[Accuracy of length and angle measurements in the roentgen image and sonogram of the pediatric hip joint].

The results of measurement of length and angles in the x-ray and ultrasound image of the infantile hip joint are dependent on the different shape of the joint but also on different x-ray projections, on a limited accuracy and incorrect technique in measurement. From our investigations on the accuracy of measurement a differentiation between normal and pathological infantile hip joints is not possible by measuring geometrical data in the x-ray resp. ultrasound image. In the x-ray the greatest possible error of the acetabular angle is +/- 3 degrees, that of the so-called "AMC-angle" +/- 5 degrees and of the Alpha- and Beta-angle in the ultrasound image +/- 10 degrees. Thus the collection of geometrical data in the x-ray and ultrasound image of the infantile hip joint is not more reliable than a qualitative assessment orientated on the osseous resp. cartilaginous corner of the acetabulum.