[Development of the ceramic sandwich cup used for the hip joint prosthesis.]

The abrasion of the polyethylene seems to be the most important factor participating on the endoprosthesis loosening. From this reason, the ceramics (AI2O3) was introduced for the both parts of the prosthesis, i. e. the head and the cup. It appears that the friction resistance is an important factor for the comparison of the hitherto applied endoprosthesis designs with the new developed type. The frictional resistance in the hip joint total prosthesis was measured by means of a testing device which allowed a swinging motion of the ceramic ball in the tested cup in the range of +/-25 degrees . This measurement was carried out at the loading levels being 0; 500; 1000; 1500 and 2000 N. For the comparison of the frictional resistance of single measured couples "cup-head", the energy consumed was ascertained which was necessary for including a swinging motion over the time interval of 35 sec. Ceramic cups manufactured by a. s. DIAS Turnov were used for the measurement. Altogether eight couples "ceramics-ceramics" having the diameter differences ranging from 0,022 mm to 0,137 mm and one friction couple "polyethylene cup-ceramics ball" were measured. The research of influence of different lubricants was also done. Key words: sandwich cup, total prosthesis, ceramics--ceramics, bioceramics, frictional resistance.