The geometry of the humerus and the kinematics of the shoulder and elbow joint can be described by use of appropriate patient-individual
co-ordinate systems.
The humerus co-ordinate system is typically defined from the medial and lateral epycondyles and the center of a sphere that approximates the
humeral head.

The humeral head's joint surface can be described as a semi-sphere, and the proximal humeral shaft axis gives information e.g. for reconstructive
or prosthetic surgery.

These landmarks are determined from bone surface points that are (semi-)automatically delineated in ultrasound volumes.
The animation shows

 - the 2-D image-wise acquisition of the raw gray-scale 3-D ultrasound image     volume,
 - the overlay of the delineated bone surface of the head (yellow), the shaft 
    (light blue), and the ellbow region (purple and white),
 - and the bone surface after processing of the raw gray-scale 3-D volume.

The image acquisition and segmentation procedure allows to determine the humerus co-ordinate system (semi-)automatically:

 - raw gray-scale 3-D ultrasound image volume,
 - delineated bone surface
 - overlay of the humeral head sphere (yellow),
 - overlay of the medial (EM) and lateral (EL) epicondyles (yellow),
 - center of the humeral head (GH), medial (EM) and lateral (EL)
   epicondyles as
 - defining landmarks of a reference plane and the humerus
   co-ordinate system,
 - overlay of the humerus co-ordinate system on the delineated bone surface.

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