Metal on Metal Joints

[Harrison]

This article is focused on artificial hip joints, but I could not help thinking about Medtronic's recent FDA cervical ADR study, which revealed that 4 patients developed cancer (if I recall correctly). Their cervical ADR is metal on metal, might this article relate to these unfortunate outcomes?

Also, good background info:

http://www.medscape.com/viewarticle/489860
Cervical Arthroplasty: Material Properties
Posted 10/04/2004
_____________________________________

Metal-on-metal bearings in old implants may cause chromosomal aberrations

Study results present more questions than answers about long-term exposure to ion debris.
By Dave Levitan
ORTHOPAEDICS TODAY INTERNATIONAL 2006; 9:9

November 2006

BOAChronic exposure to metal ions from early metal-on-metal hip bearings may result in chromosomal aberrations, according to recent findings, but the consequences of these aberrations remain unknown.

“Are these findings of clinical significance? We have absolutely no idea,” said Edward Dunstan, FRCS, of Stanmore, England. “Our patients are otherwise well.”

Dunstan presented results of a long-term study of the effects of metal ion debris in patients with metal-on-metal hip bearings at the British Orthopaedic Association Annual Congress in Glasgow.

Metal-on-metal bearings create more particulate debris than polyethylene, and the particulate is significantly smaller. Dunstan said that electron microscopy has shown metal debris inside the nuclei of certain cells; polyethylene debris “ends up in the cytoplasm.”
Long follow-up

Dunstan and colleagues studied 25 patients who received metal-on-metal hip bearings between 1965 and 1979.

“The average age at time of surgery was incredibly young — only 33 years of age — and the average follow-up is now 35 years” for the survivors, Dunstan said. He noted that while the acetabular cups evolved from uncemented to cemented design during the period of implantation, the bearing articular surfaces and the neck, shaft and stem did not change in terms of materials.

abnormal chromosomes
This image of abnormal chromosomes shows translocation between chromosomes 2 and 15 and aneupoidy loss of chromosomes 9, 16 and 17. This fluorescent in situ hybridization chromosome painting technique shows aberrations in peripheral leucocytes in a male patient with a metal-on-metal implant of 38 years duration.

Image: Dunstan E

Dunstan told Orthopaedics Today, “The bearing articular surface was always a cobalt, chromium, molybdenum alloy. The neck shaft and stem of the prosthesis was always a titanium/titanium alloy.” The Stanmore Metal-on-Metal Proximal Femoral replacement implant was used throughout the study.

The study included three groups: a control group matched for age and sex, patients who retained their original metal-on-metal bearings and patients who originally had metal-on-metal bearings, but received a revision to metal-on-polyethylene. Researchers used the 24-color fluorescent in situ hybridization (FISH) chromosome painting technique on peripheral leucocytes to map changes and aberrations in chromosomes. They examined results from 20 different cells per individual.

The FISH technique allowed researchers to view gain or loss of chromosomes and the more significant structural aberrations, Dunstan said.

“There was a significant difference between the number of structural aberrations between the control group and metal-on-metal group. There was also a significant difference in the number of structural aberrations between the metal-on-metal group and the revised metal-on-metal group. There was no difference between the control group and the revised group.”
Reversible changes

Interestingly, Dunstan said that the chromosomal changes appear to be reversible. The revisions from metal-on-metal to metal-on-poly occurred at an average of 26 years postoperatively, or approximately 10 years from the end of the study. From the time of revision to the present, those patients’ chromosomal aberrations declined.

“It may well be that the normal genetic repair mechanisms are overwhelmed or are themselves damaged by the metal ion load,” Dunstan said.

Because this study focused only on peripheral leucocytes, researchers could not determine the overall effects of metal ion wear.

“Are these changes replicated in other tissues in the body? There is evidence from retrieval analysis that they do occur in bone marrow,” Dunstan said. “What about reproductive cells? We just don’t know. But what is absolutely sure is that we must monitor the long-term biological effects of metal wear debris.”

