Three-dimensional investigation of the postoperative condition after ossiculoplasty with hydroxylapatite corp. (Running title; 3-D investigation of Corp).

From January 1985 to December 1993, at Oita Medical University, we have employed hydroxylapatite ceramic ossicular replacement prosthesis (Corp) for 42 ossiculoplasties for chronic otitis media with and without cholesteatoma and investigated the relationship between 3-dimensional condition of the prosthesis and hearing improvement after surgery according to the method of 3-D reconstruction technique as previously reported. The images of the middle ear and inner ear structures were traced on 4 or 6 tomograms of 2 mm thick slices from frontal view and input into the Nexus 6800 image processor. The 3-D images were reconstructed by using a 3-D reconstruction microsoft, TRI. The postoperative hearing improvement in ossiculoplasty with Corp was achieved in 23 (55%) of 42 ears. In 28 (67%) of 42 ears, Corp was found to be in the proper position on tomograms and to tilt upwards in 10 years (24%) and downwards in 3 ears (7%). In one case, the prosthesis was rejected through the tympanic membrane 23 days after surgery because the head of Corp was not covered with cartilage plate. In 19 (67%) of 28 ears, satisfactory hearing improvement was achieved, and Corp was well fitted to the tympanic membrane out of touch with other surrounding structures and vertical to the tympanic membrane, 3-dimensionally. In contrast, in 9 ears (33%) without improved hearing, the prosthesis was fixed in the proper position on the frontal plain, but it sifted backwards or forwards in 3-D reconstructed images.(ABSTRACT TRUNCATED AT 250 WORDS)