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Correlation between inclination of the acetabular component and metal ion
levels in metal-on-metal hip resurfacing replacement
Link
http://www.jbjs.org.uk/cgi/content/short/90-B/10/1291
R. De Haan, MD, Resident in Orthopaedic Surgery1; C. Pattyn,
MD, Orthopaedic Surgeon2; H. S. Gill, DPhil, University Lecturer in
Orthopaedic Engineering3; D. W. Murray, MD, FRCS(Orth), Professor of
Orthopaedic Surgery3; P. A. Campbell, PhD, Associate Professor4;
and K. De Smet, MD, Consultant Orthopaedic Surgeon5
1 University Hospital Brussels, Laarbeeklaan 101,
1090 Brussels, Belgium.
2 Ghent University Hospital, De Pintelaan 185, 9000 Ghent, Belgium.
3 Nuffield Department of Orthopaedic Surgery, University of Oxford,
Botnar Research Centre, Nuffield Orthopaedic Centre, Oxford OX3 7LD, UK.
4 J Vernon Luck Orthopaedic Research Center, Orthopaedic
Hospital/UCLA, 2400 S Flower St, Los Angeles, California 90007, USA.
5 ANCA Medical Centre, Krijgslaan 181, 9000 Ghent, Belgium.
We examined the relationships between the serum levels of
chromium and cobalt ions and the inclination angle of the acetabular component and the level of activity in 214 patients implanted
with a metal-on-metal resurfacing hip replacement. Each patient had a
single resurfacing and no other metal in their body. All serum
measurements were performed at a minimum of one year after operation.
The inclination of the acetabular component was considered to be
steep if the abduction angle was greater than 55°.
There were significantly higher levels of metal ions in patients
with steeply-inclined components (p = 0.002 for chromium, p = 0.003
for cobalt), but no correlation was found between the level of
activity and the concentration of metal ions. A highly significant (p
< 0.001) correlation with the arc of cover was found. Arcs of cover
of less than 10 mm were correlated with a greater risk of high
concentrations of serum metal ions. The arc of coverage was also
related to the design of the component and to size as well as to the
abduction angle of the acetabular component. Steeply-inclined
acetabular components, with abduction angles greater than 55°,
combined with a small size of component are likely to give rise to
higher serum levels of cobalt and chromium ions. This is probably due
to a greater risk of edge-loading.
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