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Arnold W, Häusler R (eds): Otosclerosis and Stapes Surgery. Adv Otorhinolaryngol. Basel, Karger, 2007, vol 65, pp 202–205

The Crimping Problem in Stapes Surgery Pingling Kwoka, Ugo Fischb, Jürgen Strutza a Ear, Nose and Throat Department, University of Regensburg, Regensburg, Germany; bORL Center, Klinik Hirslanden, Zürich, Switzerland

Abstract Aim of the Study: The goal of this study was to compare the attachment of stapes prostheses with differently shaped loops to the long process of the incus. Method: Gold, steel/Teflon, platinum/Teflon, and two different titanium stapes prostheses were inserted in 30 specially prepared temporal bones by three experienced surgeons using the Fisch technique with the McGee crimper and straight alligator forceps for the crimping of the loops. Results: In all prostheses, a sufficiently firm attachment of the long process of the incus was achieved. The band-shaped loops showed a better contact with the incus than did the wire loops. However, the broad spiral-shaped loops led to a loss of the perpendicular axis of the piston to the long incus process. Conclusion: The geometry of the loop affects the final length of the piston in the vestibule and its angle to the long process of the incus. Copyright © 2007 S. Karger AG, Basel

In order to study the effect of the crimping process in stapes surgery, the attachment of five different stapes prostheses (fig. 1) made of titanium, gold, steel and platinum was compared in 30 especially prepared temporal bones. For the crimping of the loops to the long process of the incus, two different instruments (McGee and straight alligator forceps) were used by three experienced surgeons. The Fisch technique was used and photographs were taken with 0and 70-degree rod lens telescopes at defined views. All prostheses showed a sufficiently firm attachment to the long process of the incus.

This paper contains parts of the publication by Kwok P, Fisch U, Strutz J, May J: Stapes surgery: how precisely do different prostheses attach to the long process of the incus with different instruments and different surgeons? Otol Neurotol 2002;23:289–295.

Fig. 1. Left to right: titanium stapes prosthesis by Leibinger; gold stapes prosthesis by Kurz; platinum/Teflon stapes prosthesis by Smith & Nephew; titanium stapes prosthesis by Kurz; steel/Teflon stapes prosthesis by Smith & Nephew.

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Fig. 2. a Arrows show an S-shaped deviation of the steel loop crimped with the McGee crimper. b Titanium stapes prosthesis by Kurz: loop spiraling toward the body of the incus, loss of the perpendicular axis between the piston and the long process of the incus. c Gold stapes prosthesis by Kurz: loop spiraling towards the thin end of the incus, achieving a better axis of the piston to the long process of the incus.

The results depended on the instrument used for crimping and the material of the stapes prosthesis but not on the surgeon. Band-shaped loops had a better contact to the bone than wire loops. The steel wire showed an S-shaped deformation in one case when crimped with the McGee crimper (fig. 2a). The spirally shaped loops (titanium and gold from Kurz, Dusslingen, Germany) demonstrated very good contact with the bone of the long process of the incus, but resulted in a deviation of the perpendicular axis of the stapes piston to the long process of the incus (fig. 2b). If the spiral was pointed towards the end of the long process of the incus, a more perpendicular angle could be achieved (fig. 2c).

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Fig. 3. a Titanium stapes prosthesis by Kurz: crimped with the McGee crimper with loss of the spiral shape, the hook touching the straight part of the piston and preventing further closure of the loop. b Titanium stapes prosthesis by Kurz: crimped with the McGee crimper with loss of the spiral shape, the loop ends touch each other because of the long hook. c Titanium stapes prosthesis by Leibinger: crimped with the McGee crimper.

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b Fig. 4. a Gold stapes prosthesis by Kurz: crimped with the McGee crimper, loss of the spiral shape, S-formed deviation of loop, the beginning of the piston pushed toward the stapes footplate. b Vestibular view of the prosthesis shown in (a); the piston is too long. The arrows show the beginning and end of the protruding piston in the vestibule (piston diameter: 0.4 mm).

Regarding the instrument, a McGee crimper should not be used for crimping the spirally band-shaped loops, as this resulted in a loss of the spiral shape. The long hook of the spirally shaped loops thus prevented a complete closure of the loop around the long process of the incus (fig. 3a, b). Concerning the material, the gold loop proved to be too soft and resulted in deformations not visible in the surgical view (fig. 4a). This also led to a functional elongation of the piston, protruding further into the vestibule than desired (fig. 4b). Titanium showed a constant good attachment and less changes in the functional length of the piston than the other materials (fig. 3c).

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In conclusion, a medium-sized band-shaped nonspirally formed titanium loop with a short hook, like the titanium-Leibinger prosthesis, is found to be most suitable to be crimped to the incus. Gold is too soft causing deviations invisible during surgery. Titanium is harder than gold, preventing undesirable deviations of the loop, but malleable enough to achieve a good connection with the long process of the incus. For band-shaped loops crimping with straight alligator forceps results in a better attachment to the incus compared with the McGee crimper. Pingling Kwok, MD Ear, Nose and Throat Department, University of Regensburg Franz-Josef-Strauss-Allee 11 DE–93042 Regensburg (Germany) Tel. ⫹49 941 944 9490, Fax ⫹49 941 944 9402 E-Mail [email protected]

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