[Are porous tricalcium phosphate ceramics suited for the replacement of bony walls in ear surgery? An animal experiment study of the hypotympanum of the domestic swine].

The purpose of this study was to examine the possibility of a partially or totally posterior canal and lateral attic wall reconstruction with a more stable and therefore less porous tricalcium phosphate ceramic plate (S8). The hypotympanon of 4 pigs was drilled out, leaving the bony shell intact. In the middle part of this cavity a 2 mm thick S8-ceramic plate was placed horizontally. The hypotympanon of further 11 pigs was drilled out and obliterated with a more porous tricalcium phosphate ceramic (S5). Additionally, a single S8 ceramic plate served as a wall to the cavum tympani. 1 to 18 months after operation the pigs were sacrificed; sections of the hypotympanon were investigated with light microscopy. After few weeks, the S8-ceramic plate was covered by granulation tissue and epithelium on the tympanic side. After three months newly formed bony tissue could be observed between the peripheral parts of the S8-ceramic plate and the tympanic epithelium. After six months both sides of the S8-ceramic plate were completely covered by new bone; moreover this bone is covered by the mucosa on the tympanic side. At this time the S8-ceramic plate has a tight bony contact to the shell of the hypotympanon and bone growth can be observed in the macropores of this plate. The bony layer on the tympanic side of the S8-ceramic plate remained slim, there was no exophytic growth after 12 months. After 18 months the S8-ceramic plate shows distinct signs of resorption and bony replacement. However, in comparison to the S5-ceramic this occurs slower and later.