07 March 2005 - University of California, San Diego Microscopic titanium particles weaken the bonding of hip, knee, and other joint replacements, according to research published online in Proceedings of the National Academy of Sciences by researchers at the University of California, San Diego (UCSD) School of Medicine and the Jacobs School of Engineering. The team demonstrated that titanium implants are safe in large blocks, but at the microscopic level, wear and tear can generate micrometer-sized particles.