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Author Topic: Some Random Thoughts on the Life of a Resurfacing  (Read 4984 times)

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stephen1254

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Some Random Thoughts on the Life of a Resurfacing
« on: September 08, 2012, 05:06:26 PM »
A question was posted in another area about weight lifting - particularly squatting - after a resurfacing. This got me thinking about stuff.

I'm not a doctor - nor do I play one on TV - but I've read general comments about the life of a resurfacing being 15 years or so. Why does it wear out?

When you look at the design of the natural hip it would appear that the femoral neck is in shear, as it sits at an angle to the socket in the pelvis. Logic would dictate, however, that it is primarily in compression - otherwise it's a bad design that evolution would have weeded out. It would seem logical that the loads on the femur would be primarily distributed throughout the hip socket, and not overly loaded at any one point.

This would also seem to be borne out by the emphasis in resurfacing at getting the cup angle "just right." A cup at the wrong angle puts localized load on one portion of the cup leading to premature wear. This would indicate that a cup placed at the right angle distributes the load on the cup more evenly, reducing localized wear. That would also indicate to me that the loads on a resurfacing implant are primarily compressive, and that the load on the femoral neck is primarily compressive, otherwise you would always be edge loading some part of the implant.

The only thing that would cause a resurfacing to need replacing would therefore be excessive wear, and likely all over the implant and not particularly localized. I guess. Maybe I'm wrong about that.

So what would cause excessive wear? If you look at three different exercises - biking, running, and squatting, what causes the most wear? In cycling the load is relatively light but there is a lot of repetitive motion. In running you have the repeated impact on the implant - momentary high loading. In squatting you have a heavy load but little impact, and for very short duration - maybe 3 to 20 repetitions.

Logic again would indicate to me that running would cause the most wear. It's going to take a certain amount of load before the force exceeds the strength of the metal, and I doubt cycling imparts really any more load than walking. Squatting imparts a heavier load but it is of short duration and I don't know that the load from squatting would be greater than the load from the impact of running. The impact of running may impart the greatest load of all, but does that load exceed the strength of the implant? Does a heavily padded running shoe, like the Hoka One One, reduce those loads in the same way a SAFER barrier reduces the localized load in an accident at a race track?

I don't know the answer to any of this, but maybe it will spark a discussion..... 
RBHR Dr. Callander 3/27/12

Dannywayoflife

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Re: Some Random Thoughts on the Life of a Resurfacing
« Reply #1 on: September 08, 2012, 05:19:04 PM »
The longevity of resurfacings is at the moment an unknown. The BHR has been out for just over 15 years and in the developers hands I believe has a retention rate of around 98% across the board. The predecessors to the BHR don't have the retention rate that the BHR does but some of those have now lasted 20+ years and are still in situ.
The key factor I believe is how long the devices will stay attached to the bone. The alloy the BHR is made from will never realistically wear enough that the device won't work. There are numerous THR's that was made from the same as cast alloy that are still in situ afte well over 40 years! The cup design of the BHR is unique as it has the porocast beads which create a really rough surface for the bone to weld to. You are totally correct that the positioning of the device is a huge factor! If the surgeon puts it in wrong it won't do well in the longrun.
Danny
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LBHR 10/11/2011 Mr Ronan Treacy Birmingham England
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Rbhr 54mm head 60mm cup 12/02/15 Ronan Treacy ROH Birmingham England
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Pat Walter

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Re: Some Random Thoughts on the Life of a Resurfacing
« Reply #2 on: September 08, 2012, 07:07:47 PM »
Good discussion.  Doctors have told me that if your bone density is not very good, it will increase with a hip resurfacing if the patient starts to walk and be active.  Weight bearing activities increase bone density.  The hip components really are depended on bone growth to keep them in place.  So I am guessing there is some line between good weight bearing activities and those that continue to jar the heck out of the joint and device.  Again, no one knows for sure about all of this.  Even among runners, some people might have different styles and ways of placing the feet as the run to make a difference between the impact the joint receives.  Not an easy thing to probably try to test, even thought they do a lot of medical testing.

