Hip Replacement

[Robbie]

Hi,

I am new to this board, just registered in fact. Can anybody please
help me. I have a good few questions as I am due for a hip replacement
imminently. I am still torn between total hip replacement and hip
resurfacing.

My questions are: -

1) What purpose does polyethelyne liner serve in THR?
2) Why is polyethelyne liner not used in hip resurfacing?
3) Is there any more news on the "metal irons" situation in resurfacing?
4) Does anyone know the results of the FDA trials on metal irons in
resurfacing?
5) Why is the resurfacing ball and socket bigger in size than in THR?
6) Why is THR subject to dislocation more than in resurfacing?

Thanks ever so much, sorry to ask so many questions!

Linda.

 

[Matt]

Linda

Whether you go for a THR or a resurfacing is up to you, but my firm belief is that resurfacing is a better option for a first operation. It preserves the femoral bone, and all studies show that resurfaced patients have better activity levels than those with THRs. If a resurfacing wears out or needs revision, it is a simple procedure to go to a THR. If a THR needs revising, then it is a more difficult operation, and the results are not as good.

On your specific questions:

Polyethelene is used as a liner for the ball to swivel in. It was chosen because other liners (eg polyurethane) that were tried (back in the 1970s) wore away very quickly. It was then found that polyethelene itself wore and that the debris often caused a reaction in the bone around the implant, weakening the bone and loosening the implant to the point where a revision operation was needed. Unfortunately the wear of the polyethelene is directly related to the activity level of the patient, so polyethelene liner THRs were found to have unacceptably high failure rates over time in younger, more active patients.

Because of the rate at which polyethelyne wears, a thick liner is needed.

Now with resurfacing, the femoral bone is preserved and the head of the femur is shaved and a metal cap placed on the head. The metal cap is about the same size as the original head. Back in the 1970s polyethelene was tried for the cup, but found to fail (for the reason I mentioned above). Interestingly, metal on metal resurfacings were tried in the 1970s but abandoned when polyethelene came along, as it was felt that the softer polyethelene would be better. Basically the polyethelene failed, while the metal on metal resurfacings (of the 1970s) lasted the recipients the rest of their lives.

No studies have found adverse effects from elevated levels of chromium and cobalt ions after resurfacing (or after metal on metal THRs). Doctors caution that the effects need to be followed over long periods - and this is right. But if there was any adverse effect of any noticable size then we would have seen it in some way by now. After all, 3rd generation resurfacings have been around now for 12 years, and many 10s of thousands have been done.

I mentioned above that the cap in resurfacing is essentially the size of the original femur head. This fits into a metal cup which is press fitted into the pelvis. Because poly liners need to be much thicker than the metal, the ball in a metal/poly THR will be much smaller. It is possible to get large THR metal balls fitting into a metal cup. In fact, if a resurfacing needs revision because of loosening of the femoral cap, it can sometimes be revised to a large ball metal on metal THR using the metal cup already in place.

Dislocations are a real problem with THRs, and small ball metal/poly THRs are the worst. The small size of the ball means it is inherently more likely to dislocate. Also, it has been reported in the medical literature that metal on metal has a "suction fit", ie it takes a lot harder knock to pull apart metal on metal than metal on poly.

One thing that needs to be watched in resurfacings is fractures of the femural neck. This occurs in a small % of patients, and can lead to a need for revision to a THR. Doesn't happen in THRs because the neck of the femur has already been amputated. What does occur in THRs, but not resurfacings, is thigh pain due to "stress shielding" (where the bone at the top of the remaining femur thins out, and the bone around the bottom tip of the shaft thickens), and leg length differences. With THR it is not possible to guarantee that there will not be a disturbingly noticable difference in leg lengths. This does not happen in resurfacings (on the other hand, existing leg length differences cannot be rectified by resurfacing, but can be by THR).

Resurfacing is technically a more demanding operation than THR, so it is important to go to a surgeon that is experienced in resurfacing, not just an experienced surgeon taking up resurfacing.

When I was contemplating a hip operation in the last quarter of last year, I decided on resurfacing, and then looked around for an experienced resurfacing surgeon. I found one that had done more than 500, and I have not regretted my choice for a minute. I've posted a report of my own experience in Thread 75 "Hip Resurfecing" (sic)

In the US, resurfacing is just starting to become recognised, and many still find it difficult to get the operation - and travel to Belgium or India. My hat off to them.

Hope this helps.

Regards

Ross

 

[XxkaytiexX]

i have two resurfaced hips, one is 2 years old and one is 3 years old. if you've been given a choice then you're obviously suitable for both thr and resurfacing (some people aren't suitable for resurfacing) and i would definately say go for the resurfacing. it's much closer to a 'normal' hip when you've recovered from the op, you can do most things you could before without worrying you'll do yourself some damage. the post op recovery is longer, and the op itself is more complicated and leaves a bigger scar (mine are about 12 inches long), but i personally feel there's no contest. find out lots more about both ops, the internet is a good place to get information, and ask your doctor loads of questions until you're satisfied you know exactly what the options are and what is involved for both. good luck.

sue

 

[lalala]

) What purpose does polyethelyne liner serve in THR? It's been the norm, now there is much movement to Ceramic on Ceramic, Metal on Metal, Ceramic on Poly, Metal on Poly and now Ceramic on Metal. This is truely a huge medical debate. What is beneficial for the patient. I chose to have ceramic on metal in my hips. It's not completely approved together, but the studies that I read were very favorable and it just made sense for me so that is what I decided to have. There is great results with today's polyethylene liners since most are made with cross link - poly.. This is the way the material is made and manufactured. Cross link Poly has had great results, but most surgeons tend to move towards what the patients ask for.
2) Why is polyethelyne liner not used in hip resurfacing?
In hip resurfacing, the acetabular shell is already lined with a metal liner built into the shell, so you can't have a poly shell. This is like a Metal on Metal Total hip.
3) Is there any more news on the "metal irons" situation in resurfacing?
This is a huge controversy... Metal ions.. There are more and more studies that show high metal ion levels in the kidneys, leading to renal failure, but it's still a debate.
4) Does anyone know the results of the FDA trials on metal irons in
resurfacing? No clinical trials with surface replacement looking at metal ions. The FDA is looking at outcomes on whether surface replacement will fail.
5) Why is the resurfacing ball and socket bigger in size than in THR?
6) Why is THR subject to dislocation more than in resurfacing?

One of the things that I looked at before I had my total hip was surface replacement, but the way many of the surgeons perform this procedure is like a regular total hip replacement with a more extensive incision. After research, I turned to have a total hip replacement through the Anterior Approach. I found a website called "www.newhipnews.com" and learned that a total hip could be done through the front of the hip. This procedure goes through an interval rather than cut through muscle. All other approaches that I investigated cut muscle or had to extensively repair tendons, etc. This approach seemed to make sense and after talking with a surgeon that did this approach, I was convinced to move in this direction. It was great. back to golfing in 10 days... Minimal pain, I had no precautions, my surgeon said walk and that was it..Hope this helps..

 

[candle-wax]

Your reply is very interesting. I'm new to this forum and the one thing I'm really interested in is hip replacement in India. Anything you have to say about India would be appreciated.