The clavicle is a sigmoid-shaped long bone with a convex surface along its medial end when observed from cephalad position. It serves as a connection between the axial and appendicular skeleton in conjunction with the scapula, and each of these structures forms the pectoral girdle. Though not as large as other supporting structures in the body, clavicular attachments allow for significant function and range of motion of the upper extremity as well as protection of neurovascular structures posteriorly. Each part of this long bone has a purpose in regards to its attachments that affects the overall physiology of the pectoral girdle.
Medially, the clavicle articulates with the manubrial portion of the sternum, forming the sternoclavicular joint (SC joint). This joint, surrounded by a fibrous capsule, contains an intra-articular disc in between the clavicle and the sternum. Superiorly, the interclavicular ligament connects the ipsilateral and contralateral clavicle, together providing further stability.
Laterally, the clavicle articulates with the acromion, forming the acromioclavicular ligament (AC joint). The surrounding area provides an attachment for the joint capsule of the shoulder. This joint, like the SC joint, is also lined by fibrocartilage and contains an intra-articular disc. The three main ligaments to support this joint are the AC ligament, the coracoclavicular ligament (CC), and the coracoacromial ligament (CA).
The actual shaft of the clavicle is clinically divided into two parts clinically: medial two-thirds and lateral third. These locations are used to properly identify where muscles are attached. The medial two-thirds has an attachment site for the sternocleidomastoid (SCM) muscle and subclavius muscle along the subclavian groove superiorly and inferiorly, respectively. The anterior surface is an attachment for the pectoralis major and the posterior for the sternohyoid muscle. The costal tuberosity, which is where the costoclavicular ligament inserts and supports the SC joint, is also found on the inferior surface. The lateral third of the clavicle serves as attachments for the deltoid and trapezius muscles anteriorly and posteriorly, respectively. Inferiorly the conoid and trapezoid components of the CC ligament provide stability between the clavicle and the coracoid process of the scapula.
The clavicle happens to be one of the most commonly fractured bones in the human body; fracture can be as a result of direct contact or force transmission from falling onto an outstretched hand. Depending on the level of displacement of the fracture, surgery may be indicated, and proper management is determined on an individual basis due to differentiating factors surrounding such injury.