claviklerne

Clavicles, known as clavicles in English and claviklerne in Danish, are slender, paired bones that form the horizontal strut at the top of the chest and constitute the anterior component of the pectoral (shoulder) girdle. Each clavicle extends from the manubrium of the sternum medially to the acromion of the scapula laterally. The bones are S-shaped and mostly subcutaneous, making them comparatively easy to feel under the skin along the upper chest and shoulder.

Anatomy and surfaces

The clavicle has a medial (sternal) end that articulates with the manubrium at the sternoclavicular joint, and a lateral (acromial) end that articulates with the acromion at the acromioclavicular joint. The conformation allows transmission of mechanical loads from the upper limb to the axial skeleton and provides a pivot for shoulder movements. The inferior surface shows attachments for ligaments and muscles, while the superior surface is relatively smooth. The clavicle serves as an anchor for several muscles, including the sternocleidomastoid medially, and the deltoid and pectoralis major laterally.

Function and joints

The clavicles act as a strut that holds the scapula and arm away from the thorax, enabling a wide range of shoulder motion and protecting neurovascular structures beneath the bone. The sternoclavicular joint (the only true articulation between the upper limb and the axial skeleton) is a saddle-type synovial joint with strong ligaments. The acromioclavicular joint is a plane synovial joint joining the clavicle to the scapula. A costoclavicular connection to the first rib via ligaments also contributes to stability.

Clinical relevance

Clavicle fractures are common, especially in sports and falls, with the middle third most frequently affected. Fractures can risk injury to the brachial plexus, subclavian vessels, or the lung apex, leading to pneumothorax or vascular compromise if displaced. Healing is typically straightforward in uncomplicated cases but may require intervention if the fracture is severely displaced or involves the joint surfaces.

Development and variation

The clavicle ossifies primarily intramembranously with two secondary ossification centers appearing late in adolescence at the ends, which fuse later in life. Variations can include accessory clavicles or morphological differences in curvature.