No abstract

This study investigates cortical involvement during ankle passive mobilization in healthy subjects, and is part of a pilot study on stroke patient rehabilitation. Magnetoencephalographic signals from the primary sensorimotor areas devoted to the lower limb were collected together with simultaneous electromyographic activities from tibialis anterior (TA). This was done bilaterally, on seven healthy subjects (aged 29 ± 7), during rest, left and right passive ankle dorsiflexion (imparted through the SHADE orthosis, O-PM, or neuromuscular electrical stimulation, NMES-PM), and during active isometric contraction (IC-AM). The effects of focussing attention on ankle passive movements were considered. Primary sensory (FS(S1)) and motor (FS(M1)) area activities were discriminated by the Functional Source Separation algorithm. Only contralateral FS(S1) was recruited by common peroneal nerve stimulation and only contralateral FS(M1) displayed coherence with TA muscular activity. FS(M1) showed higher power of gamma rhythms (33-90 Hz) than FS(S1). Both sources displayed higher beta (14-32 Hz) and gamma powers in the left than in the right hemisphere. Both sources displayed a bilateral reduction of beta power during IC-AM with respect to rest. Only FS(S1) beta band power reduced during O-PM. No beta band modulation was observed of either source during NMES-PM. Mutual FS(S1)-FS(M1) coherence in gamma2 band (61-90 Hz) showed a slight trend towards an increase when focussing attention during O-PM. Somatosensory and motor counterparts of lower limb cortical representations were discriminated in both hemispheres. SHADE was effective in generating repeatable dorsiflexion and inducing primary sensory involvement similarly to voluntary movement.

Acute post-stroke rehabilitation protocols include passive mobilization as a means to prevent contractures. A device (SHADE) that provides repetitive passive motion to a flaccid ankle by using shape memory alloy actuators could be of great help in providing this treatment. A suitable actuator was designed as a cartridge of approximately 150 3 20 3 15 mm, containing 2.5 m of 0.25 mm diameter NiTi wire. This actuator was activated by JouleÕs effect employing a 7 s current input at 0.7 A, which provided 10 N through 76 mm displacement. Cooling and reset by natural convection took 30 s. A prototype of SHADE was assembled with two thermoplastic shells hinged together at the ankle and strapped on the shin and foot. Two actuators were fixed on the upper shell while an inextensible thread connected each NiTi wire to the foot shell. The passive ankle motion (passive range of motion, PROM) generated by SHADE was evaluated optoelectronically on three flaccid patients (58 ± 5 years old); acceptability was assessed by a questionnaire presented to further three flaccid patients (44 ± 11.5 years old) who used SHADE for 5 days, 30 min a day. SHADE was well accepted by all patients, produced good PROM, and caused no pain. The results prove that suitable limb mobilization can be produced by SMA actuators.

NiTi is a metal alloy with unconventional functional characteristics: Shape memory and pseudoelasticity. Its use in the field of rehabilitation is very innovative. This work presents applications in lower limb orthotics. Three different devices were assembled and tested: An equinus gait dynamic splint, a compliant ankle positioning brace, and a dual-mode haptic/active exerciser for the dorsiflexors. Results are derived from technical and preclinical trials. The gait splint improves several walking parameters even better than a traditional flexible ankle-foot orthoses (AFO). In particular, it supports mid-stance and propulsion biomechanics and affects physiological activation of tibialis anterior during swing much less than posterior leaf AFO. The haptic/active exerciser, able to provide dorsiflexion through a suitable articular range, could be controlled on the basis of minimal surface electromyographic (sEMG) signals, suggesting its use as an aid for early active workouts as soon as patients start to recover voluntary control of tibialis anterior. Further evidence must be sought in future to confirm for the ankle joint the promising results obtained in repositioning applications in prior upper limb studies. The work done so far on the tested prototypes is encouraging: Material characteristics and dimensioning will be optimized so that customized NiTi devices can be prescribed to best meet individual patients' requirements.

No abstract

The capacity of flexing oneÕs ankle is an indispensible segment of gait re-learning, as imbalance, wrong compensatory use of other joints and risk of falling may depend on the so-called drop-foot. The rehabilitation of ankle dorsiflexion may be achieved through active exercising of the relevant musculature (especially tibialis anterior, TA). This can be troublesome for patients affected by weakness and flaccid paresis. Thus, as needs evolve during patientÕs improvements, a therapeutic device should be able to guide and sustain gradual recovery by providing commensurate aid. This includes exploiting even initial attempts at voluntary motion and turns those into effective workout. An active orthosis powered by two rotary actuators containing NiTi wire was designed to obtain ankle dorsiflexion. A computer routine that analyzes the electromyographic (sEMG) signal from TA muscle is used to control the orthosis and trigger its activation. The software also provides instructions and feed-back for the patient. Tests on the orthosis proved that it can produce strokes up to 36°against resisting torques exceeding 180 Ncm. Three healthy subjects were able to control the orthosis by modulating their TA sEMG activity. The movement produced in the preliminary tests is interesting for lower limb rehabilitation, and will be further improved by optimizing bodyorthosis interface. It is hoped that this device will enhance early rehabilitation and recovery of ankle mobility in stroke patients.

A compliant brace (EDGES) promoting spastic elbow relaxation was designed to investigate the potentialities of pseudoelastic NiTi in orthotics. By exploiting its peculiar characteristics, EDGES could improve elbow posture without constraining movements and thus avoiding any pain to the patient. A commercial Ni 50.7 -Ti 49.3 alloy heat treated at 400°C 1 h + WQ was selected for this application. A prototype of EDGES was assembled with two thermoplastic shells connected by polycentric hinges. Four 2-mm-diameter NiTi bars were encastred in the upper-arm shell and let slide along tubular fixtures on the forearm. Specially designed bending tests demonstrated suitable moment-angle characteristics. Two post-stroke subjects (aged 62 and 64, mild elbow flexors spasticity) wore EDGES for 1 week, at least 10 h a day. No additional treatment was applied during this period or the following week. A great improvement (20°± 5°) of the resting position was observed in both patients as early as 3 h after starting the treatment. Acceptability was very good. A slight decrease in spasticity was also observed in both subjects. All the effects disappeared 1 week after discontinuation. EDGES appears to be a good alternative to traditional orthoses in terms of acceptability and effectiveness in improving posture, especially whenever short-term splinting is planned.

Actuators based on standard technologies often do not comply with environmental constraints on electromagnetic noise. Even though shape memory actuators are not ferromagnetic, activation by Joule’s effect poses a question about magnetic compatibility. This article presents a new concept design of a rotary actuator based on a double coil of NiTi wire, which permits to abate dramatically the electromagnetic fields generated. A particular implementation of the idea was devised as a case study to investigate feasibility. The desired torque and stroke were 83 N cm and 40°, respectively, and mechanical tests confirmed that a maximal stroke of 38° can be achieved for resisting torques ranging from 33 to 122 N cm. The built prototype proved appropriate to respond to the needs of a neuroscience study requiring mobilization of the ankle. So, this device was tested during measurement of brain activity in healthy subjects with both magnetoencephalography and functional magnetic resonance imaging, that is, diagnostic equipment with very demanding constraints on electromagnetic noise. Neither magnetoencephalography signals nor the functional magnetic resonance imaging images were affected by any electromagnetic noise or artifacts, allowing for further analysis and extraction of neurological features. Besides the discussed uses, this type of actuator could find an application in several fields, such as biomedical, robotic, aerospace, or automotive.