Power-free knee rehabilitation robot for home-based isokinetic training

Robot-assisted isokinetic training has been widely adopted for knee rehabilitation. However, existing rehabilitation facilities are often heavy, bulky, and extremely energy-consuming, which limits the rehabilitation opportunities only at designated hospitals. In this study, we introduce a highly integrated and lightweight (52 kg) knee rehabilitation robot that can provide home-based isokinetic training without external power. By integrating a motor, torque/angle sensors, control circuit, and energy regeneration circuit into a single driver module, our robot can provide power-free isokinetic training by recycling mechanical work from the trainee. Ten postsurgical subjects were involved in an interventional randomized trial (ChiCTR2300076715, Part I) and the cross-sectional area of trained legs (experimental group) was significantly higher than that of untrained legs (control group). The primary outcomes, muscle growth (quadriceps: 5.93%, hamstrings: 10.27%) and strength improvements (quadriceps: 70%, hamstrings: 84%), achieved with our robots surpass those of existing commercial rehabilitation devices. These findings indicate that our robot presents a viable option for home-based knee rehabilitation, significantly enhancing the accessibility of effective treatment.

A randomized cross-over study protocol to evaluate long-term gait training with a pediatric robotic exoskeleton outside the clinical setting in children with movement disorders

Individuals with neuromuscular disorders display a combination of motor control deficits and lower limb weakness contributing to knee extension deficiency characterized by exaggerated stance phase knee flexion. There is a lack of evidence for long-term improvement of knee extension deficiency with currently available clinical treatment programs. Our previous work testing a wearable robotic exoskeleton with precisely timed assistive torque applied at the knee showed immediate increases in knee extension during walking for children with cerebral palsy, which continued to improve over an acute practice period. When we applied interleaved assistance and resistance to knee extension, we observed improvements in knee extension and increased muscle activation indicating the potential for muscle strengthening when used over time. There is a need for additional, high-quality trials to assess the impact of dosage, intensity and volume of training necessary to see persistent improvement in lower limb function for these patient populations. This randomized crossover study (ClinicalTrials.gov: NCT05726591) was designed to determine whether 12 weeks of overground gait training with a robotic exoskeleton outside of the clinical setting, following an initial in clinic accommodation period, has a beneficial effect on walking ability, muscle activity and overall motor function. Participants will be randomized to either complete the exoskeleton intervention or continue their standard therapy for 12 weeks first, followed by a crossover to the other study component. The primary outcome measure is change in peak knee extension angle during walking; secondary outcome measures include gait speed, strength, and validated clinical scales of motor function and mobility. Assessments will be completed before and after the intervention and at 6 weeks post-intervention, and safety and compliance will be monitored throughout. We hypothesize that the 12-week exoskeleton intervention outside the clinical setting will show greater improvements in study outcome measures than the standard therapy.

Hip Exoskeleton Based Trans-multi-articular Gait Intervention: Preliminary Study on Achilles Tendon Rehabilitation

The rupture of the Achilles Tendon (AT) is a prevalent affliction among athletic populations. The patients who process AT repair frequently exhibit a deficit in the activation and strength of the gastrocnemius muscle. The exoskeleton can help with the patients gait training, especially perform effectively interventions during walking. However, the ankle exoskeleton is not suitable for acute-phase gait training, and the knee exoskeleton may have the possibility of downward migration. To address this issue and facilitate the early-stage rehabilitation of the gastrocnemius, this paper proposes a trans-multi-articular gait intervention strategy. Preliminary study on healthy subjects suggests that the implementation of extension resistance during the hip extension phase of the gait cycle can contribute to an increment in the strength of the ankle plantar flexion muscle. Future research will focus on the effectiveness of the proposed therapy strategy in practical application to patients.

Resist-as-Needed ADL Training With SPINDLE for Patients With Tremor

Individuals with neurological disorders often exhibit altered manual dexterity and muscle weakness in their upper limbs. These motor impairments with tremor lead to severe difficulties in performing Activities of Daily Living (ADL). There is a critical need for ADL-focused robotic training that improves individual's strength when engaging with dexterous ADL tasks. This research introduces a new approach to training ADLs by employing a novel robotic rehabilitation system, Spherical Parallel INstrument for Daily Living Emulation (SPINDLE), which incorporates Virtual Reality (VR) to simulate ADL tasks. The study results present the feasibility of training individuals with movements similar to ADLs while interacting with the SPINDLE. A new game-based robotic training paradigm is suggested to perform ADL tasks at various intensity levels of resistance as needed. The proposed system can facilitate the training of various ADLs requiring 3-dimensional rotational movements by providing optimal resistance and visual feedback. We envision this system can be utilized as a table-top home device by restoring the impaired motor function of individuals with tremor and muscle weakness, guiding to improved ADL performance and quality of life.

Walking on Real-world Terrain with an Ankle Exoskeleton in Cerebral Palsy

Despite medical treatment focused on addressing walking disability, many millions of people with neurological conditions, like cerebral palsy (CP), struggle to maintain independent mobility. Lower limb exoskeletons and exosuits may hold potential for augmenting walking ability. However, it remains unknown whether these wearable robots are safe and beneficial for use outside of highly controlled laboratory environments, the demonstration of which is necessary for clinical translation. Here, we show that a lightweight, portable, ankle exoskeleton with an adaptable one-size-works-for-all assistance controller can improve energy efficiency and walking speed for individuals with CP spanning a wide spectrum of lower limb impairment in a multi-terrain real-world environment. Tested on an outdoor walking route with level, sloped, and stair terrain, robotic assistance resulted in a 15-18% (p = 0.013-0.026) reduction in estimated energy cost and a 7-8% (p = 0.001-0.004) increase in average walking speed across "shorter" 6-minute and "longer" 20-minute walking durations relative to unassisted walking. This study provides evidence that wearable robots may soon improve mobility in neighborhood, school, and community settings for individuals with CP.

