Pregnancy outcome after metal-on metal hip arthroplasty: A case report

Objective: Metal-on-metal hip prostheses are frequently used in young patients, including women of childbearing age. Patients bearing these devices can present elevated chromium and cobalt blood levels . High-doses of these metals during pregnancy can be responsible for reproductive adverse effects, in experimental animals. Few case reports do not suggest an increase of malformative risk (1). Case report: A 36-year old woman had an unilateral metal-on-metal hip arthroplasty performed when she was 23 year old for an avascular necrosis of the femoral head. Radiological tests were carried out once a year. At age 31 the x-ray showed an initial implant wear with metal debris in the periprosthetic tissue. In 2013 she became pregnant and blood cobalt and chromium concentrations were determined for the first time at 31st gestational week. High metal-ion levels were detected both in blood and urine, with 43 mcg/l (normal 0.05-1 mcg/l) and 138 mcg/l (normal 0.1-1.5 mcg/l) for chromium and 55 mcg/l (normal 0.1-0.5 mcg/l) and 304 mcg/l (normal 0.05-0.35 mcg/l) for cobalt, respectively. No systemic symptoms were present, therefore chelating therapy was not indicated. At 39th gestation week, a healthy female infant was delivered by caesarean section and maternal chromium and cobalt levels were 34 mcg/l and 48 mcg/l whereas infant’s levels were 5.3 mcg/l and 26 mcg/l, respectively. Conclusion: Althoug the Expert Advisory Group of the British Committee on the Safety of the Devices recomended that women should be advised to postpone pregnancy at least two years after metal-on-metal hip implantation, in the case here reported, high chromium and cobalt levels were detected far beyond that period. Our case is in agreement with the previously published data that maternal high chromium and cobalt level does not increase the reproductive risk in hip implanted women (2); however, further investigations are requested in order to evaluate offspring physical and mental development. This observation can give a chance to women of childbearing age to plan their pregnancies or to avoid unnecessary pregnancy elective termination.