Inner, close-to-body reachable workspace to quantify upper extremity mobility: a study on children with brachial plexus birth injury.

Brachial plexus birth injury (BPBI) results in individualized impairments in upper extremity (UE) mobility. A patient-specific understanding of these movement limitations is critical for optimizing decision-making and outcomes; however, current assessments may fail to capture the entirety of a patient's UE mobility. Reachable workspace quantifies an individual's global UE mobility by measuring the regions that can be reached by their hand. Despite most UE activities of daily living requiring adequate close-to-body function, current workspace approaches only assess far-from-body mobility. This study assessed the ability of a motion capture-based workspace approach to evaluate inner, close-to-body UE mobility in children with BPBI. It was hypothesized that the BPBI affected limb would have less inner, close-to-body workspace than the unaffected limb, especially in regions requiring UE movements commonly impaired in BPBI. Fifteen children with unilateral BPBI were assessed with motion capture using real-time visual feedback to measure UE workspace in all regions surrounding the body. All inner, close-to-body points reached by the hand were recorded. A two-way repeated measures ANOVA evaluated percentage workspace reached in each region surrounding the head, thorax, and abdomen. The affected limb had significantly less workspace reached than the unaffected limb for 8 of 9 regions (mean interlimb differences by region, 17.0-49.2%). Affected limb workspace deficits corresponded to common movement impairments in BPBI demonstrating the clinical relevance of this tool. Assessment of inner, close-to-body reachable workspace may provide a valuable new perspective on UE mobility to help guide clinical decision-making and outcomes assessment.