Titanium serum and urine levels in rabbits with a titanium implant in the absence of wear

Although devices made of titanium and its alloy with 6% aluminium and 4% vanadium have been remarkably successful primarily in orthopaedic and dental applications, clinical reports have implicated the biological response to released metal from this class of metals as a cause of failure. It is our hypothesis that in the absence of wear, the amount of titanium released is small and will preferentially accumulate in local tissues. One important implication of this is that measurable quantities of titanium in serum and urine that have been observed in clinical studies result from mechanically induced or assisted release phenomena. In order to test this hypothesis, titanium levels in various tissues and fluids of animals both with and without titanium implants need to be determined. In this paper, we report the titanium concentration in serum and urine of rabbits in the absence of wear. Titanium fibre felts were implanted into the tibia of rabbits. At various time points, serum and urine samples were collected from these rabbits as well as from two groups of control rabbits. The samples were analysed for titanium concentration using electrothermal atomic absorption spectrophotometry. The data for the implant group show that titanium levels in serum and urine do not increase in comparison to controls up to one year after implantation. Some clinical studies have documented elevated titanium serum and urine levels in the presence of titanium-based prostheses. The different results from these studies can be resolved by considering titanium release mechanisms other than passive dissolution.