PullExo: An orthosis-based mobile hand exoskeleton with on-device visual biofeedback.

Background: Grasping function is severely compromised in individuals with spinal cord injury, significantly limiting their independence in activities of daily living. While robotic hand exoskeletons offer promising solutions, current systems often separate control and motor units from the wearable body, resulting in additional components to be worn by the patient. Furthermore, the integration of an immediately accessible user interface, capable of providing biofeedback, has not been fully explored.

Purpose: To develop and evaluate a standalone mobile hand exoskeleton that assists the user when grasping objects and provides real-time visual biofeedback during operation, aiming to improve patient autonomy and catalyze rehabilitation.

Study design: A proof-of-concept prototype was designed, developed, and tested in a preliminary study.

Methods: A prototype was built using an upcycled postconsumer textile waste, repurposing a wrist-hand-thumb orthosis to house the actuation system, control unit, and a visual biofeedback screen directly on itself. Pilot studies were conducted on a spinal cord injury patient and a healthy subject. Fingertip forces were measured, and kinematics were explored using a motion capture system. Additionally, ergonomics and the prototype's effectiveness in assisting grasping across a range of daily life objects were evaluated.

Results: The results indicate its potential to improve grasping function, enabling the patient to exert over three times their baseline fingertip force without relying on compensatory movements such as tenodesis. Weighing only 318 g, the system enabled independent donning in approximately 1.5 minutes and effectively assisted in grasping objects ranging from a pen to a 500-g water bottle.

Conclusions: PullExo demonstrated potential as a lightweight, standalone assistive and rehabilitative system for improving grasping function and autonomy. Future studies with larger sample sizes are planned to confirm its overall efficacy and explore the clinical implications of integrated biofeedback.