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Cementless hip implants are durable for at
least 20 years
Despite the common perception that total hip
replacements last about 10 years,
researchers at Rush University Medical
Center have found that the devices are
extremely durable, even 20 years after
surgery.
Clinical and radiological evidence showed
that 96 percent of the 124 cementless metal
components assessed remained securely fixed
in place 20 years post surgery, according to
a study published in the May issue of the
Journal of Bone and Joint Surgery.
These components, which fit into the
cup-shaped hip socket, or acetabulum, were
among the first implants designed with a
porous structure to allow bone to grow into
the surface in the hopes of achieving
long-term fixation.
"Our results confirm earlier work done at
Rush and at other institutions: that
cementless acetabular components work very
well and that long-term biological fixation
can be obtained," said Dr. Craig Della
Valle, an orthopedic surgeon and principal
author of the study.
Over the last two decades, the researchers
have been studying the results for 204 total
hip replacements performed at Rush in the
mid-1980s in a group of 184 patients ranging
in age from 20 to 84 years.
Findings were previously reported at 10 and
15 years.
The implants studied were the Harris-Galante
I acetabular component, whose design was
based on pioneering research work done by
Dr. Jorge Galante, former chairman of
orthopedics at Rush and a co-author of this
study.
Earlier-generation implants, which relied on
special cement to secure the device to the
patient's bones, had been shown to have
higher rates of failure, particularly beyond
10 years.
"The hope was to provide more durable
fixation, especially for younger patients
with a longer life span," Galante said.
In the present study, the researchers
analyzed results for 124 hip replacements in
the 111 patients who were still alive 20
years or more after surgery.
Since the previous report at 15 years, two
metal cup implants, in addition to the three
noted earlier, were found to be loose, or 4
percent of the 124 implants.
Of the original 204 hip replacements, five
cases, or 2.5 percent of the total, had
failed. Two of these five implants were
revised, but three were left intact because
the patients did not suffer significant
symptoms.
However, in nearly 20 percent of the
patients still living 20 years post surgery,
the plastic lining of the metal shell had
worn enough that repeat, but less involved,
surgery was required or recommended.
Younger age strongly correlated with a
higher risk of wear-related problems, the
study showed.
"The average age of the patients in this
study was 52 years, much younger than most
patients who underwent hip replacements at
the time.
"So
the high rate of wear-related complications
was not completely unexpected," Galante
said.
Also, with time, the number of surgical
revisions has increased due to osteolysis,
or bone resorption as a result of the body's
reaction to debris created by wear and
corrosion of the metal implants.
"With time, the number of repeat surgeries
due to wear and osteolysis has increased, as
have the numbers of cases of osteolysis we
identified radiologically.
"But
with the newer, more wear-resistant bearing
surfaces we are now using, we believe that
fewer patients today will need revision
surgery for these reasons," Della Valle
said.
"This longitudinal study gives us a wealth
of data to use as we continue to improve on
techniques and materials for total hip
replacements," Galante said.
###
Rush University Medical Center's orthopedics program ranks
tenth in the nation, according to U.S.
News & World Report. Physicians from
Rush serve as the team physicians for the
Chicago Bulls and the Chicago White Sox.
For more information on orthopedics at Rush, visit
http://www.rush.edu/rumc/page-R11726.html
or call (888) 352-RUSH.
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