Hybrid walking therapy with fatigue management for spinal cord injured individuals

In paraplegic individuals with upper motor neuron lesions the descending path for signals from central nervous system to the muscles are lost or diminished. Motor neuroprosthesis based on electrical stimulation can be applied to induce restoration of motor function in paraplegic patients. Furthermore, electrical stimulation of such motor neuroprosthesis can be more efficiently managed and delivered if combined with powered exoskeletons that compensate the limited force in the stimulated muscles and bring additional support to the human body. Such hybrid overground gait therapy is likely to be more efficient to retrain the spinal cord in incomplete injuries than conventional, robotic or neuroprosthetic approaches. However, the control of bilateral joints is difficult due to the complexity, non-linearity and time-variance of the system involved. Also, the effects of muscle fatigue and spasticity in the stimulated muscles complicate the control task. Furthermore, a compliant joint actuation is required to allow for a cooperative control approach that is compatible with the assist-as-needed rehabilitation paradigm. These were direct motivations for this research. The overall aim was to generate the necessary knowledge to design a novel hybrid walking therapy with fatigue management for incomplete spinal cord injured subjects. Research activities were conducted towards the establishment of the required methods and (hardware and software) systems that required to proof the concept with a pilot clinical evaluation. Speciffically, a compressive analysis of the state of the art on hybrid exoskeletons revealed several challenges which were tackled by this dissertation. Firstly, assist-as-needed was implemented over the basis of a compliant control of the robotic exoskeleton and a closed-loop control of the neuroprosthesis. Both controllers are integrated within a hybrid-cooperative strategy that is able to balance the assistance of the robotic exoskeleton regarding muscle performance. This approach is supported on the monitoring of the leg-exoskeleton physical interaction. Thus the fatigue caused by neuromuscular stimulation was also subject of speciffic research. Experimental studies were conducted with paraplegic patients towards the establishment of an objective criteria for muscle fatigue estimation and management. The results of these studies were integrated in the hybrid-cooperative controller in order to detect and manage muscle fatigue while providing walking therapy. Secondly closed-loop control of the neuroprosthesis was addressed in this dissertation. The proposed control approach allowed to tailor the stimulation pattern regarding the speciffic residual motor function of the lower limb of the patient. In order to uncouple the closed-loop control from muscle performance monitoring, the hybrid-cooperative control approach implemented a sequential switch between closed-loop and open-loop control of the neuroprosthesis. Lastly, a comprehensive clinical evaluation protocol allowed to assess the impact of the hybrid walking therapy on the gait function of a sample of paraplegic patients. Results demonstrate that: 1) the hybrid controller adapts to patient residual function during walking, 2) the therapy is tolerated by patients, and 3) the walking function of patients was improved after participating in the study. In conclusion, the hybrid walking therapy holds potential for rehabilitate walking in motor incomplete paraplegic patients, guaranteeing further research on this topic. This dissertation is framed within two research projects: REHABOT (Ministerio de Ciencia e Innovación, grant DPI2008-06772-C03-02) and HYPER (Hybrid Neuroprosthetic and Neurorobotic Devices for Functional Compensation and Rehabilitation of Motor Disorders, grant CSD2009-00067 CONSOLIDER INGENIO 2010). Within these research projects, cutting-edge research is conducted in the eld of hybrid actuation and control for rehabilitation of motor disorders. This dissertation constitutes proof-of concept of the hybrid walking therapy for paraplegic individuals for these projects. ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------En individuos parapléjicos con lesiones de la motoneurona superior, la conexión descendente para la transmisión de las señales del sistema nervioso central a los músculos se ve perdida o disminuida. Las neuroprótesis motoras basadas en la estimulación eléctrica pueden ser aplicadas para inducir la restauración de la función motora en pacientes con paraplejia. Además, la estimulación eléctrica de tales neuroprótesis motoras se puede gestionar y aplicar de manera más eficiente mediante la combinación con exoesqueletos robóticos que compensen la generación limitada de fuerza de los músculos estimulados, y proporcionen soporte adicional para el cuerpo. Dicha terapia de marcha ambulatoria puede ser probablemente más eficaz para la recuperación de las funciones de la médula espinal en lesiones incompletas que las terapias convencionales, robóticas o neuroprotesicas. Sin embargo, el control bilateral de las articulaciones es difícil debido a la complejidad, no-linealidad y la variación con el tiempo de las características del sistema en cuestión. Además, la fatiga muscular y la espasticidad de los músculos estimulados complican la tarea de control. Por otra parte, se requiere una actuación robótica modulable para permitir un enfoque de control cooperativo compatible con el paradigma de rehabilitación de asistencia bajo demanda. Todo lo anterior constituyó las motivaciones directas para esta investigación. El objetivo general fue generar el conocimiento necesario para diseñar un nuevo tratamiento híbrido de rehabilitación marcha con gestión de la fatiga para lesionados medulares incompletos. Se llevaron a cabo actividades de investigación para el establecimiento de los métodos necesarios y los sistemas (hardware y software) requeridos para probar el concepto mediante una evaluación clínica piloto. Específicamente, un análisis del estado de la técnica sobre exoesqueletos híbridos reveló varios retos que fueron abordados en esta tesis. En primer lugar, el paradigma de asistencia bajo demanda se implementó sobre la base de un control adaptable del exoesqueleto robótico y un control en lazo cerrado de la neuroprótesis. Ambos controladores están integrados dentro de una estrategia híbrida cooperativa que es capaz de equilibrar la asistencia del exoesqueleto robótico en relación con el rendimiento muscular. Este enfoque se soporta sobre la monitorización de la interacción física entre la pierna y el exoesqueleto. Por tanto, la fatiga causada por la estimulación neuromuscular también fue objeto de una investigación específica. Se realizaron estudios experimentales con pacientes parapléjicos para el establecimiento de un criterio objetivo para la detección y la gestión de la fatiga muscular. Los resultados de estos estudios fueron integrados en el controlador híbrido-cooperativo con el fin de detectar y gestionar la fatiga muscular mientras se realiza la terapia híbrida de rehabilitación de la marcha. En segundo lugar, el control en lazo cerrado de la neuroprótesis fue abordado en esta tesis. El método de control propuesto permite adaptar el patrón de estimulación en relación con la funcionalidad residual específica de la extremidad inferior del paciente. Sin embargo, con el n de desacoplar el control en lazo cerrado de la monitorización del rendimiento muscular, el enfoque de control híbrido-cooperativo incorpora una conmutación secuencial entre el control en lazo cerrado y en lazo abierto de la neuropr otesis. Por último, un protocolo de evaluación clínica global permitido evaluar el impacto de la terapia híbrida de la marcha en la función de la marcha de una muestra de pacientes parapléjicos. Los resultados demuestran que: 1) el controlador híbrido se adapta a la función residual del paciente durante la marcha, 2) la terapia es tolerada por los pacientes, y 3) la funci on de marcha del paciente mejora despu es de participar en el estudio. En conclusión, la terapia de híbrida de la marcha alberga un potencial para la rehabilitación de la marcha en pacientes parapléjicos incompletos motor, garantizando realizar investigación más profunda sobre este tema. Esta tesis se enmarca dentro de los dos proyectos de investigación: REHABOT (Ministerio de Ciencia e Innovación, referencia DPI2008-06772-C03-02) y HYPER (Hybrid Neuroprosthetic and Neurorobotic Devices for Functional Compensation and Rehabilitation of Motor Disorders, referencia CSD2009-00067 CONSOLIDER INGENIO 2010). Dentro de estos proyectos se lleva a cabo investigación de vanguardia en el campo de la actuación y el control híbrido de la combinación robot-neuroprótesis para la rehabilitación de trastornos motores. Esta tesis constituye la prueba de concepto de la terapia de híbrida de la marcha para individuos parapléjicos en estos proyectos.This dissertation is framed within two research projects: REHABOT (Ministerio de Ciencia e Innovación, grant DPI2008-06772-C03-02) and HYPER (Hybrid Neuroprosthetic and Neurorobotic Devices for Functional Compensation and Rehabilitation of Motor Disorders, grant CSD2009-00067 CONSOLIDER INGENIO 2010

