Can you give me your input on the ASR device being discontinued and the NY Times article “With Warning, a Hip Device Is Withdrawn ”

Update reply from Dr. Vijay Bose on July 17, 2011

"Hi Vicky,
You had written to me earlier asking for my current thoughts on the ASR failure and recall.
 
The following is the mail that I sent to one of my patients which explains my current thoughts on the ASR .
 
This ASR Recall and unexpectedly high failure rate has caused tremendous confusion for everyone concerned.
Advisories from surgeons, govt bodies and the company are changing by the day.

We are certainly not seeing the failure rate of Tony's group from stockton on Tees in England.
Of the 300 + ASRs that I have installed , I have revised only  one personally. One of course  has to give an allowance for someone getting it revised elsewhere.

However in private practice in India , it is very unlikely that the patient will not return if there is a problem.
Fortunately as I used  the ASR exclusively in small boned patients, most patients are local with only a handful of overseas patients
There are 3 other patients having symptoms and or in the process of evaluation and probably will need revision.
The failure rate is nowhere near the rate quoted from England.

During my recent trip to south Africa to do some lectures, many surgeons reported a similar experience ( ie failure rate of less than 5%). There are surgeons there who have done more than 400 and seen very few failures.
I discussed this apparent disconnect with tony in one of the meetings and we could not come up with an explanation.
Luckily I have done only a handful of ASR large head THRs.

I have completely discontinued to do any more large head  MoM THR  of any make ( especially since the advent of the deltamotion where the same advantages can be given and eliminating the risk.)
As for monitoring the ASR patients there have been roadblocks.
I started to get patients gradually for monitoring ion levels.
For some reason the labs here give astonishingly different values for two consecutive specimens taken one week apart from the same patient.

I am in the process of helping to standardise  the testing and reporting locally here in India. Currently the most reliable one for picking up ALTR would be the imaging which I do  on all symptomatic patients.
I am also having many interactions with depuy at various levels to formulate an 'action plan' for India for not only my patients but the 3000+ patients who have had the ASR devise in India.

I also feel that asymptomatic ALTR is very very rare. A simple fluid collection of bursitis will cause pain and to think this rapid accelerated changes will be asymptomatic is unrealistic.
 
The vidoes from Nargol and Langton are most alarming .  Nevertheless ,It is important to keep in mind that knee jerk reactions in panic mode would be a disaster regarding this pseudotumour issue. . In one instance in the video they say all metal on metal is at risk. I would put the total MoM implants ( if one includes the zimmer 28 mms heads ) to be atleast 400,000 patients world wide. We now know that any THR of any bearing type  with high inclination angle of the  cup can cause a pseudotumour. This would put easily put tens of millions of patients worldwide at risk.  The MRI also has its limitations. David Young  a good friend of mine who specialises in doing hip arthroscopy after THR / resurfacing  feels that all hips of whatever type ( if symptomatic - as he scopes only symptomatic patients)  will have some kind of fluid collection .  Therefore the MRI is likely to pick up some fluid in all types of hip arthroplasities making it again difficult to interpret.  In the current scenario I would not be surprised if somebody calls for a ban on all hip implant surgeries.

Thus  , I would think that one has to exercise some caution in the interpretation.
 
We are currently sure only of the following facts.
1.The ASR and durom have much higher failure rates than the BHR and conserve plus due the low clearance concept of these devices.( It does not mean that all ASR and Durom will fail).  Low clearances works well in the lab. However if this is adopted in surgery, the clearance of the bearing  used for some patients  may fall below min required causing clamping and failure. This occurs when the implant had a clearance in the lower range of the bell curve of manufacturing tolerances and /or  cup deformation occurred during implantation. Thus , Patients who have had an ASR implant with a larger clearance of the bell curve scatter and in whom deformation did not occur during implantation are unlikely to fail if the implant positioning was optimal.
2. The ASR modular head with a THR stem has a much higher failure rate than the  ASR resurfacing.
3. Patients with pseudotumors and very high metal ion levels are likely to be  symptomatic . (Of course there are exceptions to every rule and  I am aware of Tony Nargol's asymptomatic pseudotumours . )
4. Metal ion level estimation is a good way of surveillance of the problem though there can be confounding variables.
5. MRI with specialised metal artifact reduction sequences are useful when the metal ion issue / clinical symptoms are on the borderline.
 
