Biomechanical Correlates of Falls Risk in Gait Impaired Stroke Survivors

Abstract

Increased falls risk is prevalent among stroke survivors with gait impairments. Tripping is the leading cause of falls and it is highly associated with mid-swing Minimum Foot Clearance (MFC), when the foot's vertical margin from the walking surface is minimal. The current study investigated MFC characteristics of post-stroke individuals (n = 40) and healthy senior controls (n = 21) during preferred speed treadmill walking, using an Optotrak 3D motion capture system to record foot-ground clearance. In addition to MFC, bi-lateral spatio-temporal gait parameters, including step length, step width and double support time, were obtained for the post-stroke group's Unaffected and Affected limb and the control group's Dominant and Non-dominant limbs. Statistical analysis of MFC included central tendency (mean, median), step-to-step variability (standard deviation and interquartile range) and distribution (skewness and kurtosis). In addition, the first percentile, that is the lowest 1% of MFC values (MFC 1%) were computed to identify very high-risk foot trajectory control. Spatio-temporal parameters were described using the mean and standard deviation with a 2 × 2 (Group × Limb) Multivariate Analysis of Variance applied to determine significant Group and Limb effects. Pearson's correlations were used to reveal any interdependence between gait variables and MFC control. The main finding of the current research was that post-stroke group's affected limb demonstrated lower MFC 1% with higher variability and lower kurtosis. Post-stroke gait was also characterised by shorter step length, larger step width and increased double support time. Gait retraining methods, such as using real-time biofeedback, would, therefore, be recommended for post-stroke individuals, allowing them to acquire optimum swing foot control and reduce their tripping risk by elevating the swing foot and improving step-to-step consistency in gait control.

Keywords: falls prevention; gait retraining; minimum foot clearance; stroke; tripping prevent.

Figure 1

(top) Illustration of MFC, marker attachment at toe and heel; (middle) Histogram description, 1% = first percentile, 25% = 25th percentile, 75% = 75th percentile, IQR (interquartile range) = 75th-25th percentile; (bottom left) step length and step width; (bottom right) walking test environment, Cam = motion capture camera.

Figure 2

MFC histogram. Stronger vs. Weaker: Healthy (dominant vs. non-dominant) and Stroke (unaffected vs. affected).

Figure 3

Spatio-temporal gait parameters (mean ± SD). (top) step length = group effects for mean and SD, (middle) step width = group effects for mean and SD, (bottom) double support time = group effects for mean and SD. Stronger vs. Weaker limb classification: healthy = dominant vs. non-dominant, Stroke = unaffected vs. affected.

Figure 4

Protocol for biofeedback training for MFC. (left) Biofeedback training setup, (right) concept of MFC biofeedback training, red dot (MFC), targeting to control MFC within the band between upper/lower boundaries, target band = (mean + SD) ± (0.5*SD).