Fig. 2. From left to right: Fisch Teflon platinum 0.4-mm piston, Teflon wire 0.6-mm piston, gold piston, wire prosthesis.
entirely of stainless steel and fastened to the incus process at the top with a handle. The prefabricated, commercially available piston prostheses replaced the intraoperatively prepared wire prostheses which were made individually by the surgeon at the operating table, in order to simplify the operation, save time and ensure a standard quality.
Marquet , in his stapedotomy review article, pointed out that there are many factors that influence the success of the procedure. It is very important that nonwettable materials (like Teflon) should be used for prostheses due to the phenomenon of surface tension. Furthermore, the prosthesis should protrude a little into the vestibule because otherwise a fibrous layer from the graft can involve the extremity of the prosthesis and cause bad functional results. The piston penetration should not exceed 400 |xm. He also refers to the footplate hole diameter, which should be 0.7 mm, so it would not touch the annular ligament but is not too small to transmit sufficient energy either. While initially the diameter of pistons used was 0.8 and 0.6 mm, from the 1970s onwards, it has been becoming even smaller, i.e. 0.3-0.4 mm. Thanks to the small diameter of a piston, it became possible to reverse the classic stapedotomy steps in the way that the footplate was perforated first and the fine piston was inserted while the stapes structure was still present and fixed to the incus process. Since these piston prostheses fitted the small footplate perforation exactly, some surgeons also dispensed the use of a vein, fascia or adipose tissue graft to cover the fenestra. The possible gap around the prosthesis was filled by blood clots, Gelfoam, connective or adipose tissue. Particularly popular among ear surgeons is the stapedotomy technique developed by Fisch , who was using the fine 0.4-mm metal wire-Teflon piston, and later platinum band-Teflon piston.
Fig. 3. Titanium-gold clip prosthesis.
Steinbach in the 1990s introduced pistons made of pure gold that have a soft band that can easily be pressed onto the incus process. Although the initial results were encouraging, gold pistons showed in some reports to have caused damage to the inner ear due to material intolerance, which resulted in granulomatous reactions and progressive postoperative sensorineural hearing loss . Another inconvenience is a relatively high percentage of implant extrusions seen in some studies .
A promising new material seems to be titanium due to its particularly good biocompatibility. Important advantages of titanium implants are their low weight (approximately 4mg), ease of handling, none or low instance of extrusion, and minimal tissue reaction, leading to a good audiometric result . Nevertheless, it should be taken into consideration that since titanium is not a noble material, it should not come into contact with steel and other materials for its ability to absorb toxic substances.
Recent refinements in the technique of stapes surgery consider the fixation of the prostheses to the incus. If the transmission of movement between the incus and prosthesis is imperfect, it can lead to incus erosion with loosening of the prosthesis and conductive hearing loss. This is the most frequent reason for revision surgery. Rigid steel wire prostheses had many disadvantages in the way of fixation and were replaced with platinum and gold band - these small soft bands can be fitted with gentle pressure around the long incus process without the spring tension inherent in steel. The titanium-gold clip prostheses, introduced by a Wengen , have an automatic fixation to the incus process through spring tension. Titanium has a shape memory, and a clip was constructed which uses this memory for fixation onto the incus (fig. 3). The combination of a Teflon shaft and a nickel-titanium alloy loop resulted in a new piston in which the crimping of the loop is activated by thermal energy, 45°C or less, using low-intensity Erbium laser or bipolar current . Some authors tend to use a drop of glass ionomer cement for additional consolidation of the piston. It is particularly useful in stapes revision operations, when the prosthesis has to be fixed again to a broken incus, as well as in malleus handle stapedectomy, where additional consolidation of the metal loop around the conical malleus handle facilitates optimal positioning of a prosthesis.
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Prof. Dr. Mislav Gjuric ORL Klinika, Salata 4 HR-10000 Zagreb (Croatia)
Tel. +385 1492 2912, Fax +385 1492 2912, E-Mail [email protected]
Arnold W, Häusler R (eds): Otosclerosis and Stapes Surgery. Adv Otorhinolaryngol. Basel, Karger, 2007, vol 65, pp 179-183
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