The real problem for surgeons in this failing MoM issue is that when a patient with this problem potentially, is being assessed .The decision the surgeon has to take is unfortunately  an 'all or none' one. ie whether the prosthesis has to be revised or not . There is no half way measures like prescribing medicines, physiotherapy or injections.
Revision of the ASR or any prosthesis for any reason is always always problematic surgery and patients are likely to have only a small part  of the functional level that  they had with a primary arthroplasty. I personally like to use poly in most revisions as polyethylene is most forgiving on cup positioning. The ideal angles of  cup position can never be guaranteed in a revision surgery and it is dependent on location and amt of  residual bone stock. (   Thus all activity restrictions of a  conventional THR will apply postop in a revision situation).  The reported dislocation rate after revision THR can be as high as 20%.
Thus  if some patients get revised unnecessarily due to this 'scare' it would be a great pity in my opinion. Nearly all patients who have had the ASR or modular heads are young and active as a prerequisite for using the resurfacing design . It goes without saying that they will all be sorely disappointed with the functional level of revision THR.  So a balanced approach seems to be the need of the hour.
 
With the above considerations and the fact that I am yet to see my first  ASR pseudotumour  my present plan is as follows.
 
Advise 'symptomatic' ASR patients who contact us  to get metal ion testing done. If borderline then a MRI is to be done. (if a questionnaires is sent explaining the problem then all patients will report some 'symptoms' making it impossible to interpret).  When 'asyptomatic' ASR  patients report for routine follow up - have the metal ions tested.
 
Currently I have tied up with a lab and MRI centre in chennai where I work closely with the respective personnel and all patients I send there  will have the costs covered by Depuy.  The results currently are not very reliable and we are trying hard to standardise them . I have a handful of ASR patients scattered around the globe and honestly I do not know the way these patients can source these tests locally . I can only  advise them to contact the local depuy and ask for help in this regard.

I am not yet confident of advising patients with  'yes or no' to revision based on the lab results apart from the extreme ones. Once I am more sure of this and our investigations are standardised , I plan to bring all ASR patients into this surveillance. ( I have discussed this with many surgeons in India and they seem to concur with the plan. ie start with the symptomatic ones and gradually  include everyone in a phased manner). Our hospital clinics , ORs and labs all have their ceiling capacities and we if suddenly deluge them with a panic response , they  are likely to  buckle under the pressure.
 
with best regards
vijay bose
chennai"

Responses from some of the top surgeons

Dr. Thomas Schmalzried
March 10, 2010

Dear Vicky,

The great majority of my patients with an ASR™ bearing (resurfacing and conventional THR) are doing well.  If there is a problem with any metal-metal bearing (including the ASR™), symptoms (pain) are usually present within the first year.  If the patient is feeling well, it is most likely that the bearing is working well and there is little risk of tissue damage.  There is no “acid test” to determine if a patient is sensitive or allergic to a metal-metal bearing. If you are concerned, you should come in for an interview, physical examination, and x-rays.  This is the best way to assess the condition of the hip, regardless of the bearing. I recommend annual or every other year follow-up for joint replacement patients (regardless of bearing material) so that problems can be detected and treated early.

Best wishes.

Thomas P. Schmalzried, M.D.


Dr. Vijay Bose
February 25, 2010

I am aware of the ASR issues for about 6 months now.  There is no doubt that the safety margin for the ASR is lower than other resurfacing system due to a 'low arc of cover'- described by Koen De Smet.  Hence the failure rate is higher than the BHR.  That said, I have not had a single failure with the ASR or the ASR with XL head combination over the last 4 years (over 300 cases) The cups coming loose is certainly not true as I have implanted ASR cups in the most complex of cases. I am 100% confident that it is a technical issue.
It has proven to be an excellent tool in my hands and in dysplasia patients (CROWE 3) the s-rom with a ASR cup is hard to beat.

