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Subtrochanteric Fracture Stability

- Discussion:
    - classifaction and fracture stability
    - frx stability is based on presence or absence of posteromedial butress;
    - farther down shaft of femur primary frx is located, greater incidence of delayed union and implant failure;
    - forces acting on hip joint
           - most compression stresses are located 1-3 inches distal to lesser troch;

- Stable Frx:
    - those frx in which it is possible to reestablish bone to bone contact of the medial and post femoral cortex;
    - when not possible: internal fixation device will act as tension band on lateral femoral cortex, & impaction & wt bearing can occur directly thru the medial cortex;

- Unstable Frx:
    - w/ unstable frx, comminution results in loss of medial cortical continuity, and presents a high rate of healing complications and implant failure;
    - medial cortical opposition is not obtained 2nd to comminution &/or fracture obliquity;
           - in this situation, medial cortical support is inadequate;
           - lateral plates or IM devices are subject to bending stress, and loads concentrate in one area of the implant;
           - this results in implant failure or loss of fixation;
    - in frxs distal to lesser troch, stability can be restored by osteotomy or medial displacement, as
    - above all avoid treating unstable fractures like stable ones; (i.e., avoid the following);


- Seinsheimer's IIIA and IV:
     - account for almost all of implant failures and non unions;
     - in both types there is frequent medial cortical comminution that results in lack of stability after internal fixation;
           - farther down femoral shaft frx is located, greater incidence of delayed union and implant failure