Abstract
Introduction
Metal-metal surface replacement (MoMSRA) continues to be used in young women. Systemic metal ion release and its effects cause concern. Do metal ions crossing the placenta in pregnant women have potential mutagenic effects? The hypothesis is that metal ions pass freely through the placenta and there is no difference in maternal and cord metal levels.
Methods
This is a controlled cross-sectional study of women with MoMSRA. (n = 25, 3 bilateral, mean age 32 years, time from implantation to delivery 60 months). The control group consisted of 24 subjects, mean age 31 years, with no metallic implant and not receiving cobalt/chromium supplements. No patient was known to have renal failure. Whole blood specimens were obtained before delivery and before any infusion or transfusion, and cord blood specimens immediately after delivery.
Results
Cobalt and chromium were detectable in all specimens in both cohorts. In the control group, the difference between maternal and cord levels was only 5 to 7% indicating free passage. Study group cord cobalt (0.88 mg/L) and chromium levels (0.34 mg/L) were significantly lower than maternal cobalt (1.57 mg/L, p < 0.05) and chromium Levels (1.43 mg/L, p 0.05). However there is a significant difference between the cord cobalt levels in the study (0.88 mg/L) and control (0.41 mg/L, p < 0.05) groups.
Discussion and Conclusion
The limitation of this study is that none of the patients in the study had the excessive metal ion levels recorded in recent times in some of the withdrawn resurfacing arthroplasties. The differences between maternal and cord metal ions in the controls indicate that normally the placenta allows an almost free passage of metal ions. Within the range of levels studied, the relative levels of metal ions in the maternal and cord blood in the study group reveal that the placenta exerts a regulatory influence on metal ion transfer.
