Sir,
We read this article with interest.
The strengths of this study are its extraordinarily long follow-up and
the use of
whole blood, rather than serum, for metal ion analysis.1 The latter is
important because red blood cells carry chromium (Cr) ions,2 a point often
overlooked by other studies.
However, we were confused by the level of metal ions detected in this study. In group 5 we would have expected the levels of cobalt (Co) and Cr to increase by similar
proportions,3 when in fact the Co increased 18 times and the Cr increased
by 1.24
times when compared with the well-fixed group 4. Is there an explanation for this, or does it require further investigation?
A. J. HART, MA, FRCS(Orth)
T. W. HESTER, BSc(Hons)
University College London,
London, UK.
1. Case CP, Ellis L, Turner JC, Fairman B. Development of a routine method
for
the determination of trace metals in whole blood by magnetic sector
inductively coupled plasma mass spectrometry with particular relevance to
patients with total hip and knee arthroplasty. Clin Chem 2001;47-2:275-80.
2. Merritt K, Brown SA. Release of hexavalent chromium from corrosion
of
stainless steel and cobalt-chromium alloys. J Biomed Mater Res 1995;29:627-33.
3. Ladon D, Doherty A, Newson R, et al. Changes
in
metal levels and chromosome aberrations in the peripheral blood of
patients
after metal-on-metal hip arthroplasty. J Arthroplasty 2004;19(Suppl):78-83.
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