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Commentary on an article by Stephen S. Tower, MD: “Arthroprosthetic Cobaltism: Neurological and Cardiac Manifestations in Two Patients with Metal-on-Metal Arthroplasty. A Case Report”
Joshua J. Jacobs, MD1
1 Rush University Medical Center, Chicago, Illinois
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In support of his research for or preparation of this work, the author received, in any one year, outside funding or grants in excess of $10,000 from Zimmer, Medtronic, Spinal Motion, NIH-NIAMS (AR 39310). In addition, the author or a member of his immediate family received, in any one year, payments or other benefits in excess of $10,000 or a commitment or agreement to provide such benefits from a commercial entity (Zimmer, Medtronic, Johnson and Johnson, Implant Protection).

Copyright © 2010 by The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2010 Dec 01;92(17):e35 1-2. doi: 10.2106/JBJS.J.01657
The main article is available here
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This issue of The Journal of Bone and Joint Surgery includes a report on two patients with metal-on-metal total hip replacements who developed systemic neurological and cardiac complications associated with an elevation in serum cobalt levels. Causality is suggested by the fact that the systemic symptoms improved in at least one of the two patients following revision surgery. The report is unusual because of the rarity of the occurrence of metal-induced systemic complications in patients with total hip replacement and the fact that the author was one of the patients. As millions of patients worldwide have undergone total hip replacement, these cases represent rare events indeed.
Metal-on-metal bearing surfaces in total hip arthroplasty have been in use for over fifty years. The earliest iterations of these devices lost favor in the 1970s and were replaced by metal-on-ultrahigh molecular weight polyethylene implants. As the indications for total hip replacement were extended to younger, more active patient populations with higher activity demands, clinically important problems such as osteolysis and aseptic loosening related to bearing surface performance were reported with increasing frequency. So-called alternative bearing materials were developed with the goal of reducing wear debris and decreasing osteolysis, aseptic loosening, and other wear-related failures. Metal-on-metal bearings generally demonstrated reduced volumetric wear in comparison with metal-on-polyethylene bearings in hip simulator and implant-retrieval studies. Metal-on-metal bearings allow the use of thinner acetabular components and larger femoral heads, which have been associated with a lower rate of postoperative hip dislocation. Thinner acetabular components also facilitate hip resurfacing.
As is the case with metal-on-polyethylene bearings, ceramic-on-polyethylene bearings, and ceramic-on-ceramic bearings, there are potential risks associated with metal-on-metal bearings that accompany the potential clinical benefits. One such risk associated with metal-on-metal bearings is the potential for adverse biological responses to elevated levels of cobalt and chromium in local and remote tissues. This risk is not unique to metal-on-metal bearings as other metal devices with accelerated damage due to wear or corrosion can lead to elevated levels of metal in local and remote tissues. In fact, four of the six reported cases to date that have demonstrated chromium and cobalt-associated neurological and/or cardiac complications had bearing couples other than metal-on-metal. In orthopaedic surgery, metal devices are used for joint replacements, fracture fixation, spine fusion, and tumor reconstruction and therefore are essential for the orthopaedic surgeon. However, if metal release is extensive as a result of wear or corrosion, adverse local and systemic biological responses can ensue. At the present time, there is no generally accepted threshold beyond which serum or blood concentrations of cobalt and chromium are known to be toxic in patients with a metal implant. As there are known risks of revision surgery, undertaking such a procedure on the basis of the blood or serum metal level alone and in the absence of symptoms is problematic. The value of these case reports would have been enhanced if there had been additional clinical, histological, and radiographic detail demonstrating implant orientation (particularly in Case 2, in which this information is quite limited) and if there had been additional detail regarding the methodology of the metal measurement in serum. The latter is particularly critical given the known variability in these measurements, which makes comparison of the metal concentrations in different published series difficult. Nonetheless, there are important lessons that can be learned from these two cases: (1) routine periodic surveillance by an orthopaedic surgeon is recommended for patients with total joint replacements to identify and treat, in a timely fashion, any prosthetic-related complications; (2) surveillance should include both an evaluation of the replaced joint and a discussion of the overall health of the patient; (3) determination of concentrations of metal in the blood or serum may be helpful for the evaluation of patients with local pain and/or otherwise unexplained systemic symptoms and should be used in concert with other clinical and radiographic information; (4) the orthopaedic surgeon should be cognizant of these rare systemic complications of metal devices undergoing accelerated wear and corrosion; and (5) expeditious revision surgery should be considered for a symptomatic patient with evidence of accelerated wear or corrosion who demonstrates local and/or systemic complications associated with the device.

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Stephen S. Tower, M.D.
Posted on April 04, 2011

Dear Bill,

One other idea. It might be reasonable to swap out the cobalt-chrome steel ball for a ceramic ball so that all of the chrome-cobalt metal is gone. This is usually easily done and the ball needs to be changed anyway.

So patients with painful Metal-on-metal hips a sensitive to even minute amounts of cobalt or chrome. If you have a ceramic-on-plastic hip you and your surgeon will have eliminated that concern.

Sincerely, Stephen S. Tower M.D.

Stephen S. Tower, M.D.
Posted on April 04, 2011

Dear Bill,

I am sorry for your troubles.

