Five years experience with ceramic-metal-composite hip endoprostheses. II. Mechanical evaluations and improvements.

The results of the complete and detailed clinical evaluation are compared with the original design criteria. It is shown that most of them stood the test. Those aspects which did not meet the expectations are discussed in detail: The occurrence of very little and biologically tolerable wear during the initial running-in period will be further reduced by a considerable improvement of the material properties. The few cases of severe wear had been associated with clinically exceptional situations, the analysis of which allows for suggestions to avoid such situations. The material improvements and all other steps taken to increase the safety margin considerably against fractures of the ceramic ball are described in detail. In addition, the attention is paid to some necessary clinical precautions.