The integration of vision and proprioception for obstacle crossing in people with motor-incomplete spinal cord injury

Background: In people with motor-incomplete spinal cord injury (m-iSCI), the ability to perform skilled walking tasks (e.g. obstacle crossing) is an essential component of functional mobility. Sensorimotor integration of visual and proprioceptive inputs, alongside indicators of functional ambulation (i.e. self-efficacy) is important for successful obstacle crossing. Thus, the overall objective was to understand how motor and sensory (specifically proprioception) deficits in people with m-iSCI affect obstacle-crossing strategies. Methods: Nine individuals with m-iSCI and 10 able-bodied controls were asked to step over an obstacle scaled to their motor abilities under full and obstructed vision conditions. An eye tracker was used to determine gaze behavior, motion capture analysis was used to determine toe kinematics relative to the obstacle, and electrogoniometers were used to determine peak ankle, hip and knee (dorsi)flexion angles during obstacle crossing. In subjects with m-iSCI, questionnaires were used to determine balance and ambulatory self-efficacy. Lower limb proprioceptive sense was assessed using a hip and knee joint position-matching task using the Lokomat and customized software controls. Results: Lower limb proprioceptive sense was impaired and varied across subjects with m-iSCI. m-iSCI subjects tended to glance at the obstacle more frequently as they approached it and with shorter gaze durations compared to controls. Decreased self-efficacy and impaired proprioceptive sense may have contributed to these differences in gaze behavior. Obstruction of the lower visual field led to appropriate modulation of lead and trail horizontal distance, however toe clearance height in m-iSCI subjects was increased to a greater extent than controls. An emerging relationship was observed between proprioceptive sense and toe clearance height, in particular for the trail limb. m-iSCI subjects increased peak knee flexion to a greater extent than controls when vision was obstructed. All other changes in joint kinematics were similar across groups. Conclusion: The results of this study indicate that people with m-iSCI rely more heavily on vision to cross obstacles and show impairments in the key gait parameters required for successful obstacle crossing. Our data suggest that proprioceptive deficits also need to be considered in rehabilitation programs aimed at improving functional mobility in individuals with m-iSCI.Education, Faculty ofKinesiology, School ofGraduat