You might consider printing out my 3/11 post and giving it to your cardiologist, your primary care MD, and your surgeon.

Your levels of cobalt might have something to do with your heart arrhythmia. Cobalt at your level can cause either a constrictive or dilated cardiomyopathy. Patients with cardiomyopathies ofter have arrhythmias. There is a link in my 3/11 post to my Alaska Medicine paper the covers cobalt and the heart in detail. You might print that out and bring it to your doctors as well. It is a problem that was rare before the metal-on-metal hips got popular so your doctors might not be familiar with cardiac cobaltism.

The good news is that in some patients the heart problem will reverse itself once the cobalt levels go down, this might take a year. We do not know if cardiac cobaltism is always reversible. Fortunately, it was in my case.

I think you ought to get a through neurologic evaluation. That is detailed in my 3/11 post. You also ought to have your thyroid checked out.

I suspect your renal function is normal despite only having one kidney but that ought to be checked as well. In theory the high levels of chromium that accompany the high cobalt levels might cause kidney damage. Since the cobalt and chromium are excreted by the kidneys levels are higher with folks with less than normal kidney function. This might potentially turn into a vicious cycle.

The neck pain is something that might not be related to the cobalt. Cobalt has been implicated in peripheral neuropathies but those do not normally present as neck pain. People with peripheral neuropathies are usually bothered first by painful or numb feet, balance problems, and weakness in the legs if the condition is advanced.

Sincerely, Stephen S. Tower, M.D.

Stephen S. Tower, M.D.
Posted on March 27, 2011

Dear Dr. Alvarez,

My largest disappointment with the ASR™ experience is that it might not contribute much to our understanding of cobalt and chromium heavy metal poisoning. When I found my ion levels to be notably high in the spring of 2007 I started my inquiries with Depuy’s design surgeons and engineers. They did not believe that there was reason for concern.

As my neurologic and cardiac toxicity became evident I continued to make inquires. It appeared that I was unique. Only when my bearing was explanted and I noted similar (fortunately less severe) problems with my patient did everything come together.

The CDC expressed more interest in arthroprosthetic cobaltism (APC) than the FDA did. I attempted to attract the FDAs interest in early 2010 without success. The CDC was ready to publish my cases in their Morbidity and Mortality Weekly Report (MMWR) in the summer of 2010 but they were torpedoed by the FDA because problems with hip replacements are their turf. I believed that APC represented a public health problem so I had shared my unpublished paper with the FDA, Depuy, and the CDC in early 2010.

The only good thing that might come of the ASR™ experience would be a cross sectional study of the thousands of Americans implanted with ASR™ to correlate cobalt and chromium levels with neurologic, cardiac, and thyroid function. Such a study would define the incidence and spectrum of arthroprosthetic cobaltism. This study has not happened, and does not appear likely to happen. Depuy in particular seems to direct a blind eye towards possibility of cardiac, brain, peripheral nervous system, and thyroid damage in ASR™ implanted patients.

After studying the third generation of MoM hips for greater that a year the FDA did finally release a patient advisory statement. It appears to have been written by the arthroprosthetic industry. In the midst of attempting to inform the FDA about the possibility of APC I contacted the physician in charge of studying problems relating to hip implants. He informed me that the FDA’s process in such matters was to “gather industry representative and surgeons that developed the implants to see if a problem existed.” I was neither a representative of industry nor a surgeon that had collaborated with industry.

As a scientist you realize that a rare opportunity exists to study the ASR™ implanted Americans. What impartial party should perform the study? Who should fund it? A rare opportunity is being wasted.

Posted on March 24, 2011

Dr. Tower,

Thank you for your informative writings. I’m a couple of weeks away from my revision surgery with a cobalt reading of 156 mcg/L. I had the hip replaced at age 57 and told the hospital that I only have one kidney (presumably congenital). I don’t know if that should have been a factor, but I proceeded on blind faith. My physicians never tested me for metal ionization until the recall, and I was too uninformed to know any better.

Now I have arrythmia and neck pain, which I have no idea if they are related to the ASR device. My surgeon wants to leave the original ball in place and replace the cap with a polyethylene plastic one. He says my body will naturally excrete the existing cobalt. Does this seem like a plausible explanation and plan of attack? Or will leaving the existing ball in place possibly result in future cobalt level problems, even though there is no longer metal on metal?

Thank you in advance,


J. M. Alvarez, Physicist
Posted on March 24, 2011

Dr. Tower,

Thank you very much for your kind reply. I am keenly interested in MoM bearing cobaltism for obvious reasons and hopefully, I am not overly concerned. Recently, an acquaintance of mine, age 76, who had a hip replacement three years prior to mine passed away. I cannot help but recall a statement in your most recent paper about the prevalence of symptoms similar to cobaltism in any aging population. Hopefully the FDA will fund a sizable clinical study which will shed much needed light on the subject.

Stephen S. Tower, M.D.
Posted on March 23, 2011

That patients and doctors are easily romanced by the short term success of any therapy has been well known since antiquity. Even today short term cure hinges on the confidence of the doctor and the confidence that the patient has in him. Expectations tend to dictate short term success. The long term survival of a hip replacement is an equation with multiple factors. These include the constitution of patient, the validity of the indications, the skill of the surgeon, luck, and the implants selected. Short term success is often not followed by long term success. My professor Dr. Rodney Beals often reminded me “Steve, nothing ruins good results as surely as long-term follow-up. To know if an operation is successful you must see your patients frequently and over many years.” Dr. Beals did not delegate the follow-up care of his patients to his minions. Only if he saw his patient thrive with his own eyes over the course of time did he believe in the validity of his own surgical work.

