Tuesday, June 14, 2011

Systemic effects of metal debris (7c of 7)

Excerpts and commentary based on the 6/4 post-Metal on Metal Bearings, The Evidence So Far http://www.mydepuyhiprecall.com/2011/06/metal-on-metal-bearings-evidence-so-far.html)

1.  Concern remains about the long-term effect of raised metal ions and systemic dissemination which can be divided into two types of long term systemic effects:  immune mediated and genotoxic.

   Immune Mediated: 

2.   Changes in the lymphocyte  counts have been reported in patients with MoM hip implants.
 [added by Connie:  lymphocytes are responsible for fighting infection or foreign substances that might be harmful to the body.  So at a high level, these lymphocytes are part of the immune system and they remove foreign substances from the blood, organs, tissues and lymph nodes.]
[I am inserting  the full reference (46)  below because I found it fascinating----- A test is available to measure the absolute number of circulating  lymphocytes for MoM patients vs a control group.  So why wouldn't you get this count prior to surgery in order to measure the circulating lymphocytes pre and post surgery.  The person who would order this is an Immunologist.  I never thought about talking to an immunologist.  They can perform tests that are Microbiological cultures, histopathologic examinations, and immunohistochemical analysis.]

J Bone Joint Surg Br. 2009 Jun;91(6):835-42.

Circulating levels of cobalt and chromium from metal-on-metal hip replacement are associated with CD8+ T-cell lymphopenia.

Source: Department of Musculoskeletal Surgery (Charing Cross), Imperial College, London, England. a.hart@imperial.ac.ukErratum in: J Bone Joint Surg Br.2009 Dec;91(12):1641.


We carried out a cross-sectional study with analysis of the demographic, clinical and laboratory characteristics of patients with metal-on-metal hip resurfacing, ceramic-on-ceramic and metal-on-polyethylene hip replacements. Our aim was to evaluate the relationship between metal-on-metal replacements, the levels of cobalt and chromium ions in whole blood and the absolute numbers of circulating lymphocytes. We recruited 164 patients (101 men and 63 women) with hip replacements, 106 with metal-on-metal hips and 58 with non-metal-on-metal hips, aged < 65 years, with a pre-operative diagnosis of osteoarthritis and no pre-existing immunological disorders. Laboratory-defined T-cell lymphopenia was present in 13 patients (15%) (CD8(+) lymphopenia) and 11 patients (13%) (CD3(+) lymphopenia) with unilateral metal-on-metal hips. There were significant differences in the absolute CD8(+) lymphocyte subset counts for the metal-on-metal groups compared with each control group (p-values ranging between 0.024 and 0.046). Statistical modelling with analysis of covariance using age, gender, type of hip replacement, smoking and circulating metal ion levels, showed that circulating levels of metal ions, especially cobalt, explained the variation in absolute lymphocyte counts for almost all lymphocyte subsets.
[ I would suppose  the lymphopenia would subside when the foreign substance is removed however, if the foreign substance has gone to the organs, what would continued exposure result in?  Suppose we have to ask an immunologist]

Lymphocytopenia is diagnosed from the results of a complete blood count. In adults, a lymphocyte level below 1,500 cells/microliter is diagnostic (proof of the condition), and in children, a lymphocyte level below 3,000 cells/microliter is diagnostic.

3.  Reduced peripheral blood counts of T and B lymphocytes were noted.

4.  One possible explanation for the low levels of T cells in the circulation and high numbers in the tissues.

[I don't see the clear relationship here between the systemic effects to the immune system and the T lymphocytes so I will need to look into this further perhaps with an Immunologist.  What are the long term efffects of the metal ion exposure from a immune perspective?   I see the process but I am missing the results from this process.  I will come back to this because all of this only matters if we know what the effect is to the immune system right? ]
The next installment will deal with teh genotoxic effects of systemic exposure to Metal on Metal.

No comments:

Post a Comment