Wednesday, June 15, 2011

Systemic effects of metal debris (7d of 7)

Excerpts and commentary based on the 6/4 post-Metal on Metal Bearings, The Evidence So Far

Genotoxic issues surrounding systemic effects of metal debris

1.  The committee on mutagenicity has reported that internal exposure to orthopedic metals is associated with increased genotoxicity. [but the genotoxicity did not result in cancer in humans...I added this.]

[ added by connie:    Following were the questions put before that committee in July of 06 (footnote 50):

i. Is there convincing evidence that MoM hip replacements can result in increased genotoxicity in patients?
[This question refers to cobalt-chrome hip replacements ie Co-Cr on Co-Cr hip replacements.]
ii. Can any conclusions be made with regard to the chemical(s) responsible, in part, or fully for the observed responses?
iii. Is there convincing evidence that an interaction between Cr and Co may be important in the observed mutagenic responses?

In genetics, a mutagen (Latin, literally origin of change) is a physical or chemical agent that changes the genetic material, usually DNA, of an organism and thus increases the frequency of mutations above the natural background level. As many mutations cause cancer, mutagens are typically also carcinogens

In assessing the studies, members were aware that a typical alloy used for cobalt chromium prostheses would contain 63% cobalt, 26%-30% chromium, 5%-7% molybdenum, 1% nickel, 1%manganese, 1% silicon and small amounts of iron and carbon.  (This is interesting.  I had no idea that there were other metals in that hip besides chromium and cobalt.)

At the end of the day though,  the evidence for the increased genotoxicty observed and the increased blood levels of Cr and Co in patients with Co Cr on Co Cr hip replacements gave rise to concern because this may present a potential risk of cancer in humans.  However, it was not possible to make that conclusion because there was only limited evidence available to suggest a possible interaction between Cr and Co  ions and possible DNA damage in vitro (lab tests) but not in Vivo (humans.)

I will explore each of the key references that were given to support the claim that internal exposure to orthopedic metals is associated with increased genotoxicity but no conclusion between that increase and cancer in humans...yet.  It will be interesting to look at the discussion topics so we can be more informed about this aspect of potential systemic effects of the metal on metal implants.

Stay tuned for the next post.  I think this document is one of the best ones I have come across which
articulates this case for genotoicity albeit, not cancer. 

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