I think if we all have our components placed properly and make sure we do some walking and weight bearing activities, we have the best shot at taking our hip resurfacings with us to the grave.  And they say you can't take it with you!  LOL    :o
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Dannywayoflife

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Re: Some Random Thoughts on the Life of a Resurfacing
« Reply #3 on: September 08, 2012, 07:40:07 PM »
I'm sure your right pat bone quality and density will be the over riding key to longevity. I personally think that I'll one day have a revision but if mine lasts me 30 years I'll be ecstatic! 
Train hard fight easy
LBHR 10/11/2011 Mr Ronan Treacy Birmingham England
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Rbhr 54mm head 60mm cup 12/02/15 Ronan Treacy ROH Birmingham England
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Mike D

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Re: Some Random Thoughts on the Life of a Resurfacing
« Reply #4 on: September 08, 2012, 07:57:21 PM »
Thats my outlook as well Danny, although I'd be ecstatic at anything beyond 20 yrs.
The way hip surgery has moved in recent years, we may all have little to worry about that far down the line.
Hopefully, the revisions will be more of a straightforward operation. My aim is to treat my THR with respect but not have it hold me back and see what the future brings.
All thanks to this site, I might add.
Right Ceramic THR
Ronan Treacy   Birmingham R.O.H
8 August 2012

Dannywayoflife

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Re: Some Random Thoughts on the Life of a Resurfacing
« Reply #5 on: September 08, 2012, 08:16:43 PM »
Mr T wouldn't commit to a lifespan of the BHR when I questioned him on it he did however he did say that his 15 year stats were in the very high 90s and that they wouldn't just go from that to zero over night. He predicted that his 20 year stats will be almost the same as his 15 year stats. So I guess that's as close as you'll get to a UK surgeon saying these will really last a long time!
And mike as I've said to Anna there's numerous THR's still in situ after 40+ years. So touch wood yours will out last you mike!  ;)
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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rubyred

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Re: Some Random Thoughts on the Life of a Resurfacing
« Reply #6 on: September 08, 2012, 08:19:43 PM »
I've said this to several people close to me, if my BHR only gives me 5 years, then that's 5 years of a decent standard of living. I had zero life before. Anything more than that is a bonus.
LBHR - 9th August 2012 - Mr R. Treacy

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Dannywayoflife

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Re: Some Random Thoughts on the Life of a Resurfacing
« Reply #7 on: September 08, 2012, 08:31:47 PM »
Very true ruby but personally I wouldn't want to go under the knife for round 2 after 5 years! I'll be amazed if either of ours don't do atleast 20 years.
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
;)

rubyred

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Re: Some Random Thoughts on the Life of a Resurfacing
« Reply #8 on: September 08, 2012, 08:38:43 PM »
I obviously expect it to last a hell of a lot longer, as does Mr T, however I was that grateful that 5 years would do LOL.
LBHR - 9th August 2012 - Mr R. Treacy

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obxpelican

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Re: Some Random Thoughts on the Life of a Resurfacing
« Reply #9 on: September 08, 2012, 11:21:14 PM »
OK, call me the ultimate optimistic guy but if you've ever held one of the devices you would be hard pressed to think it would wear out easily, the implants are designed to ride on a thin layer of synovial fluid produced by your body so wear would be greatly minimized, even if it did you have a lot of very strong metal.

Adhesion issues between the femoral component and the femur is one thing that will likely cause a failure, maybe, this has not shown it's ugly head. Once the cup is set properly bone growth will hold up for a very long time.

Everyday that goes by the more I am optimistic that our implants for the majority will last a lifetime and there is nothing that says differently, most times when you do have a failure it's happened in the first couple years.

I personally think the pounding from running could cause failure over the long term.

Of course this is IMHO.


Chuck
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8-6-08

Baby Barista

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Re: Some Random Thoughts on the Life of a Resurfacing
« Reply #10 on: September 09, 2012, 02:50:16 AM »
I'm not entirely sure what we're talking about here.

Are we talking about wearing out the BHR prosthetic bearing?
Or, are we talking about the longevity of the hip surface replacement as a whole?

It's an important distinction, because each has a different answer. It would be impossible for a human to "wear out" a BHR prosthetic bearing. We would have to live for hundreds of years for that to happen. The laws of metallurgy and physics dictate this.

Answering the other question is near impossible, because so many factors dictate the life of a hip surface replacement. Surgical technique, recovery, activity level, bone density, weight, health, diet, flexibility, metal allergies, accidents, cell turnover, vascularity, bone resorption, bone cement longevity... and probably a lot of things no one has figured out just yet.

I just had my six month with Dr. Pritchett yesterday. He says the best any doctor can tell anyone at this point, is what he told me: "This hip should last you a long time." Vague, but realistic.

I have an uncle who had a heart transplant at Stanford in 1990. Doctors gave him another 10 years at the most. He's still alive today and still one of the most cantankerous bastards I know.

