Powered Orthosis May Help Hemiparetic Patients Regain Motion

A robotic exercise orthosis improved arm motion in severely impaired hemiparetic stroke survivors. Joel Stein, MD, chief medical officer of the Spaulding Rehabilitation Hospital, and colleagues at the Massachusetts Institute of Technology, conducted a pilot clinical study with a novel device, the active joint brace (AJB), which combines an exoskeletal robotic brace with electromyography (EMG) control. The AJB is a noninvasive, lightweight system that uses surface EMG signals from affected muscle groups to control a powered orthosis, according to a report published in the American Journal of Physical Medicine and Rehabilitation.

“[The brace] picks up the electrical activity in the patient’s own muscle, and uses that to control a powered brace and essentially provides what could be described as a ‘powered assist,’” Stein told O&P Business News. “The person decides what movement they want to make, whether they want to bend or extend the elbow, and the device senses their attempt as they try to do that and gives them help as they do it.”

Pilot study

Man using robotic exercise orthosis
Image reprinted with permission of Myomo Inc.

The investigators developed a pilot study that included eight patients who had chronic weakness for at least 6 months after a stroke. To be included, patients had to have weakness and loss of motor control that interfered with functional upper extremity use. Patients with ischemic and hemorrhagic stroke were enrolled, the authors wrote. Before they could begin the study, patients had to have completed formal physical and occupational therapy. The investigators asked participants to avoid starting new motor rehabilitation programs during the study.

A physical therapist or occupational therapist assessed motor function at baseline and when the training program was complete, the authors wrote.

One patient left the study because of a scheduling conflict. The investigators found that another patient did not have enough surface EMG activity in the target muscles to control the device. Their report focused on the six patients who completed the program.

The patients trained 2 to 3 hours a week for a total of 18 hours of exercise over a 6- to 9-week period. While wearing the AJB, the patients performed functionally oriented upper extremity tasks tailored to their individual motor abilities, including moving blocks from one spot to another or operating a light switch.

Encouraging results

Stein and colleagues used the upper extremity portion of the Fugl-Meyer scale to measure motor control. Their results showed that the patients had statistically significant gains in motor control. Before treatment, the patients scored a mean of 15.5 on the Fugl-Meyer scale; by the end of treatment, their scores rose to 19 (P=.04).

When they evaluated muscle hypertonicity with the modified Ashworth scale (MAS), the investigators saw a decrease in the summated upper limb MAS after treatment, dropping from a mean of 19 to a mean of 15.17 (P=.04), the authors wrote. The investigators found that the largest MAS decrease was in the elbow. The combined elbow flexor and elbow extensor tone decreased from a mean of 4.67 to 2.33 (P=.009).

The device was well tolerated by all study participants, and there were no complications, according to the report.

“This is a pilot study,” said Stein, who is also the interim chairman of the department of physical medicine and rehabilitation at Harvard Medical School. “This is not a definitive study, by any means. But it established the feasibility and apparent benefit in a small group of subjects of this new device, which is an EMG-controlled powered upper orthosis.”

Exciting direction

“I think [the AJB] is an exciting direction in this type of research,” Stein continued. “It is a wearable device, which I think is appealing. It allows people to do exercises in a more real-life environment.”

The orthosis used in this study was a prototype. The device was invented by Kailas Narendran and John McBean, who were graduate students and researchers at MIT during their collaboration with Stein. Narendran and McBean have since co-founded their own company, Myomo Inc., and have continued to refine the orthosis.

“They have come out with a newer version of the device which I think is really nicely streamlined,” Stein said.

Long-term functional device?

Active joint brace
The active joint brace combines an exoskeletal robotic brace with electromyography control.
Image reprinted with permission of Myomo Inc.

There are a few ways to use the AJB, Stein said. The most obvious use is as a training device, which is what they examined with this study. When using the AJB as a training device, the goal is to stimulate the recovery of brain function, he said. When the exercise program is complete, the patient no longer needs the orthosis.

Another potential use is for patients with chronic weakness, Stein said. These patients would “essentially need [the brace] as a long-term functional device – an orthosis that they would wear on a daily basis.” Stein and his colleagues have not explored this area much yet, but they plan to do so in the future.

The device is pending FDA approval.

“We submitted our application for FDA clearance last August and expect to be able to bring the device to market by the fall of this year,” said Maureen Liberty, vice president of marketing for Myomo Inc.

The company plans to market the orthosis as the Myomo e100 NeuroRobotic System.

For more information:

  • Stein J, Narendran K, McBean J, et al. Electromyography-controlled exoskeletal upper-limb-powered orthosis for exercise training after stroke. Am J Phys Med Rehabil. 2007;86:255-261.

Colleen Owens is a correspondent for O&P Business News.

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