Defining the design requirements for an assistive powered hand exoskeleton: A pilot explorative interview study and case series

Abstract

Background: Powered hand exoskeletons are an emerging technology that have shown promise in assisting individuals with impaired hand function. A number of hand exoskeleton designs have been described in the literature; however, the majority have not been supported by patient-oriented criteria.

Objective: The aim of this study was to define preliminary end-user needs and expectations for an assistive hand exoskeleton.

Study design: Explorative interview and case series.

Methods: Six clinicians and eight individuals with impaired hand function were interviewed in small groups or individually. A standardized list of questions was used to elicit feedback on specific design criteria or promote the discovery of new criteria. In addition, three participants with impaired hand function returned for a second session where hand characteristics, such as range of motion and force required to flex/extend fingers, were recorded to further quantify design requirements.

Results: Interview responses indicated that there was general consensus among participants on criteria relating to important grasp patterns, grip strength, wear time, and acceptable bulk/weight. However, interview responses and hand characteristics also revealed important differences between individuals with impaired hand function.

Conclusion: Qualitative and quantitative data were collected to develop an understanding of end-user design requirements for assistive hand exoskeletons. Although the data collected were helpful in identifying some preliminary criteria, differences between participants exist and identifying a universal set of criteria applicable across individuals with impaired hand function is challenging. This work reinforces the importance of involving users of rehabilitation technology in the device development process.

Figure 1.

Custom load cell attachment used to move the participant’s finger while measuring the force required to assist with the movement. Movements assessed were (a) index finger extension, (b) flexion of the metacarpalphalangeal (MCP) joint on the index finger, (c) flexion of the proximal interphalangeal (PIP) and distal interphalangeal ( DIP) joints on the index finger, and (d) thumb opposition.

Figure 2.

List of tasks that participants indicated they would like to perform with the help of a hand exoskeleton sorted, by grip type (precision, power, and miscellaneous) as well as the number of participants who mentioned each task.

Figure 3.

Photographs of Par06’s hand (brachial plexus injury, BPI) during (a) rest, (b) active hand opening, (c) cylinder grip, (d) hook grip, (e) spherical grip, (f) tip-to-tip grip, (g) tripod grip, and (h) lateral key grip.

Figure 4.

Mean absolute value of surface electromyography (EMG) signals recorded from participants’ forearms during wrist flexion (left) and extension (right) for a representative trial. Signals are normalized based on the maximum signal observed between the two channels across EMG trials. SCI: spinal cord injury, BPI: brachial plexus injury.