Metal Ion Levels in Maternal and Placental Blood Following Metal-on-Metal Arthroplasty Running Title: Maternal and Placental Metal Ion Levels

Background: There has been a resurgence in the interest and use of metal-on-metal (MOM) bearing surfaces in hip arthroplasty. However, concerns remain regarding elevated metal levels in blood and urine and possible effect on the fetus of a pregnant female with a MOM bearing surface. Purpose: The purpose of this study is to compare metal concentrations in maternal and fetal serum in subjects with MOM hip arthroplasty to subjects without metal-containing implants. Methods: Maternal and umbilical cord blood was obtained from three patients with a MOM hip arthroplasty and seven patients without implants who served as controls. Maternal and placental serum metal levels were tested using inductively-coupled plasma-mass spectrometry. The serum concentrations of titanium, nickel, cobalt, and chromium were measured. Intergroup comparisons were made independent of the means with use of the Wilcoxon-Mann-Whitney test. Correlations were established with use of the Spearman rank-order correlation test. Results: Mothers with implants have statistically significant elevations in serum Cr and Co levels in comparison to control mothers. Babies from mothers with implants have statistically significant elevations in serum Co and Cr levels in comparison to control babies. Conclusions: The Cr and Co serum levels obtained from both mothers with implants and the offspring of mothers with implants are elevated in comparison to the control maternal and