Assessment of an automatic prosthetic elbow control strategy using residual limb motion for transhumeral amputated individuals with socket or osseointegrated prostheses

International audienceMost transhumeral amputated individuals deplore the lack of functionality of their prosthesis due to control-related limitations. Commercialized prosthetic elbows are controlled via myoelectric signals, yielding complex control schemes when users have to control an entire prosthetic limb. Limited control yields the development of compensatory strategies. An alternative control strategy associates residual limb motions to automatize the prosthetic elbow motion using a model of physiological shoulder/elbow synergies. Preliminary studies have shown that elbow motion could be predicted from residual limb kinematic measurements, but results with transhumeral amputated individuals were lacking. This study focuses on the experimental assessment of automatic prosthetic elbow control during a reaching task, compared to conventional myoelectric control, with six transhumeral amputated individuals, among whom, three had an osseointegrated device. Part of the recruited participants had an osseointegrated prosthetic device. The task was achieved within physiological precision errors with both control modes. Automatic elbow control reduced trunk compensations, and restored a physiologically-like shoulder/elbow movement synchronization. However, the kinematic assessment showed that amputation and prosthesis wear modifies the shoulder movements in comparison with physiological shoulder kinematics. Overall, participants described the automatic elbow control strategy as intuitive, and this work highlights the interest of automatized prosthetic elbow motion

Phantom-Mobility-Based Prosthesis Control in Transhumeral Amputees Without Surgical Reinnervation: A Preliminary Study

Transhumeral amputees face substantial difficulties in efficiently controlling their prosthetic limb, leading to a high rate of rejection of these devices. Actual myoelectric control approaches make their use slow, sequential and unnatural, especially for these patients with a high level of amputation who need a prosthesis with numerous active degrees of freedom (powered elbow, wrist, and hand). While surgical muscle-reinnervation is becoming a generic solution for amputees to increase their control capabilities over a prosthesis, research is still being conducted on the possibility of using the surface myoelectric patterns specifically associated to voluntary Phantom Limb Mobilization (PLM), appearing naturally in most upper-limb amputees without requiring specific surgery. The objective of this study was to evaluate the possibility for transhumeral amputees to use a PLM-based control approach to perform more realistic functional grasping tasks. Two transhumeral amputated participants were asked to repetitively grasp one out of three different objects with an unworn eight-active-DoF prosthetic arm and release it in a dedicated drawer. The prosthesis control was based on phantom limb mobilization and myoelectric pattern recognition techniques, using only two repetitions of each PLM to train the classification architecture. The results show that the task could be successfully achieved with rather optimal strategies and joint trajectories, even if the completion time was increased in comparison with the performances obtained by a control group using a simple GUI control, and the control strategies required numerous corrections. While numerous limitations related to robustness of pattern recognition techniques and to the perturbations generated by actual wearing of the prosthesis remain to be solved, these preliminary results encourage further exploration and deeper understanding of the phenomenon of natural residual myoelectric activity related to PLM, since it could possibly be a viable option in some transhumeral amputees to extend their control abilities of functional upper limb prosthetics with multiple active joints without undergoing muscular reinnervation surgery

Phantom Sensations Influenced by Global and Local Modifications of the Prosthetic Socket as a Potential Solution for Natural Somatosensory Feedback During Walking: A Preliminary Study of a Single Case

Following lower limb amputation, amputees are trained to walk with a prosthesis. The loss of a lower limb deprives them of essential somatosensory information, which is one of the causes of the difficulties of walking with a prosthesis. We here explored whether a solution to this lack of somatosensory feedback could come from natural sensations of the phantom limb, present in most amputees, instead of from substitutive technologies. Indeed, it is known that phantom sensations can be modulated by (i) global mechanical characteristics of the prosthesis socket, and (ii) locally applying a stimulus on an area of the residual limb. The purpose of this pilot study was to verify the feasibility of influencing phantom sensations via such socket modifications in a participant with transfemoral amputation. Four prosthetic interface conditions were studied: a rigid and a semi-rigid socket, each one with and without a focal pressure increase on a specific area of the residual limb. The results show that phantom sensations during walking were different according to the 4 interface conditions. The participant had more vivid phantom sensations in his foot and calf of which some varied as a function of the gait phases. Preliminary gait analysis with wearable sensors shows that these modifications were accompanied by changes in some gait spatiotemporal parameters. This preliminary study of single case demonstrates that phantom sensations can be modulated by the prosthetic interface and can provide natural somatosensory information dynamically varying with gait phases. Although this needs to be confirmed for a larger population of lower limb amputees, it already encourages non-painful phantom sensations to be considered early during the rehabilitation of lower limb amputees