I hope that Alan’s arthroplasty sees him through 20 years. Some patients will see good long term results despite their third generation metal-on-metal (3GMoM) hips, regardless of whether they are stemmed or a resurfacing. The information to date indicates that the 3GMoM hips are failing at a greater rate than the Low Fiction Arthroplasty (LFA) of the 1970s, the second generation metal-on-metal hips of the 1990s, and the present generation of metal-on-plastic hips. The failure rates and mechanisms appear to mirror the experience of the First Generation Metal-on-Metal (1GMoM) hips of the 1960s and 1970s. One must remember that success at 20 years was the rule with the LFA, it was the exception with the 1GMoMs.

It appears that the reincarnation of the large head MoM hips (resurfacing or stemmed) is an example of survivorship basis. A handful of patients with 1GMoMs were reported to have done well and error of induction was made. This error is unfortunate for hundreds of thousands of 3GMoM implantees that will require comparatively premature high risk revision surgery. The public cost due to increased medical costs and economic losses will be tens of billions of dollars.

The foundational rationale the 3GMoM hips was that revision rates would be lower than other technologies due to lower volumetric wear. Although the amount of volumetric debris of the 3GMoM bearing might on average be smaller than that of some historical metal-on-plastic hips the local tribiology of chrome-cobalt metals debris seems to be comparatively more toxic than polyethylene debris.

The other disproven hope was that a revision of a 3GMoM hip might fare as well as a primary MoP hip. We now know that this is not the case and the reason that revisions of hip resurfacings do comparatively poorly again relates to the adverse tribiology of chrome-cobalt metal debris and the resulting periprosthetic tissue damage.

According to joint registry data and recent 9 year results of one 3GMoM hip resurfacing by its design surgeon revision rates are twice that of the Mayo clinic’s experience with the LFA of the 1970’s, an unselected series of their first 2000 cases by multiple surgeons, many of them trainees.

In 2005 two theories were cited by the advocate design surgeons in support of the 3GMoM hips. The first was a lower rate of revision. The second was that a resurfacing was a transition to a stemmed arthroplasty and that revisions of a resurfacing would on average fare as well over time as a conventional MoP arthroplasty. We now know that the 3GMoM hips (resurfacing or stemmed) have double the revision rate, and that the revisions comparatively do poorly.

The return of patients to activities not usually recommended by their surgeons has likely occurred over the past 50 years. It is the choice of the patient, and it has not been studied whether those patients that return to such activities have a high risk of a complication or premature failure and revision of their arthroplasty.

That patients with a resurfacing might on average return to a higher levels of activity than patients with a stemmed MoP bearing is likely due to expectations and the instructions given to the patient by their surgeon.

No claim of benefit of 3GMoM hips (resurfacing or stemmed) has been proven after ten years of clinical use. Further implantations lack rationale support. The local and systemic tribiologic complications compromise revision surgery and can result in irreparable neurologic and cardiac damage.

The continuing popularity of hip resurfacing appears to be supported by marketing rather than clinical science. Certainly marketing can be persuasive. Google surfacehippy and surf that site. Is this patient advocacy or is it marketing? Review the interviews with implant design surgeons and the pop-up-ads. Are the claims mades in favor of hip resurfacing supportable? Is there equal time given to possible acute complications and likely hood of a comparatively premature revision?

Are the fellows of the AAOS that are featured in, supporting, and advertising on this site in line with the AAOS’s standards of ethical conduct?

alan j pollock RPA-c
Posted on March 18, 2011

I should include the disclaimer that I am in Emergency Medicine and do not consider myself (nor should anyone else) an expert in orthopedics.

Thank you for your reply Dr. Tower. I should have commended you for reinforcing the need to fully inform patients of risk vs. benefit and alerting your colleagues that cobalt intoxication (systemic effects) occurs (of course, as you point out, they should know this). You have well stated that there are unknowns with respect to metal ion exposure. I have not seen the term “cobaltism” before; I assume you coined the word to describe the syndrome of cobalt intoxication. I think it important to have a name for something; it sticks in your mind. Many of my fellow patients were upset when the Oxford Group used the term “psuedotumor”, I was not and for the same reason.

As far as anyone owing me an apology, not at all. As far as being duped by the scientific literature, again, no. Is it complete, certainly not? Do the manufacturers list complications or unknowns, not enough? As mentioned previously, I looked at quite a few studies and articles both peer reviewed and not. I also looked at testimonials, both good and bad on the web as well as company and private practice sites. In addition, I reviewed material on the various “Surface Hippy” web sites. I tried to consider all this information with a critical (if not cynical) eye concluding the following BEFORE my surgery on Halloween of 2008;

1. The various metal ions in concentrations associated with a PROPERLY functioning prosthetic, seemed only a problem in those who were allergic (less than 1% was the figure I found) and for those who might go on to develop renal insufficiency. I did not see any mention of what would happen to those with renal failure (or what would need to be done) but deduced that the device would most likely need to be removed. The literature did mention that in the event of an allergy, the entire device would need to be removed, including a well fixed shell with all the problems that could stem from that. Most failed devices were surgeon error (see below).

