Trace element burdening of human tissues due to the corrosion of hip-joint prostheses made of cobalt-chromium alloys.

Using instrumental neutron activation analysis, the concentrations of 18 elements were studied in human articular capsule and fascia lata before and after application of total endoprostheses of the hip joint made of cobalt-chromium alloys. Tissues from the vicinity of the implant showed extreme burdening by corrosion products (Co, Cr, Ni), as well as by Zr, Hf, and Ba from the bone cements. Tissues more distant from the implants exhibited lower, but still significant burdening. Moreover, some essential trace elements not contained in the implant materials were changed in the tissues after implantation. In order to clarify the dissolution of alloy constituents in biological media, the passivation of cobalt-chromium alloy was investigated by tracer techniques using Ringer's solution as a simple model of the body fluids. The passivation process lasted for more than 1 month and was accompanied by a selective dissolution of the alloys constituents in the order Ni greater than Co approximately Fe greater than Mo greater than Cr. A comparison of the tissue analyses with the corrosion experiments demonstrates that the distribution patterns of the corrosion products in the tissues are influenced by both the corrosion process and the biochemical properties of the corrosion products.