By: Michelle Rizzo for Medtech1
Recent findings suggest that microscopic titanium particles weaken the bonding of hip, knee, and other joint replacements. While titanium implants are safe in large blocks, wear and tear can produce micrometer-sized particles at the microscopic level.
Total joint replacement is a widely accepted treatment for many destructive joint diseases, including osteoarthritis, rheumatoid arthritis, osteonecrosis and severe pathologic fractures. Most joint replacements use a polyethylene for the bearing surface and either a titanium alloy or a chrome-cobalt alloy for the rest of the joint.
Researchers at the University of California, San Diego School of Medicine and the Jacobs School of Engineering measured the effects of titanium particles on the bonding strength of pins implanted in rat thighs. The findings, published in the Proceedings of the National Academy of Sciences, demonstrated that when the titanium particles were present, the pins came out more easily. The greatest weakening was associated with the smallest and largest particles.
The investigators showed how bone-building cells called osteoblasts and bone-destroying cells called osteoclasts are affected by different-sized titanium particles. With small- and medium-sized titanium particles concentrated inside cells, osteoblasts did not form proper adhesions. Osteoblasts increased the production of a protein called RANKL, which recruited and activated osteoclasts at the sites when the pins were inserted. This further weakened the bone.
“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,” said the study’s senior author K.L. Paul Sung, Ph.D., professor of orthopedic surgery and adjunct professor of cellular bioengineering.
Currently, Sung is leading a team in using nano-technology to improve implant material which has three to five times higher wear resistance and fatigue properties to reduce particle generation from implants.