Acetabular notch.

Ultrasound images of dysplastic and/or unstable hips often display an indentation or notch at the superolateral part of the acetabulum where the iliac wing joins the acetabular roof. We reviewed the ultrasound and subsequent radiographic examinations of 295 babies examined in our hip screening clinic. Of the hips with a notch demonstrable at the first ultrasound, 97% had a persistent notch at the second ultrasound and in 79% the notch was apparent on the 3-month radiograph. When the notch persists, we believe that it represents damage to the lateral acetabular ring epiphysis and delayed maturation of the lateral acetabulum.