What is a knee replacement made of?
*Excerpt from book "The MD Answer Book...on Arthritis" that I am currently writing.
Joint replacements have been around for approximately 50 years. Modern joint replacements generally were developed in the 1960's and 1970's. Over the years there have been many materials used. Currently this is the state of the art:
Knee replacements have three components to them- the part that covers the femur, the part that cover the tibia, and the part that covers the knee cap. Knee replacements are not really replacements. A knee replacement is really a resurfacing of the ends of the bone. For a good review of knee replacements go to this link.
The actual metal is made of a super metal mixture of cobalt, chromium and nickel. To give you an idea of how strong this is, it would take almost an hour to cut through a quarter of an inch with a diamond cutting wheel. To put this in perspective, another common metal used in joint replacement of the hip - titanium - would be cut in half in less than 30 seconds!
The space between the metal pieces is filled with a special polyethylene (plastic). The better products are made of what is called a cross-linked polyethylene. This gives the plastic superior wear characteristics. A review of one of the more modern plastics can be found here.
The quality of the metal and the plastics has led to increased lifespan of knee replacements. Knee replacements generally fail at a rate of 1% a year. That means in 15 years, close to 85% should still be around. Not bad.
Thanks to tremendous engineering research we have come a long way.
Dr. K.
*The excerpt above is Copyright 2006 by Ira H. Kirschenbaum, MD and used with permission.
Related Topics: Joint Replacement Surgery on the Rise, WebMD Video: Need New Knees? There's better metal in Joint Surgery
Technorati Tags: joint replacement, knee replacement
Joint replacements have been around for approximately 50 years. Modern joint replacements generally were developed in the 1960's and 1970's. Over the years there have been many materials used. Currently this is the state of the art:
Knee replacements have three components to them- the part that covers the femur, the part that cover the tibia, and the part that covers the knee cap. Knee replacements are not really replacements. A knee replacement is really a resurfacing of the ends of the bone. For a good review of knee replacements go to this link.
The actual metal is made of a super metal mixture of cobalt, chromium and nickel. To give you an idea of how strong this is, it would take almost an hour to cut through a quarter of an inch with a diamond cutting wheel. To put this in perspective, another common metal used in joint replacement of the hip - titanium - would be cut in half in less than 30 seconds!
The space between the metal pieces is filled with a special polyethylene (plastic). The better products are made of what is called a cross-linked polyethylene. This gives the plastic superior wear characteristics. A review of one of the more modern plastics can be found here.
The quality of the metal and the plastics has led to increased lifespan of knee replacements. Knee replacements generally fail at a rate of 1% a year. That means in 15 years, close to 85% should still be around. Not bad.
Thanks to tremendous engineering research we have come a long way.
Dr. K.
*The excerpt above is Copyright 2006 by Ira H. Kirschenbaum, MD and used with permission.
Related Topics: Joint Replacement Surgery on the Rise, WebMD Video: Need New Knees? There's better metal in Joint Surgery
Technorati Tags: joint replacement, knee replacement
10 Comments:
What effects will a lateral release have when the knee cap will ride in a different spot? Is there increased or new pain? What percentage of paitents this has been done to and what is the final outcome?
Hi Anonymouse I had the Knee reconstructions when I was 16 and 17,and in 91 I was diagnosised with osteo and ra by 39 i had lost both kneecaps to the arthirists it had degenerated the patellas so that my dr could blow through them. now I have osteo and Ra all over my body along with lupus and I live with a daily battle of pain, what i am telling u is that the pain will come later on down the road.
My mother just had "another" knee replacement after the one she had done two years ago showed loose screws, etc on an MRI. Why did this happen? She has done great with this new one, but she had pain from day one with the first one, that lasted until they did this one.
Had bilat.knee repl. 3 months apart 1996. 10 yrs later the 1st had a loose screw & the plastic from the pad was sloffing off and causing osteolysis. Had surg. replaced the screw & pad and had bone grafts. 11 months 11/06 later the grafts are doing great. Note: within 3 months of having the original repl. the pad composition had changed. Products change everyday.
I have bilateral knee osteoarthritis and the recommendation if total knee replacements. I am scared because I have heard of too many cases where something went wrong or the patient ended up in worse shape than before. (I read this in a Web MD Conference). I have significant pain. My mother had similar situation and I am following her profile: NSAIDS provide no relief, cortisone shots no relief, Hyalgon injections no relief. Ortho MD suggested alternative techniques and pain clinic. I have started accupuncture no relief and massage that helps my fibromyalgia. I am 57. What would a pain clinic do and what other options have I overlooked? My doctor does not subscribe to a Minimally Invasive Surgery protocol except for some variations such as size of instruments.Should I get a surgeon who does? This doc did an arthroscopic torn meniscus repair and chondroplasty that seemed to really get the arthritis situation riled in both legs. What should I expect regarding planning prior to the TKR and after care and rehab. Thank you.
Celeste
i had bilateral knee replacement 2 years ago,in march of this year[2007] had a hip replacement, did great for a couple of months, since i have been off the walker, i now find i have extreme neck and back pain and my knees are numb and very painful, to the point where i cannot walk. why?
I have severe knee deterioration- bone on bone- but- my doc is hesitant to do the surgery because they use cement and I have COPD (bad lungs) and some of the cement dust is forced into the lungs- so It looks like I get the shot in the knee every 3 months from now- till forever.
You have my sympathy. I also am down to "bone on bone".Had arthroscopic on both knees, didn't help much but DR is also hesitant to replace them. I am the ONLY member of my family of 5 that has not had both knees replaced. I don't want to continue with cortisone shots as they are also detrimental. Agree?
I had total knee replacement in July 2005. I have to go for an MRI for back and leg pain. Would a MRI be right for me, or would it be the wrong thing to do
just had a lat release and the only pain that i have is post sugery
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