Step length asymmetry is representative of compensatory mechanisms used in post-stroke hemiparetic walking

Abstract

Post-stroke hemiparetic subjects walk with asymmetrical step lengths that are highly variable between subjects and may be indicative of the underlying impairments and compensatory mechanisms used. The goal of this study was to determine if post-stroke hemiparetic subjects grouped by step length asymmetry have similar abnormal walking biomechanics compared to non-impaired walkers. Kinematic and ground reaction force data were recorded from 55 hemiparetic subjects walking at their self-selected speed and 21 age and speed-matched non-impaired control subjects. Hemiparetic subjects were grouped by paretic step ratio, which was calculated as the paretic step-length divided by the sum of paretic and nonparetic step-lengths, into high (>0.535), symmetric (0.535-0.465) and low (<0.465) groups. Non-parametric Wilcoxin signed-rank tests were used to test for differences in joint kinetic measures between hemiparetic groups and speed-matched control subjects during late single-leg stance and pre-swing. The paretic leg ankle moment impulse was reduced in all hemiparetic subjects regardless of their paretic step ratio. The high group had increased nonparetic leg ankle plantarflexor and knee extensor moment impulses, the symmetric group had increased hip flexor moment impulses on both the paretic and nonparetic leg and the low group had no additional significant differences in joint moment impulses. These results suggest that the direction of asymmetry can be used to identify both the degree of paretic plantarflexor impairment and the compensatory mechanisms used by post-stroke hemiparetic subjects.

Copyright © 2011 Elsevier B.V. All rights reserved.

Figures

Figure 1

AP impulse for control (yellow, average of right and left legs), paretic leg (green) and nonparetic leg (red) in late single-leg stance and pre-swing phases. Hemiparetic subgroups were determined by the paretic step ratio (PSR) (low: PSR0.53). * denotes a significant difference relative to the controls, # denotes significant a significant difference between PSR groups; all p

Figure 2

Ankle (plantarflexor positive), knee (extensor positive), and hip (flexor positive) joint moment impulses for control (yellow, average of right and left leg), paretic leg (green), and nonparetic leg (red) in their respective late single-leg stance and pre-swing phases. Hemiparetic subgroups were determined by the paretic step ratio (PSR) (low: PSR0.53). * and † denote significant difference relative to the controls, p<0.05 and p<0.01; # denotes a significant difference between PSR groups, p<0.05.