Development and Evaluation of a Device to Assess Finger Individuation in Neurorehabilitation

Finger individuation, the ability to independently control fingers, is a critical component of hand function that is often impaired in people with neurological conditions. To address the need for sensitive tools to measure finger individuation in clinical and research settings, an assessment device was developed and tested. Equipped with force sensors under each finger, an individuation index (IndX) in both flexion and extension was calculated. Feasibility of the device was assessed by measuring able-bodied participants and neurological patients. The reliability of the finger individuation assessments was evaluated in a test-retest setting, showing high consistency, with Intraclass Correlation Coefficients (ICC) and Spearman correlation classified as moderate to excellent (ICC for flexion of thumb: 0.73, $p < 0.001$: index: 0.68, $p < 0.001$: middle: 0.48, $p=0.003$; ring: 0.72, $p < 0.001$; little: 0.80, $p < 0.001$). Validity was further examined by comparing the IndX across fingers and between groups, utilizing t-tests and the Area Under the Curve (AUC) from Receiver Operating Characteristic analysis. Although AUC values indicated a mixed discriminative ability, the device successfully captured differences in finger control between able-bodied individuals and patients. These results indicate that the device offers a reliable and effective means of quantifying finger individuation, opening the door to advanced fine hand motor control research and through that, personalized rehabilitation.