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Patellar failure

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whaler

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Hi. I'm a 48 male who had my right knee replaced 36 months ago. The doctor used a DePuy/J&J prosthesis. I went through the rehab and felt fine for over three years. About six months ago I started having some regular pain and swelling at the front and outside of my knee. The pain and sweeling increased over time, I went to see the doctor and I explained my symptoms. He took an Xray and compared it to my post surgical xray. It seems that the part cemented behind the patella has fallen off from behind the patella and is floating in the knee. I am scheduled for a patella resection/revision in the next two weeks. I have never abused the knee with over exertion since the TKR.
1. Is this a common failure?
2. Should I be upset at this failure?
3. What should I expect from this new surgery?
4. Is this part necessary, or can one live ok without replacing it with another?
 
Oh my goodness, whaler! What terrible bad luck.

Is this a common failure - I would say not- I have never met or even heard of this occurrence before. Thing is, the patella is actually quite a small bone, quite thin except in one spot as can be seen here


[Bonesmart.org] Patellar failure


The surgeon has to hold it with a special clamp whilst creating a plug hole in it for the bone cement. Then it has to be held firmly (in another clamp) whilst the cement sets which is about 6-8 minutes.

I have said elsewhere that the majority of "failures" - especially loosenings - actually occur in the bone/cement interface and this can be down to various things

1. inadequate preparation of the drill site
2. insufficient drying and cleaning of the site
3. poor cement security - i.e. bedding of the cement into the matrix of the bone
4. moving or releasing the clamp before the cement is completely hardened.

However, it should also be noted that other factors come into play. There is a condition known as resorption where the bone, when placed under long term pressure, actually begins to be re-absorbed by the body. It's a natural process that occurs all the time as the healthy bone grows from within outwards and on the outside of the bone, the old, dying cells, are resorbed so the bone keeps its shape. But this can happen in unwanted places as well and at the cement/bone interface is a favourite spot. It is more often observed where the femoral prosthesis loosens that it is found to be the bone actually dying back from the cement. This can be prevented in part by making sure the cement is forced into the bony matrix so it is not put under the stress that can precipitate it, but it can happen spontaneously without that.

3. What should I expect from this new surgery?

The knee will have to be reopened as it was before though perhaps not quite so extensively. Therefore the rehab will be some of the same.

4. Is this part necessary, or can one live ok without replacing it with another?

The button is necessary to aid the quadriceps ligament's tracking over the femoral component. Without it, the rough underside of the patella would hinder the smooth action. In that respect it is necessary.

On the other hand, people who have fractured their patellas and have had them removed, manage quite well without them. But the recovery from a patellectomy would be worse than that from replacement of a patellar button!

 
Josephine: Thanks so much for your response. Your knowledge and information is a great help to me. After a total of 7 surgeries on the knee, I figured the TKR would keep me out of the operating room at least ten years. Now one more. Well, I will hope that it won't be nearly so invasive as a TKR.
 
You're most welcome. I only hope it is a brief and easily recovered from surgery.

BTW when I said "It is more often observed where the femoral prosthesis loosens that it is found to be the bone actually dying back from the cement." I should have made it clear that I was referring to the femoral prosthesis in HIP replacements, not knees.
 
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