Biological considerations for the use of homograft tympanic membranes and ossicles

This report deals with some biological aspects of transplantation and preservation of tympanic membrane and ossicular grafts. The structure and behaviour of tympanic membrane grafts depends largely on the reaction of the preservatives with the tissue proteins. Due to these properties no observable change in the microscopical structure of the membranes and ossicles was found up to 3 years after alcohol and formaldehyde preservation. Preservation in cialit showed gradual disappearance of nuclei and an increasing disintegration of the fibrous structures. Irrespective of the mode of preservation, the fibrous tissue appeared to persist virtually unaffected for long periods. The monocellular reaction found around the grafts preserved in formaldehyde after heterolopie transplantation suggests that tissue antigens are not completely destroyed. A reaction to transplantation in the middle ear is only found around fresh heterologous grafts and around the fresh homologous grafts after previous sensitisation. As observed in rats, ossicles preserved in alcohol or cialit, obtained from revision operations in humans showed partial remodelling. Moreover in some cases these ossicular and especially the cartilaginous grafts showed areas of frank erosion.