Poststapedectomy hearing gain: comparison of a Teflon prosthesis with a Schuknecht-typewire/Teflon prosthesis

Ear, Nose & Throat Journal, Nov, 2005 by Emila Guadalupe Zepeda-Lopez, Antonio Bello-Mora, Manuel Martin Felix-Trujillo

Abstract

We conducted a retrospective study to compare poststapedectomy hearing gain in study-eligible patients who had received a Teflon (fluoroplastic ASTM F 754) prosthesis (study group; n = 76) with hearing gain achieved in a matched group (by age, sex, and degree of hypoacusis) of patients who had received a Schuknecht-type wire/Teflon prosthesis (control group; n = 70). All procedures had been performed by the authors at our institution between Jan. 2, 1994, and Dec. 31, 1997. Airway averages at low, medium, and high frequencies were estimated on the basis of pre- and postoperative audiologic evaluations, as were total air-bone gaps at 7 frequencies between 125 and 8,000 Hz. We found that the study group achieved a significantly greater degree of hearing gain at 125 and 250 Hz and significantly better closure of the air-bone gap at 250, 500, 1,000, 2,000, and 4,000 Hz. The hearing outcomes among patients in the study group were excellent.

Introduction

Otosclerosis, an osteodystrophy limited to the temporal bone (otic capsule), can cause a progressive conductive hearing loss (and occasionally a sensorineural hearing loss if the cochlea is involved). (1) The treatment of patients with otosclerosis and associated conductive hearing loss is stapedectomy. In 1956, Shea performed the first stapedectomy, which involved a complete removal of the stapes and closure of the oval window with a vein graft; hearing gain was achieved by placing a polyethylene strut to connect the incus to the vein graft. (2)

Since then, Shea's technique has been modified several times. (3) Shea abandoned the use of the polyethylene prosthesis because it had a tendency to slide toward the vestibule and erode the incus. In 1960, Schuknecht and Oleksiuk introduced a wire prosthesis. (4) A Gelfoam wire prosthesis was also used during the 1960s, but it too was abandoned after it became implicated in an increase in the incidence of sensorineural hearing loss and in the risk of postoperative perilymphatic fistulae.

The 1970s marked the beginning of the era of the metal-wire and Teflon (polytetrafluoroethylene) Schuknecht-type piston prosthesis of various diameters (0.4, 0.6, and 0.8 mm). The diameter of the most widely used wire/Teflon prosthesis is 0.6 mm. During surgery, the wire is fixed to the long arm of the incus and manually closed with a McGee forceps. (5,6) Improper closure of the wire was reported to cause erosion and necrosis of the incus arm in 43.2% of cases. (6-9) Perkins and Curto reported that the use of the wire/Teflon prosthesis resulted in a closure of the air-bone gap of 16.1, 7.9, 3.9, and 10.2 dB at 500, 1,000, 2,000, and 4,000 Hz, respectively. (10) Closure of the air-bone gap to within 10 dB has been reported in as many as 82.8% of patients. (10,11)

Since 1995, we have been using the fluoroplastic ASTM F 754 prosthesis, which is made completely of Teflon. To ensure correct placement intraoperatively, the prosthesis ring is opened with a set of cupped tweezers or a hooked instrument. The prosthesis remains open for several minutes, which allows for its proper placement before memory closes it.

In this article, we describe our comparison of the Teflon prosthesis with the wire/Teflon device in terms of postoperative hearing gain. To the best of our knowledge, no such study has heretofore been published in the world literature.

Patients and methods

We retrospectively reviewed the records pertaining to all stapedectomies that we performed between Jan. 2, 1994, and Dec. 31, 1997, at the Otorhinolaryngology-Head and Neck Surgery Service at Dr. Gaudencio Gonzalez Garza General Hospital, an otologic tertiary care center in Mexico City. In order to be eligible for this study, cases had to have involved (1) patients of either sex who were between 17 and 60 years of age, (2) clinically diagnosed and audiologically corroborated otosclerosis, (3) a 65-dB conductive hypoacusis with tone loss, and (4) stapedectomy with placement of either a Teflon prosthesis or a wire/Teflon prosthesis. The groups were paired by age, sex, and degree of hypoacusis. We excluded cases in which patients had had ossicular chain fixation secondary to tympanic sclerosis, malleus and incus problems, or congenital anomalies. All of the authors had used the same surgical technique to perform all stapedectomies. Local anesthesia was administered in every case.

Once all eligible charts had been selected, we reviewed them for each patient's age, sex, degree of hypoacusis, and type of prosthesis. We also reviewed audiologic data and noted airway averages at low frequencies (125,250, and 500 Hz), medium frequencies (500, 1,000, and 2,000 Hz) and high frequencies (2,000, 4,000, and 8,000 Hz). We also noted air-bone gaps at 0, 1 to 5, 6 to 10, 11 to 15, 16 to 20, and 21 to 25 dB at low (250 and 500 Hz) and high (1,000, 2,000, and 4,000 Hz) frequencies as recorded by a Madsen Midimate 602 audiometer (GN Otometrics; Taastrup, Denmark).

The statistical analysis was done with the assistance of SPSS 8.0 software (SPSS; Chicago). Frequency measures were used independently for each of the variables. For qualitative variables such as sex, the chi-square test was used. Based on the skewness and kurtosis values, we used the Mann-Whitney U test and the Student's t test to analyze group differences.