A neuromechanics-based powered ankle exoskeleton to assist walking post-stroke: a feasibility study

Takahashi, Kota; Lewek, Michael D.; Sawicki, Gregory S.

doi:10.1186/s12984-015-0015-7

Cited by 123 publications

(116 citation statements)

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“…In general terms, the kinematic results during the first use of the T-FLEX actuation system showed improvements in some participants (i.e., increase foot clearance, and early push-off), which are similar to a robust AAFO based on pneumatic actuation [31]. Additionally, these results are comparable to devices controlled by Force Sensitive Resistor (FSR) for gait detection [32,33] that is the most common detection strategy used in wearable robotic orthoses.…”

Section: Discussionmentioning

confidence: 64%

Actuation system of the ankle exoskeleton T-FLEX: first use experimental validation in people with stroke

Gomez-Vargas

Ballén-Moreno

Barria³

et al. 2020

Preprint

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Abstract Background: Robotic devices can provide physical assistance to people who have suffered neurological impairments such as stroke. Neurological disorders related to this condition induce abnormal gait patterns, which harm the independence to execute different Activities of Daily Living (ADL). From the fundamental role of the ankle in walking, Active Ankle-Foot Orthoses (AAFOs) have been developed to enhance the users' gait patterns, and hence, their quality of life.Methods: Ten patients who suffered stroke used the actuation system of the T-FLEX orthosis triggered by an inertial sensor on the foot tip. The VICON motion capture system recorded the users' kinematics for unassisted and assisted gait modalities. Biomechanical analysis and usability assessment measured the performance of the system actuation for the participants in overground walking. Results: The biomechanical assessment exhibited changes in the range of motion of the lower joints for $70\%$ of the subjects. Moreover, the ankle kinematics showed a correlation with the variation of other movements analyzed. This variation had positive effects on 70\% of the participants in at least one joint. The Gait Deviation Index (GDI) presented significant changes for 30\% of the paretic limbs, where one volunteer increased this index in 14\%. The spatiotemporal parameters did not show significant variations between modalities, although users' cadence had a decrease. Lastly, the satisfaction with the device was positive, being the comfort the most users-selected aspect.Conclusions: This article presented the assessment of the T-FLEX actuation system in people who suffered stroke. Biomechanical results showed improvement in the ankle kinematic and variation in the other joints. In general terms, GDI did not exhibit significant changes, and Movement Analysis Profile (MAP) registered the main movements altered by the device. Future works should focus on assessing the full T-FLEX orthosis in a larger sample of patients that includes a stage of training.Trial registration: This study was registered as Preliminary Biomechanical and Usability Study of an Active Ankle-Foot Orthosis for Stroke Survivors on 30 January 2020 in Clinical Trials with the identi er No NCT04249349 (available at https://clinicaltrials.gov/ct2/show/NCT04249349).

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Section: Discussionmentioning

confidence: 64%

Actuation system of the ankle exoskeleton T-FLEX: first use experimental validation in people with stroke

Gomez-Vargas

Ballén-Moreno

Barria³

et al. 2020

Preprint

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“…Although this study presents a comprehensive analysis of exosuitinduced changes in post-stroke gait mechanics and energetics, it is limited by a small sample size. However, comparable sample sizes have been used successfully to evaluate other wearable assistive devices (Collins et al, 2015;Malcolm et al, 2013;Mooney et al, 2014;Takahashi et al, 2015) and we believe that the findings of this study provide a meaningful step toward understanding how individuals after stroke utilize robotic ankle assistance to achieve a more economical gait. Another limitation is that this investigation focused on the effects of walking with an exosuit worn unpowered versus powered.…”

Section: Discussionmentioning

confidence: 89%

“…A major contributor to post-stroke walking deficits is impaired paretic ankle function, specifically during the push-off and swing phases of the gait cycle. During push-off, impaired paretic ankle plantarflexion (PF) (Chen et al, 2005;Olney et al, 1991;Peterson et al, 2010) reduces the paretic limb's contribution to forward propulsion (Mahon et al, 2015;Takahashi et al, 2015). During swing phase, impaired paretic ankle dorsiflexion (DF) contributes to impaired ground clearance by the paretic limb, increasing the risk of falling (Weerdesteyn et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

“…PF or DF) based on the desired biomechanical response. Active ankle assistive devices include functional electrical stimulation (Kottink et al, 2004;Lynch and Popovic, 2008) and robotic mechanical assistive devices (Díaz et al, 2011;Shorter et al, 2011;Takahashi et al, 2015). Previous studies using such devices have shown improved paretic ankle function and reduced gait impairment Forrester et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Biomechanical mechanisms underlying exosuit-induced improvements in walking economy after stroke

