Crowe et al reported a classification for developmental dysplasia of the hip.
Data requirements from AP radiograph:
(1) height of the pelvis (vertical distance from the highest point of the iliac crest to the inferior margin of the ischial tuberosity)
(2) medial head-neck junction of the affected hip
(3) inferior margin of the acetabulum (teardrop)
A reference line is drawn that joins the inferior margin of each teardrop. The distance between this line and the medial head-neck junction of the affected hip (proximal dislocation) is then measured.
Parameters:
(1) subluxation in percent
(2) proximal dislocation as percent of pelvic height
Subluxation
Proximal Dislocation
Group
< 50%
< 10%
I
50 to 75%
10 to 15%
II
75 to 100%
15 to 20%
III
> 100%
> 20%
IV
where:
• A subluxation > 100% would be completely away from the acetabulum.
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