The heat-activated stapes prosthesis 'SMart' Piston: technique and preliminary results.

Since 2003 we are using in our stapedotomies the Nitinol 'Smart' Piston. This prosthesis has a Teflon 'vestibular' end and a wire shaft made by Nitinol, with a heat activated self-crimping loop. Nitinol is an alloy of Nickel + Titanium, belonging to the class of the so-called smart materials, i.e. materials with shape-memory and superelastic properties. Nitinol is lightweight and highly biocompatible thanks to the thin layer of Titanium oxide covering the Nickel surface. The special advantage of this piston is that the loop grips by itself very uniformly and quite tightly around the incudal process or the malleus handle when a minimal heating (about 60 degrees C) is applied using a disposable heater ('Thermal Tip'). This piston was successfully used in our Department between 2003 and 2004 in a first group of 42 cases of stapedotomy and in 7 cases of malleostapedotomy. The shape and the uniformity of the loop grip was controlled by examining fresh temporal bone specimens by S.E.M. (x21 / 166) and in all specimens the loop was uniformly surrounding the ossicle, without 'dead' spaces. It is our feeling that this prosthesis is very useful in stapes surgery for at least two reasons: 1. because it improves the quality of the interface 'piston loop/long process of incus'; 2. because the duration of the procedure is reduced.