Serum cobalt levels after metal-on-metal total hip arthroplasty.
BACKGROUND
Systemic cobalt dissemination from the Metasul Co-28Cr-6Mo-0.2C metal-on-metal total hip prosthesis has been demonstrated in the first year after implantation. The aim of this prospective study was to monitor the serum cobalt concentrations in patients during the first five years after total hip arthroplasty with a metal-on-metal articulation.


METHODS
A total hip arthroplasty was performed without cement in 100 consecutive patients who had either unilateral osteoarthritis or unilateral osteonecrosis. Fifty patients were randomized to be treated with a metal-on-metal articulation, and fifty patients, with a ceramic-on-polyethylene bearing. The femoral stem was made of a Ti-6Al-7Nb alloy, and the threaded acetabular cup was made of commercially pure titanium. Blood samples were taken before the operation and at multiple time-points for five years after the operation. Serum cobalt concentrations were measured with use of atomic absorption spectrometry.


RESULTS
In the metal-on-metal group, the median serum cobalt concentration was 1 micro g/L at one year after surgery and 0.7 micro g/L at five years. The median of the serum cobalt concentrations measured from three to twelve months did not differ from the median of subsequent measurements, with the numbers available. The median serum cobalt level in the control group of patients treated with the ceramic-on-polyethylene articulation was below the detection limit at all time-points.


CONCLUSIONS
Systemic cobalt release from Metasul metal-on-metal articulations was demonstrated throughout the five-year study period. The median serum cobalt concentrations were found to be slightly above the detection limit and remained in a constant range. The serum cobalt concentrations did not reflect a so-called run-in wear period of the metal-on-metal articulations.
Brodner
Wolfram
W
Department of Orthopaedics, Vienna General Hospital, University of Vienna, Austria. wolfram.brodner@akh-wien.ac.at
Bitzan
Peter
P
Meisinger
Vanee
V
Kaider
Alexandra
A
Gottsauner-Wolf
Florian
F
Kotz
Rainer
R
D000293:Adolescent; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D003035:Cobalt / Q000097:blood*; D005260:Female; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008670:Metals / Q000097:blood*; D015207:Osteoarthritis, Hip / Q000601:surgery*; D010020:Osteonecrosis / Q000601:surgery*; D011446:Prospective Studies; D011475:Prosthesis Failure
D008670:Metals; D003035:Cobalt