I have to start by saying that I have never had any issues with the ASR devise at all. I was very surprised about 6 months ago when the issue of ASR withdrawal first surfaced. There is no doubt that the safety margin for the ASR is lower than other resurfacing systems like the BHR due to a 'low arc of cover'- described by Dr. Desmet. This is because the rim of the cup has become 'non -articular' to accommodate the cup holder. Hence the failure rate is higher than the BHR.

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 combination that is hard to beat.

The ASR reamers are very poor and not matched to the ASR cups. I have routinely used BHR or equivalent reamers for the ASR cups for 3 yrs since the time noticed the mismatch between the reamers and cup size for the ASR

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 correctly. I will surely miss the ASR cup for small made patients if it is withdrawn completely.

with best regards
vijay bose
chennai

The controversy regarding adverse wear in metal-metal bearings

Thomas P. Gross , MD 3/5/2010

I have used over 3000 metal bearings in primary total hip and hip resurfacing as well as revision surgery. I have revised 2 for adverse wear 7 years after implantation. I know that most other high volume hip resurfacing surgeons have a similar experience. The revisions were straightforward and the patient enjoyed the same rapid and complete recovery as if she had a primary hip replacement.

Currently less than 5% of my practice involves revision surgery. However, I have revised over 100 metal plastic replacements for excess wear. Furthermore significant wear related damage to the tissues is seen in virtually all metal plastic hip replacement or knee replacement revised for other causes.

A surgical group that has seen a surprisingly large number of wear‐related failures of metal bearing implants has coined the term "pseudotumor" when an inflammatory soft tissue mass is seen around the hip of a metal bearing implant. However, this inflammatory soft tissue reaction to metal wear debris is not much different than the inflammatory reaction that we have seen with plastic wear debris for many years.

All artificial bearing implants give off wear particles. The question is, which type of wear debris is best tolerated by the body? During the last 20 years of joint replacement polyethylene osteolysis (bone destruction caused by plastic wear debris) has been a major problem. But anyone who has revised total joints is also aware that polyethelene debris also is always associated with large amounts of soft tissue reaction around the joint. Polyethelene has been improved, and metal bearings have been developed. Both give off much less wear debris than the old polyethelene implants. The question is which results in less wear related damage? At this point we do not yet have the answer. Adverse wear reaction is a serious problem, but fortunately it is very rare.

Lets put this into perspective. The most common reason resulting in revision of total hip replacements in the US is hip instability (recurrent dislocation). 20% of all hip revisions are done for this reason. This is far more common than adverse wear reaction. Hip instability is a very disabling condition that occurs in 3‐5 % of hip replacements. The rate of instability for large head metal bearings is less than 1/2 %. Larger bearings are the solution for this problem. Large head metal bearings (resurfacing and total hip) are currently the only ones that allow reconstructing the hip in a biomechanically normal fashion to avoid instability. Proponents of plastic and ceramic bearings realize this and have made their bearings thinner recently to allow larger heads to be inserted (32‐36mm). This has made them more stable, but 32‐36mm does not yet approximate normal femoral head sizes in the average female (48mm) and average male (52mm) patients. These larger head (32‐36mm) implants for plastic and ceramic bearings have only been in use for a few years and it is not yet clear if these bearings will break at a higher rate because they are thinner. I would not recommend impact sports on thin plastic and ceramic bearings. Anatomic sizing that matches the patient's own size is only possible with large metal head designs. These are stable and can tolerate repetitive full impact without breaking. Wear rates are not significantly increased by running.

In the last few years we have learned that these rare cases of adverse wear in metal bearings are related to three factors: steep acetabular inclination greater than 55 degrees, small component sizes, certain component designs with an extremely shallow arc of coverage. At this point it is still only a very tiny percentage of patients with cup inclination angles above 55 degrees that have had wear problems. If a patient with an inclination angle above 55 degrees develops symptoms years after surgery, I would first check metal levels and an MRI. If the levels were high or a soft tissue mass developed I would recommend revision. So far this has happened twice in my practice.

More important, however, is prevention of this adverse wear complication. Since this information about cup inclination has become available several years ago we developed and tested a protocol for measuring the inclination by XR during the operation. The paper reporting this technique will be published in CORR this year. Using this technique in every case, I now have had no cups implanted with inclination greater than 55 degrees since 10/ 2007. We expect that this technique will completely eliminate this rare cause of failure in metal bearing hip implants: adverse wear reaction.

Knowing the cause of resurfacing failure can ensure successful conversion to THR by Edwin Su, MD
The shell can be retained in cases involving femoral neck fracture, femoral loosening or impingement.

