Clavicle

Clavicula

The clavicle is the long, S-shaped collarbone lying across the root of the neck, linking the sternum to the shoulder blade.

At a glance

English: Clavicle
Latin (TA2): Clavicula
System: Bone
Region: Upper limb
Side: Paired, left and right
Muscles on it: Sternocleidomastoid

About the clavicle

Commonly called the collarbone, the clavicle is a thin bone running across the root of the neck, from the top of the sternum out to the point of the shoulder, just above the first rib. It is about 15 cm long and lies almost horizontally, which is unusual for a long bone. Paired with the scapula it forms the pectoral girdle, and it can be seen and felt along its whole length beneath the skin.

Seen from above it has a gentle S-shaped double curve. The inner two-thirds bow forwards and are rounded in section, while the outer third bows backwards and is flattened from above down. The thick medial (sternal) end meets a notch on the manubrium, along with the first costal cartilage, at the sternoclavicular joint. The flat lateral (acromial) end carries a small facet for the acromion at the acromioclavicular joint. Under the lateral part are the conoid tubercle and the trapezoid line, the attachments of the two parts of the coracoclavicular ligament that ties the clavicle down to the coracoid process. The deltoid arises from the front of the lateral third and trapezius inserts on its back edge.

The bone acts as a strut that holds the shoulder out from the chest, giving the arm room to move and letting the scapula slide over the ribs. Shocks from the arm travel along it to the axial skeleton, and it arches over the major nerves and vessels heading for the arm. Its name comes from the Latin for a little key, after the way it turns about its long axis as the arm is raised. In the embryo it starts to ossify before any other bone, mostly by membranous ossification, yet its medial end is among the last growth centres to close, in the early to mid twenties.

The clavicle is one of the most frequently broken bones, usually after a fall onto the shoulder or the outstretched hand. The break typically occurs where the two curves meet, and sternocleidomastoid then pulls the medial fragment upwards. Other problems include separation of the acromioclavicular joint and sternoclavicular dislocation. In cleidocranial dysostosis the clavicles may be partly or wholly missing. The midclavicular line, dropped from the middle of the bone, helps locate the apex beat.

Function and supply

Function: Holds the shoulder away from the trunk and carries load from the arm across to the sternum.
Nerve supply: The supraclavicular nerves cross it superficially and supply the overlying skin; a branch occasionally pierces the bone.
Blood supply: Mainly a nutrient branch of the suprascapular artery, with periosteal twigs from the thoracoacromial artery.

Parts of the clavicle

Each number is marked on the model. Press one, here or on the model, to see it named in place.

Acromial endExtremitas acromialisThe flattened lateral end of the clavicle, wide from front to back. It meets the acromion of the scapula at the acromioclavicular joint, and the joint capsule is fixed to the bone around its margin.
Acromial facetFacies articularis acromialisA small oval joint surface on the tip of the acromial end. It faces the matching facet on the acromion, and together they make the acromioclavicular joint that lets the scapula glide and tilt on the clavicle.
Body of clavicleCorpus claviculaeThe shaft between the two ends, convex forwards in its inner two thirds and concave forwards in its outer third. This double curve is where fractures most often occur after a fall on the shoulder or outstretched hand.
Conoid tubercleTuberculum conoideumA rounded bump under the outer shaft, close to its posterior border. The conoid ligament, the inner portion of the coracoclavicular ligament, is fixed to it and helps to hang the scapula from the clavicle.
Groove for subclavius muscleSulcus musculi subclaviiA shallow furrow running along the middle third of the underside of the shaft. The subclavius muscle lies in it and steadies the clavicle, and it also cushions the subclavian vessels beneath if the bone breaks.
Impression for costoclavicular ligamentImpressio ligamenti costoclavicularisA roughened patch on the underside of the medial end. The costoclavicular ligament, a short strong band, ties the clavicle down to the first rib and its cartilage here, limiting upward movement at the sternoclavicular joint.
Sternal articular surfaceFacies articularis sternalisThe joint surface on the medial end, which faces the manubrium and extends onto the lower aspect where it meets the first costal cartilage. An articular disc separates it from the sternum within the sternoclavicular joint.
Sternal endExtremitas sternalisThe enlarged, roughly four-sided medial end of the clavicle. It sits in a shallow notch at the upper corner of the manubrium, at the sternoclavicular joint, the only bony link between the upper limb and the trunk.
Trapezoid lineLinea trapezoideaA ridge running forwards and outwards from the conoid tubercle beneath the outer third. The trapezoid ligament, the outer portion of the coracoclavicular ligament, attaches along it.
Tuberosity for coracoclavicular ligamentTuberositas ligamenti coracoclavicularisThe roughened area beneath the outer clavicle that includes the conoid tubercle and trapezoid line. The coracoclavicular ligament passes from here down to the coracoid process, and its tearing lets the shoulder drop in a severe acromioclavicular separation.

Anthromica

See the clavicle where it really sits, with every layer of the body around it.

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At a glance

About the clavicle

Function and supply

Related structures

See the clavicle where it really sits, with every layer of the body around it.