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Radiographic Findings in SCFE

- Early Stages:
    - widening of epiphyseal line (representing growth plate);

- AP View:
    - normal hip shows epiphysis of femoral head projecting above & lateral to the superior border of the femoral neck;
    - affected hip shows widening and irregularity of growth plate;
    - height of the femoral head above the growth plate appears shortened as compared to the contra-lateral side;
    - Klein's Line:
          - line drawn along superior border of femoral neck should cross atleast a portion of the femoral epiphysis;
          - slip must be suspected if a straight line drawn up lateral surface of femoral neck does not touch the femoral head;

- Lateral View:
    - AP view may not reveal initial slip, which explains need for a true lateral lateral which will detect a posteriorly directed slip;
          - w/ an acute slip, a frog leg lateral may be contra-indicated since it can increase the slip;
          - w/ a chronic slip (or w/ a child who has been walking), a frog leg lateral is acceptable;
    - the most sensitive indicator of a mild slip is the loss of lateral overhang of the femoral epiphysis;
    - Southwick Slip Angle:
          - head-shaft angle of the affected side is subtracted from the head-shaft angle of the normal side;
          - the normal head shaft angle is 12 deg;

- Classification:
    - Grade I: displacement of epiphysis less than 30% of width of femoral neck;
    - Grade II: slip between 30%-60%;
    - Grade III: includes slips of greater than 60% the width of neck;

- Chondrolysis:
    - is seen as a progressive irregularity of subcondral bone & rarefaction of both the acetabulum & femoral head;
    - initial pre-treatment radiographs may show loss of cartilaginous space (as compared to the other side);

- Misc:
    - example of a valgus SCFE