Robotic Functional Gait Rehabilitation with Tethered Pelvic Assist Device

The primary goal of human locomotion is to stably translate the center of mass (CoM) over the ground with minimum expenditure of energy. Pelvic movement is crucial for walking because the human CoM is located close to the pelvic center. Because of this anatomical feature, pelvic motion directly contributes to the metabolic expenditure, as well as in the balance to keep the center of mass between the legs. An abnormal pelvic motion during the gait not only causes overexertion, but also adversely affects the motion of the trunk and lower limbs. In order to study different interventions, recently a cable-actuated robotic system called Tethered Pelvic Assist Device (TPAD) was developed at ROAR laboratory at Columbia University. The cable-actuated system has a distinct advantage of applying three dimensional forces on the pelvis at discrete points in the gait cycle in contrast to rigid exoskeletons that restrict natural pelvic motion and add extra inertia from the rigid linkages. However, in order to effectively use TPAD for rehabilitation purposes, we still need to have a better understanding of how human gait is affected by different forces applied by TPAD on the pelvis. In the present dissertation, three different control methodologies for TPAD are discussed by performing human experiments with healthy subjects and patients with gait deficits. Moreover, the corresponding changes in the biomechanics during TPAD training are studied to understand how TPAD mechanistically influences the quality of the human gait. In Chapter 2, an ‘assist-as-needed’ controller is implemented to guide and correct the pelvic motion in three dimensions. Here, TPAD applies the correction force based on the deviation of the current position of the pelvic center from a pre-defined target trajectory. This force acts on the pelvic center to guide it towards the target trajectory. A subject in the device experiences a force field, where the magnitude becomes larger when the subject deviates further away from the target trajectory. This control strategy is tested by performing the experiments on healthy subjects with different target pelvic trajectories. Chapter 3 describes a robotic resistive training study using a continuous force on the pelvis to strengthen the weak limbs so that subjects can improve their walking. This study is designed to improve the abnormal gait of children with Cerebral Palsy (CP) who have a crouch gait. Crouch gait is caused by a combination of weak extensor muscles that do not produce adequate muscle forces to keep the posture upright, coupled with contraction of muscles that limit the joint range of motion. Among the extensor muscles, the soleus muscle acts as the major weight-bearing muscle to prevent the knees from collapsing forward during the middle of the stance phase when the foot is on the ground. Electromyography, kinematics, and clinical measurements of the patients with crouch gait show significant improvements in the gait quality after the resistive TPAD training performed over five weeks. Both Chapters 2 & 3 present interventions that are bilaterally applied on both legs. Chapter 4 introduces a training strategy that can be used for patients who have impairments in only one leg which results in manifests as asymmetric weight-bearing while walking. This training method is designed to improve the asymmetric weight bearing of the hemiparetic patients who overly rely on the stronger leg. The feasibility of this training method is tested by experiments with healthy subjects, where the controller creates an asymmetric force field to bring asymmetry in weight bearing during walking. In summary, the present dissertation is devoted to developing new training methods that utilize TPAD for rehabilitation purposes and characterize the responses of different force interventions by investigating the resulting biomechanics. We believe that these methodologies with TPAD can be used to improve abnormal gait patterns that are often observed in cerebral palsy or stroke 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

Trunk Rehabilitation Using Cable-Driven Robotic Systems

Upper body control is required to complete many daily tasks. One needs to stabilize the head and trunk over the pelvis, as one shifts the center of mass to interact with the world. While healthy individuals can perform activities that require leaning, reaching, and grasping readily, those with neurological and musculoskeletal disorders present with control deficits. These deficits can lead to difficulty in shifting the body center of mass away from the stable midline, leading to functional limitations and a decline in the quality of activity. Often these patient groups use canes, walkers, and wheelchairs for support, leading to occasional strapping or joint locking of the body for trunk stabilization. Current rehabilitation strategies focus on isolated components of stability. This includes strengthening, isometric exercises, hand-eye coordination tasks, isolated movement, and proprioceptive training. Although all these components are evidence based and directly correlate to better stability, motor learning theories such as those by Nikolai Bernstein, suggest that task and context specific training can lead to better outcomes. In specific, based on our experimentation, we believe functional postural exploration, while encompassing aspects of strengthening, hand-eye coordination, and proprioceptive feedback can provide better results. In this work, we present two novel cable robotic platforms for seated and standing posture training. The Trunk Support Trainer (TruST) is a platform for seated posture rehabilitation that provides controlled external wrench on the human trunk in any direction in real-time. The Stand Trainer is a platform for standing posture rehabilitation that can control the trunk, pelvis, and knees, simultaneously. The system works through the use of novel force-field algorithms that are modular and user-specific. The control uses an assist-as-needed strategy to apply forces on the user during regions of postural instability. The device also allows perturbations for postural reactive training. We have conducted several studies using healthy adult populations and pilot studies on patient groups including cerebral palsy, cerebellar ataxia, and spinal cord injury. We propose new training methods that incorporate motor learning theory and objective interventions for improving posture control. We identify novel methods to characterize posture in form of the “8-point star test”. This is to assess the postural workspace. We also demonstrate novel methods for functional training of posture and balance. Our results show that training with our robotic platforms can change the trunk kinematics. Specifically, healthy adults are able to translate the trunk further and rotate the trunk more anteriorly in the seated position. In the standing position, they can alter their reach strategy to maintain the upper trunk more vertically while reaching. Similarly, Cerebral Palsy patients improve their trunk translations, reaching workspace, and maintain a more vertical posture after training, in the seated position. Our results also showed that an Ataxia patient was able to improve their reaching workspace and trunk translations in the standing position. Finally, our results show that the robotic platforms can successfully reduce trunk and pelvis sway in spinal cord injury patients. The results of the pilot studies suggest that training with our robotic platforms and methods is beneficial in improving trunk control

