S. Pittaccio, S. Viscuso, CNR IENI Institute for Energetics and Interphases - Italian National Research Council, Lecco, Italy
Background. The post-acute rehabilitation of stroke is clinically based on strategies for enabling the gradual re-acquisition of active ability in carrying out simple and more complex motor tasks. The rehabilitation of ankle dorsiflexion may be achieved through active exercising of the relevant musculature (especially tibialis anterior, TA). Thus a device able to guide and sustain gradual recovery from flaccid paresis by providing commensurate aid as needs evolve during patient’s improvements may be an important resource to exploit even initial attempts at voluntary motion and turn those into effective workout. Materials and methods. An active orthosis powered by two rotary actuators containing NiTi wire is used to obtain ankle dorsiflexion. The wire is wound around a spiraling sequence of pulleys and, on recovering strain, it produces rotation in much the same manner as an angling spool. Each actuator, powered at 20W, provides a stroke of up to 36°, and torques exceeding 100Ncm, when mounting 0.25mm-diameter wire. The orthosis is controlled by a home-written routine that analyses the electromyographic (EMG) signal from TA muscle and uses this as a trigger to activate the orthosis. The software also provides instructions and feed-back for the patient. Results. The system is stable. Threshold values may be selected by the therapist, so that the orthosis will only support the movement when TA-EMG indicates that the patient is actually trying to dorsiflex the ankle but the effort does not result in a proper and complete movement. Discussion and Conclusions. The application of EMG-controllable actuators based on NiTi enables patients to exercise and experience complete dorsiflexion as soon as they are able to minimally contract TA voluntarily. This provides active workout, sensorial stimulation and constant gratification. It is hoped that this device will enhance early rehabilitation and recovery of ankle mobility in stroke patients.
Summary: The post-acute rehabilitation of stroke is clinically based on strategies for enabling the gradual re-acquisition of active ability in carrying out simple and more complex motor tasks. The rehabilitation of ankle dorsiflexion may be achieved through active exercising of the relevant musculature (especially tibialis anterior, TA). Thus a device able to guide and sustain gradual recovery from flaccid paresis by providing commensurate aid as needs evolve during patient’s improvements may be an important resource to exploit even initial attempts at voluntary motion and turn those into effective workout. An active orthosis powered by two rotary actuators containing NiTi wire is used to obtain ankle dorsiflexion. The wire is wound around a spiraling sequence of pulleys and, on recovering strain, it produces rotation in much the same manner as an angling spool. Each actuator, powered at 20W, provides a stroke of up to 36°, and torques exceeding 100Ncm, when mounting 0.25mm-diameter wire. The orthosis is controlled by a home-written routine that analyses the electromyographic (EMG) signal from TA muscle and uses this as a trigger to activate the orthosis. The software also provides instructions and feed-back for the patient. The system is stable. Threshold values may be selected by the therapist, so that the orthosis will only support the movement when TA-EMG indicates that the patient is actually trying to dorsiflex the ankle but the effort does not result in a proper and complete movement. The application of EMG-controllable actuators based on NiTi enables patients to exercise and experience complete dorsiflexion as soon as they are able to minimally contract TA voluntarily. This provides active workout, sensorial stimulation and constant gratification. It is hoped that this device will enhance early rehabilitation and recovery of ankle mobility in stroke patients.