2. There was minimal information of actual systemic metal toxicity from poorly functioning or damaged implants. I was aware of the Canadian beer drinkers from old news reports. I found a number of testimonials of those who complained of systemic symptoms. I deduced that one could experience similar problems with resurfacing. I planned to have metal levels drawn at three months and yearly anniversaries of implantation. I would have the device removed if high. I was able to find that levels under 2 ppb were desirable but it was unclear at what levels adverse effects could be expected. I was also aware that serum/blood levels were indirect markers of wear and not always correlated with local tissue reaction.

3. There were no cancer clusters but, local chromosomal and systemic immune cell changes were seen in some studies. It was unknown what this meant. I deduced that this may or may not be a problem and that there could be other ill effects that would not be known until large numbers of people had lived a long time with these implants. I have since found additional information which would not have swayed me against resurfacing. http://www.ncbi.nlm.nih.gov/pubmed/18720105

4. Studies at the time (and currently) did not give me enough information to compare patient satisfaction between THR and resurfacing in any meaningful way. I was impressed by testimonials. For resurfacing there were several Iron Man competitors, Floyd Landis and an Ultra Man competitor. As well, average guys like me. I never met an orthopedist that would recommend running to a THR patient. Not so with resurfacing. Part of the problem is the multitude of THR articulations and combined with age differences, I could not deduce much from the literature. I am sure that retrospective studies would show resurfacing patients much more active because that is the reason why most choose this procedure (not really useful). I guess prospective studies would be needed but again, would suffer from the same issue unless truly randomized.

5. Tissue damage due to metalosis, was a nasty complication from excess wear almost always associated with malposition of implant components (see below). There was also one year that McMinn had a number of cases. He attributed that to a change (not authorized by him) of manufacturing technique. Other’s disputed his finding. This could largely be avoided by periodic metal ion levels and prompt evaluation of persistent pain. Rarely, some are asymptomatic with high metal levels and local tissue damage.

6. That resurfacing is a technically very difficult surgery. Exposure, as you pointed out is poor. Implant positioning is critical. Most of what was available at the time revolved around femoral component alignment. However, cup position was beginning to appear increasingly in the literature as being extremely important. Different approaches have specific benefits and risks. These include blood flow to the head and neck (AVN and neck fracture), less exposure and more soft tissue damage. Some repair the capsule and others do not (a mistake from my readings). In my opinion, a successful surgeon is shaped by education and knowledge, training and experience and God given talent. A deficit in one area cannot be fully compensated by excellence in another. I thought that testimonials from patients of a specific surgeon were somewhat important.

7. Femoral neck fracture was possible. I concluded that this was almost always surgical error due to neck notching or poor patient selection due surgery before significant joint space loss (see above).

8. Nerve damage was seen more often due to needed manipulation. I had hypotensive spinal anesthesia with an epidural placed for later pain control. As soon as I became aware (Propofol is great), did almost constant neurochecks on myself till everything worked!

9. Catastrophic heterotopic ossification may be more likely, in part due to more soft tissue trauma.

10. The ASR device had different cup geometry (coverage and clearance If I recall properly) and was newer than other devices. I considered new, especially associated with the word different as meaning unproven and would not use it. I did the same for uncemented femoral caps as not much data was out yet. Today, I would consider uncemented.

11. I personally did not believe the known and unknown risks of a MOM THR acceptable. That is because I would only consider doing high impact with a resurfacing, no additional benefit with MOM THR over what I considered safer alternatives. Again, would have gone with ceramics as the literature suggests fracture of those is very rare now.

12. I deduced that failure rates for my age group and sex were about the same after eight years for the most current THR or resurfacing. I knew that short term was a bit higher but that this was usually due to surgical error. I was also aware that true comparisons were difficult to make (see above 4).

13. That this surgery was for a limited population, with the best survival rates seen in young men, who are active, larger boned, not more than a little overweight with osteoarthritis. Some considered this “cherry picking” but in reality, it is historically the group that suffered most from failed THR prosthetics. I was an “ideal” patient except for cam FAI.

There is of course a lot more out that I did not review. There were many conflicting studies concerning functional outcomes, patient satisfaction and implant survivorship. I agree that patients need to be made aware, we are somewhat lacking, printed materials are very useful. I had much more information available to me than the average patient. Personally, I do think that SOME marketing is not a bad thing, but the good must be tempered with the bad (information on complications). I believe that the overwhelming majority in the field of medicine truly want only the best. I think they are horrified when their patients suffer with complications from surgery meant to stop pain. I have no doubt that there is some cognitive dissonance reduction at work here, but most really believe in what they are doing. Money can and does corrupt, many times subconsciously. Dr. Tower, all your points are well taken. I have always acknowledged that there is legitimate disagreement on the subject of resurfacing. I stand by my first posting above.

Certainly more studies are needed to better quantify and qualify the long term effects of mildly elevated metal levels and the emergence of local and systemic effects. As I mentioned before, actual matched comparisons with resurfacing and the various THR articulations to show what can and cannot be done activity wise.

