Experimental animal model of intracochlear ossification in relation to cochlear implantation

Abstract

Histopathologic examinations of the temporal bones of implanted human patients and experimental animals have demonstrated various degrees of abnormal fibrous tissue or new bone formation within the cochlea; in some cases, extensive new bone formation was reported. The presence of new bone following cochlear implantation is undesirable, since it may adversely affect current distributions in the electrically stimulated cochlea. The pathogenesis of intracochlear osteoneogenesis as a direct result of cochlear implantation is unclear. The aim of this study is to use an experimental animal model to investigate some of the factors underlying the formation of new bone and fibrous tissue within the implanted cochlea, especially the role of insertion trauma and bone chips, and also a possible way of inhibiting such a process using an anticalcific agent of the diphosphonate family, disodium ethane-1-hydroxy-1, 1-diphosphonate(EHDP). The local release of EHDP from a polydimethylsiloxane (Silastic silicone rubber, Dow Corning Corp) controlled delivery system has been shown effective in the context of bioprosthetic heart valve. Its application within the cochlea has not been documented, to our knowledge.