MONDAY, March 7 (HealthDay News) -- Tiny particles released by the wear-and-tear of titanium joint implants can weaken the bonding of knee and hip replacements, researchers report.

In tests with rats, University of California, San Diego (UCSD) and Jacobs School of Engineering researchers concluded that titanium implants are safe in large blocks, but wear-and-tear can cause the implants to release micrometer-sized particles.

"As replacement joints are becoming increasingly common in aging populations, our results explain how such devices fail and suggest that improvements should be made in artificial joint design," senior author K.L. Paul Sung, UCSD professor of orthopedic surgery and adjunct professor of cellular bioengineering, said in a prepared statement.

The findings appear in this week's issue of the Proceedings of the National Academy of Sciences.

Sung and his colleagues calculated the effect of titanium particles on the bonding strength of pins implanted in rats' thighs. The researchers found that the pins came out more easily when there were titanium particles present. Both the smallest and largest-sized titanium particles resulted in the greatest weakening of the pins.

The titanium particles prevented osteoblasts -- bone-building cells -- from forming proper adhesions and also resulted in increased production of bone-destroying cells called osteoclasts.

Sung and his colleagues are currently using nanotechnology to improve joint implant material by increasing wear resistance and reducing particle generation.

More information

The American Academy of Orthopaedic Surgeons has more about joint replacement.