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There are many types of total hip replacement devices or
prosthesis. There are many hip implant designs and
materials. The hip replacement devices or prosthesis come in
three broad categories:
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Metal with Polyethylene Liner Devices
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Metal on Metal (MOM) Devices
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Ceramic on Ceramic Devices
The Plastic liner in the Metal with Polyethylene Liner
device is the hip implant's weakest part for the metal and
plastic devices. The plastic wears away at a rate of about
one millimeter per year or 1/40th of an inch as it rubs
against the metal ball of the femur device. This type of
implant has a life expectancy of about 10 to 15 years. Newer
types of Polyethylenes have been used in more recent years,
but plastic particles are produced by daily wear and the
very small pieces soon migrate between the implant and the
bone. The body reacts to the foreign particles and produces
an enzyme which will slowly dissolve the bone. This will
eventually result in the loosening of the implant.
Metal on Metal hips were introduced in the US in 2002. They
had been used in other countries for many years before the
were approved in the US. The ball and socket of the Metal on
Metal (MOM) hip devices are made of Cobalt-Chrome. It is
believed that the MOM will never wear out in a person's
lifetime. But there is still a chance of loosening after
many years of use. There has been some health concerns about
the metal ions that are created when the metal parts cause
friction. The Metal on Metal hips have been used for more
than 16 years in Europe and there have been no reports of
problems to date. There have been a number of studies about
the Metal Ion Issue.
The Ceramic on Ceramic Devices are newer types of hip
prothesis. The ball and socket are made from ceramic. The
ceramic is an oxide from aluminum oxide. The wear with the
Ceramic Devices is even less than with the Metal on Metal
hips and there are no metallic ions to worry about. There is
a chance of the ceramic components fracturing. The risk is
about 1 in 25,000 ceramic components fracturing. Other than
the very small risk of shattering, the all ceramic hip is a
very good choice for most patients and especially for the
younger and more active person. The larger size ball and cup
of the component makes dislocation much more difficult than
the small, old fashioned metal and plastic hips that were
used years ago.
The Metal on Metal and Ceramic on Ceramic hip devices are
more expensive than the old fashioned metal with plastic
insert hips. Many people including older people have long
life expectancies and should choose hip devices that have
long life expectancies. Only a surgeon can decide what is
best for you, but make sure you are knowledgeable about what
he is suggesting. Ask questions about the device and do some
research to make sure you are getting a hip that will last a
long time and will not dislocate easily.
Additional References about Total Hips Replacements:
Total Hip Replacement by Dr. De Smet
Dr.
Huddleston's Discussion of Different Hip Replacements
Basics of Total Hip Replacement at Bone Smart
Hip Replacement History and Information at Wikipedia |
