Zum Übertritt von Korrosionsprodukten aus Stahlimplantaten in das Kontaktgewebe. Untersuchungen der Implantatoberfläche mit ESCA und instrumentelle Neutronenaktivierungsanalyse des Kontaktgewebes

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Abstract
The long-term behavior of corrosion products of steel implants was investigated by animal experiments. Rabbits (30) were subject to an osteosynthesis of their left hind legs. The bone fragments of each were fixed by a V4A steel plate and 3-4 screws. One year after the implantation the rabbits were sacrificed and samples of the tissues and of the implants were analyzed. By electron spectroscopy for chemical analysis (ESCA), information was obtained on thickness, composition and valence state of the components of the alloy in the outer surface layer. Steel implants were covered by an easily destroyable oxide layer of 3-5 nm only, parts of which were Cr, Fe and Mo. Ni was not found. This passive layer was rather strongly enriched in Cr. An increased content of Cr was also revealed in the deeper metal layer next to the passive one. The mechanism leading to the formation of the passive layer is discussed. Provided that the passive layers of the implants are intact, the contents of the alloy deposited in the adjacent tissue are expected to correspond to the composition of the alloy. The concentrations of the corrosion products in the tissues can be changed by biological regulatory processes. Contact tissues and the surrounding muscles were investigated for Cr, Fe, Co, Ni, Mo and W, which are contained in the steel, and for the partially essential trace elements K, Zn, Se, Br and Rb by instrumental neutron activation analysis. The samples of contact tissue were strongly enriched in content of alloy-specific elements. Concentrations higher than the normal values for Ni, Cr, Co and Mo were observed at constant ratios. Fe behavior is an exception to this rule, indicating the existence of a regulation mechanism. Some other trace elements not contained in the steel show an anomalous behavior. K, Zn, Se and Rb in contact tissue are decreased compared to the surrounding tissues, while Br in contact tissue is enriched 2 times. An overburden of tissue with corrosion products of stainless steel enriches the alloy-specific elements and disturbs the balance of trace elements in the body.

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