has anyone had a loosening of your TKR

[Josephine]

Well, bone cement doesn't 'stick' to anything because it's not an adhesive. It's a packing material that keys into the bone and provides a tight fit to the prosthesis, also keying into certain parts of that. The bone has to be adequately prepared which means flushing out all the blood and fat and drying the area thoroughly. Any tiny space that is occupied by water, blood or fat (bone marrow) will prevent bone cement going in there. This is referred to as cement security which is a skill. The vast majority of loosenings occur because the surgeon has not prepared the site properly or pressed the cement into the bone with enough force.

Almost all knee and hip prostheses have been around some years and number in the thousands. It would therefore be unrealistic to blame the prosthesis for this. TKRs should last around 20-25 years in the hands of a careful and suitably experienced surgeon. I would suggest that your knee would have become loose whatever implant that surgeon used because it wasn't the fault of the implants nor of the cement.

As a rule, loosening occures at the cement-bone interface because the bone hasn't been properly prepared. Therefore the cement sits on top of the tiny spicules of bone (see left image) on the inside (see right image) which eventually break down and die back due to the pressure and thereby cause loosening.

That the loosening was at the implant-cement interface means the implant was moved whilst the cement was hardening so the space that should have been a tight fit was opened up.

For your interest, bone cement comes to the table in an ampoule of fluid and a bag of powder which are mixed together when required which is to say when the trials have been tested, the real implants opened and ready for use and the operation site properly prepared. When mixing (which I've done a few thousand times in my life!) it first is very fluid like cream, then gets thicker until the mix takes on the consistency of warm plasticine. Now it is put into the bone and the implants hammered into place. At this juncture it is imperitive that the prostheses are not moved at all while the hardening continues. This takes about 8 minutes from adding the two materials together. Towards the last minute or so, the mix will suddenly go extremely hot and set like marble. Any distortion to the implants' place in the cement will be, to use a phrase, set in stone!

 

[Gringo]

Why not use screws instead of those things they hammer in? Wouldn't screws pull the metal bits hard up against the bone and hold them better than nails? Not second guessing, just curious.

 

[Josephine]

Well, unlike wood, bone has this habit of objecting to pressure being applied to it and when you tighten a screw into bone, the bone in the threads is put under pressure (at arrow points). So what happens is that the stressed bone dies back and everything gets loose!

Some hip cups are centred using a screw or two but the pressure of the bone on the screws is taken over by cement or the uncemented bone to metal bonding.

 

[Gringo]

Good info Jo, and very interesting. So... if I understand, bone basically dies and gets crumbly if you put pressure on it, or try to compress it?

What keeps the exposed bone under the prothesis from dying when you stand on it? Is that the cement acting like a cushion?

 

[Josephine]

Well, that's the 'cement security' I spoke about in this post. If the surgeon's done his job properly he will have pressed the cement into the bone so it encompasses the wee little spicules of bone. This a) spreads the load over a greater area and b) encompasses and supports them.

In a uncemented prothesis, the special coating on the metals encourages the bone to grow into the metal with much the same result.

 

[Linda2]

This is all so fascinating. Thanks for the lesson on cement--I really hadn't thought much about that before.

 

[tooyoungforthis]

Hi Everyone, I saw my pain doctor last week ,she is the one that order the xrays and she wanted to know if i saw my OS when i told her it takes 6-8 weeks to get in she said you dont want me to call because any doctor can see you sooner so when i got home i called the os again I told the lady that answer the phone what was going on and she sent my call to the doctor personal nurse and she did look up and told me that he is so busy that May 18 is the earlest date, so here i wait just me and this so called new soon to be old cement less knee. My pain doctor upped my fentanyl patch and my pain pills since my pain is getting very bad,I asked her a question and she didnt know the answer so i hope someone knows I have a tens machine i do use, am i hurting my knee or should i say the cement that is loose by useing the machine?
I wish everyone well until later, Peggy

 

[Jamie]

I don't think the TENS machine would not have any impact on the joint itself. Use it if it helps you. I think it is very strange that you can't be seen before May 18th. Doctors almost always have times they don't schedule appointments for in case of emergencies like yours. But if you talked to his nurse and still got nowhere, I guess you have to accept that. The only other alternative for you would be to try and find a second doctor to see instead. I'm so sorry you have to wait!!!

 

[Jamie]

Peggy, I just went back and read your original post. If this doctor you are seeing on May 18th is not a revision specialist, you really do need to find someone who is. Is he???

