Abstract
Introduction: Metal-metal (MM) hip resurfacing is being increasingly used in the young. The main concern is the invariable systemic metal ion release. In young women the concern is that metal ions cross the placenta in pregnant women with MM bearing arthroplasties. We earlier presented an interim report on this subject the results of which ate established in a larger cohort
Methods: This is a controlled cross-sectional study of women of child-bearing age with MM resurfacings. (n= 22, mean age: 32 years, mean duration after resurfacing 60.3 months, 3 bilateral). The control group consisted of 24 pregnant subjects who did not have a metallic implant (mean age 31.3 years). Whole blood specimens were obtained from the mothers and umbilical cords at delivery.
Results: None of the babies had a congenital anomaly. Cobalt and chromium were detectable in all specimens including all controls. In the study group, mean cord metal ion levels were significantly lower than the maternal cobalt (p < 0.05) and chromium (p < 0.0001). In the control group, the mean cord blood metal levels differed very little from the maternal levels (p > 0.5). The mean difference in cord chromium between the study (0.33 μg/l) and control groups (0.21 μg/l) was not statistically significant, although the difference in cord cobalt was significant (0.41 μg/l).
Discussion: The differences between maternal and cord metal ions in the control patients is very small indicating that, under these circumstances the placenta allows an almost free passage of metal ions. The relative levels in the study group reveal that the placenta exerts a modulatory effect on metal transfer when maternal levels are above normal. Cobalt and chromium cross the placenta, irrespective of the presence of metal devices and therefore there is a need to continue efforts to reduce metal ion release.
Correspondence should be addressed to BHS c/o BOA, at the Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London, WC2A 3PE, England.
