Pilot studies suggesting new applications of NiTi in dynamic orthoses for the ankle joint

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.