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THR: Acetabular Component Biomechanics


- See:
       - operative considerations for hip dyplasia
       - acetabular component revision

- Discussion:
    - restoration of the normal hip center in acetabular reconstruction encourages restoration
           of normal biomechanics; 
    - medial placement:
           - moving hip center medially improves efficiency of hip abductors and will reduce forces
                    acting on the hip in the coronal plane;
           - in osteoarthritis, acetabulum is often overgrown by osteophytes that push femoral head laterally,
                    superiorly, and posteriorly;
                    - in order to re-establish optimal hip mechanics, the hip center must be placed medially,
                             inferiorly, and anteriorly;
           - ref: Benefit of cup medialization in total hip arthroplasty is associated with femoral anatomy.
    - lateral placement:
           - placing the socket laterally creates increased joint reactive forces;
           - lateral placement leads to uncoverage of the superior acetabular cup (or inappropriate abduction of the cup to achieve coverage);
    - anterior placement:
           - this will reduce saggital plane resultant forces about the hip and improves efficiently of the hip extensor muscles;
    - superior placement:
           - placing it directly superior requires the use of a long neck prosthesis to restore abductor moment arm;
           - may slightly improve efficiency of extensor muscles but may have a more significant negative effect on hip abductor muscles 



The definition and measurement of acetabular orientation

Cross-sectional Anatomy of the Ilium: Implications for Acetabular Component Placement in Total Hip Arthroplasty