Factors influencing neuromuscular responses to gait training with a robotic ankle exoskeleton in cerebral palsy

A current limitation in the development of robotic gait training interventions is understanding the factors that predict responses to treatment. The purpose of this study was to explore the application of an interpretable machine learning method, Bayesian Additive Regression Trees (BART), to identify factors influencing neuromuscular responses to a resistive ankle exoskeleton in individuals with cerebral palsy (CP). Eight individuals with CP (GMFCS levels I - III, ages 12-18 years) walked with a resistive ankle exoskeleton over seven visits while we measured soleus activation. A BART model was developed using a predictor set of kinematic, device, study, and participant metrics that were hypothesized to influence soleus activation. The model (R2 = 0.94) found that kinematics had the largest influence on soleus activation, but the magnitude of exoskeleton resistance, amount of gait training practice with the device, and participant-level parameters also had substantial effects. To optimize neuromuscular engagement during exoskeleton training in individuals with CP, our analysis highlights the importance of monitoring the user's kinematic response, in particular, peak stance phase hip flexion and ankle dorsiflexion. We demonstrate the utility of machine learning techniques for enhancing our understanding of robotic gait training outcomes, seeking to improve the efficacy of future interventions.

Hip Exoskeleton Based Indirect Intervention Strategy Towards Gait Training After Total Knee Arthroplasty

Total Knee Arthroplasty (TKA) is the most effective approach for function restoration in patients with severe knee osteoarthritis. However, kinematic, kinetic and muscle activation differences between post-TKA patients and healthy people can be observed in many studies. Exoskeletons have been applied to post-TKA rehabilitation for many years, while few studies concentrated on the stance phase abnormality, neither in the aspect of kinematics nor in muscle activation. In this paper, we propose an indirect resistance strategy for post-operative TKA patient gait training. Three healthy subjects were asked to wear the hip exoskeleton and provided with 8 N·m resistance on the hip extension phase of the gait cycle. The intervention leads to an increment in the knee extension muscle activity as well as the augmentation in maximum knee angle in loading response. The results indicated that the application of resistance in the hip extension phase is a potential therapeutic approach for post-TKA rehabilitation, and may increase the gait training efficiency in the near future.

Design and Implementation of a Portable Knee Actuator for the Improvement of Crouch Gait in Children with Cerebral Palsy

Common manifestation of spastic Cerebral Palsy (CP) are abnormal gait pathologies. These conditions require greater energy expenditure to successfully ambulate and are linked with significant deterioration in joint health and childhood musculoskeletal development. Crouch gait presents with knee hyperflexion throughout stance due to extensor muscle weakness and spasticity in flexor muscles stemming from neurological damage. The goal of this study was to develop a wearable cable-driven robotic system that applies controlled perturbation to the knee joint during overground walking in children with CP. Two children with spastic CP were recruited in this pilot study. They were tested in two conditions, i.e., applying knee resistance vs. knee assistance during overground walking. Kinematic and EMG data were recorded during overground walking. Data indicated that it was feasible to apply controlled knee perturbation torque during overground walking in children with crouch and preliminary results showed an improvement in crouch gait pattern in children with CP after one session of walking with the robotic system.Clinical Relevance- This study might have a potential clinical significance modifying neuromuscular control of CP patients with Crouch Gait.

The Use of the 6MWT for Rehabilitation in Children with Cerebral Palsy: A Narrative Review

Assessing and improving walking abilities is considered one of the most important functional goals of physical therapy in children with cerebral palsy. However, there is still a gap in knowledge regarding the efficacy of treatment targeting the walking capacity of children with CP, as well as their responsiveness to the treatment. The 6 min walk test (6MWT) is a reliable tool to measure this function in children with CP, although less has been known about its potential efficacy to assess changes in the walking abilities associated with interventions. The aim of the present narrative review is to increase the amount of knowledge regarding the use of the 6MWT as a reliable measure to evaluate the effect of interventions on walking capacity in children with CP.

Passive Exoskeleton with Gait-Based Knee Joint Support for Individuals with Cerebral Palsy

Cerebral palsy is a neurological disorder with a variety of symptoms that can affect muscle coordination and movement. Crouch gait is one such symptom that is defined as excessive knee flexion accompanied by a crouched posture. This paper introduces a passive exoskeleton to support the knee joint during stance of individuals with cerebral palsy that are affected by crouch gait. The exoskeleton utilizes a hydraulic disc brake mechanism that is actuated only by the body weight and gait of the wearer to provide a braking torque at the knee joint. This passive, gait-based control method aims to offer a compact, lightweight, and simple alternative to existing exoskeletons. Preliminary experiments were conducted to verify the mechanics, safety, and braking capabilities of the device with healthy participants. A pilot study with an individual with cerebral palsy was then conducted. The individual with cerebral palsy showed a reduction in hip joint angle when using the device (18.8∘ and 21.7∘ for left and right sides, respectively). The muscle co-activation index was also reduced from 0.48 to 0.24 on the right side and from 0.17 to 0.017 on the left side. However, changes such as activation timing and device training need to be improved to better support the user.

