Show Titanium Debris Sabotage Artificial Joints
By Sue Pondrom
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
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
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., UCSD professor of orthopedic
surgery and adjunct professor of cellular bioengineering.
The team measured how
titanium particles affected the bonding strength of pins implanted
in rat thighs. The pins were shown to come out more easily when
the titanium particles were present, with the smallest and largest
particles causing the greatest weakening. The researchers demonstrated
how different-sized titanium particles affected bone-building
cells called osteoblasts and bone-destroying cells called osteoclasts.
Microscopic studies revealed osteoblasts did not form proper
adhesions, with small- and medium-sized titanium particles concentrated
inside cells. Increased production of the protein RANKL by osteoblasts
recruited and activated osteoclasts at the insertion sites,
further weakening the bone. Larger titanium particles also activated
metalloproteinases, which chop up the extracellular matrix that
holds cells together.
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.
In addition to Sung,
additional authors were first author Moon G. Choi, M.D., UCSD
Department of Orthopedic Surgery; and Hae S. Koh, M.D., UCSD
Department of Orthopedic Surgery; Daniel Kluess, M.S. and Daniel
O'Connor, M.A., UCSD Department of Bioengineering; Anshu Mathur,
Ph.D., George Truskey, Ph.D., Department of Biomedical Engineering,
Duke University; Janet Rubin, M.D., Department of Medicine,
Emory University School of Medicine and Veterans Administration
Medical Center, Atlanta; and David X.F. Zhou, Ph.D., UCSD Department
The study was supported
by a Bristol Meyers/Zimmer Award for Excellence in Orthopaedic
Research and the National Institutes of Health.
Media Contact: Sue
Pondrom (619) 543-6163