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August 2008
Antoniou J, Zukor DJ, Mwale F, Minarik W, Petit A, Huk OL.
Lady Davis Institute for Medical Research, SMBD-Jewish General Hospital, 3755,
Chemin de la Côte Ste-Catherine, Montréal, QC H3T 1E2, Canada. janton@orl.mcgill.ca
BACKGROUND: Metal ion toxicity, metal hypersensitivity, and metal
carcinogenicity are causes for concern for patients with metal-on-metal hip
replacements. Thus, understanding the biological fate of metal ions, and
consequently their long-term systemic effects, is of great interest to patients
and surgeons alike.
METHODS: Inductively coupled plasma mass spectrometry was used to measure
the levels of cobalt, chromium, and molybdenum ions in the blood of control
patients (preoperative control pre-resurfacing patients), patients with a
metal-on-polyethylene total hip prosthesis, patients with a metal-on-metal total
hip prosthesis with either a 28 or 36-mm femoral head, and patients with a hip
resurfacing prosthesis. Since cobalt and chromium ions have the potential to
induce oxidative stress through irreversible biochemical damage to
macromolecules, the levels of ions were correlated to the concentration of three
oxidative stress markers in the plasma of these patients. RESULTS: The median
cobalt level was significantly lower (p < 0.001) in the 36-mm metal-on-metal
total hip arthroplasty group (1.8 parts per billion [1.8 microg/L]) compared
with the 28-mm metal-on-metal total hip arthroplasty group (2.5 parts per
billion [2.5 microg/L]) and the hip resurfacing group (2.3 parts per billion
[2.3 microg/L]) at six months postoperatively. The median chromium level was
also significantly lower (p < 0.01) in the 36-mm metal-on-metal total hip
arthroplasty group (0.25 parts per billion [0.25 microg/L]) compared with the
28-mm metal-on-metal total hip arthroplasty group (0.35 parts per billion [0.35
microg/L]) and the hip resurfacing group (0.50 parts per billion [0.50 microg/L])
at six months postoperatively. However, neither the median cobalt levels nor the
median chromium levels were significantly different among the three
metal-on-metal groups at one year. The median levels of molybdenum were not
significantly different among the three groups at either six months or one year.
In addition, there was no significant difference in the plasma concentration of
oxidative stress markers in patients with metal-on-metal bearings compared with
that in control patients.
CONCLUSIONS: The blood metal ion levels in the hip resurfacing group were
similar to those in the 28 and 36-mm-head metal-on-metal total hip arthroplasty
groups. This study suggests that the increased metal ion levels had no effect on
oxidative stress markers in the blood of these patients.
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