Cobalt And Chromium Ion Levels In
Patients With a Metal On Metal Hip Resurfacing
Prosthesis

AAOS San Diego Convention Center, Sails Pavilion
2007
Adult Reconstruction Hip

Michael Dunbar, MD, PhD Halifax NS Canada (a)
G Yves Laflamme, MD ,FRCS Montreal QC Canada (a)
Paul E Beaule, MD Ottawa ON Canada (a,e)
Anna Conway, MSc (n)
Heather Hrushowy, BScN (n)
Paul R Kim, MD Ottawa ON Canada (a,e – Wright Medical
Technology)

Cobalt and chromium ion levels are elevated post
metal-on-metal hip resurfacing arthroplasty. They remain
elevated at 2 years post-op (median serum cobalt 1.6 ug/l
and chromium 3.3 ug/l).

Cobalt and chromium ion levels become elevated following
insertion of a metal on metal hip prosthesis. Few
studies have prospectively assessed ion levels following
hip resurfacing arthroplasty. This study was undertaken
to evaluate cobalt and chromium levels following hip
resurfacing arthroplasty with a contemporary design
implant.

Sixty patients who underwent metal on metal hip
resurfacing arthroplasty were enrolled in a prospective
trial to assess serum, erythrocyte and urine cobalt and
chromium ion levels. Levels were measured
preoperatively, and postoperatively at 3 months, 6
months then yearly. Measurements were performed using a
high resolution ICPMS assay machine.

Preoperatively median cobalt and chromium levels were
within the normal range. At one year, median serum
cobalt levels were 1.1 ug/l and median serum chromium
levels were 1.9 ug/l. The median levels at two years
were 1.6 ug/l for cobalt and 3.3 ug/l for chromium. At
one year, median erythrocyte cobalt levels were 0.8 ug/l
and median erythrocyte chromium levels were 1.2 ug/l.
The median erythrocyte levels at 2 years were 1.1 ug/l
for cobalt and 1.2 ug/l for chromium.

Resurfacing arthroplasty is associated with elevated
cobalt and chromium ion levels. These levels did not
show a significant reduction following the ‘wear in
period’ for metal on metal implants. There is a strong
correlation between serum and erythrocyte cobalt levels
but a poor correlation between serum and erythrocyte
chromium levels. This emphasizes the need for a
standardized method of ion assessment and reporting
following any metal on metal hip arthroplasty.

If noted, the author indicates something of value
received:

a – Research or institutional support
b – Miscellaneous non-income support (e.g., equipment or
services), commercially derived honoraria, or other
non-research related funding (e.g., paid travel)
c – Royalties have been received
d – Stock or stock options held
e – Consultant or employee
n – Nothing of value received

A · to the left of the title indicates the FDA has not
cleared the drug or device for the described purpose.