How accuracy of foot-placement is affected by the size of the base of support and crutch support in stroke survivors and healthy adults

Background: The high prevalence of falls due to trips and slips following stroke may signify difficulty controlling balance and adjusting foot-placement in response to the environment. We know very little about how controlling foot-placement is affected by balance requirements and the effects of stroke. Therefore, in this study the research question is how foot-placement control is affected by balance support from crutches and reducing or enlarging the base of support. By understanding how foot-placement control and balance deficits following stroke interact, rehabilitation efforts can be more effectively targeted towards the cause of poor mobility. Methods: Young (N = 13, 30 +/- 6 years) and older (N = 10, 64 +/- 8 years) healthy adults and stroke survivors (N = 11, 67 +/- 9 years) walked to targets on an instrumented treadmill with or without crutch support for balance. Targets were randomized to either reduce or increase the base of support in the antero-posterior (AP) or medio-lateral (ML) direction. Mean and absolute foot-placement error were measured using motion analysis. These outcomes were compared using repeated measures ANCOVA with walking speed as a covariate. Results: Overall, stroke survivors missed more targets (9.1 +/- 2.3%, p = 0.001) than young (1.0 +/- 2.5%) and older (0.2 +/- 2.1%) healthy adults (p = 0.001). However, there were no significant differences between groups in foot-placement error. Crutch support reduced both AP and ML foot-placement error (p= < 0.001, AP 5.2 +/- 0.5cm unsupported, 4.1 +/- 0.4cm supported, ML 2.3 +/- 0.2cm unsupported, 1.9 +/- 0.2cm supported) for all participants. Interaction effects indicate crutch support reduced foot-placement error more when narrowing (unsupported 2.8 +/- 0.2cm, supported 1.8 +/- 0.2cm) than widening (unsupported 2.6 +/- 0.4cm, supported 2.4 +/- 0.4cm) steps (p < 0.001), Significance: Stroke survivors have greater difficulty accurately adjusting steps in response to the environment. Crutch support reduces foot-placement error for all steps, but particularly when narrowing foot-placement. These results provide support for the implication of walking aids, which support balance to improve ability to adjust footplacement in response to the environment.