The alpha-angle, which is a measurement of the bony roof of the acetabulum, mainly determines the hip type. Alpha angle > 60 degrees is normal.

Actually, for classification purposes the beta angle is only used to differentiate between type Ia and Ib (both normal hips) and between type IIc and type D)


Up to the age of 3 months (13 weeks) an alpha angle below 60 degrees is acceptable.
A neonate can even start with an alpha angle of 50 degrees provided that the angle gradually reaches the 60 degrees by the age of 12 weeks.

At the age of 3 months the decision has to be made whether the hip is normal or not.

Evidently if a neonate starts with an alpha angle of 60 degrees than everything is o.k. and no follow up is necessary.