Abstract
Background: Gait analysis studies during robot-assisted walking have been predominantly focused on lower limb biomechanics. During robot-assisted walking, the users' interaction with the robot and their adaptations translate into altered gait mechanics. Hence, robust and objective metrics for quantifying walking performance during robot-assisted gait are especially relevant as it relates to dynamic stability. In this study, we assessed bi-planar dynamic stability margins for healthy adults during robot-assisted walking using EksoGT™, ReWalk™, and Indego® compared to independent overground walking at slow, self-selected, and fast speeds. Further, we examined the use of forearm crutches and its influence on dynamic gait stability margins.Methods: Kinematic data were collected at 60 Hz under several walking conditions with and without the robotic exoskeleton for six healthy controls. Outcome measures included (i) whole-body center of mass (CoM) and extrapolated CoM (XCoM), (ii) base of support (BoS), (iii) margin of stability (MoS) with respect to both feet and bilateral crutches.Results: Stability outcomes during exoskeleton-assisted walking at self-selected, comfortable walking speeds were significantly (p < 0.05) different compared to overground walking at self-selected speeds. Unlike overground walking, the control mechanisms for stability using these exoskeletons were not related to walking speed. MoSs were lower during the single support phase of gait, especially in the medial–lateral direction for all devices. MoSs relative to feet were significantly (p < 0.05) lower than those relative to crutches. The spatial location of crutches during exoskeleton-assisted walking pushed the whole-body CoM, during single support, beyond the lateral boundary of the lead foot, increasing the risk for falls if crutch slippage were to occur.Conclusion: Careful consideration of crutch placement is critical to ensuring that the margins of stability are always within the limits of the BoS to control stability and decrease fall risk.
Highlights
Available exoskeletons, such as the EksoGTTM (Ekso Bionics, Richmond, CA), ReWalkTM (ReWalk Robotics, Inc., Marlborough, MA), and Indego R (Parker Hannifin Corp, Cleveland, OH), are suggested rehabilitative modalities for overground (OG) walking among individuals with movement limitations (U.S Food Drug Administration, 2014, 2016a,b, 2017)
Researchers have studied the kinematic, spatiotemporal, cardiopulmonary, cognitive, neuromuscular, and safety outcomes associated with robotic exoskeleton (RE) training (Nozaki et al, 2005; Sayenko et al, 2015; Miller et al, 2016; Ramanujam et al, 2017, 2018, 2019a; Saleh et al, 2017; Gordon et al, 2018; Tefertiller et al, 2018; Forrest et al, 2019; Guanziroli et al, 2019; Khan et al, 2019; Luger et al, 2019; Momeni et al, 2019; Wang et al, 2019; Yildirim et al, 2019; McIntosh et al, 2020), a thorough assessment of dynamic stability during RE walking is important to understanding the mechanics of human–machine interactions during exoskeleton-assisted gait and the potential to lower fall risk
At heel-strike during RE walking across all tested devices and conditions, the overall mean margin of stability (MoS) calculated using the base of support (BoS) defined by the bilateral crutches (MoSML = 0.56 ± 0.09 m; MoSAP = 0.31 ± 0.08 m) were significantly (p < 0.05) greater than OG walking (MoSML = 0.11 ± 0.03 m; MoSAP = 0.06 ± 0.17 m) across all speeds in both directions (Figure 2A)
Summary
Available exoskeletons, such as the EksoGTTM (Ekso Bionics, Richmond, CA), ReWalkTM (ReWalk Robotics, Inc., Marlborough, MA), and Indego R (Parker Hannifin Corp, Cleveland, OH), are suggested rehabilitative modalities for overground (OG) walking among individuals with movement limitations (U.S Food Drug Administration, 2014, 2016a,b, 2017). Walking using these exoskeletons requires assistive devices like bilateral canes, forearm crutches, or a walker; these assistive devices can inhibit dynamic stability (Bateni and Maki, 2005; Saunders et al, 2013). We examined the use of forearm crutches and its influence on dynamic gait stability margins
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