A new study led by UC San Francisco researchers has found that acrylic bone cement, often used to attach total hip replacements to bone, degrades in the body over time and this, says researchers, may contribute to the loosening in cemented total hip replacements.
"This is the first study that shows there is a chemical breakdown in the structure of the cement," said Michael Ries, MD, lead investigator of the study, UCSF associate professor of orthopaedic surgery, and orthopaedic surgeon at the UCSF Arthroplasty Center, part of UCSF Stanford Health Care. "The findings can be used to improve the longevity of cemented total hip replacements."
Ries and research colleagues presented study findings on February 4 at the annual meeting of the American Academy of Orthopaedic Surgeons in Anaheim, CA.
A total hip replacement is a successful treatment for arthritis in the hip, said Ries. If severe arthritis is treated without surgery, often the pain can be so great that walking is no longer possible and a wheelchair is the only option for mobility, he added.
In a total hip replacement, the hip joint is replaced with a metal ball attached to a metal stem fitted into the upper portion of the thigh bone and a plastic socket is implanted into the pelvis, replacing the damaged socket. Approximately 50 to 60 percent of total hip replacements use cement to anchor the ball and socket into the bone, according to Ries.
One possible complication of a total hip replacement, he said, is the metal ball
and plastic socket may become loose, resulting in pain. If loosening is
significant, a revision of the joint replacement may be needed. About 90
percent of hip replacements last 10 years and 80 percent last 20 years.
In the current study, Ries and research colleagues studied the chemical
structure of bone cement used in hip replacements -- polymethylmethacrylate
(PMMA) -- after it had been in the body to determine the effects of the body's
environment on PMMA
Contact: Lordelyn P. del Rosario
University of California - San Francisco