臨床的耳硬化症の聴力所見と結合織によるアブミ骨置換術（Heermann法）の成績

AUDIOMETRIC FINDINGS IN CLINICAL OTOSCLEROSIS AND THE RESULTS OF STAPES REPLACEMENT BY CONNECTIVE TISSUES

　臨床的にアブミ骨固着が存在すると診断された場合，日本では欧米に比して耳硬化症が少ないのでいわゆる耳硬化症あるいは臨床的耳硬化症として報告されている^{9）12）22）39）40）}。大学病院での耳疾患患者総数に対するこのような耳硬化症の割合は0.25〜0.3％^{22）32）40）}であり，難聴患者総数の1.1％^12）といわれている。このように日本人では頻度の少ない疾患であるだけにアブミ骨固着の成因についての検討や検査所見についての報告は比較的少なく，とくに手術成績についての報告が少ないのは己むを得ない^{22）32）40）}。後者に関する初期の報告は内耳開窓術のものであり，アブミ骨切除術による成績についてまとめたものは少ない^22）32）。著者はミュンヘン大学耳鼻咽喉科留学中の経験や，欧米のクリニックでの手術見学，さらに日本人の本症に対する手術経験から，1）日本人では耳内操作が欧米人より容易でないこと，2）耳硬化症の頻度が少ないため手術例数が少ないこと，3）合併症の中に異物使用と関連するものが多い，などが気がかりであつた。

　以上の3点を考えれば諸外国で通常行なわれている方法とは違つた，より容易で，しかも安全な手技が必要ではないかと考えていた。偶々，ミュンヘン大学留学中，そこでfirst choiceの方法として行なわれていた方法にHeermann法があつた。この方法は後述するように，アブミ骨除去後に結合織のみを用いるアブミ骨置換術ともいうべきものであり，異物をまつたく使用せず，手技も容易で，しかも良好な成績が得られ，合併症も少ない。このようなことから日本人のアブミ骨切除術として適した手技と考えて5年来成績を検討してきたのでその結果を報告する。

Abstract 1. Twenty-four ears of fifteen cases with clini-cal otosclerosis in the Department of Otolaryngo-logy, School of Medicine, Keio University were evaluated for past five years.

2. Audiometric pattern of both air and bone conductions and air-bone gaps, and differences in air conduction threshold between both ears were investigated. One of the remarkable findings was that bone conduction threshould was elevat-ed in half of the all cases, and this findings is diagnostic of otosclerosis. Tympanometry shows As-type (type A with low compliance) in most cases and the value of static compliance is mo-stly within 0.31-0. 5cc.

3. In twenty-two ears among twenty-four ears stapedectomy was performed. Nineteen cases among them were operated on by Heermann's method under local anesthesia, in which fixed stapes was removed and replaced by a few pieces of connective tissues taken from behind the ear through an incision of one centimeter in length.

4. In 67% of the operated cases more than 15dB hearing improvement was obtained post-operatively with this method. In 67% air-bone gap decreased within 15dB. Also in 72% of the cases operated on recovery rate (postoperative air conduction gain /preoperative air-bone gap) was more than 51%.

5. Postoperative findings of impedance audio-metry revealed that the cases showing type A in tympanometry and showing static compliance value over 0. 51cc in increased in number. 6. Postoperative hearing became stable within three months both in conversational areas and in 4, 000 Hz in which hearing became temporalily worse immediately after the operation, but re-covered gradually thereafter.

7. Histologic findings of the footplate obtained showed no otosclerotic focus.

8. From these observations two different pathologies, otosclerosis and congenital footplate fixation, seemed to be included in the so-called clinical otosclerosis. Heermann's method is an easy and complication-free technique as far as the replacement materials are concerned, because no artificial prosthesis is used. Though their long-term results should be followed and re-evaluated, this method is thought to be applicable as a first choice stapedectomy procedure for clinical otosc-lerosis in the Japanese.