The Commission for the Study of Hip Dysplasia (CSHD) of the German Society for Orthopedics and Traumatology developed a grading scheme to describe the relative position of the ossification center for the femoral head to the hip joint.
Anatomic features seen on an AP radiograph:
(1) ossification center of the femoral head (capital) = center of femoral head
(2) Perkin's or Ombredanne's line = a vertical line through the superior acetabular rim
(3) horizontal line through the superior acetabular rim
Location of Ossification Center Relative to the Vertical Line
Location of Ossification Center Relative to the Horizontal Line
Grade
medial
inferior to
1
lateral
inferior to
2
lateral
on or near the horizontal line
3
lateral
above
4
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