Northeastern's second version of an active knee rehabilitation orthotic device, dubbed AKROD, uses electro-rheological fluid to create a brake on the device. AKROD consists of two lightweight circular braces above and two below the knee, with the power-generating fluid brake--containing gears and sensors--resting alongside the knee.

An upcoming issue of the IEEE Transactions on Mechatronics reports on the Northeastern team's tests of the device on nine healthy patients. The subjects underwent standard stroke exercises and used AKROD as well. The researchers found that AKROD helped the subjects achieve comparable results to a bigger, commercial rehabilitation system called the Biodex System 3, which consists of a specially made chair, foot brace, and computer system.

A newer version of Northeastern's AKROD uses a NASA-inspired gear-based system instead of the special fluid. The gear-bearing drive lets the system lift a patient's leg to correct walking, rather than just apply resistive force. The device is still relatively small and light, due to a compact gearbox design. The device acts as if it has a virtual spring, say the researchers, using careful force to push the patient into the correct position.

The Northeastern team has also tested a rehabilitation device for the hand that's made of a gripper handle connected to sensors and gears. The device is driven by two actuators with the electro-rheological fluid, which increases or decreases its resistance as the patient uses the handle to navigate through a video game maze. The device exercises not only hand muscles but also forearm muscles, and records the force and position of the patient's hand. The researchers also created a version that can be used in an MRI to image the brain while a patient is undergoing the hand exercises. This could allow a doctor to see the effect of the exercise on a patient's brain, according to Mavroidis.

"We're so interested in this technology because it allows patients to perform repetitions of certain types of movements," says Paolo Bonato, Harvard Medical School assistant professor and director of the Motion Analysis Laboratory at the Spaulding Rehabilitation Hospital. Bonato collaborates with Mavroidis to test the devices with patients at the hospital. They are currently testing a small number of patients with the AKROD, pelvic, and hand devices, Mavroidis says.

"We can envision a home-care type of application where these devices are used by the patient in the home or the community," says Bonato.

The devices still need to go through clinical trials before they can be made available to the public.