Read Complete Article by clicking here

March 2010

Causes of failure

"The cause of failure must be carefully assessed prior to the conversion surgery in order to ensure an optimal THR outcome," Su said. He noted that femoral neck fracture is the primary cause of short-term failure in resurfacing procedures. He theorized that the rate of these fractures could be reduced with improved surgical techniques, careful patient selection and preoperative evaluation of bone quality. Inadequate acetabular fixation or the so-called "slipped cup" is another cause of early failure, which may also be related to surgical technique.

"The greatest cause of a mid-term failure is femoral component loosening and osteonecrosis probably plays a role in this," Su said. "I think that component malposition is going to play a large role in these mid-term failures as well." He noted that mid-term investigations of patients with acetabular component malpositioning revealed painful metal reactivity requiring revision.

Other causes of failure include metal hypersensitivity and unexplained pain due to impingement, undetected stress fractures or pseudotumors...

...Shell retention or full revision?

In planning conversion procedures, surgeons have the option of retaining the shell from the hip resurfacing.

"I think this is acceptable for a well-positioned, well-fixed and undamaged shell," Su said. "It is applicable in situations such as, a femoral neck fracture and in a femoral loosening...

..."A full revision is necessary when there is component malposition of chronic duration because there will be damage to the metal components," Su said. "It is also best when there is a question of metal hypersensitivity."

Reference:

• Su E. Surface replacement conversion: Assuring an optimal THR outcome. Paper #44. Presented at the 26th Annual Current Concepts in Joint Replacement Winter Meeting. Dec. 9-12, 2009. Orlando, Fla.
• Edwin P. Su, MD, can be reached at Hospital for Special Surgery, 535 East 70th Street, New York, New York 10021; 212-606-1128;

Hospitals more specialized in orthopedic surgery show better outcomes for hip and knee replacement

 February 17, 2010  Click Here to read full article

A recent study of Medicare data by University of Iowa investigators indicates that hospitals with a higher degree of orthopedic specialization provide better outcomes for patients undergoing hip or knee replacement surgery.

The findings, which appear in the online version of the British Medical Journal, were based on a retrospective study of nearly 1.3 million Medicare beneficiaries aged 65 years and older who had hip or knee replacement procedures between 2001 and 2005 at 3,818 U.S. hospitals. The investigators grouped the hospitals into five categories according to their degree of orthopedic specialization. Orthopedic procedures accounted for 10.5% of admissions at the average hospital, while they represented 14.5% or more of the admissions in the most specialized group...

..."The findings suggest that more specialized hospitals have better outcomes even after we account for the type of patients each hospital cares for and the number of hip and knee replacement surgeries that each hospital performs," Tyson Hagen, MD, the lead author of the study, stated in the release...

Reference: Hagen TP, Vaughan-Sarrazin MS, Cram P. Relation between hospital orthopaedic specialisation and outcomes in patients aged 65 and older: retrospective analysis of US Medicare data. BMJ. Published online 2010 Feb 11.

The status of DePuy Orthopaedics’ ASR platform as Feb. 2010

Last fall of 2009, DePuy decided to discontinue ASR® XL Acetabular Head System and DePuy ASR® Hip Resurfacing Platform (not available in the U.S.) worldwide. As a result of declining demand for the ASR platform and other market factors, DePuy is in the process of phasing out this platform to focus on the development of next generation hip replacement and resurfacing technologies that best meet the needs of surgeons and patients.

DePuy wants to assure patients who have been treated with a device from the ASR platform that there will be options available to them in the future should they need a revision:

· If a patient who had received the DePuy ASR® XL Acetabular Head System for total hip replacement requires a revision surgery, the acetabular component could be revised with the Pinnacle Hip Solutions platform, which would be compatible with an existing well-fixed femoral stem.

· As with any hemi-resurfacing prosthesis, including the DePuy ASR® hemi arthroplasty, a patient requiring a revision procedure would generally be treated with a total hip replacement.

· For patients outside the U.S. treated with DePuy ASR® Hip Resurfacing (not commercially available in the U.S.), DePuy intends to maintain an inventory of ASR XL heads outside the U.S. for use on compatible DePuy femoral stems. This will allow surgeons outside the U.S. the option of retaining a well-fixed ASR Cup when appropriate as part of the revision procedure.

Lorie Gawreluk
Vice President, Worldwide Communications
DePuy, Inc.

WHAT ABOUT NAVIGATION

Today navigation is still a tool that is not easy to use and that needs a certain learning curve as resurfacing itself also has.

So it is not a useful tool today for resurfacing beginners, where it should be! It would be nice if it would be a help at the start of the learning curve.

So can somebody with experience use it or should they use it?

It is like doing a certain approach and having experience with it, so it feels better and confident.

Most of the experienced surgeons do feel they do not need it. MAYBE it could help.

