Human Anatomy, Part 1 - K. A. Dyubenko, A. K. Kolomiysev, Yu. B. Chaykovsky 2002

Special Part
Joints of the upper limb, juncturae membri superioris — Joints of the pectoral girdle, juncturae cinguli pectoralis

The sternoclavicular joint, articulatio sternoclavicularis, is formed by the clavicular notch of the Sternum and the sternal end of the clavicle (Fig. 87). Due to the incongruity of the articular surfaces, an articular disc, discus articularis, is located within the joint cavity, dividing it into two compartments. The articulating surfaces are saddle-shaped. Movements in the joint can occur around three axes: sagittal (abduction and adduction), vertical (forward and backward Movements of the clavicle), and frontal (elevation and depression / flexion and extension).

The joint is reinforced by the following ligaments:

- the costoclavicular ligament, lig. costoclaviculare, which extends from the 1st rib to the Inferior surface of the clavicle;

- the anterior and posterior sternoclavicular ligaments, lig. sternoclaviculare anterius et posterius, which pass across the anterior and posterior aspects of the joint;

- the interclavicular ligament, lig. interclaviculare, which connects the sternal ends of both clavicles across the jugular notch.

The acromioclavicular joint, art. acromioclavicularis, is formed by the acromial end of the clavicle and the acromion of the scapula. The articular surfaces are flat in shape. An articular disc, discus articularis, is frequently present within the joint cavity.

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Fig. 87. Sternoclavicular joints, articulationes sternoclaviculares, anterior view (right joint; frontal section)

The joint is secured by the following ligaments:

- the coracoclavicular ligament, lig. coracoclaviculare, which runs from the coracoid process of the scapula to the inferior surface of the clavicle;

- the acromioclavicular ligament, lig. acromioclaviculare, spanning between the clavicle and the acromion.

Movements in the joint occur around three axes, but their range is very limited. On radiographs, the joint space of the acromioclavicular joint is defined by distinct margins of the articulating PARTS OF THE clavicle and scapula, which feature a very thin cortical bone line. The articular end of the clavicle is larger than the corresponding end of the acromion, causing the superior surface of the clavicle to lie higher than that of the acromion. Their inferior surfaces, however, lie on the same level. In cases of subluxation or dislocation, the inferior surfaces of the clavicle and acromion are displaced to different levels, and the distance between the articular ends increases.

The proper (intrinsic) ligaments of the scapula include:

- the coracoacromial ligament, lig. coracoacromiale, a strong triangular band extending from the apex of the acromion to the coracoid process. It protects the shoulder joint from above, forming its protective arch;

- the superior transverse scapular ligament, lig. transversum scapulae superius, which bridges the scapular notch and occasionally ossifies to form a foramen.