THE INFLUENCE OF MALPOSITIONING OF THE COMPONENTS

R. De Haan, MD, Resident in Orthopaedic Surgery¹;
P. A. Campbell, PhD, Research Scientist²; E. P.
Su, MD, Orthopaedic Surgeon³; and K. A. De Smet,
MD, Orthopaedic Surgeon⁴

¹ University Hospital
Brussels, Laarbeeklaan 101, 1090 Brussels, Belgium.
² J. Vernon Luck Snr MD, Orthopaedic Research
Centre, Orthopaedic Hospital/University of California Los
Angeles, 2400 South Flower Street, Los Angeles, California
90007, USA.
³ Hospital for Special Surgery, 535 East 70th
Street, New York, New York 10021, USA.
⁴ ANCA Medical Centre, Krijgslaan 181, 9000
Ghent, Belgium.

We have reviewed 42 patients who had revision
of metal-on-metal resurfacing procedures, mostly
because of problems with the acetabular
component. The revisions were carried out a mean
of 26.2 months (1 to 76) after the initial operation and
mostof the patients (30) were female.

Malpositioning of the acetabular component resulted in 27
revisions, mostly because of excessive abduction
(mean 69.9°; 56° to 98°) or insufficient or
excessive anteversion. Seven patients had more
than one reason for revision. The mean increase
in the diameter of the component was 1.8 mm (0 to 4) when
exchangewas needed.

Malpositioning of the components was associated with
metallosis and a high level of serum ions. The
results of revision of the femoral component to a
component with a modular head were excellent, but
four patients had dislocation after revision and four
requireda further revision.