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TOTAL KNEE
REPLACEMENT
It is a well known
fact that people are living longer and pursuing higher levels of activity at an older age
than was ever possible in past generations. The orthapaedic reconstructive surgeon
has often struggled with the problems of knees whose surface has worn out and can no
longer provide a buffer upon which the patient can walk without pain. Over the last
25 years many orthapaedic procedures have been developed to help men and women maintain
higher activity levels as they age. Earlier generations were quite simply forced to
use canes, crutches, wheelchairs, and in fact were bedridden as their deformities and pain
became worse.
In order to
understand what reconstructive surgeons do today in helping these types of patients which
advanced arthritis of the knee, it is important to review a little bit of the basic
anatomy. There are two bones which form the knee joint. One is the femur which
is the thigh bone, and the other bone is the tibia which is the lower leg bone. The
ends of the bones are lined with cartilage which has no blood supply. It is
nourished by the synovial fluid which is produced by the lining of the knee joint.
The supporting structures of these two bones are called the ligaments and the
capsule. There is a lining within the capsule which is called the synovial lining,
which creates the synovial fluid.
Over a period of
time the articular cartilage (the cartilage that lines the ends of the bones) starts to
wear away. When it wears awat to a significant degree, you then have bare bone
rubbing on bare bone, and that's when the deformities and the extreme pain occur.
When the surface is
in the process of wearing away, it will shed cells, which we call debris. This
debris will cause irritation of the lining of the knee. This may be treated
conservatively with medications, and/or physical therapy, crutches, canes, walkers or
minor surgical procedures. When nothing helps and the deformities or pain become
severe, the lining is completely worn away and the bones are touching each other in the
joint. This is when reconstructive surgery is usually indicated.
Early attempts at
resurfacing the ends of the bones were rendered successful in the early 1950's and 1960's.
Complete replacements of the knee joint were originally done by a hinged type of
joint. These methods really did not last for a long period of time and so they were
abandoned quite quickly. It has really been over the last 10 years that total knee
replacements have been rendered quite successful and in fact achieve over a 90% success
rate for pain relief, getting rid of the deformity, and allowing the knee to bend more
normally so that the patient can use it for activities of daily living.
Years ago, it was
common to use cement to fix the implants to the patient's bone. Technology has
advanced to the point where we now have biological fixation of the implants to the bone.
The latest addition to this fixation process is the use of hydroxy appetite, a
substance normally found in bone which promotes the bone growth into the prosthesis.
Before 10 years ago the problem of wear was a very real one. Today, however,
we are employing prostheses whose wear characteristics are markedly improved over those
that existed 10 years ago. So we are on our way to solving this problem of wear in
total joint replacement and specifically in the knee.
The other problem
that presents itself in modern day total knee arthroplasty is that of reconstructing the
joint surface of the knee cap. Attempts are being made right now by all the
companies to improve the technical aspects of putting in a kneecap joint. If
revisions of this joint have to be performed, it can certainly be performed by complete
reconstructive surgery.
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