Pseudoelastic Nitinol-Based Device for Relaxation of Spastic Elbow in Stroke Patients

Abstract

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.

Pilot Studies Suggesting New Applications of NiTi in Dynamic Orthoses for the Ankle Joint

“…For this reason, we shall also quote some previous pre-clinical evidence relating to an upper limb orthosis of the same type. In that study by our group 11 we found that an application of just a few hours could lead to an improvement of the resting elbow angle. Further exposition to the same therapy produced even better results after a week, with also a possible reduction on spastic tension of the limb.…”

Shape Memory Actuators for Medical Rehabilitation and Neuroscience

“…Static orthoses are often used to impart these treatments and may be as rigid as castings or partially compliant. Many authors imagined the use of SMA in orthotics as passive components that apply static corrective forces [20][21][22][23][24][25][26][27][28][29][30]. In these applications SMA are mostly employed for their pseudoelastic properties, even though some designs are also based on SME.…”

“…In these applications SMA are mostly employed for their pseudoelastic properties, even though some designs are also based on SME. A series of papers [20][21][22][23][24][25] showed applications of pseudoelastic NiTi for spastic limb repositioning (elbow, ankle). The authors suggest that pseudoelasticity can be an interesting solution to the disuse and immobility problems during the orthotic repositioning therapies, in that it safeguards residual motor capabilities (voluntary or reflex) and decreases contact pressure by yielding under muscular jerks.…”

Applications of Shape Memory Alloys for Neurology and Neuromuscular Rehabilitation

“…There are a number of groups who have been developing ideas and devices exploiting SMA for imparting forces on or producing movements of body parts, especially with the aim of assisting or replacing lost functions. The most relevant experiences address biomedical problems, such as the mobilization of paralyzed hands, fingers (e.g., [ 7 , 8 , 9 ]) and other segments [ 10 ], the support of gait (e.g., [ 11 , 12 , 13 , 14 , 15 ]) and limb repositioning [ 16 ]. The corpus of published literature highlights the promising aspects of SMA technology [ 17 ] and also describes the limitations connected with those materials.…”