A sensorized thumb for force closed-loop control of hand neuroprostheses

Garments for functional electrical stimulation: Design and proofs of concept

Introduction

Repeated use of functional electrical stimulation can promote functional recovery in individuals with neurological paralysis. We designed garments able to deliver functional electrical stimulation.

Methods

Shirts and pants containing electrodes knitted with a conductive yarn were produced. Electrodes were moistened with water before use. Stimulation intensity at four thresholds levels (sensory, movement, full range of motion, and maximal), stimulation comfort, and electrical properties of the interface were tested in one able-bodied subject with garment electrodes and size-matched conventional gel electrodes. The pants and shirt were then used to explore usability and design limitations.

Results

Compared to gel electrodes, fabric electrodes had a lower sensory threshold (on forearm muscles) but they had a higher maximal stimulation threshold (for all tested muscles). The stimulation delivery was comfortable when the garment electrodes were recently moistened; however, as the electrodes dried (within 9 to 18 min) stimulation became unpleasant. Inconsistent water content in the fabric electrodes caused inconsistent intensity thresholds and inconsistent voltage necessary to apply a desired stimulation current. Garments’ tightness and impracticality of electrode lead necessitate further design improvement.

Conclusions

Fabric electrodes offer a promising alternative to gel electrodes. Further work involving people with paralysis is required to overcome the identified challenges.

Making sense of artificial hands

A review of sensors for artificial hands is presented in terms of their range, specifications and characteristics. There is a growing need for sensors due to the development of prosthetic hands that have multiple degrees of freedom requiring finger coordination into different postures. The sensing of force, position (angle), object-slip and temperature allows for the control of these hands automatically and frees the user from cognitive burden. To make the best possible use of individual sensing elements, future controllers will need to combine data from different types of sensor. They may also have an integral power supply using a small battery or harvest energy from their environment and transmit data wirelessly.

Referral of sensation to an advanced humanoid robotic hand prosthesis

Hand prostheses that are currently available on the market are used by amputees to only a limited extent, partly because of lack of sensory feedback from the artificial hand. We report a pilot study that showed how amputees can experience a robot-like advanced hand prosthesis as part of their own body. We induced a perceptual illusion by which touch applied to the stump of the arm was experienced from the artificial hand. This illusion was elicited by applying synchronous tactile stimulation to the hidden amputation stump and the robotic hand prosthesis in full view. In five people who had had upper limb amputations this stimulation caused referral touch sensation from the stump to the artificial hand, and the prosthesis was experienced more like a real hand. We also showed that this illusion can work when the amputee controls the movements of the artificial hand by recordings of the arm muscle activity with electromyograms. These observations indicate that the previously described "rubber hand illusion" is also valid for an advanced hand prosthesis, even when it has a robotic-like appearance.

On the identification of sensory information from mixed nerves by using single-channel cuff electrodes

Background

Several groups have shown that the performance of motor neuroprostheses can be significantly improved by detecting specific sensory events related to the ongoing motor task (e.g., the slippage of an object during grasping). Algorithms have been developed to achieve this goal by processing electroneurographic (ENG) afferent signals recorded by using single-channel cuff electrodes. However, no efforts have been made so far to understand the number and type of detectable sensory events that can be differentiated from whole nerve recordings using this approach.

Methods

To this aim, ENG afferent signals, evoked by different sensory stimuli were recorded using single-channel cuff electrodes placed around the sciatic nerve of anesthetized rats. The ENG signals were digitally processed and several features were extracted and used as inputs for the classification. The work was performed on integral datasets, without eliminating any noisy parts, in order to be as close as possible to real application.

Results

The results obtained showed that single-channel cuff electrodes are able to provide information on two to three different afferent (proprioceptive, mechanical and nociceptive) stimuli, with reasonably good discrimination ability. The classification performances are affected by the SNR of the signal, which in turn is related to the diameter of the fibers encoding a particular type of neurophysiological stimulus.

