Poststapedectomy hearing gain: comparison of a Teflon (fluoroplastic ASTM F 754) prosthesis with a Schuknecht-typewire/Teflon prosthesis.

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.

Results

Of the 436 cases we reviewed, 146 met our inclusion criteria. These cases involved 76 patients who had received a Teflon prosthesis (study group) and 70 who had received a wire/Teflon prosthesis (control group). The two groups were paired according to age, sex, and the degree of hearing loss; there were no statistically significant differences between the groups in these variables (table 1).

Analysis of postsurgical hearing gain in both groups revealed a statistically significant difference (p < 0.04) in favor of the study group at the low frequencies (table 2). However, no statistically significant differences were seen at the medium and high frequencies.

Similarly, when analyzing the air-bone gap by frequencies, we found statistically significant differences in favor of the study group at 250, 500, 1,000, 2,000, and 4,000 Hz (p < 0.001) (table 3). The overall difference was also statistically significant (p < 0.001).

The differences between the two groups with respect to air-bone gaps at the low (table 4) and high (table 5) frequencies were also statistically significant (p < 0.001) in favor of the study group.

Discussion

For more than 40 years, stapedectomy has been an effective method of treating hearing loss secondary to otosclerosis. New prostheses have been developed for the purpose of improving hearing gain at a lower cost.

During the period of our study, we observed that an important determinant of hearing improvement was the stability of the prosthesis. Because the Teflon prosthesis has the ability to close itself(memory), it should be opened only as needed, depending on the width of the incus's long arm. This characteristic allows surgeons to safely place a Teflon prosthesis and fix it to the incus, thereby ensuring good stability in the oval window. With the wire/Teflon prosthesis, it has been clearly shown in the literature that manually closing the metal ring on the long arm of the incus can lead to unwanted tightness and necrosis at the fixation site. On the other hand, the ring may not close at all, which can lead to displacement of the prosthesis. Wire accounts for two-thirds of the components of the wire/Teflon prosthesis, and wire is subject to bending and displacement.

Placement of the Teflon prosthesis resulted in a significantly greater hearing gain at low frequencies and in significantly better air-bone gap closure at all frequencies in our study group. At the low frequencies, the air-bone gap was closed to within 0 to 10 dB in 71 of the 76 Teflon patients (93.4%), compared with only 40 of the 70 wire/Teflon patients (57.1%). At the high frequencies, the corresponding figures were 74 of 76 (97.4%) and 56 of 70 (80.0%). We believe that the hearing improvement seen in the study group is excellent. Although we are not certain why placement of the Teflon prosthesis results in greater postsurgical hearing gain and air-bone gap closure, we suspect the reason has to do with its ability to self-close and therefore remain stable.

Emilia Guadalupe Zepeda-Lopez, MS; Antonio Bello-Mora, MS; Manuel Martin Fe1ix-Trujillo, MS, MD

Reprint requests: Dr. Emilia Guadalupe Zepeda-Lopez, Nicolas San Juan 519-13, Col del Valle Delegacion Benito Juarez, C.P. 03020 Mexico D.F. Phone: [phone]; fax: [phone]; e-mail: [e-mail]

References

(1.) Shea JJ. Thirty years of stapes surgery. J Laryngol Otol 1988;102: 14-19.

(2.) Shea JJ Jr. Fenestration of the oval window. Ann Otol Rhinol Laryngol 1958;67:932-51.

(3.) Causse JB, Causse JR, Parahy C. Stapedotomy technique and results. Am J Otol 1985;6:68-71.

(4.) Schuknecht HF, Oleksiuk S. The metal prosthesis for stapes ankylosis. Arch Otolaryngol 1960;71:287-95.

(5.) Sooy FA, Owens E, Neufeld ES. Comparison of wire-vein and wire-gelfoam prostheses in stapedectomy for otosclerosis. Ann Otol Rhinol Laryngol 1973;82:149-52.

(6.) el-Seifi A. The necrosed incus in stapedectomy revision. Laryngoscope 1996;106:511-12.

(7.) Han WW, Incesulu A, McKenna MJ, et al. Revision stapedectomy: Intraoperative findings, results, and review of the literature. Laryngoscope 1997;107:1185-92.

(8.) Hammerschlag PE, Fishman A, Scheer AA. A review of 308 cases of revision stapedectomy. Laryngoscope 1998; 108:1794-1800.

(9.) Krieger LW, Lippy WH, Schuring AG, Rizer FM. Revision stapedectomy for incus erosion: Long-term hearing. Otolaryngol Head Neck Surg 1998;119:370-3.

(10.) Perkins R, Curto FS Jr. Laser stapedotomy: A comparative study of prostheses and seals. Laryngoscope 1992; 102:1321-7.

