[The influence of tympanoplasty on bone conduction (author's transl)]

Seldom tympanoplasty damages the inner ear in a substantial amount: From 1814 operations upon chronic inflamed ears 4 patients (0.22%) became deaf, among the other patients bone conduction (b.c.) in the mean increased at 1000 cps for + 0.8 dB and decreased at 4000 cps for - 2.2 dB. In 9.8% b.c. showed an improvement for 10 dB or more at 1000 and 4000 cps, 9.7% showed an corresponding deterioration. For patients it was confirmed on a statistical base, that the influence on bone conduction demonstrated by animal experiments (Tonndorf), was mainly the result of changing the compliance of oval window and of increasing ossicular inertia. By relieving a mobile stapes of an incus which was fixed in the attic, there results an improvement of mobility of the stapedial footplate with increasing b.c. at 1000 and 4000 cps. By interposition of an incus between tympanic membrane and stapes and by myringoplasty with fascia there results an increasing ossicular inertia with increasing b.c. at 1000 cps and decreasing b.c. at 4000 cps. Noise trauma, mechanical trauma and infection are only of slight importance, only in some single cases they will damage the inner ear in a substantial amount.