Researchers set safe upper limit metal ion levels for metal-on-metal hip resurfacings
Orthopedics Today, July 2012

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An award-winning study by researchers from Belgium identified safe upper
limits of 4.6 µg/L for chromium and 4.0 µg/L for cobalt in unilateral
metal-on-metal hip resurfacing arthroplasties and 7.4 µg/L for chromium and 5.0
µg/L for cobalt in bilateral procedures.

“Levels higher than [these] established limits were significantly correlated
with clinical symptoms, smaller component size, a smaller coverage arc, smaller
contact patch to rim distance and a higher cup inclination,” Catherine Van Der
Straeten, MD, said. “Females and small head sizes are more at risk of having
problematic hips.”

“These upper acceptable limits are lower than the recommended threshold by the
Medicines and Healthcare Products Regulatory Agency [in the United Kingdom],”
Van Der Straeten said. “But, we had low tolerance for what we call the
clinically problematic hip.”