Effectiveness of a wearable ankle-tubing gait training on ankle kinematics and motor control in hemiparetic stroke

BACKGROUND: While excessive ankle plantarflexion is a common neuromuscular impairment resulting from insufficient coordination of selective ankle neuromotor control and kinematics during gait. We recently developed a wearable, inexpensive and sustainable wearable ankle-tubing gait training (WAGT) aimed at improving selective ankle motor control and kinematic coordination. OBJECTIVE: We investigated the effects of WAGT on tibialis anterior (TA) and gastrocnemius (GCM) muscle electromyography (EMG) activity, TA: GCM muscle imbalance ratio, and ankle joint kinematics during gait in hemiparetic stroke patients. METHODS: A convenience sample of 33 participants (15 non-stroke healthy adults and 18 hemiparetic stroke patients) underwent standardized electromyography and kinematic biomechanical tests under conventional gait training (CGT) and WAGT conditions. Analysis of variance (ANOVA) was used to determine the significance of differences in the TA: GCM muscle activation, muscle imbalance ratio, and ankle joint kinematics before and after the intervention and between the two groups at P < 0.05. RESULTS: WAGT was more effective than CGT in improving TA muscle activation (P < 0.01), TA: GCM muscle imbalance ratio (P < 0.01), and kinematic movement (P < 0.01) in adults with or without hemiparetic stroke. CONCLUSIONS: This study demonstrated that WAGT is relatively ease to design, wear and affordable to most clinicians and patients, hence it is suitable for many health care applications to correct gait-related movement abnormalities presented in the hemiparetic stroke patients.

Soleus H-reflex modulation in cerebral palsy and its relationship with neural control complexity: a pilot study

Individuals with cerebral palsy (CP) display motor control patterns that suggest decreased supraspinal input, but it remains unknown if they are able to modulate lower-limb reflexes in response to more complex tasks, or whether global motor control patterns relate to reflex modulation capacity in this population. Eight ambulatory individuals with CP (12-18 years old) were recruited to complete a task complexity protocol, where soleus H-reflex excitability was compared between bilateral (baseline) and unilateral (complex) standing. We also investigated the relationship between each participant's ability to modulate soleus H-reflex excitability and the complexity of their walking neural control pattern determined from muscle synergy analysis. Finally, six of the eight participants completed an exoskeleton walking protocol, where soleus H-reflexes were collected during the stance phase of walking with and without stance-phase plantar flexor resistance. Participants displayed a significant reduction in soleus H-reflex excitability (- 26 ± 25%, p = 0.04) with unilateral standing, and a strong positive relationship was observed between more refined neural control during walking and an increased ability to modulate reflex excitability (R = 0.79, p = 0.04). There was no difference in neuromuscular outcome measures with and without the ankle exoskeleton (p values all > 0.05), with variable reflex responses to walking with ankle exoskeleton resistance. These findings provide evidence that ambulatory individuals with CP retain some capacity to modulate lower-limb reflexes in response to increased task complexity, and that less refined neural control during walking appears to be related to deficits in reflex modulation.

Interleaved Assistance and Resistance for Exoskeleton Mediated Gait Training: Validation, Feasibility and Effects

Strength and selective motor control are primary determinants of pathological gait in children with cerebral palsy (CP) and other neuromotor disorders. Emerging evidence suggests robotic application of task-specific resistance to functional movements may provide the opportunity to strengthen muscles and improve neuromuscular function during walking in children with CP. Such a strategy could be most beneficial to children who are more severely affected by the pathology but their ability to overcome such resistance and maintain functional ambulation remains unclear. The goal of this study was to design, validate and evaluate initial feasibility and effects of a novel exoskeleton strategy that provides interleaved assistance and resistance to knee extension during overground walking. One participant with CP (GMFCS III) was recruited and completed ten total visits, nine walking with the exoskeleton. Our results validated the controller's ability to parse the gait cycle into five discrete phases (mean accuracy 91%) and provide knee extension assistance during stance and resistance during swing. Following acclimation to the interleaved strategy, peak knee extension was significantly improved in both the left (mean 7.9 deg) and right (15.2 deg) limbs when walking with the exoskeleton. Knee extensor EMG during late swing phase increased to 2.7 (left leg) and 1.7 (right leg) times the activation level during baseline exoskeleton walking without resistance. These results indicate that this interleaved strategy warrants further investigation in a longitudinal intervention study, particularly in individuals who may be more severely affected such that they are unable to ambulate overground using an exoskeleton training strategy that only deploys targeted resistance to limb motion.

Is robotic gait training effective for individuals with cerebral palsy? A systematic review and meta-analysis of randomized controlled trials

AIM

To determine if robotic gait training for individuals with cerebral palsy is more effective than the standard of care for improving function.

METHOD

PubMed, Embase, Scopus, and Cochrane databases were searched from 1980-January, 2022 for articles that investigated robotic gait training versus standard of care (i.e. physical therapy or standard gait training) for individuals with cerebral palsy. Articles were included if a randomized controlled trial design was used, and excluded if robotic gait training was combined with another neuromuscular intervention, such as functional electrical stimulation. A meta-analysis of outcomes measured in at least four studies was conducted.

RESULTS

Eight citations met all criteria for full-text review and inclusion in the meta-analysis. A total of 188 individuals with cerebral palsy, ages four to 35, and Gross Motor Function Classification System levels I-IV were studied. Level of evidence ranged from 2b-1b. All studies utilized a tethered, assistive device for robotic gait training. The overall effect was not significantly different between the robotic gait training and control interventions for six minute walk test performance (95% CI: -0.17, 0.73; P = 0.22), free walking speed (95% CI: -0.18, 0.57; P = 0.30), or Gross Motor Function Measures D (Standing) (95% CI: -0.29, 0.39; P = 0.77) and E (Walking, Running and Jumping) (95% CI: -0.11, 0.57; P = 0.19).

