Understanding inconsistent step-length asymmetries across hemiplegic stroke patients: impairments and compensatory gait.

BACKGROUND In hemiplegic gait, step length typically differs in magnitude between paretic and nonparetic sides. However, the direction of step-length asymmetry varies across stroke patients. OBJECTIVE The study sought to understand directional variations in step-length asymmetry in terms of asymmetries in forward foot placement relative to the trunk and trunk progression. METHODS A total of 10 hemiplegic stroke patients and 9 healthy elderly controls walked at a self-selected comfortable speed while pelvic and heel marker positions were recorded. Step length, forward foot placement relative to the trunk, and trunk progression of paretic and nonparetic steps were quantified, as well as the asymmetries therein. RESULTS The 3 asymmetry indices in question varied within individual patients and occasionally fell within control reference ranges, whereas directional variations across stroke patients were observed for asymmetries in step length and forward foot placement only. Despite heterogeneity in asymmetry across patients, step-length asymmetry was determined by the sum of asymmetries in forward foot placement and trunk progression. Asymmetries in trunk progression and forward foot placement were negatively correlated. No significant association was observed between step-length asymmetry and any other asymmetry index. CONCLUSIONS Step-length asymmetry was accounted for by asymmetries in forward foot placement and trunk progression, whereas their relative contribution accounted for directional variations in step-length asymmetry. Partitioning of step-length asymmetry further helped to identify individual impairments and compensatory gait strategies. An encompassing hemiplegic gait evaluation should therefore include an assessment of foot positioning relative to the trunk.