Paretic limb biomechanical response to hip exoskeleton limb assistance strategies during walking for individuals post-stroke.

Abstract

Individuals post-stroke with hemiparetic gait often experience impaired mobility, which can be restored using powered exoskeletons. Specifically, hip exoskeletons can deliver positive work to the leg to help initiate leg swing; however, it is unclear which limb assistance strategy (e.g., unilateral or bilateral assistance) best improves walking performance due to the asymmetric characteristics of hemiparetic gait. Therefore, the purpose of this study was to investigate how different hip exoskeleton limb assistance strategies affect lower-limb joint biomechanics during walking for individuals post-stroke. We hypothesized that bilateral assistance would best improve late stance paretic leg orientation and swing initiation, unilateral paretic limb assistance would improve interlimb asymmetries and unilateral nonparetic limb assistance would indirectly improve late stance kinematics. We found bilateral assistance significantly increased paretic hip flexion angle, providing an improvement in leg swing initiation, and improved ankle joint work symmetry, suggesting an improvement in propulsion mechanics. Unilateral paretic limb assistance significantly increased paretic knee flexion during swing, which is a common rehabilitative target to improve stiff-knee gait for individuals post-stroke, and significantly improved joint work symmetry between limbs, which is beneficial for individuals who have increased reliance on the nonparetic limb. Unilateral nonparetic assistance did not improve late stance kinematics. These results provide insight into joint-level responses of individuals post-stroke and can help tailor hip exoskeleton assistance for individuals post-stroke based on rehabilitation targets.