Reducing Sitting Time After Stroke: A Phase II Safety and Feasibility Randomized Controlled Trial. ( Presented in part as a poster to the European Stroke Organization, April 17–19, 2015, Glasgow, United Kingdom; and Stroke 2015 (a combined conference of the Stroke Society of Australasia and Smartstrokes NSW), September 1–5, 2015, Melbourne, VIC, Australia.)

OBJECTIVE: To test the safety, feasibility, and effectiveness of reducing sitting time in stroke survivors. DESIGN: Randomized controlled trial with attention-matched controls and blinded assessments. SETTING: Community. PARTICIPANTS: Stroke survivors (N=35; 22 men; mean age, 66.9±12.7y). INTERVENTIONS: Four counseling sessions over 7 weeks with a message of sit less and move more (intervention group) or calcium for bone health (attention-matched control group). MAIN OUTCOME MEASURES: Measures included safety (adverse events, increases in pain, spasticity, or fatigue) and feasibility (adherence to trial protocol). Secondary measures included time spent sitting (including in prolonged bouts ≥30min), standing, and stepping as measured by the thigh-worn inclinometer (7d, 24h/d protocol) and time spent in physical activity of at least moderate intensity as measured by a triaxial accelerometer. The Multimedia Activity Recall for Children and Adults was used to describe changes in use of time. RESULTS: Thirty-three participants completed the full protocol. Four participants reported falls during the intervention period with no other adverse events. From a baseline average of 640.7±99.6min/d, daily sitting time reduced on average by 30±50.6min/d (95% confidence interval [CI], 5.8-54.6) in the intervention group and 40.4±92.5min/d in the control group (95% CI, 13.0-93.8). Participants in both groups also reduced their time spent in prolonged sitting bouts (≥30min) and increased time spent standing and stepping. CONCLUSIONS: Our protocol was both safe and feasible. Participants in both groups spent less time sitting and more time standing and stepping postintervention, but outcomes were not superior for intervention participants. Attention matching is desirable in clinical trials and may have contributed to the positive outcomes for control participants

Déconditionnement et réentraînement à l'effort chez des hémiplégiques d'origine vasculaire (Evaluation à court et moyen termes des effets d'un réentraînement à l'effort sur les capacités, les performances et la qualité de vie)

Objectifs : De nombreuses études mettent en évidence qu'un programme de réentraînernent à l'effort en post AVC peut améliorer les capacités à l'effort et les capacités fonctionnelles à court terme. L'objectif de ce travail est d'évaluer l'évolution de la capacité à l'effort, de la capacité de marche, des performances en milieu ordinaire et de la qualité de vie de patients hémiplégiques pendant un programme de réentraînement et à 3 mois de l'arrêt. Matériel et méthode : Un réentraînernent à l'effort personnalisé est réalisé chez 9 patients hémiplégiques d'origine vasculaire. Les données concernant la capacité à l'effort, l'endurance à la marche, le niveau d'activité en milieu ordinaire, la qualité de vie et la fatigue sont recueillies de façon prospective avant le début du réentraînernent, pendant le programme, immédiatement après et à 3 mois de l'arrêt du programme. L'estimation de l'activité en milieu ordinaire repose sur des renseignements objectifs obtenus par monitorage d'activité et sur des informations subjectives recueillies par autoquestionnaires. Résultats : A court terme, le réentraînement améliore significativement les capacités du patient (capacité à l'effort et capacités de marche). Ces améliorations ne sont que peu utilisées en milieu ordinaire : l'observance d'une activité physique régulière est modérée. A moyen terme, l'observance est faible et la capacité à l'effort a tendance à diminuer pour les patients les moins actifs. Discussion : Les effets du réentraînernent sur les capacités ont tendance à diminuer à distance de l'arrêt du programme. Cela est probablement lié à une faible observance de l'activité prescrite. L'utilisation d'un monitorage de l'activité locomotrice par accélérométrie pour évaluer l'évolution du profil d'activité permet de mettre en évidence une dissociation entre capacités et performances et d'évaluer l'observance des patients de façon objective. L'éducation thérapeutique doit être àméliorée pour favoriser la poursuite d'une activité physique régulière et permettre ainsi le maintien de l'amélioration des capacités. Conclusion : Des études complémentaires sont nécessaires pour identifier la population à laquelle un réentraînement peut être proposé et les éléments prédictifs d'efficacité du réentraînement et de l'éducation thérapeutique à court et moyen termes.NANCY1-Bib. numérique (543959902) / SudocSudocFranceF

