Wednesday, April 15, 2009

Too young for Knee Replacement


Why do surgeons say you are too young for a knee replacement? Shouldn't your pain be the primary factor in the decision to have surgery?

As usual there is more to it than meets the eye.

Surgeons take a long view when advising on joint replacement surgery. These operations have a limited lifespan and each successive operation is technically more difficult and has a much poorer outcome. The other thing they consider is the demand you will be placing on the new joint. A 40 year old does more walking and exerts higher forces by doing more stressful activities than a 65 year old. This means that the lifespan of the joint replacement is likely to be less.
I like to compare the replaced joint to another mechanical object, the car.
You don't expect a car to last forever. It is likely to last longer if owned by a nice little old lady who rarely drives and when she does, it is for short distances in a careful manner. It is likely to suffers significantly more wear if driven aggressively and frequently over long distances by a 40 year old man.
Modern prostheses are made of very durable materials and last for many years. The same unfortunately cannot be said about your bones. No matter how good the materials of the knee replacement, they still have to attach onto your bone. When joint replacements 'wear out' - it is often the bone, not the prosthesis that gives. The result is loosening of the prosthesis and revision surgery is required.
Revision surgery is not a repeat of the first operation. More bone is cut away and longer stems inserted into the bone. Knee range of motion is likely to be less following revision surgery, and the complication rate higher.
This is why surgeons do everything they can to delay the initial surgery despite your pain. A primary knee replacement at 40 could mean revision by 50 and mobility threatening complications before 60. Of course this may not happen, but the risks should be understood before any big decisions are made.

You can always opt for surgery later, but once its done, you can't undo an operation.

EDIT: 23rd Feb 2011: This has proven to be one of the most controversial topics at The Arthritic Knee. On a number of internet forums there has been much discussion about this post and quite a number of people questioning the source of the data used to formulate this post (and mentioned in the comments section by me). Some have even labelled this data a complete fabrication. To clarify the point being made here, below I provide a link to the source, The Swedish Knee Arthroplasty Register. This is arguably the worlds most complete data set on knee replacements and has been running prospectively since 1975.
The 2004 study mentioned in the comments section below can be found here:

It shows that the younger a patient is when a knee replacement is first put, the shorter the lifespan of that replacement.
In response to those saying "they were old knee replacements, new ones are much better" I refer to the following paragraph:

"The results showed a higher cumulative revision rate for the group of younger patients in all statistical analyses and the risk ratio for revision was significantly lower for the group of older patients. The risk for revision decreased for both groups when considering the year of surgery. This is probably attributable to better implant components and surgical techniques."

To paraphrase: "Yes things are getting better but despite this, even with better implants and better surgical techniques, the younger you have a knee replacement, the sooner it is likely to fail".

Anyone questioning this data will not be able to provide any evidence of a similar power as it does not currently exist.

The Swedish Knee Arthroplasty Register has long been recognized as the Gold Standard of Orthopedic data. Until a better source of information becomes available, health professionals will use their experience and this type of data to guide clinical decisions as this is the most scientifically sound evidence at their disposal.


7 comments:

  1. Out of date info - was very true 10-15 years ago but technology advances!!

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  2. I would be very interested in this new technology. As mentioned in the above article, it is not the materials that tend to fail, it is the bones they attach to. Aseptic loosening is still a very real reason for early failure of knee arthroplasty in younger individuals.

    A 2004 study comparing older and younger patients investigated a total of 35,857 knee replacements. It found a higher revision rate for younger people in every statistical analysis.
    Yes, things are better than they were 15 years ago but there is still a very good reason to delay surgery for as long as possible. This information is current I'm afraid.

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  3. You base the information on a study the was complete in 2004 that used information 10-15 years ago...you validate the out of date nature of you information....its 2010...in the last 5 years the TKR has changed dramatically and in the last 2 years even more...the FDA just approve Smith and Newphew to market a knee that can last in wear simulator tests 30 years...Biomet has a vitamin E approved knee that the cleveland clinc says can last longer the underwards of 25 years....

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  4. Hi Norma,
    Again I refer to the point that the problem is not the implants but the bones they attach to. I have no doubt simulated tests last the equivalent of 30 years. As I mentioned in the post, the prosthesis-bone interface is the problem. The average knee is not revised because of component failure but because of loosening. The prosthesis could last 100 years but if it becomes loose it needs revising.
    As for figures on revision rates, these will always be "out of date" as you need to wait until a prosthesis fails before you get the information. We will only know how long a 2010 knee lasts in 15 - 20 years when we have the data. We hope we are improving but we don't know until the numbers are in. The 2004 study looked at over 35,000 knees so gives an excellent indication and is the most current of its size.
    Not all changes work out for the better. Just last month De Puy recalled a Total Hip replacement that was failing twice as much as the average. Smith and Nephew and Biomet make large claims because they are selling implants and it will take 20 years to prove them wrong.
    My advice remains the same: Young people should think very hard about the risks and benefits of a knee replacement.

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  5. Lets slow down a little here....You really dont understand the full picture and are just spewing mis information in you blog....i fear some people might actually follow your advise....I have worked in this industry for 13 years...2006 is when the new cross-linked liners started being put in people so your info is backward looking....

    What causes the bone to weaken and hence the TKR to fail?

    In any total knee replacement there is a highly polished femoral component that is designed to slide and rotate over a very dense piece of plastic (polyethylene) which is secured to the tibial metal base plate. When two surfaces are designed to move upon each other, there is friction between the two surfaces leading to wear. Over time the plastic starts to wear away, somewhat similar to how rubber wears off of a tire.

    As the plastic is worn down, tiny particles are shed off to the periphery of the joint where a variety of normal and protective cells in the lining of the joint try to remove them. In this complex biologic process, the ingestion of the particles by these “housecleaning” cells causes the release of a variety of substances that actually lead to the resorption and weakening of the bone which supports the metal implants. This process is known as osteolysis and the holes left in the bone are referred to as lytic defects which can grow quite large in size and are susceptible to fracture and deformation and cause the implant to come lose from the bone...

    Less wear means less failure...knee boy

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  6. Hi Norma,
    No argument from me on the process of osteolysis causing aseptic loosening. Everything wears eventually and the debris is known to cause this effect. My point is merely that young people should seriously consider their long term future before having a knee replacement at 40. Implants from 2006 have a 4 year follow up. Time and again we have seen "advances" not work out - often for reasons no one predicted. The theory is sound but we have no practical proof yet. We can only go on the data published. I consider having a knee replacement at 40 a leap of faith in the new components. I hope they do well but we just don't know yet.
    This is the difference between implant companies and clinicians.
    Companies extrapolate forward, health professionals look at the current data and make their decisions on the best available information at that time.
    "Less wear means less failure" - Lets hope you are right.

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  7. Norma,
    I am closing this discussion as there is little to be gained from continuing. Repeated comments across this site promoting your company's knee replacement launched in 2006 do not offer a balanced view.

    Just because something was developed recently does not mean it will do all it has promised.

    The 2005 DePuy ASR Hip Replacement system has been recalled this year as 1 in 8 has failed after 5 years. Over 90,000 people have this implant in them worldwide.
    I am sure DePuy were just as confident at the start as you are about your company's knee replacement.
    Surgeons don't say knee replacements last 30 years, implant company employees do.
    Those with knee arthritis should discuss the risks with their surgeon and those in their 40's would benefit from a second opinion before proceeding with joint replacement. It may be the right decision for you, but you first need to understand all of the risks.

    Thank you for your input.

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