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Femoral Neck Frx: Acceptable Reduction Parameters

- See:
       - x-rays for femoral neck fractures
       - technique of closed reduction

- Acceptable Reduction:
    - poor reduction of femoral neck frx interferes w/ blood supply to femoral head & decreases apposition of bone between bone fragments;
    - reduction should leave neck-shaft angle between 130-150 degrees;
    - radiographic outline of femoral head & neck junction will have convex outline of femoral head meeting concave outline of femoral neck regardless on all views;
           - this outline produces image of S or reversed S curve;
           - hence, if outline reveals an unbroken C curve, then frx is not reduced;
    - posterior comminution: have higher occurance of non-union;
    - garden's alignment index
    - valgus reduction:
           - reduction should leave neck-shaft angle between 130-150 degrees;
           - acceptable reduction may have up to 15 deg of valgus angulation;
           - valgus reduction will increase bony stability, esp in pts w/ posterior comminution;
           - excessive valgus ( > 185 deg - Garden angle ) may increase rate of AVN (due to tethering of lateral epiphyseal vessels);
           - valgus position can be reduced by decreasing traction;
    - varus reduction:
           - results in an increased non-union rate;
           - if reduction is in varus, more traction must be applied, & greater trochanter is pushed medially w/ heel of hand to adduct shaft in relation to head;
                   - this will increase valgus position & impact frx at same time;
           - as noted by Weinrobe, et al (1998), major relative risk of redisplacement of femoral neck fractures correlates with initial inferior fracture offset and varus angulation;
                   - the take home message is that a non anatomic reduction will often lead to postoperative displacement;
                   - similar findings were published by Chua, et al (1998), who noted that varus angulation was the biggest predictor of early fixation failure;
    - angulation: (anteversion)
         - reduction should be between 0 - 15 degrees of anteversion;
         - anterior or posterior angulation of > than 10 degrees should not be accepted, particularly in osteoporotic bone;
    - apex anterior angulation: (retroversion)
         - internal rotation & adduction oppose fracture surfaces & correct apex anterior angulation on lateral view;
         - posterior angulation or retroversion can be corrected by posterior directed force applied to anterior aspect of femoral shaft

Predictors of early failure of fixation in the treatment of displaced subcapital hip fractures.

Predicting the mechanical outcome of femoral neck fractures fixed with cancellous screws: an in vivo study.