Sunday, June 12, 2011

Systemic effects of metal debris (7a of 7)

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

1.  Following metal on metal hip replacement the concentration of metal ions in the blood increases and long term studies  have shown that these elevated levels persist throughout the period of implantation and become grossly elevated when the implant becomes loose.

 [added by Connie/I looked at the references for this statement because it was clearly not my understanding that the only cause for the high levels is loosening of implant however, I found this quote from the study reference: 

The whole blood and urine levels of Co were grossly elevated, by a factor of 50 and 300 times respectively in patients with loose metal-on-metal articulations when compared with the control group. Stable metal-on-metal articulations showed much lower levels. Elevated levels of whole blood or urinary Co may be useful in identifying metal-on-metal articulations which are loose. (reference 34 in this study.)  If this is correct, patients who have grossly elevated Cr and Co levels who are asymptomatic should assume that there is loosening of the implant? ]

2.  The systemic dissemination of metal particles to solid organs has also been shown. (accumulation of these particles in both the liver and spleen have been demonstrated in the reference article, 36.)

[Fretting at ancillary fixation devices, loose components, and modular connections can generate a substantial volume of debris. These particles are in addition to those generated at the bearing surfaces, further increasing both the local and systemic particulate burdens. While all components can be associated with the distant spread of particles and metal ions, it is the environment of revision arthroplasty that provides the greatest potential for the generation and systemic dissemination of wear debris. The long-term effects of accumulated wear particles in the liver and spleen are unknown.  .....So does this mean that post revision,  while the blood levels of the metals are expected to fall, the metal particles in the organs are likey to rise?  Unfortunately, I can't find anyone to answer these questions.]

 [Ok, so if you look at reference 36 from the original journal article, I can see 3things:
  • loosening of the component is only one of the causes of high ion levels but not the ONLY cause
  • It is not the components themselves that are associated with the distant spread of particles and ions but rather THE REVISION SURGERY THAT PROVIDES THE GREATEST POTENTIAL FOR THE GENERATION AND SYSTEMIC DISSEMINATION OF WEAR DEBRIS. I have blogged on this before.  I bet most patients have not been told this likely because no one seems to know how to measure the levels systemically in the organs.  This is why I think it is important to have some kind of systemic measurement of particles in the organs prior to surgery.
  • The long term effects of wear particles accumulated in the liver and spleen are unknown (I have blogged on this before as well.)]
Before I proceed, think about the implications of this. 10 professionals publish this document in May of 2011 (The evidence so far.)  When you get to the systemic review section, only 3 other seminal journal articles  worth referencing on this topic:  one published in 1996, one in 2004 and one in 2005.   It appears the literature has now moved on to the immune mediated and genotoxic systemic effects.  There are 30 references in the next section which I need to review so as I review them, I will comment on them.  This section of the document is worth spending more time on so I will look at this section in 3-5 installments or so.  Completed now: installment 7a. 

Sorry to draw this out but reviewing this section necessitates looking at all of the source documents.  As you know, I think the systemic issues are the most important and least studied of this metal on metal question.

Disclaimer:  Need to again remind the readers of this blog that I am not a doctor, not medically trained and have no real background in this subject matter other than approaching something from  common sense and logic.  You should always consult with your surgeon about this subject matter. I can only give you ideas to discuss with them. I am merely a patient trying to make some sense out of this material.


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