• Paul R Kim, Paul E Beaulé, Michael Dunbar, Joshua K L Lee, Nicholas Birkett, Michelle C Turner, Nagarajkumar Yenugadhati, Vic Armstrong, and Daniel Krewski.
• Division of Orthopedics, The Ottawa Hospital-General Campus, Room W1650, 501 Smyth Road, Ottawa, ON K1H 8L6, Canada. pkim@ottawahospital.on.ca
• J Bone Joint Surg Am. 2011 May 1; 93 Suppl 2: 107-17.

BackgroundThe purpose of the present study was to determine cobalt and chromium ion levels in the blood and urine of patients in whom a modern-generation metal-on-metal hip resurfacing device had been implanted.MethodsA total of ninety-seven patients with a Conserve Plus metal-on-metal hip resurfacing implant were followed prospectively for two years. Cobalt and chromium levels in erythrocytes, serum, and urine were measured preoperatively as well as three, six, twelve, and twenty-four months postoperatively.ResultsThe median serum cobalt and chromium ion levels were 1.04 μg/L (range, 0.31 to 7.42 μg/L) and 2.00 μg/L (range, 0.28 to 10.49 μg/L), respectively, at one year after surgery and 1.08 μg/L (range, 0.44 to 7.13 μg/L) and 1.64 μg/L (range, 0.47 to 10.95 μg/L), respectively, at two years after surgery. The corresponding mean levels (and standard deviations) of serum cobalt and chromium were 1.68 ± 1.66 μg/L and 2.70 ± 2.22 μg/L, respectively, at one year after surgery and 1.79 ± 1.66 μg/L and 2.70 ± 2.37 μg/L, respectively, at two years after surgery.ConclusionsThese levels compare favorably with other published ion results for metal-on-metal hip resurfacing and replacement implants. No pseudotumors or other adverse soft-tissue reactions were encountered in our study population. Further research is needed to determine the clinical importance of increased cobalt and chromium ion levels in serum and urine following metal-on-metal hip resurfacing.

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