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How does partial knee replacement surgery
differ from total knee replacement?
Arthritic knee joints may be repaired either
partially or totally - known as partial knee
replacement and total knee
replacement. A partial knee replacement is also
called unicompartmental or "UNI". If the bone
disease is restricted to the inner side of the knee
(the 'medial' side), the surgeon will simply reshape
those damaged surfaces. The repaired surfaces on that
one side of the knee are then partially covered with
a combination of metal and plastic bearings. For this
reason, a UNI knee replacement is considered less
invasive and can provide much shorter recovery times
from the operation.
The primary limitation with the UNI procedure is that
the surgery only works for bone that has not been too
damaged by the arthritis. It also requires that the
other ('lateral') side of the knee joint have healthy
cartilage. The average age of UNI knee patients will
therefore be a lot younger than those going for total
knee replacements. This means that the UNI
resurfacing option may only be a good choice for a
small percentage of knee patients.
Generally speaking, UNI knee replacements are not
performed on patients with arthritic damage on both
sides of the knee. In more arthritic knees, there
will be considerable erosion and deformity on both
sides of the knee joint (as in 'medial' and 'lateral'
sides). This will require more repair of the upper
joint bone and the lower joint bone and sometimes
also behind the knee cap. The UNI knee cannot
accommodate such destructive changes in bone
structure. Therefore in this case a surgeon will
often opt to perform a total knee replacement -
resurfacing bone with metal cap and tray.
Note that the most common method of fixing both
implants to the bone is with bone cement. There are
also options to provide for bony attachment and
ingrowth onto the implants (bone ingrowth fixation).
The final step is to insert a plastic cover onto the
metal tray to act as the bearing knee for the knee joint.
There are other options to consider. The majority of
knee patients do not get their patella replaced
although this may become an option further down the
road. There are also indications for knee operations
that make use of smaller incisions (MIS: 'minimally
invasive surgery') and use different kinds of
instrumentation such as computer-assisted navigation
(NAV).
Your doctor should explain to you which type of knee
replacement surgery is best for you and why.
About Bonesmart.org -
BoneSmart.org is a National Public-Awareness Campaign
for Candidates of Hip Replacement Surgery and Knee
Replacement Surgery. The BoneSmart(r) National
Consumer Awareness Campaign's mission is to raise
patient awareness of the options available to persons
diagnosed as a hip replacement or knee replacement
candidates by providing an Internet portal for
awareness of the latest advances in joint replacement
materials, their longevity and suitability for
various applications. With this information the
potential patient may be better informed when
discussing options with his or her surgeon.
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