The
arthritis in your knee often results in a deformity, so that
you have become either bowlegged, or more rarely, knock kneed. This is corrected at the time of the surgery so that you become a little knock kneed, the “correct” alignment
for the new knee. |
Imagine
if you will, a straight line running through the centre of the ankle, up to the centre of the knee and on to the
ball
of the hip joint. This imaginary line is the landmark the surgeon uses to make sure the knee is placed in the correct
orientation. The jigs supplied for insertion of the knee replacement assist in accurate preparation of the bone to give good alignment.
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A
jig is applied to the shin bone (tibia) so that the
arthritic part of the knee can be removed with minimal
removal of good bone and the correct alignment of the leg
can be restored. |
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The
diseased bone at the top of the shin-bone (tibia) is then
removed using a special power saw (not unlike that used by a
carpenter!) The amount of bone removed is generally quite
small (just a few millimetres)
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The
diseased bone at the top of the shin-bone (tibia) is then
removed using a special power saw (not unlike that used by a
carpenter!) The amount of bone removed is generally quite
small ( just a few millimetres) |
The
femur is then prepared using this cutting jig. Again, only a
minimal amount of bone ( a few millimetres) is
resected to accommodate the component |
The
"finishing block" is then applied to the end of
the femur and pinned into position. A saw blade is then
passed into the slots in the cutting block to precisely
prepare the bone to accommodate the selected component. |
The
surgeon will test the fit and function of the implant many
times BEFORE implanting the real implant. He can do this
using TRIAL implants. A full and thorough assessment is made
prior to insertion of the final implants. |
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The
tibia is prepared and trialled in a similar fashion. |
The
trial components can be assembled, and the thickness of the
plastic insert can be assessed. The trail insert is blue in
colour here so as not to be confused with definitive plastic
insert made of high density polyethylene. |
The
arthritic process often attacks the patellar too. The knee
cap (patellar) is therefore, often but not
always replaced or more accurately, re-surfaced. |
Thus
the modern concept of knee replacement surgery, compared to
early implants, is to provide more precise instruments
and a more wide range of size and type of implants.
The
best way to illustrate that is to say that suppose you
needed a pair of shoes. The company sends the entire shoe
shop to your home. You measure and choose the shoe which is
the most suitable and best fit, and send the rest back.
That’s what happens with an Orthopaedic implant.
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