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
           



Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Friday, December 9, 2011 11:34 am