CONCLUSION

Tethered robotic devices that provide assistive gait training for individuals with cerebral palsy do not provide a greater benefit for improving mobility than the standard of care.

Adaptive ankle exoskeleton gait training demonstrates acute neuromuscular and spatiotemporal benefits for individuals with cerebral palsy: A pilot study

BACKGROUND

Gait abnormalities from neuromuscular conditions like cerebral palsy (CP) limit mobility and negatively affect quality of life. Increasing walking speed and stride length are essential clinical goals in the treatment of gait disorders from CP.

RESEARCH QUESTION

How does over-ground gait training with an untethered ankle exoskeleton providing adaptive assistance affect mobility-related spatiotemporal outcomes and lower-extremity muscle activity in people with CP?

METHODS

A diverse cohort of individuals with CP (n = 6, age 9-31, Gross Motor Function Classification System Level I - III) completed four over-ground training sessions (98 ± 17 min of assisted walking) and received pre- and post-training assessments. On both assessments, participants walked over-ground with and without the exoskeleton while we recorded spatiotemporal outcomes and muscle activity. We used two-tailed paired t-tests to compare all parameters pre- and post-training, and between assisted and unassisted conditions.

RESULTS

Following training, walking speed increased 0.24 m/s (p = 0.006) and stride length increased 0.17 m (p = 0.013) during unassisted walking, while walking speed increased 0.28 m/s (p = 0.023) and stride length increased 0.15 m (p = 0.002) during exoskeleton-assisted walking. Exoskeleton training improved stride-to-stride repeatability of soleus and vastus lateralis muscle activation by up to 51 % (p ≤ 0.046), while the amount of integrated stance-phase muscle activity was similar across visits and conditions. Relative to baseline, post-training walking with the exoskeleton resulted in a soleus activity pattern that was 39 % more similar to the typical pattern from unimpaired individuals (p < 0.001).

SIGNIFICANCE

This study demonstrates acute spatiotemporal and neuromuscular benefits from over-ground training with adaptive ankle exoskeleton assistance, and provides rationale for completion of a longer randomized controlled training protocol.

A Mobile Cable-Tensioning Platform to Improve Crouch Gait in Children with Cerebral Palsy

Gait impairment represented by crouch gait is the main cause of decreases in the quality of lives of children with cerebral palsy. Various robotic rehabilitation interventions have been used to improve gait abnormalities in the sagittal plane of children with cerebral palsy, such as excessive flexion in the hip and knee joints, yet in few studies have postural improvements in the coronal plane been observed. The aim of this study was to design and validate a gait rehabilitation system using a new cable-driven mechanism applying assist in the coronal plane. We developed a mobile cable-tensioning platform that can control the magnitude and direction of the tension vector applied at the knee joints during treadmill walking, while minimizing the inertia of the worn part of the device for less obstructing the natural movement of the lower limbs. To validate the effectiveness of the proposed system, three different treadmill walking conditions were performed by four children with cerebral palsy. The experimental results showed that the system reduced hip adduction angle by an average of 4.57 ± 1.79° compared to unassisted walking. Importantly, we also observed improvements of hip joint kinematics in the sagittal plane, indicating that crouch gait can be improved by postural correction in the coronal plane. The device also improved anterior and lateral pelvic tilts during treadmill walking. The proposed cable-tensioning platform can be used as a rehabilitation system for crouch gait, and more specifically, for correcting gait posture with minimal disturbance to the voluntary movement.

Development of a Prototype Overground Pelvic Obliquity Support Robot for Rehabilitation of Hemiplegia Gait

In this work, we present the overground prototype gait-rehabilitation robot for using motion assistance and training for paralyzed patients. In contrast to the existing gait-rehabilitation robots, which focus on the sagittal plane motion of the hip and knee, we aim to develop a mobile-based pelvic support gait-rehabilitation system that includes a pelvic obliquity support mechanism and a lower-limb exoskeleton. To achieve this, a scissor mechanism is proposed to generate the paralyzed patient’s pelvic obliquity motion and weight support. Moreover, the lower limb exoskeleton robot is integrated with the developed system to provide the patient’s gait by correcting mechanical aids. We used computer-aided analysis to verify the performance of the prototype hardware itself. Through these methods, it was shown that our motor can sufficiently lift 100 kg of user weight through the scissor mechanism, and that the mobile driving wheel motor can operate at a speed of 1.6 m/s of human walking, showing that it can be used for gait rehabilitation of patients in need of a lower speed. In addition, we verified that the system drives the model by generating pelvic motion, and we verified the position controller of the integrated system, which supports the multi-degree motion by creating hip/knee/pelvic motion with a human dummy mannequin and systems. We believe that the proposed system can help address the complex rehabilitation motion assistance and training of paralyzed patients.

