Low-cost, Portable Arm Rehabilitation Robot for Cerebral Palsy Designed

A low-cost, portable robot for arm motor rehabilitation has been developed by University of Michigan researchers. The device can be used at home and facilitates motor recovery in patients with cerebral palsy, stroke, and spinal cord injury.

The study, “A Portable Passive Rehabilitation Robot for Upper-Extremity Functional Resistance Training,” was published in the journal IEEE Transactions on Biomedical Engineering.

Individuals with neurological damage, such as stroke or cerebral palsy, are commonly affected by loss of limb function that results from a reduction in muscle strength and mobility.

This loss of motor skills and movement capacity can greatly affect patients’ quality of life and limit their autonomy.

There is currently an increased demand for caregivers and rehabilitation services — a critical factor for recovery from neurological injuries — with insurance companies often reducing the time a person can stay on therapy.

This increases the need for alternative therapeutic approaches that improve muscle strength and movement control in a cost-efficient manner.

The interest in rehabilitation robotics has grown steadily because they can effectively deliver training and potentially compensate the higher demand for care. Rehabilitation robots can also automate, standardize, and ensure longer treatments.

But existing robotic devices able to assist in motor rehabilitation are typically too large, bulky, and expensive to be routinely used in the clinic or at home.

To overcome many of these limitations, researchers propose a novel rehabilitation robot for the arm — named PaRRo — that increases the functional capabilities of current devices.

The robot contains an effector at the end of a robotic arm, designed to be maneuvered by the patient. This effector is connected to a system of brakes that offer resistance to the arm’s movement, training muscle strength and improving arm resistance.

The device was designed to contain a wide range of scalable resistances to adapt to each patient’s abilities. This means that arm exercise intensities can be adapted to each patient’s motor skills. 

However, the robot is passive, which means it does not have any computer control, nor does it actively operate by taking over from the user.

PaRRo was designed to provide task-specific training. Evidence suggests that treatments which incorporate repetitive practice are more effective to improve functional outcomes.

Researchers chose low-cost and light materials to allow the robot to be portable and more accessible for in-home use by patients.

A large reachable workspace was also designed to enable training on a wide array of functionally relevant reaching tasks.

This device guarantees safety as it uses a special type of brake for generating a resistive force that opposes the user’s movement.

Researchers performed simulations to calculate the robot’s resistive force and workspace. They then constructed a prototype device based on these results.

The prototype was tested in a healthy male volunteer with no neurological or orthopedic impairments. Nine surface electrodes were placed in different muscles, whose activity was recorded by electromyography, a technique that evaluates the electrical activity in skeletal muscles to assess the health of muscle and motor neurons.

Both the force generated by the robot and the force produced by the user matched those predicted by the simulations when the device was moved across different directions.

Electromyography results also revealed the robot was capable of generating resistive forces adjustable to the subjects’ motor abilities.

“These results indicate that PaRRo is a feasible low-cost approach to provide functional resistance training to the muscles of the upper-extremity,” researchers wrote.

“The proposed robotic device could provide a technological breakthrough that will make rehabilitation robots accessible for small outpatient rehabilitation centers and in-home therapy,” they added.