Author Topic: Screws in Acetabular Cup? (Read 2697 times)

Luanna · « **on:** December 19, 2011, 07:09:51 PM »

Hi everyone,
As I'm preparing for my meeting with Dr. Pritchett on Wednesday (rechecking hip progress and xrays for back), I'm going over all the info that I have. In my surgical paperwork from Swedish Hospital I just came across a list of the items that he implanted. Among them are 2 cancellous screws Stryker brand so they must have been used on the titanium cup that houses the poly liner?

We never talked about the need for screws but I have congenital hip dysplasia so I'm guessing that is why he implanted them. Anyone ever hear of screws implanted into the bone to hold the cup? So now I realize that I have a titanium cup, poly liner, and cobalt and chromium femoral ball. Only missing ceramic.... I think.

Anyone knowing anything about screws used to attach the cup please share. Thanks.

Luanna

Dannywayoflife · « **Reply #1 on:** December 19, 2011, 07:25:02 PM »

I believe that it's fairly common in dysplasia cases to secure the cup with screws. Just look at any of the dysplasia resurfacing cups.
Danny

Aerial · « **Reply #2 on:** December 19, 2011, 08:00:11 PM »

Dr. Gross uses a cup with spikes that also provide security from slipping. I too have congenital dysplasia, however, on my operative report he didn't indicate a special cup was used. This is something I want to ask him about at my post op appointment. Good luck with your appointment.

Luanna · « **Reply #3 on:** December 19, 2011, 09:49:55 PM »

Danny and Aerial, it appears that my cup is not a special cup for dysplasia but it has 2 screws to secure it rather than spikes. Here's what I found on the Stryker site:

"Insertion of cancellous screws:
In some cases of cup instability... the spikes may be replaced by 6mm cancellous screws. A drill guide is provided for this purpose. The end of the guide can be screwed into the intended hole in the cup, using the hexagonal socket screwdriver. A drill bit of the required length is introduced into the guide, to drill the cancellous bone. The drill guide is removed. The screw length gauge allows the screw length to be determined; the screw itself is inserted with the hexagonal socket screwdriver. In order to prevent impingement, it is important to ensure that the screw, which is held in the cup with its double thread, is fully recessed in the cup. For cup fixation, one screw or several screws may be used."

Interesting what amazing things they can do. I'm impressed but I'm definitely screwed!!!

Luanna

curt · « **Reply #4 on:** December 20, 2011, 08:01:02 AM »

Luanna, is the cup also cemented or will the bone affix to it along with the screws? I don't think I would care too much anyway, as long as it lasts, but if it takes screws to keep it from moving, bring it!

Curt

Dannywayoflife · « **Reply #5 on:** December 20, 2011, 09:16:21 AM »

I believe that it will still be a cementless cup. I think the screws are used because in dysplasia the sockets are shallow and the screws help keep the cup in the correct position. I know that its something to do with the morphology of dysplasia.
Danny

Luanna · « **Reply #6 on:** December 20, 2011, 12:11:34 PM »

Good morning or afternoon depending on where you are!

Curt, I believe that it is not cemented because it has a fixation feature that helps the bone attach to it. The bone will affix to the device. In a way the screws make me feel like it will be harder for the cup to slip! That's kind of reassuring but i wish I knew that they were there before my 15 week mark. Probably too zonked out after surgery to remember what my doc told me. We had some good conversations....but I don't recall a one of them.

Danny, You are totally correct. The Smith and Nephew metal ball is the only implant that is cemented.

Hoping I'll find out more tomorrow at my doc appointment.
Luanna

Tin Soldier · « **Reply #7 on:** December 20, 2011, 02:36:39 PM »

Sounds like a standard dysplasia cup, like Danny was saying. Although you have a slightly different setup than most of us. I suspect you'll get a well-informed answer from Pritchett. Let us know how it goes.

Luanna · « **Reply #8 on:** December 25, 2011, 09:07:05 PM »

Hi Tin,
Well I did find out that I don't have a dysplasia cup. The screws go through holes inside the regular cup. You can see the holes in the trident acetabular cup at:
http://www.stryker.com/en-us/products/Orthopaedics/HipReplacement/PrimaryAcetabular/index.htm

According to Dr. P I have a regular cup with holes in it that supports spikes, screws or no extra support mechanisms - just bone growing into the mechanism. The poly liner goes on after the metal cup is in place. He does not always use screws but he did with me. He said that they were "not much really as screws go... only 25 mm". So, I have piddly screws. My appointment was right before their Christmas office party so he was in a hurry.

He said that we'll talk more after he gets the exact results of the MRI on my back. You know how he is....sometimes he talks and sometimes he walks... During this appointment he was totally focused on my back and setting up my MRI with the imaging folks.

Luanna

Dannywayoflife · « **Reply #9 on:** December 26, 2011, 01:17:09 PM »

I'm sure the screws will mainly aide primary fixation. I wonder though why cross linked Polly is the choice over ceramic for the liner?
I think in the future ceramic will be the material of choice for hr devices.

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