Clavicle

The clavicle, or collarbone, is an S-shaped long bone that extends horizontally across the upper front of the chest between the sternum and the scapula. Together with the scapula, it forms the pectoral, or shoulder, girdle. The clavicle provides the only direct bony connection between the upper limb and the axial skeleton and helps support the shoulder away from the chest .^1,2

The medial, or sternal, end of the clavicle articulates with the manubrium of the sternum at the sternoclavicular joint. Its lateral, or acromial, end articulates with the acromion of the scapula at the acromioclavicular joint. Between these ends is the curved shaft, whose surfaces provide attachment sites for several muscles and ligaments, including the pectoralis major, deltoid, trapezius, sternocleidomastoid, subclavius, and coracoclavicular ligaments .¹

Mechanically, the clavicle functions partly as a strut between the thorax and scapula. This arrangement helps maintain the position of the scapula while permitting the shoulder girdle to move during elevation and other movements of the arm. The clavicle itself moves at its joints through motions including elevation and depression, protraction and retraction, and axial rotation as the scapula changes position .^1,2

The clavicle should not be confused with the scapula, or shoulder blade. Both belong to the shoulder girdle, but the clavicle is the anterior bone connecting the girdle to the sternum, whereas the scapula lies mainly on the posterior thorax and contains the socket for the head of the humerus .¹