’d sell through retail outlets and to computing centers as an ergonomic device to prevent damage.

If they succeed, a few years from now you may be slipping on a pair of ergonomic gloves before you even check your email.