A system for describing positions of the humerus relative to the thorax and its use in the presentation of several functionally important arm positions.

The function of the shoulder is to position the arm with respect to the thorax. Humerothoracic positions are commonly described in terms of the degrees of humeral elevation in the sagittal plane (flexion) and/or the degrees of elevation in the coronal plane (abduction). This article proposes a more general system for describing positions of the arm based on the plane of humeral elevation and the angle of elevation within this plane. This system is used to present the humerothoracic positions used by eight normal subjects to perform several activities of daily living as well as those achieved in a range-of-motion examination of the shoulder. Eating, hair combing, and maximal elevation were all performed in a plane approximately 60° anterior to the coronal plane. Between reaching the perineum and washing the contralateral axilla, the humerus functioned in a range of planes extending over 180°.