Forskning

This review of electrical peripheral nerve stimulation found that electrodes which attach around the outside of the nerve have superior long-term stability compared to electrodes which pierce the nerve. In reviewing animal and human studies, we found that stimulation frequencies below 30 Hz and with less than 50% active stimulation time are considered safe for long-term use. Other safety limitations depend on the geometry and arrangement of electrodes in the body, and thus further investigation is needed. These conclusions help to ensure the health and safety of the neural tissues and the individuals using these technologies, allowing such sensory feedback to continue to be used long-term and in daily life.

Osseointegrated transradial prostheses have the potential to preserve the natural range of wrist rotation, which improves the performance of activities of daily living and reducescompensatorymovements that potentially lead to secondary health problems over time. This is possible by enabling the radius and the ulna bone to move with respect to each other, restoring the functionality of the original distal-radioulnar joint. In this paper, we report on psychophysics tests performed on an osseointegrated transradial amputee with the aim to understand the extent of mobility of the implants that is required to preserve the natural forearm rotation. Based on these experiments, we designed and developed an attachment device between the implants and the hand prosthesis that serves as an artificial distal radio-ulnar joint. This device was fitted on an osseointegrated transradial amputee and its functionality assessed by means of the Southampton Hand Assessment Procedure (SHAP) and the Minnesota Manual Dexterity test (MMDT). We found that the axial rotation of the implants is required to preserve forearm rotation, to distribute loads equally over the two implants (60% radius – 40% ulna), and to enable loading of the implants without unpleasant feelings for the patient. Higher function was recorded when our attachment device enabled forearmrotation: SHAP from 61 to 71, MMDT from 258s to 231s. Natural forearm rotation can be successfully restored in transradial amputees by using osseointegration and our novel mechanical attachment to the hand prosthesis.

Controlling a vehicle with signals from the body can give individuals with missing limbs, loss of muscle function, or weak muscles, the opportunity to become independent. In this study, muscle contractions are translated into commands to control a drone. Three different types of control for collision avoidance were tested. All three types performed well, and the drone was able to avoid all obstacles.

The underlying mechanism of phantom limb pain (PLP) is poorly understood. This article discusses PLP in relation to available clinical findings. An alternative hypothesis for PLP is proposed: that the disruption following an amputation result in the pain system becoming coactivated with the sensorimotor system belonging to the missing limb. An implication of this hypothesis is that training of phantom movements through phantom motor execution could disentangle the motor system from pain, resulting in a reduction of PLP.

Conventionally, a prosthesis arm is controlled via the signals from contracting the muscle remaining after the amputation. Rerouting nerves to some of these remaining muscles allows the patient to generate additional control signals, thereby improving the functionality of the prosthesis. We showed an improvement of signal-quality of these new control signals over time in two patients, which resulted in more reliable control of their prosthesis.

When filtering multi-channel EMG recordings, it is important to distinguish between correlations caused by crosstalk versus co-activation of muscles. Ideally, we wish to remove the crosstalk component from the signal. Under the assumption that impedance in volume conductors is resistive, we can use principal component analysis to separate crosstalk from co-activation for multi-channel EMG recordings in surface electrodes.

Phantom limb pain (PLP) is a chronic condition that can greatly diminish quality of life. Control over the phantom limb and exercise of such control have been hypothesised to reverse maladaptive brain changes correlated to PLP. Preliminary investigations have shown that decoding motor volition using myoelectric pattern recognition, while providing real-time feedback via virtual and augmented reality (VR-AR), facilitates phantom motor execution (PME) and reduces PLP. Here we present the study protocol for an international (seven countries), multicentre (nine clinics), double-blind, randomised controlled clinical trial to assess the effectiveness of PME in alleviating PLP. Sixty-seven subjects suffering from PLP in upper or lower limbs are randomly assigned to PME or phantom motor imagery (PMI) interventions. Subjects allocated to either treatment receive 15 interventions and are exposed to the same VR-AR environments using the same device. The only difference between interventions is whether phantom movements are actually performed (PME) or just imagined (PMI). Complete evaluations are conducted at baseline and at intervention completion, as well as 1, 3 and 6 months later using an intention-to-treat (ITT) approach. Changes in PLP measured using the Pain Rating Index between the first and last session are the primary measure of efficacy. Secondary outcomes include: frequency, duration, quality of pain, intrusion of pain in activities of daily living and sleep, disability associated to pain, pain self-efficacy, frequency of depressed mood, presence of catastrophising thinking, health- related quality of life and clinically significant change as patient’s own impression. Follow-up interviews are conducted up to 6 months after the treatment.

Direct skeletal attachment of lower limb prostheses ensures direct load transfer between the prosthetic leg and the skeleton. Knowledge of the load characteristics at the boneimplant interface during high-loading activities is needed to understand the limitations of current implant systems, as well as to inform their future development. The present study estimates the load scenario at the bone-implant interface of a transfemoral amputee while running with kinematic symmetry between the prosthetic and the intact limbs corresponding to that of an ablebodied subject. Kinematic symmetry was used as this represents the ultimate aim of advanced bionic legs. Kinematic data and ground reaction forces from a running trial of an able-bodied subject were matched to a musculoskeletal model of a transfemoral amputee. The joint reaction forces at the boneimplant interface were calculated using inverse dynamics. The normalized peak forces and moments during a single gait cycle were calculated to 153 % BW (body weight) / -14.8 % BWm, 186 % BW / 16.2 % BWm and 56.8 % BW / -18.7 % BWm for the x- (anterior), y- (longitudinal), and z-axis (lateral-medial), respectively. These findings can potentially be used as design input for future implant systems and external safety devices.

A central challenge for myoelectric limb prostheses resides in the fact that, as the level of amputation becomes more proximal, the number of functions to be replaced increases, while the number of muscles available to collect input signals for control decreases. Differential activation of compartments from a single muscle could provide additional control sites. However, such feat is not naturally under voluntary control. In this study, we investigated the feasibility of learning to differentially activate the two heads of the bicep brachii muscle (BBM), by using biofeedback via high-density surface electromyography (HD-sEMG). Using a one degree of freedom Fitts’ law test, we observed that eight subjects could learn to control the center of gravity of BBM’s myoelectric activity. In addition, we examined the activations patterns of BBM that allow for the decoding of distal hand movements. These patterns were found highly individual, but different enough to allow for decoding of motor volition of distal joints. These findings represent promising venues to increase the functionality of myoelectrically controlled upper limb prostheses.

EMG-based biofeedback training was administered to the patient with conversion disorder for improving motor impairment of the upper limb without any physical damage. Three months training brought dramatically improvement to muscle activity of her affected forearm. This study shows the efficacy of EMG-based biofeedback training for motor impairment caused by psychological problem.