Conclusions

Our findings indicate that signals of acceptable SNR and corresponding to different physiological modalities (e.g. mediated by different types of nerve fibers) may be distinguished.

Consumer design priorities for upper limb prosthetics

PURPOSE

To measure consumer satisfaction with upper limb prosthetics and provide an enumerated list of design priorities for future developments.

METHODS

A self-administered, anonymous survey collected information on participant demographics, history of and goals for prosthesis use, satisfaction, and design priorities. The questionnaire was available online and in paper format and was distributed through healthcare providers, community support groups, and one prosthesis manufacturer; 242 participants of all ages and levels of upper limb absence completed the survey.

RESULTS

Rates of rejection for myoelectric hands, passive hands, and body-powered hooks were 39%, 53%, and 50%, respectively. Prosthesis wearers were generally satisfied with their devices while prosthesis rejecters were dissatisfied. Reduced prosthesis weight emerged as the highest priority design concern of consumers. Lower cost ranked within the top five design priorities for adult wearers of all device types. Life-like appearance is a priority for passive/cosmetic prostheses, while improved harness comfort, wrist movement, grip control and strength are required for body-powered devices. Glove durability, lack of sensory feedback, and poor dexterity were also identified as design priorities for electric devices.

CONCLUSIONS

Design priorities reflect consumer goals for prosthesis use and vary depending on the type of prosthesis used and age. Future design efforts should focus on the development of more light-weight, comfortable prostheses.

The roles of predisposing characteristics, established need, and enabling resources on upper extremity prosthesis use and abandonment

PURPOSE

Prosthesis use and abandonment is a complex function of variables defining the contextualized individual. This review presents a comprehensive panoramic of these factors as related to the management of upper limb deficiency. Me

METHOD

nderson's model for health service utilization was used to frame prosthesis use and abandonment as a function of (1) predisposing characteristics of the individual (e.g. gender or level of limb loss); (2) established need, as characterized by lifestyle- and age-related demands; and (3) enabling resources (e.g. clinical and social). English-language articles pertaining to these components were identified in a search of Ovid, PubMed, ISI Web of Science and www.scholar.google.com (1980-November 2006) for key words upper limb and prosthesis. Approximately 90 articles were included as evidence in this review. Re

RESULTS

ersonal and contextual factors are critical determinants of prosthesis acceptance. While the influence of some factors (i.e. lifestyle, level of limb loss), is strongly supported in the literature, the impact of others, (i.e. age of fitting, efficacy of training protocols), remain controversial. Co

CONCLUSIONS

nhanced understanding of these factors is required to optimize clinical practices, guide design efforts, and satiate demand for evidence-based measures of intervention. Future research should comprise of controlled, multifactor studies adopting standardized outcome measures and providing comprehensive descriptions of population characteristics.

Bidirectional interfaces with the peripheral nervous system

Considerable scientific and technological efforts have been devoted to develop neuroprostheses and hybrid bionic systems that link the human nervous system with electronic or robotic prostheses, with the main aim of restoring motor and sensory functions in disabled patients. Such developments have also the potential to be applied to normal human beings to improve their physical capabilities for bidirectional control and feedback of machines. A number of neuroprostheses use interfaces with peripheral nerves or muscles for neuromuscular stimulation and signal recording. This chapter provides a general overview of the peripheral neural interfaces available and their use from research to clinical application in controlling artificial and robotic prostheses and in developing neuroprostheses. Extraneural electrodes, such as cuff and epineurial electrodes, provide simultaneous interface with many axons in the nerve, whereas intrafascicular, penetrating, and regenerative electrodes may selectively contact small groups of axons within a nerve fascicle. Biological and technical issues are reviewed relative to the problems of electrode design and tissue injury. The last sections review different strategies for the use of peripheral neural interfaces in biomedical applications.

