Osteoclastic activity is seen in areas of bone resorption which are the result of experimental and human cholesteatoma. Many factors may induce osteoclasts, including transmitted pressure. The purpose of this study was to determine if transmitted pressure, in the absence of cholesteatoma, could cause localized bone resorption in the middle ear. Surgical grade silicone was implanted into the middle ear of gerbils without cholesteatoma. Bone resorption was observed only in areas where the implants exerted pressure on bone. It was estimated that pressures of 50 to 120 mm Hg (6.7 X 10(4) to 16 X 10(4) dynes/cm2) resulted in the induction of osteoclastic bone resorption.
Surgical ligation of the external auditory canals of Mongolian gerbils produces aural cholesteatomas that are similar to spontaneous gerbilline cholesteatomas. These experimental cholesteatomas expand rapidly, medially displacing the tympanic membrane and eroding bone. Less than 2 months after ligation, half these cholesteatomas are in contact with the bony prominence of the cochlea. Ligation-induced formation of cholesteatomas may be unique to the gerbil. Keratin deposits are produced by similar ligations of the external auditory canals of cats, guinea pigs, hamsters, mice, and rats. However, in these animals there is no medial displacement of the tympanic membrane, no cholesteatoma formation, and no bone erosion. Cholesteatomas were not seen in cats, guinea pigs, hamsters, mice, and rats even after post-ligation intervals of 6 to 36 months.
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