Relating nickel-induced tissue inflammation to nickel release in vivo

Nickel has a number of adverse biological effects that have made the use of nickel in biomedical implants controversial. Yet information about the dis tribution of nickel in tissues around nickel-containing implants is scarce. The purpose of the current study was to use a laser ablation technique, co mbined with inductively coupled mass spectroscopy, to assess the spatial di stribution of nickel around nickel-containing implants in vivo. Polyethylen e, pure nickel wire, or a nickel-containing alloy (Ni-Cr) were implanted su bcutaneously into rats for 7 days. The tissues were analyzed for Ni content and inflammation at 1-mm intervals up to 5 min away from the implants. The sham surgery sites and the polyethylene caused mild to moderate inflammati on 1-2 mm from the implant site with no detectable nickel in the tissue. Th e nickel wire caused severe inflammation up to 5 mm away from the implant s ite with necrosis for I nun around the implant. Nickel concentrations reach ed 48 mug/g near the implants, falling exponentially to undetectable levels at 3-4 nun from the implants. The Ni-Cr wire caused inflammation equivalen t to polyethylene, with less than 4 mug/g of nickel present in the tissue f or 1-2 nun around the implants. The current study showed that the laser-abl ation technique was well suited for the analysis of soft tissues for metal- ion content, and that the nickel distribution in tissues correlated well wi th overt tissue inflammation. (C) 2001 John Wiley & Sons, Inc.