Replacement of the femoral head by ceramic endoprosthesis. An experimental study on rabbits

In 31 rabbits the femoral head was replaced by a ceramic endoprosthesis. For 11 of the experimental animals the endoprostheses were made by the Arabia China Factory in Helsinki, and for 20 by Staatliche Porzellan Manufaktur in Berlin. The operation was performed under fully sterile conditions and the follow-up time was between 6 and 34 weeks. The hip joint was examined clinically, roentgenologically, macroscopically and histologically. The bending tolerance of the ceramic endoprosthesis was not adequate. Mechanical loosening of the proximal part of the prosthesis occurred in 68 per cent and was combined with fracture of the prosthetic stem. This created a pseudarthrosis-like reaction in the acetabular area and limited the movement of the hip joint. The distal fragment of the stem was always surrounded by a thin layer of dense bone. In the nonfractured cases (32 per cent), however, the reaction was only moderate and the movement of the hip joint was well preserved. The tissue reactions to the ceramic material were slight, but the great number of secondary reactions following stem fractures make the use of the ceramic endoprosthesis questionable in experiments with rabbits.