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Mobile bearing vs fixed bearing prostheses for total knee arthroplasty for
post-operative functional status in patients with osteoarthritis and rheumatoid
arthritis
Jacobs WCH, Anderson PG, Limbeek J, Wymenga AAB 2008
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COMPLETE STUDY
Which type of knee implant is better in Total Knee Replacement surgery for
osteoarthritis and rheumatoid arthritis of the knee: mobile or fixed bearing?
To answer this question, scientists analysed 2 studies that tested over 150
people with osteoarthritis of the knee (6 had rheumatoid arthritis). These
people had total knee replacement surgery with either a mobile or fixed bearing
knee implant and were studied 1 or 7 years after the surgery. These studies
provide the best evidence we have today.
What is osteoarthritis and rheumatoid arthritis of the knee and what types of
knee implants are there?
Osteoarthritis and rheumatoid arthritis are two forms of arthritis that can
affect the knees. In some people, damage and pain in the knee from arthritis may
be severe enough for surgery. In these people, the whole knee joint can be
replaced by an artificial joint or knee implant. In total knee replacement
surgery the ends of the long bones of the leg are usually replaced with metal
ends and an insert is placed in between them. The insert can either be "fixed"
into place on the end of one bone or not as fixed which makes the insert more
movable or "mobile". It is thought that people with a mobile bearing may be able
to move their knee more and function better than people with a fixed bearing.
What did the studies show?
The two studies show that the range of motion/movement of the knee was about the
same in people who had a fixed or mobile bearing knee implant. The year long
study shows that slightly more people with a mobile bearing knee implant had
less pain and better function than with a fixed bearing knee implant. But the
seven year long study showed no differences in pain or function between the
mobile or fixed bearing knee implants.
What is the bottom line?
The level of quality of the 2 studies in this review is "silver". It appears
that mobile bearing knee implants provide the same amount of range of
motion/movement and pain relief as fixed bearing implants in total knee
replacement for osteoarthritis and rheumatoid arthritis of the knee. Ability to
function with either type of implant is also the same.
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