The ASR reamers are very poor and not matched to the ASR cups. I have routinely used BHR reamers for the ASR cups for 3 yrs now when I noticed the mismatch between the reamers and cup size.  The ASR has been excellent tool to provide an anatomical metal on metal articulation in small patients. I am very confident that it will work well if installed corrrectly. I will surely miss the ASR cup for small made patients if it is withdrawn completely.
 
with best regards
Vijay Bose
Chennai

Further comments from Dr. Vijay Bose
March 10, 2010

Hi Vicky,

When surgeons visit me to see me do ASR surgery or when I am doing live demo surgery - I demonstrate the technique of 'soft fit' to achieve reliable press fit. This is very helpful in cup without screws ( typically hip resurfacing cups). This applies to non resurfacing cups as well but not as critical as the screws can save the day if one does not achieve press fit.
Surgeons who learnt the technique of soft fit from me consistently commented that the resurfacing cups like the ASR suddenly 'turned' very reliable and they never had any issues with cup loosening subsequently though there were many issues prior to that. Thus this whole matter of the ASR cup not integrating is due to surgical technique and not a true design issue.  In my opinion, the design team for the ASR made a small mistake in making the differential between the cup trial and definitive cup very small ( .5 mms) . This is too small compared to other resurfacing devices. Unless the surgeon appreciates this issue he is likely to make a mistake ie. If the trial for the specific implant size is fully seated during the surgery, then the press fit for that size is destroyed and the cup will not be stable. The trial should never bottom out in an ASR. This is very different from other systems like the BHR where the trial - definitive implant differential is 1.5 mms or 3 times that of the ASR.  This is the main source of the ASR errors on the acetabular side.
 
Thanks
 
with best regards
Vijay Bose
Chennai

Dr. Scott Ball
March 10, 2010

Yes, I know about DePuy's decision to discontinue the ASR.  No, I don't think there is anything to worry about.  Here is the whole scoop as I understand it (from direct communication with the company and a designer). If implanted correctly, it should show the lowest wear rates of all available devices - that applies to you - your component position is EXCELLENT. Also with the larger implant sizes, things look great.

The design issue that was discovered is that the implant can be sensitive to component malposition particularly in the smaller sizes. When trying to minimize wear in metal-on-metal hips, getting a smaller 'clearance' leads to
lower wear. 'Clearance' is the difference in size between the head and the inside of the cup. If they were the exact same size, they could bind. So the head needs to be marginally smaller. If the head is much smaller though so that it is a looser fit, you get increased contact stress and therefore more wear.  Depuy went for the lowest clearance possible with the design in hopes of minimizing wear. As one compromise to allow a tighter clearance, they made the cup just under a full 180 hemisphere to avoid rim binding. It appears however
that by doing that, the cup is more sensitive to poor positioning. That means if you get it in between 35 and 50 degrees in the frontal plane (your cup is a perfect 45 degrees) that should yield very low wear. However if you put it too vertical (above about 50 degrees) you may get more wear (since the implant is less than a full 180 hemisphere 50 degrees with this cup may seem more like 55 to 60 with other full hemispherical cups.)

That is a long description of the issues at hand. Despite all of these things, the implants have performed well and I have had no issues with any of my patients -- in fact the most impressive results I have had to date have been with the ASR.

So why is DePuy discontinuing the ASR?
There have been an interesting string of Business events that of course they don't typically tell the surgeons until the decisions have been made.

1- The FDA review of the ASR data set came back wanting more enrollment prior to full unrestricted FDA approval - that equals big investment on the part of DePuy with no guarantee of a pay-off at the end.

2- Resurfacing market is no longer growing nationally and internationally - if anything it is contracting - less of a pay-off for the company - research and development costs with no pay-off = bad business

3- A small company in England called Finsbury has previously done all the manufacturing for the Birmingham Hip and for the Adept Hip Resurfacing. J&J / DePuy acquired Finsbury a couple months ago. All BHR manufacturing has now shifted in house with Smith and Nephew. Finsbury looks to have a ceramic hip resurfacing in the pipeline which may be the 'holy grail' for hip resurfacing - lower wear rates, no risk of metal hypersensitivity, etc.

Conclusion- - It would appear that DePuy has made a business decision to stop investing in developing and distributing the ASR in favor of acquiring a company that has its own resurfacing device, the Adept, and may have the 'next generation' resurfacing device coming down the pipeline in the future.
The bottom line is, I don't think you have anything to worry about with your hip. If the cup was not going to ingrow we would know that by now. Your implants are perfectly positioned and BIG in size so you should actually have the lowest wear resurfacings of anyone out there.
Long winded response. I don't know how much of this info is out there. What I just described here is my best impression of the issues with the disclaimer that I don't have any vested interest in any of these companies and certainly don't sit in on the business decisions so I am not privy to the actual details - consider what I just wrote as well-informed rumor, not necessarily fact.
Take care,
-Scott Ball

Dr. John Antoniou

Hi Vicky,