Wearable Lower-Limb Exoskeleton for Children With Cerebral Palsy: A Systematic Review of Mechanical Design, Actuation Type, Control Strategy, and Clinical Evaluation

Children with a neurological disorder such as cerebral palsy (CP) severely suffer from a reduced quality of life because of decreasing independence and mobility. Although there is no cure yet, a lower-limb exoskeleton (LLE) has considerable potential to help these children experience better mobility during overground walking. The research in wearable exoskeletons for children with CP is still at an early stage. This paper shows that the number of published papers on LLEs assisting children with CP has significantly increased in recent years; however, no research has been carried out to review these studies systematically. To fill up this research gap, a systematic review from a technical and clinical perspective has been conducted, based on the PRISMA guidelines, under three extended topics associated with "lower limb", "exoskeleton", and "cerebral palsy" in the databases Scopus and Web of Science. After applying several exclusion criteria, seventeen articles focused on fifteen LLEs were included for careful consideration. These studies address some consistent positive evidence on the efficacy of LLEs in improving gait patterns in children with CP. Statistical findings show that knee exoskeletons, brushless DC motors, the hierarchy control architecture, and CP children with spastic diplegia are, respectively, the most common mechanical design, actuator type, control strategy, and clinical characteristics for these LLEs. Clinical studies suggest ankle-foot orthosis as the primary medical solution for most CP gait patterns; nevertheless, only one motorized ankle exoskeleton has been developed. This paper shows that more research and contribution are needed to deal with open challenges in these LLEs.

A portable exotendon assisting hip and knee joints reduces muscular burden during walking

Assistive devices are used to reduce human effort during locomotion with increasing success. More assistance strategies are worth exploring, so we aimed to design a lightweight biarticular device with well-chosen parameters to reduce muscle effort. Based on the experience of previous success, we designed an exotendon to assist in swing leg deceleration. Then we conducted experiments to test the performance of the exotendon with different spring stiffness during walking. With the assistance of the exotendon, peak activation of semitendinosus decreased, with the largest reduction of 12.3% achieved with the highest spring stiffness (p = 0.004). The peak activations of other measured muscles were not significantly different (p = 0.15-0.92). The biological hip extension and knee flexion moments likewise significantly decreased with the spring stiffness (p < 0.01). The joint angle was altered during the assisted phases with decreased hip flexion and knee extension. Meanwhile, the step frequency and the step length were also altered, while the step width remained unaffected. Gait variability changed only in the frontal plane, exhibiting lower step width variability. We conclude that passive devices assisting hip extension and knee flexion can significantly reduce the burden on the hamstring muscles, while the kinematics is easily altered.

Robotic devices for paediatric rehabilitation: a review of design features

Children with physical disabilities often have limited performance in daily activities, hindering their physical development, social development and mental health. Therefore, rehabilitation is essential to mitigate the adverse effects of the different causes of physical disabilities and improve independence and quality of life. In the last decade, robotic rehabilitation has shown the potential to augment traditional physical rehabilitation. However, to date, most robotic rehabilitation devices are designed for adult patients who differ in their needs compared to paediatric patients, limiting the devices' potential because the paediatric patients' needs are not adequately considered. With this in mind, the current work reviews the existing literature on robotic rehabilitation for children with physical disabilities, intending to summarise how the rehabilitation robots could fulfil children's needs and inspire researchers to develop new devices. A literature search was conducted utilising the Web of Science, PubMed and Scopus databases. Based on the inclusion-exclusion criteria, 206 publications were included, and 58 robotic devices used by children with a physical disability were identified. Different design factors and the treated conditions using robotic technology were compared. Through the analyses, it was identified that weight, safety, operability and motivation were crucial factors to the successful design of devices for children. The majority of the current devices were used for lower limb rehabilitation. Neurological disorders, in particular cerebral palsy, were the most common conditions for which devices were designed. By far, the most common actuator was the electric motor. Usually, the devices present more than one training strategy being the assistive strategy the most used. The admittance/impedance method is the most popular to interface the robot with the children. Currently, there is a trend on developing exoskeletons, as they can assist children with daily life activities outside of the rehabilitation setting, propitiating a wider adoption of the technology. With this shift in focus, it appears likely that new technologies to actuate the system (e.g. serial elastic actuators) and to detect the intention (e.g. physiological signals) of children as they go about their daily activities will be required.

A Vacuum-Powered Artificial Muscle Designed for Infant Rehabilitation

The majority of soft pneumatic actuators for rehabilitation exercises have been designed for adult users. Specifically, there is a paucity of soft rehabilitative devices designed for infants with upper and lower limb motor disabilities. We present a low-profile vacuum-powered artificial muscle (LP-VPAM) with dimensions suitable for infants. The actuator produced a maximum force of 26 N at vacuum pressures of -40 kPa. When implemented in an experimental model of an infant leg in an antagonistic-agonist configuration to measure resultant knee flexion, the actuator generated knee flexion angles of 43° and 61° in the prone and side-lying position, respectively.

Stability During Stairmill Ascent With Upward and Downward Applied Forces on the Pelvis

This study investigates how external vertical forces on the pelvis change the stability of stairmill climbing and other gait parameters such as kinematics and muscle activity. We use a Tethered Pelvic Assist Device (TPAD) to apply forces on the pelvis during continuous ascent on a stairmill. Ten young healthy subjects participated in three one-minute stair ascent with no force, a 10% body weight (BW) downward force, and a 10% BW upward force applied on the pelvis. The stability is determined by evaluating the base of support (BoS) and margin of stability (MoS). Kinematics and muscle activities were used to characterize the biomechanical changes. The results show that the upward forces applied on the pelvis decreased the (i) MoS by 1.84cm in the lateral direction, 2.07cm in the anterior direction, (ii) double stance phase by 1.85%, and (iii) the knee flexion by 5°. Furthermore, the peak activation levels of the muscles rectus femoris (RF), vastus lateralis (VL), and left gastrocnemius decreased. In contrast, the downward forces applied on the pelvis increased (i) the MOS by 1.5cm in the anterior direction and (ii) mean activation levels of RF and VL muscles. This study provides insights into the effects of applied vertical forces on the pelvis during stair ascent. These findings contribute to the understanding of the gait parameter changes and their relation with stability. Results could be used as a basis for designing training protocols to improve balance during stair ascent.

