New Revision questions

[AOC]

After receiving a THR in 1986, I was just told that the lining is wearing out and I will need a revision within the next few months. I'm now 55 and plan on staying active for a long time to come. I'm researching all the new materials and products but was looking for some input from people that have already been through this before. The stem and ball are metal; the socket is metal with an older polyethylene liner. The liner seems stable but was screwed, which fell out of favor within a few years. I've only had a short conversataion with my surgeon but one possibility he mentioned was glueing a new cup into the old one. My doctor told me he needs to determine the brand of prosthesis to see what he can do with the existing ball and socket. Anyone out there been through this before that can share some information?

 

[Josephine]

I take it you don't know the name of your present prosthesis? Could be a Stryker or a Stanmore.

I actually know of very few replacements that are not in production now and I believe the one you describe is still in regular use in the UK!

I'm not sure I'd be happy with a make-do and mend job such as he seems to be suggesting. If the liner is a click-fit into a cementless metal cup, then cementing in a 'foreign' liner would not be something I would go for. However, the dimensions of the heads of all the prostheses are standard and so it wouldn't be an impossible task. But one has to wonder at the longevity of it. The bone cement is a not a 'glue'. It has to key into whatever it is fixed to.

In the femoral shaft, the cement is forced into the myriad little cavities in the bone to provide a firm foundation for the stem. In the cup, it's pretty much the same. You can see what I mean in this illustration

However, using it to fix a liner into a metal cup would not, IMO, give the same security and that is something I would discuss with him in detail if I were you. You want assurances what he is going to use to 'glue' it in and a guarantee that it is going to have a long lasting result. He'll not be able to give you such but I think his response might be revealing!

Ultimately, were someone to put in the effort, I'm sure they could find a new liner for you. That's why those hips were designed that way, so the liner could be changed when it was worn. Most reps would be able to identify it from the xrays if he couldn't. I know I always could when I was working! But whatever, please don't settle for that compromise.

 

[AOC]

My medical records were archived but I was able to locate them and should have the details in few days. The cup appears to have a spiral of fins that anchor the cup into the pelivs. There are two screws that were added ostensibly to make the unit more secure. The liner screws into the cup. I remember the surgeon telling me he had a lot of difficulty getting it to thread due to the close tolerace. He put it in the freezer for a time to get it to contaract just a hair so it was easier to thread. The screws have given me some minor trouble over the years, which is probably why they don't use them anymore. I was hoping that they had a replacement cup but he didn't think that was the case. I would think that a manufacturer would be able to machine a liner if it was necessary. I was also hoping for something more durable such as the cross linked polyethylene since I really don't want to do this again. I had a bone density scan and all the bone was nice and dense so that's not a problem. Thanks for the input. I'm dealing with John's Hopkins orthopedics so I don't think they will do anything shoddy, especially if I have anthing to do with it. If I read you correctly, a new liner is a possibility. Any idea on recovery and function after a second revision?

 

[Josephine]

Ah, but the screw anchored cups are still in use! That was my point. I can't recognise the prosthesis from your description but one or two possibilities spring to mind. I wish I could offer to find out what they are called and who makes them but I'm afraid I'm not in the position to do that anymore.

Prostheses cannot be made on a one-off. The machinery to produce them only works on a mass production style of output and the head of the stem and the interior of the liner has to be machined within a microns to ensure the accurate fit.

Still, whatever the problems you are having now, 23 years is not a bad life span for a THR.

And John Hopkins, huh? Can't beat the best! Do let us know what transpires.

 

[AOC]

I'll let you know the model as soon as I get my records out of the archives. I still have a lot of homework to do but thankfully I still have some time. This site is a wonderful source for information. When I had my first THR I was at the mercy of the physicians that worked on me. Fortunately, I picked a talanted doctor and he did a wonderful job. As you said in another post, the physican is probably the most important link in the chain. Thanks for your help and I'll talk to you soon.