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.