Stapes prosthesis: Stainless steel vs. teflon

Abstract Bilateral stapedectomies were performed in 46 patients with a Robinson stainless steel stapes prosthesis and vein graft in the first ear, and a Robinson Teflon stapes prosthesis with vein graft in the second ear. The same patient was used for both types of prosthesis in order to equate variables as much as possible. Each patient had the same bilateral preoperative bone conduction level, the same surgical technique and the same footplate pathology. This resulted in the only difference being the prosthesis, itself, stainless steel in the first ear and Teflon in the second ear. The design of the prostheses was exactly the same, reducing the only variable factor to the weight of the two prostheses. The stainless steel prostheses weighed 12.5 mg. and the Teflon prostheses weighed 3.3 mg. The following factors were used in evaluating the results: 1. the preoperative bone conduction classification; 2. the type of footplate surgery and amount of footplate removal; 3. the postoperative pure tone audiometric results in the speech range, low frequency range, and high frequency range; and 4. acoustic impedance measurements to provide a relative comparison of the compliance of stainless steel, Teflon, wire‐fat and otosclerotic stapes. The audiometric studies revealed that the air‐bone gap closure to within 10 db was essentially the same in the stainless steel ears and in the Teflon ears (97 percent); however, 80 percent of the stainless steel ears had complete closure or overclosure of the air‐bone gap, whereas only 52 percent of the Teflon ears obtained complete closure or overclosure. Overall average gain in the stainless steel ear was 42 db compared to a net operative gain of 36 db for the Teflon ear. In the low frequency range there was a net gain in the stainless steel ear of 43 db and a net gain in the Teflon ears of 30 db. Similarly the high frequency gains were slightly better for the stainless steel (14 db) compared to the Teflon (11 db). Because the rate of complete and overclosure were significantly greater in one method than another, this paper illustrates that closure of the airbone gap to 10 db as the criteria of success is no longer adequate and more critical analysis such as the complete closure and overclosure rate, should be utilized in comparing the relative merits of one technique or prosthesis to another. Previous studies on stapedial loading by Bluestone, and by Cottle and Tonndorf are reviewed and correlated with the findings in this study. The impedance studies, measuring the median compliance and resistance suggest that the stainless steel prosthesis most resembles the normal mobile stapes while the Teflon shows a higher than normal impedance and the wire‐fat a considerably lower than normal impedance, corresponding closely with a previous study by Feldman. Although changing the weight of the prosthesis in stapedectomy surgery may have only a very small effect on the final hearing result, if it contributes to a 6 db gain over other prostheses it can be an influential factor in determining the type of prosthesis to be used in patients with mixed hearing losses, where such a gain will be critical in changing the result from a non‐serviceable hearing level to a serviceable hearing level. This may be even more beneficial when this gain is added binaurally.