If my hip gives me as long as his heart... I'll be happy.
LBHR Pritchett 01/23/12 - 52mm head, 58mm cup
RBHR Pritchett 12/10/12 - 52mm head, 58mm cup

Mike D

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Re: Some Random Thoughts on the Life of a Resurfacing
« Reply #11 on: September 09, 2012, 12:13:51 PM »
Is a THR designed to work in the same way regarding synovial fluid lubricating the joint, or is that not a possibility with no femoral head?
Right Ceramic THR
Ronan Treacy   Birmingham R.O.H
8 August 2012

Dannywayoflife

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Re: Some Random Thoughts on the Life of a Resurfacing
« Reply #12 on: September 09, 2012, 12:33:44 PM »
I think that would depend on the THR mike ask Mr T next rime you see him.
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
;)

obxpelican

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Re: Some Random Thoughts on the Life of a Resurfacing
« Reply #13 on: September 09, 2012, 12:37:01 PM »
I was referring to the overall life.

Adhesion is what will cause long term issues, Dr. Gross thinks that the cement will be the weak link in all of this but then again that has not shown to be the weak link.  The more time goes on like I said the more I think we'll die with our implants walking straight lines.   In the past failures were many times the results of the break down of the bearing surfaces.

You make a great point that how the device is implanted will determine the future, but more than often poor surgical technique shows up within the first 3 years, this is why the 4 year point is key.

Back in 2008 Dr. Gross was of the opinion that the possibility of long term survival of implants was more than likely.

Chuck


I'm not entirely sure what we're talking about here.

Are we talking about wearing out the BHR prosthetic bearing?
Or, are we talking about the longevity of the hip surface replacement as a whole?

It's an important distinction, because each has a different answer. It would be impossible for a human to "wear out" a BHR prosthetic bearing. We would have to live for hundreds of years for that to happen. The laws of metallurgy and physics dictate this.

Answering the other question is near impossible, because so many factors dictate the life of a hip surface replacement. Surgical technique, recovery, activity level, bone density, weight, health, diet, flexibility, metal allergies, accidents, cell turnover, vascularity, bone resorption, bone cement longevity... and probably a lot of things no one has figured out just yet.

I just had my six month with Dr. Pritchett yesterday. He says the best any doctor can tell anyone at this point, is what he told me: "This hip should last you a long time." Vague, but realistic.

I have an uncle who had a heart transplant at Stanford in 1990. Doctors gave him another 10 years at the most. He's still alive today and still one of the most cantankerous bastards I know.

If my hip gives me as long as his heart... I'll be happy.
Chuck
RH/Biomet U/C Dr. Gross/Lee Webb
8-6-08

Dannywayoflife

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Re: Some Random Thoughts on the Life of a Resurfacing
« Reply #14 on: September 09, 2012, 12:39:41 PM »
Chuck I truly pray that we can all take our HR's to the grave! As everyone stresses on here all the time surgeon technique is THE most important factor!
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
;)

stephen1254

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Re: Some Random Thoughts on the Life of a Resurfacing
« Reply #15 on: September 09, 2012, 02:56:34 PM »
I'm not entirely sure what we're talking about here.

Are we talking about wearing out the BHR prosthetic bearing?
Or, are we talking about the longevity of the hip surface replacement as a whole?

It's an important distinction, because each has a different answer. It would be impossible for a human to "wear out" a BHR prosthetic bearing. We would have to live for hundreds of years for that to happen. The laws of metallurgy and physics dictate this.

Answering the other question is near impossible, because so many factors dictate the life of a hip surface replacement. Surgical technique, recovery, activity level, bone density, weight, health, diet, flexibility, metal allergies, accidents, cell turnover, vascularity, bone resorption, bone cement longevity... and probably a lot of things no one has figured out just yet.

I just had my six month with Dr. Pritchett yesterday. He says the best any doctor can tell anyone at this point, is what he told me: "This hip should last you a long time." Vague, but realistic.

I have an uncle who had a heart transplant at Stanford in 1990. Doctors gave him another 10 years at the most. He's still alive today and still one of the most cantankerous bastards I know.

If my hip gives me as long as his heart... I'll be happy.


And this is actually what I was getting at. I liken the BHR device as functioning like an engine crankshaft bearing, with the synovial fluid acting like the engine oil. With an adequate number of main bearings supporting the crankshaft there will be essentially no wear to the bearing surfaces. I wonder if the loads placed on the hip from activity cause wear - if the synovial fluid is compressed to the point where you have metal to metal contact, or if failure would come from a skeletal problem - the cup or the cap loosening over time. I would think the skeletal bond would become greater over time and not less.

