Variability of Leg Kinematics during Overground Walking in Persons with Chronic Incomplete Spinal Cord Injury

Abstract

Incomplete spinal cord injury (iSCI) often leads to partial disruption of spinal pathways that are important for motor control of walking. Persons with iSCI present with deficits in walking ability in part because of inconsistent leg kinematics during stepping. Although kinematic variability is important for normal walking, growing evidence indicates that excessive variability may limit walking ability and increase reliance on assistive devices (AD) after iSCI. The purpose of this study was to assess the effects of iSCI-induced impairments on kinematic variability during overground walking. We hypothesized that iSCI results in greater variability of foot and joint displacement during overground walking compared with controls. We further hypothesized that variability is larger in persons with limited walking speed and greater reliance on ADs. To test these hypotheses, iSCI and control subjects walked overground. Kinematic variability was quantified as step-to-step foot placement variability (end-point), and variability in hip-knee, hip-ankle, and knee-ankle joint space (angular coefficient of correspondence [ACC]). We characterized sensitivity of kinematic variability to cadence, auditory cue, and AD. Supporting our hypothesis, persons with iSCI exhibited greater kinematic variability than controls, which scaled with deficits in overground walking speed (p < 0.01). Significant correlation between ACC and end-point variability, and with walking speed, indicates that both are markers of walking performance. Moreover, hip-knee and hip-ankle ACC discriminated AD use, indicating that ACC may capture AD-specific control strategies. We conclude that increased variability of foot and joint displacement are indicative of motor impairment severity and may serve as therapeutic targets to restore walking after iSCI.

Differential deficits in spatial and temporal interlimb coordination during walking in persons with incomplete spinal cord injury

“…The non-significant association between the composite spatial and temporal asymmetry indices (Figure 4b) may therefore be driven by unequal deficits in phase accuracy between spatial and temporal domains rather than differences in step to step consistency. This suggests corrupt sensorimotor control underlying the reproducibility of consistent motor coordination during walking, supplementing prior reports of increased kinematic variability within a single limb [6]. Thus, even though accuracy maybe differentially impaired between space and time domains, consistency from step to step appears equally impaired.…”

“…Specifically, we tested for correlations between spatial and temporal AI, GCI, and PCI, as well as, AI and walking assessment scores (10MWT, 6MWT, and SCI-FAI) in iSCI subjects. Since a prior study showed persons with iSCI who required a "walker" for ambulation had greater intralimb coordination deficits as compared to those who used a less restrictive AD (i.e., cane, loftstrands) [6], we predicted a similar result with interlimb coordination. Thus, we stratified our iSCI subjects into those who used a "walker" (N = 7) for ambulation and those who did not (N = 9).…”

“…Clinical gait measures are useful tools to quickly assess walking ability in persons with iSCI [34]. However, they do not capture the underlying interlimb coordination strategies used by individuals [35], especially those more reliant on AD use [6]. SCI-FAI only modestly correlated with asymmetry parameters, suggesting that this qualitative clinical scale of leg coordination may not adequately identify interactions between spatial and temporal coordination deficits that are patient specific.…”

“…Similar impairments in temporal coordination, depicted by Grasso and colleagues, showed co-activity of muscles spanning the hip, knee, and ankle coincided with inconsistent single-limb step placement during transitions between stance and swing phases of walking [4]. Similarly, Sohn and colleagues found iSCI-induced intralimb deficits in spatial (step placement) coordination corresponded to inconsistent step-by-step foot placement and interjoint coordination, which corresponded to limited walking speed and more restrictive assistive device (AD) use (i.e., walker); those who walked slower, demonstrated more kinematic variability and more reliance on AD [6].…”

Walking and Balance Outcomes Are Improved Following Brief Intensive Locomotor Skill Training but Are Not Augmented by Transcranial Direct Current Stimulation in Persons With Chronic Spinal Cord Injury

“…In addition to improvements in walking speed, participation in 3 days of MST was associated with significant increases in stride frequency (cadence) and length. Gait kinematics associated with walking impairments in persons with SCI have been reported extensively ( Field-Fote and Tepavac, 2002 ; Pepin et al, 2003 ; Nooijen et al, 2009 ; Awai and Curt, 2014 ; Sohn et al, 2018 ; Ardestani et al, 2019 ). Both stride frequency and stride length are coupled to walking speed modulation in non-injured adults ( van Hedel et al, 2006 ).…”