[The betA-angle. a diagnostic sign for the early diagnosis of congenital hip dysplasia (author's transl)].

A new radiographic sign for the diagnosis of congenital hip dysplasia is described. The beta-angle lies between the proximal end of the femur, the medial trochanter and the edge of the acetabulum. Measurements were carried out on 1174 hips and the size of this angle was established. The theoretical transition point between normal and dysplastics is 52 degrees. In reality the transition is smooth, and angles of 50 to 56 degrees are to be regarded as physiological transition values. A vertical position of the acetabulum or lateral position of the end of the femur necessarily results in an increase of beta angle. Values above 56 degrees indicate a definitely abnormal state in a child's hip joint.