gms | German Medical Science

Objectives: Every metal implant in a biological environment corrodes which leads to the generation of metal ions that can potentially modulate the immune system and cause local as well as systemic adverse reactions. The aim of this study was to investigate the potential influence of elevated blood metal ion levels on lymphocyte and cytokine levels in patients following metal-on-metal total hip arthroplasty at long-term follow-up.

Methods: Lymphocytes (CD8+, CD4+,CD3+, CD14+, CD19+, CD16+/ CD56+, CD25+/CD127-) and specific intracellular cytokines (Interferon-gamma, IL-4, IL-17A) in peripheral blood were assessed using flow cytometry from three different patient groups. The study group (n=38) consisted of patients who had undergone total hip replacement (mean follow-up 15,5 ± 1,4 years) with a small head metal-on-metal bearing and showed elevated serum metal ion concentrations (mean cobalt ion concentrations 2,63 ± 4,36 #g/L). The first control group (n=23) included patients who had also undergone total hip replacement with a metal-on-metal bearing (mean FUP 14,9 ± 1,4 years) and showed normal serum metal ion concentrations (mean cobalt ion concentrations 0,50 ± 0,18 #g/L). The second control group (n=15) consisted of patients who had undergone total hip replacement with a metal-on-polyethylene bearing and showed normal serum metal ion concentrations (mean cobalt ion concentrations 0,20 ± 0,16 #g/L ).

Results: Flow cytometry analysis revealed no significant differences in CD8+ levels among all three patient groups. Furthermore, CD4+,CD3+, CD14+, CD19+, CD16+/ CD56+, CD25+/CD127- Lymphocytes and specific intracellular cytokines, IL-4, IL-17A levels also did not show any statistically significant difference among the three patient groups. However, a weak negative correlation between CD8+ T-Lymphocyte counts and blood cobalt ion levels as well as a weak negative correlation between CD3+ T-Lymphocyte counts and serum titanium ion levels were observed.

Conclusion: Peripheral T-Lymphocytes counts did not show statistically significant differences regardless of implant type or metal ion levels. However, metal ions such as cobalt or titanium may have a general depressive effect on T- lymphocyte levels. More research is needed to evaluate systemic and local lymphocytic reactions in patients after total hip arthroplasty.