This position of neutral scapulohumeral angulation is determined by the angle between a line drawn along the center axis of the scapula and second line drawn at the same level that is perpendicular to the coronal plane (see Fig.
The scapular plane is generally defined as a position of neutral scapulohumeral angulation which optimizes glenohumeral joint congruity and facilitates accurate and consistent evaluation of the joint. However, this method of measurement has recently been called to question since the vertebral level to which one reaches may be influenced by elbow, wrist, and hand motion rather than isolated internal rotation of the humerus. This position maximizes internal rotation and has historically been a standard measure for internal rotation capacity. In this case, the patient will attempt to reach as far up the spinal column as possible while the clinician determines the most superior spinal level that the patient can reach (Fig. Internal rotation can also be measured with the arm in the adducted position. The humerus rotates in the same direction in each case, regardless of the position of the elbow, forearm, or hand. Internal rotation with the arm in a position of 90° of abduction or 90° of flexion uses the same concept. For example, when viewing a right shoulder from the superior to inferior direction, a counterclockwise rotation of the humerus would be referred to as internal rotation (Fig. Internal rotation describes motion around a center of rotation such that the angular motion vector points towards the midline. For this reason, appropriate glenohumeral and scapulothoracic resting positions should be utilized such that accurate assessment can be achieved (the scapular plane and the glenohumeral resting positions are discussed in more detail below). Thus, any evaluation of the capsular structures may produce inaccurate results when the humerus is abducted in the coronal plane.
For example, examination of the patient with straight lateral abduction of the shoulder would place an increased stress on anterior structures relative to posterior structures (Fig.
This slight forward angulation facilitates examination such that surrounding soft tissues are similarly lax on both the anterior and posterior sides of the joint. This position should be differentiated from abduction within the scapular plane which places the humerus in approximately 20–30° of forward angulation, also termed “scaption” (Fig. Abduction of the shoulder occurs when the humerus is elevated in the coronal plane such that the extremity points directly laterally (also known as straight lateral abduction) (Fig.
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