Wednesday, June 22, 2011

Systemic effects of metal debris (7g of 7); excerpts from the Committee on Mutagenicity

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 (continued from prior posts)

The committee on mutagenicity has reported that internal exposure to orthopedic metals is associated with increased genotoxicity.

This is a series of commentary from the committee on mutangenicity evidence based on the the key journal articles examined by that committee. I think you will find the results really interesting if you are concerned about the systemic effects of the metal.

Third piece of evidence:
J Bone Joint Surg Br. 2005 Oct;87(10):1439-44.

Metal-specific differences in levels of DNA damage caused by synovial fluid recovered at revision arthroplasty.


Bristol Implant Research Centre, Southmead Hospital, Bristol BS10 5NB, UK.


Previous research has shown an increase in chromosomal aberrations in patients with worn implants. The type of aberration depended on the type of metal alloy in the prosthesis. We have investigated the metal-specific difference in the level of DNA damage (DNA stand breaks and alkali labile sites) induced by culturing human fibroblasts in synovial fluid retrieved at revision arthroplasty. All six samples from revision cobalt-chromium metal-on-metal and four of six samples from cobalt-chromium metal-on-polyethylene prostheses caused DNA damage. By contrast, none of six samples from revision stainless-steel metal-on-polyethylene prostheses caused significant damage. Samples of cobalt-chromium alloy left to corrode in phosphate-buffered saline also caused DNA damage and this depended on a synergistic effect between the cobalt and chromium ions. Our results further emphasise that epidemiological studies of orthopaedic implants should take account of the type of metal alloy used.

What did the committee say about this study?
  • They agreed that the assays were done appropriately
  • All 6 samples from the Chromium and Cobalt MoM hip revisions induced a statistically significant increase in DNA damage.
  • None of the samples from stainless steel on PE resulted in DNA damage
  • 4 of the 6 samples of from Co-CR on poly revisions induced statistically significant DNA damage
  • Members agreed that  the data suggested a  plausible hypothesis but no definite conclusions could be drawn
So, now we have 3 studies with two remaining.  In my mind, these studies have raised questions in my mind about the dismissal of the issues surrounding the DNA damage.  It is quite clear to me these these studies clearly conclude, with some rigour, that DNA damage can result from the metal on metal implants.  The question is what is the implication of this with cancer or other systemic issues?  There are some "comments submitted in confidence data which I will review as the final post. 

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