Periprothetische Zementverteilung bei femoralen Oberflächenersatzprothesen im Vergleich: Kunstknochen versus humaner Ex-vivo-Knochen : Etablierung eines standardisierten In-vitro-Modells

Despite controversial discussions, the Metasual Durom Hip actually seems to be the most bone sparing procedure when implanting hip prostheses in the field of prosthesis. Despite advancements of the materials as well as the surgical procedures, there remains an element of risk of septic and aseptic loosening and particularly the risk of necroses with the distress of fracturing of the neck of the femur. These factors are mainly influenced by the periprosthetic allocation of bone cement. Because of missing radiation transparency the allocation of bone cement under the prosthesis postoperatively cannot be evaluated by common radiologic procedures. Therefore, uneven allocations of the cement, fractures of the cement coating and border loosening cannot be identified. For validation of the cement allocation under the prosthesis a pilotstudy was conducted particularly with regard to describe the macro- mechanical interdigitation of bone cement with spongy bone of anatomically specimen compared to artificial bone models.MATERIALS AND METHODS: Plastic models of polyoxymethylene accordant to the inside geometry of the Metasual Durom Hip Prostheses were implanted on ex-vivo-Femura (n=14) versus artificial bone models (SAWBONES) of three different spongy densities (0,16;0,20;0,32 g/cm³)(every n=8) in clinically standardized surgical procedure. Polyoxymethylene ist defined by the characteristics radiolucency and thermal consistency according to the cobalt-chrome-alloy of the Durom Hip. The resulting models were reproduced by highly resolving computed tomography. Afterwards the computer based analysis of the periprothetic bone allocation of the artificial bone models versus the anatomic specimen was accomplished.RESULTS: It could be shown that the sawbones of the lower spongy density (0,16 and 0,20 g/cm³) were similar to the ex vivo femura regarding the bone penetration of cement. No significant differences could be shown regarding interdigitation. Both groups of Sawbones can be used for further studies.OUTLOOK: The intention of a continuative project will be the comparison of the periprothetic cement allocation of the current prostheses (cemented and cemented press fit versions) after implantation at sawbones with the density of 0, 16 and 0, 20 g/cm³