Effects of unilateral robotic limb loading on gait characteristics in subjects with chronic stroke

Abstract

BackgroundHemiparesis after stroke often leads to impaired ankle motor control that impacts gait function. In recent studies, robotic devices have been developed to address this impairment. While capable of imparting forces to assist during training and gait, these devices add mass to the paretic leg which might encumber patients' gait pattern. The purpose of this study was to assess the effects of the added mass of one of these robots, the MIT's Anklebot, while unpowered, on gait of chronic stroke survivors during overground and treadmill walking.MethodsNine chronic stroke survivors walked overground and on a treadmill with and without the anklebot mounted on the paretic leg. Gait parameters, interlimb symmetry, and joint kinematics were collected for the four conditions. Repeated-measures analysis of variance (ANOVA) tests were conducted to examine for possible differences across four conditions for the paretic and nonparetic leg.ResultsThe added inertia and friction of the unpowered anklebot had no statistically significant effect on spatio-temporal parameters of gait, including paretic and nonparetic step time and stance percentage, in both overground and treadmill conditions. Noteworthy, interlimb symmetry as characterized by relative stance duration was greater on the treadmill than overground regardless of loading conditions. The presence of the unpowered robot loading reduced the nonparetic knee peak flexion on the treadmill and paretic peak dorsiflexion overground (p < 0.05).ConclusionsOur results suggest that for these subjects the added inertia and friction of this backdriveable robot did not significantly alter their gait pattern.

Measurement of passive ankle stiffness in subjects with chronic hemiparesis using a novel ankle robot

“…It has low friction (0.744 N·m) and inertia (0.8 kg per actuator for a total of 1.6 kg at the foot) to maximize the backdriveability. A previous study has shown that unilaterally loading the impaired leg with the additional mass of the anklebot had no detrimental effect on the gait pattern in subjects with chronic hemiparesis (Khanna et al 2010).…”

Short-term ankle motor performance with ankle robotics training in chronic hemiparetic stroke

“…* The anklebot can estimate ankle kinematics and kinetics with a very high degree of precision [19] and can be used as an effective clinical measurement instrument in estimating paretic ankle stiffness [21][22]. Walking with the unpowered anklebot as an added mass on the paretic leg does not interfere or significantly alter gait kinematics [23].…”

Assist On-Ankle: a reconfigurable ankle exoskeleton with series-elastic actuation

“…Weight can further be distributed over the body by suspending the device with shoulder strap, running up over the shoulder and neck, as in Roy et al (2007). Please note, it has been shown in the literature that, unilaterally loading the impaired leg of chronic hemiparesis patients with an additional mass of 3.6 kg due to an ankle rehabilitation device does not cause detrimental effects on the gait pattern of subjects (Khanna et al 2010). Table 2 lists the specifications of the device in both modes.…”