Pilot evaluation of changes in motor control after wearable robotic resistance training in children with cerebral palsy

Cerebral palsy (CP) is characterized by deficits in motor function due to reduced neuromuscular control. We leveraged the guiding principles of motor learning theory to design a wearable robotic intervention intended to improve neuromuscular control of the ankle. The goal of this study was to determine the neuromuscular and biomechanical response to four weeks of exoskeleton ankle resistance therapy (exo-therapy) in children with CP. Five children with CP (12 - 17 years, GMFCS I - II, two diplegic and three hemiplegic, four males and one female) were recruited for ten 20-minute sessions of exo-therapy. Surface electromyography, three-dimensional kinematics, and metabolic data were collected at baseline and after training was complete. After completion of training and with no device on, participants walked with decreased co-contraction between the plantar flexors and dorsiflexors (-29 ± 11%, p = 0.02), a more typical plantar flexor activation profile (33 ± 13% stronger correlation to a typical soleus activation profile, p = 0.01), and increased neural control complexity (7 ± 3%, p < 0.01 measured via muscle synergy analysis). These improvements in neuromuscular control led to a more mechanically efficient gait pattern (58 ± 34%, p < 0.05) with a reduced metabolic cost of transport (-29 ± 15%, p = 0.02). The findings from this study suggest that ankle exoskeleton resistance therapy shows promise for rapidly improving neuromuscular control for children with CP, and may serve as a meaningful rehabilitative complement to common surgical procedures.

Does Ankle Exoskeleton Assistance Impair Stability During Walking in Individuals with Cerebral Palsy?

Lower-limb exoskeletons have the potential to improve mobility in individuals with movement disabilities, such as cerebral palsy (CP). The goal of this study was to assess the impact of plantar-flexor assistance from an untethered ankle exoskeleton on dynamic stability during unperturbed and perturbed walking in individuals with CP. Seven participants with CP (Gross Motor Function Classification System levels I-III, ages 6-31 years) completed a treadmill walking protocol under their normal walking condition and while wearing an ankle exoskeleton that provided adaptive plantar-flexor assistance. Pseudo-randomized treadmill perturbations were delivered during stance phase by accelerating one side of a split-belt treadmill. Treadmill perturbations resulted in a significant decrease in anteroposterior minimum margin-of-stability (- 32.1%, p < 0.001), and a significant increase in contralateral limb step length (8.1%, p = 0.005), integrated soleus activity during unassisted walking (23.4%, p = 0.02), and peak biological ankle moment (9.6%, p = 0.03) during stance phase. Plantar-flexor assistance did not significantly alter margin-of-stability, step length, soleus activity, or ankle moments during both unperturbed and perturbed walking. These results indicate that adaptive plantar-flexor assistance from an untethered ankle exoskeleton does not significantly alter dynamic stability maintenance during unperturbed and perturbed walking for individuals with CP, supporting future research in real-world environments.

Promoting Functional and Independent Sitting in Children With Cerebral Palsy Using the Robotic Trunk Support Trainer

Seated postural abilities are critical to functional independence and participation in children with cerebral palsy, Gross Motor Functional Classification System (GMFCS) levels III-IV. In this proof-of-concept study, we investigated the feasibility of a motor learning-based seated postural training with a robotic Trunk-Support-Trainer (TruST) in a longitudinal single-subject-design (13y, GMFCS IV), and its potential effectiveness in a group of 3 children (6-14y, GMFCS III-IV). TruST is a motorized-cable driven belt placed on the child's trunk to exert active-assistive forces when the trunk moves beyond stability limits. TruST-intervention addresses postural-task progression by tailoring the assistive-force fields to the child's sitting balance to train trunk control during independent short-sitting posture. TruST-intervention consisted of 2 training blocks of six 2hour-sessions per block (3 sessions per week). Pelvic strapping was required in the 1^st block to prevent falls. As primary outcomes, we used the modified functional reach test, gross motor function measure-item set (GMFM-IS), Box & Blocks, and postural kinematics. After TruST-intervention children did not require pelvic strapping to prevent a fall, improved trunk stability during reaching (baseline = 5.49cm, 1week post-training = 16.38cm, 3mos follow-up = 14.63cm, ) and increased their sitting workspace (baseline = 127.55cm², 1week post-training, = 409.92cm², 3mos follow-up = 270.03cm², ). Three children also improved in the GMFM-IS. In summary, our novel robotic TruST-intervention is feasible and can effectively maximize functional independent sitting in children with CP GMFCS III-IV.

Crouch gait or flexed-knee gait in cerebral palsy: Is there a difference? A systematic review

BACKGROUND

Crouch or flexed-knee gait is one of the most common pathological gait patterns in cerebral palsy (CP). Differences exist in definitions used; the degree of knee flexion, inclusion of hip or ankle position, and timing in the gait cycle. This ambiguity may be responsible for variations in prevalence rates and difficulty comparing data across studies.

RESEARCH QUESTION

What are the kinematic parameters used to define crouch or flexed-knee gait in CP gait? A secondary aim was to examine the quality of data reporting, focusing on the sample characteristics, inclusion/exclusion criteria and the choice of limb included for analysis.

METHODS

Articles included in this review reported on a specified cohort of adults or children with crouch or flexed-knee gait assessed with 3-dimensional gait analysis. A customised data extraction and quality assessment table was designed specific to the research question.

