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Journal of Bone and Joint Surgery - British Volume, Vol 91-B, Issue 6,
835-842.
doi: 10.1302/0301-620X.91B6.21844 Copyright © 2009 by British Editorial Society of Bone and Joint Surgery Circulating levels of cobalt and chromium from metal-on-metal hip replacement are associated with CD8+ T-cell lymphopeniaA. J. Hart, FRCSG(Orth), Clinical Senior Lecturer & Honorary Consultant Orthopaedic Surgeon1; J. A. Skinner, FRCS(Orth), Consultant Orthopaedic Surgeon2; P. Winship, PhD, Senior Analyst3; N. Faria, PhD, Research Scientist3; E. Kulinskaya, PhD, Director4; D. Webster, MRCP, Consultant in Clinical Immunology5; S. Muirhead-Allwood, FRCS, Consultant Orthopaedic Surgeon2; C. H. Aldam, FRCS, Consultant Orthopaedic Surgeon6; H. Anwar, BMedSci, MRCS, Orthopaedic Specialist Registrar6; and J. J. Powell, PhD, Head of the Micronutrient Status Research Section3
1 Department of Musculoskeletal Surgery (Charing Cross) Correspondence should be sent to Mr A. J. Hart; e-mail: a.hart{at}imperial.ac.uk
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 in13 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.
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