The glenohumeral joint is sometimes referred to as the true shoulder joint, but it is only one of four articulations that constitute what is commonly called the shoulder, shoulder girdle, or shoulder joint complex. The combined and coordinated movements of the glenohumeral, acromioclavicular, and sternoclavicular joints plus the scapulothoracic articulation permit the arm to be positioned in space for efficient use of the hand. Impairment of a single articulation will inhibit normal functioning of the collective. To provide a comprehensive radiographic look at the entire shoulder joint complex, radiographs of the acromioclavicular and scapulothoracic articulations are included herein. Radiographs of the sternoclavicular joints are presented in Chapter 9.
The bones of the shoulder are the proximal humerus, the scapula, and the clavicle. The articulation between the humerus and the scapula is the glenohumeral joint, and the articulation between the scapula and the clavicle is the acromioclavicular joint.
The most proximal part of the humerus is the humeral head, which articulates in the scapular glenoid fossa (Fig. 15-1). The humeral anatomic neck is the slightly constricted region that lies just below the articular cartilage of the head. Inferior to the anatomic neck is the laterally projecting greater tuberosity and the anteriorly projecting lesser tuberosity. The tuberosities are separated by the intertubercular or bicipital groove. The narrowed region distal to the tuberosities is the surgical neck. Below the surgical neck is the humeral shaft.
Osseous anatomy of the shoulder: (A) anterior view; (B) posterior view.
The scapula is a flat, triangular bone with three borders, three angles, two surfaces, and prominent processes. The borders are identified as the medial or vertebral border, the lateral or axillary border, and the superior border. The angles or corners of the triangular scapula are named the superior, inferior, and lateral angles. The superior and inferior angles are at the ends of the medial border. The lateral angle and border give rise to the prominent process of the scapula and thus compose the greatest mass and weight of the scapula. The broadened end of the lateral angle supports the shallow glenoid fossa, which is deepened by the attachment of the fibrocartilaginous glenoid labrum and receives the humeral head. Medial to the glenoid fossa is the coracoid process, which projects laterally and anteriorly.
The body of the scapula is thin and somewhat curved for greater strength. The costal surface of the scapular body lies in close approximation to the thoracic ribs, and this bone–muscle–bone articulation is referred to as the scapulothoracic joint. The costal ...