Toward standardized procedures for recording and describing 3-D shoulder movements.

Movements of the human upper extremity are difficult to measure, due to the specific structure of the limb. All arm movements are a combination of movements of the humerus relative to a moveable base: the scapula. Measurement of movements is, however, strongly hampered by the fact that the scapular movement is difficult to track when skin-based landmarks are used. A second complicating factor is the fact that a skin-based proximal landmark on the humerus is difficult to define, which directly affects attempts to describe accurately the movements of that segment. To solve these problems, special measurement procedures have been developed, which include the identification of landmarks for the scapula and the humerus and recording procedures for segment movements or the estimation of landmarks. Also, a definition of the three-dimensional description of motion is presented. These measurement procedures have now been applied in several experiments and have been proven to be successful.