I had two year levels done by the Mayo Clinic Labs; cobalt 1.7 ppb and chromium 1.6 ppb. Unfortunately I do not recall if they were serum or whole blood. They may be falsely elevated values as I am not sure if other tubes were drawn before the metal free royal blue ones. My understanding is that one should never use anything but the needle in the standard “Vacutainer” assembly and that the metal sample tubes should be drawn first as all other ones may have metal contamination. Next year I will have them get three, first to be discarded.

To those here who have been injured or have had your patients suffer, I am very sorry. alan

Stephen S. Tower, M.D.
Posted on March 11, 2011

Dear Dr. Alvarez,

I believe that you can be reassured rather than concerned by a [Co] of 1.8 with the minimal hip symptoms and good function that you relate.

The following is my present algorithm for following patients with metal-on-metal hip implants.

Some patients will have an immune response to the metallosis and have a very painful hip with periprosthetic tissue destruction with a low [Co]. I work up these patients with an MRI of the hip. If the MRI shows that the periprosthetic tissues and being compromised I ask the patient to consider revision surgery.

With the good function that you presently have I would not be concerned but would repeat a [Co] in 12 months unless you note progressive hip pain or neurologic or cardiac symptoms beyond what you and your physician would consider to be normal for aging.

I apologize if my work has caused you unnecessary worry.


Stephen S. Tower, M.D.

Dear concerned clinician, or patient implanted with an ASR or other Metal-on-Metal hip bearing,

Thank you for your inquiry about monitoring for neurologic, cardiac, or endocrinological cobaltism.
Please refer to my Alaska Medicine Paper. (These pages may not be reproduced or distributed without written permission from the Alaska State Medical Association’s Publications Department. Complete copies of Alaska Medicine magazine may be requested by contacting:Dave Rush, Publications Director, Alaska State Medical Association, 4107 Laurel St.,Anchorage AK 99508-5334(907) 562-0304Fax (907) 561-2063 drush@asmadocs.org )

Considering the nascent and evolving knowledge on arthroprosthetic cobaltism I believe that the following monitoring program is indicated.

All Metal-on-Metal hip implantees (ASR inclusive) should have a serum cobalt measured annually. Although this measurement is done at reference laboratories most labs can draw and mail out the specimen (royal blue topped tube, drawn after at least one other tube).
Additional testing determined by serum cobalt level measured in micrograms per liter:
1 to 5: Excessive cobalt exposure. Repeat the test in 6 weeks to confirm persistent elevation. These levels may be associated with sub-clinical cardiomyopathy and sub-clinical cognitive impairments. Repeat serum cobalt and additional testing annually.
Neurologic evaluation as below if cognitive, memory, visual, or auditory symptoms.
Cardiac evaluation as below if progressive exercise intolerance.

> 5 to 20: Considered to be toxic. Repeat the serum cobalt and additional testing and test again every six months if level remains >5.
imPACT battery. http://ajs.sagepub.com/content/34/10/1630.abstract
Visual fields (computerized)
Nerve conduction velocity of the sural nerve.
Cardiac: Echocardiogram with “speckle” study.
Thyroid Stimulating Hormone (TSH)
> 20: Indicates extreme cobalt exposure. Revision hip surgery should be considered. Repeat serum cobalt and additional testing every three months pending and after revision surgery until all parameters are stable.
imPACT battery.
Visual fields (computerized)
Nerve conduction velocity of the sural nerve
Cardiac: Echocardiogram with “speckle” study.
Thyroid Stimulating Hormone (TSH)
Explanted Metal-on-Metal bearings should be submitted to a joint retrieval laboratory analysis of the total absorbed dose of cobalt and chromium by the patient. This information may be critical in determining the need for long term monitoring of neurologic, cardiac, and thyroid function as well as surveillance for hematopoietic malignancies.

Dartmouth Biomedical Engineering Center (DBEC) is interested in analyzing retrieved Metal-on-Metal bearings that are not involved in active litigation. The bearing must be submitted by the surgeon that revised the hip.
For patients in which their explanted ASR bearings has been submitted to Depuy should contact Depuy to confirm that the bearing will be analyzed the amount of cobalt and chromium missing from the bearing due to wear, corrosion, or fretting.
I would advise consideration of revision surgery in those monitored patients that show significant deterioration in neurologic or cardiac function and have serum cobalt levels exceeding 10 micrograms per liter.
For patients that have already had their metal-on-metal bearing removed I would still obtain both a serum cobalt and a serum chromium. It may take months or years for the serum cobalt and chromium to normalize. Significant elevations in serum cobalt and chromium may persist for months or year after the metal-on-metal bearing is removed. It may be possible to estimate the peak ion level at the time of revision surgery from a measurement made some months later.

Links to my paper in the American Journal of Bone and Joint Surgery that has further technical data two patients with cobalt poisoning from excessive wear of their Depuy ASR XL Metal-on-Metal hip bearings:




Link to American Academy of Orthopedic Surgeons commissioned commentary and my response as well as reports of two additional cases of arthroprosthetic cobaltism (APC):


Due to a busy private and professional life Dr. Tower is not interested in any Medical-Legal consulting work. I am willing to be contacted by concerned surgeons and physicians that are concerned that they might have a patient with systemic toxicity related to a Metal-on-Metal hip implant. Concerned patients should request that their treating primary doctor or orthopedic surgeon contact me.

