About 4% of the newborns in Central Europe suffer from a malformation of their hip joint. An established procedure to diagnose the developmental dysplasia of the hip was inaugurated by Reinhard Graf in the 1980s. It is based on the interpretation of 2-D sonograms.

While the femoral head (2), which is not visible in ultrasound imaging, and the capsule (5) are not used for measurements, the most distal point (arrow) of the pelvic line (1), the acetabulum (3), and the acetabular labrum (4) must be identified to determine the Graf angels alpha (inclination angle) and beta (roof angle).

Since a 2-D ultrasound image visualizes only a plane cut through the joint, it must be regarded to represent the entire spatial joint formation.
Using 3-D ultrasound instead, the entire spatial joint geometry can be visualized. The animation demonstrates the visual enhancement of a raw image volume by the overlay of automatically delineated diagnostically relevant anatomical structures:

 - original gray-scale 3-D ultrasound image volume,
 - overlay of the pelvis (red), acetabulum (blue), acetabular labrum (purple),
   and capsule (green),
 - overlay of the femoral head (yellow), which is invisible in the
   raw image data,
 - the joint after rejection of the original gray-scale 3-D ultrasound
   image volume.

Co-operation: Hannover Medical School, Orthopedic Clinic, Hannover, Germany (Annastift)