[Obliteration of the mastoid cavity with porous tricalcium phosphate ceramic. Results 12 and 18 months after ceramic implantation in the hypotympanon of the pig].

The paper reports on the obliteration of mastoid cavities with resorbable tricalcium phosphate ceramic. As a model, we chose the pneumatic air cell system of the pig's hypotympanon, which resembles the human mastoid. At the time of surgery, the specimens were 10-12 weeks old. In a first group the cells of the hypotympanon were totally removed and the operation cavity was obliterated with adjacent layers of porous tricalcium phosphate ceramic. In a second group of specimens the air cell system was partly removed, leaving the apical part of the hypotympanon intact; the operation cavity was obliterated again with porous tricalcium phosphate ceramic. After 12 and 18 months survival the hypotympanons were removed and prepared for histological investigations. Those ceramic plates, lying close to the bony shell were strongly resolved and replaced by new bone. Other ceramic plates, however, especially those in the center of the implant, showed few signs of resorption and bony remodelling. Inside the ceramic implant there was hardly connective tissue. The space between the still unsolved ceramic plates was filled up with new bony tissue. This bone was partly structured and adjoined directly to the ceramic. The ceramic was integrated into the new bony tissue without any sign of an inflammation.