This paper describes the design principles of a new endoprosthesis made of dense aluminum oxide (A12O3) and implanted without bone cement. Mechanical tests and animal experiments have proved the sufficient mechanical strength of the bone-prosthesis connection as well as the biocompatibility of the material. So far, 12 tumor patients selected according to strict indication criteria have been operated on. Both the clinical-radiologic and the first histological findings available are encouraging. Special reference is made to the first fully ceramic total hip joint endoprostheses implanted in a human without bone cement.
Various implants have been developed for the upper and lower extremities and the spine. In order to establish whether endoprostheses made of Al2O3 will show the same good biocompatibility in humans as it has in experiments with animals, endoprostheses implantations were performed in 4 patients: 2 upper arms, 1 radius, 1 vertebra body. The implants were exposed to various loads. The biomechanical conditions were considered in the construction. The results reveal that the knowledge of material properties and prior calculations make possible the development of satisfactory endoprostheses. X-ray examinations confirm these deductions. Good functionality was achieved in vivo with all implants. They were all mechanially anchored, no bone cement was used. Thus the biocompatibility of the material was not limited. A histological examination is made of one implant. The macroscopic examination showed a stable fit and no pathological reactions, X-rays revealed that the bone remained in good contact with the implant. The longest observation period was over 1 1/4 years. Present observations show that the use of Al2O3 implants, without the use of additional materials (bone cement), results in a tight fit of the implants.
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