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Entry into the Medullary Canal

     


- Femoral Exposure:
    - femur is exposed by placing a medium Homan retractor under femoral neck & 2nd under quad. femoris & levering down on fascia lata;
    - leg is held in adduction, flexion and internal rotation such that tibia is vertical;
    - remove any remaining soft tissue from the posterior and lateral aspect of the neck;

- Positioning:
    - place lap sponge into acetabular to collect debris;
    - ensure that femur will not move during reaming;
    - proximal femur is elevated with jaws or hip skid;
    - it is necessary to provide lateral access to femoral canal, because modern femoral stems for cemented use have straight
           or nearly straight lateral borders;

- Back Cut:
    - most femoral components used today have straight lateral stems or relatively straight stems that necessitate a back cut into the
           trochanter, similar to inserting a Moore type prosthesis;
    - to provide straight entry into the femoral canal, any remaining lateral bone on the femoral neck and medial cortex of greater trochanter
           is removed with box osteotome;
    - this can be done with a box osteotome or with a regular chisel;

- Enter IM Canal:
    - enter IM canal first w/ box osteotome to remove meduallary canal first w/ box osteotome to remove base of femoral neck &
           medial aspect of greater trochanter;
    - good exposure to meduallary canal is necessary to prevent under-sizing the component and placing it into varus;
    - a rasp is then used to enlarge the back cut into the trochanter;
    - it is difficult not to overemphasize this back cut;
    - if it is not big enough, then varus insertion will occur;
    - a high speed burr may help with safe enlargement of the hole;
    - w/ rongeur or bonx chisel, remove bone at base of neck at its junction w/ greater trochanter so that stem of femoral component will not be
           placed in varus;
           - femoral component should be placed in slight valgus position;
           - w/ hand reamer aim for medial condyle of femur so component will be in slight valgus w/ 5-15 deg of anteversion;



- Misc:
    - in some cases, a femoral shaft deformity requires a subtrochanteric osteotomy inorder to allow entry of the stem component into the medullary canal