The Epidemiology and Demographics of Hip Dysplasia
Figure 1
Ultrasound neonatal hip examination. (a) A representative longitudinal ultrasound image of a normal neonatal hip. The ilium is marked by the asterisk, the bony acetabular roof by the large arrowhead, and the abductor muscles seen by the longitudinal white/gray alternating structures. (b) Measurement of the alpha (α) and beta (β) angles on ultrasound establish the Graf class. The baseline is first drawn and is the line along the ilium as it intersects the bony and cartilaginous portions of the acetabulum (solid black line). The α angle is the angle between the baseline and the roof of the bony acetabulum; the β angle is the angle between the baseline and the cartilaginous roof. (c) An example of a Graf IIc hip, with an α angle of 43° and a β angle of 49°. (d) An example of a Graf IV hip, irreducible dislocated hip, with an α angle of 42°. Typically β angles are not measured on dislocated hips, but in this example it would measure 99°.
