[Fracture load of ceramic ball heads of hip joint prostheses]. / Bruchlast keramischer Kugelköpfe von Hüftgelenkprothesen.

To ensure the stability of ceramic ball heads of hip joint prostheses over the long term, both standards for the material and FDA-regulations for the components have been established. In this paper the philosophy underlying design and reliability is discussed. On the basis of fracture loads determined for Biolox ball heads the high level of stability and reliability that has been achieved and can now be guaranteed, is demonstrated.

[The cause of loosening in cemented hip joint prostheses. Light and electron microscopy study and laser microprobe mass analysis]. / Untersuchungen über die Lockerungsursache bei zementierten Hüftgelenkendoprothesen. Licht- und elektronenmikroskopische Untersuchung und Laser-Mikrosonden-Massenanalyse.

Aseptic loosening of joint prostheses is a quantitatively increasing problem. For evaluation of the pathogenesis of prosthesis loosening joint capsules and tissue membranes taken from the femoral and acetabular bone-cement-interface of 23 hips revised for aseptic loosening were examined. In all cases we found an excessive inflammatory histiocytic reaction with intracytoplasmatic incorporation of a small granular foreign material. This could be identified to be zirconium oxide by LAMMA-analysis. Zirconium oxide and polymethylmethacrylate (PMMA) wear particles could be shown in the cytoplasm of histiocytes by transmission electron microscopy. By quantitative grading of the histiocytic reaction and the intracellular granular wear particles we found that both were evenly distributed around the loosened prosthesis. Chronic inflammation due to bone cement abrasion is regarded as a leading cause of aseptic prosthesis loosening.

[Hydroxyapatite ceramic coatings for anchoring components of hip joint prostheses (technical aspects)]. / Hydroxylapatitkeramik-Beschichtungen für Verankerungsteile von Hüftgelenkprothesen (technische Aspekte).

Following the positive clinical results obtained with pure hydroxyapatite ceramic in the form of granules, the development of coatings of this material for anchoring components of artificial joints was initiated 6 years ago with the aim of improving implant bone bonding. Among the various coating procedures available, the plasma spraying process alone would appear capable of producing coatings which meet the requirements of a bioactive and osteotropic layer between bone and implant, in particular with respect to coating thickness and bond strength. However, the plasma spraying process at first seemed to be out of the question because of the high process temperature involved. After studying the factors affecting the transformation mechanism, it proved possible to suppress the phase transformation by a suitable preparation of the hydroxyapatite ceramic powder, and a combination of particular process parameters. The coating process and the quality checks are described in detail, and the properties of the coating compared with the requirements it has to fulfill.

[Assorted aluminium-oxide ceramic heads for prostheses of the hip-joint. A preliminary communication (author's transl)]. / Aluminiumoxidkeramikkugeln für Hüftendoprothesen nach Baukastenprinzip. Vorläufige Mitteilung.

In the search for even more hard-wearing prostheses of the hip, a rotating total- and femoral head prosthesis and a total- and femoral head prosthesis with fixed detachable heads are described, the head of which is made from highly polished aluminium oxide ceramic, Biolox. For total prostheses the excellent gliding features between ceramic head and polyethylen acetabulum are being used. They will also permit return to proved metal-polyethylen prostheses, should the ceramic head fracture. The fracture prosthesis provides both such an exchange and conversion into a total prosthesis. Extending the present programme of rotation-prostheses to ceramic heads will require a wide assortment of heads. This will mean not only wide adaptability but also the need for detailed knowledge of this assortment, the use of which demand thorough preparation of the surgeon. In order to collect material of the use of these prostheses, the authors are very keen to hear of drawbacks- and without reticence-as soon as possible. Publication of our own experience will follow this preliminary communication in due course.

[Studies on non-metal materials in oral surgery]. / Untersuchungen mit nichtmetallischen Werkstoffen in der Zahn-, Mund- und Kieferchirurgie

Two non-metallic implant materials are introduced and the indications for their use are described. A maxillo-facial indication exists in the reconstruction of the temporo-mandibular joint and the orbital floor. We find dental-surgical indications for the Aluminium-Oxide ceramics as well as for implants in the replacement of single tooth gaps and unilateral as well as bilateral shortened dental rows. The indication in the toothless jaw is the most unfavourable and should be restricted to replacement of both canine teeth.

Animal studies on bone ingrowth kinetics of ceramic material under dynamic stress.

Two of the primary problems of implants in use today result from the materials used in their construction (metal and polyethylene) and from the necessary additional fixation with bone cement. In order to alleviate these well known difficulties, we studied ceramic material (99.7% Al2O3 with 0.25% MgO) which exhibits several advantages in these areas, but has a diminished bending strength. To take advantage of the ceramic material, we tested a cement-free implantation which should allow unhindered growth of bone tissue to or into the material. In particular, the interface relationship under load bearing was investigated. The course of the tissue differentiation and ingrowth on the surface of the ceramic implants under dynamic stress, was studied by a specifically disegned distance-spacer. These were tested on the femur of foxhounds and sheep, as well as by use of temporary immobilization. Histological investigations in intervals of 4 weeks showed the course of the development of the interface tissue. After removal of the binding materials, the behavior of the implant support is studied in 4-week intervals with free load bearing. Radiological and histological development studies are shown. The results we obtained implicate the use of ceremic impants. But the application in humans still seems to be problematic, as there is a need for designs which are loaded by pressure only.

[The properties required of bioceramics for artificial joints (author's transl)]. / Anforderungen an oxidkeramische Werkstoffe als Biomaterial für künstliche Gelenke

Tests of hip joint simulator proove the outstanding friction--and wear-behaviour of high density high purity allumina ceramics, being well known for many years from the field of engineering. According to a comparison of the characteristical physical properties of these special oxide ceramics with the requirements of materials for artificial joints, it is to be expected that wear components being made of high density alumina ceramics will show a very good behaviour in long time runs. This paper will also discuss the problems of body compatability breifly, which have been solved so far already.