Transplacental passage of metal ions in women with hip resurfacing: no teratogenic effects observed.

Over recent years, hip resurfacing has been performed in young, active patients, including women in their child bearing years. Current work investigating the transplacental passage of metal ions (cobalt and chromium) suggests significant passage of ions across the placenta in mothers with metal on metal hip resurfacing. In vitro studies show that cobalt and chromium can create DNA and chromosome damage in human cells. The consequences of this ion transfer on the child during fetal development and thereafter have not been fully quantified. We report on 3 patients with metal on metal hip resurfacings who had the prosthesis in situ during pregnancy. Our data show that umbilical cord blood chromium levels are under a quarter of the maternal serum levels. Cord blood cobalt levels are approximately half that of maternal blood. All 3 children are healthy. Although there was transplacental passage of ions, there was no significant effect on the child in these cases. We did not show any teratogenic effect of metal ions on the child, and this is consistent with the reported literature.

A comparison of Harris and Oxford hip scores for assessing outcome after resurfacing arthroplasty of the hip: can the patient tell us everything we need to know.

We have compared the Harris hip score with the Oxford hip score in a population of 358 patients (213 men and 145 women) aged between 19 to 74 years (median 55 years), after resurfacing arthroplasty of the hip (between September 1995 and October 2006) with a median follow-up of 6 years. The Oxford hip score was related to the age of the patient (Mann-Whitney test; p = 0.015), the hip lifetime (p = 0.030) and body mass index (p < 0.001). Correlation analysis indicated a good correlation between overall Harris and Oxford hip scores (Spearman's rank correlation = -0.70; p < 0.001). An analysis of correlations between individual items in the Oxford score and functional domains of the Harris score showed that the range of movement domain of the latter score was correlated with two items from the former score (-0.40 and -0.38; p < 0.001 and p < 0.001). Based on the correlation analysis, this study provides good evidence that the Oxford score can be substituted for the Harris score for long-term assessment of hip function, without significant loss of information.

Femoral neck fractures after hip resurfacing.

Femoral neck fracture is an important early complication after hip resurfacing. Our aims were firstly to determine the incidence of fracture in an independent series and secondly, in a case control study, to investigate potential risk factors. Fifteen femoral neck fractures occurred in a series of 842 procedures, representing an incidence of 1.8%. No relationship existed between age, sex, and fracture incidence. Mechanical factors such as notching, femoral neck lengthening, and varus alignment of the femoral component were found to have a similar incidence in both fracture and control groups. The proportion of patients that had at least 1 mechanical risk factor was not different between the 2 groups (fracture group, 50%; control group, 41%). Established avascular necrosis of the femoral head was evident in all retrieved femoral heads (n = 9) of patients who sustained postoperative fracture; in none of these patients was avascular necrosis the initial diagnosis. This study suggests that in our practice, mechanical factors, such as neck notching, neck lengthening, or varus angulations, are not the primary cause of femoral neck fractures.