Pseudoelastic Nitinol-Based Device for Relaxation of Spastic Elbow 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.