 

[tooyoungforthis]

Hi Jamie, I just lost the post that i wrote its out in space somewhere!! The doctor that i am waiting to see is a revision specialist that i didnt know at the time i made the appt.This doctor is in a group and his brother is a OS in the same building that i saw before.My husband told someone what was going on with me and he told him his wife had the same thing and the name of her doctor so i called and i could of got in to see him but he didnt take our insurance,thats my luck! Now i have been doing spring cleaning and keeping ice and the tens machine on when i start having too much pain.Can i be doing more damage to this poor leg? Thanks

 

[Jamie]

I would take it easy on the spring cleaning until you know what is going on. But ice and the TENS machine are no problem. You do need to do some exercise...out and about...walking, bike...something just to keep from sitting all the time. But depending on what you're doing...spring cleaning might be a bit much. Just be sure not to overdo it until you see the doc.

 

[aussie]

Very interesting description Jo. In my xrays the screws are very visible, both hip and knee. I just thought they used screws in all of them. You are just full of interesting facts.

Chris

 

[tooyoungforthis]

I am been doing some walking,I can make it up our block just not all the way around it,its a big block that brings too much pain.In the middle of the night when i get up because i hurt i go into the kitchen and hold onto the sink and do some exercises.I have a exercise bike and last week when i was on it my husband asked is it safe to be riding it with out asking the doctor, i didnt know is it safe? Today my sister called to ask if i can babysit my nephew tomorrow he is 15 months and on monday when he was in daycare he came down with a fever and they were in Mexico for easter week.He ened up in the ER for tests of the Swine Flu,and thank goodness its only a virus.Itold her that i am sorry that i couldnt babysit him as he is 18 pounds and just picking him up and carrying him would be too much on my knee.Its just not my knee as i have fibromyalgia and the other times i watched him i was o so sore and tired. Peggy

 

[Josephine]

My goodness! How thoughtless of her to even ask. Let me have her email and I'll soon put her right! (just kidding!)

Yes, it is safe for you to use the bike so long as you don't force yourself to do a full rotation if you find it too painful and/or difficult. And instead of doing exercises in the middle of the night - which won't ease your pain - why not take some pain meds and then apply some ice? Nights are supposed to be when you rest and recharge your batteries.

 

[Jamie]

Peggy, you were SO WISE to tell your sister you cannot be a babysitter for an active 15-month old boy!!! And one with a virus!!! What is your sister thinking???? You may have to do this again. It is a common problem for people who have not had joint replacement surgery to think you should be healed in a few weeks and completely back to normal. This is YOUR TIME to heal and get yourself back to normal. It will likely be months before you could deal with a toddler. Hang in there!!!

 

[tooyoungforthis]

Last night I had a hard time sleeping after hour and half i woke up in pain. Got my ice pack and back to sleep only to wake up 3 1/2 hours later.I couldnt take a pain pill yet so i made a cup of sleepytime herb tea and got another ice pack and this time i when out on the couch.It was 4am and dont you know that the birds outside started signing.This time of the year we get lots of birds in the back yard.I didnt get back to sleep.
I did notice that i am starting to swell up on the left side of my tibia about the size of a egg and some on top right side of the femur.I am keeping ice on it and since i am tired today i am not doing too much. What i cant understand is all this pain meds i am on why do i feel this pain? I am taking Norco pain pill every 6 hours i can take 1 more pill if need also i am on 50mg fentanyl patch that gets change every 2 days, gabapentin 2700mg a day,flexerl 10mg. I think i take enough and cant wait for the day i dont need all this,I think what are they going to put me on when this knee gets fix,I am very tired of all this pain.Just think only 17 more days until i see this new doctor!

 

[Jamie]

If you are in pain, take all the pills you are allowed to take. That is what they are for and you should take advantage of them when you hurt. God bless you, hon. You are in my prayers.

 

[Josephine]

Absolutely, Jamie! If there's more pills you are told you can take - why aren't you taking them? When I got home, my doctor increased the Tramadol from 100mgs to 150mgs per dose if I wanted though I didn't often have to take the 150. But I always took the Trams and the 2 paracetamol - still do. Even today I did.

 

[Texas]

Hi peggy I was wondering how you were doing. Did you ice up, and did the sweling go down at all. I hope so...The begining of you story is me to a tee. But I dont have any other problems but the knee. Put yea h I the begining da ja vue. Anyway I hope are feeling better. please let us know......

 

[tooyoungforthis]

Hi All, Yesturday i was so tired i did rest but didnt take a nap.So at 10pm i took a sleeping pill and when out like a light untill 12;30 when and got a ice pack back to bed and about 20 mintues i was sleeping until 4;30 this time my left hip was hurting so i said to myself it had to been the way i was laying on it. I took my pain pill but couldnt get back to sleep again back out into the living room I have a lounge chair( best thing we brought)this time 2 ice packs and on when the tv still didnt get back to sleep.I need to get a couple of things at the food store good thing i wrote down what i needed its hard to shop when you are tired and in pain. I just had a 2 hour nap and i forgot to put the ice pack on and i am in so much pain i need to wait a hour before i take a pill and tonight my patches get change.I hope i get a whole night sleep tonight.