Clavicles

The clavicle, or collarbone, is a slender, S-shaped long bone that links the upper limb to the axial skeleton. It sits horizontally across the top of the thorax, extending from the sternum medially to the scapula laterally, and helps suspend the limb away from the trunk to provide a wide range of shoulder movement.

Anatomically, the clavicle has two ends and a shaft. The medial, or sternal, end articulates with the manubrium at the sternoclavicular joint, while the lateral, or acromial, end articulates with the acromion at the acromioclavicular joint. The inferior surface hosts landmarks for ligament attachments, including the conoid tubercle and the trapezoid line for the coracoclavicular ligaments, and a costoclavicular impression for the costoclavicular ligament. A groove on the inferior surface accommodates the subclavian vessels and the brachial plexus. The superior surface is smooth, while the inferior surface is rough due to muscle and ligament attachments. The clavicle also serves as a conduit for neurovascular structures traveling from the thorax to the upper limb.

Developmentally, the clavicle ossifies primarily by intramembranous ossification with a primary center in the shaft and two secondary centers near the ends, which fuse in late adolescence or early adulthood. This pattern makes the clavicle the first bone to begin ossification in the fetus and among the last to finish.

Functionally, the clavicle acts as a strut that holds the scapula in place, transmitting forces from the arm to the axial skeleton and allowing a wide range of shoulder motions. Clinically, it is a common fracture site, especially in the midshaft, and fractures may risk injury to adjacent vessels or the brachial plexus; treatment varies from conservative immobilization to surgical fixation depending on age and fracture pattern.