A new prototype for a hand exoskeleton system (HES) has been designed and tested in a patient with spinal muscular atrophy (SMA), as detailed in Frontiers in Neurorobotics.
The new HES is intended to provide assistance during activities of daily living as well as telerehabilitation. Researchers from the Mechatronics and Dynamic Modeling Laboratory in the Department of Industrial Engineering at the University of Florence in Italy designed the HES to be wearable and portable.
They mounted the actuators on the back of the hand and designed a separate module that detects surface electromyographic signals connected to the wrist. “The device is force effective, intuitive, and fully wearable and portable,” they said.
The HES was tested in a patient with SMA type 2 which impaired the extensor muscles in both hands. The loss of strength resulted in hand contractures and clenched fists. The patient performed the Action Research Arm Test 3 times, once without the HES and twice with it, to evaluate the assistance provided by the device.
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The patient scored a 36 in their session without the HES but only scored 29s on the 2 sessions wearing the HES. The authors attributed the lower performance to “the overall dimensions of the finger-handling mechanisms, which, although they have been reduced compared to the first prototype ones still prevent movements in confined spaces, e.g., when the patient hand approaches the table to pinch small-size items on it.”
The patient did not fail tasks that involved interaction between the thumb and index finger but did when the thumb needed to interact with the middle or ring finger. The HES enabled the patient to have “a more correct and effective hand grip” on the tasks that the patient was able to complete.
The authors acknowledged some flaws in the current prototype design including the current pulley system which only allows for actuator-assisted hand opening movements. The device also does not currently include a mechanism to assist thumb movements, and the size and placement of the actuator system make it hard to use in confined spaces such as turning a handle or pinching small objects.
“Overall, the novelty of this study lies in proposing a design that, differently from other state-of-the-art solutions, collects most of the primary crucial characteristics of assistive and rehabilitative devices (i.e., wearability, portability, safety, comfort, compliance, customization, force, and cost-effectiveness),” the researchers concluded.
“Nonetheless, the authors are well aware of the wide room for improvements left, in particular, regarding component miniaturization, thumb actuation, and independent finger movement.”
Secciani N, Brogi C, Pagliai M, et al. Wearable robots: an original mechatronic design of a hand exoskeleton for assistive and rehabilitative purposes. Front Neurorobot. 2021;15:750385. doi:10.3389/fnbot.2021.750385