Re: Re: Geoffrey/Roger/cemented stems

December 29, 2002

Hi , et. al.,

It is my understanding that the primary reason for cementing a stem is

immediate solid fixation. It can fill a sloppily sized hole like a " Bondo "

type auto body filler here in the states. The result is almost immediate

pain relief and rapid return to mobility. Stem movement and especially

rotational movement is the primary cause of pain & eventual failure. The

alternative of bone ingrowth takes longer for really substantial improvement

simply because it takes a specific amount of time for the stabilizing bone

to grow in.

The problem with a cemented fixation is (once again, to the best of my

limited knowledge) that even though it is very good cement and sticks to the

implant very well, the body sees it as a foriegner; as in: " You aint frum

aroun here is you boy? " and it grows an isolating film between the surface

of the cement and the bone. This causes the initial loosening and the

resultant movement causes accelerated wear along with more debris and it's

all downhill from there.

To get a cemented stem out for replacement or to remove a sucessfully

ingrown stem requires some pretty extensive demolition work on the femur

followed by just as much reconstruction, and you end up with a really nice

piece of mosaic art, which you will never be able to see in order to fully

appreciate it.

I like the De Puy S-Rom Stem. It has longitudinal flutes which can be driven

into a precisely machined femoral canal. This causes immediate fixation

which does not depend on bone ingrowth or cement. It is inserted through a

proximal sleeve with a Morse taper for locking. This allows it to be rotated

a full 360 degrees into perfect alignment with the acetabular cup. The

sleeve is designed for bone ingrowth yet is initially mechanically located

by being locked to the stem. The beauty of it is that in most cases when a

recvision becomes necessary, the stem can be removed from the sleeve and

replaced with a new one without disturbing the ingrown collar. Also, the

collar fit is tight enough that I believe there have been no cases so far,

wherein wear debris has been able to migrate down into the femural canal and

initiate femoral osteolysis.

That being said, let me show this vacuum cleaner I'd like to sell you.

Seriously if anyone would like me to send you more info which is not

available on the web (ie, fax or surface mail), feel free to contact me

direct.

Feel Free anyway,

Greg

on 12/29/02 3:36 AM, van der Meulen at martin@... wrote:

Here in the Netherlands it is also well known that cemented protheses

live longer. However, they preferred cementless versions in younger

active patients because the revision procedure is easier, and the revised

prothese is expected to live longer. It seems that when a cemented

prothese is getting loose, it will distruct more bone around it. And this

makes revision more complicated. You don't see these arguments back in

narrow viewed statistics (so called 'jumping to conclusions' pitfall).

Re: Geoffrey/

- I agree with you on all points, but I did have a

question/observation: Couldn't the reason for the doubly high

cementless revision rate be simply that those patients outlive

their original prostheses? Since the cemented ones tend to be

placed in very elderly people, isn't it possible that they don't get

revised as often simply because the people they're in aren't

around to be revised? There may be something I don't know

here, but it seems like a plausible explanation.

And Sweden! Let us point out that here is yet another country with

a single payer, socialized system that surpasses the U.S. in an

area of important research and the delivery of quality medical

care - not to mention innovation. I find it fascinating that so many

countries offering the socialized medicine that is so reviled here

in fact provide better care and information to their citizens - both

rich and poor - more economically than we can in our so-called

" for profit " system. It's not a surprise to me that the richest

country in the world can't get it together to have a joint

replacement registry: There's little political will here to do

anything that doesn't promise a chance to turn a fast buck.

sheila

-

-- In surfacehippy , " Frost "

<roger@r...> wrote:

> I have just posted the following under 'well well well' for

Geoffrey on TH

> YOUR QUOTE

> I had simply heard that there were restrictions on irradiated

materials in Germany and speculated that this might be a

reason for differences.

> REPLY

> I am a Mechanical Design Engineer with past responsibility for

products exported to Germany. I have no knowledge of what you

state you heard. It just does not tally with ISO (International

Standards Organisation) with which the Germans are signed up

active members.

>

> YOUR QUOTE

> Your speculations are at least as valid, though I am not sure

why our litigious society should be more of a problem for

resurfacing technology than for the others, which are hardly

perfect.

> REPLY

> Familiarise yourself with

http://www.wattslawfirm.com/13_15.5mil.html WATTS & HEARD

CLIENTS AWARDED $15.5 MILLION IN FIRST FAULTY

HIP-IMPLANT TRIAL

> Familiarise yourself with

http://www.oxmed.com/docs/datafiles/swedish%20hip%20regist

er.html

> The bottom of the 4th paragraph reads that revisions in the

USA are 2x those of Sweden, UK and Australia. What

manufacturer would let their product be used ad hoc with this

knowledge. The FDA resurfacing trial is taking place with a

select number of OS's - I wonder why!

>

> YOUR QUOTE

> The problem of training is a very valid point. However, it really

makes getting the technology difficult here. And, if there is a

problem (and there are always problems) finding someone who

is reasonably close who can handle these devices is a

compelling negative.

> REPLY

> Please see above. I don't think it needs spelling out.

>

> YOUR QUOTE

> I would like to know where you get your figures and over what

period of time those 4455 resurfaces have been done and how

old they are. If they were all done 15 years ago, I am impressed

(and dubious) if they are all done yesterday the number is hardly

impressive at all. I could be mistaken, but Resurfacing has not

yet stood the test of time.

> REPLY

> Familiarise yourself with

>

http://www.ahfmr.ab.ca/hta/hta-publications/technotes/TN33.pdf

> (ALBERTA HERITAGE FOUNDATION DOCUMENT)

> Familiarise yourself with

> http://www.jru.orthop.gu.se/archive/AAOS-2000-NHR.pdf

> The figures I mentioned only go back to 1997 but other figures

go further back. THR was started by an Englishman some time

back. Similarly so was Resurfacing over 65 year ago - I think

both have stood the test of time.

> I anticipate you will dissect these sites and choose the bits that

suit yourself - they are unbiased reports, and as with everything

there are pluses and minuses (added together they make an

equation). They should stay as they are and the conclusions be

held

>

> YOUR QUOTE

> It would be very nice if resurfacing had more of a go here in the

states. I do not oppose that and I do believe that people should

be free to choose.

> REPLY

> You are right

>

> Now I would like to inform of the part Sweden plays in THR. If it

wasn't for them we would have little relevant historical data.

Whilst everyone else was collating some data no real definitive

work was taking place except for guess where - SWEDEN.

> There data is published annually in Swedish - they publish an

English language version two years later. This can be viewed on

> http://www.jru.orthop.gu.se/archive/AAOS-2000-NHR.pdf

> It is generally used by OS's the World over - The American

Academy of Orthopedic Surgeons: www.aaos.org. refer to it at

there annual conventions.

> Now if you look at the Swedish site you will find that cemented

THR is carried out far more than cementless THR. Also the

cementless revision rate is an awful lot higher. I don't mind

personally what comments are made on this and other sites but

I am occasionally stirred when they defy data that is only too

readily available.

> I would now like to introduce a paper that is from the American

Academy of Orhtopedic Surgeons re Resurfacing

http://www.aaos.org/wordhtml/anmt2001/sciprog/268.htm.

> This is with information that goes back with data for almost 12

years.

>

> PLEASE NOTE

> Most of these sites require a download of Acrobat Reader - the

read only version is absolutely free from Adobe on

www.adobe.com/products/acrobat/readstep2.html.

> It is useful in that it enables a text document to be read

universally without the need of a specific word processor

software package.

>

December 29, 2002