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Acetabular Cup Insertion

(see also: Acetabular Component Menu)

Acetabular Component

press fit components »

  • note whether acetabular component is hemispheric or non-hemispheric;
    • non hemispheric components (ie over sized components or components with a peripheral flare) may be more appropriate for protrusio or for situations where acetabulum will be medialized where as hemisperic components may be more appropriate for shallow or osteoporotic acetabuli;

acetabular liner / femoral head size

over-sizing the acetabular component »

Technical Considerations in Component Insertion

acetabular reaming »

acetabular component position »

  • component is inserted in same direction of reaming;

trial component considerations

  • insert trial component and note the distance between the end of the prosthesis and the bottom of acetabulum;
  • with firm hand pressure usually this distance is about 5-6 mm;
  • note quality of subchondral bone:
    • hard sclertic bone:
      • with hard circumferential subchondral bone only 1 mm oversized component may be sufficient;
      • ensure that the 1 mm undersized component trial can be fully seated (reamer may be used as a trial)
      • consider re-reaming with 1-2 mm undersized reamer to disrupt the circumferential subcondral rim;
      • soft bone:
        • may need to undersize by 2 mm to ensure that the hand pressed trial is about 5-6 mm from the medial edge of the acetabulum (which means that the real component will advance with good peripheral contact);

component insertion

screw placement »

anterior & inferior osteophytes

  • if the acetabulum is retroverted then anterior wall itself will project beyond edges of cup if it is set in anteversion;
  • reflected head of the rectus may be attached to osteophyte;
  • anterio-inferior wall osteophytes must be removed w/ osteotome, cutting along the edge of the cup;
    • failure to heed this may cause posterior dislocation in flexion and internal rotation;

Polyethylene insertion »

References