Author Topic: The 'mechanics' of THR  (Read 9896 times)

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Mike D

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The 'mechanics' of THR
« on: March 15, 2013, 07:54:51 PM »
Can anyone tell me why all THR surgery-as far as I know- involves a spike into the femur?
I know its the way its been done for many a decade, but why can't the femur part fit over the bone instead of going down the middle?
I thought about this before posting as it seems such a basic question and I assume there's a good reason for the way it's done but would it not be a more natural loading of pressure to not have the femur spike?
One of the main reasons on here for a preference to HR is  that its a much better 'loading' of the joint than THR, and I agree.
Would a type of sleeve, maybe screwed to the femur, with the large ceramic ball on top be a similar natural loading that the HR provides?

Any thoughts?
Mike
Right Ceramic THR
Ronan Treacy   Birmingham R.O.H
8 August 2012

Dannywayoflife

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Re: The 'mechanics' of THR
« Reply #1 on: March 16, 2013, 08:20:55 AM »
Not sure a sleeve would be possible mike I would have thought things attach to the bone like muscles and circulation.
I think the main problem with thr is the differing harmonics between the bone and the stem. If they can make the stem from a material with the same flex etc as the natural bone I think there onto a winner.
On that subject I know they have been experimenting with carbon fibre (not very well so far due to poor bone ingrowth if memory serves).
Train hard fight easy
LBHR 10/11/2011 Mr Ronan Treacy Birmingham England
60mm cup 54mm head
Rbhr 54mm head 60mm cup 12/02/15 Ronan Treacy ROH Birmingham England
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evant

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Re: The 'mechanics' of THR
« Reply #2 on: March 16, 2013, 09:19:10 AM »
I can see the way you're thinking Mike.

It doesn't seem logical to destroy so much of the femur.

And it would be a less scary option to consider for all of us (however I do see that there are some really encouraging THR guys out there doing as much as HR guys).

As Danny mentions it looks like some research has been taking place.

Maybe a medical engineering person on this site can add something further.
rbhr 3 january 2013
mr ronan treacy
royal orthopaedic hospital, birmingham, england

B.I.L.L.

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Re: The 'mechanics' of THR
« Reply #3 on: May 30, 2013, 05:52:52 AM »
Yeah it seems sketchy, especially with a longer stem. I just posted my friends x-ray in the motorcycle section. He just broke his femur around his 2nd thr, not good. Wonder if someday they'll have the technology to replace the whole femur with one that has a ball for the hip on one end and what ever they use for a knee replacement on the other ? Does the bone "have" to have blood flow ? I've been doing thr research since I'm on deck for one soon. What happened to my friend is my worst nightmare  :(

evant

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Re: The 'mechanics' of THR
« Reply #4 on: May 30, 2013, 07:55:50 AM »
The whole femur replacement sounds good - just not in our lifetime unfortunately - I would love to be proved wrong of course.

I know you've battled valiantly with your BHR B.I.L.L. so I really wish you well for your forthcoming THR.
rbhr 3 january 2013
mr ronan treacy
royal orthopaedic hospital, birmingham, england

B.I.L.L.

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Re: The 'mechanics' of THR
« Reply #5 on: May 30, 2013, 03:16:45 PM »
The whole femur replacement sounds good - just not in our lifetime unfortunately - I would love to be proved wrong of course.

I know you've battled valiantly with your BHR B.I.L.L. so I really wish you well for your forthcoming THR.

I REALY wish I could keep the bhr, I think it's better in every way shape and form. But obviously they have to be set correctly. I haven't been posting alot but look in here almost daily. If I read about someone who is going to use an inexperienced doctor cause "they like him or think he'll do a good job" I'm gonna blast them out of the water and tell them don't even think about it !! :). I have Kaiser insurance so I have to use someone in their system. Last thursday I drove 8 hours to go see Dr. Klug in Roseville for an appointment on friday. Really liked him and he will be doing my thr. Titanium parts with a ceramic coated ball in a polyethelene liner, and a relatively short stem (by thr standards) He also said the ceramic head and plastic liner can be swapped out without ripping the metal parts out of the bone (if it were to wear prematurely, and the bone ingrowth metal parts were still solid of course) Traveling is the least of my worries if it means going to a more experienced Dr. Wish I knew what I know now about 5 years ago, 16 hours in the car vs what I've been dealing with ? Hahahahaha that's truly a no brainer !  8) As always thanks for the encouragement, this is an awesome community, you guys rock  8)   

Dannywayoflife

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Re: The 'mechanics' of THR
« Reply #6 on: May 30, 2013, 03:22:14 PM »
Bill I really hope your thr goes better than your bhr. Your soooooo right that surgeon selection is THE MOST IMPORTANT FACTOR. I'm sure you'll bounce back from your thr your obviously very determined.

All the best

Danny
Train hard fight easy
LBHR 10/11/2011 Mr Ronan Treacy Birmingham England
60mm cup 54mm head
Rbhr 54mm head 60mm cup 12/02/15 Ronan Treacy ROH Birmingham England
;)

hernanu

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Re: The 'mechanics' of THR
« Reply #7 on: May 30, 2013, 03:50:16 PM »
The whole femur replacement sounds good - just not in our lifetime unfortunately - I would love to be proved wrong of course.

I know you've battled valiantly with your BHR B.I.L.L. so I really wish you well for your forthcoming THR.

