Implant Longevity

[stevel]

Danny,

Yes, running on a treadmill has less impact than running on a road.
But it has more impact than using a stairmaster or recombinant bicycle.
That's why I notice the loading when my left hip aches after running 30 minutes on the treadmill.

I haven't seen any reports of loosening of the femoral cap or acetabular cup due to effects of impact loads in the long term say for over 10 years.
Even though McMinn's study is a small sample size, the results are great at 14 years for patients doing impact sports with no loosenings of either component.

[obxpelican]

The cemented/uncemented question has yet to be fully answered.  Dr. Gross feels that the cement is the weak link in HRs.  Cemented implants have been around for a while now so the cement weak link has yet to be proven.

I tend to believe that uncemented implants will work out, but I tend feel that cemented implants will be fine in years to come, but only time will tell for both cemented and uncemented.

Chuck

[PistolPete]

My surgeon said that he would prefer to do uncemented because the cement is the weak-link. He said that he legally cannot do it uncemented because the FDA Approval requires the use of cement.  HE said he uses the absolute minimal amount of cement so it is "almost" cementless.  He said he does it so if the cement fails it won't really matter as your bone growth will secure the implant in place.  I guess time will tell.

[stevel]

The first BHR's were installed in 1997 and the precursor to the BHR was installed a couple years before that.
So we have at least 14 years of "in service" for a cemented device without cement failures yet.
Ironically, Dr. McMinn has reported 20 years of "in service" for an uncemented devices that were installed beginning in 1991, but the device had an unacceptable failure rate for all patients.
See "Longevity of hip resurfacing" on Vicky Marlow's website.

Dr. Gross believes he has perfected the uncemented device but only time will tell.
Let's hope that both the cemented and uncemented versions last a lifetime.

[Dannywayoflife]

That's right it's a theory with at the moment no evidence I could find to back it up.
Derrick mcminn has had zero loosening of the femoral components since he switched to cement.
There's evidence that cemented thrs don't last as long but the way the forces are transmitted are totally different.
Also after watching the mark Bloomfield interview on vickys site it gives an interesting insure to some people's mistrust of cement. He goes on to give a brief history lesson about how hip devices were developed and why they failed. Initially he said because the technollogy wasn't available to see the real problem( the wear debris) they blamed the cement for the loosening and osteolysis. Apparently American surgeons initially named this loosening cement disese.
It's a very very interesting interview and well worth a look. He's a top surgeon and has been doing hr's since the mid 90s so knows what he is on about!
Danny

[Tin Soldier]

I think we tried to calculate the mass of a BHR acetabular component and the amount of wear one would expect to see in a lifetime and I think we determined that if you wear the component at the expected wear rate, you would have 100 years or more? of material.  That was a fun thread.

BTW - the Mckee-Farrer group in England from the 70s (pre Modern HR) had at least one individual that had a MoM HR device for 40 years.  I don't remember what paper I saw that in, probably one of Pritchett's.  I think McMinn discusses that group and the longevity of old-school HRs in his book.   

[Dannywayoflife]

Tin, the Mckee-Farrer device was a thr device. I can't find a hr device by them. But I think you are correct they had a 40year survivorship. That's got to be a tick in favour for MoM HR devices!
Danny

[Tin Soldier]

I guess I thought it was HR, I must have been focusing on the MoM aspect.  Prichett's paper on metallosis discusses the McKee-Farrar arthroplasty and indeed it was THR.  So I guess from a MoM perspective, which is what a lot of the fuss is about with HR device longevity, I think the point is still good, in that CoCr rubbing on CoCr can last a very long time. 

Thanks Danny. 

[Dannywayoflife]

I defiantly consider it a plus for hr tho. As the thr device mentioned, still had the devilish stress shielding that causes most thr's to fail! But yet the baring lasted regularly over 20years and upto 40! Now also consider, I have a paper published by mcminn and Treacy that states tge consider the majority of that devices failiures to be down to manufacturing errors! Ie not finished smooth enough. That is not a problem with any modern day hr device. All of which are machined to exacting finish smoothness!
Also when you consider that a hr device replicates nature and transfers normal loading of tge proximal femour that's got to be good for it!? As we have proof that the alloy can last a really long time with less than ideal positioning and loading so a well positioned hr device should last a real real long time as it eliminates one of the main reasons for failure! Atleast that's the way I've interpriteted the evidence that I have seen!

[hernanu]

Some great info. The one about the 20 year anniversary is amazing. She's still going strong too - really makes me feel good going forward.

[Dannywayoflife]

I touched on the subject with Mr Treacy when I first had my consultation with him and he said they were fairly crude devices compared with the bhr that when to Market so like has been said before these devices well placed should last a long time!

[Dannywayoflife]

Surely tho when the new ceramic ceramic HR devices come out they will be an unknown tho as there will be no data on them for a long time so it could be a risk?