Sửa chữa một khiếm khuyết màng tympanic sử dụng các nguyên tắc cơ bản của mô ghép. Kỹ thuật ưa thích là phương pháp miếng cẩn ngoài trung gian vì nhiều lý do. Đầu tiên, đặt mảnh ghép trên bề mặt trung gian còn lại màng tympanic, ngăn chặn một bên | 18 Chapter 2 Principles of Tympanoplasty I Ossiculoplasty 2 Repair of a tympanic membrane defect utilizes basic principles of tissue grafting. The technique favored is the medial onlay method for several reasons. The first placing the graft on the medial surface of the tympanic membrane remnant prevents lateralization Fig. . Second healing is more rapid since the squamous epithelial covering of the tympanic membrane is not sacrificed as it is with lateral on lay grafts. Third in order to prepare the medial surface of the tympanic membrane for receiving the graft it is necessary to remove epithelium from the medial surface of the drum which may include occult squamous epithelium that has migrated around the edge of the tympanic membrane defect Fig. . Although lateral onlay grafting is attractive technically it carries a risk of lateralization blunting of the anterior sulcus angle and may bury squamous epithelium on the medial surface of the drum remnant. The medial onlay graft is stabilized by pulling a tag of graft through a buttonhole incision in the tympanic membrane remnant anteriorly and sandwiched under the fibrous annulus of the canal skin flap and the bony canal wall posteriorly Fig. . This method of graft security avoids the use of absorbable synthetic material Gelfoam in the middle ear o Fig. Schematically type I and II tympanoplasty rely on an intact a or partially deficient b ossicular chain which retains the areal and lever mechanisms of the middle ear Repair of the Sound-Conduction Mechanism 19 space which may give rise to a granuloma posing a threat to cochlear function through the round window membrane. Finally firm packing to compress the graft onto its recipient bed prevents blood products from causing graft separation. Repair of the sound-conduction mechanism which transmits energy of the sound pressure wave to the cochlea where movement of the basilar membrane activates the neural response must follow one of two principal .