A shape memory alloy-based tendon-driven actuation system for biomimetic artificial fingers, part I: design and evaluation

In this paper, a new biomimetic tendon-driven actuation system for prosthetic and wearable robotic hand applications is presented. It is based on the combination of compliant tendon cables and one-way shape memory alloy (SMA) wires that form a set of agonist–antagonist artificial muscle pairs for the required flexion/extension or abduction/adduction of the finger joints. The performance of the proposed actuation system is demonstrated using a 4 degree-of-freedom (three active and one passive) artificial finger testbed, also developed based on a biomimetic design approach. A microcontroller-based pulse-width-modulated proportional-derivation (PWM-PD) feedback controller and a minimum jerk trajectory feedforward controller are implemented and tested in anad hocfashion to evaluate the performance of the finger system in emulating natural joint motions. Part II describes the dynamic modeling of the above nonlinear system, and the model-based controller design.

Upper limb amputees can be induced to experience a rubber hand as their own

We describe how upper limb amputees can be made to experience a rubber hand as part of their own body. This was accomplished by applying synchronous touches to the stump, which was out of view, and to the index finger of a rubber hand, placed in full view (26 cm medial to the stump). This elicited an illusion of sensing touch on the artificial hand, rather than on the stump and a feeling of ownership of the rubber hand developed. This effect was supported by quantitative subjective reports in the form of questionnaires, behavioural data in the form of misreaching in a pointing task when asked to localize the position of the touch, and physiological evidence obtained by skin conductance responses when threatening the hand prosthesis. Our findings outline a simple method for transferring tactile sensations from the stump to a prosthetic limb by tricking the brain, thereby making an important contribution to the field of neuroprosthetics where a major goal is to develop artificial limbs that feel like a real parts of the body.

Classification of afferent signals recorded with a single cuff electrode

The implementation of systems to restore sensorimotor functions in person with neurological disabilities is an important research area. In the past, many studies have been carried out to develop closed-loop neuroprostheses based on the processing of electroneurographic (ENG) signals recorded from physiological sensors using cuff electrodes. However, the potential of this approach is not completely clear. In this paper, an artificial neural network is used to discriminate afferent ENG signals evoked by different mechanical stimuli and recorded with a single cuff electrode. The preliminary results indicate that even single cuff ENG signals can be useful to extract interesting information with good performance. In the future, the possibility of discriminating additional stimuli using additional channels and more advanced classification techniques will be investigated.

Upper limb prosthesis use and abandonment: a survey of the last 25 years

This review presents an analytical and comparative survey of upper limb prosthesis acceptance and abandonment as documented over the past 25 years, detailing areas of consumer dissatisfaction and ongoing technological advancements. English-language articles were identified in a search of Ovid, PubMed, and ISI Web of Science (1980 until February 2006) for key words upper limb and prosthesis. Articles focused on upper limb prostheses and addressing: (i) Factors associated with abandonment; (ii) Rejection rates; (iii) Functional analyses and patterns of wear; and (iv) Consumer satisfaction, were extracted with the exclusion of those detailing tools for outcome measurement, case studies, and medical procedures. Approximately 200 articles were included in the review process with 40 providing rates of prosthesis rejection. Quantitative measures of population characteristics, study methodology, and prostheses in use were extracted from each article. Mean rejection rates of 45% and 35% were observed in the literature for body-powered and electric prostheses respectively in pediatric populations. Significantly lower rates of rejection for both body-powered (26%) and electric (23%) devices were observed in adult populations while the average incidence of non-wear was similar for pediatric (16%) and adult (20%) populations. Documented rates of rejection exhibit a wide range of variance, possibly due to the heterogeneous samples involved and methodological differences between studies. Future research should comprise of controlled, multifactor studies adopting standardized outcome measures in order to promote comprehensive understanding of the factors affecting prosthesis use and abandonment. An enhanced understanding of these factors is needed to optimize prescription practices, guide design efforts, and satiate demand for evidence-based measures of intervention.