BUT there are some things that have to be cleared out still today:

*there is no correlation in most of the systems between head and cup.
*Most of the systems only look to the head, and nobody can tell us today what is now the best place to put the implant
*It would be the best to use it for the cup because there we have the most failures!

BUT AGAIN the most problems will be with females, that easily have twisted pelvis on the table and smaller sizes, and it is not sure it will have a big influence here.

If it is a system with preop CT of the pelvis to do the acetabulum, the pictures are taken in SUPINE (lying down position!). The patients walk and run on their hips, they do not lie on them, and that can make a complete difference!

So we are not there yet, if something could help me to do better surgery it would be navigation, but as it is today, it is not a 100% proven project. I have today so designed instruments that I call it navigation without navigation; of course in other sites navigation really could help!

I do not know if the 7 malpositioned cups in my series of 3000 would have benefited with navigation, possibly yes, but maybe would have had others where then the placement was worse?

It is the future?, maybe, but not there yet at present for everybody. That is why not everybody is using it, not just because we would be to lazy, to old, to stubborn or whatever.

If it would be used tomorrow in all cases from the start, the worry is also there, that if the navigation fails we do not know anymore what to do. All these facts should not be used for marketing or publicity issues but left to the orthopaedic community to make it better, try it and try to succeed better, what prof.Cobb, myself and all others I think try to do.

KOEN

koen de smet

hipsurgeon amc gent krijgslaan 181 9000 GENT BELGIUM +3292525903 www.heup.be

anca clinic roma valle giulia ROMA ITALY www.ancaclinic.it

There is some data indicating that navigation can improve the accuracy of femoral component placement in hip resurfacing.  The real issue is "compared to what?"  For an inexperienced surgeon, navigation may help him avoid component positioning problems that have been associated with "the learning curve".  However, for an experienced surgeon, who has an established mechanical alignment system with a high success rate - it is difficult to demonstrate an advantage to him with a navigation system.  Further, the registration process takes a little time – so the cost-to-benefit ratio for the experienced surgeon in a busy O.R. is questionable.  The navigation systems are not hard to learn to use, even for old guys like me!

A bigger challenge is acetabular component positioning.  This is true for total hips, and even more important for resurfacing.  There are 2 parts to the acetabular positioning problem.  The first is identifying the desired position for that patient and the second is putting the cup in that position.  Keeping the pelvis in one position and finding accurate pelvic/acetabular landmarks can be challenging.  The lateral opening angle is the easier part.  Most surgeons today agree that between 40 and 50 degrees is desirable.  Version is more complicated because the desired acetabular version is dependent on femoral version.  Acceptable version is also related to the lateral opening angle and the resultant bearing contact area.  Again, the issue is experience.

If I have any doubt about component positioning, I get an intra-operative x-ray.  Admittedly, there can be some challenges to getting a good intra-operative view.   For what it’s worth, we did an x-ray review of my first 500 resurfacings (minimum 1 year follow-up).  I have never had a femoral neck fracture and all sockets are below 50 degrees lateral opening.

Best wishes.

Thomas P. Schmalzried, M.D.

Computer aided navigation is an interesting concept. However, there is no evidence that it leads to better clinical outcomes and fewer failures. On the other hand, there is ample evidence that surgeon experience has a dramatic effect on outcomes and complications. 

One way to conceptualize this is that the experienced surgeon’s brain is a computer with much more sophisticated "software" than a navigation computer. When a computer is programmed, an algorithm must be created which has certain inherent limitations. Furthermore additional significant sources of errors are introduced by the registration of anatomic points for the navigation computer in surgery.

My personal opinion is that navigation that is based on a pre-operative CT scan data, which is being pioneered by Justin Cobb, has tremendous promise in the future to improve the results. At this point, we are still in the early development phase. It will probably add several thousand dollars to the cost of each operation. 

In summary, I believe the right kind of navigation surgery based on accurate 3D CT scans holds tremendous promise for the future. It will still require an extensive amount of preliminary development work before it is ready for routine use. 

I hope this helps with this very complex issue. 

Best regards,
Thomas P. Gross, M.D.

Computerized navigation has been around for a long time, in total hips, total knees, and now hip resurfacing. A lot of surgeons, including me, have tried it out and not seen an advantage in all but very exceptional cases. Yet other surgeons use it on every case.
 
This is what I think about computerized navigation: It is a tool which can narrow the "bell-curve" of component position, but the curve still has some spread. That helps a surgeon avoid "outliers", or badly misplaced components. Navigation does not make component position the exact same every time, but it helps avoid those outliers. (If it was the exact same every time there would be no bell-curve at all.)
 
So, if a surgeon has no outliers, in other words if he is doing a good job of keeping his personal bell-curve narrow, there is no advantage to using computer navigation. Alternatively, if a surgeon thinks he might accidentally misalign a component so much that it would be considered an outlier, the computer may prevent that.
 
