The Electronic Grip Gauge (EGG): Automated Assessment of Sensorimotor Hand Function Using an Instrumented Fragile Object.

Hand dexterity assessments play a crucial role in informing the rehabilitative care of individuals with upper-limb hemiparesis. However, current assessments often struggle to evaluate the hand's ability to precisely control grip force, a skill vital for daily activities like handling fragile objects. Here we describe the design of the Electronic Grip Gauge (EGG), an adjustable-weight, instrumented "fragile" object that measures grip force, load force, acceleration, orientation, and relative position. Embedded sensors enable automatic segmentation and analysis of EGG transfers in various modes. In "Non-Fragile" mode, there is no break threshold; the EGG serves as an automated variant of the Box-and-Blocks test. In "Fragile" mode, the EGG simulates fragility by playing a "break" noise if grip force exceeds a set threshold, requiring grip control to prevent breaks. In "Fragile-Feedback" mode, audio-visual feedback is provided proportional to applied grip force to supplement potentially impaired tactile feedback. Demonstrating functionality, we evaluated sensorimotor differences between 26 hemiparetic and 26 age-matched healthy participants. In "Fragile" mode, paretic hands were significantly slower, applied excessive force, and broke the EGG more frequently than contralateral and healthy control hands. In "Fragile-Feedback" mode, a subset of paretic hands improved, transferring the EGG faster and/or with less force. This work demonstrates the EGG's utility in automatically quantifying sensorimotor deficits and that, for a subset of hemiparetic patients, audiovisual feedback could potentially coach and rehabilitate hand function. Collectively, this work showcases the EGG's potential as both an assessment and rehabilitation device for grip force control-a critical skill in hand therapy.