Comparison of stapes prostheses : A Retrospective analysis of individual audiometric results obtained after stapedotomy by implantation of a gold and a Teflon piston

Evaluation of hearing results after implantation of a Teflon piston (type Causse; Xomed Surgical Products, Jacksonville, FL) and of a pure gold piston (K-piston; Heinz Kurz GmbH Medizintechnik, Dusslingen, Germany), both with a shaft diameter of 0.4 mm in cases of otosclerosis requiring stapedotomy. An important difference between both prostheses is the difference in mass: the gold piston is three times heavier than the Teflon piston. Retrospective analyses were carried out of the presurgery and postsurgery audiologic results obtained after primary stapedotomy by implantation of 62 Teflon pistons and 66 gold pistons. The results were compared according to mean values of several audiometric parameters. Furthermore, individual audiometric results have been evaluated with the "Amsterdam Hearing Evaluation Plots" (AHEPs) as a method for visual presentation of hearing results from each operated ear. With this method, "unsuccessfully" and "successfully" inserted prostheses can be recognized easily and a more realistic comparison between prostheses is possible. It was found that in the overall group the heavier gold prosthesis gives a significantly larger gain in air-conductive hearing at 2 kHz (p < 0.05) and in the speech frequency range 0.5 to 2 kHz (p < 0.05). There were no significant intergroup differences with regard to change in bone-conduction and air-bone gaps. Analysis of the hearing results of the subgroup that included only the "successfully" implanted prostheses according to the criteria of the AHEPs had mainly consequences for improvement of air-conduction thresholds: none of the intergroup differences were statistically significant. For a fair comparison between prostheses, it is necessary to take only the prostheses into account that are inserted properly and that are functioning under normal conditions with regard to transmission of sound vibrations. After analysis of the hearing results of these "successfully" implanted prostheses, a trend was noticed that the heavier gold piston gives more gain in the low- and mid-frequency range and the light-weighted Teflon piston gives more gain in the high-frequency range, although none of the differences were significant.