PMC6378482_01
AP pelvic pre-operative radiograph. Polyethylene wear and asymmetrical positioning of the femoral head are visible in the left hip.
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Radiographs were obtained and revealed severe polyethylene wear and asymmetry in the left hip (Figure 1).
Anteversion was measured intraoperatively using navigation and found to be more retroverted than indicated on pre-operative radiographs (5  vs 18 ), leading to revision of the cup component.
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Furthermore, intraoperative measurement with the navigation system indicated anteversion of 5  (radiographic definition), revealing a cup component significantly more retroverted than the 18  indicated by the pre-operative radiograph (Figure 2).
Post-operative radiograph shows the revised left hip with new acetabular cup component and liner with improved joint articulation.
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A decision was made to exchange both the liner and the cup component (Figure 3).