Like any computer, what comes out depends on what went in. Registering the anatomy (which tells the computer where everything is) at the beginning of a computer-navigated operation is not at all an exact science, but depends upon knowledge and experience. It's the same with mechanical alignment jigs. With either method, one should hope that the surgeon is ready to adjust the verdict of the computer or the jig to place the component accurately in the bones which are clearly visible.
 
Are there any downsides to using a computer? Well, there is the extra time involved, which prolongs the surgery (think infections, blood clots). There is extra expense. There is often one more person in the OR, and more traffic in the OR can lead to infection. There is the possibility of surgical complacency if the doctor believes in the infallibility of computers.
 
I have heard this discussed at resurfacing meetings, and people whom I respect more than any others in this field have tried navigation and declared it "useless", and a "waste of time". While unwilling to go quite that far, it does make me think I am fine in continuing with mechanical jigs.
 
Your question about doctors not having 100% "retention" due to component malposition requires a reply. Personally, I have not had any failures in almost 600 resurfacings due to component malposition. I have 1 femoral neck fracture due to leg presses 8 weeks after surgery, and one pelvis fracture resulting from trauma 2 years after resurfacing. That's it. But malposition is an important cause of fracture, wear-related failure, and possibly pseudotumors as well, so should be avoided.
 
Any surgeon "young" enough to learn hip resurfacing is certainly young enough to learn the much easier task of computer navigation, so people who consider someone too "old" to learn navigation are being silly.
 
Similarly, a patient who would choose his surgeon based upon their use of computer navigation is badly misguided. There are many much more important issues to consider.
 
Having said all this, I wouldn't be surprised if at some point in the future surgical navigation becomes more accurate, easier, cheaper, and quicker. Robots will substitute for doctors. Surgeons will look back on the old days and shake their heads in amazement that we used to do all this by hand.
 
Peter Brooks MD, FRCS(C)
Cleveland Clinic

Using computer navigation in  joint surgery is a double edged weapon. While potentially it can reduce the number of outliers,  it can also cause tremendous deviations and absurd placements which would never be done with conventional jigs. I have seen many examples of this done elsewhere and referred to me for revision surgery.

Generally the input to the computer is made by a technique known as bone morphing where the surgeon uses pointer probes to point out the various bony landmarks to the computer. If the surgeon makes an error in this step then it obviously carries on in all further steps leading to a faulty placement. To argue that it removes human  error is most irrational.

We have the brainlab navigation ( market leader in navigation)  in our unit since 2007 and I did a series of cases at that time ( about 80 cases) . I have to say that the femoral cap placement was inferior to my placement with traditional jigs. However I found it useful when one had distorted anatomy as in previous prox. femoral osteotomy. I still use it for such cases.
 
There are many reasons in my opinion by which the conventional jig is far superior to the navigation in hip resurfacing.
 
1. bone morphing with the pointer probes damages the neck capsule which I protect passionately during hip resurfacing surgery and which I am sure is one of the key elements for my success rate.

2. I  use navigation routinely  during my Total knee replacements as the aim of the TKR surgery is to allign the components to the hip and ankle which are not visible in the surgical wound. In contrast in hip surgery the goal is not to align hip component to the spine , pelvis or knee/ ankle. The aim is to align components to local landmarks in the surgical wound, the location of which is given to the computer by the surgeon.  Then the computer gives back the same information which the surgeon offered in the first place. ( this is unlike the TKR where the computer picks up the hip on merely moving the hip and not morphing). Arguments that the computer increases accuracy in hip surgery is frankly absurd and have to be dismissed as marketing techniques.
 
3. The concept of incorporating the  combined anterversion is now the key in operating on FAI ( Femoro- acetabular impingement) which is the pathology in over 95 % of male patients having primary osteoarthritis. This is a dynamic assessment and can be done only with a jig using a lat cortex pin and cannot be done with navigation.
 
Having said all of the above  one must make a distinction between what Prof. Cobb uses and what others use.

Prof . Cobb is the  only one to my knowledge who uses a CT based navigation. The CT gives information which the surgeon cannot access unlike imageless navigation with all other surgeons which depends on surgeon's input based on bone morphing that  defeats the whole purpose of navigation.

In conclusion I would like to say that imageless navigation has very limited role in hip arthroplasty ( eg previosely operated cases) and is an excellent tool in Knee arthroplasty.
CT based navigation for hips which is still not available commercially ( which prof. Cobb uses) may have a significant role in hip arthroplasty. This has to be balanced with the radiation dose for routine CT to be applied universally( approx 30 -50 conventional x-ray dose )
 
wishing you the very best
 
with best regards
vijay bose
chennai