Enhancing robotic gait training via augmented feedback.

Recent work has examined the feasibility of robotic-assisted gait training in pediatric patients, including children with cerebral palsy (CP). Herein we present a case series describing clinical outcomes in four children with CP who underwent gait training using a robotic driven gait orthosis (DGO) (Pediatric Lokomat©). Children had a diagnosis of spastic diplegia due to CP. They were paired based on functional abilities and observed gait characteristics. Two children had a GMFCS of III and showed excessive ankle plantarflexion during stance. The other two children had a GMFCS of II and displayed a crouch gait pattern. Each subject participated in a 6-week intervention of robotic-assisted gait training that involved three 30-minute sessions per week. Pre-and post-training evaluations were performed including clinical tests of standing and walking function, walking speed, and walking endurance. Clinical gait analysis was also performed using a motion capture system to assess changes in gait mechanics. All subjects showed an improvement in locomotor function. For lower functioning children, this may be mediated by improved trunk control. The use of augmented feedback was associated with larger. However, these results have to be considered with caution because of the limited sample size of the study.

Multicenter randomized clinical trial evaluating the effectiveness of the Lokomat in subacute stroke.

OBJECTIVE: To compare the efficacy of robotic-assisted gait training with the Lokomat to conventional gait training in individuals with subacute stroke. METHODS: A total of 63 participants<6 months poststroke with an initial walking speed between 0.1 to 0.6 m/s completed the multicenter, randomized clinical trial. All participants received twenty-four 1-hour sessions of either Lokomat or conventional gait training. Outcome measures were evaluated prior to training, after 12 and 24 sessions, and at a 3-month follow-up exam. Self-selected overground walking speed and distance walked in 6 minutes were the primary outcome measures, whereas secondary outcome measures included balance, mobility and function, cadence and symmetry, level of disability, and quality of life measures. RESULTS: Participants who received conventional gait training experienced significantly greater gains in walking speed (P=.002) and distance (P=.03) than those trained on the Lokomat. These differences were maintained at the 3-month follow-up evaluation. Secondary measures were not different between the 2 groups, although a 2-fold greater improvement in cadence was observed in the conventional versus Lokomat group. CONCLUSIONS: For subacute stroke participants with moderate to severe gait impairments, the diversity of conventional gait training interventions appears to be more effective than robotic-assisted gait training for facilitating returns in walking ability.

Quantification of reflex activity in stroke survivors during an imposed multi-joint leg extension movement.

The goal of this study was to compare short- and long-latency reflex responses in eight major lower-extremity muscle groups following an imposed multi-joint leg movement between a group of 14 chronic (>1 year) stroke survivors and 10 healthy age-matched controls, and to investigate the influence of joint velocities and muscle excitation levels on these reflex responses in each respective group. Subjects were seated with their foot anchored to a sliding footplate that could extend their leg. Prior to the leg being moved, subjects were instructed to pre-activate hip and knee flexors and extensors. Feedback of joint torque was used to help subjects activate muscles over a range of excitation levels. Following pre-activation, the subject's leg was passively extended so the knee or hip joint rotated at one of three different speeds (30, 60, and 120 degrees /s). In general, it was found that the magnitude of stroke survivors' reflex response was greater compared to controls' in certain biarticular muscles, notably the gastrocnemius and medial hamstring, and the uniarticular adductor longus, and that the long-latency reflex component (between 40 and 150 ms post-movement) accounted for most of the observed differences. Furthermore, while reflex response amplitudes increased in both groups with increasing movement speed, the rate of increase was significantly larger in stroke subjects than in controls. Clinically, these findings may help explain why stroke survivors walk slowly since it is under these conditions that reflex responses better emulate those of their able-bodied counterparts.

Quantification of functional weakness and abnormal synergy patterns in the lower limb of individuals with chronic stroke.

BACKGROUND: The presence of abnormal muscle activation patterns is a well documented factor limiting the motor rehabilitation of patients following stroke. These abnormal muscle activation patterns, or synergies, have previously been quantified in the upper limbs. Presented here are the lower limb joint torque patterns measured in a standing position of sixteen chronic hemiparetic stroke subjects and sixteen age matched controls used to examine differences in strength and coordination between the two groups. METHODS: With the trunk stabilized, stroke subjects stood on their unaffected leg while their affected foot was attached to a 6-degree of freedom load cell (JR3, Woodland CA) which recorded forces and torques. The subjects were asked to generate a maximum torque about a given joint (hip abduction/adduction; hip, knee, and ankle flexion/extension) and provided feedback of the torque they generated for that primary joint axis. In parallel, EMG data from eight muscle groups were recorded, and secondary torques generated about the adjacent joints were calculated. Differences in mean primary torque, secondary torque, and EMG data were compared using a single factor ANOVA. RESULTS: The stroke group was significantly weaker in six of the eight directions tested. Analysis of the secondary torques showed that the control and stroke subjects used similar strategies to generate maximum torques during seven of the eight joint movements tested. The only time a different strategy was used was during maximal hip abduction exertions where stroke subjects tended to flex instead of extend their hip, which was consistent with the classically defined "flexion synergy." The EMG data of the stroke group was different than the control group in that there was a strong presence of co-contraction of antagonistic muscle groups, especially during ankle flexion and ankle and knee extension. CONCLUSION: The results of this study indicate that in a standing position stroke subjects are significantly weaker in their affected leg when compared to age-matched controls, yet showed little evidence of the classic lower-limb abnormal synergy patterns previously reported. The findings here suggest that the primary contributor to isometric lower limb motor deficits in chronic stroke subjects is weakness.

Advances in the understanding and treatment of stroke impairment using robotic devices.

The presence of robotic devices in rehabilitation centers is now becoming commonplace across the world, challenging heath care professionals to rethink treatment strategies for motor impairment in hemiparetic stroke patients. In this article, we will discuss some of the motivations for using these devices, review clinical outcomes following robotic-assisted training in both the upper and lower extremities, and detail how these devices can provide quantitative evaluations of function. We will also address the clinical issues that need to be considered when using robotic devices to treat stroke patients, and finally a vision of where this field is heading will be discussed.