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Calcar Pivot

- Discussion:
    - windshield wiper effect (distal toggle);
    - this really only happens w/ non cemented component with large collar;
    - distal portion of the stem loosens and begins to pivot around collar;
    - frequently seen w/ Moore prosthesis that does not fill medullary canal;
    - calcar pivot is caused by medial and lateral toggle of the distal end of the embedded stem;
    - distal stem lacks support, and a subsequent bone reaction results;
    - adequate proximal support of stem or "hang up" medially on cortical rim of femoral neck on which stem and cement pivot produces 
          windshield wiper type of reaction at distal stem with sclerosis & thickening of cortex medially and laterally at the level of the tip of stem