Studies on the measurement of the mechanical properties of the round window membrane

Abstract

With a microtesting system which can measure the mechanical properties of small tissue membranes, we have measured the mechanical properties of the round window membrane on the guinea pigs and the human. We also found that, as a result of formalin-fixation, round window membranes become weaker and that this effect of formalin-fixation is greater on human round window membranes than on those of guinea pigs. Since the protein in collagen fibers, which are the main constituent of round window membranes, is coagulated and fixed with formalin, we consider that the strength of the membranes decreases and that this is more evident in human membranes, which contain more collagen fiber. Having compared the mechanical properties of the fresh round window membranes of guinea pigs with those of humans, we found that the human membranes are approximately five times stronger than those of guinea pigs. This difference is considered to stem from the species differences. Also, having compared the mechanical properties of the tympanic membranes with those of the round window membranes each species, we found that the round window membranes of guinea pigs are almost the same as their tympanic membranes in terms of strength, whereas human tympanic membranes are stronger and harder than the round window membranes. In view of the minimum pressure causing destruction of human round window membranes, as deduced from the experiment on guinea pigs, it is possible that human round window membranes may be ruptured in the perilymphatic fistula.