Neuromuscular electrical stimulation in neurorehabilitation

This review provides a comprehensive overview of the clinical uses of neuromuscular electrical stimulation (NMES) for functional and therapeutic applications in subjects with spinal cord injury or stroke. Functional applications refer to the use of NMES to activate paralyzed muscles in precise sequence and magnitude to directly accomplish functional tasks. In therapeutic applications, NMES may lead to a specific effect that enhances function, but does not directly provide function. The specific neuroprosthetic or "functional" applications reviewed in this article include upper- and lower-limb motor movement for self-care tasks and mobility, respectively, bladder function, and respiratory control. Specific therapeutic applications include motor relearning, reduction of hemiplegic shoulder pain, muscle strengthening, prevention of muscle atrophy, prophylaxis of deep venous thrombosis, improvement of tissue oxygenation and peripheral hemodynamic functioning, and cardiopulmonary conditioning. Perspectives on future developments and clinical applications of NMES are presented.

A critical review of interfaces with the peripheral nervous system for the control of neuroprostheses and hybrid bionic systems

Considerable scientific and technological efforts have been devoted to develop neuroprostheses and hybrid bionic systems that link the human nervous system with electronic or robotic prostheses, with the main aim of restoring motor and sensory functions in disabled patients. A number of neuroprostheses use interfaces with peripheral nerves or muscles for neuromuscular stimulation and signal recording. Herein, we provide a critical overview of the peripheral interfaces available and trace their use from research to clinical application in controlling artificial and robotic prostheses. The first section reviews the different types of non-invasive and invasive electrodes, which include surface and muscular electrodes that can record EMG signals from and stimulate the underlying or implanted muscles. Extraneural electrodes, such as cuff and epineurial electrodes, provide simultaneous interface with many axons in the nerve, whereas intrafascicular, penetrating, and regenerative electrodes may contact small groups of axons within a nerve fascicle. Biological, technological, and material science issues are also reviewed relative to the problems of electrode design and tissue injury. The last section reviews different strategies for the use of information recorded from peripheral interfaces and the current state of control neuroprostheses and hybrid bionic systems.

Electroactive polymeric sensors in hand prostheses: bending response of an ionic polymer metal composite

In stark contrast to the inspiring functionality of the natural hand, limitations of current upper limb prostheses stemming from marginal feedback control, challenges of mechanical design, and lack of sensory capacity, are well-established. This paper provides a critical review of current sensory systems and the potential of a selection of electroactive polymers for sensory applications in hand prostheses. Candidate electroactive polymers are reviewed in terms of their relevant advantages and disadvantages, together with their current implementation in related applications. Empirical analysis of one of the most novel electroactive polymers, ionic polymer metal composites (IPMC), was conducted to demonstrate its potential for prosthetic applications. With linear responses within the operating range typical of hand prostheses, bending angles, and bending rates were accurately measured with 4.4+/-2.5 and 4.8+/-3.5% error, respectively, using the IPMC sensors. With these comparable error rates to traditional resistive bend sensors and a wide range of sensitivities and responses, electroactive polymers offer a promising alternative to more traditional sensory approaches. Their potential role in prosthetics is further heightened by their flexible and formable structure, and their ability to act as both sensors and actuators.

On the Development of a Biomechatronic System to Record Tendon Sliding Movements

The main goal of this paper is to study the feasibility of a novel implantable micro-system able to record information about tendon sliding movements by using contactless measurement devices (magnetic sources and sensors). The system, named "Biomechatronic Position Transducer" (BPT), can be used for the implementation of advanced control strategies in neuroprostheses. After a preliminary analysis based on finite element model simulations, an experimental setup was developed in order to simulate the recording conditions (the sensors fixed to the bones and the magnetic sources placed on the tendons). In order to limit the number of implanted components of the system, a fuzzy Mamdani-like architecture was developed to extract the information from the raw data. The results confirm the possibility of using the presented approach for developing an implantable micro-sensor able to extract kinematic information useful for the control of neuroprostheses. Future works will go in the direction of integrating and testing the sensors and the electronic circuitry (to provide power supply and to record the data) during in vitro and in situ experiments.