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SCFE: Screw Placement

- Discussion:
    - incorrect placement of pins is a common error;
    - superior quadrant of femoral head should be avoided:
         - this is where retinacular vessels enter, and pin penetration into this area may cause AVN;
         - pins should not be placed superiorly inorder to avoid wt bearing area of femoral head;
    - pins should enter anterior aspect of extra-synovial base of femoral neck;
    - if pins are placed too posteriorly, they may exit thru lateral femoral neck reenter the head, disrupting vessels along neck;
         - from anterior entry point, pins are directed posteromedially to engage epiphysis of femoral head;
         - in grade III slip, epiphysis & metaphysis overlap only 25% of width of femoral neck, making accurate pin placement difficult;
    - pin penetration:
         - pin penetration may cause chondrolysis;
         - two x-rays taken at 90 degrees don't necessarily r/o penetration, however, addition of oblique views should rule out penetration

- AP and Lateral Views of Screw Placement:

    - type of screw:
         - Biomechanical Comparison of Fully and Partially Threaded Screws for Fixation of Slipped Capital Femoral Epiphysis
         - Biomechanical Study of 16-mm Threaded, 32-mm Threaded, and Fully Threaded SCFE Screw Fixation 
    - number of screws:
         - references:
               - Slip progression after in situ single screw fixation for stable slipped capital femoral epiphysis.
               - In situ pinning on slipped femoral capital epipyhysis with a single cannulated screw.
               - Biomechanical stability of single-screw versus two-screw fixation of an unstable slipped capital femoral epiphysis model: effect of screw position in the femoral neck.
               - Biomechanical Testing of Unstable Slipped Capital Femoral Epiphysis Screw Fixation: Worth the Risk of a Second Screw?

The place of threaded pin fixation in the treatment of slipped upper femoral epiphysis.

Unrecognized pin penetration in slipped capital femoral epiphysis.

Progression of a slipped captial femoral epiphysis after fixation with a single cannulated screw. A case report

Screw Placement After Pinning of Slipped Capital Femoral Epiphysis: A Postoperative CT Scan Study