Characterization of multi-finger twist motion toward robotic rehabilitation

Stroke or other neurological disorders potentially lead to movement deficits that may be recovered through proper rehabilitation. Robotic therapy has been applied to larger limbs such as the arms but not as commonly for the hand. It has been shown that virtual robotic environment with feedback distortion has a positive therapeutic effect in single finger movement. To expand this one finger therapeutic environment to more functional movements, our particular interest is applying feedback distortion to the everyday motor task of twisting bottle caps and jar lids. In order to understand what parameters to distort, unimpaired subjects´ stereotypical movements were characterized with an intention to identify the differences with impaired population groups. This paper describes the hardware and software details of the haptic rotational twist-cap device developed to characterize, diagnose, and rehabilitate coordinated multi-finger twist movements. Using this device, it is shown the tangential and radial forces applied by each finger have stereotypical profiles for the unimpaired population. In addition, individual results from stroke, multiple-sclerosis (MS), and elderly subject population are presented. This preliminary data show different types of deviation from the control data providing insight into parameters that should be distorted during robotic rehabilitation.