Bae

Awad

Long

et al. 2018

Journal of Experimental Biology

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Stroke-induced hemiparetic gait is characteristically asymmetric and metabolically expensive. Weakness and impaired control of the paretic ankle contribute to reduced forward propulsion and ground clearance - walking subtasks critical for safe and efficient locomotion. Targeted gait interventions that improve paretic ankle function after stroke are therefore warranted. We have developed textile-based, soft wearable robots that transmit mechanical power generated by off-board or body-worn actuators to the paretic ankle using Bowden cables (soft exosuits) and have demonstrated the exosuits can overcome deficits in paretic limb forward propulsion and ground clearance, ultimately reducing the metabolic cost of hemiparetic walking. This study elucidates the biomechanical mechanisms underlying exosuit-induced reductions in metabolic power. We evaluated the relationships between exosuit-induced changes in the body center of mass (COM) power generated by each limb, individual joint power and metabolic power. Compared with walking with an exosuit unpowered, exosuit assistance produced more symmetrical COM power generation during the critical period of the step-to-step transition (22.4±6.4% more symmetric). Changes in individual limb COM power were related to changes in paretic (=0.83, 0.004) and non-paretic (0.73, 0.014) ankle power. Interestingly, despite the exosuit providing direct assistance to only the paretic limb, changes in metabolic power were related to changes in non-paretic limb COM power (=0.80, 0.007), not paretic limb COM power (0.05). These findings contribute to a fundamental understanding of how individuals post-stroke interact with an exosuit to reduce the metabolic cost of hemiparetic walking.

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“…Despite the importance of propulsion to a functional bipedal gait, conventional rehabilitation efforts have, by and large, been unable to restore propulsion function after neurological injury or dysfunction. The development and study of interventions that target propulsion function is a highly active area of research 12,[33][34][35][36][37][38][39][40][41] ; however, the clinical translation of these experimental approaches is hindered by the limited access that rehabilitation clinicians have to the sophisticated in-strumentation (i.e., forceplates and instrumented treadmills) and personnel with advanced training required to collect, analyze, and interpret ground reaction force data. Moreover, even in settings with access to a motion analysis laboratory, locomotor differences inherent to treadmill walking and the small collection footprint of most overground forceplate walkways limit ecological validity.…”

mentioning

confidence: 99%

Indirect measurement of anterior-posterior ground reaction forces using a minimal set of wearable inertial sensors: From healthy to hemiparetic walking

Revi

Alvarez

Walsh

et al. 2020

Preprint

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Abstract Background: The anterior-posterior ground reaction force (AP-GRF) and propulsion and braking metrics derived from the AP-GRF time series are indicators of locomotor function across healthy and neurological diagnostic groups. In this paper, we describe the use of a minimal set of wearable inertial measurement units (IMUs) to indirectly measure the AP-GRFs generated during healthy and hemiparetic walking. Methods: Ten healthy individuals and five individuals with chronic post-stroke hemiparesis completed a 6-minute walk test over a walking track instrumented with six forceplates while wearing three IMUs securely attached to the pelvis, thigh, and shank. Subject-specific models driven by IMU-measured thigh and shank angles and an estimate of body acceleration provided by the pelvis IMU were used to generate indirect estimates of the AP-GRF time series. Propulsion and braking point metrics (i.e., peaks, peak timings, and impulses) were extracted from the IMU-generated time series. Peaks and impulses were expressed as % bodyweight (%bw) and peak timing was expressed as % stance phase (%sp). A 75%-25% split of 6-minute walk test data was used to train and validate the models. Indirect estimates of the AP-GRF time series and point metrics were compared to direct measurements of the same made by the reference standard forceplates. Results: Indirect measurements of the AP-GRF time series strongly approximated the direct measurements made by forceplates, with low error and high consistency in both the healthy (RMSE = 4.5 %bw; R2 = 0.93) and post-stroke (RMSE = 2.65 %bw; R2 = 0.90) cohorts. In the healthy cohort, the average errors between indirect and direct measurements of the peak propulsion magnitude, peak propulsion timing, and propulsion impulse point estimates were 2.37 %bw, 0.67 %sp, and 0.43 %bw. In the post-stroke cohort, the average errors for these same point estimates were 1.07 %bw, 1.27 %sp, and 0.31 %bw. Average errors for the braking-related point estimates were higher, but comparable. Conclusions: Accurate estimates of the AP-GRF time series and key propulsion and braking point metrics can be generated using three strategically mounted IMUs and subject-specific calibrations. This study is a foundational step toward the development of point-of-care diagnostic systems that can catalyze the routine assessment and management of propulsion and braking locomotor deficits during rehabilitation.

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A neuromechanics-based powered ankle exoskeleton to assist walking post-stroke: a feasibility study

Cited by 123 publications

References 67 publications

Actuation system of the ankle exoskeleton T-FLEX: first use experimental validation in people with stroke

Actuation system of the ankle exoskeleton T-FLEX: first use experimental validation in people with stroke

Biomechanical mechanisms underlying exosuit-induced improvements in walking economy after stroke

Indirect measurement of anterior-posterior ground reaction forces using a minimal set of wearable inertial sensors: From healthy to hemiparetic walking

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