Personalized Range of Motion Scaled Wrist Pointing for Robotic- Based Motor Impairment Assessment

Movement smoothness is a commonly employed metric of motor impairment in stroke patients due to a strong correlation with Fugl-Meyer Assessment score, and because it can be assessed with functional-oriented tasks like wrist pointing. Robotic assessments of wrist-pointing tasks typically use targets located at fixed points in the workspace, which can exceed the range of motion (ROM) of stroke patients who exhibit severe motor impairment. We hypothesize that movement smoothness assessed based on movements that do not reach visual targets may conflate assessment of movement smoothness with ROM. We propose that scaling the locations of wrist pointing targets for wrist flexion-extension and radial-ulnar movements from a ROM assessment will better reflect movement characteristics. In this paper, we analyze wrist-pointing movements for fixed and ROM-scaled target locations. We evaluate wrist-pointing performance in both conditions for 8 neurologically-intact participants whose wrist ROM was constrained with a wrist brace simulating ROM deficits present after stroke. Results show that failing to reach targets during wrist pointing has a significant negative impact on movement smoothness. Additionally, scaling target placement to ROM increases the proportion of targets reached while producing practically equivalent movement smoothness to successfully reached fixed target locations. These findings support incorporation of ROM-scaled target placement into movement smoothness assessment.