RESULTS

The majority (75 %) of included studies used the term crouch gait. Where the pattern was defined, 80 % of crouch papers and 94 % of flexed-knee gait papers based this solely on knee position. Kinematic parameters were clearly defined when they provided objective values of knee flexion, supported this with rationale and provided a reference point in the gait cycle. Only 22 % of crouch papers and 19 % of flexed-knee gait papers provided this information. The majority of studies (67 % crouch; 90 % flexed-knee) specified which limb(s) were included for analysis with the majority including both limbs. Objective values of knee flexion ranged from 8 o to 30 o.

SIGNIFICANCE

This review highlights that crouch and flexed knee are synonymous and ambiguity exists in the kinematic definition making it difficult to make compare data amongst study cohorts. Future research should provide detailed definitions including the threshold value of knee flexion, how it was derived, the timing in the gait cycle and the limb(s) included in analysis.

Adding Haptic Feedback to Virtual Environments With a Cable-Driven Robot Improves Upper Limb Spatio-Temporal Parameters During a Manual Handling Task

Physical interactions within virtual environments are often limited to visual information within a restricted workspace. A new system exploiting a cable-driven parallel robot to combine visual and haptic information related to environmental physical constraints (e.g. shelving, object weight) was developed. The aim of this study was to evaluate the impact on user movement patterns of adding haptic feedback in a virtual environment with this robot. Twelve healthy participants executed a manual handling task under three conditions: 1) in a virtual environment with haptic feedback; 2) in a virtual environment without haptic feedback; 3) in a real physical environment. Temporal parameters (movement time, peak velocity, movement smoothness, time to maximum flexion, time to peak wrist velocity) and spatial parameters of movement (maximum trunk flexion, range of motion of the trunk, length of the trajectory, index of curvature and maximum clearance from the shelf) were analysed during the reaching, lowering and lifting phases. Our results suggest that adding haptic feedback improves spatial parameters of movement to better respect the environmental constraints. However, the visual information presented in the virtual environment through the head mounted display appears to have an impact on temporal parameters of movement leading to greater movement time. Taken together, our results suggest that a cable-driven robot can be a promising device to provide a more ecological context during complex tasks in virtual reality.

Adaptive Ankle Resistance from a Wearable Robotic Device to Improve Muscle Recruitment in Cerebral Palsy

Individuals with cerebral palsy can have weak and poorly coordinated ankle plantar flexor muscles that contribute to inefficient walking patterns. Previous studies attempting to improve plantar flexor function have had inconsistent effects on mobility, likely due to a lack of task-specificity. The goal of this study was to develop, validate, and test the feasibility and neuromuscular response of a novel wearable adaptive resistance platform to increase activity of the plantar flexors during the propulsive phase of gait. We recruited eight individuals with spastic cerebral palsy to walk with adaptive plantar flexor resistance provided from an untethered exoskeleton. The resistance system and protocol was safe and feasible for all of our participants. Controller validation demonstrated our ability to provide resistance that proportionally- and instantaneously-adapted to the biological ankle moment (R = 0.92 ± 0.04). Following acclimation to resistance (0.16 ± 0.02 Nm/kg), more-affected limbs exhibited a 45 ± 35% increase in plantar flexor activity (p = 0.02), a 26 ± 24% decrease in dorsiflexor activity (p < 0.05), and a 46 ± 25% decrease in co-contraction (tibialis anterior and soleus) (p = 0.02) during the stance phase. This adaptive resistance system warrants further investigation for use in a longitudinal intervention study.

The robotic Trunk-Support-Trainer (TruST) to measure and increase postural workspace during sitting in people with spinal cord injury

Study design

Cross-sectional study.

Objectives

To measure and expand the sitting workspace of participants with spinal cord injury (SCI) with the Trunk-Support-Trainer (TruST).

Setting

Columbia University.

Methods

TruST is a motorized-cable belt placed around the torso. Participants performed maximal trunk excursions along eight directions, radiating in a star-shape, to define their seated postural limits and workspace area (cm2). TruST was configured to apply "assist-as-needed" forces when the trunk moved beyond these postural limits. Kinematics were collected to examine trunk control. The clinical features of the sample (n = 5) were documented by neurological injury, dynamometry, the American Spinal Injury Association Impairment Scale, and Spinal Cord Independence Measure-III.

Results

Statistical significance was examined with paired t-tests. TruST successfully recreated the postural limits of participants and expanded their active sitting workspace (Mean: 123.3 ± SE: 42.8 cm2, p < 0.05). Furthermore, participants improved their trunk excursions to posterior (Mean: 5.1 ± SE: 0.8 cm, p < 0.01), right (Mean: 3.1 ± SE: 1.1 cm, p < 0.05), and left (Mean: 5.0 ± SE: 1.7 cm, p = 0.05) directions with TruST-force field.

Conclusions

TruST can accurately define and expand the active seated workspace of people with SCI during volitional trunk movements. The capacity of TruST to deliver continuous force-feedback at the user's postural limits opens new frontiers to implement motor learning-based paradigms to retrain functional sitting in people with SCI.

Stand Trainer With Applied Forces at the Pelvis and Trunk: Response to Perturbations and Assist-As-Needed Support

Functional rehabilitation of patients with spinal cord injury remains a current challenge. Training these patients to successfully stand is the first step towards restoring advanced skills such as walking. To address this need, we have developed a novel robotic stand trainer that can apply controlled forces on the trunk and the pelvis of a user, while controlling the knee angle. The stand trainer utilizes cables to apply assistive, resistive, or perturbation forces at the trunk, pelvis, and the knees, simultaneously. We have conducted a human study to validate the system. In this study, we applied multi-direction perturbation forces either at the pelvis or the trunk while assist-as-needed forces were applied to the other segment to keep balance. This study characterizes the human kinematics and measures of balance under the perturbations and assistive forces on the human body. Results shows that the level of force-field assistance (trunk or pelvis) directly affects the motion of the trunk, pelvis, and center of pressure. This provides a quantitative framework to restore balance in patients while providing assistance only when needed. This stand trainer can potentially free up therapists to attend to higher level rehabilitation goals and objectively assist patients to engage in interventions that challenge both their musculoskeletal and sensorimotor impairments.

