Modeling of joint synergy and spasticity in stroke patients to solve arm reach tasks

Abstract

Abstract-Strokerehabilitation often focuses on counteracting stroke-induced muscle weakness so as to allow patients to regain the ability to complete activities of daily living. However, other motor issues such as deleterious joint synergies (involuntary coactivation of joints) and spasticity (involuntary muscular contractions that limit range of motion) may impede stroke victims and thus necessitate modification of the training methods utilized in rehabilitation. To increase the rehabilitation efficacy and help patients relearn how to complete essential reach tasks, alternative routes that account for the synergy and spasticity must be identified. The procedure for finding efficient reach task paths is accomplished by performing a branched iterative search. Each path is scored based on the distance from the final hand position to the reach task target as well as the total travel distance of the path. Synergy is included in the algorithm by multiplying the joint command, the desired joint change, by a matrix of synergy interactions. Spasticity is included by either imposing hard joint angle limits or by specifying a spastic region through which movement induces score penalties. The algorithm successfully reduces travel through spastic regions while counteracting synergistic deviations that would increase path travel distance.