For more information:

* Dunstan E, Ladon D, Whittingham-Jones P, et al. Chromosomal aberrations in the peripheral blood of patients with metal-on-metal hip bearings. Presented at the British Orthopaedic Association Annual Congress. Sept. 27-29, 2006. Glasgow.

Courtesy Orthosupersite. More data in the original found here:

http://www.orthosupersite.com/defaul...view&rid=19445

[ADR in the USA]

I can't help think about the Maverick lumbar disc due for FDA approval in the summer. It shows very low particulate wear. As for the 35 year follow-up outcomes presented in the article, I would be one happy camper if in 35 years I didn't have cancer of one sort or another. LOL!

[Harrison]

I think the 35 years thing was a misprint...

[Trish]

It is not a misprint.

This looks like the article (abstract only) Dunstan references in his Nov 06 article; however, it mentions a 30 yr follow-up not 35.

Metal ion levels after metal-on-metal proximal femoral replacements - A 30-YEAR FOLLOW-UP

I've recently finished an obsessive amount of research on wear debris, both for metal and poly-whachya-callit-etheline. I am definitely NOT going for a Maverick or any other disc with a metal-on-metal configuration. I am allergic to chrome, cobalt and nickel. Although the studies indicated that skin allergy has no relation to internal or -metal sensitivity- as it is called, I would still like to know. I bet it has some relation. I managed to talk the Norwegian Pro-Disc rep. into a tiny sample that I could tape to myself for a few weeks....LOL [I was sure he'd put out a restraining order on me.] He said sure, he'd send me the same sample he sends to institutions (or somewhere?) for metal content testing.

There is one thing I found everyone "glossing" over (ignoring) in the analysis of polyethylene wear debris. The medical community is unanimous when it says polyethylene is completely inert and it provokes no response from the body...just floats around happily in the cytoplasm . Well, I seem to remember similar assertions about the material used in many breast implants, namely silicon. They thought it would be inert too.

Just a few thoughts for this fine Thursday morning...

Sincerely Your-Bringer-of-Cheer-and-Optimism,
Trish

[Trish]

Sorry. Evidently I'm too old to figure that url link thing out.

http://www.jbjs.org.uk/cgi/content/abstract/87-B/5/628?...urcetype=HWCIT[/url]

[annapurna]

Originally posted by Trish:
There is one thing I found everyone "glossing" over (ignoring) in the analysis of polyethylene wear debris.

Polyethylene wear particles are bad actors and can lead to long term bone loss through osteolysis. You don't hear of it with ADR because they've not found the wear particles in situ or in test. Polyethylene hips and knees are a different story, however. On the good side, I've not hear of the poly becoming chemically active like the silicone did. Generally speaking, poly rots out the bone it falls near and is perfectly happy to remain inert while doing so.

[sahuaro]

Annapurna:
Any thoughts on why no evidence of poly particles with ADR as opposed to hips and knees, e.g., does it have to do with the design of the device?
Just want to add that I so appreciate your sage posts.

[Justin]

This discussion should be helpful in regard to ADR specifically: Previous Wear Debris Article and Discussion

Justin

[Alastair]

We all quite rightly look for perfection for ourselves, and our treatment- - - - -unfortunately it does not exist, but we get the "Nearest thing we can"
Best
Alastair

[fl man]

I think the wear debris would be much less than the knee and hip replacements. The knee and hip replacements are a poor comparison with the lumbar disc. The loads, stresses and types of movements that those joints are required to tolerate are so much more than a lumdar disc.

The Charite's movement is a compression and tilt around a small center spot. Not a sliding and grinding with almost 180' of movement.

I could see the Prosdisc having a slightly higher chance then the Charite for wear. I say this because it functions more like these other joints as a ball and socket, but its rotation is much less. 3'-6'.

Pat