These thoughts came about because of a post on another topic where a doctor recommended against heavy squats after a resurfacing. I'm trying to figure out why - other than just taking a conservative approach. I can recall Kirk M. posting some time ago that he knew of a resurfacing patient that snapped of the end of the femur doing leg presses. I'm trying to understand why that would happen - if it would be because leg presses (or squats) place the femoral neck in shear instead of compression. It would seem more likely in that case that the femoral neck had not fully healed. Is there an issue after the femoral neck has fully healed?

I'm not a powerlifter and I'm not going to be doing 400 pound squats like Buster, but I cannot ever recall reading that powerlifting resulted in a structural failure - like a femoral neck snapping - in a natural hip. Powerlifters have muscle and tendon issues, and often skeletal issues in the spine, but I've never heard of a skeletal issue in the hip. Is the concern then that heavy squatting - or running - would cause the implant to move, or to wear?
RBHR Dr. Callander 3/27/12

Dannywayoflife

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Re: Some Random Thoughts on the Life of a Resurfacing
« Reply #16 on: September 09, 2012, 09:30:15 PM »
I think even if all the synovial fluid was pushed out of the gap the vitalium alloy is soooooo incredibly resistant to wear that it wouldn't really do much. The fluid would be sucked back in pretty quickly when whatever the activity was ceased.
I really doubt that the femoral neck would fracture once fully healed. But be mindful that it takes 12 months for the bone density to "normalise".
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
;)

obxpelican

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Re: Some Random Thoughts on the Life of a Resurfacing
« Reply #17 on: September 10, 2012, 12:54:33 AM »
Even if you had a situation where some of the synovial fluid was thin or non existent the surfaces are polished to the point where you can spin the femoral component in the cup and it spins and spins like crazy, and that is without any lubricant.   The day before surgery Dr. G handed us the device and we had a good old time spinning it like a top.

As Danny has said, getting the right angles is so very important for the long term survival of the device.  If you get Treacy or McMinn as your surgeon your chances of long term survivorship jumps, you would be hard pressed to find a failure of his on this forum, go ahead and do a search, we might have one from each, what do you say Pat?????



Chuck

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8-6-08

morph

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Re: Some Random Thoughts on the Life of a Resurfacing
« Reply #18 on: September 10, 2012, 08:57:01 AM »
Have the Synovial fluid pushed out under load is something I have thought about quite a lot. The same argument surely would apply to a natural joint, although cartiallage is way more slippery than anything else, about 10 times more slippery than black ice! The metal/metal surface, although very smooth, nowhere near natural cartiallage. Never the less with proper placement the combination of the Synovial and smoothness is obviously good enough for a long time. Also Synovial fluid is not like water, it is very viscous with a similar consitency to egg yolk so naturally with heavy load it should still be a good lubricant.

As for shear stress during squatting, the cap is precisely moulded to be a tight fit in all directions, having said that it is still an interface with two different materials so must probably is the weakest point, but how resilient is a good question. I wonder if there are any in lab tests fo this type of force. In my mind the only weak point would be if you tried to pull it off. So I would have thought that once the bone has healed and reshaped to it's new stress loading it would be fairly resilient. I still think that it is best to err on the cautious side when doing really deep heavy repetitive squats in case over time it worked lose. Just my thoughts.
LBHR - 58mm ball, 64mm cup
7th June 2012 - Mr J P Holland - Newcastle

stephen1254

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Re: Some Random Thoughts on the Life of a Resurfacing
« Reply #19 on: September 10, 2012, 02:04:22 PM »
I remember Rick Rubio posting that he was having a revision done to the cup after 5 years. Rick began running right after the resurfacing, and was running 5 miles at one month. The cup loosened up and apparently little or no bone grew into it. In that case, however, it seems likely that the impact of running was causing very slight movement in the cup from the beginning preventing bone growth, kind of like picking at a scab prevents it from ever healing. I would think after 6 months to a year of bone growth into the cup that wouldn't be an issue.

So here is a question. Does anyone know if a bone, say a thigh bone, flexes at all during activity, or is it completely rigid? I would bet a bone does have a tiny amount of give, and that give is reduced in the femoral neck area by the insertion of the metal pin in the center of the bone.
RBHR Dr. Callander 3/27/12

 

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