Design And Development of A Powered Pediatric Lower-limb Orthosis

Gait impairments from disorders such as cerebral palsy are important to address early in life. A powered lower-limb orthosis can offer therapists a rehabilitation option using robot-assisted gait training. Although there are many devices already available for the adult population, there are few powered orthoses for the pediatric population. The aim of this dissertation is to embark on the first stages of development of a powered lower-limb orthosis for gait rehabilitation and assistance of children ages 6 to 11 years with walking impairments from cerebral palsy. This dissertation presents the design requirements of the orthosis, the design and fabrication of the joint actuators, and the design and manufacturing of a provisional version of the pediatric orthosis. Preliminary results demonstrate the capabilities of the joint actuators, confirm gait tracking capabilities of the actuators in the provisional orthosis, and evaluate a standing balance control strategy on the under-actuated provisional orthosis in simulation and experiment. In addition, this dissertation presents the design methodology for an anthropometrically parametrized orthosis, the fabrication of the prototype powered orthosis using this design methodology, and experimental application of orthosis hardware in providing walking assistance with a healthy adult. The presented results suggest the developed orthosis hardware is satisfactorily capable of operation and functional with a human subject. The first stages of development in this dissertation show encouraging results and will act as a foundation for further iv development of the device for rehabilitation and assistance of children with walking impairments

Design Principles for FES Concept Development

© Cranfield University 2013. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright owner.A variety of pathologies can cause injury to the spinal cord and hinder movement. A range of equipment is available to help spinal injury sufferers move their affected limbs. One method of rehabilitation is functional electrical stimulation (FES). FES is a technique where small electrical currents are applied to the surface of the user’s legs to stimulate the muscles. Studies have demonstrated the benefits of using this method and it has also been incorporated into a number of devices. The aim of the project was to produce a number of designs for a new device that uses FES technology. The project was completed in conjunction with an industrial partner. A review of the literature and consultation with industrial experts suggested a number of ways current devices could be improved. These included encouraging the user to lean forwards while walking and powering the device using a more ergonomic method. A group of designers were used to produce designs that allowed the user to walk with a more natural gait and avoided cumbersome power packs. The most effective of these designs were combined to form one design that solved both problems. A 3-dimensional model of this design was simulated using computer-aided design software. Groups of engineers, scientists and consumers were also invited to provide input on how a new device should function. Each of these groups provided a design that reflected their specific needs, depending on their experience with similar technology. Low level prototypes were produced of these designs. A group of designers were also used to design concepts for a functional electrical stimulation device based on an introduction given by industry experts. Each of the designs was presented to experienced professionals to obtain feedback. A set of guidelines were also produced during the project that instructed how to create the designs

USING MUSCULOSKELETAL MODELING TO ASSESS MUSCLE FUNCTION AND GAIT ASYMMETRY AFTER A STRAYER PROCEDURE APPLIED TO A CHILD WITH CEREBRAL PALSY

