[Experimental joint incus-stapedial injuries in scanning electron microscopy]

Abstract

Because all machines and vibration devices also produce noise, the combined activities of both factors are usually examined together. The opinion dominates that vibration exerts only a weak, additionally traumatic influence on the hearing organ. The aim of our investigation was to determine the influence of long-term, whole-body vibration on the incudo-stapedial joint which integrity is indispensable for the protection of the inner ear from the effect of noise. To realize the experimental conditions, sinusoidal vertical shaking (10 Hz, 5 mm, 1.4 g rms), an own noiseless apparatus was consisted. The experiment was carried out on 30 young, healthy, colored guinea pigs. They were subjected to vibration over 1, 3, and 6 months (132, 396, and 792 hours). The investigation was based on examination of the structures of the incudo-stapedial joint in the scanning electron microscopy. Among experimental animals two kinds of changes were ascertained which can be attributed to the activity of vibration. One was an extensive damage to the surfaces of the incudo-stapedial joint itself. The other was an often observed thickening of the bursa of the joint. The frequencies of occurrence and stages of advancement of both were in direct relationship to the duration of the experiment. The evaluation of the observed changes permits an explanation of the mechanism of the damage to hearing of persons subjected to noise and vibration. Whole-body vibration damages the incudo-stapedial joint, making its separation difficult. This may, than, facilitate the transfer of noise and its injurious influence to the inner ear.