Quantification of abnormal upper limb movement during walking in people with acquired brain injury

Background: Abnormal upper limb movements frequently affect people with acquired brain injury (ABI) during walking. Three-dimensional motion analysis (3DMA) can quantify upper limb abnormality kinematically, with composite scores condensing multiple joint axes data into a single score. Research Question: Are 3DMA-derived composite scores valid (known-groups and convergent validity), reliable and able to quantify speed-related changes in abnormal upper limb movement during walking? Methods: This observational study compared 42 adults with ABI and abnormal upper limb movements during walking with 36 healthy controls (HC) at a matched walking speed intention. Participants underwent 3DMA assessment of self-selected and fast walking speeds. Composite scores quantified the affected upper limb’s kinematic abnormality. The Arm Posture Score arithmetic mean version (APSam) and 1.96 standard deviation reference-range scaled versions; the Kinematic Deviation Score mean (KDSm) and worst score (KDSw) were evaluated for association with each other and subjective abnormality rating (Pearson’s r correlation), test-retest reliability (intra-class correlation coefficient (ICC)), and ability to quantify speed-related changes in abnormal upper limb movement (Cohen’s d effect size (ES), % change scores). Results: Very strong correlations existed between composite scores. The KDSm under-classified upper limb abnormality, whereas the KDSw captured the majority of ABI participants. All scores had moderate-strong correlations with subjective rating of abnormal upper limb movements (r = 0.54-0.79) and very strong test-retest reliability (ICCs>0.81). The APSam demonstrated a 16% (ES 0.76) walking speed-related increase in upper limb abnormality, whilst decreases were demonstrated in the KDSm 26% (ES 0.90) and KDSw 35% (ES 0.96). Significance: The APSam, KDSw, and number of abnormal joint axes comprehensively assess the whole upper limb abnormal movements, accurately classifies abnormality, and quantifies severity. This study illustrated notable presence of abnormal upper limb movements at self-selected walking speed and small increase at fast speeds. However, when scaled to HC variability, the fast walk kinematics became less abnormal due to increased HC movement variability.