Midterm Results
Show Positive Outcomes for
Ceramic-on-Ceramic Total Hip Replacements
March / April 2002
Midterm results show that new ceramic-on-ceramic hip replacement
prostheses provide increased durability and function for patients.
"This technology represents a true breakthrough in total
hip replacements. We expect the majority to last 30 years
and beyond," says Jonathon
P. Garino, MD, an orthopaedic surgeon at the University
of Pennsylvania Health System, who has performed more than
300 ceramic on ceramic total hip replacements.
Traditional total hip replacements are comprised of a metal
ball and plastic liner. The FDA approved the use of a ceramic
ball for total hip replacements 13 years ago in the United
States. Penn is just one of a few centers across the country
selected to participate in several Investigational Device
Exemptions (IDE) that utilize a ceramic ball and a ceramic
liner for total hip replacements. Since 1997, three randomized
IDE studies have been completed involving hundreds of patients
and a fourth study is ongoing. Midterm results show no differences
between the groups.
"The FDA should approve the ceramic liner in the next
six to 12 months. In 10 to 15 years, we should start to see
the advantages," adds Dr. Garino.
Socket hip replacement components are composed of four separate
parts - a stem, a metal socket or shell, a separate plastic
or ceramic liner for the socket and a trunion protruding from
the stem where the metal or ceramic ball is placed. This four-part
design separates and optimizes the fixation and articulation
functions.
Advantages of Ceramic-on-Ceramic
The fracture rate has been reduced to about one of every
25,000 parts that are implanted, which means that other parts
of the total hip replacement technology are 35 times more
likely to break than the ceramic ball or liner. When compared
on a hip simulator in a laboratory, ceramic-on-ceramic has
a wear rate of about 200 times less than metal on plastic.
Previously, a young patient was not usually a good candidate
for a total hip replacement due to osteolysis (bone loss)
and the need to replace the device every 10 to 15 years. This
bone loss made subsequent replacements, or revisions, very
difficult. "The friction between the metal ball and the
plastic cup in traditional hip replacements create wear debris
(little particles of bone, cement and metal) that wear and
scratch a metal ball. These fine scratches abrade the plastic
and destroy bone," says Dr. Garino. "Next to diamonds,
alumina ceramic is the hardest material on the planet; therefore,
the debris does not blemish the ceramic components."
Also, ceramic-on-ceramic technology allows orthopaedic surgeons
to use increasingly larger ball heads without increasing the
size of the trunion, which increases the volumemetric wear
(shed more particles per step). The standard ball head size
is 28 mm, but Dr. Garino routinely uses 32 mm and is investigating
increasing the ball head with future designs. As the ball
head size increases, patients increase their range of motion
and reduce their dislocation rate.
About 95 percent of patients report good to excellent results
and are able to return to their normal activities, including
playing tennis or golf. "For now, we are conservative,
ten years from now these patients may have the ability to
run marathons," adds Dr. Garino.
Any patient who needs a primary total hip replacement and
is relatively active may be eligible for this research study.
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