I REALY wish I could keep the bhr, I think it's better in every way shape and form. But obviously they have to be set correctly. I haven't been posting alot but look in here almost daily. If I read about someone who is going to use an inexperienced doctor cause "they like him or think he'll do a good job" I'm gonna blast them out of the water and tell them don't even think about it !! :). I have Kaiser insurance so I have to use someone in their system. Last thursday I drove 8 hours to go see Dr. Klug in Roseville for an appointment on friday. Really liked him and he will be doing my thr. Titanium parts with a ceramic coated ball in a polyethelene liner, and a relatively short stem (by thr standards) He also said the ceramic head and plastic liner can be swapped out without ripping the metal parts out of the bone (if it were to wear prematurely, and the bone ingrowth metal parts were still solid of course) Traveling is the least of my worries if it means going to a more experienced Dr. Wish I knew what I know now about 5 years ago, 16 hours in the car vs what I've been dealing with ? Hahahahaha that's truly a no brainer !  8) As always thanks for the encouragement, this is an awesome community, you guys rock  8)

Sounds like a good plan for a regrettable situation, Bill. The shorter the stem, as long as it's stable, the better (I think). You've been an active athlete for a long time, so your bone density must be in good shape so hopefully bone ingrowth is solid for you.

I agree - a longer trip to ensure a very good outcome is a very good trade off. I'm glad you got a good one.
Hernan, LHR 8/24/2010, RHR 11/29/2010 - Cormet, Dr. Snyder

denisesuemann

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Re: The 'mechanics' of THR
« Reply #8 on: August 31, 2013, 11:23:54 PM »
B.I.L.L. - , I have also seen Dr. Klug about my "failing" BHR - (my x-ray makes people cringe). Do you know if he is planning to use bone cement in the femoral component? I'm a little older than you (58) and am afraid my metabolism will destroy the cement by the time I'm 72, and my genes put me at 100+ longevity-wise. Personally, I am holding out for an uncemented revision.

I have read of your trials and tribulations and my heart goes out to you, dear. Bon courage!

Pat Walter

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Re: The 'mechanics' of THR
« Reply #9 on: September 01, 2013, 01:51:10 PM »
BILL

Good Luck with your revision.  I am sorry you have to go thru a second surgery, but hopefully this will be the final solution.

Denise - I am also sorry to hear about your required revision.  Dr. Klug is an excellent surgeon and I am sure he will do well for both you and Bill.

Uncemented femur stem for THRs is often used, especially for younger people.  The cement is not what holds the device in place - it is your own bone growth.  The cement remains until the bone can grow. That is why people have to wait 6 months before they begin being really active.  It is usually your own bone growth that has failed when components become loose.  Many have special coatings and designs to encourage good bone growth.

Please keep in touch when you can.

Pat
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3/15/06 LBHR De Smet

denisesuemann

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Re: The 'mechanics' of THR
« Reply #10 on: September 01, 2013, 05:51:46 PM »
Sorry, Pat, no plan (or failure yet) for BHR. Will be hearing back from Kusuma and Su, as cup was determined to be malpositioned but migrated femoral component presently stable. Thanks for all your help.

                                                                             denise
                                 

John C

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Re: The 'mechanics' of THR
« Reply #11 on: September 01, 2013, 07:41:45 PM »
Pat,
I really respect your expertise, especially after all the interviews and surgeons conferences that you have attended. Your post about cement and bone ingrowth left me confused. I was always under the impression that it was an either/or situation: either you had a cementless prosthesis with a textured metal surface, often with a bone stimulating coating, that the bone was intended to grow into; or you had a cemented design in which there was a layer of cement in between the bone and the metal to hold them together, often with some penetration of the cement into the bone surface during installation. What confused me was when you said "The cement remains until the bone can grow." I always thought that the cement was intended to remain forever at the interface as the bonding agent, and that therefore there could be no bone ingrowth into a cemented prosthesis. (There is an absorbable bone cement intended to allow gradual bone ingrowth, but I thought that it is still only experimental in animal models). The bone cannot grow into the cement since there is little or no porosity, and with the cement in between, it cannot reach the metal to grow into that. When you have a moment, would you clarify this? ( I do understand that there are "hybrid" designs where one component such as the cup is cementless, and one component such as the femoral stem or cap is cemented, so I don't think that is where I am confused.)
John/ Left uncemented Biomet/ Dr Gross/ 6-16-08
Right uncemented Biomet/Dr Gross/ 4/25/18

Pat Walter

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Re: The 'mechanics' of THR
« Reply #12 on: September 01, 2013, 08:10:32 PM »
Hi John

I am sorry, but I meant the cement remains holding the device in place until the bone growth occurs.  The cement remains and does not become absorbed.

With a resurfacing, the cement in the femur cap is only inside the cap, not on the stem. The bone growth also occurs inside the cap.  I have photos of studies where they cut the cap in half to see how much bone growth has occurred.  I will look them up. 

Didn't mean to confuse you.
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John C

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Re: The 'mechanics' of THR
« Reply #13 on: September 02, 2013, 09:41:51 PM »
Thanks Pat. It would be fun to see those photos if you find them.
John/ Left uncemented Biomet/ Dr Gross/ 6-16-08
Right uncemented Biomet/Dr Gross/ 4/25/18