knee replacement and cycling - Page 2

08-03-2004, 07:34 PM

Terry Morse wrote:

> Patrick Clark wrote:
>
>
>>Does anyone know of any data about competitive cyclist who have had a total
>>knee replacement? What are reasonable expectations after the surgery?
>
>
> Here's a decent overview article from the American Journal of Sports
> Medicine:
>
> [Only registered and activated users can see links. ]
>
> I read another article about the young "X Games" athletes who are
> getting joint replacments at 30 or younger. Longer lasting materials
> are being used for these young, active patients. Sorry, I don't
> remember in which magazine I read the article.
> --
> terry morse Palo Alto, CA [Only registered and activated users can see links. ]

That's a good survey article, but it doesn't mention at all what is
probably the best type of hip replacement for the active and athletic
person. This may be because it is not through all the FDA approvals for
general use although it is well past the experimental stage. Anyway this
technique is surface replacement.

In the standard technique the end of the femur is cut off and a large
pin with the ball on the end is inserted down in the marrow of bone. The
socket part attached to the pelvis is polyethylene. This contains the
seeds of its own destruction, or at least the need for revision (read
replacement of components). The polyethylene wears and the wear
particles provoke an allergic reaction in the bone (osteolysis) which
loosens up the pin in the femur. The time scale of this is usually 10 to
15 years, not a problem if you don't live that long, but a serious
problem for the active athletic person. To minimize wear rate the size
of the ball is relatively small compared to that of the natural joint.
Unfortunately this makes it much more susceptible to dislocation that
the natural joint. There have been improvements in materials, more wear
resistant polyethylene, or ceramic components, but they all seem to stay
with the relatively small ball diameters and the big pin down the femur.

In the surface replacement technique, the end of the femur is left
mostly intact except for the ball being ground down to a peg and a metal
(cobalt chrome) ball is attached to it. The socket is also the same
metal, so that in effect they are just replacing the worn surfaces. The
metal is very hard and the part are machined and polished to quite
exquisite tolerances. The wear rate is very small compared to the
metal/plastic combination, and the diameter of the ball similar to that
of the natural joint so it much better resists dislocation. Worst case
if it were to become necessary, there is plenty of good bone left to do
a standard type of replacement.

My interest in this is that I have such a joint replacement. About five
years ago at age 54, osteoarthritis had about done for my left hip. I
did a lot of research and found out about this type of replacement. I
had it done a the Joint Replacement Institute at Orthopaedic Hospital in
Los Angeles. Since then I have never looked back. Range of motion of the
replacement joint is as good or better than the natural one, and I have
no sigificant restriction on my activities other that good sense (I
don't bungee jump). I didn't go back to running because I found cycling
more interesting. I have done more challenging backpack trips since the
replacement than I had been doing before it was needed. I am a relative
wimp compared to some of the folks I have heard of who have surface
replacements, including an Ironman competitor.

For anyone interested, there is more information at
[Only registered and activated users can see links. ] There is also
[Only registered and activated users can see links. ] and a Yahoo group of former and prospective
patients [Only registered and activated users can see links. ]

Mike