The globe system: an unambiguous description of shoulder positions in daily life movements

Positions of the shoulder joint are commonly described in terms of degrees of humeral elevation in the principal planes. This approach is inadequate for an accurate and unambiguous description of functional arm movements that are not confined to these planes. In this paper, a general unambiguous method for describing shoulder positions is adopted and visualized in globe graphs. This facilitates the use and interpretation of the method in clinical practice. To illustrate this globe system of description, a healthy subject participated in the experiments. The shoulder position is described for several functional and standardized tasks for the upper limb with three angles: (1) the angle of the plane of elevation, (2) the angle of elevation within the plane of elevation, and (3) the angle of axial rotation. With these parameters, the position of the upper arm can be visualized as a position on a "globe" about the shoulderjoint. Although not perfect, the globe system provides the most unambiguous description of functional thoraco-humeral positions, which is easy to apply in clinical practice.