(11.) Persson P, Harder H, Magnuson B. Hearing results in otosclerosis surgery after partial stapedectomy, total stapedectomy and stapedotomy. Acta Otolaryngol 1997;117:94-9.

From the Otorhinolaryngology--Head and Neck Surgery Service, Dr. Gaudencio Gonzalez Garza General Hospital, La Raza National Medical Center, Mexico City.

Table 1. Selected characteristics of the two groups

                             Wire/
                Teflon       Teflon
                group        group
               (n = 76)     (n = 70)     p Value

Sex (n [%])                               0.4 *
  Women       51 (67.1)    49 (70.0)
  Men         25 (32.9)    21 (30.0)

Mean age         33.8         32.9         0.5
              [+ or -]     [+ or -]     ([dagger])
                 8.9          7.6

Median            61           63          0.3
hearing       (29 to 86)   (45 to 82)    ([double
loss in                                  dagger])
dB (range)

                  OR         95% CI

Sex (n [%])      1.46      0.6 to 3.3
  Women
  Men

Mean age                      -2.3
                              to
                              4.2

Median                        0.23
hearing                       to
loss in                       0.24
dB (range)

* Chi-square test.

([dagger]) Student's t test for independent samples.

([double dagger]) Mann-Whitney U test.

Key. OR = odds ratio; CI = confidence interval.

Table 2. Airway average by frequency

                               Median dB (range)

                               Teflon group

Frequency          Preop                Postop
(Hz)

Low         56.6 (43.3 to 70.0)   21.6 (10.0 to 36.6)
Median      51.6 (35.0 to 66.6)   20.0 (7.0 to 38.3)
High        43.3 (17.0 to 53.0)   26.6 (8.3 to 53.3)

                               Median dB (range)

                               Wire/Teflon group

Frequency          Preop                Postop
(Hz)

Low         58.3 (38.3 to 66.6)   23.3 (5.0 to 43.3)
Median      51.6 (36.6 to 65.0)   20.0 (10.0 to 43.2)
High        43.3 (30.0 to 65.0)   28.3 (3.0 to 58.3)

Teflon group Wire/Teflon group

Frequency        p Value *
(Hz)

Low                0.04
Median             0.15
High               0.34

* Mann- Whitnev U test.

Table 3. Air-bone gap by frequency

                                  Median dB (range)
                                  Teflon group

Frequency (Hz)         Preop            Postop

250                40 (25 to 60)     5 (0 to 25)
500                35 (15 to 60)     0 (0 to 30)
1,000              30 (10 to 55)     0 (0 to 15)
2,000              10 (0 to 40)      0 (0 to 15)
4,000              20 (0 to 45)      0 (0 to 30)
Overall           27.5 (17 to 53)    3 (0 to 13)

                                  Median dB (range)
                                  Wire/Teflon group

Frequency (Hz)         Preop            Postop

250                45 (20 to 60)     15 (0 to 30)
500                40 (20 to 55)     5 (0 to 35)
1,000              35 (10 to 50)     0 (0 to 25)
2,000              25 (0 to 25)      0 (0 to 30)
4,000              25 (0 to 55)      10 (0 to 60)
Overall            33 (17 to 48)     7 (0 to 21)

Frequency (Hz)       p Value*

250                    0.001
500                    0.001
1,000                  0.001
2,000                  0.001
4,000                  0.001
Overall                0.001

* Mann-Whitney U test.

Table 4. Closure of the air-bone gap at the
low frequencies (250 and 500 Hz)
postoperatively

             Teflon     Wire/Teflon
              group        group
            (n = 76)     (n = 70)

Intensity
(dB)          n (%)        n (%)      p Value *

0           28 (36.8)    11 (15.7)      0.001
1 to 5      25 (32.9)    14 (20.0)      0.001
6 to 10     18 (23.7)    15 (21.4)      0.001
1 1 to 15    2 (2.6)     15 (21.4)      0.001
16 to 20     2 (2.6)     9 (12.9)       0.001
21 to 25     1 (1.3)      6 (8.6)       0.001

* Mann-Whinier U test.

Table 5. Closure of the air-bone gap at the high frequencies
(1,000, 2,000, and 4,000 Hz) postoperatively

                  Teflon     Wire/Teflon
                   group        group
                 (n = 76)     (n = 70)

Intensity (dB)     n (%)       n (a/o)     p Value *

0                36 (47.4)    12 (17.1)      0.001
1 to 5           24 (31.6)    27 (38.6)      0.001
6 to 10          14 (18.4)    17 (24.3)      0.001
11 to 15          2 (2.6)     11 (15.7)      0.001
16 to 20           0 (0)       1 (1.4)       0.001
21 to 25           0 (0)       2 (2.9)       0.001

* Mann-Whitney U less.