TAILOR: Patient-specific hybrid wearable systems for walking rehabilitation

Personalization of robotic exoskeletons for walking assistance to the end user is still a challenge for this technology. The TAILOR project aims to create hybrid and modular robotic-neuroprosthetic wearable systems that can be adapted to an individual patient. For that, a User-Centered Design approach and predictive dynamic simulation tools are conceived to support the design of the hybrid assistive technology.Peer ReviewedObjectius de Desenvolupament Sostenible::3 - Salut i BenestarPostprint (published version

El proyecto TAILOR: sistemas para la asistencia de la marcha

En las últimas décadas se ha constatado que la alteración de la capacidad de andar es una de las consecuencias más prevalentes, debido por un lado a la creciente incidencia de patologías de origen neurológico –ictus, daño cerebral, lesión medular, diferentes formas de esclerosis, etc.– así como al envejecimiento de la población, dado que una mayor longevidad conlleva, entre otras consecuencias, un aumento de la fragilidad y por tanto afectación de la capacidad de andarPeer ReviewedPostprint (published version

Noninvasive Modalities Used in Spinal Cord Injury Rehabilitation

In the past three decades, research on plasticity after spinal cord injury (SCI) has led to a gradual shift in SCI rehabilitation: the former focus on learning compensatory strategies changed to functional neurorecovery, that is, promoting restoration of function through the use of affected limbs. This paradigm shift contributed to the development of technology-based interventions aiming to promote neurorecovery through repetitive training. This chapter presents an overview of a range of noninvasive modalities that have been used in rehabilitation after SCI. Among others, we present repetitive transcranial magnetic stimulation (rTMS), transcranial direct current stimulation (tDCS), surface electrical stimulation tools such as transcutaneous electrical spinal cord stimulation (tcSCS), transcutaneous electrical nerve stimulation (TENS), and functional electrical stimulation (FES), as well as its integration with cycling training and assistive robotic devices. The most recent results attained and the potential relevance of these new techniques to strengthen the efficacy of the residual neuronal pathways and improve spasticity are also presented. Future efforts toward the widespread clinical application of these modalities include more advances in the technology, together with the knowledge obtained from basic research and clinical trials. This can ultimately lead to novel customized interventions that meet specific needs of SCI patients

Modelling neuromusculoskeletal response to functional electrical stimulation

A model for functional electrical stimulation with hysteretic muscle recruitment is used to reproduce experimental tibialis anterior stimulation to control ankle dorsiflexion. The subject-specific parameters of the muscle recruitment model where identified from experimental data by solving a nonlinear least-squares problemPeer ReviewedObjectius de Desenvolupament Sostenible::3 - Salut i BenestarPostprint (published version

Desarrollo de sistemas modulares robóticos y neuroprotésicos personalizables para la asistencia de la marcha patológica a través del diseño centrado en el usuario: Proyecto TAILOR

Currently available wereable exoskeletons and neuroprosthetic gait assistive devices have controverted efficacy and low penetration into rehabilitation centers because they are generic solutions that do not consider the individual requirements and characteristics of each patient. TAILOR project proposes a new approach to the design of customizable neurorobotic systems, based on robotic exoskeletons (WR) and modular neuroprosthetics (NP) to provide subject-specific solutions. These two technologies are integrated with a closed loop hybrid controller. We are using a User-Centered Design approach for the design and development of these technologies to effectively introduce the requirements and needs of patients and clinical staff. Currently, we are making modifications to the WR to integrate it to the NP, which has already been developedPeer ReviewedObjectius de Desenvolupament Sostenible::3 - Salut i BenestarPostprint (author's final draft

Adaptation Strategies for Personalized Gait Neuroprosthetics

Personalization of gait neuroprosthetics is paramount to ensure their efficacy for users, who experience severe limitations in mobility without an assistive device. Our goal is to develop assistive devices that collaborate with and are tailored to their users, while allowing them to use as much of their existing capabilities as possible. Currently, personalization of devices is challenging, and technological advances are required to achieve this goal. Therefore, this paper presents an overview of challenges and research directions regarding an interface with the peripheral nervous system, an interface with the central nervous system, and the requirements of interface computing architectures. The interface should be modular and adaptable, such that it can provide assistance where it is needed. Novel data processing technology should be developed to allow for real-time processing while accounting for signal variations in the human. Personalized biomechanical models and simulation techniques should be developed to predict assisted walking motions and interactions between the user and the device. Furthermore, the advantages of interfacing with both the brain and the spinal cord or the periphery should be further explored. Technological advances of interface computing architecture should focus on learning on the chip to achieve further personalization. Furthermore, energy consumption should be low to allow for longer use of the neuroprosthesis. In-memory processing combined with resistive random access memory is a promising technology for both. This paper discusses the aforementioned aspects to highlight new directions for future research in gait neuroprosthetics.Peer ReviewedPostprint (published version