Monday, June 13, 2011

Systemic effects of metal debris (7b of 7)

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

1.  The exposure to cobalt and chromium has changed as a result of implant design.

2.  The particles are smaller (nano particles) and more numerous and in some patients, the metal levels may be higher and there may be more corrosion.

3.  Much of our knowledge about the clinical actions of there metals comes from external exposures in industry to the environment.

4.  In contrast, the orthopaedic exposure is internal and hence different in that it bypasses many of the body's natural defenses.

[Added from the footnote-36-:

-  Particles of surgical Chromium and cobalt can be cytoxoix (toxic to the cells which can result in necrosis where they loose the cell membrane and die) or they can be genotoxic (Genotoxic substances are known to be potentially mutagenic or carcinogenic, specifically those capable of causing genetic mutation and of contributing to the development of tumors) in vitro.  In humans, these toxins may be engulfed by a membrane and the debris is  disseminated to local and distant lymph nodes the liver and the spleen.  This is why  there is a concern about systemic effects in the liver and spleen.]

5. Chromium exists in 3 forms (6/3/0).. Cr 6 is a known carcinogen but is not the Cr found in the MoM hips. Cr 3 is less reactive than Cr 6 but  can damage DNA in tissue culture studies.

6.  cobalt compounds cause lung cancer in animals but the epidemiology  in humans is not regarded as conclusive.

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