Neuroplasticité après amputation : Phénomènes fonctionnels et conséquences pour la réadaptation

Une amputation a comme conséquence la privation soudaine d'entrées sensorielles au niveau du système nerveux central ainsi que la perte de cibles musculaires pour les fibres efférentes. Le système nerveux central, avec sa grande capacité d'adaptation, réagit à cette privation par une réorganisation anatomique et fonctionnel à différentes échelles de temps. Ce papier résume les réorganisations fonctionnelles au niveau des aires sensorimotrices primaires suite à une amputation d'un membre. Ensuite, nous abordons les mécanismes sous-jacents au membre fantôme avec l'accent sur sa mobilité, peu connue mais répandue. Nous finissons avec l'intérêt que peut avoir la mobilité du membre fantôme pour la réadaptation de patients amputés du membre supérieur

Neuromuscular reorganization after arm amputation revealed by stump EMG evoked by different phantom movements

International audienc

Guiding the training of users with a pattern similarity biofeedback to improve the performance of myoelectric pattern recognition.

International audienceNext generation prosthetics will rely massively on myoelectric "Pattern Recognition" (PR) based control approaches , to improve their users' dexterity. One major identified factor of successful functioning of these approaches lies in the training of amputees and in their understanding of how those prosthetics works. We thus propose here an intuitive pattern similarity biofeedback which can be easily used to train amputees and allow them to optimize their muscular contractions to improve their control performance. Experiments were conducted on twenty able-bodied participants and one transradial amputee. Their performance in controlling an interface through a myoelectric PR algorithm was evaluated; before and after a short automatic user training session consisting in using the proposed visual biofeedback for ten participants, and using a generic PR algorithm output feedback for the others ten. Participants who were trained with the proposed biofeedback increased their classification score for the retrained gesture (by 39.4%), without affecting the overall classification performance (which progressed by 10.2%) through over-training and increase of False Positive rate as observed in the control group. Additional analysis indicates a clear change in contraction strategy only in the group who used the proposed biofeedback. These preliminary results highlight the potential of this method which does not focus so much on over-optimizing the pattern recognition algorithm or on physically training the users, but on providing them simple and intuitive information to adapt or change their motor strategies to solve some misclassification issues

A simple movement based control approach to ease the control of a myoelectric elbow prosthetics in transhumeral amputees

International audienceTranshumeral amputees face substantial difficulties in efficiently controlling their prosthetic limb, leading to a high rate of rejection of these devices. Actual myoelectric control approaches make their use slow, sequential and unnatural, especially for these patients with a high level of amputation who need a prosthesis with numerous active degrees of freedom (powered elbow, wrist, and hand). While surgical muscle-reinnervation is becoming a generic solution for amputees to increase their control capabilities over a prosthesis, research is still being conducted on the possibility of using the surface myoelectric patterns specifically associated to voluntary Phantom Limb Mobilization (PLM), appearing naturally in most upper-limb amputees without requiring specific surgery. The objective of this study was to evaluate the possibility for transhumeral amputees to use a PLM-based control approach to perform more realistic functional grasping tasks. Two transhumeral amputated participants were asked to repetitively grasp one out of three different objects with an unworn eight-active-DoF prosthetic arm and release it in a dedicated drawer. The prosthesis control was based on phantom limb mobilization and myoelectric pattern recognition techniques, using only two repetitions of each PLM to train the classification architecture. The results show that the task could be successfully achieved with rather optimal strategies and joint trajectories, even if the completion time was increased in comparison with the performances obtained by a control group using a simple GUI control, and the control strategies required numerous corrections. While numerous limitations related to robustness of pattern recognition techniques and to the perturbations generated by actual wearing of the prosthesis remain to be solved, these preliminary results encourage further exploration and deeper understanding of the phenomenon of natural residual myoelectric activity related to PLM, since it could possibly be a viable option in some transhumeral amputees to extend their control abilities of functional upper limb prosthetics with multiple active joints without undergoing muscular reinnervation surgery