Stephen S. Tower, M.D., Tower@afoc.com
3831 Piper Street, Suite 220, Anchorage, AK 99508
907.563.3145 (phone) 907.561.3967 (fax)

Revised 2/24/2010

J. M. Alvarez, physicist
Posted on March 09, 2011

I am a patient who was implanted with the recalled De Puy ASR in October 2009. As such, I have an intense interest in Co metalosis. I am a retired NASA physicist who, 11years ago, at age 62 was advised by his physician to consider a left hip replacement. I researched the area. Metal and plastic bearings were in use at the time, and ceramics in clinical trial. Because I am a very active individual, I chose to wait since the medical concensus appeared to be that 10 years was the lifetime of hip implants, barring ceramics which wore considerably less but one cracked in clinical trial .

Fast-forwarding to the present, I find myself in a difficult dilemma. At age 73, I am still very active but my blood has a Co ion level of 1.8 ng/ml, not too surprising since I have a Co/Cr MoM implant. Since it took me almost a year to regain my full strength and fully trust my implant in skiing and competitive sports, I truly do not want revision surgery even if it’s free. I do not want to sue either. I want a hip implant that will give me ten years of use but good luck with that. At present I am not experiencing any gross symptoms of metalosis but the hip hurts more now than a few months ago and it occasionally makes a clicking noise. Of course I’ve never been 73 before either and heard such noises from various body parts. However, for the reasons cited above, I must conclude that a revision is probable for me, perhaps even in the immediate future.

I commend Dr. Tower for following the great scientific tradition of going wherever experimentation leads. At present, his is the best case study regarding the side effects of metal implants. I would ask him to post an update on the details of his revision for those of us who may need information on revision.

Dr. Jacob’s commentary is well written and informative but I have always mistrusted medical research funded in any way by vested commercial entities.

Stephen S. Tower, M.D.
Posted on February 28, 2011

American orthopedics owes Alan an apology. Clearly we were overcome with irrational exuberance when we implanted 250,000 of our countrymen with metal-on-metal bearings with either a resurfacing or stemmed femoral implant.

Like Alan I was clearly duped by the “scientific” literature when I consented to have my ASR XL implanted. Being cognizant of the risk of catastrophic failure thin XLPE liners in a prior collaboration with Dartmouth Biomedical Engineering Center (Tower, Currier, and Currier, JBJS, 2007) I thought I made a rationale decision.

I was primarily guided by the published work of Metal-on-Metal “opinion leaders” Dr. Thomas P. Schmalzried and Dr. John M. Cuckler in my choice of an anatomically sized Metal-on Metal bearing on a stem. I choose not to have a resurfacing because periprosthetic fracture of the retained femoral neck was known to be the major cause of failure of hip resurfacing. I am aware that femoral periprosthetic fracture can be a challenging complication of hip arthroplasty (Beals and Tower, CORR, 1996).

I was also aware that a resurfaced hip has no advantage over a stemmed hip arthroplasty in patient satisfaction and that the resurfacing is more likely to fail than a stemmed arthroplasty (Ritter and Gioe, AJBJS, 1986). Other concerns were the circumferential capsulotomy required by resurfacing and that surgeon error in acetabular shell placement would be likely due a surgical exposure cramped by the retained femoral head.

Perhaps Alan was misled also by industry and surgeon direct to consumer marketing as well as a suspect literature.

I am concerned that American arthroprosthetic surgeons, our professional organizations, and our continuing medical education efforts have been conscripted into the Arthroprosthetic Industrial Complex (APIC). Perhaps, even worse, we have volunteered.

As long as the APIC is controlling our literature, our education, and is marketing directly to our patients arthroprosthetic evolution in the interest of the patient and the public is a forlorn hope.

Posted on February 27, 2011



alan j pollock RPA-c
Posted on February 18, 2011

Dr. Jacobs writes a commentary on a journal case report of two patients who suffered the effects of metalosis and cobaltism because of poorly functioning metal implants. I believe his response to the article was both balanced and delicate. I think he was more than cognizant that the author was one of the cases. However, his response was met by a broadside. I will not be so soft BUT I do empathize with Dr. Tower’s experience. I hope he heals, finds peace, and continues his good work healing others and easing their pain.

I was also 49 when, in the space of the half hour I lasted in a touch football game, went from running two miles a day, swimming at least half a mile four times a week, and biking 12 miles four times a week to crippled. Only the day before, I saw that I was bone on bone and realized that the pain in my left hip I thought was bursitis was actually arthritis from cam FAI. Having the resources of the Mount Sinai School of Medicine library, I embarked on a seven-month-long review of the literature. I chose, based on research, taking into account what I wanted to do with it and, yes, considered my fears and unsubstantiated promise too. There was not (and still is not) any agreement amongst the experts as to what would be the best for a particular patient. Therefore, I took it upon myself to explore. I found that nothing here is the best of all possible worlds. I am cynical, so I will say that I chose my own poison, made sure I could accept the bad if it would come my way, and went with it. Knowledge was my opium.

