Dynamic instability during post-stroke hemiparetic walking

Abstract

Falls and fall-related injuries cause extremely costly and potentially fatal health problems in people post-stroke. However, there is no global indicator of walking instability for detecting which individuals will have increased risk of falls. The purposes of this study were to directly quantify walking stability in stroke survivors and neurologically intact controls and to determine which stability measures would reveal the changes in walking stability following stroke. This study thus provided an initial step to establish objective measures for identifying potential fallers. Nine post-stroke individuals and nine controls walked on a treadmill at four different speeds. We computed short-term local divergence exponent (LDE) and maximum Floquet multiplier (maxFM) of the trunk motion, average and variability of dynamic margins of stability (MOS) and step spatiotemporal measures. Post-stroke individuals demonstrated larger short-term LDE (p = 0.002) and maxFM (p = 0.041) in the mediolateral (ML) direction compared to the controls but remained orbitally stable (maxFM < 1). In addition, post-stroke individuals walked with greater average step width (p = 0.003) but similar average ML MOS (p = 0.154) compared to the controls. Post-stroke individuals also exhibited greater variability in all MOS and step measures (all p < 0.005). Our findings indicate that post-stroke individuals walked with greater local and orbital instability and gait variability than neurologically intact controls. The results suggest that short-term LDE of ML trunk motion and the variability of MOS and step spatiotemporal measures detect the changes in walking stability associated with stroke. These stability measures may have the potential for identifying those post-stroke individuals at increased risk of falls.

Correlations between measures of dynamic balance in individuals with post-stroke hemiparesis

“…This measure is based on foot placement while accounting for body CoM position and velocity and has been used to assess dynamic balance in young healthy individuals in destabilizing environments (e.g., McAndrew Young et al, 2012), older adults while stepping to targets (Hurt and Grabiner, 2015), amputees (e.g., Bolger et al, 2014; Gates et al, 2013; Hof et al, 2007) and post-stroke individuals (e.g., Hak et al, 2013; Kao et al, 2014). Similarly, whole-body angular-momentum has been used to assess dynamic balance in a number of patient populations including post-stroke hemiparetic individuals (Nott et al, 2014), amputees (e.g., Pickle et al, 2014; Sheehan et al, 2015; Silverman and Neptune, 2011) and older adults (e.g., Pijnappels et al, 2005b).…”

Do clinical assessments, steady-state or daily-life gait characteristics predict falls in ambulatory chronic stroke survivors?

“…Nevertheless, gait characteristics of stroke survivors have also been shown to predict falls (16). Moreover, with regard to gait stability, it has been shown that the local divergence exponent (LDE) was larger in stroke survivors than in age-matched healthy peers (17), indicating less stable gait. Still, stroke survivors had equal margins of stability (MoS) (17) probably accomplished by a larger step width (18).…”

Walking behaviors for stroke survivors: comparison between straight line and curved path

“…During the usual straight line walking, spatiotemporal variabilities have been known to be an early indicator of mobility impairment and associated with risk of falls. Stroke survivors show decreased gait velocity, asymmetric walking pattern, and increased step width, and thereby show a different walking pattern compared to before the stroke event [14]. Spastic or synergistic gait patterns are atypical movement patterns in hemiparetic stroke patients and include contact with ground via toe strike or foot flat, loss of hip extension, and usage of excessive forward trunk flexion to initiate [1].…”