More power to your elbow

An experimental robotic device that provides a ‘power assist’ to weakened muscles has shown promising results in improving arm motion in partially paralysed stroke survivors.

The MIT Active Joint Brace (AJB) was tested on stroke patients at MIT’s Clinical Research Center and at Spaulding Rehabilitation Hospital in Boston. According to the researchers, the results show that the ability of the device to provide a ‘power assist’ to muscle groups may help close the feedback loop of brain intention and actual limb movement that is believed to be a key component of cerebral plasticity in motor recovery.

Exoskeletal robots can, in principle, provide therapeutic exercise and/or function as powered orthoses to help compensate for chronic weakness.

The wearable, portable neurorobotic device combines a lightweight, motorised elbow brace with a computerised system that detects electrical impulses (electromyographic, or ‘EMG,’ signals) from the muscles. The device allows a patient to control affected muscles by attempting to move the arm. The system detects and then processes the EMG signals and translates them into the desired motion, amplifying the movements of the weakened muscles.

Lead researcher Dr. Stein and colleagues performed an initial feasibility study of the AJB in seven stroke survivors with severe weakness and reduced use of one arm. All patients were able to successfully control the robotic AJB to help them flex and extend the elbow.

The study showed that patients made significant gains in arm function while not wearing the device. Average score on a standard test of arm movement increased by 23 per cent. Scores for muscle spasticity (stiffness) were also improved. There were no complications. Most patients said they enjoyed learning to use the AJB and felt they gained meaningful improvement in elbow control and use of the arm.

The researchers envision two possible therapeutic uses for the AJB. As in the pilot study, it could be used as an aid to exercise training, either to improve muscle control or to build strength. It might also be used as a powered brace to provide assistance with everyday tasks in patients with chronic weakness or paralysis, such as that caused by spinal cord injuries. More study will be needed to address these issues, along with further development to make the AJB more portable, user-friendly, and comfortable.