Cerebral palsy (CP) is a common group of neuromotor disorders with symptoms appearing during childhood. Children with CP often undergo orthopedic surgeries and treatment plans depending on the gait pattern and its severity. Jump gait is a gait pattern present in bilateral spastic CP and is characterized by a combination of ankle equinus, accentuated hip and knee flexion, lumbar lordosis, and anterior pelvis tilt. The modified Strayer procedure is a surgical intervention to treat equinus in ambulatory children with CP and is often accompanied by botulinum toxin type A (BTX) injections to aid in spasticity reduction. Musculoskeletal modeling is a promising approach to indirectly estimatemuscle function, includingmuscle force, andmuscle induced accelerations. Gait asymmetry is often studied as it is associated with pathological gait. This study aimed to analyze the improvements in gait function in one child with CP following corrective surgery for jump gait. Gait asymmetry, muscle forces and contributions to the center of mass accelerations during walking were assessed before, one and two years after surgery. Furthermore, comparison with typically developed children was also performed. Threedimensional marker coordinates and ground reaction forces (GRF) during walking were recorded and used as input for musculoskeletal simulations using OpenSim. Two years post-surgery, gait asymmetry reduced to levels similar to or lower than unimpaired gait. Overall joint kinematics improved, although the increase in dorsiflexion was not enough to achieve heel strike at first contact in the lower limb submitted to surgery. Estimates of muscle forces showed the child with CP relied more on proximal muscles to walk, mainly the vasti and hamstrings, before and after surgery. Soleus muscle forces increased following surgery, becoming the primary contributor to vertical support from the plantarflexors. Suggestions were made for treatment plans and for maintaining surgical improvements, such as strengthening of weakened muscles.Paralisia cerebral (PC) é um grupo de perturbações neuromotoras cujos sintomas aparecem durante a infância. Crianças com PC são regularmente submetidas a cirurgias ortopédicas e planos de tratamento de acordo com o padrão de marcha e grau de severidade. Marcha em salto é um padrão de marcha presente em PC espástica bilateral caracterizada por pé equino, flexão acentuada do joelho e anca, lordose lombar, e inclinação pélvica anterior. O procedimento modificado de Strayer é uma cirurgia comum para tratar pé equino em crianças com PC em contexto ambulatório e é normalmente acompanhada por injeções de toxina botulínica. Modelação musculoesquelética é uma abordagem que permite estimar, indiretamente, as forças e acelerações induzidas musculares. Assimetria na marcha é frequentemente estudada por estar associada a uma marcha patológica. O objetivo deste trabalho consiste em estudar as melhorias na marcha de uma criança com PC após cirurgia. Assimetria da marcha, forças e contribuições musculares para a aceleração do centro de massa foram avaliadas antes, um e dois anos após cirurgia. Além disso, foi feita a comparação com marcha saudável. Foram gravadas as coordenadas tridimensionais dos marcadores e forças de reação do solo para as simulações musculoesqueléticas através do OpenSim. Dois anos após cirurgia, a assimetria melhorou para níveis semelhantes ou inferiores aos da marcha saudável. Em termo gerais, a cinemática melhorou, porém, apesar da capacidade de dorsiflexão ter aumentado, o calcanhar não estabelece o primeiro contacto no membro inferior submetido a cirurgia. Resultados das forças musculares mostram uma maior dependência em músculos proximais na criança com PC, principalmente o vasto e os isquiotibiais, antes e após cirurgia. As forças musculares do solear aumentaram após cirurgia, tornando-se o principal plantarflexor a contribuir para o suporte. Fortalecimento de músculos enfraquecidos foi um dos planos de tratamento sugeridos para preservação das melhorias obtidas pela cirurgia

Factors associated with stiff knee gait in cerebral palsy

Stiff knee gait (SKG) is one of a few classified walking patterns which people with cerebral palsy (pwCP) can present with. The characteristic for SKG is delayed and/or reduced peak knee flexion during swing phase, which can reduce walking ability and result in functional restrictions. Through the use of both clinical and laboratory based measures this cross-sectional study aimed to identify the factors associated with SKG, suggest possible treatment options and propose potential directions for future research. The impact of five variables on knee flexion amplitude during the swing phase of gait was assessed. Data was gathered from a group of 27 pwCP and 20 age-matched controls. Three dimensional motion analysis was used to record the kinetics and kinematics of the pelvis and lower limbs. Isometric strength of the ankle plantarflexors, knee extensors, hip flexors and hip extensors was recorded via maximal voluntary contraction using a dynamometer. Passive and stretch-mediated stiffness of the knee extensors was also recorded using a dynamometer with two set stretch speeds. The main findings highlight that several factors are correlated with SKG. The key determinants of which are a crouch positioning of the lower limb in stance phase and spasticity within the knee extensors. Additionally, secondary analysis highlighted the importance of the knee extensors inner/outer range strength ratio. Greater weakness in inner range was linked to increased spasticity, to the degree of crouch and in turn to a smaller degree of knee flexion in swing phase. This study further highlighted that both clinical and laboratory based measures may be used to determine the possible causes of SKG but that laboratory based gait analysis and outcome measures were more sensitive and had higher predictive power. The implications for treatment are to be mindful of the fact that by attempting to improve one impairment it does not have a negative effect upon another. Inter-relationships between impairments need to be looked at in more detail. Future work should evaluate treatments on SKG of strengthening the inner range quadriceps with/without a stretching programme

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

The biomechanics of human locomotion

Includes bibliographical references. The thesis on CD-ROM includes Animate, GaitBib, GaitBook and GaitLab, four quick time movies which focus on the functional understanding of human gait. The CD-ROM is available at the Health Sciences Library