Voluntary control of wearable robotic exoskeletons by patients with paresis via neuromechanical modeling

BACKGROUND

Research efforts in neurorehabilitation technologies have been directed towards creating robotic exoskeletons to restore motor function in impaired individuals. However, despite advances in mechatronics and bioelectrical signal processing, current robotic exoskeletons have had only modest clinical impact. A major limitation is the inability to enable exoskeleton voluntary control in neurologically impaired individuals. This hinders the possibility of optimally inducing the activity-driven neuroplastic changes that are required for recovery.

METHODS

We have developed a patient-specific computational model of the human musculoskeletal system controlled via neural surrogates, i.e., electromyography-derived neural activations to muscles. The electromyography-driven musculoskeletal model was synthesized into a human-machine interface (HMI) that enabled poststroke and incomplete spinal cord injury patients to voluntarily control multiple joints in a multifunctional robotic exoskeleton in real time.

RESULTS

We demonstrated patients' control accuracy across a wide range of lower-extremity motor tasks. Remarkably, an increased level of exoskeleton assistance always resulted in a reduction in both amplitude and variability in muscle activations as well as in the mechanical moments required to perform a motor task. Since small discrepancies in onset time between human limb movement and that of the parallel exoskeleton would potentially increase human neuromuscular effort, these results demonstrate that the developed HMI precisely synchronizes the device actuation with residual voluntary muscle contraction capacity in neurologically impaired patients.

CONCLUSIONS

Continuous voluntary control of robotic exoskeletons (i.e. event-free and task-independent) has never been demonstrated before in populations with paretic and spastic-like muscle activity, such as those investigated in this study. Our proposed methodology may open new avenues for harnessing residual neuromuscular function in neurologically impaired individuals via symbiotic wearable robots.

Simulating Hemiparetic Gait in Healthy Subjects Using TPAD With a Closed-Loop Controller

Hemiparetic gait is abnormal asymmetric walking, often observed among patients with cerebral palsy or stroke. One of the major features of asymmetric gait is excessive reliance on the healthy leg, which results in improper load shift, slow walking speed, higher metabolic cost, and weakness of the unused leg. Hence, clinically it is desirable to promote gait symmetry to improve walking. While there are no clear methods to achieve this goal, we are exploring new methods where we guide the pelvis to change the gait symmetry. This controller is designed to mimic the hands of a physical therapist holding the pelvis and guiding it to promote the usage of both legs during walking. In this paper, we show that the essence of this method can be demonstrated by promoting asymmetry in the gait of healthy subjects when walking with the device. The results showed that their kinematics and kinetics changed asymmetrically during the intervention. Subjects demonstrated asymmetric lateral ground reaction force to compensate for the lateral forces applied on the pelvis. Muscle activities increased on the targeted leg show the forced use of the leg which can be used for rehabilitation of patients with an asymmetric gait.

An Untethered Ankle Exoskeleton Improves Walking Economy in a Pilot Study of Individuals With Cerebral Palsy

The high energy cost of walking in individuals with cerebral palsy (CP) contributes significantly to reduced mobility and quality of life. The purpose of this paper was to develop and clinically evaluate an untethered ankle exoskeleton with the ability to reduce the metabolic cost of walking in children and young adults with gait pathology from CP. We designed a battery-powered device consisting of an actuator-and-control module worn above the waist with a Bowden cable transmission used to provide torque to pulleys aligned with the ankle. Special consideration was made to minimize adding mass to the body, particularly distal portions of the lower-extremity. The exoskeleton provided plantar-flexor assistance during the mid-to-late stance phase, controlled using a real-time control algorithm and embedded sensors. We conducted a device feasibility and a pilot clinical evaluation study with five individuals with CP ages five through thirty years old. Participants completed an average of 130 min of exoskeleton-assisted walking practice. We observed a 19±5% improvement in the metabolic cost of transport (p = 0.011) during walking with untethered exoskeleton assistance compared to how participants walked normally. These preliminary findings support the future investigation of powered ankle assistance for improving mobility in this patient population.

Adaptation of Stability during Perturbed Walking in Parkinson's Disease

Gait and balance disorders are major problems that contribute to falls among subjects with Parkinson's disease (PD). Strengthening the compensatory responses through the use of balance perturbations may improve balance in PD. To date, it is unclear how PD affects the ability to react and adapt to perturbations delivered while walking. This study aims to investigate how PD affects the ability to walk, respond to balance perturbations, and produce acute short-term effects to improve compensatory reactions and gait stability. A cable-driven robot was used to train nine patients with PD and nine age-matched controls with multidirectional waist-pull perturbations while walking on a treadmill. Margin of stability and base of support were evaluated while walking without cables and reacting to the perturbations. PD was associated with a reduced stability in the forward direction and the inability to produce proactive anticipatory adjustments. Both groups were able to improve the response to the disturbances and produce short-term aftereffects of increased gait stability once the cables were removed. A single session of perturbation-based balance training produced acute effects that ameliorated gait instability in PD. This result is encouraging for designing new therapeutic interventions that remediate falls risk.