I am sure Dr. Tower did much the same. I believe that he considered what would be best for him AND his family, as I did. I now find him giving testimonial through this case report and his reply to commentary. ALL articulations have their problems, period! One must know them and be prepared to treat appropriately. People do not die from arthritic hips. So, going with Dr. Tower’s reasoning, why in God’s name implant something that can get infected and cripple you or even worse? Well, certainly I and Dr. Tower know the answer, as does everyone who walks in our shoes; the pain and disability eats one’s soul. We take our chances, and shake hands with the devil. I wanted to run, snowboard, bike, and swim again. And, I do.

The case report itself, well, I am absolutely flabbergasted that these two patients were allowed to languish so long with obviously malfunctioning prosthesis with metal ion levels known to be toxic and cause extensive tissue damage. I find it incomprehensible that one was the author of the case reports. To be truthful, not enough information is presented with the second case (yes some editing involved), but that level was high enough to consider action. The first take-home message is that these should have been removed as soon as practicable with those ion levels, especially in the presence of symptoms. The second message is that metal-on-metal implants must be placed nearly perfectly. The third message is that yearly x-rays and metal ion levels should be considered in ALL patients. And last, every patient must be told of the risks vs. the benefits and the unknowns. For me, running and snowboarding with a stem would have been frightening. If I couldn’t get a resurfacing, I would have gone with ceramic-on-ceramic and settled for a low-impact life. Deathly afraid of a THR periprosthetic fracture. A resurfacing periprosthetic fracture is a femoral neck fracture and means conversion to a THR (usually simple).

Obviously, I went with the resurfacing; had it Halloween of 2008. My testimonial is that it is great. But it is not for most. Metal ions, as Dr. Tower pointed out, are toxic at certain levels. Those levels are not agreed upon AND he correctly points out that it is somewhat unclear what long-term exposure will result in with even mildly elevated levels. He questions about what will happen as we get older as ALL persons will experience a declining renal function with age. I share his concerns. I will say, it is my opinion that the less than one percent true allergy level may rise with implant longevity and metalosis may be time-dependent, such that borderline levels may result in cumulative tissue damage down the road. Given all that, I am still a believer. I scoff at the research comparing THR and resurfacing with respect to hop, skipping, and jumping. I want studies to show me comparing running, skiing, mountain biking, and, most importantly, high impact against the ground, FALLING!

Of note, my understanding of the ASR cup was that it was designed as less than hemispherical to reduce impingement. A good theory that unfortunately was not adequately tested. This resulted in poor tolerance to less than perfect placement. alan

Posted on December 02, 2010

As a patient of ASR MOM hip implants (bilateral) I would have to agree with Dr. Tower. My cobalt level currently stands at 100.3. I’ve been suffering from pain, headaches, vision problems, loss of taste, nausea, gastrointestinal upsets, popping and grinding in my right hip, and now my memory is failing me. My boss has noted that my memory has declined significantly and is affecting my performance at work. Fortunately, he is helping me through this. I will be having my first revision surgery in January and will have the second revision surgery in Spring as soon as I’m recovered from the first one. I will miss a total of 4 months of work as a result of the failed implants and cobalt toxicity. I have done extensive research on metal-on-metal hip implants dating back to the 1960′s showing complications with this technology. Therefore, it should be no surprise to anyone that there is a problem. My own surgeon stopped implanting the metal-on-metal devices in December 09. Unfortunately, it was too late for me. Thank you, Dr. Tower, for your article!

Paul D. Burton, D.O.
Posted on November 20, 2010

Dr. Tower’s article and experience are quite timely for me . Two days ago I performed a revision THR on my patient, a 38 year old female for severe hip pain and cobalt toxicity. She has had seizures, headaches, gross creaking of the hip on examination and a serum cobalt level of 126.8 mcg/L. Her hip replacement was performed for AVN in Feb. 2008 and was a Biomet Taper lock stem, 50 x 56mm MOM implant. She has no other reason for cobalt toxicity other than the THR. The cup was implanted in an over anteverted position (approximately 45 degrees) but her physical findings were severe creaking and crepitant sensation with any hip motion.

I am planning on submitting this case as a case report as I am not aware of this occurring with this prosthesis.

Paul D. Burton, D.O.

Saturday, November 20, 2010

eugene elia m.d.
Posted on October 31, 2010

who’s to blame for the resurgence of MOM bearings? the manufacturer who has financial incentive for higher number use or the surgeon who has continued or increased his use despite the obvious warning signs of cobalt toxicity in the literature. surgeons in many instances have been paid well by their companies to use their products no matter what the bearing is. companies have increased direct to direct advertising to the consumer without accountability. ie the 30 yr. total knee replacement. until our acadamy makes a strong stand on this issue with strict guidelines (not the soft guidelines recently published) this practice will continue until it is obviously too late. (ie no company products will be used who directly advertise to consumers, surgeons will not receive direct compensation from a company unless they actively work for the company or are directly involved in the development of a product etc.)

Stephen S. Tower, M.D.
Posted on October 31, 2010

I appreciate Dr. Jacobs’ thoughtful and timely commentary on my paper. His caution will be appreciated by the arthroprosthetic industry and by surgeons that have implanted, and continue to implant, metal-on-metal bearings. I am concerned that such caution is not in the best interests of about a million patients that have been implanted and those that continue to be implanted with metal-on-metal bearings.

