does anybody know how long a total hip replacement lasts???how long does the metal to metal last???ive read that the metal to metal replacement lasts about 15-20 yrs.anybody knows about this????can it last longer,depending on the person???
hip replacement question
- Thread starter tito8512
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Tito,
Total joints arent like a jar of mayonnaise--they dont have expiration dates.
Although yours seems like a simple question, the answer is very complex and not easy to understand.
First, total joint outcomes are measured in per cent survival at a given time point, not how long they last. For example, 700/1000 of hips followed to 10 years are without revision or explant = 70% survival. They best way to evaluate them is to set up survival curves. I never tell people how long to expect their hip to knee to last, but rather I quote them odds of keeping that same joint for X number of years, based on the literature and type of joint they are looking at.
Second, there is a large variation between patients. If they get an early infection, theyll keep it for 6 weeks. If they get loosening, they may have it 6 months. If they have malpositioning, they may get early wear and have it 2 years. Depending on how many cycles the patient puts the joint through can affect the longevity. Although sometimes loosening occurs irrespective of load or number of cycles.
Thirdly, the material is constantly changing and its impossible to know directly how long the highly crosslinked polys are going to last or how long the new metal on metals or large/jumbo diameter components are going to last. We can speculate, but the reality is that the only 20-30 year data is on old prostheses implanted by old methods. So I always qualify my conservative estimates with the phrase: But the materials and methods are getting better and better so those number are a conservative estimate.
I suggest that you do a literature search to find a few articles on total joints so that you can see how they are written and base your take-home point on them.
Hope this helps,
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Hey - I know they can do ceramic-on-ceramic joints in Europe, but are you guys able to them here yet? I've heard the ceramics don't wears out as fast and generate fewer wear particles in the joint than UHMWPE joints.
OP - check out PubMed and you'll see tons of articles on this subject.
OP - check out PubMed and you'll see tons of articles on this subject.
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Ceramic on Ceramic do have the incident of fracturing the ceramic head, that would be the only risk that would be out there in the literature to date from what I've read. However I think the newer larger head prosthesis with the increased surface areas are going to revolutionize the THA industry. However data to support that won't really be available for several years. I think the metal on metal large heads do generate less wear debrie compared to the smaller heads. Lower dislocation rate is huge as well. We just don't know how long they'll last yet.
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Larger heads? I hadn't heard about this design change. How much larger? Can you post a link? How about prosthetic knees - I thought they were about as big as you could get (anatomically). Are they trying the same thing there?
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The trend in knees is a little bit the opposite. Lower profile designs with alterations in the radius of curvature in the femoral component are meant to enhance flexion. The rationale for large heads in hips is reducing the dislocation rate. Traditional heads were 28mm then 38mm became more popular. Now you can get 60mm heads. I work with an orthopod that puts a lot of these in, and he has excellent early results. As the other posts indicate, its the long term info we are waiting for. One other aspect of metal on metal is metal ion issue. There isn't a lot of data on safe levels in the blood and tissues, so who knows what to do about the studies showing high levels following metal on metal arthroplasty. The downside to ceramic on ceramic is the size limitation. Thinner cups means higher incidence of fracture, so you are limited to a thicker acetabular component that will fit the patient, and a head that is smaller to fit the cup. Ceramic on ceramic versus metal on metal is the big debate right now, but at a local meeting last month I hear talk of metal on ceramic being attempted. Also they now have new UHMWPE made with Vit E ,which binds free radicals and is meant to reduce wear. I don't think there will be one best design, just better things for different people.
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The larger metal on metal heads for Biomet is what I'm very familiar with. The Biomet Magnum heads allow you to put in just about any acetabulum, and the head is 6mm smaller than the acetabulum. So if you ream I think it's two under, so ream to a 52mm, you put in a 54mm cup, and the head is a 48 mm head. This is really giving you imho, the most anatomic relationship possible. Plus the neck design really limits any type of impingement or leveraging of the neck against the cup for dislocation purposes. They are said to have nearly 180 degrees of movement (that's not possible of course) but they have probably 160 or so. You can obviously use a variety of different femoral stems, from taperloc, etc I believe. Patients my physician and I worked with did very well so far with them. As stated above it really helps with dislocation, and one might be able to even relax current hip precautions as well. Metal ions and wear are what we have to worry about, but i wonder with decreased force per square area due to the larger head, will the wear be as much. I'm sure there is some study out there talking about that, or someone should do one atleast. Just some random thoughts I guess, but as stated, there are many options and until we see the long term data, it's going to be interesting to see where it goes.
Check out their website www.biomet.com , I think Wright has a mega head as well.
