Abnormal Synergies and Muscle Weakness Identified in Stroke Survivors via Wrist Position Probability Distributions

Stroke significantly impairs motor function, often causing abnormal synergies and muscle weakness. Clinical assessments are vital for diagnosing impairment and guiding treatments but are labor-intensive and time consuming. Moreover, the supply of clinicians cannot keep pace with the growing number of individuals affected by stroke. This study presents a more efficient strategy to assess motor function, substantially reducing the time and effort required for assessment while eliminating the need for direct accessor involvement. Our proposed method leverages wrist position probability distribution during two minutes of free upper-extremity movements of individuals with chronic stroke, tracked by a markerless motion capture system. Two probabilistic models, rectilinear and icosahedron-based, revealed stroke survivors spend significantly less time in four posterior zones and more time in the anterior-inferior-medial zone. The icosahedron model identified abnormal flexion synergies in 10 stroke survivors (52.6%), two more than the rectilinear model. Conversely, the rectilinear model demonstrated stronger associations with clinical scores, with three zones showing strong correlations (R>0.70) compared to one in the icosahedron model. These findings highlight the promise of wrist position probability distribution models as tools to detect movement deficits and abnormal synergies in stroke survivors. Future work could integrate joint angles to improve clinical insights.