In my case and in the case of my patient I believe that causality is proven rather than suggested. If a child has the classic findings of plumbism, known lead exposure, and elevated levels of lead in the blood, is not causality proven rather than suspected? That I was a subject of my own report suggests that cobaltism is not rare in metal-on-metal implantees. Only after I became aware of my own illness was I able to diagnose it in one of the six patients that I have implanted with metal-on-metal hips: What man knows, he sees (Goethe).

Dr. Jacobs is correct that the present iteration of metal-on-metal bearing was driven by known problems with metal-on-plastic; perhaps it was more driven by marketing. Unfortunately, the present generation of metal-on-metal bearings are underperforming present metal-on-plastic implants in nearly every metric in joint registry data and in well controlled outcome studies reported by economically disinterested investigators. The trend for surgeons to use very large balls is driven by fear rather than by science. The merit of using a bearing of > 36 mm in reducing prosthetic dislocation rates is not proven and it is known that large balls do not reduce dislocation risk if there is prosthetic malposition. That metal-on-metal bearings may on average produce less volumetric debris than metal-on-plastic bearing is inconsequential given that the material is different. Some patients have florid immune reactions to minute amounts of periprosthetic chrome-cobalt. Patients with gross chrome-cobalt metallosis can experience both adverse tissue reactions and cobalt poisoning.

Hip resurfacing appears to be market rather than science driven. The anatomically sized metal-on-metal bearings generally produce twice the periprosthetic debris and systemic metal ion levels as 28 mm bearings and are therefore are at an increased risk for both local and systemic toxicity. The only case controlled study I can find comparing hip resurfacing to total hip arthroplasty found that patients were more likely to prefer the 28 mm hip in the short term, in the resurfacings failed at a much higher rate. Dr. Jacobs is correct that the resurgence of the metal-on-metal bearing has allowed for the resurgence of hip resurfacing. Unfortunately, hip resurfacing has no proven patient benefit and an increased risk of premature revision due to the local and systemic effects of chrome-cobalt metallosis, femoral neck fracture, increased rates of femoral and acetabular loosening, and increased incidence of prosthetic malposition.

I disagree with Dr. Jacobs that either the methodology of measurement of serum cobalt or the level that should merit concern are poorly defined. The levels that represent normal, excessive exposure, and potential toxicity are well documented and referenced in my paper. The levels of cobalt found in myself, my patient, and in the four prior case reports of arthroprosthetic cobaltism dovetail nicely with the levels found in reported cases of alcoholic, iatrogenic, and industrial cobaltism. It is irrational to believe that systemic cobalt generated by a prosthetic hip should be less toxic to the brain, the heart, or the thyroid than cobalt that is ingested and absorbed.

Inductively coupled mass spectrometry was the method used to determine serum cobalt in myself and my patient. The Mayo Clinic reference laboratory made the measurements. Inductively coupled mass spectrometry is more accurate than the graphite furnace method used historically. Either method would have been acceptable given that my cobalt level was 500 times normal and my patient’s level was 100 times normal. I was quite surprised at the magnitude of my first cobalt level and I suspected lab error. At the next draw my long suffering PA served as a control, his levels were not detectable. I also studied matched urine and serum cobalt levels in my case. The relative concentrations of cobalt in serum, urine, joint fluid, and CSF were consistent with available literature of prior cases of arthroprosthetic cobaltism, and from reports of patients requiring revision of hip resurfacing due to metallosis related complications

The radiographs from case 2 were initially submitted but culled in the editorial process. It is notable that cobaltism can occur with well positioned components. It is concerning that cobalt levels 100 times normal are commonly reported in series of hip resurfacing patients that have pain or prosthetic malposition. Cobalt levels of 500 times normal have been reported in renally impaired patients with asymptomatic, well positioned, 28 mm metal-on-metal hips. Many patients that have normal renal function at the time of metal-on-metal hip implantation will develop some degree of renal impairment by the age of 70 years.

The metal-on-metal patient at risk for arthroprosthetic cobaltism is well defined in my paper recently published in Alaska Medicine which is referenced in my JBJS case report. I agree with Dr. Jacobs that we need to target the right population for screening. I now provide my patients with a copy of their implant stickers and a copy their operative report. I no longer implant metal-on-metal bearings due to the increased risks of this technology in the face of no proven benefit.

I am concerned about the possible sub-clinical neurologic and cardiac impairments related to cobalt exposure. Cognitive changes and early cardiomyopathy have been found in workers with lower cobalt levels than asymptomatic metal-on-metal hip implantees.

Arthroprosthetic cobaltism exists, we do not know its prevalence or spectrum, that further study is required is obvious. What non-conflicted party should to do the study? Who should fund it?

I hope that my experience and that of my patient will result in the early diagnosis and treatment of others to prevent an avoidable burden of neurologic and cardiac pathology. I believe that given the safer proven alternatives that all metal-on-metal hip implants should be withdrawn from the market.

Given the information available on cobalt toxicity 40 years ago we should have realized that arthroprosthetic cobaltism was possible, even predictable. That metal-on-metal bearings have become popular represents a triumph of marketing over reason. The present system of arthroprosthetic development, approval, marketing, and regulation bears scrutiny.

Stephen S. Tower, M.D.

Saturday, October 30, 2010

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